Project Rb31dett. The Development Of My Open Deck Rb Engine And The Quest For More Torque!

[Roy]

The stock cooler maxis out at 380kw

What is the issue, temperature drop or pressure drop?

[GTRNUR]

I didn't realise you had to chop up the car to get the GTX's to fit. Pass on those then... I'd rather chop up an engine than a car.

I definatly want more power than -5's can produce, at least on an un-cammed and un-ported head... 2 points that are definatly holding back the current engine.

Shuffle isn't really an issue for me when street driving, as I don't floor it in 5th or 6th gear at 4000-5000 RPM in order to get up and moving. Its always drop back to 3rd or 4th. In order to have a shuffle issue that would affect drivability and power delivery, I would need to be doing 160km/h in 5th or around 200 in 6th. Which is one gear too high for those road speeds.

[Piggaz]

When I say chop up the car I meant not OEM intake piping. Thats a shame as it's nice to have it looking all standard!

[Weapon]

I'm not sure if its the case with the 28 series Garrett's but do you buy these things then have to pay additional money for your rear housing seperately?

When I was tossing up going the Precision Billet 6262 or the GTX when I got the GTX priced up it was $2499 + $599 for the .82 rear housing.... that was through the MTQ branch here and thats not even the Tial rear housing....

Is that the same scenario with all GTX's or just the GT30 upward range of GTX's?

[Piggaz]

I believe thats the case yes. Gav didnt get rear housing with his set.

[Piggaz]

The thing I don't get Ian is this. You're after 'more torque' which means a curve which has more area. Now the GTR engine/2.6L lacks grunt south of 4000 - 4500 RPM, Yet you're using a turbo which is proven over and over again that simply does not work in that area.

In my own experience I have picked up 100 RWKW at 4500 RPM. That means more torque yes?

After being there and used them, I couldnt care what capacity I have behind them I wouldn't use them.

You say you want more power than the -5's can produce... What is their upper limit? I was at 425RWKW with cam timing with hurt its top end. A simple twist of the intake cam would reel off 450. Thats at 24 peak tapering down to 22 psi topend. (although its on E85, however its a super safe tune)

For you to make 303 at 18 psi on RS's there must be a serious serious restriction somewhere. It aint the airbox. Exhaust? Possibly, but wouldn't be the full cause of it.

[GTRNUR]

The thing I don't get Ian is this. You're after 'more torque' which means a curve which has more area. Now the GTR engine/2.6L lacks grunt south of 4000 - 4500 RPM, Yet you're using a turbo which is proven over and over again that simply does not work in that area.

In my own experience I have picked up 100 RWKW at 4500 RPM. That means more torque yes?

After being there and used them, I couldnt care what capacity I have behind them I wouldn't use them.

You say you want more power than the -5's can produce... What is their upper limit? I was at 425RWKW with cam timing with hurt its top end. A simple twist of the intake cam would reel off 450. Thats at 24 peak tapering down to 22 psi topend. (although its on E85, however its a super safe tune)

For you to make 303 at 18 psi on RS's there must be a serious serious restriction somewhere. It aint the airbox. Exhaust? Possibly, but wouldn't be the full cause of it.

Every setup has a compromise of some sort. I wanted the stock appearence and to be able to make power more easily in top end without having a ported head or cams. The GTRS shuffle issue wasn't something knew even existed, having had no GTRS/RB experience before starting this project. We can only learn from our mistakes and I'm down a specific road now and I need to get to the end of it before I can see how good the journey really is.

Cam timing will go a long way to sorting out the restiction issues. This is an area we have yet to play with having started a 0/0 again in this most recent tune session. Cams will be the focus of one of the next dyno sessions. My window of time for tuning is pretty narrow, as I am having to do all this after hours and only generally get about 1.5 hrs of usable light before it gets too dark where the dyno is to be able to make any fine adjustments. Especially without burning myself on the radiator (Im sporting a few good blisters from 2 weeks ago still).

The greddy extension front pipe setup and un ported head will also be holding it back a bit.

Yes -5's could solve a few issues and make better low end at the expense of some (easy) top end. But its pointless changing them now without first trying to optimise what I already have. So NO. No dash 5's!

Shuffle is only an issue if your driving in the wrong gear. 150-200km/h is a 4th gear speed, not a 5th gear speed. It drives through the shuffle zone (4-5) a lot quicker on the street in the lower gears than it can on the dyno. Street driving has the advantage of having inertia energy in the spinning turbine shafts, which helps help get through the shuffle zone quicker too. On the dyno this isn't the case when gently driving the car up to full load. If driving enthusiastically and shifting at 7, the next gear starts at 5 ish which is still above the shuffle zone too.

So what I am saying is my shuffle issue really is only a problem when holding load points on the dyno. I have a feeling that more boost I run the less of an issue the shuffle will be. More boost will also bring the curve further forward as the wastegates won't be bleeding off as early, and build more inertia in the turbo's quicker.

The torque curve on the high boost run is a bad example to draw any comparisons to, as the boost response is slower than it is on the street becuase of the reduced ramp rate. The low boost run is a better example of what the boost/torque response curve is like, despite the shuffle dip. The only conclusions that can be drawn from the high boost dyno sheet is that the engine is making the same power that it did 6 months ago with the same cam timing, and that last weeks ignition issues are fixed.

[Marko R1]

As I've quoted more than a few times, shuffle was never an issue on my rb2630 with gtrs's. On my rb26 it is much more apparent but this is due to the vipec tune + my cams are also on 0 degrees.

I think with further tuning ian, you will be happy as gtrs's seem to run efficiently when making 230kw per turbo hence also taking you to your target 450kw

[Rolls]

love all the detail you go into in this thread, top read.

