Do I really need 4"??

[Mogman]

OK I am doing a LMM Humvee conversion, every one I see has a 3 1/2" (or maybe a 3"?) down pipe then 4" out in front of the rear wheel.
My engine has an improved intake, a Cheetah turbo, DSP-5 and had a 4" exhaust, and it looks like the engine has been built/rebuilt but does not have studded heads, other than that I have no farther history.

So I am thinking that I am replacing a 165HP engine and don't need the 500HP or so that this engine is likely able to deliver, and I am a mature driver and that a 3 1/2" exhaust with no muffler, four total bends and wrapped for increased flow and heat reduction would be OK.

Now don't get me wrong I might want to do a couple donuts in a parking lot or shock an unsuspecting driver occasionally.

The pic is not mine (I wish I was at this point!) but gives an idea of total length.

So is there anything wrong with my thinking? a 3 1/2 would be a little less clumsy.

 

[TheBac]

No. You're just "straight piping" the stock exhaust, which many people have done in the past.

 

[gmduramax]

Is 3.5” fine, yes. Would you see more power with 4” maybe. Is it worth the trouble trying to squeeze it in a swap, probably not.

 

[Dozerboy]

X3 I made 500hp on a stock straight pipe truck. I only went bigger when my delete pipe rusted out.


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[RMJ_LB7]

Only reason I went with a bigger exhaust system was due to sound. I have had stock 3.5", 4" & 5" exhaust all straight piped and never saw a difference. What I did notice a difference in was when I went with the 3" downpipe.