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Tuning With Aftermaeket Plenums


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I have a plazmaman plenum on my RB20 and the results were a bit disappointing. I simply have not been able tonmatch the std plenums performance let alone realise a gain

I was thinking on the weekend, we have not played with the cam gears from when it was tuned with the std plenum. I still have std cams. Do you have to change the cam gear settings with a plenum, or do people typically still run 0 on inlet and retard about 4 deg on exhaust?

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So what are your cams degreed at currently? ie. does it have adjustable gears

Also did you expect a performance gain in some way, or accept it as a cosmetic tart up or a means of easier access to injectors, shorter pipework etc?

That aside, I wouldn't think you'd necessarily end up with lower outputs.

Edited by Dale FZ1
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Runner lenght is what its about, apparently, been told that my runners on my GREEDY (china spec) plenum are not as long as the tuner would like and I would make better power/response with my old standard RB25 one.

This is info that I gleened whilst listenening to my tuner going on about velocity and power and stuff which I didnt really understand but it sounded like tech secret stuff about stuff.

Makes sense though as the same issues with runner lenght on exhaust manifolds are used for moving the power and tourqe around, or something like that, LOL.

pinch.gif

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doesn't the plazman just bold onto the standard runners? I'm planning to put some cam gears on RB20 to get some more low down power with the RB26 ITB's

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doesn't the plazman just bold onto the standard runners? I'm planning to put some cam gears on RB20 to get some more low down power with the RB26 ITB's

Half the standard runners

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I'm not surprised to be honest. much shorter runnes. usually when going shorter runners the diameter is increased to aid top end. but in the plazmaman set-up you retain half the standard runners so you now have shorter runners (less midrange) and no diameter increase (no top end benefit either). so it's kind of the worst of both worlds. the only advantage is the simple pipework and easy access etc but I thought your old set-up was money anyway.

by all means try the cam gear tuning. there's no doubt the plenum has changed the power curve and tuning with the cam gears may have some benefit again.

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So what are your cams degreed at currently? ie. does it have adjustable gears

My cam gears are 0 on inlet and retard about 4 deg on exhaust.

med_gallery_462_50_44142.jpg

As you can see its slower to ramp onto boost, loses a fair bit in the midrange...but holds on top a bit better. It also seems to take less ignition then the std plenum.

Based on what other people have quoted on pages of this forum, i didnt really expect to make more power, or care to make more power. The talk is I could expect 200rpm or so increased response, which I was hoping to get another 15rwkws or so 4,500rpm to help with 3rd gear corner exits at the circuit where at present I just have to wait a tad to get onto power band. You can see from about 1:12 to 2.00 that there are 3rd gear corners where I just need a little more jump out of the corners. ...http://www.youtube.com/watch?v=gOl-IGx8UkQ ... (especially at 1.39 and 1:50)

I understand all the fluids of inlet manifolds reasonably well. But with so many people say raving about their performance increase, some even say same power at less boost...I thought I would give it a go. But much like my change from a Greddy exhaust manifold to a 6boost manifold did nothing to improve performance (most things point at I lost a little bit of response) it seems that I can get the same performance increase with the plenum as others.

So, before throwing another $200-350 at the tuner to try different cam gear settings, thought I would post up to see if any oen has tried a Greddy plenum, plazmaman plenum or other which has meant the proven I=0, E=-4 deg recipe for cam gears is different with an aftermarket plenum.

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Bris - I know this isnt really related to cam gears, and it costs money.

But have you thought about pulling the head off and having the ports tickled?

Wouldnt need much, and I wouldn't go any larger in port volume, but I have no doubt there are REAL gains to be had with a bit of a grind, espesially on the exhaust side of the 20 Head.

I would leave the standard cams as you are making power right through to the rev-cut, so unless you want another 1000rpm on top (which the 20g won't allow) I would definately leave the standard bump sticks, and as you found the the Apexi (I think) cams you went backwards.

If you do want cams + more mid range, have a look at getting some custom cams ground, with a smidge more lift and LESS duration than standard.

Anyhoo, hope you get it sorted :)

Andrew

Quick Edit -

Bris, That little RB20 is making something like 210-220hp/L

Pretty good when you think of it like that.

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when i went from standard plenum to greddy copy plemum i lost a little in midrange but gained an extra 10 rwhp. Response was almost identicle .This was with stock turbo, front mount ic,3inch exhaust ,power fc etc.

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Bris, That little RB20 is making something like 210-220hp/L

Pretty good when you think of it like that.

