CMIs on 496 HO-Myth or Real?

[MOBILEMERCMAN]

I know a guy that had a 288 Sunsation and got 1 mph increase but then was selling the boat, took off the exhaust and still had the 1 mph.....go figure

A couple hundred hours will loosen the drive and may be the 1 mph he noticed.

 

[DAREDEVIL]

I think this is like everything else.......

the parts and boat and prop need to match 100% then u may see a gain in a better exhaust ?!

If nothing really is dialed in u won't see a differents in just changing headers exept for maybe sound. LOL

 

[CRC]

I think this is like everything else.......

the parts and boat and prop need to match 100% then u may see a gain in a better exhaust ?!

If nothing really is dialed in u won't see a differents in just changing headers exept for maybe sound. LOL

I really don't think that the stock 425 hp 496 needs the extra breathing capability. Mine had the aluminum exhaust and the ports were huge. I really wanted to tell myself that after spending almost 5 big ones and doing all that work that there was some improvement but that fact is, there wasn't. My advice is to save the money unless you are redoing the complete motor or have an extra 5 grand laying around to blow on bling. To keep publishing these claims of 4-7 mph on a single engine boat just to sell more headers is not cool.

 

[DAREDEVIL]

My advice is to save the money unless you are redoing the complete motor or have an extra 5 grand laying around to blow on bling. To keep publishing these claims of 4-7 mph on a single engine boat just to sell more headers is not cool.

:iagree:

 

[Wardey]

Bob Teague is CMI's biggest dealer, what the hell you think he is going to say!
As for 4-7 mph in a Baja with CMI's on a stock 496HO, NO WAY!
I've dynoed almost every header made on stock and our Raylar built 496's and I can tell you unequivocally that CMI Sport tubes make between 35-40HP more on a stock 496 than the stock Mercury 496 exhaust and the new CMI Sport tubes do about 20-25HP.
I know about that 50-60Hp dyno test originally done by CMI and I've never seen anybody in the industry re-create that result on a calibrated dyno, running the SAE standard with full accessories and water in the exhaust! You can confirm this with Bob at Full Throttle, he's also done a lot of header dyno testing and the results we have both seen in boats and on the dyno are about the same and pretty consistant. Bob, will also confirm with his propshaft dyno that water in the headers takes away about 15-20HP all by itself as we have seen in wet tests.
As Mild thunder has said if we were comparing Merc's older MPI and log manifolds the increase would be larger and when you go up to 500HP plus on the 496's you also se a slightly bigger increase in power, about 10-15HP more due to the better breathing required. Lets face it there are no realy cheap 40-100HP increase upgrades for any bbc engine especially the 496 family. We oughta know, we've only done hundreds of them!

Best Regards,
Ray @ Raylar

Hmmmmm....Guess those were bogus dyno sheets I was looking at ???? They DO create almost 60 HP on the sheets I saw. If I remember it was 57. On a second note, put the riser off your stock 496 risers and look at the anti-reversion ring inside. With this ring your exhaust is restricked to about 2 " in diameter.......pull the rings out for the price of a gasket set and you will see good gains but forget about your warranty after.

 

[Pismo10]

Hmmmmm....Guess those were bogus dyno sheets I was looking at ???? They DO create almost 60 HP on the sheets I saw. If I remember it was 57. On a second note, put the riser off your stock 496 risers and look at the anti-reversion ring inside. With this ring your exhaust is restricked to about 2 " in diameter.......pull the rings out for the price of a gasket set and you will see good gains but forget about your warranty after.

Not real world wet prop hp results like Ray said before. I think CRC had switchable exhaust as well which would also hurt any gains. I dont know to. Did you keep the switch exhaust after the CMI were installed?

35-40hp in a Donzi 22 classic should have given you a noticeable top end increase.

CRC, I also think your move the the 525 was probably more like 130+hp increase at the prop. Those 525s are nice.

 

[jrz]

Since all of the dyno results are faked, call Teaque for real world "non dyno" boat results.

