boost spiking!!, need help, pros are insisted to advise
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Joined: Mar 2012
Posts: 114
It's not the BoV. At least, not in my experience. I changed my BoV almost immediately to a Turbosmart Race-Port (which I love), and I had no issue holding boost...
I totally believe that it's the absence of the catalytic converter that is causing your problem. Period.
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Scionetics
KAD
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Joined: Oct 2005
Posts: 11,936
From: Western NY
Exhaust back pressure will play a role in boost response 100%. ALL wastegate springs are referenced off of a backpressure ratio of at least 1:1. This means the spring will respond accordingly when there is 1 PSI of boost in the intake manifold and 1 PSI or more in the exhaust (back pressure). Should you LOWER back pressure by running a less restrictive exhaust and/or open downpipe etc, you effectively change this ratio which responds on the pressure differential therefore, allowing more boost to occur.
The manifold design, if the wastegate priority is not correct COULD also cause creep issues as well.
If you have an auto trans, the trans loads up VERY differently every time the throttle is punched. It can make tuning very difficult. The manual mode also opens up the throttle a little differently as well than the auto mode. All of these variables can make tuning an auto a challenge, but it can be consistent. Here is proof. Notice the 9 PSI and hold?
The manifold design, if the wastegate priority is not correct COULD also cause creep issues as well.
If you have an auto trans, the trans loads up VERY differently every time the throttle is punched. It can make tuning very difficult. The manual mode also opens up the throttle a little differently as well than the auto mode. All of these variables can make tuning an auto a challenge, but it can be consistent. Here is proof. Notice the 9 PSI and hold?
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SL Member
Joined: Mar 2012
Posts: 114
Exhaust back pressure will play a role in boost response 100%. ALL wastegate springs are referenced off of a backpressure ratio of at least 1:1. This means the spring will respond accordingly when there is 1 PSI of boost in the intake manifold and 1 PSI or more in the exhaust (back pressure). Should you LOWER back pressure by running a less restrictive exhaust and/or open downpipe etc, you effectively change this ratio which responds on the pressure differential therefore, allowing more boost to occur.
The manifold design, if the wastegate priority is not correct COULD also cause creep issues as well.
If you have an auto trans, the trans loads up VERY differently every time the throttle is punched. It can make tuning very difficult. The manual mode also opens up the throttle a little differently as well than the auto mode. All of these variables can make tuning an auto a challenge, but it can be consistent. Here is proof. Notice the 9 PSI and hold?
The manifold design, if the wastegate priority is not correct COULD also cause creep issues as well.
If you have an auto trans, the trans loads up VERY differently every time the throttle is punched. It can make tuning very difficult. The manual mode also opens up the throttle a little differently as well than the auto mode. All of these variables can make tuning an auto a challenge, but it can be consistent. Here is proof. Notice the 9 PSI and hold?
Thanks for the response. The design on the manifold shows that the wastegate does not prioritize the rear two manifold pipes. If you remove the catalytic converter, you remove tons of back-pressure, which allows the rear two manifold pipes to dump directly into the turbo. In the picture below, you'll see the DESCENDANT manifold, with the TIAL wastegate set-up. This wastegate is in the direct front of the manifold, while the dump is behind it. While I had a catalytic converter, I was holding 8.00 PSI at all times. Without it, we had trouble staying under 18 PSI with a 4 PSI wastegate spring. We fabricated a new wastegate through the CENTER of the manifold and into the dump. Fixed all of the problems, now I'm holding steady at 9.00 PSI, which is exactly where I wanted to be. This is WITHOUT a boost controller. I run a full 3" catback exhaust with a very tiny Magnaflow resonator and muffler in the far rear, along with a fabricated Cobb intake to regulate the MAF readings. I don't have boost creep issues. Just proves that removing the catalytic converter is the cause for all of the problems. NOT the BoV, NOT the intake, this was all done far before the 3" exhaust system and I was holding a steady 8 PSI.
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Joined: Aug 2008
Posts: 100
From: UtahScions.com
So do you think this exhaust:
http://www.ptuning.com/html/Item-Des...l&ModelDesc=tC
Would get enough back presser to run a descendant turbo kit?
http://www.ptuning.com/html/Item-Des...l&ModelDesc=tC
Would get enough back presser to run a descendant turbo kit?
at back) I would think would.be ok.
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Joined: May 2011
Posts: 687
From: Chicago, IL
Lot of knowledge being thrown around in this thread alone. Good stuff!
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Joined: Mar 2012
Posts: 114
No worries. I know what you mean by "pick this company, no that company" but trust me, if he doesn't get it fixed with this kit, he's got the money to go to another kit and sell it the current setup to someone else. That's why i mentioned a different option. His build has been a work in progress and i know his frustrations.
