R33 Rb30 Conversion

[mambastu]

doh!

Edited November 29, 2006 by mambastu

[Sydneykid]

SK,

Please don't take offence at anything I say I'm just trying to get my head around where you are coming from as to myself its as clear as day the wider power band is considerably better than a peaky one even though it 'may' loose a little through the mid range.

But first...

I'm curious how you tell it has poor distribution when the car clearly had a little boost control issue prior to the plenum and after the plenum ign wasn't tuned to suit. There was no boost controller connected so the external wastegate should have held boost perfectly to start off with, not spike up then tail off.

Possibly an issue some where else that was accidentally sorted when reworking i/c piping etc.

The plenum was simply dropped on, afr's set back to 12:1 due to it running larger 800cc twin sprays (no ign tweaking) and a power run performed.

Either way I really do believe its worth while for the RB30DET running a GT35r even when running the lower 8psi and making under 200rwkw. I have no results with one running a gt30r so I can't conclude.

Consider...

The rpm drops between gears, selecting the next gear your going to be in more power with a wider power band.

A narrow power band that may make more power earlier will no doubt be quicker accelerating out of a corner in a given gear but those benefits are over once that car selects the next gear as they will drop to say 160rwkw then have to build up where as one with the wider power band may only drop to 240rwkw then build up to 270rwkw. So a much greater average power for the given gear ratio's which should translate to quicker 0-100 and quicker 1/4 times.

The car with the narrow power band will also loose out at higher road speeds, possibly resulting in lower TS 1/4 speeds.

Hope that made sense.

Hi, I only went on what was posted, a before and after dyno graph. I had no knowledge of retuning or higher flow injectors or anything else that was done at the time.

The logic is quite simple, if the aftermarket plenum flows better then that reduces the restrictions and the boost should "decrease". The boost controller (spring on the wastegate or EBC) would correct for that and "increase" the boost back to its set level. Hence there would be more airflow as a result of removing the restriction. More airflow always means more power (all other things being equal).

But between 3,500 rpm and 5,000 rpm we are actually seeing less power. How can that be? Either the aftermarket plenum increase the restriction or it has poor distribution. Since the power is higher at higher rpm then we can most likely rule out increased restriction, which leaves poor distribution as the reason for the decreased power.

Moving on to the average power, I know you know the rpm drop on gear changes, but for other readers. The 1st to 2nd gear change at 6,000 rpm (in 1st) results in drop of ~2,500 rpm to ~3,500 rpm in 2nd. Which is the widest rpm drop, the 2nd to 3rd drop is ~2,000 rpm, 3rd to 4th is 1,500 rpm and 4th to 5th ~1,000 rpm.

Keeping the above in mind and relying on the information given, the best estimate of accelleration (potential) is average power between 3,000 rpm and 5,500 rpm where the standard plenum averages 155 rwkw and the aftermarklet plenum 151 rwkw.

Note that I had to use ~5,500 rpm as the maximum rpm as the standard plenum dyno graph doesn't show figures past that and I don't believe extrapolation is the correct approach in this case. But even if I did use a straight line extrapolation of the standard plenum dyno graph to 6,000 rpm, the aftermarket plenum still has a lower average power (ie; 178 rwkw versus 180 rwkw).

Just becuiase the aftermaket plenum makes ~4 rwkw more max power doesn't overcome the fact that at 4,500 rpm it looses ~15 rwkw. So all things being equal, the standard plenum equiped car would be definitely be faster accellerating from 3,000 rpm to 5,500 rpm and would most likely be faster from 3,500 rpm to 6,000 rpm than the aftermarket plenum equipped car.

Personally, I would much rather spend $800 on a pair of Poncams and get higher average power, than spend twice that on an aftermarket plenum and get less.

cheers

[Roy]

Problem is...are all things equal? The ignition wasnt changed. Also if the wastegate gets its pressure signal from the pipe to the intercooler then the spring isnt to know what pressure the inlet manifold is seeing. Could explain the slight difference in boost? Would not normally be a problem....but hard to tell based on the info given and nto being there. All you can really do is go on Cubes experience...

