Horsepower limits with 2.125" hemi TTI headers & 3" exhaust

What's the limits of this set up I have on my car? Just curious. It has 17793 dynomax mufflers also. My car has been 10.97 @ 122 with this and the car is going to get a rollbar put in it soon. Just looking ahead as I may want to chase this thing closer to the 9s but would like to keep this exhaust because it's a true driver. Thanks for any insights.

There isn't an actual limit. You're already at the point where the ID is a slight restriction. It will cost more pumping loss, but also stop reverting at a lower RPM (slight bonus).
How big (volume) are the mufflers? Even in 3" the case should be wide and long.

The mufflers are 5.5x11x16 shell and 23" total length and 3" inlet/outlet.

When I was building my 540, I asked Indy whether I should go with 2 1/8" or 2 1/4" being primarily a street car.

They told me to always go with as big a tube as possible and as free flowing exhaust as possible because the Hemis wanted no resistance to exhaust flow.

Maybe I'm biting off more than I can chew with what I have already and keep it a nice street car. I really like that exhaust. Not sure a big header would fit real well under my car. Then to cut it back with the pipes I have would probably be a waste

See my post on the Hemi dyno motor tests I did last month
That was not in the car but the 3.0 inch head pipes with a set of 3.0 in and out by 14 inch long straight through Ultraflows did make decent power on the DTS engine dyno
I have tested my old pump gas Duster with a full three inch system on it with 14x7x3.0 in and out Magnaflow muffs mounted at the rear bumper versus removing the complete exhaust system at the track, .02 ET and .2 MPH difference in the 1/8 mile 7.01 ET at 95.2 MPH with the exhaust sytem hooked up and 6.98 ET at 95.4 MPH with no exhaust system on the car, Hooker A body fender well headers with 2.0 primary pipes and 3.5 inch collectors
I think the weight was possibly part of the gain and the lack of back pressure was a small part also, not enough to remove it again though

If the exhaust was a restriction and you did not rejet the carb after removing it, are the results worth anything?

Will your car be 100 or 200 pounds heavier with the roll cage? Keep the exhaust and maybe make some cutouts for those track days?

It will be a little heavier. But I'm taking the factory buckets out and using Kirkeys. Never gave cut outs a thought. Thanks

I would look at some of the faster F. A. S. T. Cars. They run low 10's high nines and are restricted to 2.5 exhaust and manifolds. I would think mufflers would be a very important part of their package. I would use what they are using in a 3" in 3" out muffler.

If the mufflers flow well their isn't going to be much difference. As for 2 1/8" headers? I went 9.0@150 yesterday with 2 1/8" and 3 1/2" collectors, no mufflers.
Doug

I'm sure my headers are good for it. I just like it quiet even when I race it. I doubt these mufflers are the best for flow.

Factory buckets LOOK so much better. I don't like the look of after market seats in a stock bodied car. Your car is very nice looking and stupid fast! If the exhaust pleases you in the fit and quiet department I would just enjoy it and don't worry about a few hundo here and there.

Thanks Dave! The kirkeys should look good in it. My original seats are not in good shape and I want the harness to go through the seats. That's why I went with Kirkeys. I can always put original seats back in it though.

I went 9.49 on some tti 2 1/8 and 3"pipes w/two chamber flowmasters.

Those headers and 3 inch pipes are fine for your current performance level, and even into the nines. But those mufflers are definitely holding you back. Switch them out for some Dynomax ultraflow SS mufflers. That is what all the F.A.S.T. cars use. They are straight through, reasonably quiet, and sound good. Then you will be good to get into the nines

Those Dynomax Super Turbo mufflers are restrictive as he11!!!! You need to either run it uncorked or, at the very least, get some good straight through style mufflers for it! It wouldn't surprise me a bit of you dropped 3 tenths by getting rid of those super turbos.

Hemis hate mufflers...they need to breathe. Definitely more sensitive to this than a wedge motor from the testing I've done. All the "old school" hemi guys told me that when I was building my hemi 12 years ago.

My dad's '69 road runner street car w/ a 480 or so hp 440-6 in it was noticeably slower when I swapped the 3" Ultra Flows for some 3" Super Turbos. He wanted it quieter, but even he was really disappointed in the noticeable loss of power after his first test drive. I knew it as soon as I pulled out on the highway leaving the exhaust shop.

My hemi runs the best either open header or w/ a pair of 4" bullets mounted right off the back of the collector (same w/ either). Everything else I've tried has slowed it down a tenth or more.

There is no difference b/t the 2.5" and 3" Dynomax Super Turbo mufflers except for the actual inlet and outlet flanges. They all neck down to the same size internally.

I bet it'd be close to two tenths quicker w/ something less restrictive though.

A pro stocker would probably run 7s w/ some Super Turbos on it. Does that mean super turbos are gonna work good for a 9 sec car since they went 7s on something real fast? They're still horribly restrictive.

Your set up is matched and you don't need to change anything.We have had similar setups and when going to a bigger tube header and collecter found a slight drop in et and mph.If you were running a 2.30 or 2.40 intake valve and a 1.98 exhaust valve and over 540" you would benefit from the larger tube.One thing we did notice is with a heavy car a 16"to18" header collecter extension can be helpful.

Change mufflers. With small block I picked up 2-3 tenths going from those to pypes racepros, but any straight through muffler is going to be better.

I also run the 2-1/8" X 3" B/E Body Super Comps on my 528" Hemi in my 70' Challenger. I figured it was the choking point on my engine but it still made great power for a street engine. On spray they may be my limiting factor but I do plan on going to some custom bigger dia step headers eventually. I added themocouples & O2 bungs to mine for tuning while on dyno & in the car.

normally I run the 3.5 pipes w/bullets., I put these on for something else(can't remember what tho.)but decided to make a pass and was surprise at the et can't remember the mph.

3-1/2" Bullets on mine also.

I picked up 0.4 in the 1/4 in a well sorted mid 11 sec car by going from TTI 3" H-pipe system with 2 chambers to 3.5" x-pipe with straight through mufflers dumping before the axle...EFI took care of the jetting for me, lol.

While it might be quicker with a larger exhaust, is it worth it if it is a true street car?

Yes.

We run 2.125 TTI headers 1230 hp 5.0 on 26's at 142 mph NA 173 @ 8.0 1/4. 565 inches, 9300 rpm going thru the traps in the quarter.

Wow! That's bookin'! I think this answers the header question...

True dat.......wondering if it's can benefit from a bigger header?

I agree

My thoughts exactly. It is crazy fast, but has it ever been tested w/ a bigger header? I don't think I've ever seen an engine making that kind of power w/ that small a header on it.

IMO the OP's car is just fine w/ the 2 1/8" header and likely would see no improvement w/ a 2 1/4". The mufflers he's running are the restriction.

What's the collector size?

Obviously!