Hey guys with the combo in my sig i went 12.7 and 107 and I thought i was running threw 3inch exhaust cause i never measured it, and its actually 2 1/2in and i have the crappy Tes headers for the tbi motor with the 2 1/4inch outlet on the y-pipe, also my cat is gutted but there no pipe goin through it. Now how bad is this holding me back you think??Would I notice a big gain with the hooker shortys and 3in y-pipe goin to a 3in catback and prob a cutout?? thanks guys

 

running 12's you might even constitute a 4 inch exhaust (Mufflex is the only one I know that makes them)... but I'm unsure of that.

 

i did all kinds of research on this stuff back before i did my exhaust. I'm not sure of the actual horse power numbers you're running, but when i was reading, here's what i found.

I have hooker 2055's (prolly the ones you were talking about) they dump into the 3" y pipe, and then flow out through a 2 chamber 3" flowmaster system, all mandrel bent no cat. I came to the conclusion that this system would support 400 hp before it became a restriction. My guess is 12.7 is prolly flirting with that line, you definitly need to get rid of that 2 1/4 ypipe, the mufflex idea is one good idea, or i would suggest a custom long tube dual exhaust if you're sure you're over 400 hp. Someone on here had an oval dual exhaust that looked great and didnt sacrafice ground clearence.

-chillen

 

Street car or race-only? If its a race car, then fabbing a set of 2.5" duals might be the best way to go.

 

I run hi 11's on 235/60/15 street radials thru a single 3 inch system with a mufflex y pipe. when i ran open headers I only picked up one tenth. I did pick up .2 switching from a flowmaster to a bullet muffler before i opened the headers tho

 

mufflex y-pipe?? do they make them for the hooker shorties?? Also does Dynomax make a 3in catback because I am going to have an electric cutout right after the y-pipe on the hookers so I dont need anything crazy in the ways of catback.. thanks

 

It all depends on how much HP you COULD push through that engine. You aren't going to get much faster, but would benefit from the system you mentioned. True dual 2.5" would be more work than needed for your car IMHO.





http://www.transamcountry.com/forum/...pic.php?t=8460
Read that, and re-think a cutout.

 

Well, I cut the stock exhaust on my ’97 WS6 and added a flange so I could just remove 3 bolts and basically drop the cat back. With a basically stock engine plus a hit of spray my best pass with the stock exhaust on it was an 11.59@119, with the exhaust off my best was an 11.61@117.9. My best NA pass was a 13.001@106.9 with the exhaust and a 13.11@105.3 without. BTW, the stock exhaust is a 2.75” intermediate pipe that necks down to 2.5” where it goes into the muffler.

Draw your own conclusions, and this did involve tweaking to get the best pass out of it both ways, and in both cases I found that the car ran the fastest if I pulled the ECM fuse before each pass, so it didn’t have anything to do with the ecm learning or tuning issues.

 

That kind of seems like bull that open exhaust can make the worst power. How can no restriction make a motor work harder and cause it to lose power. then the warlock open made great power, thats the same thing as no muffler but with an added 12 inches or so...

 

Well, those are the exact numbers that I got. I’ve never run faster in that car removing the exhaust, even the same night on back to back runs with the ecm reset before each run.

As far as the reason, I don’t think I have a good one. The fact is that the stock exhaust stuff has been getting MUCH better in recent years, and it is not uncommon to gain nothing/even loose when swapping to an aftermarket muffler (new/newer mustangs are notorious for this), so I could explain why there wouldn’t be much of a gain.

There is the possibility that you loose a little midrange by loosing some of the length of the exhaust, but in this case I’m not sure that that makes any sense since the car is an M6 car with 4.10 gears, so midrange should be a non issue and even if there was a small loss it should be easily compensated for by the fact that I’m also loosing about 20# or more by doing it. Also that explination doesn’t make much sense in my head if the car since the car still has cats on it.

Even the explanation that “taking the exhaust off resulted in more flow so it ran lean and lost power” doesn’t make sense. The problem is that it ran slower both on and off the spray. If that was the issue then you’d expect it to run slower NA but faster sprayed (I was running NX’s recommended jetting, which is always WAY RICH to be safe, so the engine running a little lean should have made the thing go faster without the exhaust).

The only thing that I can think of is that maybe the extra weight was helping me (6 speed car being launched on radials) marginally by allowing me to run a slightly faster 60’. I could probably dig up timeslips and check, but that’s a pretty half assed answer also.