So is it possible the thing is flowing a bit better, making less power which can be explained by bigger injectors and tune which neglects changes to ignition?

Im surprised to read the last few pages that the RB30s are choking at higher revs...so is that purely cams?

[Cubes]

Cams did nothing to shift peak power to a higher rpm in Sky30's case.

Pumped up the mid range and brought it in sooner though.

[Roy]

Cams did nothing to shift peak power to a higher rpm in Sky30's case.

Pumped up the mid range and brought it in sooner though.

So how do you get the RB30s to make power over 6,500rpm?

[r33_racer]

i have no idea whats wrong with your rb30's but at 8000-8500 our rb30 was still making power...no signs of tapering off at all. But we have a greddy plenum which ive heard does that....same poncams as everyone else too. But i wouldnt think its just the plenum allowing our rb30 to make power past 6500 would it?

So does the rb26 plenum not have any such problems as its more like a holding tank as the throttle butterflies are right infront of the ports.

[discopotato03]

Problem is...are all things equal? The ignition wasnt changed. Also if the wastegate gets its pressure signal from the pipe to the intercooler then the spring isnt to know what pressure the inlet manifold is seeing. Could explain the slight difference in boost? Would not normally be a problem....but hard to tell based on the info given and nto being there. All you can really do is go on Cubes experience...

So is it possible the thing is flowing a bit better, making less power which can be explained by bigger injectors and tune which neglects changes to ignition?

Im surprised to read the last few pages that the RB30s are choking at higher revs...so is that purely cams?

Good question Roy , I tend to think the reason may involve turbine housing AR and exhaust gas speed . Again I'd look at the GT3076R's turbine map and note the difference in flow between the 1.06 and the 0.82 housings . I just happen to have that map handy and the 1.06 has a maximum flow of ~ 26.5 lbs compared to the 0.82's ~ 23.3 lbs . Just for the record the 0.63 is ~ 20.5 lbs flow .

Provided my mathematics is correct I get the 1.06 being a 14% increase in flow over the 0.82 and this would help with our 20% larger than RB25 RB30 . Hotter cam profiles genereally raise an engines state of tune and increasing the capacity pulls it back down . So with gas speed increasing by the 3L drawing through a 2.5L head/valves removing or reducing any choke points has to help .

Its not very surprising that no one really bothers with GT3076R's on RB30's , the effort and money to make it happen doesn't justify only 200-220 Kw . In a way I suppose you could compare the difference of running the RB25 turbo vs the VG30 turbo on the VG30 engine . The larger turbine housing helped prevent the turbo from leaping into life when the engine was producing enough low rev torque . The smaller one would have made it very on off and very choked with any revs on the engine . I reckon if I was to run a GT3076R on an RB30 it would have to have the largest exhaust housing even though in this form it becomes unacceptably laggy on 2.5 engines . Garrett reckon they have this GT3076R/GT3582R area pretty finely sliced up but I reckon they read it wrong . As we know the void between the two is very obvious and not difficult to overcome but try telling them that .

As for inlet systems I think it comes down to the intended purpose so for me RB25 on RB25 and RB26 on RB30 , expensive yes but cheap for competition grade equipment .

Cheers A .

[r33_racer]

As for inlet systems I think it comes down to the intended purpose so for me RB25 on RB25 and RB26 on RB30 , expensive yes but cheap for competition grade equipment .

Yes i think we're about to find that out the hard way now. Scrap rb25 heads and go for the 26 ones...solid followers, better inlet system, sodium filled valves. Much better platform to build on.

[Cubes]

Yep it looks that way if you want an Rb30DET that rev's.

By the time you throw a plenum on the rb25 head that allows it to rev you may as well have bought the rb26 head.

