'S'-Pipe upgrade to complement my new header
 

Probably a controversial move since it isn't cheap and I'm not certain what the value will turn out to be, but I'm curious having just installed a header. I already have a 2.5" cat-back exhaust, so I wanted to replace the OE 'S'-Pipe (2-1/4" entry half and 2" exit half) with a 2.5". I did some hunting, got pretty much nowhere, and decided to order a Weapon-R. So, now I'm waiting for it to arrive -- hopefully by Tuesday.

In the meantime, I might as well prepare for it. First, I wanted to evaluate constrictions in the final exhaust setup. Relative to 2-1/2", there's a very short 2-1/4" header exit plus longer "scuba" (OE resonator/main cat combination) 2-1/4" entry and 1-3/4" exit. I don't think the collector is long enough to have much impact, and the "scuba" exit carries much cooler exhaust gases that require less pipe volume, so I'm really not that concerned about either of those. The worst IMO is the "scuba" entry including the 2-1/2" to 2-1/4" junction, though with the gases already cooling a little, the temporary loss of 1/4" before they diffuse within the "scuba" is probably not as harmful as that abrupt size change. However, that I can do something about -- port the "scuba" entry pipe to smooth the transition. So, I ported the entry out to a smidgen over 2.5" and here are before and after photos.

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Attachment 60856

Not perfect, but hugely better than before and very smooth to the touch (except for a slight dip where the pipe meets the flange). The "scuba" is now back under the car and ready for the new 'S'-Pipe.

You're putting way too much thought into this...lol. There's a lot of theory involved, and if that isn't vague enough, you don't have the means to measure how much your theories are effecting the results (gas getting cool, gas velocity, etc.)

Just relax and enjoy the S-Pipe when you install it.

What can I say, dude? I'm just trying to figure out how to get the most bang for my buck, and the bucks aren't exactly trivial (at least, not to me). Guess my curiosity's to blame, but I find it interesting stuff. It's seeming to me that in the world of exhaust velocity Vs capacity, my best bet is probably focusing on velocity. Cutting OE back pressure may be good for F/I, but not so sure for N/A street. Currently planning to paint the 'S'-Pipe for max exhaust gas temp at the "scuba" -- I see that as a velocity assist :)!. However, can't do anything further 'til the pipe arrives :(!

Nice work Trevor. I'm surprised that there was enough material thickness to allow such enlargement to the scuba entry. While FromtheOld has a good point, I'm often inclined to take the extra time to tweak the little things like this. It may not produce a significant improvement but it's still an improvement. It's an individual decision as to whether the little tweaks are worth the effort or not. The time I spent port matching my manifold and gasket to my turbine housing may have been a waste but I don't regret doing it.

Not to rain on your paint idea but if it's a thermal barrier you want, VHT, Ceramic paint or even Jet-Hot don't do much. You need a thicker ceramic coating or better yet, thermal wrap. Hi-temp paint is just for appearance.

Yeah I understand. I used to be similar to you in the sense that I would tirelessly research every little thing I could to get the most out of things, but I've been way busier with life in general so I don't really have time to think about stuff like that. By the way, the whole backpressure thing is a whole myth. Backpressure is NEVER needed....exhaust gas velocity is needed. When using a smaller diameter pipe, people would notice better low-end torque and would assume it was cause of backpressure, but in reality, it was cause the exhaust velocity was increased. I used to be a hardcore N/A guy interested in getting the most out of it, but in the end, I just ended up dealing with turbo stuff cause making power on a turbo car is way easier. Anyways, I just recommended you go with the "standard" for N/A so you don't stress yourself out too much.

Yeah, like I said above, it's up to you if you want to do the little modifications for improvement.

Also, about the thermal barrier, you need high temperature Ceramic Coating to act as a good thermal barrier. Ceramic coating retains heat as long as the temperature doesn't exceed the Ceramic Coating's rating. Most people think 1300 deg sufficient enough for exhaust headers, but I prefer 2000 deg coating for exhaust headers. Having a higher temperature rating also prevents flaking, which is another common complaint. The thing is though, the parts after the exhaust get significantly cooler so coating 2000 deg isn't really needed, but underneath the car is a pretty harsh environment. As durable as ceramic coating is, it won't last underneath a car.

So all-in-all... for thermal barriers underneath your car, you'll need heat wrap.

