B-Man's Excellent Engine Adventures

[Steve]

Problems with plenum.

1. what was described was not delivered, no bell mouthed runner, throttle body didnt fit, plenum sits too high to do a 3L conversion which I also asked if it would allow clearance to the bonnet for this.

2. welds were actually quite poor, some places looked like it was close to burning through, and I had it re welded to be safe.

3. i was originally told they would fit their plenum for $895 and do a ford throttle body for an extra $200 fitted. When I asked for a price for plenum and throttle body ready to bolt on (i am in a different state) the throttle body delivered was a second hand ford explorer one, it didnt fit on to the plenum (it was made to fit stock TB) and the TPS was the stock ford on/off affair.

Didnt really appear to be good value for money IMHO

PLUS

They did not deliver what was promised.

Bottom line, cut the top off your stock plenum chamber, weld up a new one with holes at the front for a new tb and radius the runners - $895.

I wanted a good plenum, I was expecting to pay up to $1500 new, so when mark told me how good his are I thought great, but bottom line is it would have been cheaper, quicker and easier and just as effective to have the throttle pos moved to the front and bored out the top of the runners myself - same difference.

[T0nyGTSt]

Before you get too excited about the Greddy plenum, I have seen test reports of it and it's less impressive flow wise than you'd expect. BUT it is best of the breed and it won't 'blow motors', is it worth the $1,800 AUD RRP??? Maybe.

But for $1,100 or so? Quite possibly.

Oh. btw, Brendan. I started my car TODAY! First time in months. First shot, sounds ok from the outside. I was tailing it as my mechanics were test driving it. Not so bad actually. Quite a horn sounding car (I've never seen it being driven!).

Anyway the rebuild has started

T.

[B-Man]

Good stuff Tony - I am only weeks away from starting mine.

Approx $1000 for the GReddy plenum - Greenline or Nengun = I got to get something cause my stock plenum aint no longer.

[Sydneykid]

Hi guys, we have a rule, on RB20's and RB25's if you are not touching the insides of the engine, then leave the inlet system alone. The standard internals are good for around 450 bhp (280 rwkw) and the standard inlet manifold, plenum and throttle body will all easily do that.

More importantly I have yet to see an aftermarket plenum make more average power than the standard one up to 300 rwkw. That includes plenty of both brand name and backyard specials. Plus all of them show serious leaness in the rear cylinders (6 & 5) that requires correction at all power levels.

Don't fall for the "pipework is shorter, therefore better response arguement". The ones we have used loose so much mid range power that any gain in response is lost there anyway.

Bottom line, if you are upgrading the internals (rods and pistons) then an aftermarket plenum may be worth it, just be very careful of the A/F ratio distribution and tune for it.

Hope that helps

[B-Man]

So, standard plenum goes back on , re-route the cooler piping and bob's my uncle - Sounds too easy ?? Well, I know it will be a shit load cheaper than buying a new plenum/inlet manifold.

Thanks Sydneykid !

[JimX]

I gained power from my cooler and plenum upgrade, but I don't know if I would have gained more if I had kept the factory plenum. I have a better throttle response regardless and the bay looks a lot neater to me IMO. It's also easier to run top-fed injectors. I can't see myself going back to the stock plenum anytime soon.

Edit: I got my plenums mixed up.

[R31Nismoid]

mmm... i'm making over 200rwkw now, no problems with response... i've got a bit of lag but that IMO is turbo not plenum

The only way to test would be to bolt up a plenum (GReddy or whatever) and then get it back on that day for a dyno run...

anyone in VIC have an A/M plenum lying around for a REAL-TIME testing to settle the debate?

[Ronin 09]

I have a Greddy plenum coming from Greenline, should be here in the next 2-3 weeks. Additionally this FMIC is going on:

http://www.skylinesaustralia.com/forums/at...=&postid=484095

with custom piping, retaining the stock throttle body.

Last is a Profec B spec II.

If anyone has a rwkW difference when just adding a FMIC could they post up the difference; in theory (if) any additional rwkW gain should be attributed to the plenum?

The only current mods are a turbo back Trust exhaust, Trust Airnx filter.

I'll be posting before and after dynos.

[DoughBoy]

Aftermarket plenums make very little difference with outright power figures with under ~250rwkw. Not enough airflow to max out the standard manifold.