The point being, that that size pipe, assuming everything else is OK is only a marginal loss in the power range that he’s talking about.

 

83 Crossfire TA ...

I believe that the stock chip on a stock setup is a good setup on a 4th gen. A stock chip w/ mods wont work as well in some cases w/ some mods.

 

i think the exhuast size really has much more to do with your cam selection more than anything....

you could probbaly gain some from an exhuast rehab..

 

Guys I plan on porting my heads a little bit and eventually putting a blower on or juicein the motor, now I don't want longtubes because its gonna stay stick and I don't wunt that headache and i may lower it int he future, So you think with as much power as I plan on trying to make that a cutout off the y-pipe won't help me? I am shooting for 11's if it matters lol...

 

If you want to stay with shorties, and want the best performance, i would highly reccomend 2055's with a 3" cut out before the cat (or in place of). The only other option would be the 1.75" SLP's with a cut out right after the Ypipe and before the cat. If you're going for an electronic cut out, the cat back is just for sound more than anything else (b/c you can go from closed to open headers with the flip of a switch).

-chillen

 

you can always get the hooker shorties, have a custom y-pipe fabbed up so that you end up with 4" right after they are combined. put the cut out on the curve around right there and run the mufflex 4" back

 

You do not need a 4"system to run 11's. A single 3" system with a good y pipe and straight thru muffler or a cut out will be just fine.

 

You're wrong and right at the same time. Your right, if your cam, heads, and such get along with a more restrictive exhuast, then you're fine.

if you have a semi radical setup for such as mine, a 3" exhaust does no good. case and point?

280rwhp/324rwtrq through a dual 3" y to a single 3" hooker cat back (no cat)

372rwhp/351rwtrq through a dual 3" y to a single 4" mufflex back (no cats)

If thats not proof that a 3" exhuast isn't restricitve on a 350, then i don't know what is.

In all practicality, it has everything to do with the cam. a short LSA cam will need the freest flowing exhuast possible, while one that's a little wider (like 114 for instance) won't be as bothered by it. So with that said, yes, 11's are possible with a good motor combo (vortec heads, xe274 cam come to mind) AND a well adjusted suspension...

Steve

 

+90 rwhp with just changing from 3" to 4" pipe???

Are you sure your not forgetting to mention a Power Adder???

 

Steve,
Was that an apples to apples comparison except the exhaust? Same dyno, conditions, etc.?

Thanks,

-Schultzy

 

nope, not forgetting a power adder... that'd be some pretty sad results from a power adder!

one difference was weather conditions, both dyno runs were at the same dyno jet facility, but from what i understand, thats what sae corrections are for... both are sae numbers, and yes, the only change was the exhuast and some tuning on the carb (jets, power valve, accel pump cam)

Also, the y-pipe was refabricated, so the entire exhaust from the headers back was different. The new y-pipe is run much straighter, and quite a few less bends... even tho the other one really didnt have much for bends in it...

I chalk it up to this...

#1)
3" pipe flows almost = to dual 2" (my primaries are only a 1/4" shy of that!)

4" pipe flows almost = to dual 3"

Obviously there is a LOT more to it than meets the eye - exhuast pulses instead of steadily flows, friction surface area... it goes on and on! however, as a rule of thumb.

#2)
I also have my suspicions about the muffler. When the hooker exhaust went on in the fall, the car ran great. brought it back out int he spring, the thing seemed quite a bit slower... i've chucked the exhuast, except for the muffler, as i think i am gonna find that something went bad in the muffler and caused a restriciton... this to would also cause th drop in power.

Again, i'll reiterate that my result are NOTTTTT typical! it just so happens the setup i have responded to the change...

Anyways, i feel i had a reasonable gain considering the issues that were at hand. Obviously the gains were in the exhuast, but which componant or combinaion of componants has yet to be determined

 

My cam is ground on a 108 LSA I have a completely stock suspension on 235/60/15 firehawk street radials, and timeslips dont lie I picked up 1 mph going from my single 3" sytem (hooker lt's, mufflex y pipe 3" I pipe and 3" bullet with a 3" tail pipe) to complete open exhaust.

 

i dont think you will see as big as improvement as i did, but when i switched from stock manifolds to a true dual 3" exhaust using hooker longtubes, i dropped 1.3 seconds off my ET. this on a pretty much stock car (did some ignition work and a K&N, thats it).