MS1, V3. Running stock CAS with 2nd VR, BAC mod, boost controller on a GSL-SE 13B 6 port and a China T4B using TII intake manifolds.

A friend and I wired up the car a few years ago and ran for a year on the dizzy, then converted this past winter to 2nd gen ignition. At the same time I added the BAC mod and boost controller.

Everything was fine during the initial tuning and the car ran great in boost pulling a smooth 11.5:1 across the range to 10 PSI. Due to wastegate plumbing issues we have not yet been able to raise the boost past 10 PSI. Now that those issues are solved, we went out to tune the car on Thursday but experienced an odd problem.

With no other changes to the car, the wideband was suddenly reading wrong (at the ECU) and the car was pig rich under boost. It went from 11.5s to 10 flat and misfiring.

So, I made the following checks:

-regrounded the wideband to the same point as the ECU by crimping both wires into the same terminal connected to the ground

-measured the voltage at the wideband VS. the Megatune display. It's about 0.5V off at the ECU from what the voltmeter says

-so I then checked the input circuit on the Megasquirt board. Everything appears fine. There's not much to go wrong here.

Any ideas? The one thing I have not done is check the gauge output itself and compare it to the AFR reading on the gauge. But I have not made this check because there is an obvious voltage difference between the gauge and the 'Squirt.

Ignoring that problem for the moment I tried to eliminate any Megasquirt related issues with the rich mixtures.

I did the following:

-reload firmware and load the last working MSQ

-verify the primary/secondary scaling factor (it was fine)

-make a datalog

Unfortunately I don't have any datalogs from when the car was working correctly so I have nothing to compare to. Injectors PWs look a little high for the injectors used (I think 550/1000) but not unusually high and there is nothing on the log to explain higher PW so I can't imagine that it is the Megasquirt enriching the mixture. I've attached the datalog. Pay no attention to the AFR reading, it is wrong as mentioned above.

Just looking for any ideas on the richness (and also the O2 voltage error above) before I tell him to start looking at a mechanical problem.

Thanks!

 

Fuel pump having issues? I've seen that before on a fuel pump that's about to go.

If the O2 is reading bad, there's a voltage offset there somewhere, or the circuit for reading voltage is having trouble (or the ms1 itself is having issues).

Are you using low impedance injectors? If so are you driving them directly from the MS or through resistors? If you're driving them directly, a component in the flyback circuits could've gone bad (causing the rich situation).

Did you check to see if accel enrichment was triggering when it was rich?

Ken

 

Do you have a scope? You could also verify that with the injectors connected, the commanded pulse-width and actual pulse-width match closely.

Looking at the log I don't see anything strange, so the only thing I can come up with that would cause a sudden change is the fuel pressure being higher for some reason, meaning the fuel pump is suddenly running faster, or the fuel pressure regulator is suddenly causing higher pressure.

Ken

 

Oddly, the car has chewed through a fuel pump due to debris in the tank but now runs a large prefilter and a new pump. There is a lot less trash collecting in the filter so it looks like the tank has been flushed. However, as I have already suggested to the owner of the car, I'm betting a tonne of junk went through the fuel system and could easily be clogging the injectors and causing them to stick. I mean, there was a load of debris. Cups full of sand. It was truly amazing. He's reluctant to pull the injectors hence I'm posting this topic...

I'm leaning a bit towards the CPU and have an extra one to swap, which I will do when convenient. There was a previous incident in which an e-fan was connected backwards and popped the transistor.

The datalog didn't show the accell was triggering, which was one of the first things I checked.

Now that you mention it, the flywheel circuit is probably high on the list. They are low impedance injectors, no resistors. Guess my next check is the flywheel circuit.

As my scope is a Heathkit 10-12, I won't be using it for any PW measurements anytime soon.

Fuel pressure has been consistent throughout (except when the filters were clogging or the original pump was dying).

 

For the flyback stuff, did you run an independent +12v for the flyback circuit back out of the MS? Usually if you don't, you end up with noise issues.

I guess if he had that much crap in his fuel system, he could have debris lodged in the pintles of one or more of the injectors.

Luckily a new MS1 CPU only costs about $20.

Ken

 

I have a few MSI CPUs around so swapping isn't a big issue.

I've never heard of this flyback mod before, so I'm about to head over to the Megamanual and check it out. It did work for over a year previously on the dizzy, and several months on the CAS though.

Yeah, the fuel injectors are at the top of my list. Another car I did had dissolved mice in the fuel tank (!!!!) and exhibited the same issues, though it was randomly lean as well as randomly rich.

 

Dissolved mice? I wonder what they do for the fuel's octane rating!

Ken

 

I'm not sure what they did for octane, but the resulting goo clogged the post-fuel pump filters. The pumps worked so hard to overcome the blockage that they actually bored a hole through the stainless element. Unfiltered fuel spread throughout the system, combined with mice innards that had been macerated by the pumps and caused no end of headaches. Compounded with the fact that the owner of the car didn't feel injector cleaning was necessary and it made for a frustrating experience.

Anyway, the injectors were pulled from the RX-7 and found to be full of crap. So they are currently out being cleaned. We'll see what the result is when they are reinstalled.

 

Looks like the situation is resolved. The injection shop said that one of the primaries had a 20% difference in flow compared to the other (both GSL-SE) and that the pintel of one of the secondaries was jammed up. Guess that is the result of the gunk that went through the fuel system. Once the new injectors were installed and the VE table adjusted to account for the new 460CC primaries (all that we had available) the car purred perfectly. The wideband seems to be reading fine and a datalog and analysis with MegaLogViewer took care of the bottom of the map so we could start retuning the boost section. So far, so good...

 

Good news then. I'll keep in mind that I might need to look for dead mice in my injectors next time this happens!

Ken