Hello everybody!
I am new in DTA. Short intro: My name is Toni from Köln (or Cologne), Germany. I build a S40 Pro in my US '77 VW T2 and made the flywheel a 24 - 1 incriment flywheel. The DTA shall work as a substitude for the original controler. Now i am having a problem with the ignition. With the sparking plugs mounted off i get a RPM of around 230 - even if I jumpstart it. I am not sure if this is a normal cranking RPM. But with the sparking plugs mounted it even drops further to probably just below 200. I am not sure because the map shows 0. even if i just put in one sparking plug. The flywheel spins a little slower and no more output of rpm. It looks like the sensor or the ECU can't sense rpm's below 200. Or is this a configuration problem? And because the rpm shows zero there is no ignition. No ignition - no running engine - problem...
I know there are a lot of you having DTA's installed in older cars? Anybody had the same or similar problems? Thanks for any support!
Greetings from Köln
Toni
@Steve
I already dealed with that problem. When cranking the voltage of the Ecu drops to around 11V, wich is okay I think. Nevertheless I tried two thinks to even be sure that this is definetly not the problem. I jumpstarted the bus with another car and had over 13V all the time. And I hooked another batterie at the Ecu so it has is very own power supply. I will still try to do scope trace.
@Drew
so you see rpm in the dta software with the plugs out, but not with the plugs in?
That is excactly the problem. I thought it might be a lower than 200 rpm that is not shown by the DTA software. But I tried it only with cylinder 1 plug in or out and the wiring for the sensor runs nearby the cylnder 1. I will try to just put the plug fpr cylinder 4 in and see what happens then. Maybe it is interference... I will gibe it a try.
mine cranks at 150 when cold, just over 200 hot, so its not that it cant be seen by the software. mine also drops into 10v range on crank.
as steve said the S series has a crank scope feature, might be worth running that with no plugs then all plugs to see if it can see the crank sensor properly.
Scope trace would tell a lot. A 2 wire VR sensor generates it's own voltage, so if for example the air gap was too large, the the voltage generated would be much smaller and the ecu may not see this until a higher rpm.
So something like that may be a potential issue. The height of the yellow trace indicates voltage seen
Either way, 200rpm is plenty fast to start an engine. I think mine cranks around 180rpm or so most of the time.
Hi everybody,
today I found the time to go to my garage and do a scope while cranking. The scope without plugs still looks good to me. But it looks quite strange with the plugs in and especially with only one or two plugs in. So it really looks like an interference problem to me... what do you think? Thanks a lot!
Don't get hung up on cranking rpm, remember that the ecu does not use the ignition map until the 'transition from cranking' speed is exceeded. Up to this point it just relies on firing tooth on start up.
