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I've recently found the limits of my turbos (Older alphas, gt2871R). I'm getting about 600 whp out of them on a mustang dyno. However, as you can see from the picture- they just can't make the boost in the top end. They're "out of steam". IAT haven't risen, so its not out of their efficiency range, just out of flow or restricted.
From personal experience, what is a good way to free up, or help the top-end flow? I'm about to do the 997tt throttle body, but I'm skeptical of the IPD plenums.
I can't imagine a 30whp gain from the plenum on a stock car, it just sounds ridiculous. That should be 60whp on my setup... I know that isn't possible.
Worse case scenario I upgrade the turbos, but I'd like to look into freeing up some top-end first! I have catless 3" exhaust, gt2rs intercoolers, and fender intakes, so the pre and post-engine restriction is low.
im sure with your setup you're talking the larger 74 ipd plenums, but i am not imagining the increased low end tq even from the ipd 68mm with the oem gt2 tb. it's how the airflows and the less restrictive design which i believe is responsible for the increase felt with the ipd vs stock. i have no experience with the larger one, and i also am dubious about any claim of 30 whp!? but there is NO question that there is an increase down low and mid rpms, just where i wanted it. pretty sure it's a torque curve kinda deal though. rather than a straight up hp increase, although SOMEthing favorable is going on. of that i am certain. also, all ya gotta do is LOOK at the stock plenum vs ipd's and you can SEE what's going on and understand it's how the LESS restricted the air getting thru the intake, that is making the "difference".
believe me, when i say it's not a i.e. "bmc/k&n air filter vs stock" kinda proposition! lol
i'm old, and my imagination just isnt that vivid any more.
I'd bet you can free up some intercooler restriction. The gt2rs ones are a good bang for the buck assuming no leaks, but they aren't "the best" for flow.
i am not imagining the increased low end tq even from the ipd 68mm with the oem gt2 tb.
The OEM throttle body on the 996TT/GT2 is a Boxster 986 throttle body... In all these years, I've not come across anyone that has done a back to back dyno comparison of the IDP v. OEM TB, all other factors being equal. All you hear about are seat of the pants numbers which unfortunately don't mean a whole lot. Plenty of posts by the 997TT guys actually claiming losses. Heck, even the manufacturer mysteriously can't mysteriously do a apples to apples comparison and instead posts some dubious charts from runs on different days. Makes you wonder... Not knocking the IDP plenum, just saying.. Too bad you never did a same day before and after dyno run on your car Mark. You had a perfect opportunity to do so before installing it. Would have been interesting to see.
I looked at the IDP plenum during my rebuild as it's certainly very cheap in the scheme of things, and after talking with numerous knowledgeable engine builders I was advised to skip it. I really really actually wanted someone to endorse it as a "claim" of cheap HP is tempting. I do however understand why the OEM plenum is made as a "T" instead of having the little diverter at the back of it. Porsche didn't skip it because they were cheap... Some engine builders have even used the IDP plenum but cut the diverter out of it and welded in a smooth back wall replicating the OEM plenum.
Last edited by pwdrhound; Apr 16, 2015 at 04:59 PM.
How big is your Y pipe ? I wouldnt touch the ICs and TB for now, if I read the graphs right you run 1.5bar and consider the gt2rs with similar turbos runs 1.5bar, also I was able to get easily 820whp on stock TB and didnt get to the limit, only 1.65bar
Injecting meth will make your Y pipe even narrower, take a closer look. try to use racegas only without meth and see if any difference
What exhaust do you run? This might be another limiting factor
Maybe would be a good idea to share your full setup
All I'm saying is if you are already running meth, you can sacrifice some intercooler cooling capability and run some that flow better and it will open up top end.
Doesn't mean it's the only way to do it, just one way.
