a bit confused

[tim_s]

tried running my car (MS fuel and sparks, no AFM etc) with motronic doing the timing (leaving MS to do the fuel still) today and it ran great, better than my MS map. Now this confused the hell out of me. Mainly I have no idea why the motronic timing isn't all over the place with no AFM connected. I thought the map might be TPS vs RPM rather than load (from AFM) vs RPM, but even with the TPS disconnected, although it advanced the timing on idle a bit (the motronic probably didn't understand that it was an idle condition), it seemed driveable otherwise.
Can anyone shed any light on the workings of motronic timing, and why its still working well without an AFM connected? that wasn't really expected!
Even better, does anyone have a timing map for the M42? Beginning to realise that my MS timing map is a bit flawed, and that the original map would be a great place to start!
Any musings?
Cheers
tim

[sheepdog]

It is probably locked in a safe timing possition (no advance). They are supposed to do that when they do not get all of the information the computer needs (a.k.a. limp mode). It also explains the idle being off but fine otherwise.

If you can find out what it defaults to in this mode, it would give you a place to start. A timing light would give you this info. Just add a bit of retard below say 1500, maybe a bit more above 4500.

[tim_s]

yeah I'd thought the same, but after driving it i'd be so surprised if the timing was just 2D and rpm based, as it feels far too good. I have a map that i've put some time into for the MS and have tried a few MS spark maps based on other 16v 4 pot motors, and nothing feels anywhere near as good as the motronic! The MS maps were all 12x12 3D and added timing as the manifold pressure dropped. If the motronic was 2D, the MS should have felt much better. The sparks actually feel really good, performance-wise its quicker on full load than my MS map, and driving around it just feels much smoother. Certainly not like an e36 in limp mode where the idle goes to crap, performance feels crap, fuel economy goes nuts and the timing feels retarded.
The idle only felt off when I disconnected the TPS, i believe this is because the motronic has an idle routine, and this was not engaged when the TPS was disconnected, as the motronic couldn't tell it would be an idle condition with no indication that there's no throttle.
I vaguely remember trying running with no AFM with MS controlling fuel on the rollers last time I was there, and do recall that we got the same max power figure.... hmmm.
I've not driven the car too far yet, will be doing 300 odd miles tomorrow, all motorway, and should be able to tell how good the timing map really is then.

Unfortunately my timing light will probably help very little. I will have a go later today, but without a rolling road (and info under load), I think i'll get minimal info, as I'm pretty certain its not a 2D map - i may be wrong though! It will be on the rollers soon enough, and i'll get an accurate timing map made then.

[Euro Nation]

DME 175 has seperate closed throttle, middle throttle and WOT maps, and a couple of each at that. The closed and WOT map are 2D so all you need is RPM. Middle is a 3D map with load.

I don't have a shot of the M42 timing map on hand to post. Post up a screenshot of you MS timing map and we'll see what we can do.

[Ramblin MAn]

by MS do you mean Mega Squirt?

[tim_s]

yup. forgot about this thread! have got the MS timing map working much better now, I'm not sure about the motronic map, i had a few cruising problems on the motorway when using it, will have to try it again sometime as the fuel map has changed quite a bit since then...
euronation, cheers for the offer, when i get some time i'll post up my MS timing map if you'd like to comment!