The basis for this comment is dyno'ing my R33 with a Greddy plenum, vs. an R33 with standard intake manifold. Same workshop, same tuner. Ok they weren't exactly the same induction setup (HKS 2530 vs 2535, different frontmount) but they were close enough that it shouldn't matter (intercoolers were ample for the task, both had uprated fuel systems, PowerFC's, tuned conservatively rich, 1 bar on both). The mechanic was surprised that such a beautiful and expensive item did not make 400rwkw on it's own. There is some more power to be made by adding the larger throttle body too.

Changing plugs is a different matter. As for response, that's going to be a seat-of-the-pants type experience that is difficult to measure properly... I could have sworn I gained throttle response by adding stickers though. All good in theory, does anyone have a realistic way of measuring this?

[Steve]

After having a chat to Evan (PSI Fabrication) last night, he is interested in testing the difference between the stock plenum and one of his custom plenums. So looks like I will be upgrading the hills thing sooner rather than later:D

The hills one would probably be ok for someone with stock turbo that isnt chasing much more than 200ish rwkw, but I really doubt it will provide the goods once bigger turbo and extra boost is wound in.

Will be doing before and after dyno runs to compare so he has concrete evidance of any gains to be had with his plenum design. I will probably try and get a comparison run between the hills one as well. Should be interesting.

[Ronin 09]

steve, keep us posted.

[B-Man]

Yes please Steve, I am VERY interested. Do you know when this will be happening ?

Cheers,

[Steve]

I hope it will be in the next month, but more realistically in the next two, cos Evan is always so bloody busy and he is a one man show.

After pulling my hair out waiting for him to finish the turbo install, I have decided that it is more than worth it - he is an artist.

Hopefully I will get some pics soon, and a preliminary dyno tomorrow - preliminary cos I still have cams and gasket in the garage waiting patiently. Looks like they may have to wait a bit longer, as I dont want to fit them and start the real tuning until I have this plenum sorted:D

I'll definately let every one know when its done. Should be interesting if the old 'aftermarket plenum makes no difference' theory could be disproven.

[BOOSTD]

Sydneykid: Have you ever seen lean out on 5&6 with the standard plenum at the 250rwkw mark??

[Sydneykid]

Hi Boosted, I have never seen lean out with a standard plenum at any power level that I could attribute to the plenum. Whenever I see one or two lean cylinders on an RB20/25 it is always the injectors.

As for the standard throttle body on the flow bench it shows no discernable resistance to flow at 50 lbs of air per minute. Thats enough for almost 500 bhp, so I wouldn't bother changing the throttle body until the engine internals are upgraded.

Hope that adds to the information pool.

[Gradenko]

Originally posted by Sydneykid

Don't fall for the "pipework is shorter, therefore better response arguement".  The ones we have used loose so much mid range power that any gain in response is lost there anyway.

However given a fmic, a properly sized front entry plenum (not 5L+ on a stock turbo) with standard throttle body will almost certainly improve throttle response. At least, thats the setup I'm moving to this week, so I'll see how it does.

I don't understand all the praise towards the stock plenum. Internally its design isn't anything special and cyl 3 &4 are far favoured over the rest. I have tell tale heat marks on the middle injectors which suggest those cylinders running hotter (leaner) than the rest. Not the most scientific of tests, I know , but its what I'd expect given the stock layout of the plenum.

[B-Man]

Well, this weekend I pulled the turbo off - thanks to Jim and a few squirts of WD-40 - And some patience.

I didn't even break anything.... amazing.

The turbo seems to be is good nick - no shaft movement - no bent or damaged turbine fins. So I'm happy about that.

Here's some pics:

[B-Man]

Can anyone identify this label ? ie what does it mean ?

Time for another beer !!

You guys don't know how much fun and free beer you are missing out on !!!

Stay tuned for more adventures next week - when I try to remove the damn intake manifold off the head - I'm porolly doing this the long and hard way - as I've not pulled any bit's off a RB25 before - Anyone got any tips ????

Cheers,

[Ronin 09]

B-Man, at the risk of sounding stupid, what is your turbo again? Is it a highflow standard? VG30? and what rwkW were you making before the bang?

[B-Man]

It's meant to be a Stage 2, GCG 500 HP Hi Flow jobbie. Performance core, and steel turbine instead of ceramic.

I can tell it does have a steel turbine, but FIIK if the core is performance and it's actually a Stage 2 500HP unit ?

I'm sort of hoping Sydneykid et al will be able to identify it for me.

I was getting 240rwkw before the bang....

Oh and BTW - no such think as a stupid question - I ask them all the time