12 replies to this topic

[Kyle Freiheit]

Like almost everyone these days I log AFRs. Well this weekend on my first weekend on my refreshed motor I had some really weird AFRs. Normally I set my AFRs to fall a little bit from 13 to 12.7-12.8 but this weekend I could not get them to be consistent lap to lap. The curve is usually the same shape but not the same level but after reviewing the data there are a few outliers where the curve started higher and then jumped down.

 

Things I know

1) This was my first race on this motor since the refresh and I changed a few things so I ran the AFM flat(ART tuned) rather than pointing down like I normally do.

2) My Fuel pressure seems steady at 43 psi(tested in garage, don't log it)

3) I have a FPR from advanced autosport and kept adding FP to be safe

4) I have not checked the fuel pump, sock or filter yet

5) Battery Voltage was a little low but above 13

6) Water temps in the 170-175, Intake temps 150ish(90F outside)

7) Timing was set to 14

8) Injectors have 10 weekends on them

9) Innovate LC-1, logged with Race Technology DL1, Free air calibrated and seems ok. 

10) I have one ticking lifter that hasn't cleared yet.

 

 

Anyone seen this before?

 

 

[chris haldeman]

Looks too me the water temp was right on the edge of 2 maps in the ecu. 165-175 is is where the computer goes into hot map. Install a 180 t-stat or tape radiator too get too 180-185 and see if it's more stable

[chris haldeman]

Other possible cause would be a flaky tps. 1.6 tps is just 2 micro switches one that tells when at idle and the other that tells when wot. Wot position puts computer In fuel enrichment mode

[Kyle Freiheit]

Thanks Chris. Grabbed the FSM and Taking a look at the TPS. Could the temp sensor at the back of the head be going bad considering thats what the ecu sees? Just curious. 

 

Kyle

[chris haldeman]

Yes it could be failing. The plug too the rear coolant sensor is often broken too.it is very possible nothing is wrong and the temp was the only cause. If temp sensor and tps check out good run the car alittle warmer

[Kyle Freiheit]

Chris,

  That does seem to jive with my data from the morning session where I was having issues getting water temps above 165 but my AFR was rock solid compared to the race that was in the 170-175ish range. 

Things I had a chance to check this afternoon.

 

1)adjusted TPS, seems fine. I went through the sweep a bunch of times while measuring the voltage of both WOT and IDL and there weren't any erratic voltages.

 

2)Coolant sensor is new but I pulled the connector and will be cleaning and making sure there are no loose connections(that thing always looks twisted)

 

3)Fuel Pump pressure and bleed down. Either I have a leak(but I can't find) or my fuel pump doesn't seem to hold line pressure when turned off. It holds just fine when on but as soon as I turn it off it bleeds down. Book says it should hold 21psi after 5 mins.

 

Kyle

[chris haldeman]

Make sure you are pinching the line between the reg and line on frame rail too take the reg out of the test. If so I would say the pump is laying down on you. Rules recently allow and aftermarket pump such as a walbro ect

[chris haldeman]

That 160-175 range is a tuning night mare. Try a 180 t-stat. Here in tx I don't run one but up there with more temperate weather you may need it for consistent tuning

[Kyle Freiheit]

Thanks Chris,

  I don't run a tstat either but then again, 90 is considered really hot in Seattle.

 

Kyle

[Kyle Freiheit]

Quick update.

Fuel pump maxs at 60psi with return line pinched and holds 60psi for at least 5 mins. That's low end of spec but that seems fine now. The more I think about it the more I think it has to be electrical or ground related. Whether it is the temp sensor connector wiring, an injector wire etc. Going through all that stuff today. 

 

Kyle

[Kyle Freiheit]

So, I'm thinking it was the temp sensor plug 

 

1) There was a cel and it said the temp sensor

2) We pulled that plug and put it back while at the track working on other stuff, so it could have been loose.

3) There was a little bit of oil from a small cas seal leak. 

 

I cleaned the plug with electronics cleaner, checked sensor voltage and resistance,  checked(wiggled) while testing continuity for both wires to the ecu and everything checked out fine.  After clearing the cel and restarting the car the idle AFR fell .75-1 point. 

 

In my defense the CEL is right behind my DAQ. 

 

For future reference if anyone runs into this issue, according to the FSM if the ecu gets a bad signal or no signal the ecu defaults to a reading equivalent to 65F(Same with the AFM air temp sensor). Not sure how a 65F(voltage equivalent) coolant temp sensor is the Safe Mode as it makes the ecu lean out about .75-1 pt AFR but my plan is to head to the dyno and cross my fingers. 

 

Kyle

[James York]

A bad coolant sensor or bad connection will read "cold" and place the mixture to super rich.

[Kyle Freiheit]

That's what my thought process says too....so, either I didn't fix the real problem(which is possible) or my data disproves that notion in this scenario.

 

Kyle