My custom Gt3 intake built by Billet Design

[strokher racing]

The turbo is a custom 74mm unit from Job Spetter. The wheels in this thing are not run of the mill so you can't compare it to another 74mm. This turbo has already made well over 1000rwhp which is alot for a 74mm unit. It would not hurt my feelings to max it out

[randywebb]

Good luck -- if you need to revise it, a flow bench can most of the non-resonant tests that a dyno can do for much cheaper.

[strokher racing]

It was not a new design. The intake is based on a gt3 so a flow bench is not needed Porsche took care of the majority of the work. Runner length and center section design are the main differences. The plenums are the same except for cleanup work. A flow bench would not do anything here.

[mattr_914]

The dual crossover is for the reversion flap, which is stock on a standard GT3 Cup. Some GT3 Cup engines have a big piece welded onto the back and the internals gutted out (an effective single crossover) for a little more power. GT3 RSR and DP engines both have ITBs (which is why TimT's manifold looks so much different).

What exhaust and cam are you running?

[strokher racing]

custom cams and headers also built by Marco. The center section on my intake is a very trick unit with internal diverters to smooth out the entrance.

[mattr_914]

Whoa, you're using a naturally aspirated intake on a turbo car? I'll be curious to see how this works.

[randywebb]

The cross-over might also function like the old-timey "balance tubes" on some motorcycles...


"naturally aspirated intake on a turbo car"

- This is a very interesting amalgam... we'll all be interested in the dyno results.

[strokher racing]

NA intakes are what most people use on turbo builds. 964 intake, 3.2 intake etc. This intake should be an animal with forced induction

[mattr_914]

I'm not saying it wont work by any means. But my understanding of cams says it will be a challenge to maximize the power. A cam works based on intake and exhaust pressure/velocity. I'm really a student to engines right now, so I'm curious to see what works that isnt written in a book or being practiced by Porsche right now.

[sewell94]

This intake is gonna be great for a boosted car. The people are doubting this havent seen one in person. It has large plenums and large runners, which are ideal for boost. The runners were shortened to help shift the power band to higher rpms. The dual crossovers help with volume. I'm thinking of ditching my ported 3.2 for one of these.
and on the note of cams, a boosted car loves overlap and high lift. There is this myth that u can't have any overlap blah blah. Alot of what u read and hear was true 20 30 years ago, things have changed alot.

[randywebb]

The dual crossovers help with volume.
- The vol. of the induction?

Has better engine mgmt. allowed greater overlap? If not, what was the change in the last 20-30 years?

[beepbeep]

This is not optimal design for turbocharged engine. Alla that resonance tuning stuff is just dead weight, especially if not connected or actuated by any device. GT3 and all...you would be as good with ordinary Carrera plenum or even better with custom made twin hi-volume-long runner plenums. Air that enters the throttle has to makee sharp 90-degree turn into each side of plenum. Balancing pipe doesn't do anything else but increases the volume of plenum.

This, on other hand, is optimal turbo plenum:



Boosted cars do not love lot's of overlap...it tends to blow out the charge trough the cylinders. It all depends on turbine size and amount of backpressure but lot's of overlap on turbo engine usually leads to inefficient engine with slightly more power.

[diabolos88]

holycrap Beepbeep, those are HUGE!

[Elombard]

I always thought the low overlap was ideal because ...just like beep beep says the charge would blow out the intake. I liked this because its intuitive. I think this is also the reason SC cams were a good upgrade because the CIS is so sensitive to intake pulses they have no overlap...ideal turbo cams.

Please expand on how overlap could possibly be good on a modern turbo engine - seems like you are fighting physics.

I am not doubting any one just curious.

[PorscheGuy79]

Originally posted by beepbeep
... turbo engine usually leads to inefficient engine with slightly more power.

Yeah, but then again what does Goran know? All he does it take pictures of the slow car him and his crew built.

[beepbeep]

Originally posted by PorscheGuy79
Yeah, but then again what does Goran know? All he does it take pictures of the slow car him and his crew built.

Even if it sounds confusing when I wrote "slightly more power", I do mean that hot turbocharged engines with lot's of overlap tend to have bad character and are not as responsive as correctly cammed ones, despite the possibility to extract the torque curve upwards in the rev range and thus achieve higher peak power figures.

imagine two engines: first dynoed @ 500hp with very flat torque curve and nice & predictable boost buildup and second dynoed @ 600hp with help of very aggressive cams but with peaky power curve and sluggish boost buildup. What you gain up top you loose longer down and sweet spot is often lower down than dyno-loving drivers believe. Of course, as revs go into strathospheric range, hi-overlap cams tied to correctly tuned runners will hit it's sweet spot and make more power than low-overlap, but this range is usually quite narrow and hard to use on circuit, unless you have CVT tranny tied to the engine.

The car equipped with first one would walk all over the other despite the lesser peak hp figures, thanx to it's better dynamic range.

It's swept area under power curve that matters, not peak hp figures.

[PorscheGuy79]

Originally posted by beepbeep


The car equipped with first one would walk all over the other despite the lesser peak hp figures, thanx to it's better dynamic range.

Goran, I think that engine design in this respect is WAY overlooked. Hot rodders so often try for high numbers rather than motors that are flexible and have a wide powerband. Damn you freakin Swedes know whats up. I would love to see the kind of stuff you guys build on your own time.

[sewell94]

hey now i didn't say lots of overlap. i've found that some over lap works well. To be honest i've found that cams with lots of lift with the overlap dialed out work very well. This is not always 100% true but i think most of it has to do with the fact that cams with lots of over lap tend to have lots of lift. I know this isn't porsche related, but i built an engine(honda twin cam) with cams that that had alot of overlap and high lift, we dialed out some of the over lap and made extremely good power for what it was. The tuner (who is nationally known) was didn't think the cams would work at all, he now says that they are his cam of choice for a boosted car. the cam is know as being an excellent NA cam. We also managed to make a t67 turbo spool faster than most 60-1's with the same turbine wheel and hot side are., i think that alot of that was also due to the large lift on the cam. I'm not just talking out of my ass here, i have a dyno so the engine i speak of was probably dyno'd for a good 40 hrs or so within 3 days. we tried every possible cam gear combination, when we dialed out all of the over lap the hp started to fall, maybe have been to the timing chaneg, and yes we changed the ign time each time to compensate for change. Another time we actually had turbo cams in an engine, and made more power with a stock cam, i personaly know that the low lift no overlap stuff is BS, it was true years ago but it was more due to engine management and tuning than it was the cams.
And to keep on topic, yes a large plenum is ideal, if u have seen erics intake, they have alot of volume. I'm sure the twin crossover work, if u look at alot of the boosted f1 cars(which i believe are more tech. advanced than most turbo cars that are built today) have crossover tubes. they were making 1000hp/liter over 20 yrs ago. Too bad most of there tech was destroyed and the secrets mostly gone forever.

[randywebb]

someday we will be able to open and close the ports when we want and as fast as we want...

think about it -- a lot of engine design and tuning is based on trying to deal with the above problem...