Rb30 Power Delivery, Should It Be Better? How?

[DennisRB30]

yeh yeh i know. Still i think final power figure was something like 370rwkws with it which isnt too bad for a little gt30r. Im hoping we will see 400rwkws with it. Only difference with this new motor is argo rods, dry sump system, and the gt35r. When time permits a 4" exhaust system for it too to replace the damaged 3"...got crushed when running off the track. However im not sure if the 3" was being a restriction at that power level or not.

All the XR6 guys will agree that 3" is too small on thier cars with the stock GT35 that comes on the XR6. They all get good power gains by going to 3.5" preferably 4" exhausts. I have a 3.5" dump and the rest is 3.1" which I think will limit my power with this turbo.

[discopotato03]

Actually it was a GT3040R or as they are called nowdays GT3082R - exhaust side of GT30R with compressor section of a GT3582R .

I've got 2c to spend but my thoughts are based on other peoples experiences not my own .

Firstly reliable sources have proven that R33 RB25 DET heads/cams are already a bit lacking for 2.5 litres let alone 3 litres . Putting more cubic inches under these heads means port velocities are going to be higher at same crank revs or same when the larger one is at lower revs . It seems these heads are lacking exhaust port/valve flow expressed as a ratio to inlet port/valve flow . If they are limited on the exhaust side nothing you do to the inlet side will make any significant difference because its not the major restriction . Pumping losses mean power losses and reversion lowers the detonation threshold to the point where retarding the ignition timing (to save your pistons etc) kills off power production .

The known methods of oncorking the top end are porting/maybe slightly larger exhaust valves , and better cam profiles . Slotting in a better direct fit exhaust cam would most likely wake it up but good results would also rely on the exhaust manifold / dump / cat / pipe and mufflers having adequate flow capacity . Actually before changing anything I'd be measuring exhaust manifold pressure just upstream of the turbo and comparing it to boost air pressure (at the compressor outlet) . Tapping into the exhaust here is the go because its the location where all of the engines exhaust gasses are collected and ducted into the exhaust housings inlet . Measuring air pressure at the compressor housings outlet is best because it takes into account any flow losses in the ducting/intercooler/throttlebody/inlet manifold etc . Losses in this area mean the turbo (turbine) is working harder to overcome flow losses and helping to create restriction on the exhaust side . My best guess is porting esp exhaust side and mild cams .

It would be interesting to know what tuning strategies your tuner uses for off boost lower rev conditions ie adequate advance and clean mixtures . Also fuel octane ?

Another thing that often gets overlooked is maximum boost vs maximum revs . You may find that dropping the boost a bit will allow the maximum revs to climb a bit , the lower boost pressure (and exhaust manifold or backpressure) means more revs for the same port velocities and maybe a little more advance with the lower max boost .

Food for thought and 2c gone , cheers A .

[r33_racer]

but the xr6 guys run a 4 litre engine...not 3 litre...so they automatically have more exhaust gas flowing all throughout the rev range.

So disco once ive deciphered all that...your basically saying that the head is too small in valve and flow size to suit the extra capacity. Thats where all the problems are coming from or at least originating from and possibly being exaccerbated by other restrictions in manifolding, exhausts and so on.

I think SK said something about this at one stage last year...the exhaust side was a little undersize for the 3l...however it was only by something like 17% i think...maybe someone else remembers. I guess it is playing havoc at all power levels both high and low.

[DennisRB30]

but the xr6 guys run a 4 litre engine...not 3 litre...so they automatically have more exhaust gas flowing all throughout the rev range.

Not as easy as that. A 4 litre running say 350rwkw is going to have a similar amount of exhaust gas as a smaller engine running 350rwkw. The smaller engine may need more boost and revs. But over all exhaust gas flow will be similar. The 4 liter might make 350rwkw @ 5500rpm on 17psi but the 3 liter might make the 350rwkw at 7000rpm at 23psi. The overall turbo size will be more reflective of how much potential exhaust flow an engine will require than the actual size of the engine.