[ISL33P]

the words "like all others" point to the fact that you have not only "tested" this style but others as well. what others are they ? what is their flow distribution like between cylinders on a flow bench/dyno (ps i am still waiting on those supposed egt logs you have in regards to them proving water temp's affecting afr/egt's in the rear cylinder/s of rb26's).

i know what the standard one flows, and it isn't that good distribution wise. with a variance of 12.5% in air flow between cylinder #1 (the lowest flowing) and cylinder 4 (the highest flowing) it is nothing to brag about and something that is easily improved on (centre feed plenums are not as good a people think).

your choice of rpm range for average power neglects the fact that nearly all modified cars have an increased power level outside of these values and hardly ever loose response/power in that range (in extreme cases they may). what do you revs your engines to ? what rev's do you need for it to fall back in the range where it will not greatly affect the cars accelaration upon changing gears....i doubt it is anywhere between 3-5000rpm. since this is the rpm range where different turbo's really come into there own, it doesn't really give you a true and correct indication of the cars true performance regardless of plenum type/design.

more airflow = more revs = more power. higher average power from 0-rev limit and beyond is one happy driver/owner.

PS anyone out there got a greedy (or imitation) plenum out there not yet installed (will happily pay for postage there and back) ? i would like to see how badly there really distribute air but have enough airflow to increase power and happily post up all results and maybe throw in some other interesting results.

[r33_racer]

yes rub it in cubes...

You know how everyones always flow testing inlet manifolds...I would like to see one of kyles manifolds flow tested to see in comparison with the chinese ones and std, along with the extrude honed ones like UAS did.

Does anyone have an answer to my rb26 inlet manifold question please?

[Cubes]

yes rub it in cubes...

You know how everyones always flow testing inlet manifolds...I would like to see one of kyles manifolds flow tested to see in comparison with the chinese ones and std, along with the extrude honed ones like UAS did.

Does anyone have an answer to my rb26 inlet manifold question please?

Kyles... He does exhaust manifolds not inlet manifolds??

[r33_racer]

Your right into stating the obvious nowadays hey Cubes?

[Cubes]

lol... and the sad part is its not intentionally. lmao

Stressful time of year.. uni exams etc so I'm off with the fairies a little.

[r33_racer]

ahh i see. University hey. Should be nearly done by now? For the year i mean.

Not intentional...geez i thought you were being, just to piss in my pants.

[Cubes]

Yep almost done.. exam tomorrow and Thursday then its all over for good.. maybe.. I'm considering a post grad course, that depends on the other half and how she goes with work.

Lol yes it was not intentional.. lol, I just didn't read the post well.

[Sydneykid]

the words "like all others" point to the fact that you have not only "tested" this style but others as well. what others are they ? what is their flow distribution like between cylinders on a flow bench/dyno (ps i am still waiting on those supposed egt logs you have in regards to them proving water temp's affecting afr/egt's in the rear cylinder/s of rb26's).

i know what the standard one flows, and it isn't that good distribution wise. with a variance of 12.5% in air flow between cylinder #1 (the lowest flowing) and cylinder 4 (the highest flowing) it is nothing to brag about and something that is easily improved on (centre feed plenums are not as good a people think).

your choice of rpm range for average power neglects the fact that nearly all modified cars have an increased power level outside of these values and hardly ever loose response/power in that range (in extreme cases they may). what do you revs your engines to ? what rev's do you need for it to fall back in the range where it will not greatly affect the cars accelaration upon changing gears....i doubt it is anywhere between 3-5000rpm. since this is the rpm range where different turbo's really come into there own, it doesn't really give you a true and correct indication of the cars true performance regardless of plenum type/design.

more airflow = more revs = more power. higher average power from 0-rev limit and beyond is one happy driver/owner.

