540 MPI Can I do this?

[Ted]

The engine tech forum seems to be hopping pretty good and I am about to dig into my winter project so I am looking for some input. Any and all discussion is appreciated, let's build me some engines :sifone::smash:

Alrighty, so I have 2 short blocks I need to redo. Bone stock 1st Gen 95 502 Mag MPI with VST systems, not the cool fuel deal. (Never vapor locked on me) The heads are stock and fresh with stainless intakes, inconel exhaust, and a little port cleanup only. My idea is to build the short blocks into 540's and change to a more modern roller cam set up. Still keeping compression down so I can run 89. I have standard Stainless Marine exhaust on it now. So here are my questions:

1. Can the MPI computers be reprogrammed for the higher C.I. ?

2. Can the fuel system feed them?

3. Can I get a cam profile that will get me around 540-550 HP with these heads and compression? (Don't want or need any more power-can't believe I just wrote that!)

4. If I am off base here, what would you do differently?

I would like to keep this project reasonably priced (not cheap, no such thing in boating) since the boat is not worth that much and an upgrade is always on my mind :sifone:


So can ya help a brutha out???

 

[Chris]

Call Bob Madara.

But you're on the right track with the 540 idea. By the time you're done, you're going to have ended up adding a set of aluminum heads into the recipe. There's too much benefit to be had for the difference in price.

I have zero experience with the MPI systems. That leads me to believe they do about what they're designed for and not much more. But there seems to be no shortage of the 500/525 EFI systems out there that you can upgrade to

 

[Spicy]

http://www.seriousoffshore.com/classifieds/index.php?page=out&id=555

 

[Ted]

Call Bob Madara.

But you're on the right track with the 540 idea. By the time you're done, you're going to have ended up adding a set of aluminum heads into the recipe. There's too much benefit to be had for the difference in price.

I have zero experience with the MPI systems. That leads me to believe they do about what they're designed for and not much more. But there seems to be no shortage of the 500/525 EFI systems out there that you can upgrade to

I am hoping to stay away from AL heads only because of the water I boat in. And I am not looking to make that much power. The MPI system can be tuned some, and maybe with a little more fuel pressure I'm thinking it can do what I need it to. Really don't want to go to carbs.

 

[Ted]

http://www.seriousoffshore.com/classifieds/index.php?page=out&id=555

Thanks Pat, that is what I'm thinking about but since I have a good machine shop I am thinking about doing them "in-house" (Ted's Garage) :sifone:

 

[Spicy]

Thanks Pat, that is what I'm thinking about but since I have a good machine shop I am thinking about doing them "in-house" (Ted's Garage) :sifone:

I just read that and thought that was resonable but what do I know??? The way I read that is you drop your old 502 to them and they switch everything over and dyno your new 540 for 6K x 2= 12K and your done but a little labor...

I can tell you I had alot more then that in my boat when I repowered last summer...

But you have awhole lot more expierance in this than I... I still have to go to the Marina this weekend and figure out where to put the Antifreeze at??? :ack2: :sifone:

 

[t500hps]

Yes the computers can be programmed but you really MUST send an entire engine to be dyno/tuned. Fuel system I know nothing about. With ported heads and 540CI your looking to make 1hp per CI (or just over)...not really a problem if you can get enough air in there...but the 502 intake will be your biggest problem. You should beable to run 9.0-9.3 compression and run 89 all day long.

For comparison, I have 500efi's made into 540's that look stock. Ported iron eagle heads, 9.75 compression, decent size cam, monoblade intake trying to get more air in and the stock fuel system.....fully dressed on a dyno it made 700 ft/TQ (4,300), but only 630 HP (5,200). Your intake is much worse than mine. If you know Mike MAngini on the upper bay he made 540's from his 502 mag...ended up scraping the EFI and going to carb's because of various problems.

 

[Tyler Crockett]

The engine tech forum seems to be hopping pretty good and I am about to dig into my winter project so I am looking for some input. Any and all discussion is appreciated, let's build me some engines :sifone::smash:

Alrighty, so I have 2 short blocks I need to redo. Bone stock 1st Gen 95 502 Mag MPI with VST systems, not the cool fuel deal. (Never vapor locked on me) The heads are stock and fresh with stainless intakes, inconel exhaust, and a little port cleanup only. My idea is to build the short blocks into 540's and change to a more modern roller cam set up. Still keeping compression down so I can run 89. I have standard Stainless Marine exhaust on it now. So here are my questions:

1. Can the MPI computers be reprogrammed for the higher C.I. ?

2. Can the fuel system feed them?

3. Can I get a cam profile that will get me around 540-550 HP with these heads and compression? (Don't want or need any more power-can't believe I just wrote that!)

