Gutted Header & Front Pipe - Dyno Inside
 

There's a whole separate discussion regarding gutting the factory front pipe and header... but I never came across an actual dyno showing the gains on an NA setup. So for those interested, here's some reference in case you guys want to do the same.

Baseline is from another local car, which has been used as a baseline for a bunch of the locals. I think its pretty close to what these cars make stock at our altitude.

Based on my logs, the car runs a little rich and the MAF sensor still needs to be re-scaled due to the GS intake. MAF scaling is untouched from the Stg 2 OFT 93 EL map. LTFTs are around 8%, and under WOT/High RPM I think AFRs are low 11s. Was at Castrol Raceway this weekend and the car was backfiring non-stop during each session.

Modifications:
- OFT OTS Stage 2 93 EL tune
- Gutted factory header
- Gutted factory front pipe
- Custom muffler delete
- Grimmspeed Intake
- NST lightweight pulleys (Crank, water pump, alternator)

Was the header and front pipe gutted as in cut the cat out and reweld a new pipe in its place? Or was it gutted as in removed all of the insides of the cat? Pretty nice gains in the dip area.

Gutted the insides of both cats. No cutting, or welding in any new pieces.

Any pics of gutting the cat? What did you use to remove all the material??

Thanks for the post! How and what did you use to gut the cat out?

I thought about taking pictures, but the sun was going down and I wanted to get as much as I could done while the sun was still out. Didn't get a chance to take any pictures.

I used a long flathead screwdriver, and a hammer. Keep hammering the screw driver into the material in as many places as you can, and the both cats will eventually start to fall out in in pieces.

Once a couple chunks fall out, the cat will pretty much collapse on itself. There's insulation around the outer diameter of the cat that comes out with the material as well.

PS. Use gloves, and wear a breathing apparatus!

So just to clarify. You are comparing a stock car with stock tune to a gutted header/fp with OFT stg2 93 tune?

+intake & muffler delete. Though slight, but some gains may come from those too.
Still from looks of it some good aftermarket header even with stock intake / catback should do better. Just like sticky bolton mods guide shows, that looks to be most effective NA tuning. Well, at least OP eliminated torque dip.

It would probably be much better to cut out the cats and weld in suitable pieces of pipe, should flow better

and I'm sure the recycling depot would be happier to take an intact cat


put up a sound clip!

I dunno, maybe, these results look about as good as most of those $1000 cat less headers out there. Maybe the ACE header is better, but not that much in it. Keep in mind this thing is running on a very generic OFT tune from Shiv. Granted the baseline is from a different car, but same dyno at least.

And yes, sound clip please!


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It has been my assertation that the stock header with the cat removed would be as good as any sub $700 header.

Here is the one I made by welding in a collector where the cat was. More pics in my build thread if anyone is interested.
https://i.imgur.com/5FSkHSx.jpg

That said I can't imagine a gutted cat is good for exhaust velocity.

Thanks for putting this on a dyno.

so no need to spend $$ on aftermarket headers, just gut for similar results... not bad...

Yup looks kinda that way, although there are aftermarket catted headers out there that produce great results as well if you want to retain your primary cat.

I think the other reason to go aftermarket would be if you went with a supercharger or turbo system that doesn't replace your manifold - as you dramatically increase your hp via FI, you'd probably see a difference between a stock header with no cat and any aftermarket option.

But if you don't care about emissions, and want a cheap power upgrade (with a tune of course), this looks like a really viable option.