Are headers worth it over just going catless + catback

[80FoxCoupe]

Checkout Reddit or Facebook for the fun reasons. Just gotta laugh and move on.

Not part of either. This is the most e-socializing that I do. I live a simple life.

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[K4fxd]

Todays gas stinks, back in the 70's it smelled wonderful. Almost like todays race gas.

I can't believe with no cats you don't get fumes in the cabin, I have cats and if I go WOT I smell the cats in the car. First time I thought they were burning out, but found out it is normal.

 

[GregO]

Todays gas stinks, back in the 70's it smelled wonderful. Almost like todays race gas.

Remember when Shell introduced “Reformulated Gas” that’s about when the “OMG that smells horrible”happened.

 

[wingnutt]

Nah, 70s gas was mostly leaded…few ran unleaded back then

 

[GregO]

Nah, 70s gas was mostly leaded…few ran unleaded back then

Early 70’s yes, by 1975 unleaded was at nearly every fuel station in the USA. All gasoline on road vehicles from 1975+ where manufactured with a catalytic converter thus requiring unleaded fuel.

 

[High Velocity]

Definitely surprised the heck out of me. I made a dyno pull without cats (straight pipes), then swapped GT500 cats in and made another pull within the hour. It gained something like 15 hp IIRC. I'm guessing it was related to blow-through, either by losing charge or the effects of the lost charge on the O2 sensor reading. Either way, it's relevant data. I didn't try different cam timing to reduce overlap, but neither do the commercial tuners on catless setups.

So correct me if I'm wrong, but in order to run gt500 cats wouldn't you need a set of cat less long tube headers to start with? I'm planning on doing an ess kit in the future and I have personally never seen any aftermarket cats hold up like oem. Which is why im assuming you did the gt500 cats?

 

[High Velocity]

This is one of the better video's regarding bolt ons and what gains you might expect too see. Key here is doing the testing in as close to same environmental conditions as possible to get a better comparison. when I did my LTH w/cats, H pipe and tune on my 2020 Bullitt, I got almost 40 hp gains over the stock numbers. Bullitt has GT350 intake and TB and a 6spd manual, so some difference over a stock GT with the 10spd auto. Mine is tuned for 93, not E85, so i would have hit 500 probably with a E85 set up. Mine came out 485Hp/435tq. He also address' dynamic advance which can be a variable.

Every Mustang 5.0L Bolt-On Part Dyno Tested Back-to-Back! Intake, Headers, Ported IM, etc.

How noticeable was that 40 horsepower gain? Like in the real world just out and about driving around?

 

[engineermike]

So correct me if I'm wrong, but in order to run gt500 cats wouldn't you need a set of cat less long tube headers to start with? I'm planning on doing an ess kit in the future and I have personally never seen any aftermarket cats hold up like oem. Which is why im assuming you did the gt500 cats?

I think they’re too big to fit with LT headers. I did a write up on this a while back but on the PS you can bolt the stock gt500 cat to the stock header collector with a spacer and it fits surprisingly well. On the DS, I added a flange to the stock header that the stock gt500 cat bolts to.

The gt500 header bolt pattern isn’t the same as coyote. I’ve seen adapter kits/plates to make it work but I don’t have experience with them. What’s interesting is S650 switched to the 5.2 header bolt pattern on the DS only, so a 5.2 header and cat might just swap right in but I haven’t heard of anyone doing it.

And I agree about oem cats. They use a ceramic substrate which can handle high temps than the aftermarket metal substrate. I believe stock cats fail due to thermal shock, either when you initially go wot with boost or when you let off, DFCO activates and you blast 1650 deg cats with cold ambient air.

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