DanG

Right you are, nothing better than wasted spark off the stock sensors, my mistake. We'd need to have at least a single cam-sync pulse to be able to do sequential COP control. Wasted spark (with COP or plain EDIS-4 style coils) is probably more than adequate though, so no real need to make it more complicated with an extra cam sensor. (assuming we could build a stock sensor conversion box cheaply)

Chris White

4-1 trigger? I wouldn’t like that for a performance engine, too slow in tracking the rate of change.

Here is so fun math (with round numbers) –
A decent engine can increase revs at lets say 6k rpm / second (from 1k to 7k)
That’s an average speed of 3500rpm or 58 revs per second.
If we assume a linear rate of change that means that the rpms will go up by 102 rpm per revolution.
So if the engine is at 2000 rpm at the start of a revolution it will be at 2102 at the end – a change of 5% (round numbers). If the system is only calculating the position once a revolution then you can have as much as a 5% error in timing, not a real problem for injection but really crappy for spark timing.

Moral of the story – make sure you know how the trigger system actually calculates the crank position, some have the possibility of quite a bit of error and more teeth (up to a point) are better.

Chris White

theedge

Actually they seem to be two different people From what I know anyway. I emailed both and ksp replied, other guy didnt unfortunatly.

It would most likely be quite a cheap solution. More than $12, once you factor in the stuff to program the PIC and all that, but still quite cheap.

theedge

Weve been talking about it on and off in this thread

http://www.msefi.com/viewtopic.php?t...r=asc&start=15

Gist is that the -extra code has a bunch of features over the other stuff, including a second wheel/trigger option.

http://megasquirt.sourceforge.net/extra/

Which should in theory, when combined with the PIC setup for using the stock sensors, give us wasted spark or even Coil on Plug. The cam trigger doesnt have to be a super fancy one from what ive been reading...

Chris White

Only one reason to go full sequential – idle quality with injectors 83lb or larger.
Full sequential sounds neat but it doesn’t really gain you anything at high duty cycles. On a Tec3 you do get the ability to trim cylinders individually (not a big deal)

Chris White

DanG

I think I got some of that 4-1 info wrong...

http://megasquirt.sourceforge.net/ex...tup-wheel.html

I still have to read more on the subject, but it seems like the MS has the ability to take in more than just 4-1 data crank trigger data. What I probably meant to say is that it could RUN on 4-1, but it isn't ideal, as Chris explained. If I was going through the effort of mounting a trigger wheel, it would likely either be 36-1 or 60-2.

DanG

Chris, I was talking about sequential COP, as in firing one Coil-On-Plug at a time. So no wasted sparks. Even that isn't all that necessary.

I'll probably be doing alternating batch injection for fuel, 1 or 2 squirts per revolution (as many as I can get away with on the minimum injector open time for my injectors).

Lots of math and figuring left.

Fen

I'll do some reading. I'm not using MegaSquirt though so it might only e part relevant.



I hadn't thought (nor read) about the benefit of more triggers in relation to changing engine speed which is something I need to take on board. I would say that in the calculation about increasing engine speed it won't increase nearly that fast when the car is in gear, though.

95993RS

I noticed the license plate frame..Guy's Independent Porsche Care...he is my local mechanic in San Luis Obispo, CA where did the car come from?
I used to own an 86' 951 that I sold a few years ago?

DanG

Here's what I dug up on the previous owners from the car's paperwork and receipts...
If you're one of those two guys, or sold it to/bought it from one of them, or know them or the car at all, let me know!

95993RS

I am neither one of those guys. But it is interesting about the license plate frame because that is a very small porsche shop and the town I live in is very small I will try and dig up the old VIN and I will PM it to you.
I think I sold it in '00 if I remember correctly.

DanG

That would be something. BTW, before it was repainted in 2003 or so, it was Zermat Silver.

Chris White

Most folks equate stand alones with the ability to tune the A/F curve accurately – true they will (or should) do that but once you really start highly tuning a turbo set up the ignition timing become critical for power and survivability. Typically the stock set up has at least 3 degrees of timing for a safety margin, as you advance the timing more you will get a smaller and smaller safety margin until you are right on the edge – that will be max performance. At that point accuracy of timing is the difference between running great and large holes in various engine parts!

If you want to run with out a safety margin you better be right on with the timing, much more accuracy is required than the A/F settings!

Chris White

Fen

Sorry it took so long. I haven't had the dizzy cover off again to take a pic of it but it has to come off one more time so I'll try to remember to catch it then.

DanG

Fen, thanks for the photo, definitely post up some more once you have them. I see the black sensor (I think) poking out there, the trigger wheel is between the pulleys and the balance cog, right? Is it just that single black tab at about 2 o'clock on the pulley? 1 toothed wheel?


I'm heading back to PA now. I'm going to go over the whole car with a fine tooth comb. Full wax and polish job. I'm bringing the valve cover and intake manifold back with me to get either polished, powder coated, or just a good clean and paint job.

I'm not sure how I want to do the underhood treatment. Black on black with black and black, black and red, black and yellow, black and blue? Polished bits, NO polished bits? I dunno yet. I'll have to decide once everything is clean. My brakes are currently yellow, but the fronts are "Big Reds" so I might revert back to that. But you see so many Black/red cars out there, so I don't know. Black and blue (and polished aluminum) under the hood can look pretty good, I might try that...


(file photo)

Shipping the block up to 944 Enhancement on Friday. 2.7 liters, here I come!