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View Full Version : weird boost spike and taper off on stage one tune



2cB51.8t
11-03-2012, 02:31 PM
I got my ecu tuned by SSP for stage one 93 octane. Pulls good and all I just have a issue with it spiking and tapering off.
Before I chipped it it would hold stock boost perfect. Now in first it will spike to 22 psi then taper off to 13psi at redline. When I shift to 2nd Itll peg my boost gauge at 25 then taper off to 12/13....shift to 3rd then I will peg it again then taper off to 11 by redline.....it is a CK04 with 3" exhaust. Dont hate because i have a CK04. If the turbo wont hold boost it still doesnt make sense to me that it could spike so high yet still not hold a normal chipped psi of 16.....any knowlegeable help would be appreciated

Vierings
11-03-2012, 02:55 PM
Any other work been done recently? Maybe n75?

thenj3
11-03-2012, 03:16 PM
Contact the tuner seems like it could be normal. Just a shitty tune

Vierings
11-03-2012, 03:18 PM
Contact the tuner seems like it could be normal. Just a shitty tune

I've never heard of that tune before, so I agree with you.

2cB51.8t
11-03-2012, 04:11 PM
I was hoping that wasnt the case....he says it should hold 16

2cB51.8t
11-03-2012, 09:20 PM
Has anyone had to use a MBC to get their chipped 1.8t to hold boost before im thinking of trying one......I just find it hard to believe im the only one who has an issue holding boost

2cB51.8t
11-03-2012, 09:42 PM
After some more research Ive read of a possibility that the diverter valve could be leaking boost back into the intake.....any input on that? Im going to check it out

2cB51.8t
11-03-2012, 09:53 PM
After some more research Ive read of a possibility that the diverter valve could be leaking boost back into the intake.....any input on that? Im going to check it out

thenj3
11-04-2012, 05:28 AM
It's possible, is it stock? Do a boost leak test see if there are any leaks. Should have done that first thing.

2cB51.8t
11-05-2012, 04:55 PM
Its not a boost leak If I dont redline in 4th it will hold 14/15 guess none of the real tuners are going to chime in....its not stock its SSP stage 1 tuned like I said....

CCA4
11-06-2012, 11:02 AM
A K04 will never hold boost to redline, shitty tune or not. Just not big enough.

http://i101.photobucket.com/albums/m49/chaos92287/gt3540_spool.jpg

nrowensby
11-06-2012, 11:43 AM
Yep... need a bigger turbo if you want to hold that kind of boost all the way to redline... Sorry

thenj3
11-06-2012, 04:47 PM
Its not a boost leak If I dont redline in 4th it will hold 14/15 guess none of the real tuners are going to chime in....its not stock its SSP stage 1 tuned like I said....I was talking about your DV being stock. To have drop off is normal though. Maybe drops more than other tunes but it's gonna happen from a baby turbo

M-Hood
11-07-2012, 06:15 AM
A K04 will never hold boost to redline, shitty tune or not. Just not big enough.


It will but only if ran at a low boost setting, he would have to run it around 15-16psi to hold that amount of boost to redline. Once the turbo is pushed above that it is going to taper off in the higher rpm's since the acceleration rate of the wheels are slowing down.


He needs to talk to the tuner and ask how much boost the tune is designed for, if it isn't designed for 20-25psi then there is an issue.

2cB51.8t
11-07-2012, 06:49 PM
A K04 will never hold boost to redline, shitty tune or not. Just not big enough.

http://i101.photobucket.com/albums/m49/chaos92287/gt3540_spool.jpg

THANK YOU! That makes more sense having that to look at.

2cB51.8t
11-07-2012, 06:59 PM
It will but only if ran at a low boost setting, he would have to run it around 15-16psi to hold that amount of boost to redline. Once the turbo is pushed above that it is going to taper off in the higher rpm's since the acceleration rate of the wheels are slowing down.


He needs to talk to the tuner and ask how much boost the tune is designed for, if it isn't designed for 20-25psi then there is an issue.

Its Greg with SSP out of NY and he says 16psi to redline. Maybe its my cheap wannabe K04 wont hold? It will taper off to 10 at redline.....its just strange that it will spike so high and only taper off if I redline. Mid 4th gear it will hold 14/15

Nateness
11-07-2012, 10:57 PM
What condition is your cat in? Assuming that you still have one, a clogged cat could result in diminished boost pressure at high rpm. It's also possible that your waste gate could be leaking at high rpm too.

Can you data log N75 duty cycle, pressure request, pressure actual and plot vs RPM for us?

