Building a BMW M10 racecar engine
Engine specifications
- 4-cylinder 2 valves/cylinder engine.
- 2058 cc normally aspirated.
- Rebuilt head with optimized intake and exhaust ports.
- Special cast intake manifold.
- TWM 45 mm throttlebodies.
- 304 Dr. Schrick camshaft.
- BMW S14 rods and custom made JE pistons.
Total newbie on VEMS, but gets lots and lots of help from Johan Rius (Thanks a lot!!)
Questions to Rikard
As we spoke earlier you were thinking of going with a distributorless setup, is it using:
- the missing tooth trigger wheel and wasted spark coils
- using a cam sync sensor and separate coils for direct fire ?
In either case you can still use the missing tooth wheel as the crank sensor (primary trigger) for a more accurate engine speed.
If you're going for a direct-fire setup, the easier trigger arrangement would be cutting of all but two teeth from the 36-1 wheel you have and use the Honeywell GT1 Hall sensor. These two teeth should pass the sensor about 60 degrees before TDC, i.e. place the sensor and then determine what teeth to keep.
A: I´m think about running Wasted spark since it seems easier (dont need a camtrigger etc) and I also dont see a gain in hp by running direct fire. By easier I mean less machining of parts since I cant do this by myself.
Q: Thinking about using the Honeywell GT1 Hall-sensor, but my toothweel has a smaller "tooth spacing" and "target thickness" than the GT1-sensor needs according to its specifications. Is it possible to use it anyway since I´m not even close to the 100kHz its supposed to handle? 8000 rpm is less then 5kHz with 36 teeth triggerwheel..
A: I guess you would have to try. With a multi tooth setup it's easy to watch the count of the wheel errors to determine if you have trigger sensor (or signal) problems. I know it's not very polite to rev the engine up to 8000 rpm in neutral as there is no load on the engine but it's the fastest way to find out if there is trouble. Any errors and it should appear in the wheel error count on page 2 of the LCD display as a kind of rev limiter as ignition (and fuel? don't remember) is cut when the Genboard looses track of the wheel tooth count. Here is good reading for finding any trouble: InputTrigger/TriggerLog
Specifications:
Thoughts about VR-trigger
I also have a VR-sensor that I first intended to use. It was installed in another car that was to be a VEMS-testcar, but it became a daily driver instead.. Im a bit scared of using a VR-sensor since they seem so much more sensitive to other things around them, but maybe Im a bit too scared..? The Hall-sensor seemed lika a god idea since it seems more foolproof..
The VR sensor works very well, you should not be afraid. Just connect all GND and GND5 from the same (strong - thus electrically close to the battery) point outside the ECM case. Also, don't connect the GND and GND5 inside the case. GND and GND5 used to be temporarily connected on non-preassembled genboards with a small arch at the middle on [this pic] right from the FETdrivers. This onboard GND and GND5 connection arch was for safety in case user forgets to connect GND5-s: some people forgot to cut the arch. Now the necessity of strong GND and GND5 connection is stressed instead (which was necessary for good operation anyway).
![[this pic]](http://www.vems.hu/files/genboardv3/CaseAndMounting/GenBoard_v3.x_clamping_Alubos_insulator.jpg){kind=link}
Actually, if you connect the VR sensor in reverse, it's revealed in 15mins by applying InputTrigger/TriggerLog at cranking. A badly connected HALL sensor can easily be damaged.
Also, there is now the '''advanced multitooth filter, see toothrel_normal and related variables (see GenBoard/UnderDevelopment/FirmwareChanges) that reveals any multitooth problem early (makes it easy to decide if problem is with trigger or other subsystem)
The sensor is taken from a BMW E36 with a six-cylinder engine (M50 I think. Anybody´s using this sensor?) and the triggerwheel is the same as Samuel Lindqvist is using on his M3E30 and it works fine. Looks like this:
