UAS RB20/25 Intake Plenum.

[R31Nismoid]

post a pic of the board.

sounds chipped too me

[Col-GTSX]

I most certainlly has been played with im sure.....

Ill post pics when i remove it... A couple of weeks before i pay for and install my chosen ecu...

[Sydneykid]

The AF's were too rich to read 10:1 flat line..... Thats why i want an after market ecu. Its unsafe to run these rich ratios all the time... Just for a dyno run is fine...

It is most certainly not "unsafe" to run 10 to 1, in fact that is the most common A/F ratio I see on STANDARD Skylines. Nissan tune them at that A/F ratio for safety.

When you start upgrading things like exhaust, cat, dump, boost, intercooler, air filter etc you quickly find 9's are far more common and 8's are not unusual. On the Stagea RB25DET it went to 9's just by turning up the boost from 0.4 bar to 0.7 bar. Plus it jumped around all over the place. I had to apply a reasonably amount of AFM voltage correction with the Jaycar DFA to get anywhere near a consistent 10 to 1.

If you are seeing "10:1 flat line" then my personal opinion is that there is no way that some tuning has not been carried out.

[Boosted Zed]

I had a bit more time to read through all this and Sydneykid your input is often good although you lost me with this statemnt in your post earlier.

"Well, where does that leave me? Seems my original rule of thumb is still the best I can come up with, i.e.; don't change the inlet system unless you are changing the pistons. Because the inlet system is most certainly not going to limit the power or the response up to that point, and in light of quite a few cars now, maybe well past that point."

What has the pistons got to do with the inlet. If the inlet and outlet of the engine has less restriction then less stress and heat on the pistons and less need to upgrade the pistons and will make more power. Or if you are saying the level of cost and power, then sort of different story but still?

Just because uncle Theo runs factory plenum and does 9's he would probably do better if he had the Nismo intake plenum or Greddy extrusion honed. Is his stock though? The Nismo GTR plenum is beautiful as has machined trumpets inside also and would be my pic. For really BIG hp bigger custom plenum may work better. Geoff from SSS Automotive in Sydney qualified mech and circuit races a R32 GTR with Gibson motor says factory GTR plenum is good for up to 700hp then needs bigger or better. Can't remember which one he recommends but he is up on all this as it is his business and passion. However I suspect going to Nismo plenum would make more power even with stock turbo's although MUCH better design than the RB20-25 design which is not good. To say this car or that car did this and that with stock AFM or stock intake etc . They would be faster if had better plenum or no AFM probably etc. One could run a 10 second dragging a box trailer too but un hook it and might run a 9, don't temp 2Rismo, and circuit racing I am sure it would hit the walls a bit. He he.

Also mentioned was the ECU on the car tested. IT WAS STOCK. I can dig out the readings from dyno computer but I remember it was rich like all other Skylines but maybe not as rich as normal and I mentioned to the owner if he got a programmable computer or piggy back fuel controller it would make more power.

The factory plenum match ported and extrusion honed would also make more power but with common sense and theory from the experts such as Plasmaman, remember him, I think he knows his stuff this plenum will make more power. Again proven on our dyno and even if you factor in that it was possibly the best motor ever, although to clarify I belive it was only stock engien and not cracked open and STOCK turbo then this plenum must be good dont you think? It is not as if I am making some wild statement that makes no sense. It is good to debate and challenge and get input as long as we don't get tied up in debating ONLY. Keeping in mind 208rwkw is not a small amount more than it shold be comparing to others, as we have tested hundreds on Skylines over last almost two years now with a dyno and we know that a R33 GTS-T with the features it had only with stock plenum on 12 to 13psi should have made 160 to 170rwkw depending on intercooler and pipes, air filter, exhaust etc and condition of engine and turbo's etc and MAX maybe 185rwk and that would be a freak. Also the test car had stock cams and cam gear.