[Cubes]

Disco,

I'm came to my conclusion due to what I have seen with my very own eyes back to back..

Mr 1.. RB30DET stock exhaust manifold, stock plenum/runners, gt35r .82 and ran with stock cams then with Tomei 260 duration 9mm.

Mr 2.. RB30DET stock exhaust manifold, stock plenum/runners and later dropped a short runner plenum on it.

So essentially the setups are as identical as one could hope.

Initially Mr 1 ran with stock cams, fiddled with cam timing and power still peaked early then nosed over.

Mr 1 decided it must be cams so he dropped a set of Tomei 260dur 9mm cams in it. Power STILL peaked at the same rpm as the stock cams but the turbo spooled earlier and made more average power.

Now Mr 2, power peaked almost identically to Mr 1 and then power nosed over. Fitted plenum up and instantly power held in to the higher rpms and power peaked later. Resulting in a higher average power that allows the car to accelerate quicker in the higher gears, he now gets more speed out of a lower gear and it is noticably quicker on the road being able to rev the car and hold the gear instead of shifting early.

Quite a few rb30det's run up on Shauns dyno and its what he recommends as one of the first modifications you perform IF you want it making power at a higher rpm. He also said the stock exhaust manifold is good up to ~300rwkw, you then look at changing to some thing a bit nicer. Generally they see ~20-30rwkw increase at 300rwkw when dropping on a good exh. manifold on and touching nothing else other than tidying up the afr's/ign.

I really do believe rb30det's nosing over early in the 5000's is caused by the std plenum. Once they are back to making power where they should cams and exhaust manifolds make them absolutely scream.

I've attached a dyno sheet with mr1 and mr2's power curve.

RED: Mr1 - stock plenum, stock exh. manifold, Tomei 260 9mm cams, 3" exhaust and ~19psi using an EBC

BLUE: Mr2 - aftermarket plenum, stock exh. manifold, stock cams and 8psi - std wastegate setting

GREEN: Mr2 - aftermarket plenum, stock exh. manifold, stock cams, 2.5" exhaust and 17psi with slight valve float, it made 265rwkw on 15psi, 2psi only gained 5rwkw due to the valve float.

Another few psi saw lifters pump up and power peak to 280rwkw. No EBC was used just a simple cheap home made bleeder.

The cams really bring the turbo on earlier + the 3" vs the 2.5" would no doubt help a little.

It would be really nice to see how Mr2's would go with the same 260duration cams, valve springs sorted, a good EBC and a 3.5" exhaust.

[SilverECR33]

the turbo is too big for the motor but yet it is restricting power!! Weirdest statment ever! The GT35 would be sweet on an rb30. Stuff some cams into it and a good zorst and u should be fine.

hang on. i thought we were talking about bringing up the torque curve, rather than making peak power at high rpm?. somewhere we have gone off track? ..

If not.. ignore me and ill skip along down the road i came from.

[discopotato03]

Unless I'm misquoting I was told std Rb25 head exhaust port will flow ~ 68% of inlet port . When this rises to ~ I think 74-75% they work much better .

I think by the time the RB25 inlet manifold becomes a serious problem the factory tool for the job (RB26 top) is the solution . I know its expensive and doesn't go bolt to an R33 RB25 block but its the least limiting solution for an RB30 bottom end . Best factory inlet/valve train/std porting - but still needs work and arguably still lacks valve area for 3 litres .

For me personally I don't see a future in a very non standard and please defect me officer type manifold .

Just my own thoughts , cheers A .

[r33_racer]

Not as easy as that. A 4 litre running say 350rwkw is going to have a similar amount of exhaust gas as a smaller engine running 350rwkw. The smaller engine may need more boost and revs. But over all exhaust gas flow will be similar. The 4 liter might make 350rwkw @ 5500rpm on 17psi but the 3 liter might make the 350rwkw at 7000rpm at 23psi. The overall turbo size will be more reflective of how much potential exhaust flow an engine will require than the actual size of the engine.