4. If I am off base here, what would you do differently?

I would like to keep this project reasonably priced (not cheap, no such thing in boating) since the boat is not worth that much and an upgrade is always on my mind :sifone:


So can ya help a brutha out???

Ted you can program the Mefi 1 to work. I would put the cool fuel on thou when going to the 540. I have some used cool fuel stuff around.

 

[YoungPerformance]

The problem you will run into is the intake. That manifold will severly limit your power potential. There are quite a few things that can be done to the intake to help it flow. However, personally, I think it is a waste when it can be replaced pretty reasonably. You can extrude hone the intake (about 800-$1000), bore out the throttle body(200-300), shorten the runners(100-200), and do some hand blending (200-300). These things will drastically help the manifold. However, even with all of that, I have never been able to make much over 600 hp......ever. At some point you will need injectors. The problem is there are no drop in injectors that will fit that manifold. I modify, drill, cut, weld, mill,etc. the fuel rails and manifold to make a Mototron injector fit. It turns out great, but it is a bunch of work. So...... now we have over $2000 tied up in a so-so manifold. For about $2500-$2600, you can replace it with Holley's setup. I buy there manifold setup without the electronics and use a Mefi. To answer your other question, no problem to reprogram the ecm. I order them with the manifold, 2000 cfm throttle body, fuel rails, injectors, croosover tubes, IAC, TPS, ECT (coolant temp), Map sensor, IAT (intake air temp). It is a dynamite setup that can make as much power naturally aspirated as you would like. I have made over 800 hp with one. Without doing the above work to the MPI intake, I don't think you will see 550 hp, even with a 540.
If you were to get the Holley intake setup, then you could just bore the engine to 516 or 525 and skip the 540. This will save you a ton on money since you can reuse the crank, balancer, flywheel, rods, etc. Just replace the pistons. I would bump the compression to 9.3 for premium, or 9:1 for 89 octane. If you did a little cleanup in the heads, you could make over 550 hp without even trying. With a set of aluminum heads, you could make well over 600 hp.
This is the route that I take on the majority of 502 MPI's that I see. Once I explain it in dollars and cents, most see that the Holley setup is the way to go. Let me know if you have any questions or if I can help in any way. Good luck.
Eddie

 

[Ted]

Ted you can program the Mefi 1 to work. I would put the cool fuel on thou when going to the 540. I have some used cool fuel stuff around.

Tyler, I know you have done lots of flow work with manifolds and what not, what is your take on the flow restrictions of the MPI manifold that tHP500 and Eddie are talking about?

 

[Ted]

The problem you will run into is the intake. That manifold will severly limit your power potential. There are quite a few things that can be done to the intake to help it flow. However, personally, I think it is a waste when it can be replaced pretty reasonably. You can extrude hone the intake (about 800-$1000), bore out the throttle body(200-300), shorten the runners(100-200), and do some hand blending (200-300). These things will drastically help the manifold. However, even with all of that, I have never been able to make much over 600 hp......ever. At some point you will need injectors. The problem is there are no drop in injectors that will fit that manifold. I modify, drill, cut, weld, mill,etc. the fuel rails and manifold to make a Mototron injector fit. It turns out great, but it is a bunch of work. So...... now we have over $2000 tied up in a so-so manifold. For about $2500-$2600, you can replace it with Holley's setup. I buy there manifold setup without the electronics and use a Mefi. To answer your other question, no problem to reprogram the ecm. I order them with the manifold, 2000 cfm throttle body, fuel rails, injectors, croosover tubes, IAC, TPS, ECT (coolant temp), Map sensor, IAT (intake air temp). It is a dynamite setup that can make as much power naturally aspirated as you would like. I have made over 800 hp with one. Without doing the above work to the MPI intake, I don't think you will see 550 hp, even with a 540.
If you were to get the Holley intake setup, then you could just bore the engine to 516 or 525 and skip the 540. This will save you a ton on money since you can reuse the crank, balancer, flywheel, rods, etc. Just replace the pistons. I would bump the compression to 9.3 for premium, or 9:1 for 89 octane. If you did a little cleanup in the heads, you could make over 550 hp without even trying. With a set of aluminum heads, you could make well over 600 hp.
This is the route that I take on the majority of 502 MPI's that I see. Once I explain it in dollars and cents, most see that the Holley setup is the way to go. Let me know if you have any questions or if I can help in any way. Good luck.
Eddie

