Exhaust Question
 

I have no doubt there are many opinions on this board about exhaust systems. My question concerns switching from "true headers" like CMI to a more dependable Stainless Marine Gen 3 manifold system. Around a 1000 horsepower..........any performance loss?????

If Supercharged (especially postive displacement), engines care less about tuning lengths and ID's than Naturally Aspirated. They, however, want as least restrictive as possible with sizes 'within reason.'

At 1000HP you will have no HP loss (or torque if supercharged) using the Gen III with 4 1/2 or 5" tailpipes.

Gen 111's make more power on blower motors from what I hear. I have a couple sets waiting for the fountain if you want to put them on for mock up and measurement. I'll be back in the shop tomorrow if your around herb.

Interesting comments. 1/2 the price and no disadvantages. Seems to good to be true. Yes, I can come by tomorrow. Actually have a pair coming to see if they fit in between the 2 engines ok. Just ordered them this afternoon. If you have a pair maybe I can call first thing in the morning and tell them not to send out. Save some time and money.

CMI's are a piss poor example of a "true header". If you look at the runner length in a Stainless Marine gen 3 and a CMI it's got to be pretty dam close.

Well I don't know about the runner length being equal, but CMI is pretty much the only game in town for headers these days aren't they?

How much better are the SM 3s vs the GILs?

TTT.

How much better are one over the other. Throw in the PF Marine headers that lightning sold too. Those castings has big runners.

Stainless yes. Aluminum I think the Thunder and lightning are a much better setup. Diamond Performance bought the molds from KE. Although they look hideous I believe they are the best performing exhaust on the market. I'm happy with the Stailess Marine Gen 3's but if I had it to do over again I would probably go with the Thunder and lightning's. Some want the bling of the CMI's but me personally I wish my hatch would never have to come open.

I was wondering where those KE manifolds went. Your right. They definitely weren't the prettiest looking pieces.

Yeah I think the proper response when the hatch gets opened is WTF happened here!

That's pretty funny. My biggest question/concern was that there would be no performance loss from the CMI's. That question seems to have been answered positively. I'm still leaning towards the Stainless Marine largely due to the many satisfied guys I know (didn't even realize they had Stainless Marine until I had problems with the CMI's leaking!). Also, price!

I think they are very comparable performance wise. My only complaint with the SM3's is it takes a little more effort to get the plugs out and valve covers off. With the right combonation of extensions ant swivels its really not that bad though. With CMI big tubes it's a breeze to do plugs and valve covers.

Yes. I have the CMI Sport Tubes right now. Plugs and valve covers are very easy to get at. I expected more of an issue with the VC, but why are the plugs tough with the Stainless Marine?

My Donzi has Balsa stringers so they are a mile high. Just about past the bottom of the manifold. It makes it a little tricky to remove plugs. You with have to bear hug the motor or use long extensions with swivels and get on the outside of the stringers.

IC. That won't be a problem on mine. Not that big of a deal anyway as the covers only come off once per season for a quick check. Thanks for the input.

This is true with the standard Stainless Marines as far as the plugs go as well.

Gil's really suck for changing plugs.

I never had a problem in my boat w/ gil's but always hated doing plugs in a gen3 manifold,the plugs near the water inlet suck.

Yeah I think if the fitting was an inch or so longer to drop it down off the manifold some it would make life much easier.

We have been working on making them more appealing!

What size are the internal tubes? I guess as long as I have your attention what are the tailpipe size options as well?

The runners are 32" long. The stock Bravo tailpipe is 6" . http://www.diamondperformanceparts.c...cat=282&page=1

Yes, I have seen that link. I meant inside diameter. I assume by your tall pipe answer these do not run "solid" tailpipes from manifold to back of boat. We run dry exhaust!

Bill do you have anyone that can make dry tails for the manifolds?

Of course that is what i meant by dry exhaust............dry tailpipes!

I know what u meant. We were posting the same question at the same time. I think I spoke to Bill about tails b4 some time ago and he had someone that could make them. Just can't remember for sure. I've actually thought about running the tail pipes out the sides of the hull just not sure if it would look gay or not.

why

Yes, I have someone to weld the pipes. Side exhaust looks good! 4" diameter of the stock tailpipe.

Diamond Perf.............answer to the inside diameter?

4"

I'm sure it's me being vague with my questions. Inside diameter of the 4 pipes within the manifold.

The exhaust runners are 1-7/8"

Ok, thank you

runners are too small for your app herb.

So why are these used on other 1000hp supercharged racing engines with great results?

I totally agree!!!!!!!!!!

because those motors really don't make a 1000hp.:D

Actually, there is someone on OSO that has big blower motors and running our exhaust. He says they work great.