Our NA combo ran 3" Dynomax race bullet header mufflers. We decided to leave them on with the ProCharged combo. I just installed 3.5" Dynomax race bullet header mufflers. Both set-ups add about 16" of collector length; the only differences are the dia. & the 3" mufflers had no packing.

While I could do some testing at the track with the 2 different dia. mufflers. With only (2) time hits during points races, I'm not going through the hassle of swapping them. I mainly changed the mufflers to quite the exhaust a little more & they do that.

Does anyone think there will be a performance increase? I'm not really concerned if it makes more power or not, we do that with boost or fuel/timing map changes.

2BKING

I would bet the only difference between the two is the larger ID one might be quieter with the packing.

My car has 3.5” ID Dynatech mufflers that are 5” OD packing and have a flat perforated baffle inside the full 6” length of the muffler. I think these type mufflers help with noise reduction and no performance loss. I like mine and one of the reasons I would not have fender exit exhaust.

quote:

Originally posted by markemark:
I would bet the only difference between the two is the larger ID one might be quieter with the packing.

My car has 3.5” ID Dynatech mufflers that are 5” OD packing and have a flat perforated baffle inside the full 6” length of the muffler. I think these type mufflers help with noise reduction and no performance loss. I like mine and one of the reasons I would not have fender exit exhaust.

The larger dia. mufflers are definitely quieter & they have the same basic features of your Dynatech's.

As for a performance increase, we'll see. I think any power adder motor is more sensitive to back pressure than a NA motor. I hope to test/race in July, if the car gets back from body/paint.

2BKING

One other thing I like with mufflers is that I have 16” of pipe behind the O2 sensor located in the collector. This aids in using closed loop and learn to get the idle map programed to the desired AFR with an ECU.

I have 23" of collector/muffler after the O2 sensor. Holley wanted a minimum of 18" if I remember correctly.

2BKING

Here's the only article that I found that somewhat resembles my header muffler change.

https://www.motortrend.com/how...2-exhaust-test-tech/

2BKING

Turbos are more sensitive to backpressure than a supercharged combo. The article references a turbo car, I'd expect that. The pressure differential across the hot side turbine wheel is a direct indicator of how hard/fast you can turn the cold side wheel.

For a supercharged applciation, i'd expect way less impact, assuming the 3" was in the ball park for not being a restriction. If it was a restriction, then you'll see some improvement but less than a turbo application.

I agree but a header muffler is the worst place to have a restriction.

Regardless the new bullet mufflers are significantly quieter & that's the major reason for the change.

2BKING

I was going over my data logs from this past weekend's racing. I noticed a distinct difference in my peak boost pressure. I usually peak around 14 lbs. this past weekend I was getting around 10 lbs.

While we were setting heat records & it was the worst air, we have run in 5,000'+. I've never seen the boost get affected as much as this.

Then I remembered I had changed to the bigger dia. mufflers. I know flow in & out of the motor with heads, cam & exhaust changes boost pressure. I'm trying to wrap my head around did the muffler change affect the boost that much?

As stated in the previous post, "a header muffler is the worst place to have a restriction".

2BKING

Well, the first thought is that it was restricted, and now the engine has caught up to the pump / intake capacity, but I'd verify that theory in some better atmosphere first.
Lack of atmosphere has to affect the boost production as well.

I am with Goob, you lowered the back pressure with the larger mufflers. Now your charge mixture has less exhaust gases in it, So you are making more power. I would look at your timing, you may have to back it down a couple of degrees.

Joe

I have some options:

Install the old mufflers, probably not going to do that.

Smaller blower pulley, maybe.

Leave it as is & see if boost follows the air. I've never noticed a big swing in boost with DA changes.

I've got the bracket finals coming up next week. Best bet is to leave it alone!

2BKING

quote:

Originally posted by sr4440:
I am with Goob, you lowered the back pressure with the larger mufflers. Now your charge mixture has less exhaust gases in it, So you are making more power. I would look at your timing, you may have to back it down a couple of degrees.

Joe

I'm not disagreeing with you guys! Something made a big change in boost & the only changes was a drastic DA change & the larger dia. header muffler. I'm leaning toward the muffler for most of the change. The DA plays a small factor in boost from my data.

As for the timing, didn't have enough before according to the ground strap. Maybe I have some now.

2BKING

There used to be one big performance muffler company that said they use backpressure to increase performance. There is NO GOOD BACKPRESSURE in a performance motor. Also ANY restriction on intake side will hurt performance.

I do like to run mufflers because I like to be able to hear my motor and opponents better but I realize there is a performance penalty for it.

Same with a filter on the intake, it will surely help the life of your motor by stopping much of the dirt and dust that goes into your motor but it to has a performance penalty. Even on my compressors which do not take in nearly as much air as a car does an intake filter makes a noticeable and measurable difference on output of compressor.

Zero difference with or without my filter.

This is just a wag on the muffler change. The car ran the same ET & mph in higher density altitudes at the bracket finals. Our 9.00 tune for 2500' to 3000' DA was running 9.0's in 4000' to 4500' DA.

2BKING

quote:

Originally posted by B KING:
This is just a wag on the muffler change. The car ran the same ET & mph in higher density altitudes at the bracket finals. Our 9.00 tune for 2500' to 3000' DA was running 9.0's in 4000' to 4500' DA.

Ain’t EFI (TB) SWEET!

quote:

Originally posted by markemark:

quote:

Originally posted by B KING:
This is just a wag on the muffler change. The car ran the same ET & mph in higher density altitudes at the bracket finals. Our 9.00 tune for 2500' to 3000' DA was running 9.0's in 4000' to 4500' DA.

Ain’t EFI (TB) SWEET!

I don't give the EFI all the credit. The ProCharger does help also! I still have work to do with the tune.

The car & driver are about equal for contributing to round wins. I'm trying to get it back to the car taking of the driver.

2BKING