The SRZ

This is for my 385 blown F1 shooting for 800rwhp this go around.

Current exh is FLP 1 3/4", no cats and their scrawny y-pipe out to a 4" mufflex exh w/ 40 series flowmaster muffler.

Slowly getting my thoughts together on this. Going to be switching to Kooks 1 3/4 stepped to 1 7/8 w/ their 3.5" collectors using V band clamps off the collectors. My issue is clearance of course and customizing...use kooks y pipe or go full custom using oval piping w/ transition pipe to a flowmaster merge collector and v band to attach to my 4" mufflex exh.

Are there any cons to going oval? Based on what little I've been able to find out would be loss of hp and or back pressue and or scavenging. I'm not sure it'd be and issue or not but would just like some thoughts. I'm only spinning it to 6400rpm though it can be spun to 6700 no problem.

Thanks!

Injuneer

Why do you feel losing back pressure could be a problem? You want the exhaust, after the collectors, to be as free flowing as possible.

What size oval tubing do you want to use, what width/height/cross-sectional area? Pressure loss has to be minimized, and pressure loss is a function of cross-section area and "wetted" perimeter. A circular pipe has the lowest possible wetted perimeter for any given cross-sectional area. You need to make sure the area of the oval pipe is a bit larger that the area of a 3" or 3.5" diameter Y-pipe (whichever alternative you are looking at). The extra area will make up for the increased wetted perimeter.

The SRZ

Damn Fred you're still around?!

It's just some of the online material I've read in terms of going oval. I think they mostly referenced N/A setups however. Size I'm looking into is 2 1/2 x 4 oval.

Silas,

Injuneer

Appears you're going with the responses on ltxtech.com .

The SRZ

Actually, I'm not just what size based on several sources. I had found a couple of Chevy Muscle Car online info but now I can't find it that mentioned what you were talking about. That was the reasoning for asking in the 1st place, just needed more understanding of it all. Hoping to have something like this when it's all said and done if it is indeed worth doing.

Injuneer

The biggest problem is going to be the transitions from round to oval. Expansions and contractions in the pipe (anything that disturbs flow) results in pressure drop. The transitions from the round collectors to the oval pipe in the picture look good. Not sure about the "Y" point... compare it to the length of the Flowmaster dual 3" into 4" merge.

The SRZ

I'm wanting to use a Flowmaster 3 to 4" merge collector. But seeing how transitions can disrupt the "flow", I may have too many transitions for it to be effective. Round to oval at header collector, oval back to round to the merge collector. Do you feel that's too many?

May not be worth the headache and just build a custom 3" or 3.5" y instead tucked nicely under the car.

Injuneer

I'm probably overthinking this. I had the custom 3" Y-pipe in the picture, with 3" Borla XR1 mufflers in place of the cats, through a 4" Mufflex catback. At the 800 (flywheel) HP level, removing the Y-pipe and the catback, and substituting 3" straight pipes/turndowns from the XR1's to in front of the rear axle had not real impact on HP.

If the issue is ground clearance, the oval pipe will have to be placed "high" with the transitions eccentric (top of collector even with top of oval pipe) to keep the bottom of the oval an appreciable distance above the ground. Just use common sense with the fabrication. I've seen oval dual pipes run all the way from the collectors to small mufflers, then under the axle to tips in the normal place at the rear bumper. Didn't seem to be a problem with a 1,000+ HP forced induction LT1.

The SRZ

Thank you Fred.

RealQuick

It may be a cheaper exercise to put in a cutout or drop the exhaust like Fred said, and see if it nets you anything.

The SRZ

I've just decided to go Kooks stepped and their new style y pipe. Seems too much of a hassle to attempt at this point.