 

[Raylar]

Who Says!

I am not saying any dyno results were faked here! As many of you know, there are different ways to set up a dyno calibration on any given run and also depends on how the engine is equipped on the dyno, when was the last time the dyno was calibrated, etc.,etc. We tried very hard to use SAE standards on our dyno tests, a properly calibrated and tested dyno and running the headers wet for real world results. How others ran their dyno tests on what in testing the CMI's with those dyno runs, I don't really know or care. What really counts is how the various boats and engines respond in the boats and under real world results in a lot of real world boats the results were for the most part as follows: 1. no change in performance. 2. 1-3 mph increase in performance. 3. A nice cool idle sound and lots of bling.
These are the results that really count, everything else is just talk and dyno numbers! You can take that to the bank baby!

Best Regards,
Ray @ Raylar

 

[Ratickle]

I would think the 35 - 40 hp you got with the CMI's only would be a pretty decent gain. I certainly would not be pizzed seeing a number like that.

 

[HaxbySpeed]

For the $ on a 496HO I don't think it's worth it. IMO. When I did a set of sport tubes for a customer a few years back they were around 5k with the quick and quiet tails. That was just the initial cost.. Doing the re&re in a 22 classic is a bit of a b!tch. Also the fitment wasn't great and you lose the ability to pressurize and drain the raw water. They're heavier then the stock manifolds as well. With the headers, labbed prop, and K&N we picked up 2-3 mph. It's hard to say what the exhaust alone did, I should have tried a back to back test. On an older Z25 with an HO I removed the turbulators, spent an hour or so porting the stock exhaust where it merges at the riser, and had the rev limit raised. It picked up 1.5mph for a fraction of the cost. The CMI's do look nice though, and sound better too.. I guess it all depends on your budget.. :cheers2:

 

[jrz]

I am not saying any dyno results were faked here! As many of you know, there are different ways to set up a dyno calibration on any given run and also depends on how the engine is equipped on the dyno, when was the last time the dyno was calibrated, etc.,etc. We tried very hard to use SAE standards on our dyno tests, a properly calibrated and tested dyno and running the headers wet for real world results. How others ran their dyno tests on what in testing the CMI's with those dyno runs, I don't really know or care. What really counts is how the various boats and engines respond in the boats and under real world results in a lot of real world boats the results were for the most part as follows: 1. no change in performance. 2. 1-3 mph increase in performance. 3. A nice cool idle sound and lots of bling.
These are the results that really count, everything else is just talk and dyno numbers! You can take that to the bank baby!

Best Regards,
Ray @ Raylar

All of the major marine engine manufacturers testing of the 8.1's, along with the development of the GM HP3 496 were done on uncalibrated dynos?

 

[PARADOX]

Dyno / lab condition is just that. "Maximum" possibility within controled environment. Just like Ray was stating. As far as ANY CMI systtem... run like hell. Sooner or later, you will be buying a new motor.
However there is a nother way to look at the so called HP gain issue. Any given motor, let's say 496 or a 502 will put out "X" amount of HP. Unless it's blown, but from a 502 block the max theoretical HP you can get is (I assume) +- 1000HP. not you start "loosing" HP with all the moving parts. So I don't think it's how much HP an engine is gaining.. it's more like how much HP you'r not loosing.
Power steering pump, oil pump, fuel pump, alternator, rocker arm/lifter movement, rotating counterwieghts, pushing out exhaust. etc. Now you'r down to 1000 HP minus all HP lost to the motor actually running and working.
So.. the least HP you loose, the more HP you have for the props. I don't think HP can be "added" (again, unless it's blown or something) it's how little HP you loose adding High Perf. parts. You can't get a V-8 to get you a V-10 performance with all things being equal. No HP gain.. less existing HP lose is the name of the game. In my .02

 

[CRC]

Pismo, yes I have Q&Q which I only use at idle or minimum planing speed now. I also had it to begin with so I don't think that it would negate any power gain. Ray, your input is always appreciated. I never said that the dyno sheets were fudged; Just wondering where all that extra hp was? As much as I wanted to say that I gained something the fact is that it did nothing for my boat's top end. I changed nothing else when I did the headers and I saw no gain.

