Dyno'd 4" catback w/cutout
 

Okay, heres the deal. I need to know if anyone has ever put a 4" cutout on a Mufflex System with the 30 Series Race Flowmaster and seen an improvement?

Now for the un-informed before they say "Flowmasters suck and don't flow worth crap", keep in mind that this is a 4" in/4" single out Race muffler that the guys in NMCA run. Not the standard 40 or 50 series junk for 3" catbacks.


I've had a couple people (un-named) that work for a very Prominent vendor on this board tell me that I need to put a cutout on the car to make real power. So I'm going to give you some information on the car and listen to what you have to say and HOPEFULLY someone has done the dyno to get hard factual results.

99 Formula
Comp Cam 232/238 595/605 XER
PATRIOT LS6
Edelbrock stepped LT's 1 3/4 to 1 7/8 HVMC
4" Mufflex catback
FAST 90mm combo
stock shortblock

The car has been dyno'd twic with this combo
1. 465RWHP 412RWTQ SAE
2. 445RWHP 40? RWTQ SAE

Why do you need a cut out? Why such a "big" setup? You aren't pushing monster horsepower. Not trying to rag you too hard, but I had a 4" setup for a while. I found that there is less scavenging with it and therefore I lost power and velocity of exhuast gases. I ran a 3 1/2" cut out and there was a noticeable difference with it vs. closed. 3" would suffice for stock cubes with a race style muffler. If they say you need a cut out then you are going to big for exhaust. I understand that you are spraying, but it can't be more than a 200 shot on stock rotating assembly. You really need that monster exhuast? Just think about it.

Its kind of a story but here it goes. I put this same exhaust on my LT1 car in my sig and the car picked up .2 N/A and .35 on the gas. You could actually feel the difference in the car from the 3" catback the car had. The amazing sound was just a bonus.

So I bought this car and removed the Magnaflow 3" in favor of another 4" mufflex system. Once again, the car felt tons better throttle response and the low end grunt was much improved.

No offense taken on the "not alot of power" comment. Its not alot in the LS1 world but its nothing to hang your head about when you have over 520+fwhp from a 90k mile stock shortblock and havent even cracked open the 200 shot yet :devil:

From talking with Mike Norris at Next Level Performance(where I dyno'd first), running the header that I'm running with the LS1 port and an LS6 exhaust port cylinder head, it helps quite a bit with scavenging not to mention the LT's have HVMC's and that helps some as well.

Now I guess, I really need to answer this question myself. I guess I'll be ordering the cutout for my piece of mind :)

Thanks,
Jeff

465rwhp isn't big horsepower :confused: yea, it's not the fastest car in the world but it's over 500hp flywheel and that doesn't sound like anything to laugh about. i know a 3" magnaflow would be VERY restirctive on that setup since oxidizr himself said the LS1 magnaflow catback is restrictive over 400rwhp and they are working on a race magnaflow system to combat this.

in short, yes his magnaflow was costing him big horsepower and he was in need of a bigger setup.

Are you kidding? It might be for a heads and cam stock shortblock. I should have put a number down. starting at 550rwhp. IE: Turbo. It is probably making some power at 6800 with the 4".

There r plenty of 500+ hp guys that run magnaflow with great results....search the threads :)

N2OSTROKER posted a dyno comparison through a 4" mufflex exhaust with a 4" cutout on a 402. He averaged approx. 18 hp and tq across most of the graph with the cutout open. The most important comparison is his track results. Through the exhaust he runs consistant 10.5's. Through the cutout he runs consistant 10.35 to 10.45.

i'm not doubting it can handle 500+hp, but there will be some loss through the muffler. i'm sure the cutout on a 500+hp car would be worth at least 10-15 horsepower, so that in itself makes it worth the measly 45 bucks for a stainless one.

I've been searching for 4" cutouts but the only one I could find was a QTP at Thunder Racing for like $75 :eek2: and throw an electric cutout on top of it and thats like $250 :bang:

So I'll be looking to purchase a basic cutout and then dyno the car. If it makes a noticeable improvement, I'll add the electric portion after that because I'm not crawling under the car everytime I need to open it.


Jeff

Good luck with the cut out. I personally don't see much improvement, if any, with the cutout. If you do get improvement, I might have to get one myself. :devil:

FWIW my buddy is using the 4" Mufflex with the Flowmaster on his 91 Camaro 383 TT project.