The whole back pressure thing is interesting in that given ECU AFR control, increasing it is necessarily counterproductive (reduces torque due to less charge in the cylinder), but how much leeway is there in decreasing it given the valve timing is tuned with the OE exhaust? If scavenging increases much, raw charge will begin to flow directly into the exhaust during valve overlap, and even though the engine is VVT-I, I don't see how it would recognize that situation and adjust intake valve timing to correct it. Do you just increase velocity until the mpg drops and then back up?

Seems like most people are going for more peak power and that translates into fatter pipes, less velocity at a given rpm, and hence less lower to mid range torque. By bumping the 'S'-Pipe a little, I'm actually reducing post header velocity proportionally to the increased pipe cross-section. I see ceramic and silica based paint on the header and 'S'-Pipe as a way of countering that change as well as reducing heat radiation. As additional benefits, it delivers higher exhaust temperatures sooner to the "scuba" catalyst and lessens heating of the engine and chassis underside.

Guess I'm not that concerned with achieving a heat block, just a reduction in pipe losses. Painting the header provides a tangible reduction in under hood temp compared to unpainted. That's the kind of change I have in mind. However, if it really would make a significant difference to wrap the 'S'-Pipe, I could take that route instead. Since the pipe is stainless steel, perhaps moisture trapping in the wrap wouldn't be an issue? Could wrap the entry pipe to the "scuba" as well -- though that's not SS and so is probably a bad idea.

Weapon-R says the S-Pipe is 304 stainless steel, so oxidation won't be a problem. The scuba is also stainless steel, but the grade is 409 (and not 304). 409 stainless steel forms a layer of oxidation on the outside to protect it from further rust. It's ugly as hell, but it'll get the job done and it saves OEMs money by using this grade of steel. Obviously this layer is not perfect and the whole thing will rust through EVENTUALLY, but it lasts a lot longer than standard mild steel. (Estimated 5-10 years.)

I'll answer the rest of your post, but I'm off to work now.

Fortunately, I only had to gain about 1/4", but the flange isn't super thick and I was afraid of weakening both it and the pipe in the vicinity of the weld. I ground it as far as felt safe and perhaps could have removed more, but the weld doesn't extend very far up the flange or down the pipe. If that flange were to break, it would be a major drag :(!

I switched from the Dremel to a drill with a cylindrical grinder bit and that was very effective -- it's a pretty large grind area. Finished off with 220 and then 400 grit paper. It's about a 45 degree angle at the outermost and pretty smoothly transitions to the inner pipe. Took me quite awhile, but should definitely help reduce turbulence.

Decided to go with this, though it'll add a few more days to the project :(.

http://www.amazon.com/gp/product/B00...=ATVPDKIKX0DER

If you want to trap heat in the s-pipe, that's the stuff to do it. It's a lot more effective than ceramic coatings and hi-temp paint has no value whatsoever as a thermal barrier. You should also wrap the header.

Problem with wrapping the header is I don't know whether the stainless is impervious to corrosion -- hard to imagine the manufacturer reached for the best quality. From what I've read in the past, the ceramic and silica suspension paints do reduce radiated heat, though no doubt the wrap is easily more effective. I'm more concerned as to whether I'll be able to bolt the different styled Weapon-R flange to the threadless header. Considering getting Helicoils and installing them in the lower flange.

Thinking of porting -- it's value is a function of flow. Low velocity generates little turbulence whereas high velocity can generate plenty, just depends on the severity of the obstruction. It's fluid mechanics and porting makes a difference whenever flow velocity matters. Your TB port opens the bore sooner resulting in a larger than OE gap between the throttle plate edge and bore, and it also reduces turbulence on both sides of the plate allowing greater max flow. Both effects boost throttle sensitivity. I've seen comparisons in the past of ported Vs non-ported and the difference can be very tangible -- true, it's not going to make the difference between a "slow" car and a "fast" car, but it can make a difference on how fast is "fast".

PS. Decided to go for the Helicoils, they and the wrap will probably arrive around the same time.

Although I believe that thermal wrap is by far the most effective means of trapping heat in the exhaust gasses and reducing unwanted radiant heat, I also believe that ceramic coating is a much better solution for street cars. Ceramic coating may not be as effective as wrap as a thermal barrier but it also protects the header or pipes and looks better. Personally I'd use wrap on a race car and ceramic coated or even just marginally effective ceramic paint for a street car. FWIW a buddy of mine wrapped the SS header on his VW and the header rusted through in under 5 years of minimal use.

I agree with what you said about porting. It's long been the little things that separate 1st and 2nd place in all forms of racing. However it's also true that unless you've already optimized the bigger things, little tweaks like porting won't make up the difference. For instance, another XB with the same exhaust as you will probably still make more power if he replaced the scuba and mid-pipe and didn't bother port matching anything.

