MicroSquirt.com read only forum (Jan.15,2018)

Hiya Guys....

Got myself a little problem here, finished assembling my first MS about 3 weeks ago. She fired and ran ( badly ) the first time i turned the key. Problem is its running really really rich and i cant work out why. One of my friends thought i had the TPS up backwards but i have double checked 0% at no throttle and 100% at full throttle. Ive spent every evening annoying the neighbours trying to adjust the fueling but when i lean the mixture it runs really really really badly....

Any thought of what to check next would be greatly apreciated.....

Many thanks

Dave

Oh MS2 v3 code 2.3 MT 2.25 Innovate LC-1 wideband.

Dave,

The most common cause of this is accel enrichment being triggered inadvertently, reuslting from the TPSdot (and/or MAPdot) threshold being too low. Can you post a datalog?

Lance.

Excuse the ignorance, i think this is what your asking for, i also have a much larger log if thats any good....

Many thanks

Dave

Dave,

Yeah, that's it. There doesn't appear to be anything obviously wrong in the log. What are you running: engine, throttle body or port injection, number of squirts, simultaneous or alternating, are you controlling ignition as well (if so, which module)?

Do you have the LC-1 EGO sensor? The log reports AFR of 8 to 9 - is that what it seems like to you? Does the exhaust seem like gas (I imagine it does!).

One thing you might try is enabling EGO correction, but only a few hundred above your idle. That will let you play with slightly elevated idle speeds and mixture, without stalling the enigne continuously.

One thing that is unlikely, but happens occassionally is that if the fuel pressure regulator (FPR) diaphram ruptures, it lets raw fuel directly into the intake manifold. So check that the vacuum line to the FPR does not smell of gas at all. You can also disconnect it and run the fuel pump to check it.

Lance.

Lance,

OK engine is an Audi 2.2 5 cylinder 10 valve turbo, on which i've removed the CIS and replaced with EFI port injection. Ignition is contolled by the stock ECU. 1 squirt simultaneous. Yes i have the LC-1 wideband controller whos software reports exactly the same as Megatune. The exhaust stinks of fuel and is covered in black soot.

I have tried to let the EGO correction deal with it this just makes the RPM bounce even more :-/

I have an after market fuel pressure reg installed and set correctly ( and double checked on a different guage, fuel pressure runs at a perfect 3 bar), however the vacume is not conected as the engine is turbo charged....

Oh and i checked temp sensors are reporting the correct temps, also out of curiosity i disconected the stock idle control valve, no difference.

The mystery continues......

Many thanks

Dave

Dave,

Is there a reason you don't want to connect the vacuum line to the fuel presure regulator (assuming you have port injection and not TBI)? That is how MegaSquirt (and virtually all other ECUs) are designed to operate.

The boost won't harm the regulator, it is simply balanced against the increased fuel pressure. The result is less fuel pressure at low vacuum, more fuel pressure under boost, and a constant pressure across the injectors (which helps set the proper pulse width).

What are you running for number of squirts, simult/alt., etc.?

Lance.

Lance,

Forgive me but i may be competley wrong but the injectors are designed to run at 3 bar of fuel pressure, if i add the vacume line wont that alter the fuel pressure therefore changing the mixture??

1 squirt simultanious over 5 injectors.

Many thanks

Dave

Dave,

Your injectors are designed to run at a 3 bar pressure differential between the fuel supply and the pintle.

If you leave the vacuum line unconnected, the pressure across the injector (from the fuel supply to the intake manifold), and thus the flow rate, varies as the intake vacuum changes (remember that the intake vacuum is sucking fuel, with the amount of suction depending on the vacuum). So you have to lower the pressure under vacuum, and raise it under boost, to keep the 3 bar differential pressure.

Read this for more info: http://www.megamanual.com/v22manual/minj.htm#supply (scroll down to the section on fuel pressure regulators).

Does your MegaSquirt work okay on the stim? Are all the LEDs flashing appropriately?

Lance.

Lance,

Oh !*@# i think i've made a huge booboo and overlooked that

Yeah MS works fine on the stim....

I'll make the additions tomorrow and let you know what happens.

Many thanks

Dave

This makes me wonder. My Saturn has a newer fuel injection system. There is no return hose from the fuel rail. Instead the fuel pressure regulator is located in the fuel filter which is just forward of the fuel tank. So really there is no vacuum feedback for the regulator. So how does this work really? I guess it could sense the fuel pressure on the injectors very quickly but that doesn't seem to accurate to me. Anyhow the stock ECU ran off it so I guess it shouldn't be a problem. Just a thought.

A.J.