Can someone with more knowledge of the Renesis than I have (and that's not saying much) help me out here.

I have recently bought my car (2010 - 8200 miles) and the gas mileage is bad even by RX8 standards. I bought an OBDII bluetooth device to use with Torque App and it works great.

However I noticed on my trip to work that the fuel mode never went closed loop. It remained in "open loop due to insufficient temperature". The trip is about 30 minues part city streets and then 10 miles on freeway. The coolant was running at 200-205 Deg F.

On the trip home it went closed loop as soon as it warmed up, probably less than 5 minutes, and remained that way for the whole journey.

Today to and from work it remained open loop due to insufficient temperature although ECT was again at 200-205 Degs F.

I have noticed that I only get an O2 voltage signal from one sensor, bank 1 sensor 2 I think. I was expecting to see at least and upstream and downstream O2 sensor for the cat monitoring.

There are no codes stored and no CEL. This confuses me as I thought that there was supposed to be a code set for not going closed loop within 15 minutes of startup.

This seems wrong to me. Any ideas of comparisons would be appreciated.

 

nothing wrong with it, ltft and stft changes constantly, its base on ur temp, speed engine load and a couple other things.

I'm not sure how bad ur MPG is, might be time to have a little extra premix in tank and see if it improves?

 

Thanks I'll try some of the premix and see what happens.

As for the open loop .... I think I may have a bug in the Torque App. This morning I exited Torque and restarted and lo and behold it came up in Closed Loop. Seems like it might not be checking fuel status properly.

 

(Speaking from Series I experience), LTFT doesn't change constantly, it's a running average over 3 MAF ranges that attempts to get your STFTs in closed loop to average zero. I wouldn't expect premix to have much impact on a new Series II engine.

OP: One way to cross check if you're in open loop or not is to see if the STFT sits at zero. Too, closed-loop AFRs should be near 14.7; if your LTFT is over +10 or so, you may have a vacuum leak somewhere. Look at fuelly.com and see how other RX-8 owners are doing with mpg. Sign up yourself and add to the database! City driving is a mileage killer in any 8 though. Also, your 4.77 rear end vs the 4.44 of Series 1s won't help either.

 

I signed up for fuelly a week or so ago, that's a pretty good site.

I have been seeing mid 15 mpgs (as low as 14.5) for mixed city and highway driving. Driving it sporty but not thrashing it. Only got 17 on a freeway run at 75mph on cruise control.

I am about 3-4 below most on fuelly. That may seem like only a couple low but it is still 20-25% which is a significant difference from the norm.

LTFTs are about 2-6 % on the logger and STFTs usually around +/- 5-10% with spikes on rapid throttle changes, but those are to be expected.

I thought that the non closed loop running would be the culprit but it appears that was just a red herring.

 

RE: Fuel consumption/economy what RPM limit do you 'typically' change/shift at?

 

If I am just coasting along with the traffic then typically about 4000, if I am accelerating normally then about 6000, accelerating hard, say onto the freeway, then 7000-8000 with the occasional fun run up to 9000.

I have tried "granny driving" and "spirited driving" but get very little difference between the two.

I never expect the engine to pull from under 3000.

 

Are you running stock tire size and pressures?

 

Yes. Everything is stock.