I'm not so sure about heli-coils for that app. I might be wrong but I believe they are designed to bottom out in blind holes. Maybe you could find longer shoulder bolts with the same length shoulder instead?

Depends on one's vehicle goals -- currently, mine include keeping the "scuba". I've done plenty of porting on the Eclipse, but if I was really intent on power, there are plenty of much bigger parts changes that could be made -- no thanks! Better flow behavior means the engine doesn't have to work as hard doing its air pump thing -- that translates into MPG and I'm an automatic fan of that :)!

Don't know how the Helicoils will work out, but I don't see an inherent problem. The 10mm length stainless coils fit entirely within the flange, I already have the appropriate tap to seat them, and I believe the existing flange holes are OK as is. It's a pretty cheap experiment (<$10) and the worst that can happen is a bolt somehow bolloxing one while threading in. If that's a problem, I'll just have to stick to nuts -- guess I'll find out!

The Weapon-R 'S'-Pipe arrived today (packaging was excellent) and I'm told the wrap and Helicoils were both shipped. So, here's a photo of what I received and the other items will probably arrive by Thursday. Weapon-R included a 2.5" donut gasket, a set of bolts with washers and nuts for the "scuba" end, and a set of bolts, washers, springs, and nuts for the header end. Don't yet know exactly what I'll use for the 'S'-Pipe to header spring bolts, but it's nice to have options :)!

Attachment 60391

I see nothing wrong with keeping the scuba other than sacrificing a few ponies up top. On the plus side you're keeping a cat and the scuba does a great job of reducing header rasp and in-cabin resonance. I forgot what you're running for a mid-pipe. Is it the 1.75" oem or something else?

I guess the heli-coils might work but since they thread in and there will be nothing to bottom out on, I'm afraid they may turn in their threads as you tighten the spring bolts. Perhaps Loc-Tite red on the heli-coils might help prevent this? Or else you could not tap the flange all the way through leaving a taper for the coil to seat against.

The W-R s-pipe looks great and I hope it fits as good as it looks.

I've a Tsudo dual which is a "scuba"-back with 2.5" piping. HP isn't that big a thing to me since I don't drive fast and I don't race. I'm more interested in torque and I don't think keeping the "scuba" hurts that -- my concern is more flow velocity than flow volume.

Helicoils aren't normally installed at the bottom of a drill hole, usually they're just a little below the surface (at least, that's the manufacturer's instruction with the previous ones I purchased) and they can definitely be torqued against, so I really don't see a problem with flange install. Of course, these holes are pre-drilled and may not be sized optimally for the helicoil, so I think that's my biggest risk. Still, they're a good fit for the 10MM bolts and the Helicoil requires a 12MMx1.25 tap, so I'm hopeful :)!

Turns out the holes are indeed too small for 12MM Helicoils, so that's good -- I had to drill them out, though I chose a drill 1/64" smaller than standard for the tap (probably 1/32" smaller would have been even better). I'd bought three Helicoils and got one installed perfectly, but had trouble with the second (the pipe bends toward that side). First try I accidentally broke off the tang while positioning it, then I was so busy concentrating on not breaking the tang on my last Helicoil, I accidentally turned it a little too far through and deliberately broke off the tang before realizing it :(! So, I just ordered another set of three and will hopefully get it right this time -- to bad it puts me out to next week.

The wrap should show up tomorrow.

Wrap's arrived and UPS should be delivering the Helicoils at any moment -- talk about speedy :)!

Attachment 60224

After the other Helicoil's finally installed, I'll do a test with the 'S'-Pipe and OE spring bolts to make sure there are no issues. If the Helicoils turn out a problem, I'll just have to use the Weapon-R provided hardware :(.

Helicoils arrived and I made yet a different mistake, but didn't break off the tang and so could re-install and this time was successful. That leaves me with two spares :)! Went to start the 'S'-Pipe wrapping and noticed the inside of the header end weld was very rough and so I cleaned it up with a Dremel stone, sanding drum, and 220 grit sandpaper. The other two weld interiors are probably much the same, but since I can't get to them, it can't be helped. Here's the cleaned up weld interior.

Attachment 60164

'S'-Pipe wrapped! Used 25ft of 2" wrap, got it as tight as I could, and used two 14" ties at each end. Might not look quite professional, but I think it'll do the job.

