More questions about P&G w/ an auto tranny

[GeekGuyAndy]

Swng, Even pulse and glide in gear will help your mileage a good amount I think. Watching the scangauge in neutral I can see 300 or 400 mpg, and in gear it would be less, but still much higher than 30, so it will help.

[swng]

I will definitely give it a try!

[MetroMPG]

swng - do you have a ScanGauge? I did a quick search of your posts, and nothing came up.

PS - Snax, sorry for the hi-jack. I'll split off the auto/p&G discussion into a new thread if you like.

[swng]

Sorry I don't have that in my Yaris. However, I do have something similar (OEM trip computer) in my MB for some instant feedback. I may as well try some P & G with the MB. It is an auto car too.
Just do not want to do too many experiments with it.

[Jim Dunlop]

Can I reduce my idle RPM's by constricting the throttle body plate bypass hole?

[skewbe]

One of the finite number of nice folk on saturnfans suggested something like that when I wanted to keep my saturn from racing up after restart. It should help by limiting how much the computer can rev it up (which is a lot sometimes).

I just unplugged the lead to the idle control motor for now (when it was at about 900 RPM). Naughty computer, no idle control for you!

[Snax]

Originally Posted by MetroMPG

swng - do you have a ScanGauge? I did a quick search of your posts, and nothing came up.

PS - Snax, sorry for the hi-jack. I'll split off the auto/p&G discussion into a new thread if you like.

No worries. I only started the thread to give Mazda5 owners a place to start.

[MetroMPG]

Originally Posted by GeekGuyAndy

Swng, Even pulse and glide in gear will help your mileage a good amount I think.

I'd wager not.

In my car, using N and idling while gliding, I once measured an 8% FE increase over steady cruise at an average speed of about 80 km/h (70-90 pulse). When you factor in the less efficient pulse of an auto tranny (my car's got a manual) and on top of that the added deceleration from gliding in gear, I think you'd be hard pressed to come out in positive territory.

That's why I asked about FE instrumentation - I think it's going to cut it close enough, it's the only way to know for sure.

EDIT: of course, this all depends on the transmission. Perhaps it freewheels nicely once the torque converter locks up, or something like that, and I'll have to eat my words.

[Jim Dunlop]

Originally Posted by skewbe

One of the finite number of nice folk on saturnfans suggested something like that when I wanted to keep my saturn from racing up after restart. It should help by limiting how much the computer can rev it up (which is a lot sometimes).

I just unplugged the lead to the idle control motor for now (when it was at about 900 RPM). Naughty computer, no idle control for you!

One of my complaints about P&G is that the idle "drifts" down after I pop out of gear, and settles around 1200 RPM while moving. At a stop, it drifts down to 750 RPM. I want it to go to 750 right away (as long as that won't hurt anything). With the RPM's drifting down, the Glide part of the P&G may not be as efficient as leaving it in gear and letting the ECU cut off fuel injection.

Can you tell me where the idle control motor is and what it looks like? I want to do what you did (as long as the engine doesn't idle rough when cold). I feel so sorry for the poor, confused computer though. It must be a rough life dealing with people like us!

[skewbe]

The engine WILL idle rough when first started, sorry, thats the price you pay. I left the engine at about 1000rpm to compensate (I don't spend hardly any time idling anyway).

On my saturn (97 SW2), the plug is between the throttle body and the firewall. It is the bottom of the two plugs (top one is probably tps).

But, yah I thought that 1200 rpm thing while coasting was strange too, and don't count on it cutting the fuel off completely in overrun either. The only way to get it to stop wasting gas is to kill it completely (10 amp microswitch in-line with the FI fuse does a good job).