Dennis Moore, John B, and the HP500 EFI
 

The origin of this post is John B's post entitled "mercury engineering problems!" which I have said that I would not continue to post at, as I think that his choice of "topic" or "title" is inflametory (for no reason) and not supported by the post. I did offer to continue the conversation, and I am doing that here.

In that pevious post, Mr. Moore has a displayed an apparant personal issue with either (a) Mercury Racing, (b) Mercury Engineering talent, or (c) me personally.

Mr. Moore, as a freelance jounalist, I find your verbosity entertaining, however, I find your actual knowledge to be limited. If you could put your personal issues with Mercury aside, and you give this post more consideration than a Pep Boy's counter boy, perhaps we could make some headway.

Point in fact, let us look at the information posted by "John B" that has got us to this point:

a) his HP500 EFI is running at over 5400 RPM
b) his HP500 EFI dyno'd at over 5400 RPM
c) the spark plugs in his HP500 EFI appear fouled

Mr. Moore, as a self proclaimed "expert" in the field, and as a "Mercury Master Technician" (certified when?) I am sure the you know that the rev limiter of the HP500 EFI is 5250 RPM.

I have no need to be devensive. John B posted information as fact that can not be supported as presented. As a MMT I would have thought that you would have recognized that, unless this technology post dates your certification or you and John B have an alternative agenda. I welcome additional information from John B, however to refer to Merc Eng Prob's based upon HIS info, is to refer to you as a Mercury MASTER technician. Give me a break. HT called you out on this two weeks ago; I spoke to HT...perhaps you need to reevaluate your marketing strategy.

For the record:

I am prepared to converse the pro's and con's of the HP500 EFI at your leisure. HT stands at the ready as well, awaiting your next response and hopefully, your next demonstration on Mercury envy.

You have issues...come with facts,
expect no mercy. We grow tired of rhetoric...

Who the hell is HT?

Dennis Moore,

I am staying out of this one. I'm just reading the posts to learn a few things. But, I think when Adivanman referred to "HT" he means High Tide from the other thread regarding this topic.

Guys,
The Mercury Technical Department told me two years ago that the rev limiter on the 500 efi cuts the fuel system back at 5420 and turns it back on at 5250. Is this wrong? This seems to be what I have found, but I know that analog tacks are not very accurate. Anybody?

I posted on the other sight because I didn't see this first. Sorry

HT,
Glad you could join us.

JohnB,
The has not been my experience. The HP500 EFI has a 5250 rpm ignition referenced rev limiter. I have never experienced an engine capable of exceeding that ignition based limit (and believe me I tried at Bradenton - repeatedly). 1999 based.

Formulafastech
I guess that I am the only only one who noticed that trend....

Some more info on Rev Limiter. Check out Dustin's / whipple charged post #6.

http://www.offshoreonly.com/forums/s...ev+AND+limiter

paradigm shift,
In this/that particular case, I believe that Mr. Whipple was incorrect. I can safely say that I have hit that particular limiter harder and more often than anyone you will meet. Your reference is kind of cool though...those were the days...Truckin...mini trucks, neon, and thumpin toons....must have needed a brake from his MMT duties. LOL

Troutly,
You need to find the leak...

Looks like the dyno test is not bogus after all.

Which one of you would, design a system to, cut off some of the fuel at 5200+ under max load with exhaust temperatures in the 1450's?:eureka: :frog: :crazy:

Thanks for the above information.

Anybody know about the rev limiting on the 525 EFI?

Fuel-cutting rev limiters are not certain death unless you are running a nitrous motor. Bear with me here, I'm only entering this seething cauldron cause I see a spot that needs elaboration...

Pretend that you are a single cylinder motor. You are approaching your rev limit and are running borderline lean and have some eyebrow-raising exhaust gas temps. You with me here? Okay, you have now reached your rev limit and the limiting electronics enter. The next intake stroke, the injector refuses to fire and you get no fuel on that stroke. You have only ingested air. Your spark plug still fires, but there is nothing there to light off. You complete your rotation and pump the remaining unexpanded air out the exhaust port and suck in another load of air.

At this stage, the cycle of air through the motor has produced no power and has cooled, not superheated, the internals. There has been no imminent meltdown because unlike a carb motor, there was no lean ignition. There was no ignition of charge at all - there was nothing there but air. No harm no foul. If the motor is still over the rev limit it repeats this cycle again and again until the motor is under the cut-in limit. At that point, you have a normal cycle with normal fuel and normal borderline lean operation.

No meltdown.

Add a blower. Does this change anything? Nope. Same situation.

Add nitrous. Does this change anything? Yep. Now you blow the crowns off of the pistons when the fuel injector doesn't fire and you get a load of nitrous plus just enough fuel from the spray rail to let her light, but not enough to keep her cool. Run this puppy into the rev liiter and you'll have some souveneirs. A way around it? Sure, add a rev module to stop the nitrous (and additional fuel) flow 100 rpm below the fuel cutoff. Now you got a 2-stage rev limiter. Mission accomplished.

Nothing wrong with fuel cutting rev limiters. Why would Detroit have them in ALL of their automobiles like this when it would be just as easy to add ignition cutting rev limiters???

There, I'm back to watching from the sidelines again...

Good post Mcollins!

Is the GM system to which you referred the same type of system that they are planning to use for their upcoming "displacement on demand" that will cut out cylinders when the engine is under light load? I wonder if this could ever apply to a marine environement. My guess is probably not, since a boat engine is almost always under load.