Attachment 60162
Attachment 60163

Ran into an unexpected snag with the Weapom-R 'S'-Pipe -- the CEL Eliminator wouldn't thread into it. The Eliminator had just come out of the OE 'S'-Pipe with no problems and the threads looked fine (though there was Anti-Seize compound on them). I tried finger turning my 18MMx1.50 tap through the bung and it wouldn't go either. I looked at the threads and saw no obvious problems, just discoloration, but clearly something was wrong -- I'm guessing distortion from the welding. I ran the tap through and it took a fair amount of effort to turn. Afterward, I applied fresh Anti-Seize to the Eliminator and was able to turn it in OK.

Attachment 60135

Ran into a few issues, but it's together, though with at least one exhaust leak -- hoping it's just the "scuba" since I've no gasket for it. I'm not sure yet about the doughnut since it's sized for the Weapon-R collector, and the OE isn't big enough for the 'S'-Pipe and can't be used. I'll find out for sure when the scuba has a gasket.

My first problem was the OE spring bolts aren't long enough to install with the Weapon-R 'S'-Pipe. Simple solution is to use the provided bolts, but they are 10MMX1.50 which doesn't match the 10MMX1.25 OE exhaust manifold and my freshly installed Helicoils. My quick and dirty solution for this was to run a 10MMX1.25 die over the bolts -- however, that's a poor solution and I need to get the right bolts. Which brings up the next complication, the provided bolts are 3.75" and need another 1/4" for comfortable install -- though maybe that's perfect for the Weapon-R header. So, hopefully the last issue is the missing "scuba" gasket. In any case, here are a few photos.

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http://i8.photobucket.com/albums/a33...onRSPipe_9.jpg
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Oh, yeah -- so far, the Helicoils are working great :)!

OK, picked up a 2.5" gasket and the exhaust leak is fixed -- the Weapon-R doughnut gasket appears fine with an OE compatible header. Picked up a couple 100mm (4") bolts and they're fine, but looks like the Weapon-R 3-3/4" bolts would be OK (outside of the thread spec) if washers aren't used at the flange -- looks like a YMMV issue to me. The Helicoil thing is an issue I created myself, but I like the convenience and they're proving themselves reliable through multiple spring bolt tightenings and loosenings. Don't have any driving time to speak of on it yet, but everything is working and tight.

Happened across the OE "scuba" gasket in the driveway, it was broken in half and looking very beat -- I didn't even realize there originally was one! Now I've a new one, it's clear it's been missing ever since I first removed the OE 'S'-Pipe. The OE coupling gives a tighter connection than just bolts and the difference is audible. I'll need some time to conclude whether I've actually gained ground with the 'S'-Pipe change, but I definitely prefer the sound with a gasket at the "scuba" :)!

I'm a little confused about the bolts. The oem bolts are shoulder bolts designed to torque tightly against the header flange while providing the correct spring pre-load to create an air-tight seal between the graphite donut gasket and it's conical mating surface in the S-pipe while still allowing some movement without destroying the donut gasket. In your photo it appears that W-R provided standard bolts with no shoulder for proper seating. How are you supposed to tighten them to the correct spring pre-load and then keep them tight? I suppose you could guesstimate and use loc-tite.

Did you really re-tap 10x1.50 bolts to 10x1.25? If so then you indeed do need new bolts. Bolts with the correct shoulder length, overall length and thread pitch. Good luck with the on-going project.

The OEM spring bolts have a stop that limits how far they can screw into the exhaust manifold. Weapon-R provides flat and split ring washers and I guess you tighten the bolts to whatever degree seems appropriate. However, darned if I know what's optimal with the Weapon-R setup, so I tried to leave "enough" inter-coil space to be functional. That is -- I guessed! Frankly, I wouldn't be the least surprised if less spring tension would be appropriate, but I really don't know how to gauge it :(! The OE setup is easily more repeatable and specific, and that was why I hoped to use the OE spring bolts, but although I tried, it didn't work out :(!

Sure did, I needed to use the car and recutting the bolt threads to get me by for a while seemed entirely reasonable. As it is, the recut threads held securely and given I've really no use for 3-3/4" 10MMX1.50 bolts, I can't say I feel too bad about the transgression :)! Unfortunately, the replacement 10MMX1.25X100 bolts cost me a little over $7 :(! I agree the OE spring bolt arrangement is higher quality and more repeatable, though the Weapon-R replacement is probably serviceable for a' that :)!.

