Cutting the y-pipe for H-pipe duals. Affected Backpressure?

Rhino77 · 09-12-2007, 01:59 PM

Hello all, I have been reading through many of the threads in the v6 tech section, and found them extremely informative. The particular concern that I have I did not find, so I would appreciate some perspective on my questions.

I was speaking with a local shop out here in San Bernardino, explaining that I am looking for magnaflow duals, with an H pipe.
The owner's concern was the issue of back pressure, and that with the cutting of the Y pipe, the back pressure would be lacking and that gas mileage would drop. v6 is an '08.

1) Is this a legitimate concern?
2)Will the gas mileage drop rather significantly.
3) Would the best route to go, be to keep the Y-pipe with a dual setup behing the Y? If so, will the rumble be as deep/loud?

Thanks guys.

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ARdoller · 09-12-2007, 02:06 PM

well a lot of guys that have older v6's (94-04) see an increase in gas mileage. your backpressure will be fine as long as you leave your cats on.

if you take the cats off, your gas mileage will go back down to about stock.

raz54 · 09-12-2007, 02:20 PM

I'm not sure on your MPG but if you lower your back pressure too much you will sure lose low end tq. If you stay with 2.25" pipe and keep all the cats you should be OK with true duals.

Rhino77 · 09-12-2007, 02:25 PM

Thanks for the quick response fellas.
I just finished talking to another performance exhuast shop out here in the San Bernardino, and it seems as though none of these guys have worked on putting a dual system in a V6.
The fella I just talked said I'd have to come down to his shop to take a look at the system on the car, to have a better idea which is of course is reasonable.

I've got Gibson Performance by me in Corona, Ca and they have develped a dual system specifically for the v6 (part #319007)...Upon further inspection it looks like that part# is dual with an off road x-pipe...Now doesn't off-road require removal of the cat? I just want to cut the Y and stick the dual on after.

This is frustrating not finding a competent exhaust place to speak with, hell, the Route 66 celebration is the in the middle of this city!
(maybe I shouldn't say "competent", but rather an installer that sounds like he knows what he's talking about).

ARdoller · 09-12-2007, 11:27 PM

just buy a catback system. any gt catback kit that will work for your car's year will do. then go to www.americanmuscle.com and buy an h-pipe adapter.

just tell them they have to cut the y pipe and bolt the h-pipe adapter up and the catback bolts up directly with no changes needed.

they put universal hangers on mine instead of using the ones that came with the h-pipe kit. you might want to talk to them about that.

945LSTANG · 09-12-2007, 11:29 PM

back pressure is of no real concern on newer EFI cars.

ARdoller · 09-12-2007, 11:36 PM

yes it is. if your exhaust system is too free flowing, you will lose a lot of low end torque. my h pipe came loose tonight, and driving home, it took quite a bit to get up to speed from a stop.

raz54 · 09-13-2007, 12:23 PM

Quote:

ORIGINAL: 945LSTANG

back pressure is of no real concern on newer EFI cars.

That is the dumbest thing I've heard! Even race engines need some amount of back pressure.

ARdoller · 09-13-2007, 03:10 PM

well most race engines are carburated, but thats besides the point[8D]

the 4cyl mustang after 1985 was efi, and that car needed all the backpressure it could get

olvanish · 09-16-2007, 03:19 AM

If you do that your gas mileage will be about 3-5 percent lower plus you'd lose some low end torque just like people who put 3 inch piping on 4 bangers do. backpressure is the cause