Supercharged Flathead EFI, Megasquirt

There, that thread title should have at least one word that interests everyone here.

I'm Flatdog's son Zack and I've been working on putting together an electronic fuel injection system during my time home from college (2nd year MechE at MIT). It's finally almost done and my dad has been bothing me about posting it to the HAMB.

I've been tired of tuning carbs since I started. Draining float bowls and switching jets to get an acceptable AFR for either the track or the highway (but not both) really sucks I and have been bothering my dad to get an EFI system for the car for several years. After getting some experience with the stuff on my school's FSAE team I just decided to start on it myself.

The first decision on the system was a MegaSquirt ECU. It's an open source hardware and software project where you actually build the ECU yourself from parts. That works a lot better for me since I can take care of any complications myself and everything I need to know about it is available to me. The whole ECU cost me $250 too, a savings of at least $1000 for a comparable ECU. I ordered the parts and got it all soldered together without a problem.



I decided to go with a sort of hybrid throttle body injection setup because it was questionable whether there would be enough room for injectors and a fuel rail under the blower plate. It also meant I didn't have to tear down the blower to put it all together. Port injection would be nicer but not enough for the trouble in this project.

For the record, it's quite hard to get four Strombergs on top of a 4-71. You'll notice that the carb runners are at a five degree angle to get them to fit and that the throttle rods are hard connected front to back (with provisions for my return springs). As always the aluminum welding was a pain, but much moreso because of the close quarters. The runners are only .060" too, joining into the 1/2" plate. The welds are only partial on the outside for some structure and are actually sealed all the way around on the inside. I'm not trying to fool anyone with the Stombergs, anyone who has a clue can spot the EFI from thirty feet away since the injectors and fuel rails hang out in the open. I used complete junk carbs that my dad just chopped up and painted. The butterflies had to be cleaned up but it came out looking very good (I'm sure you've seen some of the flathead EFI abominations out there) and quite cheap.





The system also controls spark, getting crank position from the MSD distributor and sending its output to the 6AL. This was the most difficult part to get working since the ignition system is so electrically noisy and interferes with the crank position VR sensor considerably.

The fuel system was modified for high pressure and a return line too. I ran new -6 hose from the high pressure pump and used the old fuel line for the return. I used an MSD pump and the system runs at 45psi. I was worried about the welds on the fuel rail bungs since I couldn't test them easily but it all came out without any leaks.

I've got about seven hours of tuning time on the system with my dad driving and me on the laptop and the low end is dialed in very well right now. I cruise the highway at about a 16 AFR. We just got into some higher end tuning tonight and the numbers are looking very good, already much better than they ever did with the four barrel. We still have quite a bit of boost retard to take out and if having a car correctly tuned does anything for strip times we should pick up a good bit. The work involved with tuning carbs meant we never really even approached something I would call correctly tuned. It's so nice being able to change fuel and spark curves from the passanger seat on the fly. I program any fuel or spark curve I can think of varying with both manifold pressure and RPM and as soon as I make the change the engine is already using the new settings. I'm trying to get some chassis dyno time for the last bit of tuning and hopefully will have some pretty graphs by the end of the week.

--Zack

 

I like it old look new fuel great Roger

 

Damn I love the high tech approach to oooooold problems!

 

Excellent - injection was going to be my next project, I've been running a distributorless Megajolt ignition on my flattie for some time.

 

Is that your garage? If so, I'm jealous.

 

Really cool!!!! congratulation!

 

love the idea, i had had the same idea using the megasquirt and some old 94s, but havent got around to it. would love to see what you get out of it.

 

Good job, Zack. Missed you at Bonneville this year. Wayno

 

Zack,

Well done. Nothing like brains & cheap labor to make things go well. Tell your dad I said, "Hello!"

Are you guys bringing that rig to Mangungie this year?

 

The Megasquirt is the best deal in fuel injection period. There's even a message board that they'll help you out with any problems.

http://www.msefi.com/

So don't be scared of jumping in. You can also just buy a box that someone else has already put together and tested if you don't like the soldering part...