At this point, I'm especially noting the difference made by installation of a new 'S'-Pipe to "scuba" gasket -- a very worthwhile move coming from none :(! I've yet no clear sense whether my 'S'-Pipe "upgrade" really accomplished much, though it's still a little early to tell. I've come to realize the difference in ID between my header collector and the Weapon-R plus the OE 'S'-Pipe and the Weapon-R is only perhaps .2", though it increases to about .7" at the 'S'-Pipe half way point. IMO -- that doesn't really speak for much of a performance boost! My suspicion is the multiple header paint coats and 'S'-Pipe wrap are my best bets for any realized improvement.

Got to see how it goes, I guess, but I'm not yet jumping to recommend the Weapon-R 'S'-Pipe as a performance upgrade for our cars. Interesting to play with though :)!

Thought a lot about the darned spring bolt setup and decided to revisit it. One thing is I believe it's a mistake to install a washer at the flange end of the spring -- the space is too tight and it binds against the bolt, restricting the very motion it's intended to permit. I'm suspecting the only reason Weapon-R includes a washer at each end of the bolt springs is to make sure the spring stays in place before install and I simply erred in installing both. (Plus, 3-3/4" bolts are definitely fine if you don't install washers at the flange.)

In any case, I've dropped back to a single washer per bolt, with the split ring washer between it and the bolt head. I've also switched to the OE springs since the wire gauge appears the same, but the OE are a smidgen longer and have a more open wind. I screwed in both bolts finger tight to start them, and then used a ratchet to add 10 quarter turns of spring tension per bolt. The connection seems stable to me and the OE springs have plenty of remaining travel. If needed, I can easily add matched bolt rotations to increase the spring pressure.

Attachment 60081

With the threaded lower header flange, I'm thinking the combination of split ring, washer, and spring tension provide enough stability that it's not necessary to add Loc-Tite. I suppose I could install jam nuts on the bolt ends, but I don't think they're needed. However, if the bolts were held by nuts instead, then either Loc-Tite or another split ring washer would probably be a good idea to prevent loosening.

Just an observation, the scuba connection to the OE 'S'-Pipe has a very positive pipe alignment because of the bolting arrangement, this is lost with the Weapon-R 'S'-Pipe, so it's necessary to very carefully align the pipes for optimal exhaust gas flow. Also, I think I'm getting spoiled by the OE 1.25 thread pitch -- it makes it easier to get a tight connection, plus it's less likely to loosen than with a 1.50 pitch.

Fired it up, slowly passed my hand around the doughnut coupling, and no sign or sound of any exhaust leaking. Took a look down at the coupling and it appeared to be flexing easily with the engine movement. So, seems to me finger tight plus 2-1/2 bolt rotations works fine with the Weapon-R doughnut and OE springs.

Took it out for awhile and the exhaust rumble seems lower than ever (installing a gasket at the "scuba" helped a lot). I tried giving it throttle up the nearby hill in fourth at about 40 mph and there was actually some push against my back, not lots, but enough to notice. Also, more of the accelerator travel seemed to be useful than before. So, perhaps cylinder scavenging has indeed increased and I'm getting a little more torque -- it always accelerated, but not so that I could feel it at all. So, I'm currently thinking I've gained a little ground, but if so, it sure wasn't cheap and it involved some work.

Since I'm thinking this mod actually accomplished something, I'm looking at extending it a little, but since the viewers of this thread apparently have no particular interest, I guess it's time to take my efforts off line. Cheers :)!

quick question did you have any clearence problems with the o2 sensor? i tried to install my weapons r s pipe this weekend with out the 90 degree cel eliminator and the o2 sensor hit the cv shaft

I'm actually interested. I just come in to read. It's interesting to see other people's results.
I haven't done any type of exhaust work on my xB yet. I have the TRD eBay replica on it's way. I'll have to look at everything more carefully, like you have. I may eventually get the Weapon-R header/s-pipe, but then I'll have to add a catalytic converter. Not a huge deal, but I'm sure I'll need to do a bit more work to tame the exhaust note.

I never tried that since I needed the CEL Eliminator for the header. I can say that with the Eliminator, the Weapon-R allows more open install/removal access to the O2 Sensor than does the OE pipe. If I need to swap the OE manifold back in, I just leave the Eliminator installed, doesn't hurt anything.

Attachment 59966
Attachment 59967

Just like me, you lose the pre-cat when you install a header, but unless you specifically choose to delete the "scuba", you'll still have your main cat.

