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Chasing 350-400rwhp, But With Much Less Lag. Advice Please?

SoFreshSoClean

By SoFreshSoClean,
in Engines & Forced Induction

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SoFreshSoClean Proficient

SoFreshSoClean

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Some developments:

Got a workshop to take a quick look at the car, they chucked it on a dyno briefly. Turns out that it's an internally gated turbo with the gate welded and routed to an external gate. They blocked off the wastegate so that theoretically the turbo should have boosted until something blew up but it had no effect whatsoever!! Something is screwed up, I'm going to get the whole setup looked at.

My friend also spotted a small rubber blockoff coming off the turbo which had broken. We put a new one on and it's now boosting a few hundred RPM earlier which is nice.

Also did a bit of road testing, the car is showing positive manifold pressure as low as 2800rpm, but only 1 or 2 psi.

I'm going to get the air filter relocated back under the bonnet, its gets wet being where it is.

  • 4 weeks later...
SoFreshSoClean Proficient

SoFreshSoClean

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Found out the turbo is a KKR480 (or at least a copy of one), my tuner reckons that its pretty hard to get much more out of the current setup. So once I sell my old car, the series II is going in for a new turbo. I've since had the AFM/pod moved up into the engine bay (so now the tune is screwed as well :) ). He is pushing me towards a GT35 with the 0.63 housing, but I'm not convinced. I dont plan on rebuilding the engine so I would rather have a smaller turbo with less lag being pushed a bit harder. I will also be getting all the stupid blue silicon hoses replaced with proper stainless pipes, and I'll be getting a catch can put in.

STATUS Grand Master

STATUS

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Found out the turbo is a KKR480 (or at least a copy of one), my tuner reckons that its pretty hard to get much more out of the current setup. So once I sell my old car, the series II is going in for a new turbo. I've since had the AFM/pod moved up into the engine bay (so now the tune is screwed as well ;) ). He is pushing me towards a GT35 with the 0.63 housing, but I'm not convinced. I dont plan on rebuilding the engine so I would rather have a smaller turbo with less lag being pushed a bit harder. I will also be getting all the stupid blue silicon hoses replaced with proper stainless pipes, and I'll be getting a catch can put in.

:)

TiTAN Grand Master

TiTAN

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you are taking a turbo capable of 400kw and putting a restrictive rear housing on it that makes it struggle to make 350kw and is laggy compared to a 3076 which makes a tad less power with lots more response.

Harey Veteran

Harey

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Posted (edited)
Also did a bit of road testing, the car is showing positive manifold pressure as low as 2800rpm, but only 1 or 2 psi.

If the car is seeing positive boost pressure at 2800rpm and the turbo will not boost any higher I think you have other issues. Its a pity the performance place couldnt help identify anything. The turbo could be fine, sure a GT3076R would be better but doesnt mean the turbo on there cant work well. Would suck to buy a new turbo and then find out the issue is still there. Although I cant say what tests to run, hopefully some other people on here can help with that.

Hmmm so its got to be something that restricts the turbo as it spools up but still allows it to get to a nice peak power. hmm

Yup -1 for the GT35R with 0.63 housing, dont do it.

Edited by Harey
SoFreshSoClean Proficient

SoFreshSoClean

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you are taking a turbo capable of 400kw and putting a restrictive rear housing on it that makes it struggle to make 350kw and is laggy compared to a 3076 which makes a tad less power with lots more response.

Thanks for that, I'm probably asking stupid questions haha. I wasnt keen on a GT35 in the first place

If the car is seeing positive boost pressure at 2800rpm and the turbo will not boost any higher I think you have other issues. Its a pity the performance place couldnt help identify anything. The turbo could be fine, sure a GT3076R would be better but doesnt mean the turbo on there cant work well. Would suck to buy a new turbo and then find out the issue is still there. Although I cant say what tests to run, hopefully some other people on here can help with that.

Hmmm so its got to be something that restricts the turbo as it spools up but still allows it to get to a nice peak power. hmm

Yup -1 for the GT35R with 0.63 housing, dont do it.

The mechanic said he's fitted several KKR480's, all with much the same result as me, although I had a slightly better top end which he said was probably due to the aftermarket plenum. I would rather sell the turbo on it and start again with something better (I am not really out of pocket as I bought the car with this setup on it).

Marlin Grand Master

Marlin

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I've just read the entire thread, and it sounds like you obviously purchased the car as is.

Have you by any chance checked the exhaust system thoroughly? Is there a shitty compliance cat in there? Has the cat begun to melt? Has a muffler collapsed?

What I'm highlighting is significant exhauist system restrictions can easily cause you issues.

SoFreshSoClean Proficient

SoFreshSoClean

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Nah, it has an xforce 3 inch turbo back, and the cat was replaced with a high-flow 4 inch item just before the turbo was put in. It used to be my workmates car, so I have at least some idea of whats gone on with it in the past.

Harey Veteran

Harey

Posted
Posted
I've just read the entire thread, and it sounds like you obviously purchased the car as is.

Have you by any chance checked the exhaust system thoroughly? Is there a shitty compliance cat in there? Has the cat begun to melt? Has a muffler collapsed?

What I'm highlighting is significant exhauist system restrictions can easily cause you issues.

Would an exhaust restriction cause it to hit positive boost pretty quickly, but then boost slowly and still make a good peak power figure?

bozodos Grand Master

bozodos

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hehe my xforce 'high flow' cat filled up with crap and sort of fused itself towards one end of the shell due to my Microtech not running an 02 sensor and running excessively rich, it would probably be worth checking out to eliminate the possibility, especially if the car's had a really crappy tune at some point.

l0WRB Mentor

l0WRB

Posted
Posted

Im running gt3076r with 50mm gate on stock manifold on 19psi and making 390rwhp

fullbboost at 4100rpm and pulls to redline

u can pickup a new gt3076r for around $1495 from garrett

joeyjoejoejuniorshabadoo Grand Master

joeyjoejoejuniorshabadoo

Posted
Posted

drop the exhaust and see if the restriction is there... your tuner probably should have suggested this.

I run a hks 2835 (garrett 3071 based turbo) and see 20psi by 3400 revs and make 390rwhp (432rwhp on e85)

a 3071 /3076 is what you are after... (but either way a 30xx turbine housing)

anyone suggesting a GT35xx turbine for someone after response and sub 300rwkw on an unopened RB25 has no idea / or a good deal on a gt35xx that they want to flog

i'd reccomend a new tuner

Marlin Grand Master

Marlin

Posted
Posted
Would an exhaust restriction cause it to hit positive boost pretty quickly, but then boost slowly and still make a good peak power figure?

Difficult to promise a yes answer as there's lots of levels of "restriction", but as a whole I would definately say yes.

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