MadScientistMatt wrote:
Larger injectors could get you pretty close on the steady state fueling. But there are several other things you would also need to tweak.
- Startup fueling. Methanol doesn't evaporate as well as gasoline on a cold engine, requiring more fuel on startup and while the engine is cold.
- Acceleration enrichment. Same effect here; you'll need proportionally more fuel to compensate for the extra fuel puddling.
- Spark timing. It's totally different due to different burn rates.
I think you've explained things to me in a simple way for me to see how to proceed..
Cold start, I can deal with one of three ways.. The early system used a extra injector for cold start. I can either switch that injector to gas or use a later system that just extended the time of firing the injectors during start up. Luckily we don't race in the 20-40 below weather we have to start our daily drivers.. Or the third way goes all the way back to my sprint car days.. Get an oil squirt can filled with gas. Drill a hole in each runner and squirt a couple of squirts of gas in each prior to start up. Put a piece of aluminum foil duct tape over the holes after start up..
During acceleration I can use the wide band of tolerance engines running on alcohol have, as an assist. Run it overly rich normally and assume puddling will be minimal since on the V12 the injector is right over the intake valve
As for timing well I'm back in my comfort area with a distributor and My Sun distributor machine..
Paul_VR6 wrote:
I am willing to slap you around but only for money. 
Only if you wear fishnets and a leather corset 
I can't fathom how anyone can be less qualified to build a megasquirt than I was, but I got one running just fine. It's not that hard.
I am not cheap, but easily bought.
I agree that accel is probably enough if you are already on the fat side after the injector change.
In reply to Paul_VR6 :
Reading this over again I'm reasonably confident that I could make my mega squirt work. The problem so many had is the system doesn't usually use digital sensors, since it was originally analog. ( Think early VW Rabbit) the last iteration did go over to digital but those are much less common in the scrap yards.
The crank position sensor is in the distributor. It uses a Hall effect magnetic sender. I can adapt the whole throttle assembly from the GM Atlas engine. Thus getting both the digital sensor and a bigger throttle bore.
My only unsolved issue is how do I deal with input from two sensors rather than just one? (The V12 uses dual intakes, one on each side, rather than the single one in front a V8 uses).
That makes plumbing for twin turbo's extremely easy and a short direct shot. But mandates the use of alcohol to cool the inlet charge if more than 6 psi will be used.
I dont have much to add other than tuning EFI looks more daunting than it actually is. Also, I recommend a book on whatever you choose to go with (MS in this case)
The one i used helped me set up a base tune and walked me through the process of datalogging and adjusting the base tune. Having the book there to tell you where to look was super helpful for me.
I found it relatively easy to pick up and I got my car running plenty well for DD and WOT use.
TPS isn't normally used for load, just decel and acceleration enrichments. Just use one of the TPS and make sure the two throttles are reasonably synced up.
In reply to Paul_VR6 :
Thank you Paul. Logic tells me You are absolutely right and I have to stop obsessing about unconnected sensors etc.
When I hook up the wide band O2 sensor does it work the same way for both sides of the V ? Or is there provisions to read each side in a Mega Squirt?
In reply to frenchyd :
If possible, put the sensor where the exhaust merges into one. It is heated, so it doesn't hurt too much to move it further downstream.
Otherwise, it is possible to modify MS2 to read and modify the fueling per bank:
https://www.diyautotune.com/support/tech/other/common-megasquirt-modifications/
In general on engines with "banks" with separate exhausts I use one O2 per bank. I even do that on my inline/vee six cylinder, one for each bank of three cylinders. If the exhaust merges into one, you can get away with a single sensor.
In reply to Paul_VR6 :
Since Jaguar has 3 cylinders per exhaust manifold for a total of 4 should I use 4 O2 sensors? Or is just 2 sufficient??
As long as it merges into two pipes (one per inline 6) two is fine
