Megasquirt is a computer system, not an injection system.

As Forced said it is a computer not an injection system so there is no such thing as megasquirt injectors, etc. Still, megasquirt is designed for gas engines, which do not need precise timing on injection events. You just spray a bunch of gas into the intake (or in front of each valve if you want) and you're good to go. A diesel wouldn't run too well that way. ;)

See my other post about Megasquirt... There is no way that it would work for a diesel. Totally different beast. Also, there should not be any vacuum on a diesel's manifold, but if there is boost pressure you would need to know that.

The most realistic way of accomplishing this is to use the normal injectors, but with some kind of electronic valve to control it with a common rail supplying the pressure. This may sound simple, but keep in mind that our injectors need 145 bar, and you have to have timing that is precise to within microseconds (.000001s). Until you find that.... nothing is going to happen.

The second link is not a standalone fuel injection system. It also seems like a snake oil product. The first link costs $7,000 for a ONE CYLINDER engine. It is targeted at research labs trying to research engine designs, etc. Not a road worthy vehicle.

If all the parts do actually exist (injector valves, etc), the fab work isn't all that expensive, and somebody designs an open source (or cheap) common rail controller you'd be looking at $3k easy. It *would* be great for lots of tuning and performance mods, but you'll still have an engine that gets crappy fuel mileage relative to modern direct injection diesels.

I don't mean to rain on your parade, but the cost makes it very hard to justify. IMO, the best way to have a computer controlled IDI diesel is to use the injection pump off of an OM606 (won't work on OM616 or OM617 diesels though). It has an electronic fuel rack... that way you can control the amount of fuel, without having to worry about all the injection timing events, and gobs of custom fabrication. :cool:

I think so. The problem with converting to DI is there is a different piston and head design. After replacing those it might very well have been cheaper to put in a used DI engine! :(

another obstacle is compression ratio on these cars. DI ratio's are around 14:1, where our IDI CR is around 22:1. so is this plan to just computerize the existing IDI injectors, or to upgrade to DI injection? cause I don't see computerizing IDI as much of an improvement. and I don't see DI working at 22:1 CR... so you are talking about not just redesigning the injectors, you are talking about redesigning the piston and head dome... um. not really possible, but if you think STOCK 616/617 pistons are pricey... try one off pistons...

Well, this is good information.

Not what I was hoping to hear but good information.

I am interested in Gurkha weighing in with the Indian connection to advances relative to the 616 617.

Tom W

On the Mercedes side of things...

The OM 602.98x was Mercedes' direct injection version of the OM602.9x. Introduced in the 1996 E290, Sprinter and Unimog it used a rotary injection pump and an intercooler. Power was mostly the same.

Compression ratio has nothing to do with DI vs. IDI. Nothing. VW TDI motors are direct injection and they operate at 17.5 to 1. The C220 CDI operates at 18:1.

The reason for the slightly lower compression ratio is the increased turbo boost. The newer engines run much higher boost, hence the reason for slightly lower CR. For the same reason, a normally aspirated diesel motor will have a CR that is higher still.

Looks like a less complicated swap. Good luck trying to get one in this country, you would have to import it.

hmm, so power was unchanged in this powerplant, was efficiency improved?
if the CR is different only for added turbo boost, then it's the boost that gives the additional power, not the DI/IDI thing... so... if we put a thicker head gasket on our 617's added a bigger turbo for more boost, and enriched the fuel... would we get a big boost in power without the danger of high EGT? ... HMMMMM

No, you would have lower power and reduced efficiency because of the reduced squish area between the head and piston. If you want to lower the compression ratio you would have to machine out the bowl of the piston.

Converting to direct injection would involve a new head and pistons at a minimum.

However, convering the existing indirect system to common rail injection seems a lot less involved. Need feed pump, sensors, switchable injectors, computer controller and common rail (manifold).

Is this more what you had in mind Tom?


Also, any possibility the existing IP could be used as a feed pump -- disconnect throttle & ALDA and wedge in WOT? That would make playing around with the idea a lot less involved and potentially easily reversible, provided you din't blow up the engine :)

What would be the advantage to converting to common rail?

Want more power? Turn up the pump and/or install larger plungers.
Want better atomization? Shim the injectors to a higher pop pressure (Like mine).
Want a different spray pattern? Install different nozzles (Like mine).
Want multiple injections (pre-spray) from the injectors? Use 2-stage injectors (Like mine).

There wouldn't be any advantage to building a common-rail system to fit an old inefficient engine like the 617. In the end, it would still be far cheaper to buy a wrecked sprinter and transplant the drivetrain.

Yes, I was thinking of using the existing heads and pistons and just contolling the injection process better. I am not kowledgable about the idi di question.

Tom W

My neighbor's buddies planed the head down on one of their gas engines to increase the compresson ratio. They got it up to around 11 to 1 (and no, they can't run normal gas in it anymore).

I'd think piston head changes and changing the distance between the head and block would be equivalant compressionwise. I find these littel nuances facinating, so if you have any pointers to further reading I can do to educate myself on why not, I'd really appreciate it.