I'm looking to put EFI on a 540 tall deck (Merc Bulldog). The target hp for the motor is just abit over 600hp and it is planned to have CMI sport tube headers or similar and original heads (if poss)

The choice of efi seems to be narrowed down to the following:

• Holley Commander 950, 2000cfm, 42lbs injectors
• Edelbrock Pro Flo2 EFI (Not sure if available in tall deck)
• Accel DFI 77203EB
• FAST 3011572-10

Ignoring the differences in cost, which of these systems is best?
Firstly, in terms of power producing capability, I dont want the manifold & TB holding the engine back. Secondly in terms of build quality.
At the moment, I'm veering towards the holley, with the edelbrock 2nd if it's available in tall deck, but don't have firsthand experience of any of them yet.

Thanks
Matt

thank you for providing the links. if i use the specs only , it would seem to me that the edlebrock system makes a good deal of sense. better than the others. but having said that, the quality of the connectors and sensors will be crucial for reliability as well as determining whether they use off the shelf bosch sesonrs or gm sensors ( inexpensive ) or proprietary stuff ( expensive) . the connectors will likely not be mil spec or even packard weather pak which will cause you issues in short order in a salt environment.

efi is absolutely the best way to go in all respects but the marine environment is harsh and corrosion and and poor connections will really really make your life miserable in short order if the hardware isn't set up for it.

the edlebrock system has a lot of user friendly and straight forward tuneability... especially the abilty to flash the ecu with a new map on site easily. but all that means nothing if the harness and connectors can't tolerate a wet and corrosive environment.

I use the Holley MPI kit. You must have a loptop to program the sytem. It takes some time to get everything adjusted. The timing and fuel maps are completly adjustable on the fly. I use the 1000cfm thotlebody with 42lb injectors on a 489 stroker engine.

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Hey Matt,
Fly into St Louis tomorow and I will show you how to do a little programing. I hope to be doing a test run tomorow with my new cam.

Unfortunately, all of these systems utilize single plain manifolds designed for carbs, then converted to EFI. So they're all going to be compromises. The runners are different for each cylinder, and plenum volume is WAY too small for max HP with EFI.

There's a reason EVERY production EFI system from cars to Merc. use a manifold that looks completely different than a carb setup, and it's not just to be different.

As far as programability is concerned, the only one of these I've used is the Accel, and it does what it needs to do for the automotive applications I've used it in.

I'm sure they'd all work to some degree, but as far as HP is concerned, I'm pretty sure they'd all be a toss up. If that's all you're looking for, just research the basic intake manifold as it is used in it's carb'd form. You'll end up with about the same HP.

If usability is a concern, you need to figure out what is important to you. I'm sure each system has it's plus's and minus's. The simplest system to program will probably also be the least flexible.

Regardless of the system you choose, remember, all of them are designed for automotive use. For marine, you need to make sure the ECM is away from any moisture, and that it's fairly well isolated from vibration, which is much more severe in a boat engine compartment than in an auto. Also, make sure the one you choose does not rely too much on an O2 sensor for continued use, but has the ability to use a wideband sensor for tuning. O2's (especially Wideband) are great for tuning, but do not work for long in a marine environment with continued usage.

A great response, thank you.

I completely agree with your comments regarding choice of manifold. My original plan was to use the arizona S&M tpi manifold & 1300cfm throttle body, however a previous post indicated that this manifold & TB combo really can't flow enough air - it's absolutely maxxed out @ 600hp with high vacuum measurable in the intake. So that rules that one out.
That post, plus other conversations, suggested the holley 2000cfm setup was the one to go for over the 1000cfm, but I'm not sure where the changeover point is to go from the 1000cfm to the 2000cfm combo (on the holley system)

I would love to go with a kinsler efi setup, but I need to be pragmatic, and the $$ to go with that setup appears to be pretty prohibitive - I also really would need a crossram setup to keep the whole lot under the engine hatch, and they're even more proud of the crossram (rightly so, it's a work of art).

Unfortunately I don't know of any other TPI manifolds (the GM Ramjet manifold is oval I believe, my motor is rect), so that left me with the more "standard" style efi setups I listed above. Unless I start looking at tunnel ram manifolds with a TB on top, or a hogan fabricated one - I don't know much about either unfortunately.

I'm not at all concerned by the ECU or wiring side of things - the ECU will be well away from the motor and fully protected, and I'll almost certainly be making my own loom to fit. I'm also not worried about the software, I've built a megasquirt before so am fairly comfortable with tuning software and don't need it to be programmed just for dummies.

I'm kinda getting the feeling that the most perceived difference between the different combos I listed is in the ease of use of the software, and that the manifolds, TBs, injectors & fuel rails are all much of a muchness - which is a shame, I was hoping one really shone above the rest, but I guess it makes it easier because I can base the my decision on $ rather than performance.

Thanks again
Matt

Do you know what's the upper hp limit on the 1000cfm manifold & TB before it starts to become restrictive?

I believe they're all more or less capable of on the fly tuning - historically edelbrock required you to shutdown to reflash the ecu, but to be honest even that's not a big deal. I'm mostly interested in which system, on the same engine (specs as per the original post), would produce the most power.

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