Boost not holding in Second gear

[initialRES]

Ok guys, I tried to search but can't find an answer and I hope you have some ideas.

I have a 98 GSX with intake, joe P manual boost controller, Greddy type S BOV, and a RRE Upper intercooler pipe. When I accelerate in second gear, it will spike to about 20 PSI then just start dropping and by the time I reach 6200 (shift point) it is at about 12 PSI. I can't tell if it does the same in first gear because that gear is so short. In third, fourth and fifth it will spike to 20 or 21 then drop and hold just fine at 16 or 17, wherever I have it set.

I have tried:
- tightening all the clamps and hoses but haven't tried a pressure tester yet. I don't feel like building one, but I will if I absolutely have to.
- Checking all vacuum Lines. All are connected
- I have tightened the bolts holding the turbo and the turbo manifold together.

None of this fixed the problem at all. I don't think it is a boost leak but I have no Idea what else it could be.

 

[Defiant]

T-25? You're running out of turbo. It's like watching Popeye run, with those stubby little legs, he just can't keep up after a given speed. If Olive Oyl didn't wan't to get caught, she'd never need to.

Move your shift down to 5800, and you'll be right in the T-25's fat spot in the next gear.

 

[1fast97gsx]

or turn the boost down cause that's way too much anyway for that lil t25

 

[initialRES]

I've read that the T25 can hold 16 or 17 but no more. Are you saying thats not true? I don't want to burn out this turbo because I can't afford a new one right now. What can it safely hold? In the mean time, I will try shifting lower, see if it will run a bit quicker. Thanks for the replies.

 

[fwdtsi]

I have the same prob. on my 1g, in 2nd it will go up to 18 psi, this is with a big 16g. I thought I had a bad actuator or something but thats not it. It could just be becuase you need porting or something, to fix the problem I just 75% throttle it in 2nd. The funny thing is 2nd and third are the same boost, thats your problem right?

 

[Defiant]

"Boost" is "More air than the cylinders can admit". Once your pistons start moving fast enough, and start taking in enough air per rev, you'd need a bigger turbo to maintain a number on a boost gauge.

Don't run a T-25 over 15 if you want it to live. Don't rev it past a 4-psi boost dropoff.

LarryD had dyno sheets of a T-25 putting out more and more pressure with higher and higher revs. But it was only an experiment, it wasn't meant to be run that way for minutes at a time.

 

[gurrmanator]

"Boost" is "More air than the cylinders can admit". Once your pistons start moving fast enough, and start taking in enough air per rev, you'd need a bigger turbo to maintain a number on a boost gauge.

Don't run a T-25 over 15 if you want it to live. Don't rev it past a 4-psi boost dropoff.

LarryD had dyno sheets of a T-25 putting out more and more pressure with higher and higher revs. But it was only an experiment, it wasn't meant to be run that way for minutes at a time.

I kinda have the same problem,I can run 12 to15psi all day long in all gears but when I turn the boost up(18-20) I only get the boost in 1st gear only,when I shift the boost only builds to 5psi, could I be running out of turbo as well(16g big)?

 

[elementalwindx]

My t25 would spike to 20 somethin if i had the mbc set for 15 or 16psi on 93 octane. but on c16 race gas I would set it for 18 and it would shoot right there and hold like a rock thru the rpm band Not a good thing to do on a t25, but thats just my experience.

For daily I always had it set for 12 or 13 and my t25 had 120k miles on it. When I replaced it w/ my 16g it had a LOT of shaft play and I was surprised it still worked. So yea don't stress your turbo like I did unless you have another ready to replace it.

 

[whitegst97]

I have the same problem, T04E turbo, i was running the Joe P boost controller, i thought the hoses were too thick so i bought smaller diameter ones and still, i get a spike of 18 then drops to 15. I got rid of the Joe P and now im using the adjustable acutator to controller boost, still have the same spike and same 3 psi boost drop. What's the matter here, could it be that getting the boost signal from the BOV line is not too good.