R33 Rb30 Conversion

[Cubes]

F1... Still a 3ltr.

[r33_racer]

ohh yeh...thats the way to do it. I would like to build a spaceframe r34 or r32 gtr but in gtst form. rb30det in it with holinger 6 speed. take the whole front end off after undoing like 6 zues clips and have free accesss to everything in the engine bay with shitloads of room for your big hands and big arms to swing spanners and do stuff. man i gotta stop dreaming.

[ISL33P]

good stuff AM Performance - so much for all the know it alls saying a stock plenum is good enough for 300rwkw without a restriction........dream on people !!!!!!! significant differences from as little as 188rwkw which is pretty much a stocka rb25 with intercooler, exhaust and boost upgrade.

the mid range loss can not be attributed to the new plenum due to the boost spiking and giving a higher output figure at that specific part of the rev range. an all round significant improvement, well done again.

i have proven on several different engines that short runners show no negative effect at all - quite the opposite usually - on low-mid range torque/power on any turgbcharged application. time for some to get back to the drawing boards....yes that is all you "experts" out there

sorry for the rant but people thought my comments in other "technical" threads were just a cheap form of advertising. this just goes to show that people out there need to try it before bagging it because their experiences are all to narrow minded and not what progress is all about and this is what people are continually looking for from a perfomrance car.

Thanks,

Ariel

[Cubes]

The 3ltrs really do benefit with a short runner large plenum.

Which has got me thinking... The plazman plenums.

Not really a good idea on the 3ltrs as they retain the standard runners?

I'm still quite stoked we've stumbled upon the 'restriction' that holds back peak power rpm in the rb30det's.

The only reason it had a plenum thrown on it is because you can't lower the motor in the GTS4's so a plenum it had to be.

So quite a stumble indeed.

ISL33P,

You do a plenum to suit the r32 rb25de?

Something that may require sending in our own inlet manifold to be chopped up or can you sort out that side of things?

The std plenums really do leave the rb30det feeling a bit like a high powered diesel.

[Craved]

will be interesting to see once mine is finally assembled, i already have the plazmaman plenum installed on my rb25.

This will go on the rb30 so we'll see how it goes. wish i could afford to test the short runner vs long runner plenums back to back.

[Cubes]

With the short runner there was 100% nothing lost off boost.

If anything it looked as if it picked u 0.5rwkw, but well within dyno variances.

[Sydneykid]

good stuff AM Performance - so much for all the know it alls saying a stock plenum is good enough for 300rwkw without a restriction........dream on people !!!!!!! significant differences from as little as 188rwkw which is pretty much a stocka rb25 with intercooler, exhaust and boost upgrade.

the mid range loss can not be attributed to the new plenum due to the boost spiking and giving a higher output figure at that specific part of the rev range. an all round significant improvement, well done again.

i have proven on several different engines that short runners show no negative effect at all - quite the opposite usually - on low-mid range torque/power on any turgbcharged application. time for some to get back to the drawing boards....yes that is all you "experts" out there

sorry for the rant but people thought my comments in other "technical" threads were just a cheap form of advertising. this just goes to show that people out there need to try it before bagging it because their experiences are all to narrow minded and not what progress is all about and this is what people are continually looking for from a perfomrance car.

Thanks,

Ariel

Hi Ariel, "experts", I guess that would include me and I have most definitely "tried it", in fact several “its”. They all fail to produce higher average power levels on RB25DET's up to their limit of 7,250 rpm (equivalent airflow to 6,000 rpm in an RB30).

Looking at the dyno graphs I see exactly the same result, lower average power up to 5,750 rpm. This means the standard plenum equipped engine would be faster accelerating from 3,000 rpm to 5,750 rpm in every gear than the aftermarket plenum equipped engine.

Personally, on an RB30 with standard internals, I would much rather have my max power at 5,250 rpm (using the standard plenum), instead of 6,000 rpm (using an aftermarket plenum). After all higher rpm = shorter engine life.

In summary, why should spend money I buy an aftermarket plenum that produces slower acceleration and wears my engine out faster?

cheers

[Cubes]

Hey Gary..

