EFI/MPI difference?
 

What is the difference of the injection system from a 454/502 EFI/MPI magnum 385/415hp and the EFI system that comes with the HP500/HP525?
How much HP can be made with the 454/502 EFIection if the injectors, map and fuel pressure is changed?

Anybody tried to run a rectangle intake on large oval heads with good result and how much power will I loose ofhe mismach ? the reson I ask is that I want to use my EFI/MPI injection from a 454magnum 385HP on a modified 454 with Brodix RR large oval alum heads.:party-smiley-004:

Come on, there must be some EFI guys who can help me with ansvers:kiss:

dont really understand your question but I think you mean whats the diff between efi and mpi? MPI is multi port injected....meaning usually one injector per cylinder. EFI electronic fuel injected can be either multi injectors or a single throttle body injected. Al least thats what I think but I'm a auto tech mainly.... Boat tech on the side. I'm sure some one else will chime in..........

the intake is the limiting factor in the 415 HP 502.

to make much over mid 500's without forced induction will be hard.

:party-smiley-004::party-smiley-004:
If I'm understanding the first part of your question properly
EFI (electronic fuel injection) generally refers to an induction system which introduces the fuel prior to entering the intake manifold similar to a throttle body type system
MPI ( multi port injection) utilizes a seperate injector in each intake runner typically aimed at the intake valve
Hope this helps

no,,, the first 502's has efi on the manifold,,,, then switched the sticker to MPI,,,,, same thing.

Its all semantics,,,,, all MPI's are efi,,,,but like said above,,,, efi can also be throttle body

MPI = multi port injection

EFI= electronic fuel injection

You can use the efi system just fine on your heads. Merc did it on several oval port engines. You'll need to get it tuned properly for your current engine. I believe the injectors are large enough. I'm sure you'll give up a little HP but it should work OK. I've done several 502's that made over 500 with that intake.

Thanks, I will try to use the 415 EFI/MPI in combination with my oval heads. I still wonder what the difference is between the 415efi/MPI and the 500/525HP EFI/MPI system. The 415 has throttle body to starbord and the 500/525 has straight throttle body but I guess thats not the only difference?:cool-smiley-011:

cam,heads and programming of ecu are difference.

I am using the Big Brodies on my 502 MPI system. They are the BBIIX's. It makes 942hp.

But I also has to stroke it to 540, do the injectors, cam, cut down and bore out the runners, better exhaust, have some serious programming and use 9 lbs of boost along with a whole bunch of other goodies.

For N/A purposes you can do the heads, cam exhaust, injectors, intake work and a few other goodies to get some pretty good power.

Young Performance did my work.

3 years ago I did exstensive work to a 2000 502 mpi intake. I had throttle body bored out, full ported the intake manifold and I had already converted the whole thing to twin rail fuel injection. I dynoed it blown and N/A. N/A I was able to make 657 hp/665 ft lb's of tq. This was on a 540 cu inch motor with only 8.2-1 compression but it did have a very large hyd roller cam and afr 315 cnc heads. There was a 10 hp gain going from a stock throttle body to the bored out one. Also,this was using CMI marine headers, thin,lightweight synthetic oil, no accessories on motor& sae j-607 was used so keep in that in mind, equivilant motor turning the water pump,power steering and alternator would be more like 620 hp or so,Smitty
I have bored out 454/502 mpi throttle bodies available also if anyone doesn't have a source to have one done locally.

carbs
 

while we are on the topic ==== would you make more power, and save a boat load of money if you bolted on a victor type (single plane) intake
and a big carb... comparison,,, heads, cam,exhuast= carb
against keeping the efi???

