UAS RB20/25 Intake Plenum.

[Boosted Zed]

I thought to make a post here as we have been receiving LOTS of calls and emails about our over due intake plenums. Plasma man Racing is making them exclusive for us. He makes the most beautiful and functional intercoolers, plenums etc in Australia. He has had a delay as had to make a huge press to make the top pieces, but should not be too far away now as he just finished making this press last weekend. 47 are being made.

We have been doing extensive flow bench testing at Abrasive Flow Engineering in Sydney and found at no surprise the factory RB20/25 intake plenum is not very good as the middle two runners that the throttle body shoot at get way more air than the outside ones. So if you are tuning the middle runners need much more fuel.

The plenums we are getting made has already been tested on a car with a prototype and made more power than any other RB25 SI or SII, and the test car was a I with stock dump and engine pipe and stock computer so even more impressive at 208rwkw.

Three reasons.

1. Less pressure drop.

2. Lower intake temps.

3. More even air flow to each cylinder.

This is from using QUALITY USA core, that is if getting the full kit, with smooth tapered end tanks and pipe work. Less bends and less pipe work being heated by radiator and engine.

Less pressure drop as less pipe and less bends. 1/4 psi or more with each 90 degree bend.

Far more even air flow to each cylinder from better design plenum, including machined trumpets inlets. I can't remember the thickness but think the main bottom plate is 12mm.

Also we have found Greddy plenums to be very coarse inside and too big especially the runners and on dyno actually lost power. This has been confirmed with other workshops. Where ours definitely makes power. Free power as less stress on motor.

Yes they bolt straight up with factory throttle or can use larger throttle body, factory throttle cable and fuel rail ready to go. When released they will be around $1500 each for plenums.

Pic of progress.

[Boosted Zed]

Link for more info.

http://nismo.com.au/pricelists/pricelist_s...ylineengine.htm

[Ryno]

John what deal will you be able to do, including the intercooler and piping?

[Wazz]

bolt on top half? or complete plenum? oringinaly i thought it was a bolt on top half on the site...

[Boosted Zed]

Top only yes. We have tooled up to extrude hone the lower runners also althugh test car did not have this. To have the ultimate you would do this and match port also as stock they are not the best. Ryno no firm price on full kit yet. There will be the normal 10% SAU discount or maybe more.

[Sydneykid]

I was going to let this slide, as any contradictory post may come across as being simply argumentative, and that is certainly not my intention. But it is so totally contrary to what I have experienced, I just have to ask for some more details.

We have been doing extensive flow bench testing at Abrasive Flow Engineering in Sydney and found at no surprise the factory RB20/25 intake plenum is not very good as the middle two runners that the throttle body shoot at get way more air than the outside ones.  So if you are tuning the middle runners need much more fuel.

I have tested the RB20/25 uneven airflow theory a couple of times, and found it to be a myth. My methodology has been to test the A/F ratios at the primary exhaust pipes, which I believe is the BEST measure of inequalities in airflow under boost. Any cylinders with higher airflow would show leanness when compared to other cylinders with lower airflow. I simply have not seen that, in fact the only cylinder that shows any leanness is #6 and (as slight as it is) that can be more likely attributed to water temp differences as it is the furthest from the water pump.

Testing on the flow bench can easily be flawed as it relies on vacuum to stimulate airflow, this does not necessarily generate the same airflow patterns as when boost is introduced into the equation ie, suck versus blow.

The question is then, how were the tests carried out? And how was the extrapolation to boost conditions calculated?

Less pressure drop as less pipe and less bends.  1/4 psi or more with each 90 degree bend.

This one is even more difficult for me to understand. If this were in fact the case, then in an RB25DET with the usual 6 X 90 degree bends, you would see a 1.5 psi difference in the boost pressure at the intercooler outlet tank compared to what you see at the throttle body. Having tested this many, many times, when selecting intercoolers, I have yet to see even 0.25 psi pressure drop.

Testing this on the flow bench can easily be flawed, as once again it relies on vacuum to stimulate airflow, this does not necessarily generate the same pressure drop as when boost is introduced into the equation.

So the same questions apply, how were the tests carried out? And how was the extrapolation to boost conditions calculated?

I expect that John may not able to answer the questions himself, but I am sure the testers will be able to fill in the gaps.

[JaFF]

the test engine made 208rwkw, what was it running before the plenum upgrade and what other mods?>

[Wazz]

Also.. all of those plenums in the pictures look like 25 Plenums... are these available for rb20's aswell... if so.. have you got them with 5 and 6 runners off set the others like they are on the factory plenum... (from wat i have seen anyway on my rb20

Waz

[B-Man]

This will be in interesting discussion as I know SK's view on front facing plenums versus factory.

Those plenums look very nice john - any pics of from the TB perspective ?? Just intested in seeing how the flow works.

