Well my testing with these 3" mufflers is done and before I begin here is a quick breakdown on my setup.
TFS 185 CNC
Freezy 74 camshaft
Edelbrock RPMII intake
Snow Performance Stage 3 water/methanol w/Boost Juice (50/50)
MSD 6AL-2 Programmable
MSD HV coil
Firecore 50 spark plug wires
1 3/4" MAC Shorty header
MAC 3" ProChamber
MAC 3" catback with MAC Flowpath mufflers
We recently switched from a 2.5" exhaust system to a 3" system and picked up 45rwhp @5700rpms: 2.5" vs 3" exhaust dyno results
Now conventional thinking would make you believe that a straight thru design muffler would be less resetrictive vs a MAC Flowpath. See pics of the Magnaflow muffler:
But that was not the case:
With no other changes we lost 45rwhp @ 5300rpms.
Please note while testing the Magnaflows we were fighting an engine miss@5300-5400rpms.....my
fault. Thinking that the straight thru design would command more fuel, I decided to regap my plugs from .035 to .020 but an engine miss developed. It wasn't until yesterday I decide to regap (using the same plugs) them back to .035 that the miss went away. I know, different than what most people say but I always run a .035 gap with Autolite 3924 with no issues.
Here is my 786rwhp (MAC Mufflers) run vs a couple of Magnaflow mufflers. Notice the huge HP difference (area underneath the curve and our new peak of 5300rpms).
Magnaflow run numbers: Runs 121 and 122 on 9/14/2011
MAC Flowpaths: Run 109 on 7/14/2011
MAC Flowpaths: Run 128 on 9/17/2011
Here is a RWTQ curve: Notice the huge differences in RWTQ
Now I spent all day at the dyno on 9/14/2011 trying my best to retune for the Magnaflow mufflers but they were down on power, its just that simple. Now on 9/16/2011, I had my old MAC Flowpths re-installed and headed back to the dyno the following day. See results below:
Important facts from my testing:
1) When I first installed the 3" exhaust system it commanded alot more fuel than the 2.5" setup because it was moving alot more air.
2) Switching to the 3" Magnaflow mufflers we were to rich and had to remove alot of fuel. Meaning it wasn't moving as much air and the decrease it RWHP and RWTQ show that.
3) Switching back to the MAC Flowpath mufflers commanded alot more fuel. Meaning it was moving alot more air vs thge Magnaflow and the increase in RWHP and RWTQ show that.
4) MAC Flowpath is NOT chambered muffler like Flowmaster. MAC Jr. said the Flowpaths are designed around flow and they outflow all the street muffler competition except for Borla XR-1. Granted Jr said not by that much.
5) Why the HP & TQ loss. MAC said those so called straight thru design mufflers like Magnaflow, Ultraflow, Race Magnum that have a huge body or cavity, causes a vortex. A vortex
vortices) is a spinning
, often turbulent
, flow of fluid
or air, inside the muffler and this causes a restricition. MAC also stated that the smaller the cavity or body the less vortex will be created hence a bullet style muffler isn't affected as much.
Magnaflow muffler test: Part#14239, size: 14" x 8" x 5"
MAC Flowpath: Part#FP743, size: 13" x 9" x 3.75"
On another side note
, I played around with testing spark plug wires (Accel 300+, Firecore 50 and FMS) I saw no noticeable difference in HP or TQ but I run the Firecore 50 because it moved the engine miss up higher in the rpm band vs the others.
Spark plugs: Autolites vs NGK, again I saw no noticeable difference in HP or TQ but on my combo my car seems to drive better with the Autolites. So I use Autolites.
On my setup the larger gap (.035) makes alittle bit more power (3-4rwhp) than a smaller one (.020). So I run the larger gap and my ignition system components have no problem igniting the mixture at all.
All runs everyday and all day is on 93 octance with water/methanol injection system from Snow Performance.
Huge Thanks to Mike Dez Racing http://dezracing.net/
for letting me come in and do testing when I want. Mike Dez and his staff are top notch and I'm glad he's available to me.