Dyno resulsts
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Just to clear up a few things. Final drive ratio has no relevance on what gear in the transmission is closest to 1:1, and in the Z's CD0XX series trannys that happens to be 5th. With that being said I still do most of my dyno tuning in 4th to alleviate stress on the stock motor and just finalize my timing in 5th.
That settles it I guess.
Now your boost issue 
I've been there several times in my life!
There are only a few logical things it can be, lets go threw them.
1. Like you have mentioned, running out of turbo. I dont know anything really about that turbo but from the name I'm assuming 61mm inducer on compressor side? If thats the case that sides not your problem being that it should flow around 60-65 lbs of air.... Do you have specs on the exhaust side? Is it a 62mm exducer? Reason I ask is we have seen several cars were the compressor cfm is irrelevant because you simply cant flow that amount of expanded air through the exhaust wheel. One car we have is stuck at 540whp with a 62mm inducer on the compressor side because the exhaust wheel is too small(dont remember the size) but that compressor should flow over 600whp...
I've been there several times in my life! There are only a few logical things it can be, lets go threw them.
1. Like you have mentioned, running out of turbo. I dont know anything really about that turbo but from the name I'm assuming 61mm inducer on compressor side? If thats the case that sides not your problem being that it should flow around 60-65 lbs of air.... Do you have specs on the exhaust side? Is it a 62mm exducer? Reason I ask is we have seen several cars were the compressor cfm is irrelevant because you simply cant flow that amount of expanded air through the exhaust wheel. One car we have is stuck at 540whp with a 62mm inducer on the compressor side because the exhaust wheel is too small(dont remember the size) but that compressor should flow over 600whp...
So you figure the wheel is to small...?
2. Next would be a restriction anywhere from the point the expanded gasses leave the turbo to where they leave the exhaust tip. A restriction there will limit shaft speed big time, drop the exhaust on the dyno and try again. I know you mentioned that it was 3" but really who knows whats going on in that muffler
3. Any exhaust leak prior to the turbo will also have an effect on shaft speed due to limiting pressure before the wheel. I've noticed this most on turbos that are fairly large for the displacement thats driving them...
4. If your waste gate reference is at the turbo(beginning of system) and and you boost gauge reference is at the end of the system(intake manifold or upper charge pipe ect..) then you simply might just be experiencing pressure drop across the system. To resolve that(well not resolve it, more like disregard it..) simply move your waste gate reverence down the line, cold pipe, prior to TB.
Realistically if everything else is up to snuff what else is there lol.
Hope this helps in any way good luck!
4. If your waste gate reference is at the turbo(beginning of system) and and you boost gauge reference is at the end of the system(intake manifold or upper charge pipe ect..) then you simply might just be experiencing pressure drop across the system. To resolve that(well not resolve it, more like disregard it..) simply move your waste gate reverence down the line, cold pipe, prior to TB.
Realistically if everything else is up to snuff what else is there lol.
Hope this helps in any way good luck!
I will have a look at the rest of the stuff as well. Thanks for your (and others) input.
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A few more comments based on Phunks response.
Exhaust back pressure after the turbo does have a fair affect on end psi. Lots of cars I see on the dyno make more boost after dropping the exhaust Ask Tial, they say spring pressure is only an estimate on boost produced. My car on a tial 3psi spring make a flat 5psi and on big yellow 9psi it makes 10-10.5 flat. And with my turbo in the front bumper I would say me and Sacha have similar pre-turbo length? That would rule out larger springs being necessary.
But then again I could be wrong and he may have alot more length than me
Exhaust back pressure after the turbo does have a fair affect on end psi. Lots of cars I see on the dyno make more boost after dropping the exhaust
Ask Tial, they say spring pressure is only an estimate on boost produced. My car on a tial 3psi spring make a flat 5psi and on big yellow 9psi it makes 10-10.5 flat. And with my turbo in the front bumper I would say me and Sacha have similar pre-turbo length? That would rule out larger springs being necessary.But then again I could be wrong and he may have alot more length than me
A few more comments based on Phunks response.
Exhaust back pressure after the turbo does have a fair affect on end psi. Lots of cars I see on the dyno make more boost after dropping the exhaust Ask Tial, they say spring pressure is only an estimate on boost produced. My car on a tial 3psi spring make a flat 5psi and on big yellow 9psi it makes 10-10.5 flat. And with my turbo in the front bumper I would say me and Sacha have similar pre-turbo length? That would rule out larger springs being necessary.
But then again I could be wrong and he may have alot more length than me
Exhaust back pressure after the turbo does have a fair affect on end psi. Lots of cars I see on the dyno make more boost after dropping the exhaust
Ask Tial, they say spring pressure is only an estimate on boost produced. My car on a tial 3psi spring make a flat 5psi and on big yellow 9psi it makes 10-10.5 flat. And with my turbo in the front bumper I would say me and Sacha have similar pre-turbo length? That would rule out larger springs being necessary.But then again I could be wrong and he may have alot more length than me
the exhaust length pre turbo should not make a difference , my brother has an sti with a tial 44mm waste gate, the spring is set to 14.5 and it holds the boost no problem with a gt35r , even with a boost controller 25psi of boost will kick in at 3k and hold to reline
sti up pipe-downpipe
sti headers
sti up pipe-downpipe
sti headers
Last edited by konrad; Feb 18, 2010 at 02:22 PM.
