matty-tC

these are some pointers i figured i'd share with yous guys in respect to tuning your setups so you don't blow anything up (hopefully!!!!). i basically posted something a buddy wrote up but it's good for you guys to know since quite a few will be boosting soon.


i have no warranty on anything i say so don't PM me if you mess something up
****DO NOT HIT BOOST UNTUNED****

1.) Street tune your AFR to be smooth and consistent AFR. 12.7 is safe up around 1/2 bar (7.5psi). you should run about 11.5:1 at 10PSI. anything over 15PSI you should be running 10.8:1 AFR. This is to make safe power so you can have a turbo'd car for longer than a few months and a big bang.

2.) Timing: Use a load bearing Dyno to tune your timing. You will probably be able to leave the timing under vacuum conditions alone. But as soon as boost starts to come on you need to start monitoring closely and modifying it. Monitor knock signals by watching the data logger for sudden plunges in timing advance. If the tming suddenly drops very low on the data logger, the ECU has detected knock. At this point, you need to retard timing. Do the same for part throttle/low boost conditions.

3.) For full boost WOT, you will need to do something similar. Start with a conservative timing tune. For example; Retard timing by -15 all the way across the RPM range @ full boost and @ WOT. There will be a substantial loss of power more than likely. Then start to advance it little by little making dyno pulls in between and watching the torque increase. You will also need to continuously monitor your data logger and AFR this whole time. When you are not getting any more increase in torque with an increase in advance, or you start seeing the data logger timing plunge again, then retard it a few more degrees(for safety), and leave it.

4.) Do a few hard pulls on the street, again monitoring your data logger, and AFR. If everything still looks good. Then you should be good to go.


The guy that wrote the content of this message has a fully built 4g64T (yes 4g64!) from road race engineering with a custom turbo kit running 21 pounds of boost. He did most of the work himself and knows what he's talking about (so even if you don't listen to what I'm saying... I'd feel safe listening to him LOL)

turbo2liter

10.8 is very rich, I have my map tuned 11.5-11.8 on everything over 15lbs boost. Going richer will be fine until you get into the low 10's, it will start misfiring and breaking up a bit.

Our 2L's seem to like 18-20* advance on pump gas nicely. On higher octane gas, I wouldn't go past 22-24* as peak power will be around there on most 1.6-2.4L (judging from B series Honda's, DSM's, and 3s engines).

Chances are you are not going to knock at low RPM's or part throttle. Get it tuned in on the safe side and call it a day. Spend your time tuning WOT, as that's where you are going to blow a motor at.

matty-tC

this is what's recommended for a mitsu 4g64 2.4L SOHC so i'd tend to agree. although for higher boost setups that may come out of these custom setups "out in the wild", i would stick to 11.5 a/f and 93 octane. timing i'd be clueless on this engine though

turbo2liter

It's probably a DOHC engine ;)

18-20* advance is fine on pump gas, just watch the knock count. If it starts pulling timing, retard it a little more and start another dyno pull, just like RRE suggested

matty-tC

the 4g64 is SOHC. I owned one about a month ago
4g63 and 4g63T are both DOHC

seen4ever

I completely disagree with your point #1. A/F in boost shoudl be a constant number in and around 11.5-11.8. it really depends on the car. IE if you tune a WRX to 11.8:1 you just blew it up, it needs to be around 11:1 to get it to operate correctly due to teh sensitivity of the rings.

On a honda, 12:1 is normally the golden number. 12.7:1 even at 5psi is enough to create lot of heat and blow something up quick.

matty-tC

yeah well if you're on a scion site asking question about tuning your boxer engine you should be shot.

and honda's are extremely high compression generally so you'd better swap the internals for 8.8:1 or so in the first place. so hopefully you've already done your homework.

but thanks for the input

turbo2liter

Correct, but if you're building a motor for power, you swap on the DOHC head ;)

Also there is nothing wrong with high compression turbo engines. Had I the chance to do it over again, I'd change out my 9:1 for 10:1 pistons. If you built took two motors, one with 8.8:1 and one with 10:1 compression pistons, and applied 10psi of boost to them, the 10:1 engine is going to make substantially more power. Granted, you will also be able to run less boost on lower octane fuels.

seen4ever

I'm just pointing out there isn't one good a/f ratio. But i know nothing, the last stock honda block I tuned, runs 7.4s in the 1/8th and 11.7s in the 1/4 mile, with a 100% stock block and a bolt on turbo kit, and the irony is his A/F ratio is 11.8:1. My 9:1 built GSR engine which makes in and around 400+whp on pump gas has guess what a 11.8:1 a/f ratio. Yeah, A/F ratio really matter in terms of compression....WAIT no it doesn't that's why i tune timing.

SporkLover

Sorry to beat a dead horse, but I also disagree with the blanket A/F statement. Maybe those are good to start tuning.

I tune A/F based on EGTs, Power gain (i believe that this sort of tuning is best done on a dyno), and somewhat by whats recommended...and of course common sense is mixed in there.... meaning I know what the really lean/rich ranges are....

Wideband and EGT gauge is a turbo tuners friend!

Speaking of EGTs..... does anyone know when the Scion/Yota 2.4L starts approaching longevity issues? On My beater, the DCX engineers say anything around 1700 is fine, but anything much over 1700 sustained for a long time is going to present problems......

matty-tC

yeah but building high compression turbo engines are for racecars. i will never build a 4 cylinder race car. it will be large displacement forced induction.

i'd rather have a low compression turbo'd 4 cyl. for a long lasting daily driver

matty-tC

if i had a cookie i'd give it to you.

i didn't post this as a 100% bulletproof way to tune your car. i was trying to give pointers for people tuning their cars. we're about to have quite a few people with boosted tC's and if they're tuning it themselves (which a lot will be doing i'd imagine) then it would help them to realize the relation between octane, boost, compression ratio, heat, timing, etc. etc. etc.

matty-tC

it wasn't a blanket statement..

and if you tune solely with EGT's you're asking for problems. keep an eye on your knock sensor and at least get an AF reading from a street tune or dyno pull.

i think the temperature you were asking about is a pretty much universal statement for NA->FI conversions. it should work fine on this car

turbo2liter

EGT's are a terrible way to tune. A high EGT can be caused by too much OR too little timing. I.E. you put too much timing in the mix, or you get knock and it retards a lot of timing. Get your a/f lined out, then tune the timing. If you get knock on the dyno, back it off several degrees and make another pull. Monitor knock on the street as well.

SporkLover

Like I said..... I like to tune the AF by EGT + Power Increase + Common Sense + recommended values. I try and find a recommended baseline and work from there. I keep the AF as lean or as rich as needed to be for the best power output, all the while trying to stay within the recommended EGT range, adjusting the timing and fuel as needed. Not sure how it is on other cars, but with SRTs, even with a perfect AF ratio, and as much allowable timing without Knock, and you often get pretty close to the edge of the allowable EGT envelope.

This is of course all assuming you have some sort of tuneable engine management system and a wideband.

And I agree... tuning by EGT alone is terrible. I guess I left out my assumptions earlier.

turbo2liter

Fair enough. Just wanted to cover the basis so some noob's didn't slap on an EGT and start leaning sh*t out.

matty-tC

which is why i posted this thread.. so people could read and learn

unlimited77

I read everything but i dont understand the vocabs so i am still somewhat lost, but now know some of the terms to comprehend it.

I am a visual learner so i need to see it and see how it works before i can comprehend, but it seems like u all know you stuff which is nice to know.

Marshall

What would be your recommended best-buy for a Boost Controler?

TimmyT

Profec type S