I have to agree that you can have an up pipe diameter that is too large.
I also wonder if doubling the intake volume would cause any noticeable increase in turbo lag.

Since the y pipe is on the pressure side of the turbo you are blowing air through the pipe not drawing air through the pipe like an intake. So a larger diameter pipe might not be that great of a benefit in terms of hp gain.

Unless you are planning on 4 digit rwhp numbers i have a hard time believing any advantage from 2.5" to 3" pipe diameter.


As an example:
My turbo hayabusa made 520+hp at 26psi with a single 2" up pipe. A competitor did a 2.5 inch up pipe with the same turbo and did not make any additional hp.

I realize that the 996 is 3 times the displacement as the busa but it also redlines at half of the rpm the bike runs.

It would be nice to see a back to back dyno
test of the 3" pipe vs. 2.5"

 

^ or even better, flow tests of the stocker vs aftermarket solutions at relevant flow rates to see what the pressure drop difference is. I agree that, in theory, this seems like pretty high hanging fruit but may be necessary on extremely high hp cars.

You can run some basic calcs here: http://www.pipeflowcalculations.com/...drop/index.htm The theoretical difference between a 2.5" and 3" pipe going around a fairly tight 90 deg bend at 700hp flow rates (I used 40lbs/min per side) is around 0.1 psi, between a 1.9" and 2.5" diameter it's around 0.4psi. Assume a couple 90s and a couple 45s for a typical y-pipe and there isn't a whole lot of total head loss with either option.

There's a reason Chris Green was able to trap 146mph with the stock y-pipe without the world imploding

...just my .02

 

Interesting specs Earl. It would be interesting to see the pressure drop from stock, gt2, Evo and other ic's. I think there is more to be had by going to a more efficient IC than large pipe diameters.

 

Doesn't Dan's dyno showing an improvement in hsp and tq of >20 prove it does help...

http://www.vividracing.com/catalog/a...5-p-87480.html

That is on a car with GT28 turbos...(not sure of the flow rate).

I imagine it wouldn't help that much on a stock k16 but i bet it would be an even greater improvement on a car with a larger throttle body and aftermarket plenum.

 

I'd be interested to see boost & afr logs from these comparison dyno pulls (I would guess the pipe allowed boost to creep up a bit). I suggested the flowbench as an easier & more repeatable method of test since you can isolate the one component. but yeah, I'm sure it doesn't hurt.

 

20hp better than stock intake piping, i wonder what the hp difference is between the 2.5" and 3"?

Whatever the hp difference the 3" definitely looks cool!!

 

Its more about getting rid of the kinks... like at the stock intercoolers which are 1.8" at the connections.... rather then 2.5" or 3." piping from the TB to the ICs.... but thats just my opinion....

 

ding ding we have a winner !!! Mark hit the most important thing right on the head !!!

besides , robs car , marks own car , scotts old 996tt, put down crazy numbers with the very same diamete pipes .

hell scotts gt2 , my car and coreys put north of 700 to the wheels with these also.

 

First - Thank you Richard for your review and I cannot wait to see pics. Thanks to Bad107. Thanks to Markski and others for the input.

Techs always ***** no matter the experience. In fact even my own guys ***** about something that is new to them. Nature of the beast. But everything does fit.

The fact that this is to large of diameter, FALSE. Get rid of the kinks and go straight 3inch from the intercoolers, ypipe, and throttlebody and you have just improved your power and flow. Calculations have nothing on real world testing such as the Texas Mile, Dyno, 60-130. If you have a stock K16 turbo with no flash, no exhaust, no DVs, etc, this is not the product for you. Building a car is like putting together a puzzle. You must have ALL the parts working together properly.

Here is an installed one for people to see -

 

I can report that the car pulls like a train, never had chance to push but did see 1.5 bar.

 

What turbos are you running.

 

Billet K16's

 

What octane are you running?

 

98, nothing is going to blow

 

apart from the Billet K16's