T78 Rb25Det

[r31 25t]

I have a t78-33d 17cm on a rb25det and would like to get an idea of the expected power output.

It's currently putting out 280rwkw at 18-19psi on a roller dyno. I thought it would be much more, at least 300-350??

Anyway, specs are as follows.

T78

rb25 highflowed injectors

stainless highmount exhaust manifold

50mm hks copy wastegate. (not plumbed in)

3" exhaust

link g3 ecu

stock inlet manifold

2.5" intercooler piping

china FMIC

stock rb25det block with stock rb25de head

stock nissan headgasket

oil cooler

AFR's on boost are around 11.5 with 10* timing up top.

I will get the dyno sheets and post them up soon.

Thanks in advance.

[zebra]

Bigger exhaust, more boost will get you there

[r31 25t]

Yea I think so, maybe a 4" exhaust and 22psi.

The engine is just a slapper with parts we had lying around.

From memory the torque drops off pretty hard after peak @ about 5.5k, like there is a great restriction. I thought with the big turbo the torque should be able to hold a bit longer than it does. It won't take much timing though (probably another sign of a restriction) or maybe the DE head has raised the CR to much. -switch it to E85?

Edited November 12, 2011 by r31 25t

[zebra]

there are plenty of results from the US of 1J's making well over 600rwhp with the same turbo and E85 up around 30psi.

From memory they all had 4" exhausts and aftermarket cams though

[ARTZ]

I'd be looking at a better cooler with 3 inch pipe as well exhaust..

[zebra]

This should give you an idea, stock internal 1JZ with 264 cams...this car hasn't backed it up on the strip so i'm not sure how genuine those 640 horses are (dynojet reads a bit higher than a Dyno Dynamics dyno) at 24psi...but should be high 500's out here on a DD roller

Edit to add - 1JZs have smaller ports and half a point less compression than an Rb25det and tend to need a couple more psi in the intake to make the same power using the same turbo.

So I would think that 600hp is there for the taking with a big (4") exhaust a good cooler and a good tuner on E85

[r31 25t]

I've seen that video before, and there is a write up on the car here supra t78.

The intercooler and exhaust piping sizes are the same as mine according to the posts on the above forum link, but like you say its being run on a dynojet.

Also running the wastegate plumbed out is effectively like having a bigger exhaust so that should help a little?

I may of found the problem, on a closer review of the dyno sheets I've noticed the there is some slippage when the turbo ramps onto boost, whether it's the tyres or the clutch, I'm not sure. - This is probably where the power is being lost, the engine maybe making an extra 20kw of smoke from the clutch or tyres. I'll have to pay more attention next time it's on the rollers.

I'm off to the shed, so will get those sheets posted up today. - no laughing please!! this may be the most inefficient way to make 280kw.

[koe]

Change the piping to 3"

Use a larger intercooler

Get rid of the bov

Use a good one

A twin scroll type turbo manifold

Yes 100mm is a good idea if you can flow power

I'm running a rb25 t78-33d with 270-272 camshaft set up

I'm at 400hp at 10psi 100mm straight pipe with a vibrant 100mm muffler port and polish etc.

Been running for 3yrs + no problems

If you have any question just pm me

[r31 25t]

Power and torque are in kw and nm and I can't remember how I scaled the knock.

KW NM AFR

KW NM MAP

KW NM Knock

I'm still working the bugs out on the dyno too which doesn't help much.

I put a tilton triple in it the car today and it feels way more savage to drive.

Didn't get enough time to put it on the dyno though so not sure if it's transferring more power.

Any way don't laugh to hard.

[Rolls]

Yea I think so, maybe a 4" exhaust and 22psi.

The engine is just a slapper with parts we had lying around.

From memory the torque drops off pretty hard after peak @ about 5.5k, like there is a great restriction. I thought with the big turbo the torque should be able to hold a bit longer than it does. It won't take much timing though (probably another sign of a restriction) or maybe the DE head has raised the CR to much. -switch it to E85?

