Newbie from New Brunswick, Canada

[Coyote Jack]

As the title says, I am a for real newbie. I have never had any type of fuel injection other than factory stuff on my truck.

My current car is a 1972 Dodge Demon 340/727 auto. I am running a 6-71 GM roots blower with 2 600 Holley carbs. My ignition is a MSD 6AL with a MSD distributer. Although the engine has never been on a dyno the estimated peak HP is about 650 hp and I would like to keep that or close to it. I want to explore the possibility of going to efi and doing it as cheaply as possible. I have read about Megasquirt before and found it interesting and a lot cheaper than the aftermarket stuff that is off the shelf. I don't want to reinvent the wheel and this looked like a good place to start getting information. If anybody has a similar setup, I am all ears. At present I guess I am looking at fuel delivery only, but if timing control can be achieved without changing my ignition then I would look at that as well. I hope that is enough info to start with.

Coyote Jack

[Matt Cramer]

Sounds like a cool build, got any pictures? I'm working on a '66 Dart myself.

For fuel, you could either rework the manifold for port injection, or use TBI-type setups above the blower. A pair of the old Pro-Jection TBIs might be a good choice - or I've seen blower injector plates that could work too.

Taking over the timing is pretty straightforward. You just lock out the advance mechanism and wire the distributor to the ECU. More details here:

https://www.diyautotune.com/support/tec ... tributors/

[Coyote Jack]

Hey Matt,
I have kind of been thinking that either a dual throttle body system or an injector plate is the way to go. I have to get the fuel charge in before the blower to cool the rotors. I am wondering if there is a throttle body I can use off of a production car that could fit the bill. That would help keep the costs down. I am not overly worried about the timing right now but I would probably be looking at a Megasquirt 1 version 3.0 so I could make some timing changes in the future.
Lets see if I can get a pic or two up here for you.

Jack

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[Six_Shooter]

If you can find them, a pair of GM 454 throttle bodies would likely be enough. IIRC they are around 600 CFM in stock form. A friend who has made his own 4bbl throttle body, one half being a 454 throttle body then bored it out an addition 1/8" IIRC. So you could do the same to a pair of those TBs and have plenty of flow.

I'd go MS2 at minimum, especially if you're thinking of production throttle bodies that have built in stepper motor IAC valves. The MS2 will control them, the MS1 will not (at least not easily, I don't recall if there was a mod for MS1 stepper motor IAC or not).

[Coyote Jack]

Hey Six_Shooter,

Thanks! That is some good info. When you say GM 454 TB's I am assuming you mean off of a chevy 454 engine.

Jack

[Coyote Jack]

Hey Matt, do you have any pics of your 66 Dart? Always like to see what others are doing.

Jack

[Six_Shooter]

Hey Six_Shooter,

Thanks! That is some good info. When you say GM 454 TB's I am assuming you mean off of a chevy 454 engine.

Jack

Yes, that is what I am saying, throttle bodies that were originally on 454 engines. They are a bit hard to come by though.

[Matt Cramer]

Hey Matt, do you have any pics of your 66 Dart? Always like to see what others are doing.

Jack

Work in progress picture taken today:

dart-engine.jpg

[Coyote Jack]

Looks like that leaning tower of power is going to surprise the odd person when you stand on it. Do you have a completion date in mind?

Jack

[R100RT]

"A completion date" - jee Matt, I was just thinking the same thing
You spend too much time helping everyone else at the expense of your projects. Been hoping to see this one running for a while now.

[Matt Cramer]

Looks like that leaning tower of power is going to surprise the odd person when you stand on it. Do you have a completion date in mind?

Jack

I've given up on setting an actual deadline and set a goal to get in 4-5 hours of work on it a week, and make it ready whenever that makes it ready. Since I made that decision about a month ago, I have been making some semblance of progress on it.

[Coyote Jack]

That works real well. That is how I did it when I built my car 10 years ago. It sure made the whole process a lot more enjoyable. When I built the blower engine it was a completely different story. I was trying to get it done before a major car show here. It was a real hair puller. Problem after problem and not having much in the line of tech support sure made it touch and go. I finished it the night before we had to leave to go to the show. That was the shakedown run and the wife was not real happy about the whole ordeal. Can't say as I blame her.

