Question about EOC with an Auto... :confused:
 

Hi All!

Im new to the site and new to Hypermiling (although at this point i would call myself a sub-hypermiler).

Ive been perusing MetroMPG.com, Gassavers.org, CleanMPG.com and this site of course :p

I am slowly learning the lingo and science behind Hypermiling not to mention some of the car/engine/transmission limitations that I will have to overcome.

By no means is any one situation the same due to age and wear of parts, but I feel that I can still learn from others experiences to help with my own.

This brings me to my question. I have been reading about Pulse and Glide, Engine Off Coasting, and Deceleration Fuel Cut Off.

I guess what I drive will help... I have a 1996 Acura TL 2.5L Inline-5. I wanted to get something fuel efficent, but this car was mint and my uncle let it go for half the kelly blue book price, so it was cheaper than a Civic or Metro of similar age/condition.

My question is this. I know that Honda's have a lean burn mode (so Im assuming that acura's do too) and that for an automatic its best to DFCO with the transmission in gear to power the engine since the fuel has been cut off. But can i really EOC?

Well, I got to screwing around (i got bored, who doesnt from time to time) and wanted to see what the car could do, if anything on a EOC. I get up to crusing speed on a nice area right before a downhill grade and kick the car into neutral. No issues rolling fine, but the engine is down to idle speed and burning fuel. Well, lets cut the engine to stop that. I key it off and then right back to the ACC selection (dunno if thats right, its the second click choice, the one that would let you activate the ECU along with accessories). Engine speed starts reporting again and all my usual lights click on, so when I get a scanguage that will be fine, and engine is off with 0 RPMS to verify. I coast down to 45 from 60 and then with radio off to listen, restart the car. I didnt hear any grinding of the starter since it had no load on the engine, and then popped it back into drive. No transmission lunge, jerk, pop, or anything. And to boot, it was already in forth gear. Of course i didnt apply any gas until the engine RPMS went back up for the normal range at that speed.

After that little test, i think that I could EOC with no issues, and even tested braking (had about 3 good pumps left) and steering (not an issue from lane to lane) on another EOC down the next hill.

Is there an issue here that Im not seeing? I really dont want to mess something up on this car. I am already getting around 3 MPG than the updated EPA standard and really think that I can get this car to around 40 just on mods but really want the driving skills and techniques to push past that figure.

Anyone else find that they can do this on their car or currently do this?

Thanks in Advance,

LBS

read your manual, can your car be towed with all wheel on the ground?

if not u may burn up your tranny, by not letting the fluid circulate.

Here is an quote from my Acura Service Manual:

If the vehicle cannot be transported by flat-bed, it should
be towed with the front wheels off the ground. If due to
damage, the vehicle must be towed with the front
wheels on the ground, do the following:
• Release the parking brake.
• Start the engine.
• Shift D4 to position, then N position.
• Turn off the engine.

That is essentially what I did... only the parking brake was never involved

It seems like I would be safe. Would you or anyone else agree? or do all car manuals say the same, but end up blowing up transmissions?

Welcome, fellow Acura hypermiler! Yes it is possible to EOC, but just be very careful and pay close attention to the transmission since Honda/Acura automatics are notoriously fragile as it is. (Interestingly enough, their manuals are all but bulletproof) My suggestion would be to get a ScanGauge and monitor when the fuel cuts off. When it cuts off just stay in D4, and the times it doesn't, coast in neutral. The gas used is minimal and it will save your starter in the long run. Just my 2¢.

One more story, take it as you like.

I tried EOC with my automatic Cobalt which is supposed to be ok to flat-tow. Upon restarting the engine I had transmission issues which caused jerky shifts until I was able to leave the car sit turned off for about 30 min. So, I wouldn't do it again in that car. Not saying your Acura is the same.

What damage that may occur is cumulative and probably not immediately noticeable until the most awkward moment. If you must EOC, do it for short periods of time/distance. Be warned that you're rolling the dice if it is not flat-towable.

I had a 1999 TL 3.2L and now a 2006 TSX stock auto in the garage. The steering is the first to show a deficit. It gets pretty rough to steer, so be aware.

Including the '98 Integra automatic (daily driver), I can't really quantify the wear on the auto-trans at 137K miles. The recommendation is to keep it short and sweet.

RH77

Basically, with an auto, its not worth it to EOC.
I have tried it, it can be fun and dangerous, but you really should just coast in neutral. It's a lot easier on the whole vehicle and less work for you. Plus you don't have to hear your radio cut out or scare passengers!

Well, upon further (and difficult due to the rarity of this engine/tranny combo) research i found out that I could EOC, but Acura recommends this only for short distances of around 25 miles and only at speeds slower than 35 MPH so its pointless.

Im now trying to confirm that i do have a deceleration fuel cutoff for this ECM and to what RPM until it starts pumping fuel again.

Dont you love answering your own questions...

If I had only waited a few more minutes before I posted....

Exert from my Acura Service Manual:

"Fuel Cut-off Control
• During deceleration with the throttle valve closed, current to the fuel injectors is cut off to improve fuel economy at
speeds over 1,250 rpm.
• Fuel cut-off action also takes place when engine speed exceeds 7,100 rpm, regardless of the position of the throttle
valve, to protect the engine from over-revving"

So, since i have been getting up to 40 MPH in 4th gear (my highest gear) with the auto shifting at 2k RPMS, i guess i will need to down shift into third when i decide to FAS (i think i used that term right even though i dont have a hybrid)

Here is one interesting thing i did read though:

Although, one idea that came to mind, although I dont know how dangerous this is and it would have to be watched to ensure I dont have to restart the engine is possibly splicing into the same wire that the ECM uses to cut power to the injectors and have a manual way to DFCO.

