vbhkj

Did you get the woodruff offset key to advance the cam timing and was it installed for that run? It would be interesting to see how much gain comes from just advancing the timing.

V2Rocket

I have an adjustable cam gear, I can advance or retard the cam 1,2,3, or4 degrees either way by loosening some bolts.

The 2* advance was the only change since my last run, also shown on the most recent Dyno chart. So 2* gained about 4hp and 7 torque. I think I'll try 4*,6* and 8* advance (need to move the belt one tooth and retard back to get 6 or 8) and see where gains start to diminish...

I do have the offset key that I won't need If you want it.

V2Rocket

looking at the most recent chart, i wonder if some power might be left to find by leaning out the fuel at the very top end a little bit?

notice the peak power, then a little dip, then back to peak almost, dip down...coincides with a little dip in the AFR. maybe pulling back to mid-high 12s there might find another 1-2?

odonnell

I bet you could find a little top end power with a COP conversion...the coils aren't competing for dwell and firing time which matters at high RPMs. There are kits (MegaJolt comes to mind) that interface with the ignition alongside the DME and existing setup. There was a guy who installed Ford EDIS on his 924S and was really satisfied. I think it's cheap too, under $500 all in.

http://www.autosportlabs.org/viewtopic.php?t=2026

Long thread but you can skip around. He used a 72-2 spur gear on the cam to trigger the EDIS controller, but a 36-1 on the crank would do the same thing. I have one installed right now and it's seamless, plenty of VR sensors to choose from.

V2Rocket

I thought about trying COP but thought it'd be spendy...I will look into that link.
It's not going to be smog legal but I suppose it's easily enough removed and replaced with a distributor when needed.

I'd like to run the 944 on a complete Ford EDIS system (PCM and ignition box) if I could...if I ever break down (literally) and re-wire the whole car I might just do that while in there.

odonnell

V2Rocket

cool that it runs so smooth.

but someone please do a wire tuck on that car...an tell him to loosen that belt lol

thomasmryan

how does the timing advance with the ford coil pack? map sensor somewhere?

odonnell

The EDIS module reads a trigger wheel via a sensor, much like the speed/position sensors we have over our flywheels. In this case it NEEDS to be 36-1 with the sensor reading 90 degrees BTDC of the missing tooth.

The EDIS module then processes this signal and fires its associated coil packs. For EDIS-4 there are 2 double-sided coils, so it's a wasted spark setup. The EDIS module also sends a PIP (Ford's "profile ignition pickup") square wave signal to the computer. In an OEM setup it's just the car's ECU.

So the main computer is still reading sensors and determines spark advance - and sends a SAW ("spark angle word") signal back to the EDIS module. This is also a square wave that tells the controller how much to advance the spark. If the EDIS module doesn't get a SAW signal, it will run in limp mode, which is 10 degree advance across the board. So theoretically you could just go to the junkyard, get EDIS parts, install a 36-1 wheel, and run the car. It just wouldn't be optimal.

... In the above video, the EDIS module talks to MegaJolt instead of the car's ECU. It looks like a cool product and is under $200. It does its own SAW calculations based off MAP and user-configurable settings. V2 you really need to do this!

V2Rocket

is there any real benefit to be found from just converting to the EDIS?
if the stock ignition coil/driver is working at 6000rpm just fine, if weaker, what would really be gained?
widening plug gaps for "more complete combustion" = power?

odonnell

In 2 crank revolutions, the coil has to fire 4 times. Not only that, but the spark has to jump from the rotor to the cap and then the plug gap.

With EDIS (or wasted spark COP) each coil fires 2 times for every 2 crank revolutions and the only gap to jump is at the plug.

With sequential COP, each coil fires 1 time for every 2 crank revolutions.

The reason it's a performance improvement at high rpm is because the coil has more time to dwell (time to full charge), and discharge (fire). The kernel from the ignition pulse needs more duration at higher RPMs to get the flame front ignited and moving fast enough to complete its power stroke before time runs out. Most importantly it has a lot less time to do all its work so in simple terms it has to work harder and longer. A little math:

6000 rpm = 100 rps = 50 cam rps, which means the stock coil has to charge and discharge 200 times every second. That leaves 5ms for every firing event which is far from ideal. In that 5ms, the coil needs to fully dwell and discharge. The dwell angle of the dizzy is mechanically fixed but the dwell time varies (decreases) with rpm.

And the DME will probably never use all 5ms because that would cook the coil, there is generally spacing between ignition events. So the charge time is cut down and the spark gets weaker as revs increase.



The reason EDIS/COP makes sense is because you have double (or more) time to do everything, allowing for a higher quality spark. You also get better spark timing options. Solid state electronics also have some advantages over a dizzy...no moving parts to wear out, moisture doesn't affect it, etc. and only one gap to jump.

Edit: here's a better worded explanation for the relationship between dwell time and performance.

V2Rocket

I like the solid-state idea and the elimination of the cap/rotor but my question is still...

Does spark "quality" really matter if you're still getting one? I mean, the stock system still works for over 1-bar boost in the 951 side which has more air-resistance than the 944 would.

The timing of the spark is the same, but maybe with the EDIS/COP you can get a higher current spark, but voltage is what makes the spark jump and the voltage is pretty much the same from EDIS/COP versus the standard coil.

V2Rocket

just wanted to upload the cleanest dyno sheet i have...lol

just comparison of where the car is at now vs where it was when 100% stock.
i had another run at over 136whp but there was some pinging so i threw that run out.

soon i will test with +4* cam advance and see what that gets me over this (2* advance).