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Rb26 Gt-ss Turbos - When Should Boost Kick In?

justinfox

By justinfox,
in Engines & Forced Induction

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justinfox Mentor

justinfox

Posted
Posted (edited)

Hi guys,

I have a fully rebuilt RB26 in an R32 GT-R. GT-SS turbos, HKS everything else (manifolds, pipes, pistons, rods) + Tomei poncams.

As you've guessed from the above, the car is built for response.

I took it out on track yesterday (Wakefield) and damn it's laggy. Boost starts kicking in at 4500rpm. Is this normal? I also drive an EVO 6.5 dead stock and that kicks the boost in at 3000rpm. I know I shouldn't be comparing the GT-R to the EVO. But I just wanted to know whether or not full boost at 4500rpm is normal?!

Maybe it's more about the car being so slow off boost. It's ridiculous, slower than a Barina off boost!!! Any suggestions, feedback, opinions, all appreciated. Thanks.

dyno.jpg

UPDATE UPDATE UPDATE 29/NOV.

It was the boost controller! Wasn't set up right. Wheeeee!!! Much more response, a whole lot smoother on boost too. Now to take it to the track again! Shame it's so damn hot at the moment.

Edited by justinfox
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GTRsean Grand Master

GTRsean

Posted
Posted

Funny! GTSS turbs were what I was going to get due to responsiveness.

It could be: Tuning what sort of mapping was done in the spool up low revs area.

Restriction in exhaust?

Maybe if you had GTRS turbs you would have this issuse but you don't and thats crazy it's so laggy!

Anyway good luck on your problem.

Blitz Grand Master

Blitz

Posted
Posted
Hi guys,

I have a fully rebuilt RB26 in an R32 GT-R. GT-SS turbos, HKS everything else (manifolds, pipes, pistons, rods) + Tomei poncams.

As you've guessed from the above, the car is built for response.

I took it out on track yesterday (Wakefield) and damn it's laggy. Boost starts kicking in at 4500rpm. Is this normal? I also drive an EVO 6.5 dead stock and that kicks the boost in at 3000rpm. I know I shouldn't be comparing the GT-R to the EVO. But I just wanted to know whether or not full boost at 4500rpm is normal?!

Maybe it's more about the car being so slow off boost. It's ridiculous, slower than a Barina off boost!!! Any suggestions, feedback, opinions, all appreciated. Thanks.

Something is definately wrong there Justin.

I have GT-SS's on my car and they are probably the most responsive turbos you could pick for your RB26

I will check my dyno sheets later tonight and get back to you with some more info if you like.

Blitz Grand Master

Blitz

Posted
Posted
yeah im a bit curious about this too

cause i am planning on getting GT-SS's for my gtr and if thats the lag i dont want them

RellikZephyr

Easy tiger, dont go changing your plans because of this - there is something else going on thats causing Justins turbo lag

Roy Grand Master

Roy

Posted
Posted

Your car seems to be a ball ache. First the 2530s were laggy, now the GTSS. Have you been for a ride in other cars with similar setups. You should have gone for a ride in the white R33 GTR at Wakefield, basically a std motor with turbos bigger then yours.

If its worse then your car then there is a problem with your car. If its about the same then you have to come to terms that you are running twin turbos, which can provide almost 600hp of airflow, but with only 2.6L... it is a turbo car.

Your EVO runs a small little turbo with boost up the brazoo...so will always be responsive, will especially feel that way because of the gearing, weight and turbo of the car

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

GT-SS should be on the juice virtually like a standard turbo, and just have a LOT more top end compared to the stock turbos.

There is something wrong with

1) Boost Control

2) Tune

3) Cam setup

4) Exhaust restriction

Thats some stuff go get started with, but for anyone else thats reading this, this is NOT normal for GT-SS turbos.

So dont be put off by them, this setup just has issues :whistling:

PhilGTR Rising Star

PhilGTR

Posted
Posted
I am pretty sure it's the tune. Here's my dyno sheet.

dyno.jpg

I have a similar problem with my r34n1's and my mechanic reckons its the tune cuz my exhaust cannot be blocked (or so i assume as I have a new cat as well as front pipes) So im going to get mine road tuned in a couple of weeks to see if they can find the problem. Good luck with yours!

justinfox Mentor

justinfox

Posted
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Posted

That's all I got dyno sheet wise. It's on 1.2bar.

Exhaust is fine (HKS manifolds, piping kit, front/dump, high flow cat + Kakimoto Regu96 all the way back).

Boost is controlled via AVCR. I would love to get someone else to tune it but that will definitely void my warranty on the engine as currentlky the builder is the tuner. Looks like I'm in a situation then huh?

PhilGTR Rising Star

PhilGTR

Posted
Posted
Do you know the boost settings and gain settings on the AVCR?

What type of computer do you have?

Hmm interesting i may have to check my boost controller see if they set the gain really low!

Blitz Grand Master

Blitz

Posted
Posted
That's all I got dyno sheet wise. It's on 1.2bar.

Exhaust is fine (HKS manifolds, piping kit, front/dump, high flow cat + Kakimoto Regu96 all the way back).

Boost is controlled via AVCR. I would love to get someone else to tune it but that will definitely void my warranty on the engine as currentlky the builder is the tuner. Looks like I'm in a situation then huh?

Justin, I dont know of anyone who has ever tried to claim on a warranty for an engine rebuild!

Take the car to CRD and get Jim to sort it out or at least check the tune without adjusting it so your warranty is safe but you will hopefully then know exactly whats going on/holding you back.

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