Here is my issue.

Yesterday tuning done on my car and was able to get 1.4 bar max. As tuner advise that my ride having back pressure issue and it's knocking if went higher.

Even thu 1.4 he had to play with timing to make it safe. My Q, did you guys had or saw any back prusser from greddy kit.


My setup:

Greddy IC

Greddy turbo kit,

HKS GT600 fuel system.

HKS Y resonated pipe.

Mines Ti cat-back.

Custem Intack.

800cc Injectors.

Ofcoures using haltech.

BTW, on dyno pack, we tuned 2 GT-Rs both greddy kits. other one had HKS intercooler and racing Y pipe with Legamax cat-back. On both car with

1.4bar. My ride did 592WHP while other did 613WHP.

As some will ask why go low.

My target for now until i upgrade tranny and change engine rods. I will keep it safe at 650WHP.

Congrats on finally finishing your car

I hope u will be attending the Automodex

In my opinion i guess your exhaust set up may be causing the back pressure

The HKS race mid pipe dimentions are 75mm x2 - 85mm, im not sure about your resonated but i am sure it doesnt have a larger diameter

The Mines exhaust dimentions are 80mm for the main pipe and 120mm for the tips

While the HKS Legamax is 85mm with 119mm tips

Tips dont really matter that much, the main pipe has the major effect

I hope what i have mentioned is right.........waiting for the pro's verdict

Im also thinking that the Mines exhaust is causing this.

Borrow the HKS legemax from your friend to test if your car still has back pressure issues. Good Luck!

Just got HKS Y pipe strait. to test. First will see if Mines do effect, the 5mm different is not a problem. But will test and see.

Incase id did effect. I will be damed. But, i may buy HKS spec R ti cat-back and add butter flys system to keep it controlled when not in race mode. But, lets see how it goes.

Also, i will submit dyno runs as i get them from tuner. He want me to see the high RPM different from my ride to other GT-R, as i got custem intack.

Let us know bredren.

When you dynoed, what fuel was it running?

we dynoed it yesterday at EXTREME garage, Was on 98 octane pump fuel.

Good luck and keep us updated

Moreover, the Y-pipe diameters may have a bigger effect, there are larger diameter resonated Y-pipes that may fit your taste

Not bad, it should make more power. Did you try VP103? 109? C16?

Nope,

I don't wanna see numbers that i will not feel as am not and never use race fuel.

our 98 RON is like 93 in the USA

98 Research Octane Number (RON) = 93 AKI ( Anti Knocking Index )

http://www.adnoc-dist.ae/eplus/TechnicalInfo.aspx

+1, 98RON ( 93 Octane ) is what you guys have.

You'll defo feel it on the road buddy, give it a shot you'll gain more HP

What was your baseline on this same dyno?

Never did a basline on ny dyno.

Today will do tuning on street as dyno out of service. We installed HKS racing Y pipe and kept the Mines cat-back.

Your back pressure is clearly caused by the small diameter of your y-pipe and cat-back. Try some 90mm y-pipes and cat-backs and it will be resolved ;-)

Custom intake?
This could be the problem.

Any details on the intake?

http://www.nagtroc.org/forums/index.php?sh...=36683&st=0

Custom intake should only be looked at if he is using factory MAF sensors and isn't able to dial in the vehicle. He is currently on Haltech so Im assuming he has removed this function.

Your right, he did remove MAF function.


Today test showed improvement in timing. and gained more power, Thu still knock appears if going more than 1.4. we suspect that HKS fuel regulator is culprit. so tomorrow will install new injectors and regulator. and see how it goes.

Good luck buddy

Are you still running stock gearbox internals?

We did dyno other GT-R that got same setup, Only different is other got HKS racing y pipe with legamax cat-back. and ofc HKS IC. it was fine all way. Also i want to keep it less noisy.

If you're using the FPR from HKS GT600 kit and did no adjustments, please do.

Their FPR's and Fuel pumps are only catered to GT570 kit with no fuel management/tuning. It's just an upgrade for the GT570 with no tuning necessary.

what is your fuel pressure when on boost? i am sure of its not the GREDDY turbos.

thanks
alex

We did not install the fuel pumps. Only FPR installed from the kit. We are changing injecters due of thinking that one injecter may be fualty.





Fuel pressure is not drooping at high boost. Only seen knock after 5krpm. Not sure what pressure is.

UPDATE,


the problem was found.


Faulty Injectors or to be honost. Those was not the injectors i ordered.

I have ordered DW 800cc, got the box and sent them to tuner. But after had not been satisfied with the power, i changed tuner which tried to manage more power and today he checked injectors to call me and ask what was these??

I went there and found that these is not my injectors i bought, they look like bosh that not made for GT-R and a rubber ring used to make it fit GT-R. One injectors nose was dinged.

It's totally shock to see this happen to me. Am not sure if my ex-tuner or the vender have not put the right ones. I don't want to point to someone. Anyways.


my tuner got 2 set of DW 950cc. he installed them and just replayed that it's run fine and got 1.45bar with more better timing.


Am totally happy to find the problem.

Even thu it runs fine. We found that Mine cat-back is about 10-15whp less than legamax HKS. which i can live with as it's much much less noise than HKS.

Congrats!!!!

Man I'm happy you found the source of your problem. Man, did this vendor send you these injectors knowingly or by mistake. If they did so knowingly, I think you got to call them out.