R33 Gtst Rb25Det Hitting Power Ceiling

[Michael's R33]

Hi guys if anyone can shed some light it will be greatly appreciated.

Firstly the car is a r33 gtst rb25det

Mods

Hypergear highflow (r34 op6)

660cc injectors

040 pump

Power fc

3 inch from turbo back

Return flow cooler

Splitfires

The problem:

Basically the car has been in and out of unigroup engineering when it was first put together it made 247kw at 15psi

Had a small manifold leak so they could not push it more since fixing that and going to push more boost through it, it now only makes 220kw at 20psi but the power drops off early around 5000 rpm they suspected a restriction in exhaust or a boost leak as they retard timing to compensate for more boost but the car wont react as in the timing is not changing.

Car is hitting the dyno again tomorrow with another cas just to rule that out but cant seem to pin point the problem.

Sorry again for the essay

Thanks michael

[Badgaz]

How do they know the timing is not changing?

[Michael's R33]

Because as they add more boost the car creates less power

[hypergear]

There are two types of OP6 high flow. Most of the recently once made this year has the updated compressor and turbine whiles which is capable of making a lot more power. The older versions usually stops making power towards the 260rwkws mark, which your first dyno run sort of makes more sense.

Getting the most out of the turbocharger, 3 inches metal induction with a good pod is a must, as well as a proper cooler and free flow exhaust.

[Badgaz]

Because as they add more boost the car creates less power

sorry i'm a bit confused...on WOT they will set timing in the load areas of the map....the ecu won't change the timing unless they are hitting a water temperature threshold. so they up the boost and you aren't getting anymore power...do you have your dyno graph? that could show a bit more. mine made 229kw with a high flow but just made no more power when we added more boost.....(we really tried)

[Michael's R33]

I got a hard pipe on the front bolted to z32 and 3inch turbo back no cat no mufflers just 4inch outlet cannon

Ill get the graph tonight and post up.

[Badgaz]

if the graph has your afr's that'll be good too.

[Dose Pipe Sutututu]

whilst you're changing your CAS, might as well pop off the cam belt cover and see if your CAM gears line up properly to all the markings vs. your crank

[Super Drager]

Yep as above, check cam timing, try a new CAS and maybe drop the exhaust from the cat.

[Michael's R33]

I told em yesterday to drop the exhaust but was pretty late at night so ill check cam timing and put new cas in while im there tonight

[Michael's R33]

ok so car got changed but could not perform a dyno run but i do have a power run while the car had the issue

[simpletool]

Hmmm...here's my 2 cents.

The curve looks worse than it is due to the scale.

1. There is a big boost drop as revs rise. At 6000 to 6200rpm it is running 15-16psi. That is entirely consistent with the power level achieved. So I'd first be looking at tension on the wastegate spring. If it's adjustable I'd add 2 turns and see the result. It looks like electronic control - is the GAIN set too high?

2. I don't know the turbine/compressor size but I'm pretty sure they're not large enough to warrant a 4000rpm boost threshold. I'd mention to the tuner that they investigate the AFRs around boost threshold (and knowing at least a tiny bit about how SAU tune they'll need to richen it up a bit coming onto boost, preferably for 800rpm before too).

#1 should fix most of your power issue

#2 should fix the drivability - which is AT LEAST as important.

I'm not saying there aren't other issues going on but it doesn't look too bad considering the boost drop.

Other things to check:

1 - Is the VCT set correctly? Is it ON between approximately 1200 and 4800rpm ?

2 - Is it too lean in places? Better to err on the side of rich rather than lean.

Edited May 26, 2014 by simpletool