I know this'll sound crazy, but with the latest mods, my xB2 is reminding me a little of my modded turbo Eclipse (my experience with which factored into these xB2 mods). There's a nice touch of eagerness showing up that requires I ease back on the throttle to behave. In the Eclipse, I interpret it as earlier-than-OE spool that I have to moderate by backing off a little. I've ordered some more wrap for the lower portion of the header (where the four pipes run together) and am hoping it will further the car in that direction. Unfortunately, Amazon seems to be doing their level best to make me wait as long as possible :(! Took me awhile to start experimenting with the pre-"scuba" exhaust, but it's appearing complementary to my smooth bore TBS that preceded it.

Huh? Typo I presume?

Glad to hear that the s-pipe wasn't a waste of money. If you haven't already you should consider a CAI for your next mod. Import Tuner got the biggest hp/tq gains from adding a AEM CAI. More than the Strup header.

BTW, back to the spring bolts... it shouldn't be hard to duplicate the oem desgined spring tension without the proper length shank on the bolts. Just measure the oem compressed spring length and tighten the bolts to the same. It only has to be close. Personally I'd prefer loc-tite to split washers since the bolts will be 'loose' without a shank but it may work just as well with the spring tension and split washers.

Perhaps a mis-communication of some sort? I never had a reason to use the Weapon-R 'S'-Pipe without the CEL Eliminator since my first step was to install a header. As soon as a header replaces the OE exhaust manifold, the Eliminator becomes mandatory. So yes, I meant what I said, no typo.

Frankly, I'm finding that one a little hard to evaluate, though it's probably best to just ignore the cost :). I'm clear I've gained some ground, however, that could be entirely due to being able to wrap the Weapon-R 'S'-Pipe (corrosion safe SS), though the slight dimension increase may also factor in. I'm taking a gamble in wrapping the lower header pipes in that I'm guessing any moisture will be able to escape from within the pipe bundle -- that is, it won't be sealed within the wrap. I think it'll be beneficial since air passing through the radiator normally cools that portion of the header. Wrapping should reduce that cooling.

Actually, I'm happy with my home brew CAI. I like that I have easy access to the high flow air filter and since I'm not pursuing max horsepower, any losses due to the presence of the OE air box (I see Descendent keeps it too) isn't a serious issue to me.

The spring bolt question is interesting. The OE design has the tension on both bolts defined by the built in bolt stops. My approach with the after market 'S'-Pipe is to take up the bolt slack by hand, and then increase the tension by a set number of bolt revolutions. Fact is, the contact area between the Weapon-R 'S'-Pipe bell and doughnut gasket is different from OE -- it's greater. So, the spring tension required could well be different despite using the OE springs. My approach was to go light and see from use if I needed to increase it. So far, the addition of 2-1/2 bolt rotations appears adequate (1.25 pitch), though to be sure, it's possible less would also do the job.

I was tired and skimmed the post to which you were replying. It sounded as though you were saying that you needed the CEL eliminator for the header, as in you installed it there. Clear now.

I'm assuming that the biggest benefit you've felt was the s-pipe and not the wrap. Typically the little things like header wrap don't produce noticeable results although they do add up.

From the test results I've seen high-flow air filters add nothing vs paper unless the filter surface area is under-sized, which is not the case with our engine, IMO. I was referring more to the turbulence and airflow reduction caused by the accordian intake pipe that World Racing eliminates. I doubt the airbox or the paper filter present much restriction.


Whatever works... it's certainly not rocket science. :)

Well, the Weapon-R is officially 2.5", but turns out that's outside dimension, not inside (I was imagining it to be ID). So, the real difference in ID for the first half of the pipe is about .2", and around .5" (EDITED from .7" to .5" on 5/24) for the last half where the OE pipe is smaller. That makes for a very small increase in volume and a very small decrease in flow velocity, which gives me a little more of a pre-"scuba" reservoir effect for power, but works a little against me for scavenging. Looking at the OE pipe, I don't see any serious flow issues in the bends, worst concern being the modest ID reduction at the halfway point, but the reduced Weapon-R resistance should provide some flow velocity increase. What's the net effect? I'll guess some reservoir and near unchanged flow velocity.

On the other hand, the increase in average gas temperature in the pipe should be significant going from bare metal to wrapped. So, I'm inclined to think velocity is having at least as much and likely greater effect here than volume and flow. 'Course, I've no proofs one way or the other -- just me trying to apply theory as best I can :). If I'm wrong, then wrapping the lower portion of the header is going to be pretty much a waste of money and time.

Can't say I know if there's a difference in restriction between the two filters on mine. I know people have claimed to notice a difference with a high flow in the absence of the snorkel, but I never seriously tried to evaluate it myself.

