Gt-Rs.. More Boost?

[SoFreshSoClean]

Hi everyone,

Looking for some advice.

I have an R33 GTS25T with:

Pod filter

Intercooler

3 inch turbo back exhaust

Walbro fuel pump (not a fake)

550cc injectors

Oil catch can

HKS GT-RS Turbo

Power FC

Greddy profec bspec 2

Currently it makes 338rwhp on ~15psi. No real blowby to speak of, pretty healthy motor on 97xxx kms.

Basically, I was considering getting a retune and upping the boost to around 18psi. Anyone know what sort of gains I could expect, or should I not bother because I am already making the power most people make out of this turbo anyway? (Boost being a measure of resistance to flow etc etc)

I have also heard claims that the standard exhaust manifold is marginal even at the power I am currently making, is there any truth to this?

Cheers

[joeyjoejoejuniorshabadoo]

1. unless you built the motor or know the person that did then it's not on 97,000 (probably more like 197,000)

2. do it

[PM-R33]

Used to run 20-21psi all day every day for over a year with no dramas (currently running low boost until I tune it for high boost again).

Chuck it on a dyno and see if there is gains to be had. If the gains are marginal than turn it back down.

Mine used to make a lot more power on 18+psi than 14psi, but every car is different.

[SoFreshSoClean]

1. unless you built the motor or know the person that did then it's not on 97,000 (probably more like 197,000)

2. do it

You know this how?

Used to run 20-21psi all day every day for over a year with no dramas (currently running low boost until I tune it for high boost again).

Chuck it on a dyno and see if there is gains to be had. If the gains are marginal than turn it back down.

Mine used to make a lot more power on 18+psi than 14psi, but every car is different.

Thanks mate, can you remember any numbers, like the difference between 14 and 18? Plus, from the all important seat of the pants dyno, was it worth it?

[joeyjoejoejuniorshabadoo]

You know this how?

Thanks mate, can you remember any numbers, like the difference between 14 and 18? Plus, from the all important seat of the pants dyno, was it worth it?

all these people with "80,000" skylines make me lol

as phil said, throw it on the rollers and tune it up until the point of diminishing return

[PM-R33]

230-235rwkw on 14psi and 255rwkw on 18-20psi prior to any head work.

Once the headwork was done the most I saw was 263rwkw on the same dyno on 19-20psi.

Always had the boost start dropping off towards redline though. My tuner didn't really know how to tune the boost controller so my boost curve was fairly average.

At the moment I have retuned it on low boost and the car feels slow as hell, so yeah definetely high boost all the way lol.

However remember every single dyno is different. I've seen cars with dyno sheets saying 350rwkw and then they run it on a different dyno and it will be 310rwkw. It really does vary so I try not to use other peoples dyno sheets to much other than a guide, and just use the same dyno every time you do mods to see if there is an increase on that particular dyno.

[SoFreshSoClean]

230-235rwkw on 14psi and 255rwkw on 18-20psi prior to any head work.

Once the headwork was done the most I saw was 263rwkw on the same dyno on 19-20psi.

Always had the boost start dropping off towards redline though. My tuner didn't really know how to tune the boost controller so my boost curve was fairly average.

At the moment I have retuned it on low boost and the car feels slow as hell, so yeah definetely high boost all the way lol.

However remember every single dyno is different. I've seen cars with dyno sheets saying 350rwkw and then they run it on a different dyno and it will be 310rwkw. It really does vary so I try not to use other peoples dyno sheets to much other than a guide, and just use the same dyno every time you do mods to see if there is an increase on that particular dyno.

Yeah, I was more interested in the hp gain vs boost added, that helps!

Are you running a standard exhaust manifold?

[joeyjoejoejuniorshabadoo]

yup... i make 325 on most dyno's but 280 @ re customs

[JonnoHR31]

20psi+ and re tune

[PM-R33]

Yeah, I was more interested in the hp gain vs boost added, that helps!

Are you running a standard exhaust manifold?

Yep standard exhaust manifold. No point changing it with a GT-RS.