I have come up with a bit of a plan for getting the efi on my engine. Here is my parts list so far.

1. Walbro GSL 392 fuel pump
2. Two GM 454 TBI units (I think they have 80lb injectors)
3. Variable fuel pressure regulator
4. MS2 Kit and related harness and stim
5. Boost gauge ( I have)
6. Wideband O2 sensor (I have)
7. Adapter plates for TBI units

What else might I need or is there something I should change?

Jack

[Matt Cramer]

The TBI units have built in fuel pressure regulators, and I think it's possible to shim them for more pressure. But four 80 lb/hr injectors would only be good for about 320 hp at the crank without a fuel pressure boost, and even then there's only so much to gain.

Perhaps it should use three TBIs, or a plate under the throttle body set up for eight injectors.

[Six_Shooter]

The TBI units have built in fuel pressure regulators, and I think it's possible to shim them for more pressure. But four 80 lb/hr injectors would only be good for about 320 hp at the crank without a fuel pressure boost, and even then there's only so much to gain.

Perhaps it should use three TBIs, or a plate under the throttle body set up for eight injectors.

Not true. There have been many people use just 2 TBI injectors (single TB) and have made proven HP greater than 320 HP. So doubling the number of injectors will greatly increase the power potential.

Going to an external regulator is a great way to get better atomization from the TBI injectors.

Those injectors can also be made to be adjustable, so they can be opened up to around 95 lbs/hr IIRC at max flow rate at 12 PSIG fuel pressure.

[Matt Cramer]

Looks like I made a bit of a goof in my math somewhere - I re-ran the numbers it looks like for four 80 lb/hr injectors, the max hp may top out at more like 420 hp, and close to 500 hp if they're bumped up to 95 lb/hr with more pressure. That is for forced induction; a naturally aspirated motor can go a bit higher as it needs less fuel for cooling.

[Coyote Jack]

I guess I am going to have to do a lot more thinking on this. I would like to keep my 650 hp at the crank. If I go with a plate and 8 injectors I would think that batch firing 4 would work fine for idle and cruise but all 8 would be needed at WOT. This would also mean a change to a BugCatcher style hat instead of the Hilborn I have now. More thinking needed.

Jack

[Coyote Jack]

I have been doing some more investigating and number crunching. It appears that 2 Chevy 454 TBI's will do the job as they can be modified to support 500 hp each fairly easily and as much as 600 hp each if you really want to work on them. So I would be looking at $500 for the throttle bodies, injectors $400 and $500 for a MS2 for a total of $1400 plus some smaller parts to mount the TBI's to my blower. This does not include any of the other parts I am going to need for whatever setup I choose. If I go the injector plate route it appears I would be in the $1900 range. The other route I am looking at is the FiTech 2x4 setup for 625hp, it is $1795. So looking at all of this I have to decide if going the Megasquirt route is worth the extra hassle compared to the FiTech stuff which is basically plug and play. The Injector plate has the best cool factor as far as I'm concerned but trying to get a good idle and off idle response could be a problem. The chevy TBI's appears to be the cheapest but also the hardest to get working properly. A lot more thought and research has to go into this before I buy anything.

Jack

[Six_Shooter]

Why are you spending $400 on injectors when the 454 TBs should come with them, especially at $250 each?

[Coyote Jack]

One of the things you have to do to make the chevy throttle bodies work in a blower application with the hp I have is to replace the injectors with ones that flow more fuel. The reason for this is you don't want to run the injectors at 100% so you need injectors in the 110 lb range and they are not cheap.

Jack

[Six_Shooter]

One of the things you have to do to make the chevy throttle bodies work in a blower application with the hp I have is to replace the injectors with ones that flow more fuel. The reason for this is you don't want to run the injectors at 100% so you need injectors in the 110 lb range and they are not cheap.

Jack

Look up how to make the TBI injector adjustable. ;) It's a free modification.