vems trigger problems on aan

[Jamo]

You can only be confident if you listen for knock dude.

Other people's spark/VE tables can not be trusted, since every engine setup behaves differently.
E.g. I have 20-21 degrees of advance in my setup at those ranges and boost profiles, however run a different turbo, exhaust, cam timing, cyl. head flow, probably different fuel, etc, etc..

Please use a knock detection solution like the cheap headphones Terrybullwon and myself are using, or an electronic solution as Marc Swanson is selling. This is the only way to be on the safe side when mapping your own car.

You forgot me i have the same headphone setup

A80avant is running the electronic solution, I'd like to know more about that one as well to be honest, Marc?

[A80Avant]

on Marc's website it has instructions to make one. Its quite easy to use and i have the cables in the car now(but not connected).

[dkw_dude]

on Marc's website it has instructions to make one. Its quite easy to use and i have the cables in the car now(but not connected).

I made a set of knock sensor to laptop mic input cables my self based on the instructions on the EfiExpress webpage, hopefully it works well. I run a quite safe ignition map, so I haven't heard any pinging sounds yet just the normal engine sounds as in the soundfile on the web page.

[Bram]

Any pictures of your headphone setup. Where did you get it. Yea I fully understand each person spark table is different, but it would be interesting to see spark advance at part load sites compared to full load.

Did about 60 miles tonight of normal driving with wife in car etc. I still get some rare trigger errors always between 2k and 2.2k rpm. When it happens the car lurches badly and the exhaust actually bangs the underside of the car. Sounds bad. it can happen even on the overrun.

I must get the scope out this weekend. Driving it is just too much fun. Lol cheers des.

Buy a cheap headphone for construction site working. Drill a hole in one of the headphones. Plug a plastic tube in to it as far as it can reach your ear. Then route the plastic tube through the S2 firewall into the engine bay and all the way up to sit between the 2 knock sensors against the engine block. Done

You can hear knock quite easy. It's like you hear coins drop in to a metal basket ( I will use that metaphor for further explanation). Depending on the amount of coins you hear if you have mild knock (when you hear occasionally some coins drop in the basket) or heavy knock (a continues rain of coins).

It really works well

[diesel des]

Ok sounds simple. Do I need to fix the pipe to the block with a pipe fitting eg bango bolt. Cheers

[Bram]

Ok sounds simple. Do I need to fix the pipe to the block with a pipe fitting eg bango bolt. Cheers

Some tie-wraps should do the trick. Just try to fiddle the tube in between the IM runners so that the opening of the tube hits the block

[diesel des]

more scope "fun"

Right, i had the scope input on the cam sensor connected incorrectly in my first pictures. Instead of ground i was connected to vcc 5 volt, hence the output looking like it was inverted. Here is the new picture. Both the crank pin and cam are on the same scale eg 1 volt/div. So the cam output drops from about 4.8v to 0.3v. The crank pin is AC and is about 6 volt peak to peak. As rpms rise this voltage increases slightly.



So what is the minimum voltage vems needs to operate correctly on this input? Has anyone got a circuit diagram of vems on this input? I dont want to have to reverse engineer vems if there is a input spec someplace?

I get this trigger fault whenever cold and also at 2200 rpm almost exactly. My wife is calling the car "the frog" as it bounces vioently during this trigger fault. Its actually shook something loose on the exhaust as it rattles on the *** of the car now. Yet another job...

[diesel des]

Looking at pauls scope picture of the ABY the crank pin is like 30 volts!
http://www.s2forum.com/forum/attachm...9&d=1276876987

My 6 volts looks the issue. I need to acurately measure the crank pin to sensor distance. This distance should influence the output from the sensor. I will put blu-tac on the sensor and spin the crank and measure whats left.

Even when i get the trigger faults in vems the scope voltage looks the same. So i must be just on the edge in terms of input voltage.

Here is my timing table. Its far from finished, but thats what im running. The numbers here are then modified by the table for inlet temp which retards the main table about 3-4 deg on average. Again its more retarded than my motronic map so its safe. Your thoughts please..

[diesel des]

More updates. I put some blue tac on the crank sensor and moved the crank so the pin was in the window. The depth of blue tac was about 1.7 mm so I "adjusted" the bracket with a grinder by just over 1mm. Now the sensor gap is about 0.5mm. The trigger error seems to have gone but I will test when car is cold as that's when its worse. On the scope the voltage has went from 6 to almost 14!

Lookin good. Will keep you update. Cheers.

[A80Avant]

yup. you should be ok now.
in our case a wrong measurement ended up in a sensor crack, but readjusted later it was ok.