Lastly Skylinegeoff made some good points and I did not want to mention my zed too much on Skyline forum even though it has lots of GTR parts. Anyway yes it makes way more power than it should. Previous engine made 407rwkw on pump gas with octane booster only. Set up as circuit car and second time at drags on street tyres with worn and slow factory box ran 10.89 130.25 mph. This is with stock S15 turbo's inlet and exh manifolds extrusion honed and match ported all flow bench tested and evened out etc and lots of other mods to lighten drive train and more. This brakes big mind sets and thinking as according to what has gone on in USA where there are hundreds of thousands of zeds and lots of big mods and some in Australia they all think you have to have big expensive Gucci turbo's and exh manifolds. To answer that it probably would make more power with better parts and money thrown at it, but shows what you can do. Not all bolt on parts make more power but this one we are talking about does. My zed makes more power down low than ANY motor I have ever seen on our dyno or even heard about 200RWKW at only 3400rpm calibrated dyno to tacho. This is due to the fact of the plenum having long runners. Might lose a bit down low which I can afford but will make more up top. By the way I have a custom intake plenum coming with six 50mm throttle bodies and larger volume plenum as it will make more power. Grant at Performance Turbo's made it in Perth and I bought it at a good price. Normally big cost to make a zed plenum and very tight under bonnet as sits on the motor not on the side.

I aim to be the fastest all round circuit and drag car in Australia and chasing my mate Theo.

This new motor we just dropped in yesterday with bigger turbo's and more will get me closer.

[benm]

Bah stick the plenum on my car and do some testing. Car sits in the garage 6 days a week as it is

[Sydneykid]

Hi John, that's a looooong post. Maybe I can just clarify my thoughts on plenums and power in this one and get around to the other points later on.

The question is not "whether to upgrade the plenum on an R20/25", it is more a question of "when to upgrade the plenum on an R20/25". There are a couple of things to consider when making that decision;

A. What gives me the best bang for my dollar, will I get more benefit (maybe max power, maybe average power, maybe response) out of one part over another.

B. By doing this upgrade now am I compromising what I want to achieve (things like sticking a 250 rwkw turbo on if you are targetting 300 rwkw).

This is the order that I would do upgrades in ~$1.5K steps, if I don't want to open the engine (ie; stay under 450 bhp) on an RB25DET;

1. Cat back exhaust, Hi flow cat and engine pipe, that would be is my first ~$1.5K because on a turbo car exhaust is always first.

Standard power is 180 kw - 60 kw = 120 rwkw

Exhaust adds 20 rwkw, but is is an enabler for more power later = 140 rwkw

2. Next I would usually suggest a FMIC, there goes my next ~$1.5K. Throw in a Pipercross panel filter at the same time.

FMIC usally worth 15 rwkw + 5 rwkw for the filter = 160 rwkw

3. Once I have done those 2, I usually find the clutch isn't up to much more. So although, it doesn't increase the power, next is clutch. There goes my next ~$1.5K

Still at 160rwkw

4. This is where it gets interesting, if I want the turbo to last, then 10 psi is the max I can realiably depend on. But at this level of mods the car is running very rich, guzzling gas and not running "nicely". So I would go for a Power FC at this stage for my next $1.5K with a Z32 AFM.

The tune is good for 25rwkw = 185 rwkw

5. Now it's turbo time, if it hasn't already failed, then the ceramic turbine is in danger. So there goes my next $1.5K (maybe a little more depending on my choice)

Ball bearing hi flow adds 30 rwkw, depending on boost and injector duration = 215 rkw

6. This is were I usualy run out of fuel supply, maybe it happened even earlier and I kept the boost down till I could save up for injectors and fuel pump for my next $1.5K.

Maybe a little extra extra power because I can turn the boost up, say 15 rwkw = 230 rwkw

7. For me its camshaft time for my next spend of $1.5K

Tomei Poncams give me a good 25 rwkw = 255 rwkw

But it will need another tune at this stage and I usually pick up another 10 rwkw = 265rwkw.