I remember a thread a while back that a discussion was held on 'should i fit a plenum to an rb25' or something along those lines. I too don't believe an after market plenum on the rb25 is worth while as the std gear works well with the given setup. i.e gearing, where peak power rpm lands, how power holds etc.

On the 3ltr I'm not so sure.

First off a possible explanation to why mid range power was down after the plenum was fitted up.

The std plenum boost was peaking to 9psi then tailing off to 8psi by peak power.

With the aftermarket plenum boost was peaking to 8psi then holding perfectly through out the rev range. With the slightest boost increase it made quite a noticeable increase in power. Roughly 1psi equalled 10rwkw until valve float became evident.

I'd have to conclude it was most definitely the slight change in boost level that caused the power difference through the mid.

Why boost peaked then tailed off with the std plenum I'm not sure.

The problem is with a GT35r .82 is that it comes on strong from mid to high 3000's. Having peak power just over 5000rpm and then nose over hard really only leaves you with ~1500rpm to play with.

With the std R32's gearing having a peak power so early in the rpm really doesn't work too well..

The benefit of AM-Performances set-up is that power holds well instead of simply peaking and then nosing over hard.

If we would see the same results on a stock turbo or high flowed turbo I'm not sure.

[shanef]

hey cubes howd u get that info?

[Cubes]

Gearcalc.

Gear_Calc.zip

[Sydneykid]

Hey Gary..

I remember a thread a while back that a discussion was held on 'should i fit a plenum to an rb25' or something along those lines. I too don't believe an after market plenum on the rb25 is worth while as the std gear works well with the given setup. i.e gearing, where peak power rpm lands, how power holds etc.

On the 3ltr I'm not so sure.

First off a possible explanation to why mid range power was down after the plenum was fitted up.

The std plenum boost was peaking to 9psi then tailing off to 8psi by peak power.

With the aftermarket plenum boost was peaking to 8psi then holding perfectly through out the rev range. With the slightest boost increase it made quite a noticeable increase in power. Roughly 1psi equalled 10rwkw until valve float became evident.

I'd have to conclude it was most definitely the slight change in boost level that caused the power difference through the mid.

Why boost peaked then tailed off with the std plenum I'm not sure.

We have no idea of the comparable atmospheric conditions prevailing on the days that the dyno runs were performed. The dyno runs do not appear to have been carried out in Shoot Out mode by an accredited workshop, hence no atmospheric information is shown. All I have done in the previous post is to comment on the information as supplied.

Remember that boost is simply a measure of resistance to airflow, lower boost should indicate less resistance. Which I am sure the proponents of aftermarket plenums would quickly lay claim to. Less resistance should lead to higher airflow and higher airflow means more power.

Since we have been told that nothing else was changed, I can only conclude that the aftermarket plenum has less resistance but fails to turn that increased airflow into increased power. Based on the evidence I would maintain that this plenum, like all the others I have tested, has poor distribution which results in the lower power output.

Hence the lower power output is not in fact due to lower boost, but due to poor distribution of the increased airflow. As is common, at higher rpm the aftermarket plenum's poor distrbution becomes less of a problem.

cheers

[shanef]

i dont suppose u have the data for the 32 gtr?

[Sydneykid]

The problem is with a GT35r .82 is that it comes on strong from mid to high 3000's. Having peak power just over 5000rpm and then nose over hard really only leaves you with ~1500rpm to play with.

With the std R32's gearing having a peak power so early in the rpm really doesn't work too well..

The benefit of AM-Performances set-up is that power holds well instead of simply peaking and then nosing over hard.

If we would see the same results on a stock turbo or high flowed turbo I'm not sure.

Having had this discussion before, I will summarise for the readers.

At 5,500 rpm in 5th gear with the standard diff ratio the R32GTST will be doing ~205 kph with 245/40/17 tyres. Which I consider a more than high enough top speed for a road car. The speed/rpm in the other gears is a more matter of the standard gearbox ratios, which are not easily (cheaply) changed.