Eddie, your idea is intriguing but my thought is that if I go to more cubes and run it at around 1hp/CI it will be more reliable than going 1.1 hp/CI like a 509 for the same power output. I have heard the 502 Mag stuff is decent but do you feel the Merc stuff would hold up okay at the higher output? And would that horsepower be at a higher RPM if I go with the smaller displacement or are you getting the power from the efficiency?

 

[t500hps]

If it's a budget build....I'd leave it a 515, re-using the crank and rods (those along are over $1K) and spend the money on an intake like Young is talking about. If 550 is your goal on 89 that will be easy and reliable.....getting 600hp wouldn't be that hard a push if you do some port work to the stock heads. Remember and engine is just an air-pump......If you can't get air in, it doesn't matter what the rest of the parts are.

and BTW: more CI means more TQ (again, only if you can get enough air)....what drives are you running and can they handle it?

 

[Ted]

If it's a budget build....I'd leave it a 515, re-using the crank and rods (those along are over $1K) and spend the money on an intake like Young is talking about. If 550 is your goal on 89 that will be easy and reliable.....getting 600hp wouldn't be that hard a push if you do some port work to the stock heads. Remember and engine is just an air-pump......If you can't get air in, it doesn't matter what the rest of the parts are.

and BTW: more CI means more TQ (again, only if you can get enough air)....what drives are you running and can they handle it?

Well, this is part of the issue. I am running standard Bravos so I don't want to kill them. I may be thinking old school but a bigger displacement engine turning slower seems like it would be more reliable. And if I do a 540 kit I am looking at 1500 or so an engine, the Holley stuff is about 2400, so the 900 difference will cover my dyno time. :sifone:

 

[t500hps]

Well, this is part of the issue. I am running standard Bravos so I don't want to kill them. I may be thinking old school but a bigger displacement engine turning slower seems like it would be more reliable. And if I do a 540 kit I am looking at 1500 or so an engine, the Holley stuff is about 2400, so the 900 difference will cover my dyno time. :sifone:

More displacement makes more HP, but it makes ALOT more TQ. Torque is what will kill a Bravo, not necesarily HP. I'm fairly certain you'll make more HP with a 515/holley intake then you will with a 540/MPI intake. The MPI intake will run out of air before 5,000 rpm's so you'll need to make power early....but this also makes TQ (remember mine make 700 ft/TQ, I've already blown an XR). Using that 515/holley will allow you to setup the engine to spin 5,500-5,600 which will still be reliable, and the bravos will be much more likely to survive. (I spin mine 5,600 when I prop it for top end runs but everyday props max out around 5,250)

 

[jeffswav]

I use the Holley MPI kit that Eddie is talking about. I have the 1000CFM TB with 42LB injectors with large oval intake. I had to do some port work on the intake to match up with the heads. At the time the marine kit only came with 30LB injectors so I purchaced bigger ones and sold the old ones. Eddie recomended the 2000CFM TB, I am not sure what the limit is for the 1000CFM. I run 489 stroker up to 5400+ RPM. The Holley PCM is laptop programable and can be tuned with your laptop on the fly. You would want to have O2 bungs welded in your exhaust risers. If you get the Holley kit be sure to get the wideband O2 upgrade. You can even set your target AF ratio's and let the PCM make adjustments.

 

[Tyler Crockett]

Tyler, I know you have done lots of flow work with manifolds and what not, what is your take on the flow restrictions of the MPI manifold that tHP500 and Eddie are talking about?