That's my 450 bhp reached and I haven't done a plenum upgrade. If I look back over my list which one would I give up? Remember my target is 450 bhp and I am not going over that. Obviously I need the turbo, the standard one won't get me to 450 bhp. I need to tune the engine, so the Power FC is a must. It's not gunna get any power to the ground without a clutch. The FMIC? The exhaust? What do I leave out in exchange for the plenum? Shoud I not do the cams? Will the plenum give me the 25 rwkw that I loose from not upgrading the cams?

Note that cams are #7 on my list. The car John has used for his plenum test he has done it at #4 (assuming the car already has a clutch upgrade). This is before a turbo upgrade, but I wouldn't like running the standard tubo at 12.6 psi. The Power FC, but it's guzzling gas and has the usual annoying RB25 dip in the power band. I could go on but I think you get the drift, there is simply no room or need for a plenum upgrade in my planning.

I should point out that at this power the R34GTT did an 11.9 at 120 mph. And it hasn't been the only one.

[Al]

SK: I have actually followed the same steps with my car , but i have done the fuel system first, b4 the turbo, only because i was doing a few track days. At a later stage i will also put in the Tomie Poncams and port the head, b4 even considering the plenium. Even though it is far down the track a 3ltr bottom end, with preped internals, is on the cards. At that stage i will have to get a plenium, only because of the taller engine, hence the cross pipe needs to be removed.

Boosted Zed: That plenium is really a nice work of art and a top effort

My question though is, what was that particular car making on your dyno, on the same day, in the same conditions? No one can post "i have made ###rwkw, on a stockish rb25 with the addition of a plenium" and claim that the plenium was the cause of such a good figure. If the car had completed 3 power runs first(then calculate an average of the readings), then fitted the plenium and completed another 3 power runs, then and only then can anyone claim the benifits of the plenium.

Once again, a very nice piece of work and i am sure some ppl will purchase it just to improve the look of the engine bay, and if it does increase the power, all the better.

[Sydneykid]

SK: I have actually followed the same steps with my car , but i have done the fuel system first, b4 the turbo, only because i was doing a few track days.  At a later stage i will also put in the Tomie Poncams and port the head, b4 even considering the plenium.  Even though it is far down the track a 3ltr bottom end, with preped internals, is on the cards.  At that stage i will have to get a plenium, only because of the taller engine, hence the cross pipe needs to be removed..

That's not actually the case, I have personally seen 3 X R33 GTST's with RB30/25's and they had the standard plenum. I built 1 X R32 with an RB30/25 that most certainly didn't need to have the plenum changed. I did actaully use a Sub Zero plenum, but that was because I bought the RB25DE top end without a plenum (it was damaged in the accident in Japan).

So don't buy a plenum because you think it won't fit otherwise, buy one because you need it for the extra power that a forged bottom end RB31 is gunna make.

[discopotato03]

I reckon the $1500 is better put towards an RB26 top end with its competition style multi throttle inlet/plenum . You also get better cams / springs / valves/ solid buckets and no dramas onto RB30 block . Good value really .

[Boosted Zed]

Yes well anyone can get power with bigger turbo and more boost and stuff some more air in, but free power is removing restrictions and evening out the flow per cylinder. No you don't need to just a very good option. Benm or others if you want to be a test pilot before and after which will prove it we could do a deal with a guarantee. What will it be then the car was not the right colour or is the feeling we are not accurate or honest. Bold boardering on abrupt ( confident) but not dishonest and our testing is thorough.

Talking bang for buck though if you spend say $1500 on Power FC maybe cheaper plus tune $2k plus and engine and dump pipe and a genuine 7 litre high flow cat fitted another $800 assuming it has cat back ram pod and FMIC and end up with 175 to maybe 200rwkw max, although most are around 175 to 190rwkw on our dyno. This is usually with 13 to 14psi. Not 12 to 13 psi as per test car.

Or have less stress on the motor and run cooler and make same or more power for around $1500 could be cheaper plus fitting which would not be much, so?. I think that is bang for buck.