Im not sure that it would be beneficial though.

On a side note, I did order a ScanGauge II this morning, does it have an alarm feature that i could set to sound at the aforementioned RPM? Or does anyone know a way to set up a light to warn me before I get withing a few hundred RPM so that I can downshift?

Just a few thoughts to try and maximize FE.

Thanks again for all this feedback!

In my experience automatic cars will not cut fuel to engine for a long time when you are off the gas. When you get your scanguage you will know for sure, just watch the instantaneous MPG gauge. I think this is to do with how an auto works.
As for EOC, since your tranny doesn't have a good reputation I wouldn't bother. Do coast in neutral idling though, idling uses way less gas than even using 3% throttle to keep the engine from braking.
Ian

I believe there's a glitch in the SG that doesn't show DFCO. My Acura shop manual states the same -- down to 1250 RPM. I think it's fairly instantaneous.

Some have installed a blinking LED to indicate if their injectors are firing -- or a multimeter may do the same for experimental purposes.

I commonly downshift to scrub speed, but rev-match to reduce wear.

RH77

My SG shows DFCO occurring immediately as long as I'm above my minimum DFCO limit (1400rpms).

So at 60 mph does your engine stay over 1400rpm when you let off the throttle? I've found my Neon will cut fuel for a second or two when I let off the gas with the engine over 3000rpm but then it goes back to adding fuel when the rpm drops. I guess having a 3 spd auto with a "looser" torque converter than a 4spd auto they decided not to be aggressive with the fuel cut off.

I EOC aggressively with my automatic Vibe, at speeds less than 50 mph when coasting back to 0mph. In my case the longest stretch I encounter is 1/2 mile and the only issue I can warn against is the power steering which obviously gos from easy to hard to easy as you bump the engine back on.

I recently switched tranny oil to synthetic in order to put my mind at ease regarding any abuse to a non lubricated tranny, but with distances less than 1/2 coasting, I am rolling the dice to see if it causes any future damage. I feel the $$$ I am saving now is worth the replacement manual transmission if it does blow. At least the money won't go to oil .. LOL

Yes. It takes time for my throttle to drop while the DFCO takes into account RPM and speed, so it USUALLY ends at 1400rpm and 32mph (I've seen it cut out around 1200 rpm). To put this into the context of time, my own tests showed D-coasts from 45 to 32mph takes an average of 13.5sec. An N-coast from 45 to 32mph, it takes an average of 28sec. That's why I use a combination of the two: D-coast in DFCO then N-coast the rest of the way to get the most MPG out of the distance.

Yeah, it sounds like your car wasn't designed to be as frugal with the DFCO. :(

I'm also figuring out my optimum TPS per speed proportions and it's really helpful for refining my cruising behavior. Load accelerating has also been great. No more tortoise starts for me (if I can help it)!!! :turtle:

Cool, another Auto Acura driver :) Same year as me too. Welcome, mate.






I've got a scanguage II in my Integra and it reports DFCO just fine, MPG goes to 9999, GPH goes to 0.00 and CPM goes to 0.000 Can't be more definite than that. It usually only takes a second or two before it engages, and when you pay enough attention you can sort of "feel" how the car pulls differently when it kicks in. It feels almost as though someone started very gently pushing the brakes. As an added bonus if you turn your AC on while you're in DFCO it doesn't really hurt your mileage. You can also feel how it's like someone's pushing that invisible brake pedal just a little harder.

Are you running the "X-Gauge" program with the SGII? Mine is about a year old without the CPM option. I haven't seen 9999 unless I shut down the engine on coast.

I may turn it in under warranty. Some pixels are going out on the bottom-right, first number displayed (on mine it's MPG, so a bit frustrating). I'd see about adding additional parameters if it's worth it.

Yeah I feel the exact same feeling as you mention. Then at 1250 the TC disengages and raises the RPM a bit to fire things back up.

By the way, I've been having a surge issue over the last several months. At steady cruise, I can feel something like a miniature A/C compressor kicking-in -- then ~30 seconds later, whatever it is disengages. (A/C is confirmed off) I have an ancient battery (~6-years old) and I'm wondering if it's the alternator asking for more demand to charge the batt. It could be the fan kicking-on. No changes in voltage, but a slight drop in FE is noted. Can't figure it :confused:

RH77

That sounds like a pretty viable culprit. I've sat at red lights watching my voltage and gph usage while I turn stuff on and off , lights stereo fans etc. The voltage never changes, it always goes between 14 and 14.1 but there's a definite, although sometimes subtle change in GPH when things are added to the alternator load. I just replaced my battery last year.

I don't think it's a glitch in the Scan Gauge II. There's an interview with the designer in the blog post at the Metrompg site, here, he states that it's to do with misreporting of the fuel injector status by the OBD II in some vehicles.

Which is odd, because we have identical vehicles, just 2 years apart (probably the same OBD-II program, maybe subtle differences).

As the interview mentioned, the difference is likely small. Pump readings vs. SG averages are now calibrated (10.2% difference) so I'm happy. If I want to know if fuel cut is active, I'll install an indicator or something (low-priority right now though).

RH77