[Boosted Zed]

Yes Sydney kid flow bench test is not conclusive but with common sense, theory and above all dyno test to back it all up hard to argue with dyno test. Also checked the thickness of the base and they are actually 16mm. We do lots of flow bench testing on our zed, testing different ports in heads and valves, and valve grinds, even found RB26 brass valve guides being shorter than the VG30 ones so less protruding into the port and proved a gain in cfm on flow bench test. Re the pressure drop with bends this is very general and can be more or less. We can talk and theorize back and forth and good to get input but the bottom line is OUR dyno tests prove it. We have never had a Skyline make this power even with addition of full exhaust and after market computer tuned. Keep in mind we have had hundreds on our dyno.

Also re the pic of 25 yes but this is not all of them and good counting.

[BBQ]

Also we have found Greddy plenums to be very coarse inside and too big especially the runners and on dyno actually lost power.  This has been confirmed with other workshops.  Where ours definitely makes power. Free power as less stress on motor.

Pic of progress.

I'm interested in that comment in particular.

Greddy being the company they are, Provide lots of aftermarket products, and carry out lots of testing. If their product wasn’t up to standard would the Japanese market use them?

The plenum in particular, is very coarse inside, and the runners may be big yes thats true.

But it depends on the applications its used for, Eg. If you were running a Gt35/40 with around 28psi boost level, which people do, running on an Rb25, with a ported head and a large set of cams. Would you want a plenum that has restrictive runners or a plenum that has a larger cfm capacity and larger runner capacity, increase Volumetric Efficiency in the head.

The USA Plenums are a good setup and look nice, But how well do they perform

on a heavily modified motor? As compared to a stock motor?

[Wazz]

with the tests of the r33.. have you tested one on a r32? i'd like to see the results of that.. before and after dyno sheets if thats possible please

[Sydneykid]

Yes Sydney kid flow bench test is not conclusive

Same result as we get, inconclusive results. The flow bench is simply not a good test in this instance

but with common sense, theory

Again I applied common sense and logic and I can not see how a plenum with the inlet at one end is going to be any better, in regard to evenness of flow, compared to one that feeds the plenum in the centre. To me that is illogical.

above all dyno test to back it all up hard to argue with dyno test

I will argue with a peak power number all day, every day, heavens it might have lost 50 rwkw everywhere else. Sorry but "208rwkw" tells me nothing about how well the plenum works.

We can talk and theorize back and forth and good to get input but the bottom line is OUR dyno tests prove it.  We have never had a Skyline make this power even with addition of full exhaust and after market computer tuned.

The control test here would to put the car on the dyno and tune it the best that can be achieved. Then swap the plenum and without changing ANYTHING else show that it makes more horsepower. Personally I would be looking for an average power increase, not just a peak number at one rpm point.

I have done this exact test with an RB26 plenum on an RB20, dismal failure, less power in most places than standard. I have done this test with a Greddy plenum on an RB25, partial success it gained power at some rpm points but lost them at others. I have done this test with a Greddy plenum on an SR20, absolute disaster, it lost power EVERYWHERE.

Hence my scepticism;

[KamikazeR33]

i like the design, although maybe u should include an option for shorter intercooler piping, gtr style.

plenums like this do make alot of difference. me and my mate tested the difference between our cars, both stock rb25's, mine had custom plenum, same size turbo. mine would kick in at 2200 and hit 1 bar by 3500 and his would kick in at around 3500 and hit 1 bar by 4500 rpm. although his was running stock computer with a safc and i was running a microtech LT-16s, im sure that tuning didnt make that much of a difference.

keep up the good work John

[Gts-t]

The gibson motorsport r31 retained the stock inlet plenum, did it not :headspin:

good enough for gibson motorsport, good enough for me

Other than that, it does look very nice

[JaFF]

sorry for sounding like a broken record, do you have a dyno sheet of before and after?

[BBQ]

Also out of curiosity what were the AFR for that dyno run ? And what fuel was it running for the Dyno Run ?

[Boosted Zed]

We will have them flow bench tested as have figures for the stock ones to compare. They will obviously flow better with stock or large turbo compared to stock one but may or may not be as good if you have a turbo you need a pole volt to jump over. I suspect they would be better than Greddy even with big flow turbo. If you got the Greddy extrusion honed may be a different story.

Also if you think that everything made in Japan is top stuff or best then you believe in stickers as not always the case although generally true. Come around to UAS one day and I show and tell and I am sure you will agree. We have lots of items made for us here in Australia way better than anything in Japan. E.g. our upper rear control arms made out of lighter and stronger Chrome Molly tube, tig welded with much better quality rod end and billet alloy spacers instead of heavy cheap mild steel ones. Weight 937 grams compared to 1498 grams Cusco brand. Unsprung weight, big advantage.

No tests on R32 but again common sense applies if makes more on R33.

[Kaido_RR]

question isnt a greddy plenum, about the same price or lower?

seems abit high for just a bolt on top when the greddy plenum replace the whole plenum but then again i could be wrong cuz i know little to nothing

[LANFOH]

G'day hows it goin?

Even if the custom plenum doesnt give gains in horsepower which is debatable there would still be sustantial gains in throttle response in the form of reduced throttle lag am I correct. And wouldnt the shorter pipes improve inlet temps thus horsepower?

Looks like an awesome unit John and I know Plasmaman fabricate some excellent stuff. If I had the cash Id put one on my line for sure...........maybe sometime in the future.

Cheers

Michael