Why only 22psi? Just keep screwing more in until it stops making power or you run into detonation issues.

[Dose Pipe Sutututu]

What duration cams are you running?

[Harey]

Why only 22psi? Just keep screwing more in until it stops making power or you run into detonation issues.

I know what your saying but if the torque is falling away that much with such a large turbo then surely something is restricting things. Would be worth pumping up the boost to see if it overcomes the issue or it gets worse as a test.

[Rolls]

I know what your saying but if the torque is falling away that much with such a large turbo then surely something is restricting things. Would be worth pumping up the boost to see if it overcomes the issue or it gets worse as a test.

Yeah fix the problems first, I just thought that was your goal once it was all running properly.

[GTScotT]

Firstly I applaud your efforts and your attitude mate, good on you for trying to nut this out.

My question is: Is the manifold twin or single scroll and is the turbine housing twin or single scroll?

I have found poorly matched flanges to the head/turbo/dumps/cats ETC ETC to cause enormous restrictions like what you are seeing. It is a lot of flow and a little bit of turbulence would be exponentially worse for its power making ability as the flow climbs.

Check this out and make sure everything is nicely matching up. See if your manifold has carbon deposits on the flanges indicating a poor flow path ETC.

Also, and perhaps more importantly, I have come across another RB slapper recently that had the exhaust cam out by 1 tooth... It just did not want to make the same power it did before because it was ingesting exhaust gas once the boost came on and killing off its spark ability. Make sure the cams you are running are in spect with the belt/camgears you are using and its all timed up 100%

[zebra]

all the td07 and larger turbos are twinscroll t4

[simpletool]

1. Exhaust not flowing enough.

[r31 25t]

Why only 22psi? Just keep screwing more in until it stops making power or you run into detonation issues.

The main reason is the G3's internal map sensor is only limited to around that boost and I'm to tight/lazy to buy another one and wire it in, and to be honest it should be more, the numbers are indicating a problem.

johnnilicte[/color]' date='14 November 2011 - 11:35am' post='1735291']

What duration cams are you running?

Factory r33 rb25de cylinder head and camshafts I=240* E=240* 7.8mm lift Same cams as the rb25det according to the tomei website.

I think the head has bumped the CR up a bit - needs to be tested.

GTScotT[/color]' date='14 November 2011 - 04:19pm' post='1735291']

Firstly I applaud your efforts and your attitude mate, good on you for trying to nut this out.

My question is: Is the manifold twin or single scroll and is the turbine housing twin or single scroll?

I have found poorly matched flanges to the head/turbo/dumps/cats ETC ETC to cause enormous restrictions like what you are seeing. It is a lot of flow and a little bit of turbulence would be exponentially worse for its power making ability as the flow climbs.

Check this out and make sure everything is nicely matching up. See if your manifold has carbon deposits on the flanges indicating a poor flow path ETC.

Also, and perhaps more importantly, I have come across another RB slapper recently that had the exhaust cam out by 1 tooth... It just did not want to make the same power it did before because it was ingesting exhaust gas once the boost came on and killing off its spark ability. Make sure the cams you are running are in spect with the belt/camgears you are using and its all timed up 100%

Thanks mate.

The manifold is definitely a twinscroll, not to sure how well it lines up with the turbo flange, will have to check that to.

Timing is spot on.

I think all going to plan, I'll have it back on the rollers next saturday with a dump pipe only. - It's gunna be loud, but hopefully it makes the numbers.

[zebra]

definitely keen to see how it goes, just sold my t78-33d without even running it on the car lol

[koe]

Twin scroll with be best.

I run a single scroll equal length love fab turbo header with a tial 60mm wg.

Spool test was at .7 bar no boost controller.

Results was:

5 psi at 3,200 rpm

10 psi at 4,300 rpm

Which was fool boost

We set our rev limit to 5,000 rpm

Which was hitting rev limit at 4,800rpm

You can check out Kelford camshafts

They use a lower lift but the same duration as my tomei.

Mine is 10.25 both camshafts

They do help spool

[On Edge]

China FMIC