PS anyone out there got a greedy (or imitation) plenum out there not yet installed (will happily pay for postage there and back) ? i would like to see how badly there really distribute air but have enough airflow to increase power and happily post up all results and maybe throw in some other interesting results.

Let's see what plenums/inlet manifolds have we tested;

Sub Zero (RB25) plenum with standard inlet manifold

Plazmaman (RB25) plenum with standard inlet manifold

GReddy (RB25 and RB26) plenum and inlet combined

Micks Metalcraft (RB25) plenum with standard inlet manifold

Standard (RB20) plenum and inlet manifold combined

Standard (RB25) plenum and inlet manifold combined

Standard (RB26) plenum and inlet manifold combined

Nismo RB26 plenum with standard throttle bodies and inlet manifold

Top Secret (RB26) plenum and inlet manifold combined

Veilside (RB26) plenum and inlet manifold combined

Jun (RB26) plenum and inlet manifold combined

and a couple more that I can't recall right now.

I am not sure how you tested the standard RB25 inlet manifold/plenum. But if, in the real world, it had 12.5% variation in airflow between cylinders there would be blown up RB25's all over the place. Since that obviously isn’t the case then the only conclusion that can be drawn was that the testing methodology was flawed.

Let's get into the rpm range discussion. I know the gearbox ratios, I know that if you change from 1st to 2nd at ~6,000 rpm (in 1st) then the engine ends up at ~3,500 rpm (in 2nd). That's why I chose the range 3,500 rpm to 6,000 rpm for an average power calculation. Plus it also happens to be the range shown on the dyno chart that we are discussing. I can hardly do comparisons if I don't have the data.

Sure if the car had a close ratio gearbox then I could us a smaller rpm range to calculate the average power. The maximum RPM drop (on a gearchange) in the Hollinger is 2,000 rpm. A change at 7,000 rpm in 1st results in 5,000 rpm in 2nd. But as far as I know this car has a standard ratio gearbox, hence why I did the average power calculation that way.

Recently I was asked by the importer to test (flow bench and dyno) a "copy" RB25 plenum and inlet manifold combined, but we are so busy at the moment I had to decline. We get this sort of request often as we have the expertise and equipment and no affiliation with any manufacturer, we are only interested in the results.

Personally, I would like to find a good aftermarket plenum/inlet manifold for RB25's, it would make my life a whole lot easier. Unfortunately to date I haven't found one that suites our applications that performs any better than the standard one.

cheers

PS; I PM 'd the EGTS to you ages ago, if you can't find them, please let me know and I will dig them out and send them again.

[Cubes]

Gary,

I've double checked the rpm vs speed and it appears you multiply the speed by 40.189 to get the correct rpm.

The rev cut was set to 7000rpm and the dyno pull was stopped just before at 6800rpm.

So on 8psi peak power shifted from ~5600rpm to almost 6500rpm.

When its making 270rwkw boost does appear to be coming on a little soft as its running a basic little bleeder setup so the boost curve elbow is round so to speak. Power holds until 'almost' 6900rpm then it begins to drop off, valve springs are playing up so it shall be interesting how it all pans out.

[Sydneykid]

Gary,

I've double checked the rpm vs speed and it appears you multiply the speed by 40.189 to get the correct rpm.

The rev cut was set to 7000rpm and the dyno pull was stopped just before at 6800rpm.

So on 8psi peak power shifted from ~5600rpm to almost 6500rpm.

When its making 270rwkw boost does appear to be coming on a little soft as its running a basic little bleeder setup so the boost curve elbow is round so to speak. Power holds until 'almost' 6900rpm then it begins to drop off, valve springs are playing up so it shall be interesting how it all pans out.

That's ~24.5 kph per 1,000 rpm, are these dyno runs done in 3rd gear?

With barely 35 lbs on the seat when new and 1 bar of boost, I have no doubt that the valve springs are "playing up".

cheers

[GTR-Ben]

Glad I used my GTR head that came with cams and was ported

And I might get to drive it this year!!