3" exhaust and why?

[Seer]

I'm kind of in the same boat. This winter I'm plopping a 3.4L Whipple on the car and looking for some pretty big numbers. Right now I have 1 5/8 Kooks LT's (well short LT's to be exact), 2.5" X and 2.5" tails and Magnaflow Magnapacks.

I would like to go 3" and have plenty of clearance (A Watts link helps a lot with that). But I don't want to go any bigger with the primary tubes and I certainly don't want longer headers. I like being able to remove things like the transmission without touching the headers. Wrapping another set of headers is not high on my list either. And with my motor lowered in conjunction with the stock K-member (haven't seen a tubular one I would want to go around corners fast with) clearance is already tight.

The plan at the top of the list is to cut the existing ball collector off of the 1 5/8 headers, replace it with a 3" collector of some sort and run off the shelf 3" exhaust.

I was thinking of making an entire oval tube "NASCAR" style system for ground clearance/aerodynamics/oval tubing is cool. But there is a good chance at some point I will spin the car off the road course. If I tear the exhaust up I would like to simply order a replacement, not make custom stuff again.

I'm just not sure what to do. I would be pretty bummed out to go to all the trouble to switch to 3" and find out it was worth 40hp for example. 40hp, probably up top in the rev range to boot, not worth the trouble when you are playing with 800+ IMO.

If I saw a decent before/after test of 2.5-3" that made some gains I would probably take the plunge. But at this point doing it because "it should make more power" is tough to swallow.

Thoughts? Thoughts on putting 3" collectors on the 1 5/8 headers?

I put on 1 7/8's with a 3" collector on my Whipple 2.9 GT500 at 18.5-19psi, picked up a good bit of hp. Mainly due to, sitting around calculating flow, that came out to give me the best gains for my manifold pressure.

 

[Greg Hazlett]

Did you have a before and after dyno of it? Not interested in the peak, more of the line.

 

[Seer]

Did you have a before and after dyno of it? Not interested in the peak, more of the line.

From what I recall, I picked up about 40'ish across the board.

 

[Department Of Boost]

I put on 1 7/8's with a 3" collector on my Whipple 2.9 GT500 at 18.5-19psi, picked up a good bit of hp. Mainly due to, sitting around calculating flow, that came out to give me the best gains for my manifold pressure.

What exhaust did you replace? Stock?

 

[Seer]

What exhaust did you replace? Stock?

I was replacing a stock GT500 exhaust manifold and a stock GT500 2.75" catted h pipe.

I already had a whipple 2.9 with a 3.25 pulley at the time. I now run a 3.0

 

[Memphis 05]

so.... with all this discussion, no one has mention a brand yet??? what would anyone recommend?

thanks in advance

 

[GrabberBlue5.0]

lol, you may have just opened the flood gates

 

[Memphis 05]

Well..... I don't want to buy some junk anywhere.

I want to know he good and bad out there.

 

[one eyed willy]

so.... with all this discussion, no one has mention a brand yet??? what would anyone recommend?

thanks in advance

magnaflow has been mentioned a few times.......

 

[tjm73]

so.... with all this discussion, no one has mention a brand yet??? what would anyone recommend?

thanks in advance

lol, you may have just opened the flood gates

Well..... I don't want to buy some junk anywhere.

I want to know he good and bad out there.

Valid questions. And part of the reason forums exist. LOL Could this be like asking which is better chocolate or vanilla?

 

[Memphis 05]

Valid questions. And part of the reason forums exist. LOL Could this be like asking which is better chocolate or vanilla?

True. Valid opinions and trial and error are the reason why I want to know the experiences of others.

I heard from one guy that the 3" piping would hit the axles.... Etc.....

 

[MikeVistaBlue06]

Pipes flowing "air" or exhaust gas are just like DC circuits. Bigger diameter = less resistance to the airflow. Just like a smaller resistor (big fat wire) lets more current flow. Perfectly true if the gas flow is nice and steady.

Now you go bolt on a big ass set pf pipes and your power drops and you might wonder why.

Search on my name to find previous posts to find out why...Hint: These things don't flow like DC circuits...they behave like AC circuits because the exhaust gas flow is not a steady flow...it is PULSED.

All I am saying is be careful, because bigger ain't always better. Look out for acoustic backpressure to knock your dick in the dirt if you get the harmonics wrong due to a bigger pipe! Think pipe organ and resonance. This in electrical terms would be known as impedance matching, and AC circuits sure behave differently impedance wise than do DC circuits!

My $0.02 and as always, hope this helps.

Mike

 

[Memphis 05]

thanks mike.... that was a nice way of putting things for sure. never really thought of comparing to a organ, but it makes sense.....I am so unsure of what to put on there now.... maybe what i will do is run the car with the new blower and see what happens. I can always open the exhaust cut outs and run them at the track. at least till i can gather some more information on this subject...