I guess the only way I can find out for certain whether that short length of 3" flex hose is having much impact would be to try something else (the flex hose inner ribs are very shallow). In my case, that would also replace the flexible inlet hose (more shallow ribs). However, max intake airflow is only needed at high rpm. My usage is very much midrange and below -- I never get even remotely near redline. Also, exhaust gas volume is hugely expanded over equivalent intake gas volume, whereas that's a 3" intake Vs 2.5" pre-"scuba" exhaust. I don't know, my logic is telling me I don't stand to gain much, if anything, by upgrading the intake pipes (and recognizing the intake manifold has a decent sized plenum plus there are two resonance chambers that smooth air demand from the piping). I think the gain on that side of the engine with N/A comes from ditching the snorkel and smoothing the constrictions (the TB approaches 2-1/4" at its widest following the plate, is a fair amount less than that at the plate, and I understand the WOT spec is only about 62% open) (EDIT -- My understanding was wrong on this -- Fred is correct with 80% being the spec 5/24). I'm just not seeing the 3" flex piping as a problem.

What I think I am seeing is the problem of getting the exhaust gases out of the cylinders. As I make improvements to the engine's ability to accomplish that, the intake side doesn't appear to have a problem delivering fresh charge -- I run out of throttle response long before I run out of pedal travel (despite the modest throttle plate size and restrictive spec). Sure, there's a computer between them, but I doubt it's leaving that much dead pedal travel in its plate control. I really think my best attack is exhaust velocity, and the lever available to me for that is temperature control.

Theory aside for the moment, here is a dyno sheet comparing the AEM CAI to the stock airbox:

http://www.importtuner.com/powerpage...rs5/index.html


http://image.importtuner.com/f/10569...ntake_dyno.jpg

Dyno 2
AEM Cold-Air Induction System
Peak HP: 134.4 / Peak TQ: 138.6

Horsepower Gain
* 4,000 to 5,500 HP range: 5.5 to 10.8
* 5,500 to redline HP range: 6.9 to 12.0

Torque Gain
* 4,000 to 5,500 TQ range: 4.3 to 14.8
* 5,500 to redline TQ range: 5.7 to 11.2

So much for the resonance chambers or should I say intake sound dampers? Also where did you hear that the "WOT spec" is only 62%? I've never seen or heard anything like that.



From the Scion TC performance parts testing roundup:

https://www.scionlife.com/forums/viewtopic.php?t=92108

"Second up Stock Air Box with Drop In K&N filter. We left the charcoal thing in as well
This one was an absolute bummer IMO. It lost HP but the air fuel was good."

Now I don't believe that the drop-in K&N actually lost hp or tq but I find it easy to believe that it made no difference or the gain was so minimal that it falls within typical dyno test variance.

Anyway, good luck and have fun with the theoretical experiments. I'd guess you've added a respectable 10whp and 10lbs tq with all your mods while essentially maintaining the oem tq and hp curves. If you ever have any actual data to show I'll be very interested to see it.

Stock includes the 2" looped snorkel, how certain are you that isn't a factor in that dyno run? Also, only one of the two resonance chambers is oriented towards sound (adjacent the MAF), per Toyota, the other is aimed specifically at mid-range torque (within the intake manifold). Both of them have the effect of smoothing mid-range air demand. The WOT spec came from a Toyota "Master" Mechanic, I'm presuming he knows what he's talking about (EDIT -- my information on this was incorrect 5/24).

Perhaps, I'm not trying to argue that one way or the other. That mod was essentially day one for me and I presumed TRD was offering a genuine enhancement -- if it was just bull____, the boom falls on Toyota/TRD, not me. One comment though, the intended air flow for the stock filter was via the stock 2" snorkel, and that flows far less air than my shorter 3" CAI setup. How certain are you the TRD high-flow isn't a better choice?

Thanks Fred, but please understand, I'm not meaning to be persnikity with this stuff, I'm just trying to interpret and apply as best I can. In absence of a dyno test, comparison between car behavior stock and car behavior now is, I think, closer to 20 per category than 10, and probably with more emphasis on torque than power, but that remains speculation. I can say flatly that simply removing the snorkel made a huge difference, and I'm betting that AEM dyno run keeps it in for the airbox run -- do you seriously disagree?

In any case, I'm expecting the wrap to arrive late week (finally shipped Friday) and I'm hoping there'll be a further improvement in mid-range performance. Attempted application of theory is the only protection I have against taking broad shotgun blasts, and it's clear that approach is expensive (as evidenced by the Weapon-R 'S'-Pipe). The tack I'm taking seems expensive enough :(!