LOL, had never even stopped to consider that. Not bad for a std motor I suppose:)

Re head work. I may pick up a std head and give it a go myself. But honestly, by the time i buy new head gasket, head bolts, new timign belt, coolant, sump of oil etc even trying to do a head clean up on the cheap will cost $500-800. :(

Will try some headwork if nobody buys my Tomei 2.4L gear soon as the combustion chamber needs to be opened up to suit the bigger bore :) And re cams, I have something sorted since i have Tomei solid lifters and Tomei valve springs to suit :) But dont want to spend any money really, the power is enough, just trying to see what i can do to get the most out of std 20. I understand some of the myths out there about parts, thought these two parts were going to work for me. So far doing accurate back to back the 6boost has been nothing but a backwards step as it cost me money, the Turbosmart gate doesnt sound as good as the Greddy gate ( :) ) and and didnt deliver any performance increase over the Greddy manifold. It may prove to last longer though. And the Plazmaman, well ... yeh well. Seems to work on some other setups, just not mine :)

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I reckon flog the 6boost mani (should be easy, plenty of market for them), flog the turbosmart gate. refit the trust mani and trust gate (both of which worked perfectly with teh trust turbs). then look at going back to a stock plenum. for response it will be hard to beat. and it did sound pretty sexual too.

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as far as going cams to get response I don't reckon it'll work. cam gear tuning yeah, but new cams I think will only shift the powerband higher again unless you stick with the same or less duration which I think is probably a waste of time too.

cam gear tuning might help solve the current deficiency.

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try winding some inlet advance into it, say +2. From memory the RB20 has 7deg overlap, your settings bring that down to 3 deg. But every engine is diferent, and ther is no set standard....bla bla bla

I'll be trying some diferent cam on mine in the near future.

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as far as going cams to get response I don't reckon it'll work. cam gear tuning yeah, but new cams I think will only shift the powerband higher again

Thats only if you overcam it for the setup, most "street" Kelfords boost midrange and top end with no noticeable loss of downlow. I think the Plazmaman manifolds seem to rely on big bites of air being taken by the engine, even stock RB25/Rb26s loose some in the lower flow areas with these kinds of manifolds. Is the volume/runner size the same for the RB20s as the RB25/26s?

I'd consider using a manifold like what RIPS make which use the stock runners but with a bigger plenum volume to try and drag things back into parity with the standard "bites". I wouldn't have thought the 6boost manifold would cost anything in response, I know of people who have gone GReddy to 6boost and gained everywhere.

Thats my feeling anyway, could be complete BS - but unless I was intending on building an RB20 to rev way beyond the normal RPM range I'd centre my attention on the mid/top end area.

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I reckon flog the 6boost mani (should be easy, plenty of market for them), flog the turbosmart gate. refit the trust mani and trust gate (both of which worked perfectly with teh trust turbs). then look at going back to a stock plenum. for response it will be hard to beat. and it did sound pretty sexual too.

+1 :D

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Marlin has my old setup in a box...it is tempting but truth is i would rather spend the money trying some other combinations using parts i have laying around. Wish i had free access to an engine dyno

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So, before throwing another $200-350 at the tuner to try different cam gear settings, thought I would post up to see if any oen has tried a Greddy plenum, plazmaman plenum or other which has meant the proven I=0, E=-4 deg recipe for cam gears is different with an aftermarket plenum.

cam gear tuning might help solve the current deficiency.

I'd say that your particular setup is a different combination to others, so it may prove that the only test is to plump for an hour or two of dyno time to prove it. Mind you, it is pretty simple to at least road test the difference between current, and then advance the inlet a couple of degrees. It will probably be noticeable, as I found while trialing my own setup.

have you thought about pulling the head off and having the ports tickled?

I have no doubt there are REAL gains to be had with a bit of a grind, espesially on the exhaust side of the 20 Head.

by the time i buy new head gasket, head bolts, new timign belt, coolant, sump of oil etc even trying to do a head clean up on the cheap will cost $500-800. :(

So far doing accurate back to back the 6boost has been nothing but a backwards step ... and didnt deliver any performance increase over the Greddy manifold. It may prove to last longer though. And the Plazmaman, well ... yeh well. Seems to work on some other setups, just not mine :)

I'd tend to agree that a cleanup of the ports will help, but again cost is the factor. A bit hard to justify the cost for something that may give you 10hp - chasing diminishing returns. Different if the engine is apart and you've got the time and tools.

Seems that the trapping efficiency in the chambers is different with this particular inlet/exhaust/turbine combination and it just needs time and a capped amount of $$ spent establishing what it likes for cam timing.

Where exactly was the ignition timing wound back, and why? Did the thing knock? A couple of degrees taken out will easily cost you the loss shown on overlay.

Side issue; I much prefer to look at the torque curves, makes much more sense and in my view magnifies the differences between runs.

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