Slamhd

Hello.

running my turbo with 4.1l kit and gt30rs twins

but my graph shows us torque dip at 5500rpm.

some said it caused by poor gt2 intake manifold.

If it true, I will change mine soon but before that I'd like to know which one is best for 997.1 turbo.

996 GT3
997 GT3
997 GT3 4.0
997.1 Turbo (stock)
997.1 GT2 (now)

would you let me know which one is best for me?

My engine spec is

80.44mm crank with 103.7mm pistons and sleeve
ferrera valve kit with 1mm over valves
stock intake cams and 996 gt3 cup exhaust cams
inconel stud bolt kit
gt30rs twins
tial waste gate x2
wavetrac lsd
and all brand new parts and sensors without block and head in engine parts

Below picture is yesterday dyno sheet



Please let me know how to pass that torque dip range and some advice to do.

Thanks.

eaks

Who did the tuning on this car? I would suggest you reach out to your tuner. Someone here might have some input but I haven't seen a build quite like this (using 996 GT3 cup exhaust cams, ect).

I have dealt with Kevin from UMW and he has been great. Might be worth a shot giving him a call and get some feedback from him. http://ultimatemotorwerks.com/

Good luck and keep us updated.

Slamhd

Thanks for reply.

It's my first thread.

I don't know who set up like this, but in my oppinion when previous owner tune it with 996 tt mod style.

I found some thread about tune 996 tt with gt3 ex cams.

So He might be tune like that.

And that time, there is no high cams for 997 tt.

It make me lay off engine again cause my tuner didn't know 996 GT3 Cup ex cam need timing with 9661/2 tools.

When I timing again, there is 10nm more torque all around.

But still around 5500rpm torque dip.

I never seen dyno graph like this and US tuner said it came from Poor GT2 intake manifold.

Find a way to get out from torque dip..

eaks

I am sure someone with more knowledge may comment.. You could always look to go with a idp plenum and y pipe. I was told by Kevin (umw) that these mods are not recommended unless you are on a bigger build with non vgt turbos. He also mentioned the larger throttle body can cause issues (mainly with drivability.. Under wot shouldn't be a huge issue so I doubt this is your issue).

It is quite possible this is why you are seeing the dip but as mentioned I have not quite seen a build like yours and not familiar with how those mods all interact.

I assume you don't have any data logs during the run?

pete95zhn

Yes, if you're using 997 GT2's intake distributors you're encountering that dip and there's no way around it. BTDT some 10 years ago. This is one solution for your problem: AIRFORM
Feel free to ask more, PM or e-mail...

Slamhd

Thanks I ask him right away.

Slamhd

Hello. I sent DM from instgram. I'd like to know which one is best, and why gt2 intake is worst. Thanks.

lliejk

From the post referred to, it looks like the flow numbers for the GT2 manifold were not as good as other IM's:


What is interesting is the GT3 IM's flowed very well. I am pretty sure, though, you cannot mount a GT3 IM on a 997 engine.

The GT2 analysis must be based on Note #3 where flow is unstable, as the flows are better than the stock Turbo IM flows.

I thought I had seen where someone had done up a polished metallic IM, but that may have been for a different 911.

Ed

Kevin

The 997GT2 intake is made out of aluminum. There is plenty of metal in the sidewalls to increase the runner diameter. cut the runners in half, port and then re-weld. The main limitation on the 997GT2 intake is the plenum diameter that runs to each bank intake plenum. It is smaller in diameter vs the stock 996TT, and 997TT. I'd increase the piping diameter.

Slamhd

Thanks I also seen about custom intakes too. but there is no way to buy it and Some tuner's using GT3 intake for TT.

I think he's intake looks so advantage for TT.

Before decision, I want to know every gt3's intake bench testing data.

Slamhd

Thank you for advice.

Cutting intake and welding it is too heavy work for me.

Some one told me that torque dip cause by low boost.

That dyno data was 0.95bar boost.

AFAIK my previous owner run peak boost about 1.7~8bar boost.

If I rise boost up to 1.8, I hope torque dip disappear.