Lot of knowledge being thrown around in this thread alone. Good stuff!
Lot of knowledge being thrown around in this thread alone. Good stuff!
Absolutely. This thread should help a lot of other peolpe also. And trust me, I know the frustration of it also... take a look at my build thread, I actually fabricated a second wastegate. The Descendant kit is great, and there are a lot of ways to fix the problem... but obviously DEZOD is a great company.. even posted in this thread. So there are many options. But, the smarter route would be to just make this kit work the intended way, because it is an excellent kit (also, it'll save him a ton of money)...
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Joined: Jul 2005
Posts: 1,902
From: PTuning
Should be no excuse from any tuner to have a car stall.. at all. I just talked to the OP on the phone, but for other readers, I will just go over it. You should NOT REMOVE the CAT from your exhaust set-up or you will have boost creep issues. The catalytic converter allows you to have much-needed back-pressure for the waste-gate on the exhaust manifold. Remove the catalytic converter, and you lose your back pressure. The way the manifold-wastegate combo is designed, the wastegate will only relieve the excess exhaust from the FRONT TWO PIPES and not the REAR TWO PIPES if you remove your catalytic converter and back-pressure. The exhaust from the rear two pipes will go directly back into the turbo causing boost creeps at high RPM and gear. Major boost creep. A boost controller will not help... You have two options.
1. Add a secondary wastegate to the CENTER of the manifold to allow more exhaust to vent.
2. Reinstall your catalytic converter.
As to the stalling issues, that is going to be your MAP VOLTAGE. I will send you the map for your tuner. For me, I am always 14.7 under 3,000 RPM and when I'm out of boost.. no exceptions. Maybe 14.9, 14.5, etc. It doesn't vary, that's very dangerous.
You have my number, let me know if you have any questions. Here's my thread for further reference.
http://www.newscionxb.com/123-2nd-ge...ld-thread.html
1. Add a secondary wastegate to the CENTER of the manifold to allow more exhaust to vent.
2. Reinstall your catalytic converter.
As to the stalling issues, that is going to be your MAP VOLTAGE. I will send you the map for your tuner. For me, I am always 14.7 under 3,000 RPM and when I'm out of boost.. no exceptions. Maybe 14.9, 14.5, etc. It doesn't vary, that's very dangerous.
You have my number, let me know if you have any questions. Here's my thread for further reference.
http://www.newscionxb.com/123-2nd-ge...ld-thread.html
Thread Starter
Joined: Jan 2012
Posts: 235
From: Lincolnwood, IL
Thanks to Paul, mike, and rj for all of your advice. Believe it or not every bit of advice and all the possibilities thrown out by everyone have helped out a lot. I'm expecting my stock exhaust soon. Some guys stole my long pipe with the cat and resonator.. I will let you all know what happens after I put my stock exhaust back on. Once again thank you all. And no there is no such thing as thread Jacking here, this is a thread very important to everyone that goes boosted or is planning on it.
Thread Starter
Joined: Jan 2012
Posts: 235
From: Lincolnwood, IL
It's not. The descendant kit was made to work with every states emission and whatnot requirements. It targets a broader market that way for those who are worried about emission requirements. I know that if my car would fail emissions I wouldn't have bought the kit
I hate to break potentially bad news to you but your Descendent turbo kit is for off-road use only and illegal for use on public roadways in all 50 states. It's a nice turbo kit despite it's boost creep problems but like all aftermarket turbo kits, it does not meet emmision requirements in any state. You may pass your state's emmision test (I have twice now with no cats) but legally, you've modified your car's emission control system and it is therefore illegal. Keeping one of the original two cats is better than none but legally you still can't remove the primary cat, etc, etc.
Thread Starter
Joined: Jan 2012
Posts: 235
From: Lincolnwood, IL
and also there are literally thousandsss of cars with modifications. ive never heard of anyone getting in trouble for them. what are the chances of me gettin in trouble for my turbo?
Your chances of getting into trouble for the turbo kit go down dramatically just by you knowing that it's illegal. I don't know how thorough they are in IL during emission testing but hopefully it's similar to MD. In MD they simply plug into the OBD2 port under the steering column and check for trouble codes. If you don't have a CEL lit, you should pass. They don't open the hood or look underneath the car where I go.I'm not 100% sure but I believe the likely result of getting caught would be a fix-it ticket that would require you to remove the turbo kit and have the car re-inspected. After which you could re-install it. More of a PITA punishment than big fines or jail time.
descendant was very disappointing with their kit. they were missing the s pipe and fhad a side mount instead of a front mount like they promised. their instructional video shows a mishimoto radiator in their kit but did not come with one. caused me many problems and too many bumps in the road. however i got the kit for a grand less than it costs right now so i did not complain.
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