ET/MPH gains from a cutout?
 

Question for you Single 3" exhaust guys. Anyone do a back-to-back run capped and uncapped? What did you gain?

Zero on a mangaflow catback.

I picked up MPH with the open cut-out over my magnaflow.

If your exhaust is right or close for your car then it won't help much. If you open up a cut out on a 3 inch system and you pick up anything noticeable, it is time to upgrade to 3.5" tubing.

As my car sits right now it traps 120mph on motor through a single 3" Blowdisaster American Thunder cat-back :shock: That makes me wonder if I'm holding back a ton of HP or if single 3" isn't nearly as restrictive as people think.

I guess I'm going to buy me a cheapie 3" cutout and place it right after my Y-pipe... We'll see what happens.

i have an e-cutout. gained about 12 hp to the wheels with it open. track results? negligible. i use it mostly because my stock over axle/magnaflow muffler is pretty damn quiet, then i can open it and be super obnoxious haha.

I believe open you'll loose alittle bit of power up top....

lol i think u have that backwards. usually when u open up your exhaust it bumps your powerband more to the top. youll loose a lil down low. but, if youre launching at 5800 rpm, it wont really matter lol

Really, both ways of stating it are a bit wrong. You don't actually "lose" any torque, you just push the torque curve up the RPM range a little bit. Since HP is a function of torque and RPM, as the RPM used goes up it will show some small increase in power.

That being said, if you are not using enough of the power band, especially in high gear, to use the new found power at the higher RPM you are not really going to see much of a gain from it.

If you picked up more than 1 or 2 hp then your muffler/tailpipe is way too restrictive. I can't believe the Magnaflow is hurting you that much. You may want to pull that muffler off and take a look at it. Is it really a 3" inlet muffler or did you get a V6 system that might be smaller pipe? Something isn't right if you picked up 12 hp to the wheels.

His car is cammed....could have something to do with it.

I wonder if he's running overly rich and opening the cutout helps balance it out. I would still be really suspect of that muffler though. 12 rwhp is a big number.

i remember he just replaced an o2. i don't know when it was dynoed or anything.

It is, and I don't think his cam is all that big. I'm pretty sure the people who installed it are the ones who dynoed. It was on a mustang dyno I believe so it's more like 15-17hp on a regular dynojet. I'm sure Doug will chime in.

heres the thing. i only have a magnaflow muffler attached to the STOCK over axle, which is what? 2.5"? not sure if that has anything to do with it.

cam was installed, tuned, and dynoed by the same crew. mustang dyno. the cam isnt all that big 230-230 .580 lift 113 lsa. as far as being rich and balancing out with it open i am almost positive that is NOT the case. it was a back to back dyno run (368rwhp closed 379rwhp open)

i dont know how it made a decent improvement...i will be sure to get some track runs in and see if its any different.

oh and its the magnaflow universal part number 14267. its a 3" inlet 2.5" dual outlet.

Its that 2.75 piping thats doing you in, Doug...

Yeah, the stock I-pipe and over axle pipe are 2.75". The full cat-back should be one of the first mods done unless you have an SS or WS6 with the optional exhaust which is 3". I'm surprised the car has a cam and not a cat-back done to it.

i just never got around to buying a catback lol

hmm maybe thats why i put down less hp this time around 335/353. although i have a single straight pipe, its the stock over axle pipe going from the Ypipe back. last time i was at ttp, which was in 2007 i believe, i put down 342/362 untuned with a 3" magnaflow catback and a cutout open. cut out only gave me 1-2 hp more

geeez maybe i shouldve been a lil more specific then. i didnt mean he would physically lose hp or tq. bahhh i shouldve just said wat u said in the first place lol

I noticed no gains over a magnaflow exhaust

Update on this one. I installed one of those cheap clamp-on Summit 3" cutouts in the I-pipe that dumps right under the rear floorboard. The car picked up precisely 3 tenths on motor :shock:

junk:moon:

whoaaaa!!!! thats some bang for the buck!