496 Mag HO
 

:evilb:
does any body know of performance upgrades for the PCM555 computers on the 496 Mag HO

Re: 496 Mag HO
 

www.whipplesuperchargers.com

The only ones that I know of who have the rights to make modifications to the pcm555.

Re: 496 Mag HO
 

Reprogramming your ecm on a 496HO won't do much until you change some engine parts, like heads, cam and intake. You might wan't to check out our BCK103 kit, turns a stock 496HO into a 525HP+ 496HOR real nice.
Ray @ Raylar www.raylarengine.com

Re: 496 Mag HO
 

OK I finally did it!!!
I just sent my PCM555 out to Dustin Whipple and will have it back by the weekend (weathers not going to be great though).
I have run my boat with GPS a number of times and know the average is 70mph with a pretty full load.
Last weekend I removed the exshaust restriction plates (Turbulators) and seen a 2mph increase.
With the two mods I will do some GPS runs and let you all know what the real deal is.
I have been waiting for someone to do some real boat testing on the PCM re-programming and thermostat change but could not wait any longer :evilb: .
I will post again when the water flies.

Re: 496 Mag HO
 

BHOCKETT,

Can you give us some detail specs on you boat/engines?

Mike

Re: 496 Mag HO
 

2 mph with removing restrictor plates... any chance it was cooler out and that helped also ?

Don

Re: 496 Mag HO
 

I question 1-3 mph results on anything. Boating is hardly a controlled environment. My top speed can be plus or minus 2 MPH from day to day. I am thinking about taking my plates out but I may wait till the warranty expires.

Re: 496 Mag HO
 

I was going to take mine out this spring before I put the boat in the water. I decided I would wait, this way I can do a before and after test with a GPS. I'll post my results which will probably be next week.

Re: 496 Mag HO
 

The boat is a 2001 Checkmate 240ZT with a 25 Mirage Plus that was lab finished by York Propellers and the 496HO has 116 hours.
The 2mph increase I seen was an average for several runs during the whole day and the temp was in the upper 70's.
I know there are several factors that lead to a good reading and that is why I stated that I would post again after more testing was done. I’m one of the biggest skeptics and that’s why I had to do it myself.
Beside the GPS the seat of the pants meter also told me there was some increase in power throughout the upper RPM range. After 116 hours in the drivers seat you can feel when everything is running good.
When I removed the plates they did not show any sign of water as they had the black soot from the too rich PCM programming. I think these things are restricting the output in a big way. Have you ever tried to produce over 400hp with 2 1/4" exhaust?
Before, when I ran with the electric select closed and going threw the prop there was a 2-3mph drop in speed prior to removing the plates, and that is another test I want to do to confirm my numbers. Now that difference should be greater.
My hat is off to Whipple as he turned my PCM around the next day.
Now for the PCM testing, and I may put the plates back in so I get a real test of before and after.
Maybe next weekend the weather will be better.

Re: 496 Mag HO
 

Keep us posted!

I'll report back next week on my results taking the exhaust restrictors out of my 496HO

Re: 496 Mag HO
 

BHOCKETT,
Any testing done this weekend?
Thanks

Re: 496 Mag HO
 

What about the noise when removing the restrictors? Any (significant) change?? Does anyone has the partnumbers for replacing the gaskets when removing the restricors?

Re: 496 Mag HO
 

We noticed a slight increase in sound on my friends boat. It appears to have picked up 150 rpm. The p/n is 27-862356. $4.73.
You probably won't need them if your careful though.

Re: 496 Mag HO
 

When I did mine, the old gaskets came right off without sticking at all. They seem to be made of a graphite type material They were in new like condition, and I just reused them. I didn't notice any change in noise from the motor, and I picked up approx 150rpm. No dramatic increase in speed as others have noted, maybe 1 mph. Don't look for dramatic changes, but it is so easy to do, why not?

