CMIs on 496 HO-Myth or Real?

[CRC]

Page 8 of our catalog at www.custommarine.com shows four of the many results responces from customers. Teaque also ran 4 or 5 quantified before and after header installation tests with great results, you can call him at 661/295-7000. I myself have no need to make up data, after 100's of 496 header installations and 25 years of this job, it would not be worth it.

Would you include myself and others who saw NO gain on page 8 of your catalog?

[Pismo10]

What is a guy from TCM going to say..Come on..

[Raylar]

Jrz:

Lets not get your panties in wad here!
I am not saying anyones dyno pulls were fudged, tweaked or otherwise. Two different dynos will usually have some differential as well as the other factors affecting a dyno pull on an engine like, coolant temperatures, time sweep of actual dyno pull, fuel type used, etc.,etc.
What is important to remember here also is that actual power made on an engine upgrade does not always translate directly to speed increases in various boats. There are too many other factors that will affect speed in any given boat, like weights , hull design, drive mounting height, type of water and air temperatures, altitude, hooks in hull, driver skill, etc.,etc., etc.
What these paticular boaters are referencing here is that on their own boat, same boat, same drive, same boating location, same driver, roughly the same boating conditions they saw absolutly little or no measurable increase in the speed and performance of their boats. We would also like to believe that if their original prop pitch was not changed that their top rpm should increase lets say 200-300 rpm and they should be able to use a larger pitch prop of same type and style and see a corresponding speed increase.
If one was to make a simple assumption from this input one would assume that if the CMI Sporttubes made 50-60HP as your dyno charts and dealers advertized, that a 50-60 HP increase in engine power which would be about 13-15% increase in engine power that this should translate to some performance increase.
I guess this is a case of 2+2 not equaling 4 and thats what has got them asking questions and feeling shorted since as bang for the buck goes, their
$4K to $5K investment appears to have yielded no real increase which makes the investment pretty hard to justify for them.
I know as well as others who have tested various true header systems versus stock and aftermarket manifold systems that true headers such as the CMI sportubes, Dana Flo-torque, Kieth Eikert cast headers, Hardin Marine headers and Lightning headers make measurable power increases. Our testing as well as Bob at Full Throttle and some others has shown time and time again that generally these increases on stock 496MAGs and 496MAG-HO's ranged between 30-45HP. Even at these modest level increases most hulls should respond to this power increase with a 1-2 mph increase @ about 15-20HP needed per mile per hour. In many cases this did happen and was documented by many boaters with before and after in the water testing.
The problem that exists now is that with the claims of 50-60HP for CMI Sporttubes over stock exhaust that it seems even less likely that a dealer should claim that a particular boat increased its speed by 7 mph with no other changes. Either that boat in question had some other issues, like a bad prop selection to begin with which was corrected after installing and testing the new header system, other upgrades were made at the same time, a new an more expierenced driver did the after testing who new better how to trim and run the boat, conditions before and after the change were significantly different or something along these lines.
In any event lets always be careful to make the testing somewhat scientific to properly document before and afters and if your 496 sportube headers make 10-20HP more than some of these others lets see it really demonstrated in a single boat, on the water, same test, same conditions and equipment and it should be demonstratable that CMI's can generate 7mph more speed than stock exhaust, especially when compared to other headers.
I know where my money and bet will be!

As for the HP3 496 -525HP program your making a non-conforming comparison since the GM Vortec HP3 engines that were built and run by Innovation were never tested with any form of stock exhaust, since GM does not make marine exhaust and the engines were not available with any other exhaust than the CMI headers your company originally provided for the GM program.
And when it comes to 496's I don't think there are too many people in our industry with more knowledge or expierence with hundreds of 496's that we have here at Raylar.
As I keep telling and proving to everyone in the industry, the newer Mercury Marine exhaust manifolds and risers as designed and built for the 496 engines are a really big improvemnt over older designs and types used on the 454-502 mpi-efi engines and are still an equal to the Gil type systems that Mercury installed on the HP500 engines.
I know your dealers want to sell your headers and systems and make a profit for themselves and you just as anybody who is in this business does.
I just think its about time this industry in general starts making more factual based claims and stop using adjectives like as much as, up to, etc. etc.
Every good manufacturer,distributor and vendor should be prepared to back up his claims and advertising with real world results and proven results.
If the results are less than advertised, the advertising should be modified to fit the actual results.
When performance boaters buy expensive equipment like headers, engines, drives, upgrade kits and such they should be delivered a product that meets its claims, no more no less!
In other words you get what you paid for!