Sydneykid I take it you say it works and good but not necessary or better bang for buck?

How many Skylines have you seen with over 200rwkw with stock turbo I have only seen one or two. One was Sam RevitR33 I think his name here is and was around 205rwkw from memory and had everything including Power FC and it was pinging a bit on road or track or both as it was tuned to the max and had to back of some timing a bit.

Getting better flow such as free flowing exhaust, cams and porting including match porting, if you have engine appart, are all what I call free power as improves flow, and is less heat and stress, and this plenum is another. At UAS my I often talk to my staff and customers re mods referring to the saying. " Good is the enemy of better" Also, " Stack everything in your favour" As far as rules, if racing, or cost allows.

Maybe I should have said. Got this new plenum made by some guy called Plasmaman who reckons he is good. Stuck it on our dyno thing and makes more power than any other car and can't explain please help?

[Sydneykid]

Got this new plenum made by some guy called Plasmaman who reckons he is good.  Stuck it on our dyno thing and makes more power than any other car and can't explain please help?

If that car was on a dyno I was responsible for, these would be my questions;

1. It's running 12.6 psi which is more than I would recommend for a standard turbo. It is risking ceramic in the cat disease. Keep it at no more than 10 10psi.

2. What does the A/F ratio look like? If it is leaner than 10 to 1, it's got some tuning, either ECU, rechip or piggy back. Let's check it all out.

3. If the plenum truly reduced resistance, then the standard turbo wouldn't have enough airflow to hold 12.6 psi. Are we sure the turbo is standard?

4. What's the injector duration looke like? It should be around 80% at 5,500 rpm, If it isn't then its got some tuning, either ECU, rechip or piggy back. Or maybe fuel pressure up or injector swap. All signs of it not being as standard as we think.

That's probably the difference, I would cross off ALL of the other possible reasons for its good power result. If I couldn't find any, then I would look at the plenum as maybe the answer and do some primary pipe exhaust gas temperature testing. When i had finished that I would stick the standard plenum back on, touch nothing and see what sort of result the car gave. Then and ONLY then could I be confident that the plenum made any difference at all.

Over many years of racing I have learnt that you don't always get the right answer without ALL of the data.

[BU5TER]

Wha about just because it looks pretty

[GTRgeoff]

If the plenum truly reduced resistance, then the standard turbo wouldn't have enough airflow to hold 12.6 psi. Are we sure the turbo is standard?

Always a toughy but in considering, I was told mine was modified but doesn't look any different to normal. It makes 14psi then drops to 11-12 for 220rwkw peak at about 6k from memory.

Looking at this from another perspective, if the plenum optimises/accelerates flow then the restrictions in the system are reduced and some negated from compressor to turbine which I identify as one of the greatest restriction regions in the entire system, and this could allow that increased power level despite the other know power limiters.

Maybe one day I'll properly model the system but it's a lot of work just for the fun of it.

I have a theoretical exercise I undertake when on the design efforts we get involved in that may be useful to some of you, just modified for this case. Take the approach of the traditional upgrade path which works well and is proven, and then parallel it with realistic measures of what the maximums for each element are and what restrictions were to remain if that were the only thing done. Knowns of exhaust, intercooler, intake piping, throttle body, turbo, exhaust manifold, inlet runners, cams, valves, inlet runners, port matching. This can be a good way to identify items that may be limiting flow, which is all I'm looking at.

Consider also the turbo in isolation as well, just how much flow would it produce without the restrictions in between and what calorific value of fuel would be required to make it run to it's limit. Just the turbo, some piping and a burn can. In this way you can start to look at elements that can add to the system far beyond the accepted view held.

Airflow can be a really tricky thing to understand fully (and I don't yet!), and something might work in different ways when velocity is increased and the turbulent flow at the walls gets to a point called a drag bucket, where the reynolds number for drag reduces almost unexplainably by a large margin. Like the golf ball at a certain velocity so that suddenly it changes trajectory and flies further, due to the turbulent flow due to the dimples.

