More questions about P&G w/ an auto tranny - Page 4

Bill in Houston · 07-26-2007, 09:01 AM

Quote:

Originally Posted by Raccoonjoe

Also VERY interested to know y'alls thoughts.....Pulse at WOT, 80%, 50%, 25%, or <25% throttle??

I was wondering about this. The BSFC charts usually show the peak efficiency to be at about 80-90% of peak torque. BUT, I don't know how that translates to throttle position. I would not be surprised if 50% throttle gave 80% torque. I remember that the SG2 has a LOD parameter for engine load, but I don't know what exactly that means either.

Whatever you do, you want to stay away from open loop or some kind of WOT enrichment.

swng · 07-26-2007, 02:47 PM

Thank you gentlemen for the input above.
I once thought that shifting to "3" when gliding may induce DFCO but now it seems that the consensus is gliding in "N" should save most fuel.
With your input, I will have lots of materials to try to understand and lots of experiments to carry out

. In other words, there will be enough to keep me busy in the coming weeks/tanks. There are legal and other limits as to how much I can do though.

Hockey4mnhs · 07-26-2007, 03:01 PM

p&g works awsome in my auto i wouldent break 30 before i startd and now my best p&g tank was in the 38 range

Zvolen · 07-26-2007, 03:23 PM

Quote:

Originally Posted by swng

Yes, please post your results when you have them. Have you noticed any really useful drop in rpm when you glide in gear? I have not

. Does your car jerk when you shift from N to D as you finish gliding and wish to start pulsing again. Actually, I personally think I should rather shift to the "3" position for gliding in the hope to make the car's computer shut off fuel supply to the engine.
Also, I wish to ask if I should accelerate to the desired speed fast or slowly at the "P" stage.
Any advice will be appreciated.

I haven't notice a significant drop in RPM's but enough to make it worth wild. If my RPM's are at 2K constantly when I put the car in N they usually go down to 1100 or 1200. It would be nice if they went do to 800 or so like they do when in drive and stopped. My car does NOT jerk when I put it back in drive to resume pulsing again, however since most of my commute is on city streets most of the gliding is just up to the next light which I resume pulsing after stopping.

Actually as of yet I have not seen an increase at ALL in MPG while P&G however I still have a 1/4 of a tank left. Although that could be to a few other issues and will continue to test as well as EOC ( Engine off Coasting ).

swng · 07-26-2007, 03:56 PM

Thank you Zvolen.
Safe and happy motoring!

omgwtfbyobbq · 07-26-2007, 05:59 PM

Quote:

Originally Posted by Bill in Houston

I was wondering about this. The BSFC charts usually show the peak efficiency to be at about 80-90% of peak torque. BUT, I don't know how that translates to throttle position. I would not be surprised if 50% throttle gave 80% torque. I remember that the SG2 has a LOD parameter for engine load, but I don't know what exactly that means either.

Whatever you do, you want to stay away from open loop or some kind of WOT enrichment.

Throttle==Air==Torque, unless the car is drive-by-wire. Then the manufacturer has purposefully disconnected the throttle from the pedal in order to have lots of throttle tip in, so the engine will fo' sho' operate in those nicer BSFC regions when accelerating, and the EPA city mileage will increase. In effect, they figure that they have to automate acceleration to some degree for the consumer to accelerate efficiently.

Bill in Houston · 07-26-2007, 08:53 PM

Sorry, I wasn't clear. Is the air flow through the throttle definitely linear with respect to throttle position sensor reading?

omgwtfbyobbq · 07-26-2007, 09:59 PM

Heh, yeah, well, probably not. You may be able to infer that from the fuel maps or some crazy fluid dynamics. The easiest thing would be to go on a dyno, and see if you can have the TPS signal and torque logged simultaneously.

Bill in Houston · 07-27-2007, 06:08 AM

Where I was going with the idea was that I might be at 80% of available torque when the throttle is only (to my foot) only at 60%. And that pressing the gas to the point that feels like 80% might over shoot the max efficiency point. It would be nice to prove it with a dyno, for sure. Okay, I think I'm done thinking out loud now...