[X-Modcarz]

_{Great project, well written thread, very much appreciate the time you have taken to explain everything.}

_{Any more updates?}

_{Version 3 updates?}

[GTRNUR]

Not much new to report really.

I've been playing with cam timing a little and have found the motor responds very well to more lobe seperation as well as much more advance on the exhaust cam. It feels like the gtrs shuffle issue is nearly completely eliminated.

Cam timing changes have moved the low end torque up a little further and reduced fuel economy a little (8.75/100km now), but the torque band is a lot wider and doesn't drop as sharply after 6500 rpm. It also lowered EGT's significantly and has improved the accuracy of the wideband readings as a result. The reading at the dump is now a lot closer to the reading at the end of the pipe.

There is nearly 18,000km on engine now so it has proven itself to be reliable. More dyno time is in the pipe line when Im back home and have the time for it. Im building another engine at the moment too which is pretty much entirely custom (not an RB), and thats absorbing all my spare time.

Yes a version 3 is next, and all the design work is finished. It will be a very different engine to this one, as the block is converted to a wet sleeve setup. It will be able to support a 90x90 bore/stroke making 3.4lt. It will be a 23mm spacer plate which will still fit with no radical modifications to the car. The first variation will be 89x90, Nitto internals, ported head with a set of step 1 springs and some 260/10mm cams and most likely a pair of GTX28's.

[r33_racer]

90mm bore. that is really pushing it in terms of wall thickness. If you run a 3mm wall, all the bores will be touching or close enough to it. Is that roughly what you have worked out?

[Boss-zilla]

*snip* Im building another engine at the moment too which is pretty much entirely custom (not an RB), and thats absorbing all my spare time.

*snip*

The VW? It was you that has that awsome beetle too or am i thinking of someone else?

[GTRNUR]

90mm bore. that is really pushing it in terms of wall thickness. If you run a 3mm wall, all the bores will be touching or close enough to it. Is that roughly what you have worked out?

Yes the sleeves are a touch over 3mm at their thinnest, which is 0.5mm thicker than the cast in cylinders are in a normal block (at their thinnest). The version 3 design has keyed sleeves like an OS engine. At their thickest they are 5mm. It shares a few similarities with how the modular deck works on a 4B11T evo X engine, excepted that the RB26 still needs a spacer to pull this off.

The VW? It was you that has that awsome beetle too or am i thinking of someone else?

Its the bug. The new motor is now 2.7lt twin turbo. I've upped the compression and changed to nickel-silicon-carbide cylinders, Should be interesting with the twin t517z's on it. Aiming for a startup next weekend.

I managed to destroy the clutch in the gtr on the way back from Proserpine today. The clutch doesn't hold at all with the revs over 4500 anymore. Im looking at an exedy competition D twin plate clutch as an alternative to a nismo twim plate at the moment. They are lighter, which will allow me to get some better response down low without losing as much torque fighting intertia in the flywheel.

[Piggaz]

How many kms was on the Nismo twin? Was it a coppermix? Was it the competition model?

[GTRNUR]

It was a Nismo gmax red cover which I believe is an early competition model version or some sort of higher power model. It was new when the engine went in about 18,000km ago.

Its never been right from the start though, so Im not too concerned. On first startup I couldnt get it to dis-engage and had to alter the slave cylinder piston size to get more throw.

I didn't install the clutch myself. It was put in by the mechanics that fitted the engine for me, so they may have done something wrong. Maybe a disc is in backwards perhaps... Or the clutch could have been a dud too. Such is cars...

[wedge_r34gtr]

Huge fan of this build look foward to seeing phase 3.

I managed to destroy the clutch in the gtr on the way back from Proserpine today. The clutch doesn't hold at all with the revs over 4500 anymore. Im looking at an exedy competition D twin plate clutch as an alternative to a nismo twim plate at the moment. They are lighter, which will allow me to get some better response down low without losing as much torque fighting intertia in the flywheel.

Did you consider the carbon D clutch? or have you thought about giving Jim Berry a ring to see if he can do something with the current clutch?

[GTRNUR]

I have investigated the carbon clutches. Some the GTR UK forum guys love them. They slip a little when cold aparently which makes them streetable, but the down side is when really taxed the head has caused some of the components to weld. Same for the ATS carbon clutches.

Pass on having it rebuilt. I wasn't overly happy with the pedal feel anyway compared to other nismo/exeedy's ive driven .Time for something new and improved!

[Marko R1]

I managed to destroy the clutch in the gtr on the way back from Proserpine today. The clutch doesn't hold at all with the revs over 4500 anymore. Im looking at an exedy competition D twin plate clutch as an alternative to a nismo twim plate at the moment. They are lighter, which will allow me to get some better response down low without losing as much torque fighting intertia in the flywheel.

I strongly advise against the exedy comp D as I had one in my car and took it out not long after, that thing was harder to drive than my os giken triple plate...terrible.

I've had 2 jim Berry's and they honestly drive like a factory clutch. Paul diemar had it in his drag car for 3 years which was a 9 sec car and now that is still running in another car - snuff said

[wedge_r34gtr]

Pass on having it rebuilt. I wasn't overly happy with the pedal feel anyway compared to other nismo/exeedy's ive driven .Time for something new and improved!

Sounds good!! lol...a phone call to Jim may be worth while either way - he likes to talk clutchs and he may be able to offer some advice on what caused the faliure or your proposed selection.

I have investigated the carbon clutches. Some the GTR UK forum guys love them. They slip a little when cold aparently which makes them streetable, but the down side is when really taxed the head has caused some of the components to weld. Same for the ATS carbon clutches.

The drivability was why i made the suggestion - i hadn't heard about the welding issue (bit worried about mine now )

Edited June 8, 2012 by wedge_r34gtr