M-Hood
11-08-2012, 09:17 AM
Its Greg with SSP out of NY and he says 16psi to redline. Maybe its my cheap wannabe K04 wont hold? It will taper off to 10 at redline.....its just strange that it will spike so high and only taper off if I redline. Mid 4th gear it will hold 14/15

It is the high spike of boost that is not going to allow it to hold 16psi to redline, when it spikes up the wheel is already spinning at a much higher speed and then the accelerating speed of the wheel slows down (not the actual speed/RPM) and that causes the boost to drop. If you want it to hold more boost you need to reduce the boost spike.

2cB51.8t
11-08-2012, 05:14 PM
What condition is your cat in? Assuming that you still have one, a clogged cat could result in diminished boost pressure at high rpm. It's also possible that your waste gate could be leaking at high rpm too.

Can you data log N75 duty cycle, pressure request, pressure actual and plot vs RPM for us?

The cat looks good from what I can tell i cut off the 2" flange and fabbed 3" pipe all the way back with a Borla muffler so I know my exhaust is very free flowing.
I need to get a VAG COM and learn how to log duty cycles...Im still new to Audi ive only tuned the AEM controler on my truck. So is all I need a VAG COM plug? do I need any software?

2cB51.8t
11-08-2012, 05:23 PM
It is the high spike of boost that is not going to allow it to hold 16psi to redline, when it spikes up the wheel is already spinning at a much higher speed and then the accelerating speed of the wheel slows down (not the actual speed/RPM) and that causes the boost to drop. If you want it to hold more boost you need to reduce the boost spike.

Thanks for all the replies it means alot to me guys! That makes perfect sense Mike. So since my ecu is in control of the N75....Im confused is to what to do to stop spike.....even if I ease into pulls and not let it spike it tapers off. Its so weird Im going to go back thru all the piping and check for leaks again just for the hell of it this weekend Im just really doubting its in the charge system

Ill take any advise I can get. Thanks guys

Nateness
11-08-2012, 10:07 PM
The taper effect is inherent to all turbo-machinery. At some point, your turbine will reach a peak shaft RPM. This is usually limited by engine flow characteristics and intake/exhaust piping. Go take a look at a compressor map. Each of the lines are flow curves for a given fixed RPM.

If you're hitting a maximum (limited by either the motor, exhaust piping, or the turbine/exhaust housing/manifold, etc.) shaft RPM, then the compressor will follow the curve. As flow increases, operating pressure drops for a fixed RPM. This is what you're observing. It's known in the engineering world as "riding the curve."

2cB51.8t
11-17-2012, 08:08 PM
It is the high spike of boost that is not going to allow it to hold 16psi to redline, when it spikes up the wheel is already spinning at a much higher speed and then the accelerating speed of the wheel slows down (not the actual speed/RPM) and that causes the boost to drop. If you want it to hold more boost you need to reduce the boost spike.

Any advise to help with my spike problem? Under load when i shift hard is when it spikes bad so what your saying makes sense. Im using Light 15" Moteigi rims too. Im going to get a new diverter valve off a TT. Should I bother trying a MBC? All this bs just makes me want to put a real turbo on with an external wastegate.

andyrew
11-17-2012, 10:53 PM
You should be shifting a stock turbo at 5.5k. Whats peak boost vs boost at 5.5k rpm? Should be within 4psi.

M-Hood
11-18-2012, 08:31 AM
Any advise to help with my spike problem? Under load when i shift hard is when it spikes bad so what your saying makes sense. Im using Light 15" Moteigi rims too. Im going to get a new diverter valve off a TT. Should I bother trying a MBC? All this bs just makes me want to put a real turbo on with an external wastegate.

Well the problem isn't the turbo it is the tuning, some tunes have boost spikes while others do not. Using a MBC in parallel with the N75 will help reduce the boost spikes by adding a 2nd path to open the WG. Other option is to go with a tune that have shown to have no boost spikes.

Seerlah
11-18-2012, 08:34 AM
What is a CK04?

2cB51.8t
11-18-2012, 10:10 AM
Well the problem isn't the turbo it is the tuning, some tunes have boost spikes while others do not. Using a MBC in parallel with the N75 will help reduce the boost spikes by adding a 2nd path to open the WG. Other option is to go with a tune that have shown to have no boost spikes.

Yeah I was afraid of that. It seems like the N75 is all the way shut at first so it spikes as high as the turbo wants to. [o_o] Then tapers off because its slowing down from that spike like you were saying. I can try a MBC but Ill have to do some research on how to install it in parallel, I just have a two port MBC laying around in the garage. Mike if you can recommend a good tune to use with a ko4, 3" exhaust and me planning on taking out the air box out I will probably go that route next paycheck. Ive read about all the out of the box tunes APR, GIAC, REVO etc. but I feel like there are better tunes out there but I could be wrong.