 

Cool. I'm working on soldering a Megasquirt right now (v3, ms2) to control my (O/T for here - 93 LT1) engine. Glad to hear that the tuning is going well, that's one of the areas that I've been somewhat concerned about.

Are you using a NB or WB O2 sensor?

 

I'm using a LambdaBoy wideband O2 for tuning. My sensor is a bit flakey and I can't trust it with closed loop operation but it's just fine for hand tuning the tables for open loop. I can't even imagine trying to tune EFI without a wideband. It's one thing with carbs, you say "that looks a bit rich" and put in smaller jets, but when you've got an entire table to do you absolutely need realtime data.

 

Zack, looks great. I have some questions for you. When designing this system why did you decide to place the injectors above the blower? Wouldn't the system be more effecient below the blower with direct port injection? Running the injectors above the blower will allow heat from the blower transmitted to the atomized fuel and effect the total advance required to eliminate heat build up and detonation. Running one large injector above the blower would be easier, wouldn't it?

 

if your going to go that far, why use the 97's for throttle bodies. this is far from the most efficient setup, but it does look pretty cool.

 

I think the blower may need to compress the whole charge (fuel and air) but then that's just me.

 

nope, it doesn't.

 

Makes a bigger boom, you can get more in the combustion chamber when the whole charge is compressed rather than just the air...

 

Thats pretty cool.

I just saw the megasquirt on a website last night.

-Jason

 

the pressure of the fuel injection is MUCH higher than any manifold pressure that the blower can create. having the blower compress the air along with the fuel takes up space that the blower could use to stuff more air inside, plus it heats the fuel, causing preignition, and due to the length of time in the chambers allows the fuel to de-atomize somewhat. all in all better performance with port injection. just look at what every single OEM manufacturer uses in their turbo/supercharged vehicles.

 

You can get assembled Megasquirts on ebay. For under $400, I think. I could never solder one of them things togther!

 

Very cool -- slick application of old school looks and modern fuel injected tech. I've been wanting to play with a Megasquirt system for quite some time . . . I was on the old EFI board on Usenet back when they were first kicking around the idea . . . I was going to get an SDS Efi setup but then an engineer friend turned me onto a set of Weber DCOE's . . . so I decided to go that route.

 

There might be some difference between what Zac has done, and what a "port" set-up might net. (blower vs. port injection)

But for the moment; let's see what kind of "numbers" Zac's design will produce.
As a fellow flathead "nut", I'm going to follow his arrangement with great interest! I love "new meets old!"
Knowing Zac's dad; there just might be a SECOND version hiding in the wings!

 

Look at the application--a GMC blown flathead is going to be pretty damn hard to put port injectors onto any way at all! The only remote possibility would have them slanted away from the direction of flow, unless you put them underneath the manifold!

 

isn't that an oxy-moran "efi flathead" like jumbo shrimp

 

I hope you guys didn't get the idea that I was picking apart his setup. in fact just the opposite. I think the way he has it setup looks great, it's a compromise between looks and all out performance. I just wanted to maybe clear up a few things that some people were saying about injection in general.

 

There's a REAL simple answer why the injectors are on top.

That's the only place they can go with that roots blower set up the way it is. He would have to cut that one (I'm sure dad said NO WAY) or build another blower manifold to fit injectors.

That is freakin awesome. I love the way you mounted the carb scoops. Well I guess you can't call em carb scoops anymore, lol.

Zack, check this out if you get a chance. Another EFI flathead build that may give some other ideas. http://www.jalopyjournal.com/forum/showthread.php?t=122396

 

I believe that my questions are more towards tech questions, not any criticism. I could never do what he did, I am severly lacking in the tuning of EFI kits. My questions are only to understand his placement and selection of injectors and carbs. In conventional blower setups the whole charge is compressed and just questioning the why,w,w,..and how, on this set up. He has just replaced the carb with injection so that we can control the delivery of the fuel, cool idea. Excelent application and skills.

 

Zack is 19 years old.Part of me letting him do this was he had to have it done before returning to school.That limited him to what he could do.