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I plan on lifting the car tonight and having a look. I will also relocate the boost reference for the wastegate. It will got right before the TB.
At the same time I may weld a small bung or something to measure the pressure in the exhaust after the turbo. This should tell me a lot. I will get to the bottom of it.
Last edited by Boosted Performance; Feb 18, 2010 at 02:31 PM.
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I have some good new.
I got the car up, and started to look for things that could cause this boost problem.
I failed. Two of T-bolt clamps were not tight, as in not tight at all. This would have been two huge leaks, and the turbo would not have been able to overcome the loss.
So stupid, but I guess it's better than an actual problem with the system. I am sure that it will do what it is supposed to now, and make much better power.
Looks like it is going to warm up on Sunday, so I may get out on the highway and do a couple of pulls (if it is safe to do) on video. I know a number of you have been asking for it.
So look for an update next week.
I got the car up, and started to look for things that could cause this boost problem.
I failed. Two of T-bolt clamps were not tight, as in not tight at all. This would have been two huge leaks, and the turbo would not have been able to overcome the loss.
So stupid, but I guess it's better than an actual problem with the system. I am sure that it will do what it is supposed to now, and make much better power.
Looks like it is going to warm up on Sunday, so I may get out on the highway and do a couple of pulls (if it is safe to do) on video. I know a number of you have been asking for it.
So look for an update next week.
Last edited by Boosted Performance; Feb 18, 2010 at 07:57 PM.
Just to clear up a few things. Final drive ratio has no relevance on what gear in the transmission is closest to 1:1, and in the Z's CD0XX series trannys that happens to be 5th. With that being said I still do most of my dyno tuning in 4th to alleviate stress on the stock motor and just finalize my timing in 5th.
Sasha, glad you found the issue, looking forward to vids.
Kudos to your system!! Even with exhaust leaks, it still makes 350rwhp at only 5 psi. My Turbonetics from back in the day when set to make 10 lbs of boost only generated 2 psi of boost when any 1 coupler blew off or was loose. FAIL.
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I had a feeling that it was a boost leak, i just didn't think I missed two couplers.
. I was in a bit of a hurry too, so that will always come back and bite your in the ***.
Just FYI. With regards to my previous Turbonetics set up on a stock block. I had an original tune of 350rwhp at 9psi. I was utilizing a similar cheapie E-Bay 3" Exhaust that used a stock styled exhaust muffler similar to the one pictured above. I then installed some JWT cams and changed the exhaust to a 3" straight single with an Apexi canister muffler on the end and gained 50 rwhp with 1 addt'l psi of boost.
I don't think the cams alone would have upped the hp that much alone on a stock block. I think the OEM styled muffler that is rather restrictive, even with the 3" pipe leading to it. I was tempted to cut it open and see what the hell was in there but never found out. Muffler shop threw it out before I could check.
I just thought I would share my experience as it pertains to your muffler. I know the kit will make tremendous power once you get back on the dyno, I am not worried in the least. Glad you took a second to do some detective work.
I don't think the cams alone would have upped the hp that much alone on a stock block. I think the OEM styled muffler that is rather restrictive, even with the 3" pipe leading to it. I was tempted to cut it open and see what the hell was in there but never found out. Muffler shop threw it out before I could check.
I just thought I would share my experience as it pertains to your muffler. I know the kit will make tremendous power once you get back on the dyno, I am not worried in the least. Glad you took a second to do some detective work.
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Just FYI. With regards to my previous Turbonetics set up on a stock block. I had an original tune of 350rwhp at 9psi. I was utilizing a similar cheapie E-Bay 3" Exhaust that used a stock styled exhaust muffler similar to the one pictured above. I then installed some JWT cams and changed the exhaust to a 3" straight single with an Apexi canister muffler on the end and gained 50 rwhp with 1 addt'l psi of boost.
I don't think the cams alone would have upped the hp that much alone on a stock block. I think the OEM styled muffler that is rather restrictive, even with the 3" pipe leading to it. I was tempted to cut it open and see what the hell was in there but never found out. Muffler shop threw it out before I could check.
I just thought I would share my experience as it pertains to your muffler. I know the kit will make tremendous power once you get back on the dyno, I am not worried in the least. Glad you took a second to do some detective work.
I don't think the cams alone would have upped the hp that much alone on a stock block. I think the OEM styled muffler that is rather restrictive, even with the 3" pipe leading to it. I was tempted to cut it open and see what the hell was in there but never found out. Muffler shop threw it out before I could check.
I just thought I would share my experience as it pertains to your muffler. I know the kit will make tremendous power once you get back on the dyno, I am not worried in the least. Glad you took a second to do some detective work.
I might end up fabricating my own custom exhaust this summer. It would be a 3.5" all the way back, I could even go 4", there is enough room.
Will see how this one works out at the next dyno.
I do think that this one is flowing well, 358whp at only 5.8psi of boost. I don't think I would see that much power if it was restricting flow.
Last edited by Boosted Performance; Feb 19, 2010 at 06:55 AM.
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