Yeh i understand what your saying there. However if the 4 litre revs out to 7000rpm as well and makes 375kws with little power increase probably because of the restriction as its flowing more gas then the 3 litre at 7000rpm regardless of powermade either way. A 4" exhaust would be a basic upgrade for a turbo 250xflow while for us its a pretty high end upgrade as 3" or 3.5" normally does it for quite sometime. The way you look at it..your right and the way i look at it im right...so were both right at least i think.

Hopefully i explained what i was thinking correctly.

[r33_racer]

Yeh i agree with you A...if i could build another 30det...would definetly go for the 26 head.

Just a side note. I have had a/m manifolds both intake and exhaust on my r33 for the last year or more and never had any problems with tpt...infact ive never had a cop look under my bonnet yet in the whole time ive had the car.

Edited January 22, 2007 by r33_racer

[DennisRB30]

Yeh i understand what your saying there. However if the 4 litre revs out to 7000rpm as well and makes 375kws with little power increase probably because of the restriction as its flowing more gas then the 3 litre at 7000rpm regardless of powermade either way. A 4" exhaust would be a basic upgrade for a turbo 250xflow while for us its a pretty high end upgrade as 3" or 3.5" normally does it for quite sometime. The way you look at it..your right and the way i look at it im right...so were both right at least i think.

Hopefully i explained what i was thinking correctly.

At the end of the day I can show you some 2JZ graphs with 380rwkw with this turbo. A 650-700 horsepower turbo is going to need to expel 650-700hp worth of gas when pushed to its limits regardless of engine size (as long as the engine is large enough max out the turbo) Its the turbo which limits this not the engine. All that will happen on a larger engine is it will choke the larger engine sooner. Supras pick up huge power gains when swapping to larger exhausts from 3". I can't see why a similarly developed RB30DET would be different.

Yes you can make good power with a 3", but if you are making good power with a 3" you will see great gains when you go larger. I'm talking over 300rwkw here. An XR6 has an exhaust equivalent to larger than 3" STOCK! Since its fairly large you can make great power though it, but it starts to limit power after 300rwkw.

[discopotato03]

Yep me neither Michael , I'm sure its the messages people and their cars sent out when they drive them on the street .

Cheers A .

[Black_R33]

Thanks for the input guys, although we seem to be drifting off topic....Is anyone running engines with the standard inlet manifold and making over 300RWKW? I think the first test we are going to do is drop the exhaust and spin it up.....then put on an adapter to read the boost on the ex side....Mmmmmmmm

[kastin]

so the 25 plenum runs outa flow at 300rwkw when does the standard 26 plenum?

[Cubes]

Thanks for the input guys, although we seem to be drifting off topic....Is anyone running engines with the standard inlet manifold and making over 300RWKW? I think the first test we are going to do is drop the exhaust and spin it up.....then put on an adapter to read the boost on the ex side....Mmmmmmmm

Have you ignored my previous posts?

The dyno sheet attached previously, the red plot is of an RB30DET making over 300rwkw with a gt35r .82, tomei poncam 260duration 9mm lift, std inlet manifold, std exhaust manifold, ~19psi and AVGAS. As you can see, an early rpm peak power. The same occured to the 'mr2' until he dropped an aftermarket plenum on.

Kastin,

The RB25DET plenum doesn't 'run out of flow' it simply isn't suited to the 3ltr, it was after all designed for the 2.5ltr.

[kastin]

Kastin,

The RB25DET plenum doesn't 'run out of flow' it simply isn't suited to the 3ltr, it was after all designed for the 2.5ltr.

ok cubes then is the 26 plenum "suited to the 3ltr" bottom end

Cheers

[Black_R33]

Cubes-

"Have you ignored my previous posts? "

A. No, they are interesting points its just that there is no dyno chart of MR2 engine before his new plenum was put on so the comparison is not between the same engine and there are too many variables to gain an accurate insight to the why's..

"The dyno sheet attached previously, the red plot is of an RB30DET making over 300rwkw with a gt35r .82, tomei poncam 260duration 9mm lift, std inlet manifold, std exhaust manifold, ~19psi and AVGAS. As you can see, an early rpm peak power. The same occured to the 'mr2' until he dropped an aftermarket plenum on."

