BMW E30 323 with M20B25 Turbo
The engine
- Inline 6 cylinder BMW M20B25, 2.5 litres, ignition order 153624.
- Wastefire ignition with Ford EDIS wasted spark coils (stock 60-2 trigger wheel)
- Sequential fuel injection with no cam sensor and low-Z 720 cc/min injectors
- Custom engine harness
The turbo system
- PPF turbo manifold (pulse-split)
- External wastegate 50 mm from Boström Turbo Teknik
- 3.5" downpipe and exhaust system out through the (no muffler)
- Dump valve by Simon Marmander
- Custom large intercooler
- Holset HX50 turbo
The config and tables will be updated on this page, and documented properly given some free time. Here they are: [config.txt] and [tables.txt]
Bear in mind that fuel has not been set properly, including afterstart and other enrichments.
Progress
The engine is running well but we have established that the poor fuseholder that was initially used caused 2 injector drivers to break, they can open if I work them manually (mdh..) but give no measureable amount of fuel through the injector if used. This doesn't explain why the IGBTs show inproper diode voltage, they have internal clamping for the back EMF and of the two IGBTs that measure diode voltage - only 00 was used to drive a coil, 06 was never used. The injector FETs that died probably didn't have flyback of the proper voltage at the instant that the injectors they fired were closing, they had to take the back EMF. The 2 FETs and 2 IGBTs are replaced later this winter.
The main problem we have now is tuning the fuel injector characteristics, these are big 720 cc/min injectors and are very fast. How fast is yet to be determined. As the idle only requires about 0.6-0.7 msec opening time it's critical to get this right. I guess experimentation is the only way to figure this one out. I'm starting out with about 100 usec opening time and 150 usec rampup, but it doesn't work too well. Similar injectors have been used on a car that Emil tuned, but the numbers don't seem to match on this engine. I hope that the FETs that died doesn't point to a problem with the health of the FETs affecting opening times. Could that happen?
- When I measure the diode voltage through the IGBTs output to ground I get 740 mV on output 00 and 06. I get nothing when I measure the others. On other boards I can't measure any diode voltage on any output, so if the norm is that no diode voltage can be measured - then something is not normal here.
- do you measure in the same direction ? ( output + ; GND - ?)
- I measured gnd + and output -.
- is it possible that the channel 00 and 06 are configured in the hardware as logic-level outputs? What is the measured output voltage (respect to GND and respect to +12V) after powerup (before trigger applied) ?
- I have never measured the board while powered up. All IGBTs are mounted, I assume that means that no logic-level output is possible.
- do you measure in the same direction ? ( output + ; GND - ?)
- it is _very_ difficult to get them pointing straight.
- we use hotmelt blob spacers that keep the IGBT-s apart until the IGBT-s are clamped. Also, measure connectivity after assembly, just to be safe.
- I did measure them after assembly, it turned out fine (no connectivity).
Some pictures of the car and engine
History
I'm helping a local guy with installing a Genboard on a M20B25 BMW inline 6 cyl engine with Bosch L-jetronic electronics and intake and distributor ignition. The M20B25 originally doesn't come in this configuration (Motronic only) but a previous owner swapped out the block and head of the 323 for 2.5 litre parts and retained the electronics and intake (very stupid, engine ran lean on too small injectors). The stock harness will be cut-up and partly re-used and directly wired to EC connectors - a lesson learned from a previous BMW 728 project with similar electronics, meaning the stock L-jetronic connector and box will not be used.