full boost but no power

[slamed_s13]

Full boost but no power! I have GT2871R on my blacktop pushing 14psi. It hits full boost around 4000rmp but it doesn't feel like it's pushing 14psi, it feels like.....7psi.....what can the problem be?

[cotbu]

Timing, Boostleak, limpmode, tps, etc. You might want to narrow it down a bit, since that question carries a diagnostic charge.?...lol(rmp?)

[!Zar!]

Seems like your turbo could be loose from the exhaust manifold.

[supradealz]

do you have a boost controller? could be a loose vacuum line. i had a line rip off my electronic boost controller and it would make full boost but i only got a little power.
or you could have a stuck or weak blow off valve or wastegate. get someone to rev it and check your vacuum lines, then see if the BOV or wastegate are leaking. if its not vacuum loss then its probably timing or fuel or one of your sensors (maf, map, tps, etc).

[aNskY]

have you checked for codes?

[OBEEWON]

What cams?

[dori_sil8t]

check all ur clamps and couplers.

[BiG MiKE86]

make sure ur BOV isnt opening under boost (I had that problem on the dyno) Check ur AFR's during boost if u haz a wideband as well...

[eclipse_dsm]

You should post more specs about your setup. If it's hitting full boost ok with no wierd noise or bogging that would typically eliminate exhaust and vaccum leaks. I would think your timing is being retarted by the ecu. Possible issues could be maxed out MAF or some knocking. GL!

[Walperstyle]

^yeah, what MAF are you running?

[slamed_s13]

Sorry guys, here is my spec.

GT2871R
SOHC MAF
greddy elbow
tru aem boost controller
greddy type RS
megan manifold
stock injectors
no cat straight pipe
koyo radiator
eletric fans
stock internal

I had just recently worked on the motor (put new pistons and rings with stock bore) and just reached 10,000 miles which means that the motor has been broken in. Last night, I tried clean my MAF and broke one of the sensor pins so I got anther MAF senor from my friend's non-running SR and the car ran like a beast. But now it's acting up again....I really believe that it's the timing issue. I will probably check the timing with a timing gun this weekend.

[Crazian609]

Check your Vaccum lines to your throttle Body... Had the same problem... U most likly have them backwards..

[yokotavia]

stock injectors with a 2871r?...

and 14 psi? try turning the boost down to like 10 or 11 psi and see how it pulls then.

could be maxing out your injectors and running really lean

[slamed_s13]

Wow, problem solved. I finally got to pull out the full potential from the SR. NEVER T ANYTHING FROM THE BOV LINE!! I had my boost gauge Teed from the bov line, what a shame. But it seems to have another problem.....it started today before I fixed the vacuum lines. The RPM fluctuates when I'm coming to a stop....the needle jumps up and down around 2,000rpm-3,000rpm and it eventually dies when I come to a stop. It cranks right up but I am afraid that one day I'm going to get stuck. Bad fuel pump? Bad ground on MAF...? It's a headache....one problem after another. And I still need to replace my clutch, it's slipping really bad. :(

[!Zar!]

You don't have any engine management AND you're rocking stock injectors?

UGH. You're going to blow your shit.

I hope you at least upgraded your stock fuel pump... right?

[slamed_s13]

yea walbro fuel pump. I am pushing only 14psi.

I found out that there is another problem....the turbo elbow was loose.....it was missing 2 bolts. So i've had an exhaust leak before the O2 sensor. I am going to have to get that fixed......along with the clutch....

[BlackTruenoAE86]

Turn your boost down bra.

[slamed_s13]

Turn your boost down bra.


lol, yea, maybe that's what i should do.

[steve shadows]

Sorry guys, here is my spec.

GT2871R
SOHC MAF
greddy elbow
tru aem boost controller
greddy type RS
megan manifold
stock injectors
no cat straight pipe
koyo radiator
eletric fans
stock internal

I had just recently worked on the motor (put new pistons and rings with stock bore) and just reached 10,000 miles which means that the motor has been broken in. Last night, I tried clean my MAF and broke one of the sensor pins so I got anther MAF senor from my friend's non-running SR and the car ran like a beast. But now it's acting up again....I really believe that it's the timing issue. I will probably check the timing with a timing gun this weekend.

