My projectcar is a 205 GTI with a 1.9 litre 8 valve engine. I turbocharged it some time ago and am now fully rebuilding/upgrading the engine to suit high boost. Have a look at my project webpage

specs in a nutshell:

alloy 1905 CC wetliner engine

16 valve cyl head

Mitsu td05 16g turbo

Boost control

Hi I've obtained an audi N75 valve and want to use it for boost control

Q The primary question I have is: Can I use a extrafet/specfet for this or should I use a injector output for this?

A Spec/extra fet can be used but since you are switching inductive loads fitting an flyback diode is required can be mounted either inside case or external across valve wires (diode pointing towards +vbat connection).

The Boost control solenoid seems to be working now. Will try to tune it one of these days.

OLD / solved issues for reference by other users perhaps experiencing simmilar problems

Engine running problems.

I have some problems with my engine. every once in a while it suddenly cuts fuel while cruising on the gighway. This lasts for about a few seconds and then it resumes again. What i can find in the logs is that:

Most likely TPS goes under iac_tps_threshold. If RPM > overrun_fuelcut than fuel will be cut. If this is the case, set tps_low, tps_high, iac_tps_threshold, overrun_fuelcut and overrun_fuelresume reasonably.

Also check fuelcut_min_kpa.

Note that these are very easy to tell if mcd dump and log is provided, and very hard to tell for sure without these.

Thanks. Problem solved. It was a bit of a dual problem. one the tps threshold for idle was to high AND there seems to be a bit of a problem in the fuel cut implementation. The fuel cut rev is devided by about 1.6 some way. Will look further into this.

Tachometer output

I wired the tachometer to EC-18 pin 12 (SPECFET 0) and set the folowing parameters in megatune:

Tachometer channel: SPECFET

Tachometer channel: 0

Tachometer divider: 0

in the help it says:

Most GenBoard outputs is only pulling the output low (0 volts)

If your tachometer wants 12V or 5V signals, wire up a (say, 1kOhm to +12V or +5V) external pullup resistor. Configure Tachometer Divider if you want a lower frequency to your tachometer.

Check out the latest MegaTune release package (mt-r27), it has 1.0.19 firmware which has the tach output working.

> Ok, I have the mt-r27 formware working now, but still no tach output. The strange thing is: I would expect a led to work here. I wired a lef parallel with the pullup resitor but it didn't do anything. Is my logic flawed?

Probably I so not really know how my tachomater works. It used to be connected to the coil (-). But I use a different coil now. (wasted spark) perhaps I'd just hook it up the old fashioned way with diodes?


I added 4 injectors to my engine. So I now have 4 injectors aiming at the valves and 4 upstream. The secondary injectors are 305 cc and the primary injectors 240 cc.


I configured VEMS to do injector staging.

Changed the firmware so the secondaries can be larger than the primaries.

I changed the VE table so all values above 130 kpa are devided by 2.

It works. Not quite how I had expected but after a bit of fiddling with the inj_stage2_rate it works.


Megatune showed wrong voltage:

Ignition problems. Fuel worked but no sprak.

Thanks for the feedback! It turned out to be the secondary trigger indeed.

Took it for a drive this day. But the engine ran verry lean (afr 1:16) and it appeared all the tables are ampty somehow in megatune. I had this problem with a more recent firware before. Ans switched to a bit older one that seemed to work fine. But now the tables are empty again. Does anybode have any idea how this could be fixed?

A: There was a ini update on the magatune page.

<<This package has bug in ini file causing settings lost when updating to ECU, here is [fixed ini file]>>

The engine didn't start -> no fuel injection.

the pulse width megatune displays is 0 though the crancking pulsewidth is set. And the the req_fuel is set(and all tables are filled with the right values)

A: somehow the decel fuel cut rpm was set to 0 rpm after a firmware update. I set is back to 2500 rpm and it started again.