Planning my exhaust

Topic: Planning my exhaust (Read 3217 times) previous topic - next topic

Planning my exhaust

Reply #15 – June 03, 2012, 06:03:38 PM

Thanks, Darren, that's the kind of info I was looking for.

Planning my exhaust

Reply #16 – June 03, 2012, 08:09:05 PM

We've all seen the 500hp on e7 heads and stock exhaust threads, but that doesn't mean you only want a better set of heads over 500hp...

Mustang stock pulls about 225fwhp. Some gt40 heads and explorer/cobra intake, you could hit 250 or so. Throw a bigger throttle body and exhaust on, you should be in the 300fwhp range, because of how much better everything mtaches. To get over 400hp, especially if you want it at the rear wheels, your going to need all the help you can get. Getting air in and out of the engine is the easiest way. Throwing a 75mm or bigger throttle body on a 302 motor in't going to hurt anything. Nor will getting rid of gas faster.

The exhaust heats up because there is a restriction between the hot air and the piping. The hotter it gets, the more power you are wasting heating up the tail pipe, and not pushing it along. The hotter you make your exhaust, the more likely you will ping, and the less timing you can run.

Also, the less back pressure the motor has to fight, the faster it accelerates. The faster it accelerates, the more power it makes quicker. This is one thing that is almost never shown on a dyno graph, and a much better guage of increased power. I've seen cars with just over 300hp and big 3" exhaust pull big wheelies and leave the line hard. But I keep forgetting about how much low end and hp they dropped, even if they are running faster at the track, more then offsets everything.

If there is a drop in power because of exhaust, its not a lack of backpressure. Its a problem of a/f ratio or tuning. A restriction csts power. Why would removing a restriction limit your bottom end and cost you hp? It kinda goes against everything that your supposed to follow when "building" an engine/combonation.

Planning my exhaust

Reply #17 – June 03, 2012, 11:14:19 PM

I should specify that I'm eventually gunning for 410 at the crank. The idea is to match the output of the coyote 5.0L.
BTW, whats the general feel on lers around here? I was considering Dynomax UltraFlo, it's a straight through ler available in rolled or welded construction. My personal feelings on chambered lers are not suitable for public exposure, so if you're thinking about flowmaster, keep thinking. I don't know, maybe I'll throw down the extra coin and try a pair of Dynomax VT 17159's. It seems like they might be too complicated for a simple device like a ler, but if they really are drone free, it might be worth it.

Planning my exhaust

Reply #18 – June 04, 2012, 09:08:51 AM

Borla, Flowmaster, Dyomax, they are all good lers. For me it all depends on what your preferences are with sound as dyno run after dyno run has been done with different lers and most are just about equal when it comes to flow with the exception of all out race lers. My Coupe is loud with the Flowmasters, not cats, and the X-pipe and I have been considering a change but it will most likely come when I switch to a 3" exhaust.

Good luck with 410 at the crank on a 302 motor NA with hydraulic lifters. I just don't think you will be able to achieve that number unless you go to a solid roller and spin it past 7,000 RPM. If you stroke it then you can achieve that with a hydraulic roller camshaft as I have seen all kinds of 302 based stroker NA carshiznitting the 400 rwhp number. Just my experiences and I am not saying there are not 400+ fwhp 302 cars out there but if there are they are farther and fewer inbetween than the stroked cars.

Darren

Planning my exhaust

Reply #19 – June 04, 2012, 09:18:22 AM

I agree with what Haystack said 100%. Hot exhaust is one of two things, lean (bad tune) or impingement points (ID restriction or sever bend angle). Hotter motors (to a point) make more power than cold motors. Think about it, it the Spring you start you car well ahead of staging to build some heat in the motor. In the summer hoods are up and fans are blowing on the radiator to keep temps under control. Hotter exhausts (to a point) flow more volume than cold exhausts for the reasons Tom mentioned. All aftermarket exhaust companies spend alot of time engineering out the pinch points and keeping the bend radius of the turns to a minimum all of which contribute to better flow.

Darren

Planning my exhaust

Reply #20 – June 06, 2012, 04:57:01 PM

Well as to what fits on a car with a column shifter:

FRPP GT40P shorty headers, only mod was to remove the lower stud that hit the shifter linkage. I replaced it with a bolt and nut and it fit fine.
Summit 2.5" mandrel bent off road H-pipe.
Flowtech 2.5" intermediate tubes.
Flowtech 2.5"Afterburner lers.
DynoMax 2.5" Tail pipes for a Mustang LX.

I had to add about 6" of pipe on both sides plus about a 6" chrome exhaust tip to make the pipes reach the rear bumper. With this set up I only had to lengthen the tail pipes. The rest of the stuff fit like a glove for some reason :D.

Planning my exhaust

Reply #21 – June 06, 2012, 05:32:43 PM

Won't be needing P headers. My engine is from a 96 Explorer, so I have standard GT40's, and not GT40P's (which were introduced mid-cycle 1997) This was purely intentional, because I wanted to keep internal EGR. I'm picking up a pair of gently used BBK shorty unequal length headers.