So the issue is more to do with the turbo chosen rather than the gearing of the car. Personally for a standard internals RB30 I wouldn't be using a GT35R, something around the GT3071/76 would be a much better choice. That will give you a very decent power band from 3,000 to 5,500 rpm, which is more than enough for the standard gearbox ratios. Plus a much higher average power and, as a result, faster acceleration.

Simply put, buying an aftermarket plenum costs extra money, selecting the right sized turbo doesn't.

cheers

[Sydneykid]

i dont suppose u have the data for the 32 gtr?

For an R32GTR, use 29 kph per 1,000 rpm in 4th gear, it's close enough for dyno comparsons.

Cheers

[Cubes]

Not sure if you got the gist of my last post..

But anyway...

Both day temps were low 20's.

The only variables as I mentioned above and a few posts back were:

Slightly lower boost

Ign timing wasn't adjusted after the plenum went on.

As I said above..

The problem is with a GT35r .82 is that it comes on strong from mid to high 3000's. Having peak power just over 5000rpm and then nose over hard really only leaves you with ~1500rpm to play with.

With the std R32's gearing having a peak power so early in the rpm really doesn't work too well..

The benefit of AM-Performances set-up is that power holds well instead of simply peaking and then nosing over hard.

If we would see the same results on a stock turbo or high flowed turbo I'm not sure.

Its all about the complete package, the gearing simply isn't suited to a motor that doesn't rev.

[Cubes]

Your right Gary the GT35r really is a not so good match for the RB30DET if it isn't able to rev.

It comes back to the old its expensive once you get over 450bhp.

So the perfect stock rb30 with stock in/exh. manifold setup would be to simply throw a VG30/R34 GCG highflow on it, make 260rwkw odd and be happy knowing that if you want much more its going to cost you considerably more than it would to do the same to an rb25 as you need that inlet manifold.

So... It sounds like you've kind of agreed with me.. lol

[Sydneykid]

Your right Gary the GT35r really is a not so good match for the RB30DET if it isn't able to rev.

It comes back to the old its expensive once you get over 450bhp.

So the perfect stock rb30 with stock in/exh. manifold setup would be to simply throw a VG30/R34 GCG highflow on it, make 260rwkw odd and be happy knowing that if you want much more its going to cost you considerably more than it would to do the same to an rb25 as you need that inlet manifold.

So... It sounds like you've kind of agreed with me.. lol

Sorta.......the original standard internals RB30 that I built in 1999 (last millenium, eeek) used an old T04E which is basically the same size as a GT3071, but without the later aerodynamics or balls. It makes (still) just a bit over 300 rwkw (475 bhp on the engine dyno) and I really like its performance envelope. It would benefit greatly from a turbo generation update and set of Poncams.

cheers

[Cubes]

Sorta.......the original standard internals RB30 that I built in 1999 (last millenium, eeek) used an old T04E which is basically the same size as a GT3071, but without the later aerodynamics or balls. It makes (still) just a bit over 300 rwkw (475 bhp on the engine dyno) and I really like its performance envelope. It would benefit greatly from a turbo generation update and set of Poncams.

cheers

Sounds a little like this one done here in Adelaide by Allen engineering.

http://users.tpg.com.au/cobra30/twincam.htm

Apart from what it says on paper whats most important is 'HOW' it feels to drive. Its a sports car afterall, not a family wagon with a big v8 dumped in it.

[discopotato03]

I'm curious to know if the std R33 RB25DET head and inlet system (forgetting the VCT for a sec) works much if any better than the R32 RB25DE bits . Cubes did you say that the ports were a bit larger on the R33 heads ? Inlet manifold passages/plenum/throttle body ? If this is the case would the std R33 bits be a better basis to start with ? I think I'd prefer factory engineering to buzworks fancy fabrications manifolds .

Only guessing but with the proliferation of R33's these days finding one of those top ends may be easier and cheaper initially anyway .

Cheers A .

[Cubes]

Yes the ports and runners are slightly larger on the R33 RB25DET.

The plenum looks pretty much the same as does the t/b.

The R33 head will always be a better starting point and obviously the RB26 better again.