Ted I did a whole 3 or 4 page artical on this 502 upgrade 8 or 10 years ago in Hot Boat mag. I put a kit together with a camshaft, bigger valves in the head, ex, roller rocker arms, timing chain, pushrods, valve springs, flame arrester, and a ECU program and we picked up almost 100HP and 100FT of torque. Now if you want to take the time to port the stock heads you can probally get 520HP . I would make the engine a 516ci because you have to buy pistons anyway. I have made 565HP thru that MPI manifold. Those injectors will work fine you just need to go to the cool fuel. If you put the Holley intake on you will make more HP but you will lose Torque. That's why those 500 and 525 manifolds work so good they have real long runners that you can't beat but you can;t get enough air thru that throttlebody to make more than 625HP. That's why I made a bigger throttlebody to bolt right on the top of the 500 manifold. You get the long runners for torque and the bigger throttlebody for more flow and HP. It takes 17 to 20 HP to get 1 MPH on the water so you may fall a little short of your 540-550HP but you can use everything you have. Also when you do the machine work deck the blocks to 0 deck to get the Quench area as small as you can to bring the compression up to 9.0 that will help a bunch.

 

[Tyler Crockett]

More displacement makes more HP, but it makes ALOT more TQ. Torque is what will kill a Bravo, not necesarily HP. I'm fairly certain you'll make more HP with a 515/holley intake then you will with a 540/MPI intake. The MPI intake will run out of air before 5,000 rpm's so you'll need to make power early....but this also makes TQ (remember mine make 700 ft/TQ, I've already blown an XR). Using that 515/holley will allow you to setup the engine to spin 5,500-5,600 which will still be reliable, and the bravos will be much more likely to survive. (I spin mine 5,600 when I prop it for top end runs but everyday props max out around 5,250)

The stroke of the crankshaft will make more torque and compression will also make torque. I think in the RPM range Ted wants to run in he will get 5200-5300 RPM of of the MPI manifold.

 

[mdgperf]

Ted you can easily make the 550hp with the mefi1 and your injectors,but as everyone that has worked with that old intake knows,the thing is junk!for making power,I once dyno a stock 502mpi made a little over 400,changed it over to intake and carb made 450,If i were you i would consider buying a intake setup from a 500 or 525 and use your harness and mefi,I have several on the shelf 2-500efi,2-525efi they are also arround from whipple upgrades,the holley intake works great too but for 550hp the 500-525 set-up is fine and will save some money,if someone has a 550hptune your best bet is to use that set-up,camshaft,heads,exhaust set-up or you will spend a lot of time tuning your combo.I have a 625 tune (afr heads,different cam,mono throttle body,55lb injectors,bigger fuel system)works great but not cheap.The merc cool fuel is good for about 550hp,would not feed my 625 ,tried it and fuel psi droping during dyno pull.I have plenty of low hrs cool fuel set-ups,not really sure about the the vst system for making power,might support 550.Another option would be is do a merc 500efi clone,great engine,i have that tune saved in my mefi burn alot of used good parts around and less time on your tune.Putting the 4.25 stoke crank in your 9.8 short deck is ok,it will help but the piston gets real short,I have done several but not a big fan,cylinder will wear a lot faster than the stock set-up but will still go 200-300hrs if not run too hard

 

[Geronimo36]

The old generation MPI's had the same bottom end as the HP500's before Merc upgraded to better rods, 731 cam and holley 750. Might be a good idea to upgrade to some manleys.

Last winter my buddy went to JC Performance hand had his 454 MPI massaged... Ported GM iron heads, 525EFI cam, bigger rail/injectors and it made 515 HP @ 5600. the boat picked up a good 10 mph over the 454 mpi and idled very well.

You should easily be able to get 550-600 hp with 540, 741 cam, 500efi intake and associated parts or put an 850 on top if budget is tight and go to town!!

My buddie's 522" made 600 hp with similar set-up, dominator and Merlin iron heads... nothing fancy..... Previously this engine was 509" and made 550 hp with a 741.

 

[YoungPerformance]

I use the Holley MPI kit that Eddie is talking about. I have the 1000CFM TB with 42LB injectors with large oval intake. I had to do some port work on the intake to match up with the heads. At the time the marine kit only came with 30LB injectors so I purchaced bigger ones and sold the old ones. Eddie recomended the 2000CFM TB, I am not sure what the limit is for the 1000CFM. I run 489 stroker up to 5400+ RPM. The Holley PCM is laptop programable and can be tuned with your laptop on the fly. You would want to have O2 bungs welded in your exhaust risers. If you get the Holley kit be sure to get the wideband O2 upgrade. You can even set your target AF ratio's and let the PCM make adjustments.

I don't use Holley's electronics. I order the manifold kit without the ecm and harness and I use a Mefi ecm and harness. I also order it with 50 or 55 lb injectors, depending on what engine it's going on.
Eddie