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Greddy Style Plenum Problem

Akis

By Akis,
in Engines & Forced Induction

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GTSBoy Grand Master

GTSBoy

Posted
Posted

Oh, I could design quite a good plenum. That's essentially what I do in my normal work. But I wouldn't trust it on an engine until I had done some reasonably extensive flow modelling (probably physical, using my wet modelling methods, or also dry with air and some very accurate and small pitot tubes, and maybe with some CFD), because I know how hard it is to make a compact plenum do a good job of making the flow even to all the outlets.

It's even worse with IC engine plenums. Because the flow is not steady state from the inlet to all the outlets all the time, they don't flow the same as steady state plenums. Half the idea of a plenum for an engine is that the volume of the plenum is shared amongst all the runners on a more than even basis, because it's not supporting evenly divided flow to all of them at the same instant. So whilst that is true, it's also not completely true, because the air has momentum and inertia and will keep flowing towards an outlet even when the inlet valve at the other end of the runner has closed. And then you get the pressure reflections and all that jazz which get in the way too. So the flow situation is some halfway position between the two extremes which means you really can't design from first principles without serious testing, with the final type of testing being on a real engine where you can monitor the effects on exhaust temperatures and so on.

I helped a guy design a plenum with internal ramtubes for a VG33DET a few years ago. It worked fairly well, but probably only because of the thought put into preparing the air flow as it entered the plenum after the throttlebody. Because VGs commonly (and this one in particular) have the air inlet at the rear and therefore it has to turn through a large angle to enter the plenum, getting even flow into the plenum required the use of turning vanes welded inside the bend. I don't have pictures of that plenum lying around, but oddly enough, I do have pictures of turning vanes in a plenum inlet elbow for an industrial application on a minerals kiln. You can see them in the back view and the cutaway of the elbow. This plenum is designed to overcome some big flow problems inside the kiln without actually aiming for even distribution to all the outlets. Looks like a bloody nightmare doesn't it? I hope it works properly - hasn't been added to the kiln yet.

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DVS JEZ Grand Master

DVS JEZ

Posted
Posted

Very informative thanks.

Im not after more power, i am happy with the current power but absolutely hate the look of the engine bay in the race car with the crossover pipe etc. was a budget cooler and piping setup built from leftovers, so i was after something nicer such as a ffp, considering Plazmaman which i know for a fact work great and make up to 20kw extra with no lack of response, but pricey for this car. Still is an option just looking for a cheaper alternative.

With the freddy does anybody have a graph that overlays the difference to stock plenum?

JustinP Mentor

JustinP

Posted
Posted

Has anyone ever tried one of these cheap chinese (or thai?!) items for an R34?

http://www.ebay.com.au/itm/R34-skyline-RB25DET-GTT-NEO-RB25-DET-intake-manifold-90-/170501510358?pt=AU_Car_Parts_Accessories&hash=item27b2ae94d6&_uhb=1#ht_4521wt_974

I've been tempted to give one a go but its only going to delay me finishing my build even more, and I would need to change intercooler and a few other bits :/

ARTZ Grand Master

ARTZ

Posted
Posted

thats not cheap its nearly 900$...may as well get a Freddy for 300$ or this

http://www.ebay.com.au/itm/Nissan-Skyline-GTS33-RB25DET-inlet-plenum-manifold-/350517307255?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item519c75a777

ARTZ Grand Master

ARTZ

Posted
Posted

Jex mate here is an extract from a convo i had with Fattony when i was thinking about the greddy install...

"330rwhp with Greddy

345rwhp with stock

Difference was the shape of the graphs. Greddy Straight linear line, like a highly strung N/A. Stock was a huge hump, massive mid-range flat-line at peak power from 5750rpm to 6750rpm.

I can't blame the Greddy plenum outright, but I do belive the shorter runners played a part.

Turbo is a 2835 ProS, I think boost came on the same with both plenums.

3rd gear, 21psi, 3500rpm.

2nd gear, 21psi, 4000rpm.

Felt much slower. Its all in the midrange. The extra power 4000rpm -> 6000rpm was the difference. Pedal response ON/OFF/ON throttle is probably better with the Greddy due to the shorter piping. It took some"

was enough to convince me anyway...maybe you could better tune your way around it i dunno...I asked Trent about it and he seemed very, meh whatever about it..:unsure:

JustinP Mentor

JustinP

Posted
Posted (edited)

How much did that cost you? And do they do one to specifically suit an R34 GTT?

I like the look of their design which is why I like the ebay one I posted up above.

The R.I.P.S front facing plenums have ram tubes inside them and they are known for their engine builds and power results... I was able to find one for my rb25...

Edited by JustinP
STATUS Grand Master

STATUS

Posted
Posted

Has anyone ever tried one of these cheap chinese (or thai?!) items for an R34?

http://www.ebay.com....1#ht_4521wt_974

I've been tempted to give one a go but its only going to delay me finishing my build even more, and I would need to change intercooler and a few other bits :/

Work well just need the mounting flanges checked for warps, one or two came through in the early days warped.
Frosty Grand Master

Frosty

Posted
Posted

Very informative thanks.

Im not after more power, i am happy with the current power but absolutely hate the look of the engine bay in the race car with the crossover pipe etc. was a budget cooler and piping setup built from leftovers, so i was after something nicer such as a ffp, considering Plazmaman which i know for a fact work great and make up to 20kw extra with no lack of response, but pricey for this car. Still is an option just looking for a cheaper alternative.

With the freddy does anybody have a graph that overlays the difference to stock plenum?

+1 for the plasmaman if you can justify the cost and lack of room in the engine bay....can provide some pics if you want

Tonks Community Regular

Tonks

Posted
Posted

Very informative thanks.

Im not after more power, i am happy with the current power but absolutely hate the look of the engine bay in the race car with the crossover pipe etc. was a budget cooler and piping setup built from leftovers, so i was after something nicer such as a ffp, considering Plazmaman which i know for a fact work great and make up to 20kw extra with no lack of response, but pricey for this car. Still is an option just looking for a cheaper alternative.

With the freddy does anybody have a graph that overlays the difference to stock plenum?

What engine do you have sorry if been said before, if you have a look at Roys build thread he tried a couple of plenums and I think he went backwards with the plaz on his rb20. Fair bit of helpful information in there for anyone looking at rb20 setups as hes had numerous different types

pipster11 Grand Master

pipster11

Posted
Posted (edited)

http://www.ebay.com....7#ht_942wt_1163

i was wondering how long it would take for these to pop up for rb25's

no where near the cheapness of the rb20 plazman ripoffs tho

Edited by pipster11
Ryno Experienced

Ryno

Posted
Posted

Another option is the MX Performance bolt on plenum top. Cheaper than Plazmaman, and in my opinion it looks better too. I've just installed this to my engine, after swapping out from a Thaliand JUN copy.

MXPerformancePlenum_zpsc0f6ad64.jpg

ARTZ Grand Master

ARTZ

Posted
Posted

your 740s maxed out..really ?..dunno where my 750s are at...how do we work that shit out I thought they would be ample for the task..

Cant wait to see how it goes cause I so nearly went there....still might if it proves worthwhile its a metre of piping I can lose...

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