Q.Have you got the dyno of MR2's before he put the plenum on, that would give a pretty accurate indication!

Q.What if MR1's early peak was caused by flow issues in the exhaust etc. Unless the other car had the same exhaust, that's another reason that makes it hard to compare.

NOW, you still may be on to something, but I don't want to guess the soulution and waste $$

Now that these engines are becoming more popular, there must be some Guru's out there that know how to set them up right. They all want to nose dive up the top!!!!

Back to your comments SilverBulletR33

"hang on. i thought we were talking about bringing up the torque curve, rather than making peak power at high rpm?. somewhere we have gone off track? .. "

That's a great point! The 3L is a longer stroke than the 25 so its not going to want to rev as hard, SO..... with its bigger displacement should it not make more torque lower down the rev range.....WHY WHY WHY?

Thanks Guys, keep it coming

Edited January 23, 2007 by Black_R33

[Cubes]

A. No, they are interesting assumptions its just that there is no dyno chart of MR2 engine before his new plenum was put on so the comparison is not between the same engine and there are too many variables to gain an accurate insight to the why's..

Its not an assumption when multiple RB30DET's on the same dyno are suffer nosing over and the common denominator is the stock inlet plenum; drop a plenum on them and power peaks at a higher rpm.

I know of 4 RB30DET's on Shauns dyno who all nose over early with the stock plenum. Its only the ones with aftermarket plenums (another 3 that I know of) that don't have that issue. I wouldn't call that an assumption.

Q.Have you got the dyno of MR2 before he put the plenum on, that would give a pretty accurate indication!

Yes.. I've attached it. Do note a dyno run was performed on 8psi, the new plenum fitted, 800cc injectors fitted, afr's tidied up then another power run performed. Ignition was not touched, Interestingly at 17psi its now running more ignition that it was when it was at 8psi. So no doubt push more ignition in to it on 8psi and the mid range would come up.

Q.What if MR1's early peak was caused by flow issues in the exhaust etc. Unless the other car had the same exhaust, that's another reason that makes it hard to compare.

NOW, you still may be on to something, but I don't want to guess the soulution and waste $$

There's too many rb30det's that have been run on the same dyno that regardless of exhaust size if they stick with the stock plenum they nose over early.

Mine, Bl4ck32's, a couple of VLT's, MR1 and MR2's.

Now that these engines are becoming more popular, there must be some Guru's out there that no how to set them up right. They all want to nose dive up the top!!!!

Yep Shaun at Boostworx has done a lot of these now.. He said the plenum is the way to go to bring that peak power back up to a respectable rpm.

Regardless of boost run with the GT35r .82 power always peaks at the same rpm. Be it 8psi or 20psi.

Please see the previous attached dyno sheet where I plotted the red.

Thats making 300rwkw odd on 19psi with cams etc so as you can see its NOT the stock CAMS causing power to nose over.

[paulr33]

thats a lot of stuff changed at any one time to directly pin point the culprit.

just how does the greddy font facing plenum help? is it larger diameter? bigger runners or channels? larger internal volume? anyone measured volume of each?

it doesnt seem to me obvious how the plenum unlocks extra power or un-chockes the top end.

we saw r31nismoid's 25t make over 350rwkw with a 600hp gt30. now it has different slow to a 3 litre but it could certainly make the power.

[Cubes]

Paul, its not the power that is the problem. They still make the same power with the stock plenum but its what I call peaky power. But regardless MR2's RB30DET GTS4 didn't have a lot of things changed. Just Plenum and injectors, thats it.

At 180rwkw or 300rwkw the RB30DET's with the stock plenum peak at the same RPM. There's multiple examples of this in Boostworx's dyno pc.

But its not just myself who has made the conclusion. I don't tune or setup each car. Boost worx does.

Boostworx came to the conclusion well before myself.

[paulr33]

hmm i wonder if there is some mathematical way if we can work out if this is true or not, using CFM calculations and head airflow or something like that.