I have 3.5 in exhaust with an x-piple going into the car next week, I'd also like to put in 3.5 in intake tubing with a custom MAF that i've seen some people on the forum try.

This is all pre work for the twin screw i'm going to order, but was wondering if there is going to be any challenges with the exhaust and intake? Could I go to 4in on the exhaust? Will i have backpressure issues?

I also worked out a plan with Hi Spec rotors to make a custom bell for their lightweight rotors cutting down 25lbs from the front rotors. If anyone is interested, PM me for details on those.

 

Not even considering the fact it might not fit, why would you go that large on the exhaust? 2.5" or 3" is plenty even for a twin screw.

Are you sure they can make rotors, even with aluminum hats, that are half the weight? It seems unlikely, unless using carbon ceramic.
I also asked HiSpec about their two-piece rotors and the weight they told me was only a couple pounds less than oem.

 

Got to agree on both points Steve highlights.

There's no real reason for that kind of diameter pipe unless you want a constant headache!

Andre runs a standard system with high flow cats, and pushes 600+bhp. Steve's car also runs a twinny - what's your widest point in the system Steve?

I've got 2.5" inner diameter sections going over the axle, any bigger you'd have to run it under axle, not good, and any bigger wheel/tire combo on the rear will run the exhaust and tire together.

Get a 4.2 throttle body, get it machined out, fabricate an induction tube to go with a custom maf once the diameter of the tb & tube is fixed. Then it's just fitting the twinny.

You must be talking about an overall unsprung saving? almost 10kg off each corner over standard is quite a saving, what diameter discs are they and how many hats attach it to the bell? if 12 I'd be interested in a disc set, if 32mm thick by 355mm diameter fronts, I think my rears are 350mm....

 

Ok on the 3in exhaust.. will be less money anyways.. thanks!

their two piece rotor weights in at 12.5 lbs, which compared to our OEM rotors that weight 21.5 pounds... sorry, 25lbs was off, but that's still 18lbs off of unsprung weight. Worth it?

 

9lb off? any weight saving is a plus.

 

Mine is 2.5" OD from manifolds back with X-pipe. A properly designed X-pipe flows more with the same diameter than without one. If I ever do any exhaust changes, I'll see if there are gains to be had with a 3".
But I don't recall ever confirming I have a twin screw...

 

This is coming from my domestic modding experience, but dual 3" exhaust is plenty for well over 700 whp. A friend of mine was making 780 rwhp in his 01 Mustang Cobra with dual 3". Any more will be impossible to fit and very expensive. You could run oval pipe if you really felt you needed more flow. An acquaintance that I talked to fairly frequentlyat the track tried 4.5" oval pipe under his Supra, but it is extremely hard to work with and very expensive. And he only went that big when he was making well into 4 digit power figures. He was making around 850 whp on a single 3.5" for a long time. So you won't need any more than a dual 3" if you're only going to be making in the 600 hp range. What I might recommend is a 3" system to the mid-point of the car, where you branch it out into some 3" cutouts and run (easy to fit) 2.25" pipe over the axles. When you really want the power you can just open up the cutouts but you don't have to take the hassle of running 3" over the axles and you'll have a tolerably quiet exhaust when cruising. Just my .02

 

Don't be coy - No eaton powered R runs your times, or has an adjusted 500bhp...I'm guessing but.....it's twinny powered. The dead giveaway was your question about throttle cable lengths