Re: 496 Mag HO
 

No testing this last weekend as the weather sucked.
The good news is I did get the re-programmed PCM installed and the new low temp thermostat along with some water wetter to improve the transfer of heat.
I also replaced the seals between the heat exchanger and the water manifold, these leaked during the winter months but never during the summer and I heard this is common.
By the way when I measured the opening on those performance crushers (turbulators) they were only 2" not 2 1/4". I don't know if other years are bigger but, "come on!!!" I think a VW has bigger exhaust.
Started it up on the hose at home after installing the PCM and it did seem to be leaner at idle, hope there is less soot under the swim platform after a day out.
The only time out with the restrictors removed it did seem a bit louder and I was not the only one who noticed but again nothing big.
Can't what to try the mod's, may have to take it to the water during the week.

Re: 496 Mag HO
 

Okay any testing news or new insight etc....?

Re: 496 Mag HO
 

Just wondering did you get your test drive in??? How was it running??? Do you think the PCM reprogramming helped??? How about carbon build up on the back of the boat??? Last but not least what did Dustin charge for the reprogramming??? I know, alot of questions but I'm sure theres alot of people out there wondering the samething, thanks Jim.

Re: 496 Mag HO
 

How's the soot situation, I'm thinking about the reporgram just to get rid of this problem.

Re: 496 Mag HO
 

what octane are you using?
since i started running nothing but 87 i don't have that problem anymore.

Re: 496 Mag HO
 

I get soot with 91 or 87 octane, doesn't matter.

Re: 496 Mag HO
 

is it worse with 93?

Re: 496 Mag HO
 

Had the same with my 496 on the baja.merc rep said not to use 93 and when i put 87 in it i had less soot on the back.see if your local merc rep can reflash the computer and it will reduce the soot problem a little.at idle i would put on capt.choice so it would go out the prop instead of on the back of the transom.

Re: 496 Mag HO
 

I've checked locally about having my PCM reprogrammed, everyone tells me Dustin at whipple is the only one that can do it yet. Just curious if it helps or is it a waste of time and money!!!

Re: 496 Mag HO
 

When I first got the boat I was using only 92 Octane and had no noticeable soot. I have since switched to 87 Octane at the recommendation of several forum members. I now have more soot. But I don't think this has anything to do with the octane switch. Everytime I take the boat out I hardly do any idling. It wasn't until last week when I had to do long periods of idling that the soot buildup became VERY noticeable. So I think it's more a function of low speed idling and the PIG RICH A/F ratio's on the stock PCM.

Re: 496 Mag HO
 

We don't have 93 octane in AZ only 91

Re: 496 Mag HO
 

:eek:
probably the same.
gas is getting worse every year.

Re: 496 Mag HO
 

what happened to BHOCKETT? Like to know what the outcome was

Re: 496 Mag HO
 

Paging BHOCKETT, whats the update how did she run???

Re: 496 Mag HO
 

Well I pulled mine off tonight. I am going to get them polished and then I'll let you know if there is any change. I will say I will be shocked if there is a difference. What is the story on the two and a half inch horn on the end of the riser? I have never held a riser from any engine in my hand before so that may be a dumb question but I just thought it too looked like a bottleneck. My thought would be none of these things would make a hell of a lot of difference unless you start trying to make some more horsepower.

Re: 496 Mag HO
 

Be careful everyone that says that they'll post there finding have never returned???? :eek: Keep us up to date. :D

Re: 496 Mag HO
 

Well I guess they either sank or the boats were so fast it scared them. :D I won't be reporting back in until I get back from Cumberland on Sun. night......That is if I'm able.

Re: 496 Mag HO
 

Thats cool have a good time!!! :drink: :D :drink:

Re: 496 Mag HO
 

i found about 100 rpm's but have not really played with it to much,but its was so much more hp that it cracked a blade on the prop! :eek: :D:

Re: 496 Mag HO
 

NICE!!! Unleased a monster did ya... :evilb: :evilb:

Re: 496 Mag HO
 

Well I think I will be the first to put them back in. I didn't get a perfect test in as I was carrying a little extra gas but I am sure I didn't gain a thing. I even think I may have lost a little torque. My hole shot seem to suffer and I am not that sure I gained anything on top. I will say getting them polished adds a little bling to an UGLY engine.

Re: 496 Mag HO
 

Well that sucks, thanks for posting back. Polishing sure would clean things up a bit!!!