on my 81.5mm gsr with my gt35e turbo, i always felt the .63ar was chocking back top end power.

Now that i'm 84mm, it just feels that past 7500 up to 9500 power is dropping, rather than climbing. With ITR cams, that shoudln't be an option.

81.5mm dynos:


low is 14psi, high is 19, turbo setup is the same, the dyno dynamics reads a good deal lower than a dynojet.

so.. I dynoed the little bastard yesterday and low and behold,


power output was dropping in the top end. don't mind the early cutouts of power... my clutchfoot was edge and would engage the damn 2step.

top line was 20psi, bottom line was 14psi, but I really want to know what the hell is up with the top end dying out. i've considered throwing more timing at it, but i think its a chocking issue of the turbine housing.

 

Bump for a legit question and cause Id like to know as well.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">how do you know when your a/r is too small?</TD></TR></TABLE>
Turbine or compressor side A/R, if its turbine side then you'll notice it from overly increasing EGT.

 

well actually both...

as i have a gt35e...

so i have a .63ar turbine housing, which i think is restricting my top end power, as it feels that above 8k it falls on its face.

and I have a e-compressor housing, which may also be the issue??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by seen4ever &raquo;</TD></TR><TR><TD CLASS="quote">well actually both...

as i have a gt35e...

so i have a .63ar turbine housing, which i think is restricting my top end power, as it feels that above 8k it falls on its face.

and I have a e-compressor housing, which may also be the issue??</TD></TR></TABLE>

No one here as of yet stated which Turbine wheel that he's using. A/R is associated with his EGT temperatures, not just power. If his Turbine wheel is not an efficient exducer size, he could lose top end power, but be a bit more responsive in the midrange, as the dyno shows. GT35E has several turbine wheel configurations. A/R is only a 4th of the story. He needs to know that first before giving a definitive answer.

 

just curious, are you making these numbers on pump gas or race gas?

 

i was actually wondering about the turbine housing being too small, the turbine wheel is the standard gt35 turbine wheel with a gt40 compressor wheel.

numbers were made on a mix of 93/110. i won't push 93 octane past 450whp, and while tye dyno dynamics read 425, that would be close to 480ish on a dynojet, hence the racegas mix.

so what i'm gathering is, higher EGTs in higher RPM range will show me if my turbine housing is too restrictive, so i'll do a few pulls and see what the temps stay at.

 

what is the wheel trim of the turbine? 84?

 

Bump for this... Im running the same exact turbo right now on my 84mm... I have the same issues that you do. I am picking up a 35r with the s cover and a .82 a/r turbine today... I will let you know when I get it on and retune.

With that turbo, I made 485whp and 420tq at 23psi.. on a conservative tune.

 

What style manifold are you running? a .63AR might be putting too much restriction and can cause gas recirculation at higher RPMs w/ the typeR cams. If you had a long tube mani this can be prevented OR by switching to a larger AR turbine housing. The longer tube mani will put the restriction further down the exhaust so when the exhaust pulses reflect off the turbine wheel it wont cause the already burnt exhaust gasses to be pushed back to the chamber. My friends 84mm GSR w/ CTR cams currently is having the same problem. He made at least 360 from 6800 to 9800 w/ a peak of 410whp. He's using a .63AR turbine w/ Log INline mani. (62-1 turbonetics turbo)

Things that can fix this:

switching to a larger AR turbine
switching to a cam w/ less overlap
cam tunning
Longer tube manifold
larger downpipe and exhaust

 

i run a full race top mount, and a 3" dp and exhaust.

 

its a custom topmount with a 3in downpipe & 3in thermal exhaust.




turbo flows directly into backdoor garrett intercooler. yes its a skunk2 intake manifold, but it has been ported to hell and back.

 

As far as I know the best way to check this is to measure exhaust manifold pressure. When it starts to become a lot higher than the intake manifold pressure, then thats when the exhaust is becoming a restriction.

 

Man, this is getting more technical than is seriously needed.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TypeSLO &raquo;</TD></TR><TR><TD CLASS="quote">what is the wheel trim of the turbine? 84? </TD></TR></TABLE>

hrmm... let me try to find the precision invoice, but the serial number is gt3561e, and i'm pretty sure it just says gt35 turbine wheel, so no clue on the wheel trim, i just kind of figured its the standard gt35 turbine wheel.