This is where the integrity and future of our sport and business should be demonstrated and protected.

Best Regards,
Ray @ Raylar

[CRC]

I didn't want to quote all that but great post Ray. That about says it all and from a guy who probably knows more about the 496 than anyone else! The Donzi 22 Classic responds well to power increases BTW.

[launchpad]

how fast is that classic now, just out of curiousity?

[Donskihp]

I installed the CNI 496 sport Tubes on my 496HO in 2007. Prior to the installation I was running 68mph in my 2005 Donzi 26zx. I was not hitting the relimiter at that time. After the installation I was hitting the relimiter so I steped up from a Brovo 1- 24p to a 26p. I gained 1.4 mph.( Speed went up to 69.4mph) I would have gained more speed if I hadn't also gained slippage. I went from 10% slip to 16%. The 26zx has a very high X dimension,wich I later discovered and found the Brovo 1 was adding to my transome lift ,increasing my slippage. Any way I realized a speed gain with the CMI's. But if you really want to gain speed the Whipple supercharger will do a fine job. I read an articled on horse power vrs/speed and how much hp it takes to gain 1 mph,the the test said it took 20hp to gain 1 mph. That seems to be about right for my experance.

[gcarter]

So while this is still going on, what would be the best way to spend $5K on a 496, or a 502 for that matter?
I know CRC, and I tried to discourage him from going the route he went. I suspected the results he got were what would happen.

So, back to my question.....how could $5K be better spent for better results?

[Donskihp]

For 5k you could proCharge a 496 and Whipple is about 8k. However any one supper Charging a 496 needs to know if their 496 has forged internals. It won't hold up if not forged.

[blackhawk]

The latest claim being in the Feb '10 issue stating that the owner of a 26 Baja Outlaw can expect 4-7 mph with just the headers and a prop change.

Actually I believe that. CMIs were probably good for .5mph and the prop was good for 3.5-6.5 mph.

[ElvisAaron]

good tips, thx a lot
__________________________________________________
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[Gordo]

Since this has become an Exhaust manifold/header discussion, Is there ANY difference between the CMI and the Lightning Headers? and
What (if any) difference between the tube primary headers and the cast headers, such as RM, Stainless Marine, Dana, etc..
I can start another thread if y'all want...

[Wardey]

Since this has become an Exhaust manifold/header discussion, Is there ANY difference between the CMI and the Lightning Headers? and
What (if any) difference between the tube primary headers and the cast headers, such as RM, Stainless Marine, Dana, etc..
I can start another thread if y'all want...

Hey Buddy, Give me a shout.

[FTMBOB]

I've dyno'd 496's back to back with stock, Dana and Lightnings. Here's a link to my web site where I posted the results. http://fullthrottlemarine.com/496%20...%20Article.htm I also tested the CMI sport tubes before & after on a 496 HO at the prop. The CMI's gained 28 HP over stock. The Dana's
gained 23 if I remember correctly and the Lightnings a couple less than the Dana's. Bang for the buck I'd go with Dana's.

Bob

Since this has become an Exhaust manifold/header discussion, Is there ANY difference between the CMI and the Lightning Headers? and
What (if any) difference between the tube primary headers and the cast headers, such as RM, Stainless Marine, Dana, etc..
I can start another thread if y'all want...

[Gordo]

On the typical twin engine boat, how much weight savings between the old stock factory cast iron exhaust, and the tube headers or the custom aluminum headers?