Exhaust

[turbo2256b]

I had ported E7 heads with a almost fully ported lower. HO TB , HOcam, 19# injectors. LOPO upper ported and unported runs, then a non ported HO upeer then a Ported HO upper. The ported LOPO upper realy did the best in economy and performance.

[jaywish]

For some reason, the exhaust gas going into a muffler housing works differently?

[turbo2256b]

Yes most of them have tubes and deflectors in them with sound deadners packed in the case. SAome like Flowmasters have an open chaamber wit ha lot of diflectors in them. People think there the shit but they actually flow less air than same pipe dia as a turbo style muff. Some muffs inlets and outlets are bigger than the pipes inside the case.

[jaywish]

Good to know. Thanks

[1980c10]

+1 on flowmasters sucking for producing power.

[BigT]

Interesting, why does leaving a gutted cat reduce fuel economy?

It doesn’t with mine. I get better MPGs without the cats. Maybe I’m one of the lucky ones. The way I see it, an engine is a big air pump. The easier it breaths in and out the better it will work.

[turbo2256b]

It doesn’t with mine. I get better MPGs without the cats. Maybe I’m one of the lucky ones. The way I see it, an engine is a big air pump. The easier it breaths in and out the better it will work.

Gutting a cat is not removing it .Its busting the brick out of the shell and leaving the shell in place. Removing old plugged up cats will remove blockage increase economy and performance. Stock engine new cats, good ones or replace with pipe wont change the economy.

[sly]

I got better economy when I went from 1 pipe to two. And then again when I went from 2.73 to 3.55 gears.

[BigT]

Gutting a cat is not removing it .Its busting the brick out of the shell and leaving the shell in place. Removing old plugged up cats will remove blockage increase economy and performance. Stock engine new cats, good ones or replace with pipe wont change the economy.

The cats removed were fine. I could see right through the honey combs. No blockage. After they were replaced with straight pipes, I noticed an increased in performance. Not much for a lopo, but I can squeal the tires now when I couldn’t before the cats were removed. My gas mileage increased around 2-3 MPG. Maybe I’m getting these increases because I also removed the EGR.

In my opinion it will run better without the cats. Either way, I’m happier without the cats on my car!

[turbo2256b]

EGR actually helps with fuel economy if its functioning properly. I never removed mine with some upgrages got 32.9MPG. Disconnecting it was a 3 to 5 MPG loss. Would like to have kept it when I went with my edelbrock 5.0 EFI intake.
Did you also go from single to duals at the same time? Duals should increase economy / power with or without cats. Factory duals were good for about 10HP. Just because one can see through the bricks dosent mean it isnt blocked some in areas you cant see. Also did you keep factory mufflers, stock pipe sizes.

Now if you just removed the cats and kept the single exhaust things might not have changed much at all if the cats were good.
Working as a design engineer often had to do systems testing of many things. One thing has to be changed at a time to figure what does what, what works best with what. Often engineers didnt do this sort of testing properly and got bogus results that didnt corilate because of it.
Often get a chuckle out of it reading hot rod mags as there tests are often set up to prove the best product is the one that pays the most in advertizing to them.
Not trying to bash your results just trying to explain results of not compairing apples to apples.

[BigT]

I did go from a single to dual exhaust with an H pipe. It's not factory. Had a local muffler shop make it with 2 1/4 pipe from the manifolds to the tail pipe. The pipes are not mandrel bend. The mufflers are just stock mufflers. So I imagine I get some back pressure from the bends and mufflers. I also remove the air pump. That probably help remove some drag on the engine.

If all goes well this year, I hope to install some shorty headers and more free flowing mufflers. Maybe get even better performance and MPGs. Then next will be the HO upgrade.