If you sought out the best intake you could find,sized and jetted your carb perfect,you could easily make 30 to 50 hp over a modified mercruiser mpi system. Now if you used that same intake,bought a billet throttle body,got a tuning program,tuned it to the nth degree,you could come very close to equalling the carb set-up,both would take considerable modifications to the fuel lines,throttle linkage,etc,etc. But as far as this discussion,a carb isn't a option. The carb vs efi debate has went on here for ever, i'm not going to argue one over the other but I will tell of my recent experience. I bought a restored 74 trans am,carbed 400 pontiac. The thing coughs,stumbles,runs rich,runs lean,is a real pia to drive (everyone has become spoiled driving modern efi vehicles). I went thru the carb,ran better but still suxs overall. I am pretty good setting carbs up and tuning them although I haven't done it much in past 10 years as almost EVERYTHING I work on is efi anymore. I was real busy with other things that actually earn me money so I ordered a done up quadrajet carb from one of the "pro's" that build them up,this thing is still miserable to drive. My 22 y/o son (who has NEVER had a carbed vehicle) pizzes and moans so goddamn much every time he drives the T/A that I can't stand to hear it. I'm building a 600 hp motor for it,and rest assured,it is getting a edelbrock super-victor efi intake,a fast billet throttle body,rail fuel injection etc. I have had plenty of carbed vehicles in the past but the bs that comes with it is very annoying,Smitty

Articfriends how much more do you bore the throttle body out? What Cfm do you get out of it?
Thanks

My notes from the guy I have that does it says the original bore size is 2.350/new bore size is 2.570. He tells me the stock one flows 1265/modified one flows 1513 cfm,a 249 cfm increase
I think this was calculated flow as most throttle bodies are NOT actually flowed on a flow bench. I can tell you it was worth 10 hp on the dyno over stock ,keep in mind though my manifold was full ported,cam was big,afr 315 cnc heads and it was a 540. I don't really know if it would make a true difference on a stock or near stock motor,there might be other things that are more restrictive,Smitty

Can you give more specs on your MPI that pushed 6XX HP?

I can't post pics anymore as I don't have the right kind of membership but in short detail I built a 540 w/afr 315 cnc heads,hyd roller cam with numbers in the mid 250's for .050 lift duration,.654 valve lift,bored out 502 mpi throttle body,milled down and all out ported 502 mpi intake,custom twin rail fuel injection w/63 lb injectors, 8.2-1 compression,j/e reverse dome blower pistons w/swain tech coating on skirt and crown,middle of the road 4340 crank and rods. Converted to mefi-4 ecu,dynoed w/2 ecu's, 1 N/A,one with procharger. On Tyler Crocketts dyno motor made 657 hp/665 ft lbs of tq. This was thru his CMI stainless headers turning no accessory's w/thin synthetic oil at the generous sae-j-607 (60 degree) dyno factor. My 272 Baja runs gps mid 70's w/this set-up,it ran 62 years ago w/bone-stock 502. Motor made 1114.7 hp at 5900/1037ft lb's of tq at 5200 runnning 13-14 psi of boost and a 20% race gas/80% 93 octane mix,made 1056.68 hp at 5700/1009.07 ft lbs of tq at 5200 on 93 octane and a slightly bigger upper pulley,my boat has ran 99 mph w the 1056 hp set-up. You can make power using a 502 mpi system but there are alot easier ways to do it. The N/A version of my motor has some weird spots in the tq curve where it looks like it peaks,drops a little then peaks again 1500 rpm's later,Smitty

Is Tyler the one who did the build? Thats the most hp I've ever heard of from the MPI, if you have a few pics from the build e-mail them to [email protected] Thanks

I did the build, used tylers dyno to test it and he did the ecu tuning. as far as pictures,if you search my post I have posted countless pics in the past on here of this project,it would have been in spring/summer of 07 and previously 04 or 05. I will try to send you a few pics though too,Smitty

About 2 years ago, I did a similar build to articfriends. It started life as a 502 Mag MPI. It is now 540 ci, Brodix BB2X heads, hyd. roller cam, Mefi 4 ecm with modified rails and 65lb injectors, ported 502 Mag intake with shortened runners, M3 Procharger with 502 intercooler, 8 1/2 psi boost. It made 945 hp. I will put up some pics later.
Eddie