Tuning issues. Time to Megasquirt

[Pierre]

My 76 530i with a 3.3 L-jet has a very strong motor. This things has so much torque, it feels almost as strong as my E36 M3... but there are problems.
1. It pings under load from 3500 on up. If I retard the timing, I lose power. In fact, I want to advance a little more but the pinging gets more pronounced. So I compromise. Under most street condition, it's OK, but when I drive hard under sustained condition as in a twisty road, the car runs hots due to the excessive pinging. I will end up damaging the engine if I keep at it.
2. Fuel economy is terrible. If I advance the timing, it improves but the pinging is excessive again. I get 15-16 MPG using premium fuel. I want to drive the car more, but fuel is not cheap.

Megasquirt seems like a plausible solution. I do know that that the gain in fuel economy may take years to recoup but I am intrigued with the idea, and would like to stop the pinging problem I am having. And if I am able to eliminate the AFM, I may gain even more power.

I did some searching, and some reading. I know a bit about the recommended course of action on a carbureted M10 in a 2002. But the L-Jet M30? What injection do I use? Suggestions? Recommendation? Advice? And some direction about specifics would be appreciated. (MS2 or MS3?)

Thanks.

[Falkenberg]

I suppose you can keep most of the L-jet components, but you might get rid of the AFM and cold-start stuff. Megasquirt uses a MAP and also a throttle position potentiometer which you will have to get from somewhere.
M30 motronic with auto gearbox have such a potentiometer, and also E34 cars with M50 engine should have something like that.

Engine speed you can get from the L-jet distribuitot, I suppose. If that is not sufficient, you might use a motronic hall flywheel setup on the front of the crank shaft.

You should be able even to add knock sensors and closed-loop lambda control to it as well, once you have a basic system running.

[themilkguy]

Do you find the pinging goes away (or at least becomes less noticeable) if you use a higher grade of gasoline?

[Blaise]

My 76 530i with a 3.3 L-jet has a very strong motor. This things has so much torque, it feels almost as strong as my E36 M3... but there are problems.
1. It pings under load from 3500 on up. If I retard the timing, I lose power. In fact, I want to advance a little more but the pinging gets more pronounced. So I compromise. Under most street condition, it's OK, but when I drive hard under sustained condition as in a twisty road, the car runs hots due to the excessive pinging. I will end up damaging the engine if I keep at it.
2. Fuel economy is terrible. If I advance the timing, it improves but the pinging is excessive again. I get 15-16 MPG using premium fuel. I want to drive the car more, but fuel is not cheap.

Megasquirt seems like a plausible solution. I do know that that the gain in fuel economy may take years to recoup but I am intrigued with the idea, and would like to stop the pinging problem I am having. And if I am able to eliminate the AFM, I may gain even more power.

I did some searching, and some reading. I know a bit about the recommended course of action on a carbureted M10 in a 2002. But the L-Jet M30? What injection do I use? Suggestions? Recommendation? Advice? And some direction about specifics would be appreciated. (MS2 or MS3?)

Thanks.

Good luck

[Pierre]

Do you find the pinging goes away (or at least becomes less noticeable) if you use a higher grade of gasoline?

I use the highest grade I can find. I am not sure of the compression but I am running a 3.2 from a later E23. (210 psi average reading on compression tester.) I could use an octane booster or go get race gas but that gets too inconvenient and expensive. I think I should be able to extract more efficient power out of the engine as is. I just need the ability to manage the spark timing better and maybe even run a knock sensor.

[Mike W.]

You know, somethings wrong if you are running stock 3.3 pistons, even the later motronic ones are only 8.8:1 compression so you shouldn't have problems. Euro's were 10:1 and people manage with them, my Bav had 9:1 and was a little touchy, but not too bad.

[Pierre]

I do not know the compression on this engine. I bought it this way. The key word is "manage." I manage but there is a lot of room for improvement. And I can't improve with a distributor and the stock L-Jet. It's restricted by design, due to the technology of the time. Megasquirt opens up the possibilities of adjustability and flexibility.