 

[Wayne Pennell]

Debate

CRC; I have debated this on forum's and in my head over and over. My finding are exactly what you say....no real world gains. In my mind, the ONLY way one could gain MPH is by being on the very edge of a prop selection...say running a 24P at 5050 RPM and doing 65 MPH. Now adding the CMI's net you a few RPM's and now you have to run a taller prop i.e 26P and can turn that at 4900 or 4950 at 67 MPH. That would be the only way I could see to gain anything. I have chosen to go a different direction with gain with an extension box.

Nice thread

 

[CRC]

CRC; I have debated this on forum's and in my head over and over. My finding are exactly what you say....no real world gains. In my mind, the ONLY way one could gain MPH is by being on the very edge of a prop selection...say running a 24P at 5050 RPM and doing 65 MPH. Now adding the CMI's net you a few RPM's and now you have to run a taller prop i.e 26P and can turn that at 4900 or 4950 at 67 MPH. That would be the only way I could see to gain anything. I have chosen to go a different direction with gain with an extension box.

Nice thread

Thanks. I chose a different direction too...:sifone:
http://www.youtube.com/watch?v=i7H6zNFH8f0

 

[Raylar]

I guess I am always amazed how sometimes the stock 496HO 425 gets compared to a Mercury Racing HP525EFI. Heck, that comparison is really an apples and oranges comparison.
First the HP525EFi is 540HP right outta the crate, thats 115 more than the stock 496HO. Yah it should make more power and speed it has more. Its also a hell of a lot more expensive, ie the apples and oranges comparison!

Just some food for thought here. Raylar took two absolutly stock 496 MAGS !! for Sunsation, $5K less than 496HO, equipped them with the Raylar HO525 standard off the shelf kits and stock exhausts and reprogrammed the ECM's and put some nice bling on the engines with powder coating and relocation kits. Sunsation installed them into a 32 SSR (awesome boat!)Sunsation with standard BRAVO 1X drives and Hawkeye took the boat to LOTO last year and ran 96 MPH. Just a mile or two faster than the same boat with HP525EFI's with Bravo XR Sportmasters. How did that happen, well its because the 496's properly upgraded will run with or outrun most HP525EFI's especially when equipped with a good set of headers like the HP525EFI.

Don't believe me, call Joe at Sunsation or the guys a Hawkeye Boat Sales and they will confirm along with all the other observers at the Loto Shootout!
Whats the point, a customers wallet will have a fatter side view due to the extra cash still in there! About $40-50K on the average twin engine boat!
If that cash ain't important to Ya, Could I please get you to put in in a plain envelope and donate it to the Raylar needs capital Foundation, we accept all chartible contributions!
GET your 496 up to comparable numbers, then lets make the comparison!

Best Regards,
Ray @ Raylar

 

[jrz]

I guess I am always amazed how sometimes the stock 496HO 425 gets compared to a Mercury Racing HP525EFI. Heck, that comparison is really an apples and oranges comparison.


The comparison is to a GM HP3 8.1 engine, not the 525, I know the difference.

 

[CRC]

I'm not comparing the 496 to the 525. It's just the route that I chose to go after talking to a lot of folks. I found a vintage 2007 motor with 30 hours for 20 grand. That's all I'll say here since my intention in starting this thread was not to compare engines but to discuss the claimed power gains from CMI headers on the 496.

 

[Wayne Pennell]

Just some food for thought here. Raylar took two absolutly stock 496 MAGS !! for Sunsation, $5K less than 496HO, equipped them with the Raylar HO525 standard off the shelf kits

I am not wanting to do the entire kit just yet, is it worth just a Raylar cam change for starters?

 

[jrz]

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.