2cB51.8t
11-18-2012, 10:13 AM
You should be shifting a stock turbo at 5.5k. Whats peak boost vs boost at 5.5k rpm? Should be within 4psi.

Spikes to 20+ and is @ 10-11 by 5.5k [=(] so thats a pile of [poop]

2cB51.8t
11-18-2012, 10:21 AM
What is a CK04?

Cheap Chinese replica Ko4 [facepalm] Im not to proud to admit it lol figured Id give one a try because my cheap t3/t4 57mm on my truck has held up for 3 years now with no problems at all

M-Hood
11-19-2012, 07:28 AM
Could be that it also has a crappy WG and WG actuator which is not opening when it should causing the really high boost spike.

2cB51.8t
11-19-2012, 06:38 PM
I acually took the wastegate off the stock turbo and used it on the new one so it shouldnt be that......Thanks for the thoughts guys im going to try a new tune when I get the money

M-Hood
11-20-2012, 06:18 AM
I acually took the wastegate off the stock turbo and used it on the new one so it shouldnt be that......Thanks for the thoughts guys im going to try a new tune when I get the money

Did you make sure that when you put it on it was set at the correct spring pressure? If it is too tight you will get boost spikes since it is not opening at the right pressure.

2cB51.8t
11-20-2012, 08:03 PM
Ya I did a lot of research on how to set the tension and watched some vids.....I basically mimicked the stock turbo tension which in just a couple threads tight after its closed....Its funny the car runs awesome after all the engine work i did but i cant live life without more power lol

seanj130
11-20-2012, 08:06 PM
Cheap Chinese replica Ko4 [facepalm] Im not to proud to admit it lol figured Id give one a try because my cheap t3/t4 57mm on my truck has held up for 3 years now with no problems at all

Just keep the boost under 15 psi with that bad boy and it should hold up forever. those things blow with high boost for long periods of time.. or just high boost in general. Other than that I have hear nothing but good stories from low boost applications. But then again. who wants low boost..

2cB51.8t
08-19-2013, 09:45 PM
So people Ive got some update information on my boost spiking issues.

Ive had the car retuned for the CK04 I have. Ive put in larger fuel injectors and FPR. Replaced the DV with a new one. Replaced many split hoses.

The car still spikes very high....even higher than before---25+ psi never going into limp at all. Now Im hearing ping once the boost is over 20-22 psi and its rediculous. @ redline once load goes down boost is @ 18psi.

Ive read that the cheap K04 turbos were famous for tiny wastegate ports and cant bypass enough exhaust gas fast enough under load to keep the turbo from spiking.

So I could try to port the wastegate and see how that works.... Ive even heard of some people changing the n75 duty cycle to work around the wastegate issue although It sounds mechanical if the exhaust just cant escape. Im just tired of this.

Im on the look out for a VAG COMM setup so I can start logging and making necessary changes. Im not opposed to buying a BW K04-15 if thats what I need to do.

Any thoughts would be great guys

ddillenger
08-19-2013, 09:58 PM
I recently tuned a CK04 car, wastegate pressure was 8psi but even with 0 percent WGDC at 5000rpm I couldn't get boost below 15psi. TINY wastegate port was preventing proper boost control. I think you're on the right track. Pull the turbo, port the SHIT out of the gate, and install your k03 actuator set @ 5-6psi.

2cB51.8t
08-19-2013, 10:57 PM
Thanks I was thinking about porting it......Then I came across a Frankenturbo F21L kit for basically $1k and it has a ported WG port with a upsized flapper.....decisions decisions....should have just bought a good turbo to start.....since im tuned for a K04 Im wondering how much Ill have to change the tune since the turbine isnt much bigger

I could port the CKO4 and see how it goes that way im getting to the bottom of my problem then decide hmmmm

andyrew
08-19-2013, 11:29 PM
If you got the time for the R+R then I would try porting your existing turbo. Could be good fun trying to get that turbo to work well :) I always like that kind of challenge.

2cB51.8t
09-01-2013, 05:19 PM
Just figured Id add some more information.

I put in a Hallman MBC today. I just left the n75 plugged in and bypassed the boost lines completely. k0mpresed told me my max boost on my tune should be 20-21 psi so I set the MBC to 20. As of now it peaks at 20 psi and holds 14-15 to redline. I was fairly satisfied. I dont know what was up with the n75 cycle but im cured for now. AEM wideband is here and is going in soon[drive]