It may be that the standard plenum can flow at a predictable rate, a known in the industry, but someone comes up with a configuration that suddenly responds in a an unpredicted way that improves what we knew as gospel. If that can be repeated and marketed...Gold! And that's what I have one eye on here.

The ancient Greeks had a standard orifice for delivery of water. A cross section area for limiting consumption. It was discovered that changing the pipe size immediately after the orifice to increase at a 7 degree included angle accelerated the flow and partially overcame the restrictive diameter. There is also a particular inlet outlet shape that goes even further to accelerate flow, based upon a mathematical equation that I don't have at hand, but certain combinations can deliver a value greater than their individual parts.

Much baseline testing on a sample of cars should be done first to determine the total value of the mod but John is well placed to commence that.

All a bit eclectic but there may be a few points of interest there.

[Sydneykid]

Hi Geoff, good stuff, your brain is alive and well. But water and air do behave quite differently under pressure, ie; you can compress air, but you can't compress water. Lets try this real world example;

A. Measure the boost at the turbo. Measure the boost in one of the primary inlet runners (after the plenum has done its thing). The difference is the restriction effect of everything in between.

B. Then do the same only change the plenum. The difference is the restriction effect of everything in between.

Subtract A from B and you have the effect (+ or -) of changing the plenum, since everything else was the same.

Sound like a reasonable test of efficiency of the plenum?

OK I have done that with a Greddy plenum on an RB25, guess what? No difference, not 0.01 of a psi. There were however some issues with distribution under 5,000 rpm that showed up on the primary exhaust pipe temperature and A/F ratio readings. This resulted in sub optimal tuning and cost a handful of horsepower.

This is another test that could be carried out in addition to the ones I suggested above.

[GTRgeoff]

Yes, great test. Almost need a test engine on an engine dyno with every sensor conceivable on it. Tell me you have most of that in the dyno room too Alternatively the pressure may remain the same but the AFM may tell the story of increased airflow, so as you correctly pointed out earlier, all the factors must be data captured, understood and considered in relation to each other. Time, time and more time.

Unfortunately I can find myself spending hours "navel gazing", as our line warrioirs put it, while I think of new ways to outsmart myself. I do like to do a fair bit of theorizing before I start to swing the spanners as a few minutes of thought can save many foot pounds of effort.

I once even put a pressure transducer in a sparkplug, connected it to the departments data capture Libretto palmtop and logged the pressures in cylinder when I oxygen injected my Lynx. Very nasty peak pressures looking like impulse waves. but I digress.....

[Wazz]

when the R32 Plenums are made let me know.. i'll do a little test.. same dyno same day hopefully run the car with stock plenum than run than bolt on top half.. see wat differences are

warrick

[benm]

How many Skylines have you seen with over 200rwkw with stock turbo I have only seen one or two.  One was Sam RevitR33 I think his name here is and was around 205rwkw from memory and had everything including Power FC and it was pinging a bit on road or track or both as it was tuned to the max and had to back of some timing a bit.

Don't forget John only 3mths ago I did 198rwkw still with the std ECU and Turbo on only 9.5psi at the UAS dyno on a hot day (after driving 40mins too, no cool down time)

PowerFC, Z32 AFM and an AVCR would smash 200rwkw but no more is being spent on the GTS-t, it's GTR time !!

[Boosted Zed]

Don't forget John only 3mths ago I did 198rwkw still with the std ECU and Turbo on only 9.5psi at the UAS dyno on a hot day (after driving 40mins too, no cool down time)

PowerFC, Z32 AFM and an AVCR would smash 200rwkw but no more is being spent on the GTS-t, it's GTR time !!

Sounds like a freak you sure only 9.5psi. I should get my guys to dig out the run out of the computer. Had full exhaust also though.

[Lepperfish]

198rwKw on only 9.5psi sounds a bit far fetched even with a power fc let alone a standard ecu..

[benm]

Don't look at me, I get all my work done at UAS