So then with a CAI installed you still have the performance enhancing resonance chamber in the intake manifold and lose nothing but a sound damper. I'm not saying that removing the airbox snorkel doesn't add power, just that I do not believe that it adds as much as a smooth-bore CAI or even a SRI. Assuming that the oem paper filter is too restrictive for a mildly modified 2AZ-FE (we really don't know), a K&N drop-in could also add a little.

As for the "WOT spec" being 62%, I'm not sure what that means but the throttle plate opens to ~80%. Maybe he said 82% or misspoke?


Not at all, I can't be without any test data. Which is pretty much what we're talking about. Without any flow or dyno testing we can speculate back and forth all day about whether your home-brew airbox works as well as a aftermarket CAI or whether your TBS actually adds mid-range torque or wrapping your s-pipe negates the restrictive effect of retaining the scuba with it's small inlet and outlet pipe sizes. I find your theories and unconventional experiments interesting but am also a bit frustrated that all we have for proof is the subjective impressions of a unavoidably biased reviewer. No offense but if you didn't believe in what you're doing you wouldn't do it. I don't see how you could possibly remain totally unbiased and impartial.



I'm sure that Import Tuner left the snorkel intact for the stock baseline dyno run. I'm also fairly certain that removing it doesn't add as much hp/tq as the AEM CAI does. Again we come down to the lack of test data. You say 20, I say 10... I guess we'll never know.

BTW, I removed my airbox snorkel and felt that it added some power too but I also installed a CAI and felt that it added more. However I have no data to support this speculation.

Good luck with it and please, if you ever have an extra $100 to spend, get a few dyno runs. I'd love to see how your theories actually work. :)

My point was just that the 10HP didn't come from simply replacing the air box, it replaced the snorkel as well, and that in itself would easily account for most of that improvement. I don't question that smooth bore piping allows greater max flow than does ribbed, and hence a higher max power possibility (whether or not actually realized by the rest of the engine systems). However, my emphasis is on mid-range performance, which not only requires lower average pipe air flow (including pulse peaks), but also benefits most from resonator flow smoothing (further reducing the peaks). Consequently, I really doubt it's a concern to me, just as I doubt the "scuba" presents a mid-range constriction.

Assuming 62% is the actual spec, I'd hope it's the minimum "acceptable" plate opening -- there's no question there'll be vehicle to vehicle variation. I was very disappointed with that number, since I'm used to hard pedal linkage where a properly adjusted WOT is truly 100%. However, he reiterated 62%. I'm presuming your 80% is measured? If so, that wouldn't necessarily be a contradiction, just a production sample -- hopefully typical (62% is depressing :(). (EDIT -- as already mentioned, 62% is actually not the spec, it's 80% as Fred said. 5/24)

My point here is just that the OE filter flow area is only required to support the 2" snorkel. So, even if it's true that replacing it with a high-flow with no other change would have little effect, if the snorkel is removed, it's a very different landscape. Also, since Toyota's intended intake enhancement is the TRD which includes its own filter and fully replaces the air box/snorkel, it's not clear the OE filter was planned to accommodate more than the snorkel (though to be sure, it could've been).

The thing to remember is I'm not targeting power per se'. I'm not talking high rpm, I'm focused on mid-range performance. I'm not saying what I'm trying is a way to achieve a fast N/A track car. Some or maybe even all aspects may help, but by themselves, they're clearly insufficient (your intake and "scuba" concerns being examples).

As for the things I choose to try, my interpretation of theory leads me to believe they provide my best shots at mid-range performance enhancement. Yep, I'm hopeful each item will benefit me (otherwise I wouldn't spend the money), but I'm not flatly assuming it up front -- I want a little driving behavior corroboration before concluding it worked. Problem there, of course, is objective measures are hard to come by. I end up looking at things like (for example) how hard it was to keep up with quick traffic from a standing stop going up a hill to a light -- then Vs now.

As I said above, I don't doubt smooth bore piping has a flow advantage over ribbed piping. I added 10 primarily due to your apparent dismissal of my air box based CAI in comparison to the AEM (meaning you were leaving off somewhere around 10). I'm quite certain they're nowhere near 10HP apart, hence my pointing out the snorkel. In any case, I don't even know what the OE WHP is, I'm thinking the published 158 number is measured at the flywheel.

Man, I don't even know where I'd take it for a competent dyno test. If I ever get finished with it though, I admit it would be interesting to give it a try :).