best way to decrease spool?

[ftrs13]

ok, Im having trouble with my turbo setup in the aspect of it boosting too soon. Im running z31 turbo, and when Im cruising down the highway at 75, it puts out 7psi(wastegate setting) is there anything that I can do about this?? I hate the fuel milage that I get because I dont need it on the highway, unless I get on it.

ThanksSteve

[absolute]

is your waste gate working correctly? im not a tubo expert just asking, is there a filter on your turbo?, i have a friend that takes his filter off because it spools a little bit faster, and how much throttle are you applying? ckwik might be able to help more ,pretty knowledgable about turbs sorry if i couldn't be of more assistance

[:: orion ::]

Weird...

I've done a KA-T with a Z31 T3, and it spooled quick, but didn't run boost on the highway.

JGS manifold, bottom mount setup.

And a friend of mine, Tony (from ATL) has a similar setup, with a UH manifold, and it acts the same.

Maybe you have a sticky caliper and it's placing a lot of load on the motor, or something along those lines.

But it's not the turbo...IMO.

- Brian

[red240ne]

that's real weird. Do you drive in 4th gear on the highway? lol, I don't see why it would be boosting, if you're just cruising along at around 2500...

curt

[SeVa-S13]

75mph cruising is considerably higher than 2500 for my KA. Not sure what RPM exactly but 45/50mph is more around there for me. Then again, maybe that's just me.

[whiterps13]

at 75-80 in 5th, my car is at 3200-3400rpms

[ftrs13]

I dont think its a caliper, Im applying barely any throttle which is why I think its wierd. driving in 5th ... Im not sure what rpm, but I think its closer to whiterps13s. it spools really easy while driving around town as well. light throttle and as soon as I pass 3000 rpm or so boost starts to climb. Im curious because I havent heard of this from any other people running KAT.

this is making me wonder what I got for a z31. I may have a T25 compressor?? I always thought it was the T3. and was advertised as from the 86 which is a T3. but Im curious now ... would the T25, with the T3 turbine from 88-89 reach boost quicker than the straight T3 model?

[ADAMHU]

the turbine may be so small that it spools up..even at partial throttle....

adam

[ftrs13]

the turbine should be a .63A/R T3, reasonably sized for a KA, but the wheel is stock which may be too small???

[ADAMHU]

i was running .63ar t3 with stage 3 turbine....and that little bugger was so twitchy ...it would spool almost instantly...i can't imagine it with a smaller turbine wheel...

i moved up to a huge .84ar O trim turbine this season.....it flows like mad top end...

[LongIsland240]

the turbine should be a .63A/R T3, reasonably sized for a KA, but the wheel is stock which may be too small???

I'm running the same turbo as you and it doesn't boost at all while cruising even at 80 or so...i don't need that much throttle to maintain speed- something wierd is going on...do you have a boost leak maybe? where is your gauge reading from?

[ftrs13]

wastegate reads from the compressor housing currently, and gauge reads from the intercooler piping before intercooler. Im not sure about the boost leak ... but why would that cause it to spool prematurely, I would think it would be the other way around.

I was thinking up upgrading the turbo, but Id like to use this for a year before changing everything around.

is there any way that I could get the tubine housing modded to fit a stage 3 turbine wheel. that could help a little ... even though it doesnt solve the initial problem.

[red240ne]

you want your boost reading from the manifold. there is pressure drop from intercooler and such.

[fiznat]

lol, premature eboostulation

try telling the turbo to think of something else, like a 1986 rusted out saab turbo in it's underwear or somethin... maybe it might help to relax the turbo, and assure it that it doesnt make it less of a turbo if it cant hold out....

lol Im sorry, I know this doesnt help at all... I just had to...

[newbe40]

fiznat that was so funny I fell out of my chair, after a few, not to make fun of this problem but that response was to much. To your problem you could try adjusting the spring or rod.

[ftrs13]

dont worry, this problem has nothing to do with turbo envy, Id just like to get mine working right.

[C-Kwik]

the turbine should be a .63A/R T3, reasonably sized for a KA, but the wheel is stock which may be too small???

That tells us very little about the actual turbine size. You can choose from several different T3 turbine wheels and still have the same A/R.

And to answer your question about fitting a larger wheel, typically, you can. But check with someone who actually does that type of work. The T3 trims can have different major diameters, which can be crucial in terms of whether or not you can fit a larger wheel.

You can try to create a exhaust manifold leak, so to speak, to bypass a certain amount of air all the time. This would slow down spool.

I'd opt for a bigger turbo myself, but that's just me.

[ftrs13]

I understand that is indescriptive for the turbine size ... I believe its a stage 0 wheel, but dont know the wheel diameters. I actually just had an exhaust leak but that was causing some major problems with the setup, when it was plugged up things smoothed out considerably. I suppose the only reasonable, and best answer is a bigger turbo, but I was hoping to get a year out of this before upgrading.I hear a lot with the dsm guys and "clipping" the turbine, is that a viable option, and does anyone know the approximate cost associated with that?

[IvanAtSPRacing]

Have you checked and adjusted your timing lately? If your timing is retarded, you will spool the turbo too quickly, power will be down, gas milage will be crap, and your exhaust mani will get really hot.

[ftrs13]

that is something that I will look into. as I was driving around yesterday I realized that 75 is at 3200rpm or so, and I started building boost at 1500 rpm in 5th going up a hill ... so I might just need a little larger turbo. I suppose its better to do it now, rather than later.

[C-Kwik]

I'd avoid clipping the turbine wheel if possible. It affects the aerodynamics of the turbo and causes a loss in turbine efficiency. I've never heard of a Stage 0 turbine for a T3. If it were to exist, it would likely be smaller than a stage 1. And the stage 1 is rather small. I wouldn't worry about building boost going up hill at 1500 RPM in 5th. My T4 could build up boost that low under those kind of conditions. Anytime you add more load to the car, you have to push more air through it to get the same acceleration, so you open the throttle more and this causes the turbo to spool sooner. Higher gears will add more load. This is part of the reason why turbos will spool at an earlier RPM in 5th than it will in 1st. Find a flat and level piece of road and try it out there.

BTW, where are you sourcing your boost gauge signal?

[hannibal]

ive read that the Z31 T3 uses a stg 1 exhaust wheel

[ftrs13]

sorry, my bad, its the lowest one, i just got confused. thanks s15

[IvoryJ30t]

get a 10 degree clip on the turbine. it will spool later, and flow more exhaust on the top end.

[Red-KAT]

Why are you reading the pressure from before your intercooler??? I think that’s your issue...

Even my turbo creates pressure there; you need to read off your intake manifold like the rest of us.

[C-Kwik]

I had asked about that, but I didn't see that he already posted that his boost gauge is reading off the intercooler piping. The most important boost reading is the manifold pressure. At part throttle there will be a difference in pressure between the intercooler pipes and the manifold. While this will not cause any differences in the spooling characteristics, it will give you a better idea of what the motor is actually seeing.

[ftrs13]

ok shifted the gauge around a lot, and now reading from manifold, I didnt realize that they were THAT different. although its still boosting a little too early and losing all power up top, on the highway everything is better.

Thanks to All