The OEM throttle body on the 996TT/GT2 is a Boxster 986 throttle body... In all these years, I've not come across anyone that has done a back to back dyno comparison of the IDP v. OEM TB, all other factors being equal. All you hear about are seat of the pants numbers which unfortunately don't mean a whole lot. Plenty of posts by the 997TT guys actually claiming losses. Heck, even the manufacturer mysteriously can't mysteriously do a apples to apples comparison and instead posts some dubious charts from runs on different days. Makes you wonder... Not knocking the IDP plenum, just saying.. Too bad you never did a same day before and after dyno run on your car Mark. You had a perfect opportunity to do so before installing it. Would have been interesting to see.
I looked at the IDP plenum during my rebuild as it's certainly very cheap in the scheme of things, and after talking with numerous knowledgeable engine builders I was advised to skip it. I really really actually wanted someone to endorse it as a "claim" of cheap HP is tempting. I do however understand why the OEM plenum is made as a "T" instead of having the little diverter at the back of it. Porsche didn't skip it because they were cheap... Some engine builders have even used the IDP plenum but cut the diverter out of it and welded in a smooth back wall replicating the OEM plenum.
john, i had NO oportunity to dyno my car before/after, and i can't argue that seat of the pants is the least comprehensive or even measurable method of determining a difference felt. i mean, we are all aware of the phenemenon of everyone heaping praise upon whatever mod they just did, perhaps in some subconscious hope that believing it "helped" will make it so! lol.
but man, i've been driving stuff a looonng time. so you'll have to give me the benefit of the doubt ( or i'll ask you to? ) when i tell you that there was a distinct low end/mid level increase mostly in low end "grunt" which while not it's technical term? i tend to associate "grunt" more with torque, than actual. HP. perhaps why i also question ipd's numbers as i'm sure you've noticed! i mean 30 whp in their white papers? ok, could well be a "stretch"! though i think if you surveyed those that have done it, against those that have not. you'd find more that say it increased "something". whether or not it simply made their pants fit more tightly in the crotch? isn't even the point. it works, and i'm tellin ya it does. believe me, or not.
btw.. i wasn't talkin up the oem TB either, the fact it came out of a gt2 and is as you say the lowly 986 part? as well as oem 996? it was more to illustrate the point as to how i paired the part, and that is was quite sufficient to my needs. the little bits i've added are time honored john, you'd be surprised how quickly this little thing gets on down the road.. and the ipd helped.
Last edited by '02996ttx50; Apr 16, 2015 at 05:37 PM.
Some engine builders have even used the IDP plenum but cut the diverter out of it and welded in a smooth back wall replicating the OEM plenum.[/QUOTE]
This is a good answer......the oem t Plenum design force the pulsation between the to banks at high rpms
The diverter at the ipd plenum give a advantage down low and mid range power but not at high rpms, because it reduce the pulsation between the two banks (left and right)
Wy not use the T Plenum from Vivid Racing and have both /pulsation and a greater TB ? I will give them a try these days
Also a 82mm Version is available but not shure if that have a advantage
Last edited by winnigt2; Apr 16, 2015 at 07:22 PM.
john, i had NO oportunity to dyno my car before/after, and i can't argue that seat of the pants is the least comprehensive or even measurable method of determining a difference felt. i mean, we are all aware of the phenemenon of everyone heaping praise upon whatever mod they just did, perhaps in some subconscious hope that believing it "helped" will make it so! lol.
but man, i've been driving stuff a looonng time. so you'll have to give me the benefit of the doubt ( or i'll ask you to? ) when i tell you that there was a distinct low end/mid level increase mostly in low end "grunt" which while not it's technical term? i tend to associate "grunt" more with torque, than actual. HP. perhaps why i also question ipd's numbers as i'm sure you've noticed! i mean 30 whp in their white papers? ok, could well be a "stretch"! though i think if you surveyed those that have done it, against those that have not. you'd find more that say it increased "something". whether or not it simply made their pants fit more tightly in the crotch? isn't even the point. it works, and i'm tellin ya it does. believe me, or not.
btw.. i wasn't talkin up the oem TB either, the fact it came out of a gt2 and is as you say the lowly 986 part? as well as oem 996? it was more to illustrate the point as to how i paired the part, and that is was quite sufficient to my needs. the little bits i've added are time honored john, you'd be surprised how quickly this little thing gets on down the road.. and the ipd helped.
