Twin-cam 30 Is Driving Me Mental.

[cactus]

I'm becoming very frustrated with my current engine...

Basic rundown - its an RB30DET being an R33 S2 turbo head (completely stock).

The bottom end is built, with CP pistons, eagle rods etc. and a final CR of 8.9:1

It runs a GT35R internal gated exhaust housing, but running external. (.82)

It has all the supporting mods necessary, and runs an EMS stinger.

2.5" intake piping, 80mm TB, 3" dump and straight exhaust.

I run a built RE401A, KEAS full manual box, all upgraded internals, and a 4200RPM stall from MV.

This bucket of shit will not make any power. It's killing me. I have had it on a few dyno's to see what each person thinks, and no one can give me an answer. Yesterday, on a 'hub' dyno, it made an incredible 352rwhp @ 17psi. 16 degrees of timing all up. AFR's around 11.8 and peak power @ 7100rpm engine speed.

What the F#ck can I do? It's hard to say if it is lacking power because I am yet to take it down the strip. At one point, it managed to make 340rwhp @ 11psi but I think this was a relatively lean tune with heaps of timing.

I'm going insane. I am starting to think that maybe the auto isnt working with the combo. I know power figures are not everything, but this sort of power doesnt make any sense out of an GT35R fed RB30/25. I dont know what I am asking from you guys. I guess some suggestions/advice about anything really. I am lost.

[Dale FZ1]

Stock head with VVT?

Does the EMS operate VVT correctly?

I'd be expecting you could run a lot more timing than 16 degrees too - again making me think of your cam timing.

[cactus]

Stock head with VVT?

Does the EMS operate VVT correctly?

I'd be expecting you could run a lot more timing than 16 degrees too - again making me think of your cam timing.

One thing we do have to fix is the VVT. Electronically, its not working. Hopefully it's an issue with the wiring rather than the ECU. The EMS is supposed to be able to run it.

[scotty nm35]

I was told by Kewish, the higher the stall the less power transfered to the wheels but you are missing a huge amount.

[James_03]

Cam gears dialed in correctly?

If I had to stab in the dark, I would maybe say something timing related. I was out one tooth on intake before a run once, totally different power outcome.

Just a suggestion, everything else looks OK mod wise. I woulnd't think the auto would pose any issues.

[Messiah]

dyno it and compare runs with the vvt plugged and unplugged. If they're the same, then you know you have a vvt problem.

[James_03]

vvt issue aside but, it's still missing too much power.

[TiTAN]

do you have a dyno run you can put up?

[cactus]

do you have a dyno run you can put up?

Pretty sure the timing belt is set-up right. All marks match up correctly and the engine has been running for about 5000kms. Well, the white dot on the passnger side cam gear is slightly off-line from the mark on the back cover, but definitely not one tooth out...

I can probably get a dyno sheet up at some point if you think it would be worth it? Will have to ask the guy that tuned it to send one through to me first.

Yeah... it is missing a stupid amount of power. Yeah the auto sucks a bit, but I thought it would still make around 400rwhp on a normal dyno.

[Dale FZ1]

Running stock exhaust manifold I'd think you'll pull around 430ish hp on that boost when things are right.

If the VVT isn't working, that's the main source of problems. Don't look any further until it does work.

Then you should be looking to be able to run more ignition timing.

Both of those things will stop you making a bucketload of power.

Edited March 24, 2010 by Dale FZ1

[cactus]

Running stock exhaust manifold I'd think you'll pull around 430ish hp on that boost when things are right.

If the VVT isn't working, that's the main source of problems. Don't look any further until it does work.

Then you should be looking to be able to run more ignition timing.

Both of those things will stop you making a bucketload of power.

OK. Will make efforts to suss that out then.

Running a 6-Boost too so plenty of flow there

[Crans]

VCT not working should effect the top end power figure. Why is the timing on boost so low?

[cactus]

I didn't realise it was that low? What should it be around?

Also... does anyone know if the exhaust housing of the turbo, being an internally gated turbo (with port now just blocked off as I am running external) would be a significant restriction, and whether it would be worthwhile replacing the housing for a proper external gate one?

I dont want to spend $700 on a housing for little gain.

Edited March 24, 2010 by cactus

[STATUS]

VCT wont make any difference to top end, unless its powered up all the time.

I would run it up with the std converter, but only after scoping the timing on the balancer and comparing it to the figures the EMS is "thinking" it is using. What ems is it? some are pretty crude in regards to map resolution under boost (no scaling adjustment).

[Messiah]

VCT wont make any difference to top end, unless its powered up all the time.

I would run it up with the std converter, but only after scoping the timing on the balancer and comparing it to the figures the EMS is "thinking" it is using. What ems is it? some are pretty crude in regards to map resolution under boost (no scaling adjustment).

Hey status, a question to clarify my understanding, not to question yours at all....

VCT changes the duration so that the intake valve opens/closes later when enabled right?? and is only enabled in the top end.

wouldnt this result in big loss's in power up high.

I think thats one of the things i had shown to me recently but i might be confused.

s15 doing 200kw with vct enabled, dropped to 150 without (might have been as high as 170 my memory is foggy).

which bit am i getting wrong??

[STATUS]

Hey status, a question to clarify my understanding, not to question yours at all....

VCT changes the duration so that the intake valve opens/closes later when enabled right?? and is only enabled in the top end.

wouldnt this result in big loss's in power up high.

I think thats one of the things i had shown to me recently but i might be confused.

s15 doing 200kw with vct enabled, dropped to 150 without (might have been as high as 170 my memory is foggy).

which bit am i getting wrong??

NVCS is OFF from 0 - 1050rpm, then ON until 4700rpm, then OFF again until redline.

Therefore the NVCS advances cam from 1050 until 4700rpm then it switches off allowing "normal" cam timing.

If the vct was wired up to be engaged all the time it would be advanced from 0rpm to redline... this would affect power, hence my first post.

If left disconnected top end power will not be effected only power to 4700rpm

[cactus]

It's an EMS Stinger... the baby one.

The timing on the computer is the same as what it is up front. Initially, this wasnt the case. It was 20 degrees at the computer and 25 degrees up front. But they adjusted this yesterday. Damn, I was getting my hopes up thinking the VCT could make a big difference to the output.

Are there any issues associated with running it from 0 - 7000RPM?

Edited March 24, 2010 by cactus

[STATUS]

It's an EMS Stinger... the baby one.

The timing on the computer is the same as what it is up front. Initially, this wasnt the case. It was 20 degrees at the computer and 25 degrees up front. But they adjusted this yesterday. Damn, I was getting my hopes up thinking the VCT could make a big difference to the output.

Are there any issues associated with running it from 0 - 7000RPM?

yeah if anything on all the time is far more detrimental to off all the time.

[Harey]

Yeah would be great to see a dyno sheet to see what the curve looks like. You can normally see converter slip on a dyno.

[hypergear]

Is that a Ebay GT35R you are using? wort sort of spec is on the turbo? have photos of both wheels and dyno reading?