You need to re-tune the car properly to match your much larger compressor/turbine and other parts.

Otherwise the car will feel slower than it was before. EVERYTHING changes when you bolt on a turbo with that much of a change in cfm etc.

[dangarnett]

Wow, problem solved. I finally got to pull out the full potential from the SR. NEVER T ANYTHING FROM THE BOV LINE!! I had my boost gauge Teed from the bov line, what a shame. But it seems to have another problem.....it started today before I fixed the vacuum lines. The RPM fluctuates when I'm coming to a stop....the needle jumps up and down around 2,000rpm-3,000rpm and it eventually dies when I come to a stop. It cranks right up but I am afraid that one day I'm going to get stuck. Bad fuel pump? Bad ground on MAF...? It's a headache....one problem after another. And I still need to replace my clutch, it's slipping really bad. :(

Hmm, that sounds like a problem I'm having. I have an hks bov and it was hooked up to the correct vacuum line coming out after the TB, but the bov wasn't opening. So I T'ed into a line from the FPR but it gets vacuum from before the TB. So now the BOV opens but it isn't pulling as nice :(
Should I hook the right vacuum line up even though the bov isn't opening? Or should i keep it t'd into the fpr and boost gauge?
specs are
rebuilt s14 sr -t28
272 bc cams
bc valve springs retainters
alum. pistons

quick question also...since I got it back from the rebuilt around 2500-3000 rpms it is REALLY jerky if I get on the throttle. Anyone know what this would be??

[slamed_s13]

Ok, I thought the problem was fixed but it's not. It sputters and the car just doens't want to accelerate. The boost is set at 10psi and when I try to get on the throttle, it starts to sputter and gets jerky around 3000rpm. Another thing is that my boost gauge needle fluctuates after passing 0psi (basically the needle is shaking as I boost). The turbo spools up fairly fast and it does hit full boost so I really don't think there is a boost leak. Can this be a timing issue? Maybe bad ground on the MAF? Any ideas?

dangarnett (http://zilvia.net/f/members/dangarnett.html), defnitely our problems sound similar. The car just doesn't want to go.

[DirtyOldMan]

i say timing, i had the same problem when i ran a TopSecret ecu for my rb, the timing set was too retarded for the ecu. so i advanced it and it stoped, but beware, advancing timing without raising octane raises the risk of detonation

[slamed_s13]

THE SR IS BACK FROM THE GRAVE!!! There was a little hole in the coupler that's in between the compressor and the hotpipe. Due to the high exhaust temperature from the tubular manifold, the rubber coupler melted over time. Now I am going to buy some heat-wrap and put it around the coupler and the exhaust manifold. Now I got one more problem to solve.....the car stays on when I turn ignition key to off position. There is a lifted track on the ECU and it's been soldered. I know for a fact that it's the ECU because I put another sr20 ECU out of my friends 240 and the car turned off. I was just thinking about hotwiring a switch so that I can manually turn it off. The question is, where do I hotwire the stwich to shut the car off?

[S13 curtis]

Bro get an E-Manage and some 550cc or 740cc injectors before turning up the boost.
Also get a Z32 maf because i herd that SOHC maf is maxed out at about 250+ whp.
If i was you i would jus keep it at stock boost to keep it safe for now.

you shouldnt jump the gun and up the boost, you don't wanna mess up that sweet motor.

[Fam0uZ]

Bro get an E-Manage and some 550cc or 740cc injectors before turning up the boost.
Also get a Z32 maf because i herd that SOHC maf is maxed out at about 250+ whp.
If i was you i would jus keep it at stock boost to keep it safe for now.

you shouldnt jump the gun and up the boost, you don't wanna mess up that sweet motor.

i second to that!
you are goin to blow ur shit man!:aw:

[slamed_s13]

Yea, I just turned my boost down to 10psi to be in the safe zone.

