Richard.

Ok so I have AWE Intercoolers and a 3 inch Y pipe both of which seem to make very little difference in the real world. Now on Cayman/Boxster GTS the first thing tuners do is change the Plenum for more air, whereas the consensus seems to be on a 996 TT it also adds little, is this simple a Turbo vs non Turbo issue ??

mcbit

My experience of forum anecdotal evidence is that there is skepticism regarding the efficacy of plenum use in NA applications whilst with FI applications the feedback is more positive.

I have no experience or opinion on the use in NA cars, but in my own 996t with 16/24 hybrids and a 1.1 bar tune, it is clear to me that rev range over which I experience max boost has increased significantly since fitting the plenum.

powdrhound

Stock plenum, 91 octane, 1.2bar

[url=https://flic.kr/p/vqFY49]

mcbit

I haven't done a dyno run on mine but before installation I used to get a brief peak of 1.1 bar during the run to max revs. Now it will run at 1.1bar from around 3,750 to redline and will continue at 1.1 bar through the (tip) gear change.

SteveMFr

Are you sure you rember this the right way around? Word from Porsche is the exact opposite: NA motors need all the help they can get in increasing induction efficiency, whereas on a turbo it does not matter as much if radii are blended or obstructions removed because the intake charge is being forced anyway.

That said, IMO the IPD plenum is snake oil on any Porsche motor.

Bruce Anderson said it best in his "911 Performance Handbook": making more HP with a Porsche motor is not easy because, in contrast to most automobile engines, Porsches come with relatively highly tuned motors from the factory.

If making extra HP were as easy as making the plenum runners curved, Porsche would have done it themselves.

CincyScott

Don't forget the dimples, those are important too. All kidding aside, there is probably a point in the horsepower chase where a larger plenum makes sense... Most of us just don't go that high.

32krazy!

if these statements were true you wouldnt be able to get 80+ hp from a simple tune
i went to a custom built plenum and 82 mm t/b to get as much air into the motor as possible. more air in more fuel can be used.

CincyScott

YOU certainly don't fit in the "most" category

A tune/exhaust kind of owner isn't going to see much lift.

"02996ttx50

my anecdotal experience using even the 68mm ipd plenum has resulted for me in more mid range torque which really improves the responsiveness of the car particularly when i need to wot up some steep hill after a hairpin uphill turn for example. as to top end no discernable difference that i can *feel* vs stock and i am also on hybrids 16/24's but pulls solidly and will sustain 1.3 @ 7200 rpm for as little time and room i get to enjoy that portion of the powerband..

but the ipd plenum was for me a decidedly certain improvement in mid range grunt over the oem plenum. bear in mind i also did NOT opt for the larger 74mm option and/or gt3 TB setup etc.

but i DID have to remove that sprint booster i got from you richard, much as i initially enjoyed it! lol. it was freaking out my old ecu somehow and i want to preserve my 1.1.5 cargrahpic tune or as long as as possible. i don't feel the changing of the throttle mapping the booster created was simpatico with my old tuned ecu.

so anyone wants a perfectly good sprint booster lemme know.. lol. sorry for the diversive thread swerve!

32krazy!

did the same thing with the mercedes i had. s/c v6 and use a larger t/b and plenum for better midrange. im not in agreement that you will see huge hp gains but ill take any increase i can get. btw the m/b was 400 rwhp

mcbit

Not sure if this was directed at me but I'm on the fence as to the achievable gains with an NA engine only because most of the vitriol directed at the IPD plenums is to my experience directed towards the efficacy when applied to NA engines. IPD say that they work others (and I understand the logic) say that the by nature on an NA engine it is necessary to harmonically tune the air intake to maximise airflow whereas with a turbo it is only necessary to smooth out any restrictions to the airflow.

I cannot add any weight to the NA arguments as I have no direct experience, but I can say that with the (also 68mm) plenum fitted to my 996 that the differences are blatantly visible not just opinion and butt dyno related.

Richard.

I guess you maybe need to change the intake manifolds as well with the plenum to get the full effect and maybe its simply indeed that it makes less difference on a TT where the air is already force fed vs a naturally aspirated car.

02996TTX50 - sorry the Sprint Booster didn't work out for you, I guess its most effective on cars which aren't already tuned.

SteveMFr

You could gain that much (percentage-wise) easily in a 930 as well by cranking up the boost, Steve. I was referring to mechanical parts such as heads, the plenum, etc.

Bruce Anderson was one of the most knowledgeable people in the Porsche industry. https://dedeporsche.com/2013/02/09/t...-feb-9th-2013/
Read his "911 Performance Handbook". He lived and worked mainly in the air-cooled era, but there is a lot to be learned from his book even for people into the later cars.

And it is not easy to pick up a lot of hp in a NA 911. And I don't believe that aftermarket parts are an improvement over stock in a large number of cases.

Yes, it was directed at you - sorry for not making that clearer.

Basically the word from Porsche was: in a turbo car, shape, smoothness, etc of the intake under boost was not of dire importance because under boost, the intake charge flows around obstacles, up hills, etc. So I was referring to the IPD's shape (and golf ball dimples) vs. the stock plenums t-intersection. Size is another matter altogether, tho.

The biggest reason most consider IPD's claims to power bogus is that, in all the years they have been on the market, not one objective, back-to-back dyno test was performed that conclusively shows performance gains. Why? It is not that expensive and not that difficult.

One of the most renowned German tuners, Reinhold Schmirler of RS Tuning, tested the IPD on a 996tt and showed a loss of hp - not much, but still.

Sorry, not buying it. But there is not much point in us arguing either, as both of us are in the same boat as IPD - unless you have data logs before and after... Seriously, I would love to see some real evidence.

Richard.

Is IPD the only manufacturer of larger Plenums for the 996 TT ?

CincyScott

I think there's another one from RS out there, but certainly not the following like IPD.

I also think they really took a beating in the beginning because of quality issues with leaks and the like. Those certainly aren't going to help with hp gains. I've also read of folks who have taken them off and noticed drivability improvements, but again it's all anecdotal until someone puts a bunch of back to back tests together.