Not knocking it at all brother. Just wish someone would do a real before and after comparison to disprove the skeptic in me.
Not knocking it at all brother. Just wish someone would do a real before and after comparison to disprove the skeptic in me.
i hear ya man, and i'm one of the few guys not ever needing more up top! so, i think winningt2's post here which also supports your views while at the same time explaining quite well, the reasons it works for me as well as where i "recognize" the "gains" it's no more "scientific" than before, but if you drove my car and a/b'd them? you'd feel it too.
Originally Posted by pwdrhound
Some engine builders have even used the IDP plenum but cut the diverter out of it and welded in a smooth back wall replicating the OEM plenum. )
Originally Posted by winnigt2
This is a good answer......the oem t Plenum design force the pulsation between the to banks at high rpms
The diverter at the ipd plenum give a advantage down low and mid range power but not at high rpms, because it reduce the pulsation between the two banks (left and right)
makes sense to me, even with my addittedly highly limited knowledge of how or why it "works", again, only that it does.
john, you'd feel the difference btw 2000k and 4k i'm sure hell, you feel the difference in the most minor of details i'm sure, given how and where you run your car. but i'm telling ya.. that 700 bucks for that ipd was bread well spent
What's been done on the intake side of this car other than the GT2/RS intercoolers?
If you REALLY want to do this right and believe it's a flow issue somewhere start sticking in some temporary pressure and vac gauges. Put a vac a few inches before the turbo intake, put a pressure gauge before and after the intercooler. This will tell you pressure drop at the intercooler and it will tell you if your intake tract to the turbo is restrictive. I'm betting that BOTH of these show issues! I'm not sold on the IPD nor the larger TB honestly, not at that level but I'd love to be proven wrong. You say IAT isn't rising but that's running meth right? My understanding is that the stock intercoolers are pretty bad, I'm betting the other OEM units aren't too far behind.
You can just throw parts at it too but I think finding the restriction would be cheaper. What are your ultimate goals?
How big is your Y pipe ? I wouldnt touch the ICs and TB for now, if I read the graphs right you run 1.5bar and consider the gt2rs with similar turbos runs 1.5bar, also I was able to get easily 820whp on stock TB and didnt get to the limit, only 1.65bar
Injecting meth will make your Y pipe even narrower, take a closer look. try to use racegas only without meth and see if any difference
What exhaust do you run? This might be another limiting factor
Maybe would be a good idea to share your full setup
How is the methanol restricting anything? I don't understand that.
My Y-pipe is stock, but tapped for the methanol jets.
My exhaust is a full 3" x-pipe with no cats. Its not restricting at all.
Here is my full mod list:
- Protomotive Mafless tuning
- Tial Gt2871R Turbos
- Gt2RS Intercoolers
- Aquamist Methanol Injection spraying 20% of fuel flow as 100% Methanol
- Walbro 450L/h Fuel Pump
- Evo 10 BOV (works great)
- Custom 3" Fender-intakes
- Catless 3" X-pipe exhaust
Freeing some top-end?
) when i tell you that there was a distinct low end/mid level increase mostly in low end "grunt" which while not it's technical term? i tend to associate "grunt" more with torque, than actual. HP. perhaps why i also question ipd's numbers as i'm sure you've noticed! i mean 30 whp in their white papers? ok, could well be a "stretch"! though i think if you surveyed those that have done it, against those that have not. you'd find more that say it increased "something". whether or not it simply made their pants fit more tightly in the crotch? isn't even the point. it works, and i'm tellin ya it does. believe me, or not.