[dangarnett]

Hmm...I think my problem is the ECU also. The company that did the srswap kept telling me they were having problems w/ the MAF. Then when they gave me that car, it was running off a non-turbo s14 maf. And it idle really crappy, would stall while driving sometimes. So I got a stock s14 turbo maf, and the car won't even stay on, the idle jumps up and down a few times then dies.
The maf it's running on now is a gtir maf, but it's the best running of the three.
could the shop have thrown on the non turbo maf, and just tuned the ecu to run just to get me it out the door?

[phi_ho1]

z32 map and tune need

[neilsan]

You need to re-tune the car properly to match your much larger compressor/turbine and other parts.

Otherwise the car will feel slower than it was before. EVERYTHING changes when you bolt on a turbo with that much of a change in cfm etc.

With just a new turbo and safe boost levels there's no way you'll LOSE power. True the 2871 flows more per lb than a T25, but the ECU doesn't care what turbo is on the car. As long as you keep the new boost levels safe (and we all agree 14psi is NOT safe w/ stock injectors) so you're not pushing the limits of the stock fuel system, then the stock ECU programming will do it's job proper and meter oxygen density and engine load and compensate with fuel and ignition timing like it always does. The only thing that'll change is drivability, because of the larger turbine and later spool up times, but with a 2871 .64 the difference is very slight.

The only time you really specifically NEED tuning is when you've installed components that are under direct control of the ECU that have a different value than what they replaced, such as a different MAF or higher flowing fuel injectors, which the OP does not have. Obviously you shouldn't run 22psi on a simple maf/injectors rom tune either but you get my point.

OP, adjust yr actuator so the WG is kicked open very slightly in the rest position and you shouldn't go over 12lbs or so. It should feel good and will still be safe till you get bigger injectors.

[Sileighty_85]

Sorry guys, here is my spec.

I had just recently worked on the motor (put new pistons and rings with stock bore) and just reached 10,000 miles which means that the motor has been broken in.

Nobody else caught that? You cant just slap in stock bore Pistons and rings (unless you resleeved the block) Unless you Mic'd the cylinder walls
and everything was dandy and honed them afterwards

On old engines over time the cylinder walls become uneven like \ / or / \
so you need to bore them out to look like this | |.
Just beacause you see the crosshatch on the cylinder walls doesnt mean the cylinders are still good


With just a new turbo and safe boost levels there's no way you'll LOSE power. True the 2871 flows more per lb than a T25, but the ECU doesn't care what turbo is on the car. As long as you keep the new boost levels safe (and we all agree 14psi is NOT safe w/ stock injectors) so you're not pushing the limits of the stock fuel system, then the stock ECU programming will do it's job proper and meter oxygen density and engine load and compensate with fuel and ignition timing like it always does. The only thing that'll change is drivability, because of the larger turbine and later spool up times, but with a 2871 .64 the difference is very slight.

The only time you really specifically NEED tuning is when you've installed components that are under direct control of the ECU that have a different value than what they replaced, such as a different MAF or higher flowing fuel injectors, which the OP does not have. Obviously you shouldn't run 22psi on a simple maf/injectors rom tune either but you get my point.

OP, adjust yr actuator so the WG is kicked open very slightly in the rest position and you shouldn't go over 12lbs or so. It should feel good and will still be safe till you get bigger injectors.


ummmm 10psi on a 2871R is still too much for 370cc Injectors on my S14 turbo I begin to lean out after 10 psi

PSI is not a factor on this its Volume
10 psi on a 2871 is probably eqivlent 16 PSI on a T28

Listen to Steve Shadows he is one of the best Tuners.

YOU NEED A Z32 MAF, 740cc INJECTORS AND A GOOD TUNE TO RUN THAT TURBO
OR YOU WILL LEAN OUT THAT ENGINE AND FRY THE RINGS