R34 Gtr Garrett -5 Turbo Lag, Need Advise

[baicai]

So what exhaust have you got?

Did he adjust ur cams?

Have you got a boost controller?

Still running the nismo twin 2.5" atm which I think is the biggest restriction, hopefully will get the twin 3" soon. I believe the tomei cam gears was adjusted, but I'm still on stock cams. Yes do have boost controller, it's profec B II. Can you sugest anything else I should do?

[XGTRX]

So y can't u run more boost

[Piggaz]

Not too sure how much bigger intake pipes are going to make when the smallest point of the whole system is the elbows that bolt onto the compressor housings. There is a mod you can do here. Either way, 400 kW on -5's and much more has been achieved with all the stock gear in place many times.

Get a decent sized exhaust on it. Twin 2.5's when you sit down and work it out isn't big at all. I'd say that would be external diameter too which makes things even worse.

Very interesting to see what the cooler and Nismo pipes did. 450 RPM is massive!

[baicai]

So y can't u run more boost

Yeah the tuner did turn boost up to 20 psi for third run but only gained 2 kw at peak, although torque at mid-range did increase some, he was worried by reliability as my motor internals is still stock so dropped boost back down to 19 psi.

[baicai]

Not too sure how much bigger intake pipes are going to make when the smallest point of the whole system is the elbows that bolt onto the compressor housings. There is a mod you can do here. Either way, 400 kW on -5's and much more has been achieved with all the stock gear in place many times.

Get a decent sized exhaust on it. Twin 2.5's when you sit down and work it out isn't big at all. I'd say that would be external diameter too which makes things even worse.

Very interesting to see what the cooler and Nismo pipes did. 450 RPM is massive!

Hi Paul the exhaust is on my next to do list, being put it back due to budget and also a bit worried about how loud it might be, I think you've got twin 3" into 4" is that right?

I think the nismo intercooler hard pipes and the intercooler made the biggest difference. I'll try and post the dyno sheet so you can see the difference. But it's still not all good as I have poor torque below 4550 rpm which I hope the bigger exhaust will help.

[XGTRX]

It sounds like the symptoms of restriction. Just get a y pipe with a 3.5 inch collector and run a full 3.5inch straight through. More than enough for a stock motor running 5s. But I think I said that on page 1.

[Ben C34]

Isn't single 3.5 the same surface area as twin 2.5?

[XGTRX]

Not sure how the twins behave but 3.5 inch single has done the job many times over. Piggaz said they are restrictive so I assume they are.

Edited October 29, 2015 by XGTRX

[baicai]

It sounds like the symptoms of restriction. Just get a y pipe with a 3.5 inch collector and run a full 3.5inch straight through. More than enough for a stock motor running 5s. But I think I said that on page 1.

Hi mate yes you did, haven't forgot, just didn't have the $2k for the complete exhaust at the time, it is next thing I'll be getting. It does make sense as the tuner also said my exhaust was way too quiet so there must be restrictions.

[Ben C34]

Maths time.

Surface area = pi x r2

1.25x1.25 x pi =4.9 x 2 = 9.8

1.75x1.75 x pi = 9.6

2 2.5 pipes is slightly larger than one 3.5.

[XGTRX]

Well maybe the mufflers are stuffed. Would be good to drop the mufflers and see how much earlier the turbos come on.

[mr skidz]

Anyone check the wastegates arent cracking open to early which introduces a soft ramp up?

[Piggaz]

What's the smallest point of the exhaust? Jap exhausts are good for "step downs" before the mufflers.

[baicai]

What's the smallest point of the exhaust? Jap exhausts are good for "step downs" before the mufflers.

Didn't get a chance to measure when the exhaust was out, but from gtr forum UK, the size are 2 x 60mm from turbo, merge to 80mm after rear diff, and 100mm exit. So i guess it's 2 x 2.36" to 3.14" with 3.9" exit.

[baicai]

Anyone check the wastegates arent cracking open to early which introduces a soft ramp up?

Not really sure how to check, any suggestions?

[baicai]

Dyno graph, blue line was with dumps/cats, red line is intercooler+hard pipes. Still have torque hole below 4500rpm, I'm guessing it's the restriction in the exhaust?

[baicai]

dyno

[mr skidz]

Apart from lack of outright power Isn't that pretty std for -5's on a 2.6L they all seem torqueless under 4500rpm.

Its one of the reasons i went 2.8L.

Edited October 30, 2015 by mr skidz

[mr skidz]

Do you have std cams?

[XGTRX]

They should be coming on a bit earlier, interested to see your AFR as they come on, I would say you might be a bit rich as you come on boost hence the slight dip and delay.

Edited October 30, 2015 by XGTRX