Can not boost past 20psi - GT35r

gsxrtalon · 10-04-2008, 09:37 PM

My problem is I am tuning my GT35r and I attempted to turn the boost up past 20psi and no matter how much I turn my MBC I can not get past 20-21psi on my boost gauge? Is this a MBC problem or WG problem? I have a Tial 38mm and Im not sure what spring I have.

->PrOjEcTGS<- · 10-04-2008, 09:41 PM

Could be both. I would venture a guess that it is a wastegate problem though. Or you have a really really huge boost leak.

T9S1i · 10-04-2008, 09:53 PM

bypass the mbc and run your pressure source straight to your wastegate. This will tell you what spring you have in your wastegate.

If its less than 10psi then you will have trouble boosting past 20psi with a mbc.

This isnt always the case, but the general rule of thumb is that you dont want to or cant run 2x your wastegate spring pressure with a mbc.

jeremy19984g63 · 10-04-2008, 10:01 PM

Also could be your BOV leaking after 20psi.

gsxrtalon · 10-04-2008, 10:05 PM

come to think of it I have a Forge Motorsports BOV and I think the spring I have in it is only a 15psi spring. Ill change it tomorrow and go from there and troubleshoot after that. I bought the WG with the GT35r setup and seller is a good friend and said it boosted fine for him. So Im thinking either MBC or the bov spring I guess.

lccynmbr13 · 10-04-2008, 10:07 PM

You actually choose your blow off valve spring pressure based on the vaccuum your car pulls at idle. Get on TiAL's webpage and look at their spring rates per vaccuum.

brisvr4 · 10-05-2008, 03:03 AM

Quote:

Originally Posted by lccynmbr13

You actually choose your blow off valve spring pressure based on the vaccuum your car pulls at idle. Get on TiAL's webpage and look at their spring rates per vaccuum.

He is using a Forge Bov not a Tial. Forge rates their springs according to how much boost you are running.
If it is only a 15 psi spring then that may be contributing to your problem. Try the yellow or even blue spring and see if that helps.

keltalon · 10-05-2008, 12:59 PM

I have a very similar problem. car will not boost past 20psi. I am currently running a borge warner s259. I just purchased a forge bov. I have not installed it yet, I purchased it suspecting that my 1g bov had failed. i think the only things we have in common is big turbo's and a tial 38mm wastegate. it was suggested to me that my tial might not be fully closing. So it will be interesting to see what you come up with.

gsxrtalon · 10-05-2008, 02:11 PM

Well the member I bought the turbo setup from swears he boosted more than 20psi and I believe him so I think I have a boost leak that gets bad at 20psi that isnt letting me go higher, but the funny thing is that at 20psi Im not running rich like a boost leak should cause. I put my new blue spring in the bov and I still cant get over 20psi so one possibility down.....next going to run a straight line from the boost source to the WG to test it. Then I am going to BLT and see what I get if nothing else.

this_tsi_8urV8 · 10-05-2008, 02:21 PM

I had a boost leak before and I couldnt boost pass 17psi or so. I doubled checked everything, except a coupler that had I rip and wouldn't let me pass a certain boost number. You might have a leak too.

1stGenTSi · 10-05-2008, 02:31 PM

Wastegate spring...

gsxrtalon · 10-05-2008, 07:23 PM

Ok so I just went out and ran the WG unhooked and it still only went to 20-21psi with an open WG. This means there is something wrong with the WG correct? Or would a boost leak at 20psi still cause me to not be able to run past 20psi even with the WG unhooked?

T9S1i · 10-05-2008, 08:26 PM

so you just pulled the vac line off the wastegate? It should never open and you should have boosted to the moon. Something is making it so that your turbo wont make more than 20 psi. Is it really slow to spool, or just normal and then stops at 20 as if you wanted it to?
Is your WG dumped to atm?
I would pull the wastegate and just take a look at it to make sure its not stuck open or whatever.

Have you bypassed the mbc yet to verify wg spring pressure? I would do that first since it doesnt involve any wrench turning. If you have a 7psi spring in there or something then the wastegate is just getting blown open. If its a 20psi spring then something is wrong with the wastegate.

Verify wg spring pressure then we'll go from there.

gsxrtalon · 10-05-2008, 08:40 PM

Ya I know its really strange. I pulled the vac line off the WG and then pulled the vac lines off the boost source and capped them(except for the WG nipple) and it built boost as normal...maybe a 100-200rpm slower than normal and built till 20-21psi and maxxed out there. It pulled good and everything just wouldnt go past 20-21psi. I totally bypassed the mbc and everything, I was waiting for the crazy boost up only 20psi. Im not sure what spring I have buy Ill check it I guess. I have the dump back into the DP. Maybe its stuck open or something????
Maybe I just need a new spring......

TURBOGSX · 10-05-2008, 08:49 PM

I havnt read on here anywhere that you did a boost leak test.i think that would be a good start.

gsxrtalon · 10-05-2008, 08:53 PM

Yes I have done a BLT holding 20+psi. I do have a small leak from my BISS that I am going to take care of but the leak is not causing me to run rich or anything.....I will check the WG spring tomorrow and see if the WG is stuck open or something. I am suspecting the WG spring or stuck open. :S

MY1GDSM · 10-05-2008, 09:00 PM

Quote:

Originally Posted by TURBOGSX

I havnt read on here anywhere that you did a boost leak test.i think that would be a good start.

+1...

gsxrtalon · 10-05-2008, 09:05 PM

Read my last post ^^^

T9S1i · 10-05-2008, 09:51 PM

by bypassing the mbc i meant to take a vac line and run it straight from your pressure source to the wg (bottom port) that way your wg will open at whatever pressure your wg spring is.

Funny thing is when my ebay wg was stuck open i couldnt make boost at all, so if it were stuck open i wouldnt think you would make any boost.
Have you pulled the intake yet to check for excessive shaft play?

MY1GDSM · 10-05-2008, 11:22 PM

Quote:

Originally Posted by gsxrtalon

Read my last post ^^^

Went to post that before you had reply'd... Was in the middle of somethin'

gsxrtalon · 10-06-2008, 06:50 PM

I did hook the boost source right to the WG and same thing happened. Im thinking its a boost leak.

I took the WG apart and found I have the big red spring and it wasnt stuck open so this leads me to believe its a boost leak.

Ps. My bov is making a weird clicking noise once on throttle. Just as the throttle is pulled it clicks as if its lifting and setting again???? weird