Light versus Heavy Throttle Acceleration

[SVOboy]

I'm in a huge rush to get my computer packed up for my 8 am departure to college, so I'm just gonna throw it out without introduction: http://crxmpg.com/accelmpg.html

[white90crxhf]

interesting, i wonder what the test results would be if there was no shutting off of the engine, i imagine most people would rather not shut of the engine, me included.

[zpiloto]

Originally Posted by white90crxhf

interesting, i wonder what the test results would be if there was no shutting off of the engine, i imagine most people would rather not shut of the engine, me included.

I imagine that the percent increase would be be same, just lower numbers on the total FE imagine I do.

[GeoMetry]

I wonder about how this works in city driving that has a lot of stop and go. If you stop every 1.5 miles how would that effect the results?

[SVOboy]

As I said, I think more distance between stops would increase the benefit of this. But I'm not sure. I stopped every 3/4s of a mile or so. Anyway, leaving the engine on would yield the same results except mehbe slightly closer, there's really no reason to leave the engine on though,

Damn this hotel lobby computer...

[ZugyNA]

I think you'd get more "accurate" results by using a chain to DEFINE the actual throttle opening you are using...and the tach to define the shift points.

It's very inaccurate to guess as to your actual throttle opening.

Not trying to be overcritical...that's some good info and a good bit of work.

Interesting results....

[MetroMPG]

Valid point Zugy. Perhaps a chain is overkill though - something (e.g. wood) of varying thicknesses placed beneath the gas pedal would be easier if you wanted to do the test using a physical restriction.

SG users could also watch TPS and/or LOD values.

Then again, knowing throttle opening values exactly may not help other cars since they have different fuel / throttle position maps.

Maybe timing the slow vs moderate rates of acceleration would be a better comparison point.

[psyshack]

I always thought the floor made a good throttle stop.

[JanGeo]

Originally Posted by psyshack

I always thought the floor made a good throttle stop.

HA HA HA HA . . . . IT DOES!!!

[JanGeo]

Here is another arguement for idling an engine when it only uses .1gph - to pay $10,000 extra for a hybrid I could idle my xB engine for about 2,000,000 minutes for that much money in fuel.

[rh77]

In city driving, I'm seeing much better FE results by getting up to speed using 50% throttle and a 3500 RPM cutoff -- The Scanguage is showing closer to 0.5-1.0 MPG from my previous slow acceleration. I'm glad too, because it makes getting on the highway easier up the ramp. Then Pulse and Glide takes over and/or momentum for hilly Interstate driving and we're in business...

RH77

[ZugyNA]

Originally Posted by MetroMPG

Maybe timing the slow vs moderate rates of acceleration would be a better comparison point.

You mean using a scan gauge or other (?) to determine fuel use per sec or whatever...up to a certain speed?

I think the driving process is more complex than that as far as engine load, throttle opening,RPM, and gears and so forth....

I don't think people actually realize how much throttle opening they actually use.

My guess is that most people only typically use 1/4 to 1/3 at most...and 95% of the time maybe 1/15th to 1/25th.

You don't start to know till you actually use a block of wood or a chain?

Now lets be a chainin' them gas pedals down!

I USED to do a lot of jack rabbit starts from stop signs up thru 3-4K...when I got 21 mpg...now I manage 28 mpg...still cruising at the same highway speeds though. Some of it is from other mods though.

Now I need to buy a fuel efficient car.....

[rh77]

Originally Posted by ZugyNA

You mean using a scan gauge or other (?) to determine fuel use per sec or whatever...up to a certain speed?

I think the driving process is more complex than that as far as engine load, throttle opening,RPM, and gears and so forth....

I don't think people actually realize how much throttle opening they actually use.

My guess is that most people only typically use 1/4 to 1/3 at most...and 95% of the time maybe 1/15th to 1/25th.

You don't start to know till you actually use a block of wood or a chain?

Now lets be a chainin' them gas pedals down!

I USED to do a lot of jack rabbit starts from stop signs up thru 3-4K...when I got 21 mpg...now I manage 28 mpg...still cruising at the same highway speeds though. Some of it is from other mods though.

Now I need to buy a fuel efficient car.....

Here's the deal -- my car's TPS on the ScanGauge is 10% at the minimum and 96% at the max. Ideal cruise is 19%, which should be 9% throttle input. The position sensor isn't accurate, but it gives you a good idea where you are. Now on some cars I've driven like the VW Jetta, it jumps from 20 to 45% in a mere milimeter of pressure.

On my TSX with the throttle by wire and i-VTEC, I'm clueless how to approach that.

On an even seperate note, I think we should have TPS Cruise Controls. Set it for a certain percentage instead of speed for maximum momentum, contant pedal pressure and super-duper FE.

RH77

[ZugyNA]

Originally Posted by rh77

On my TSX with the throttle by wire and i-VTEC, I'm clueless how to approach that.

On an even seperate note, I think we should have TPS Cruise Controls. Set it for a certain percentage instead of speed for maximum momentum, contant pedal pressure and super-duper FE.

RH77

If you have a gas pedal...the block of wood still works? You can always go low tech if you need to? Though the wire or chain method is easier to adjust.

[SVOboy]

The block of wood won't do anything with i-vtec which will go WOT on it's own to reduce pumping losses. It kind of does its own thing,

[ZugyNA]

Danged modern technology!

[BuffaloChips]

I am going to throw out something crazy and say the marked improvements were greatly influenced by the fact that he skipped 4th gear altogether.

[SVOboy]

I skipped 4th gear in both runs, and always skip forth gear. It's somewhat useless. I don't see how it would effect anything besides to use more fuel in the slow start by forcing the use of a gear that is lower than need be.

[Brock]

Here are some findings I had from last spring when I ran this.

I think you’re correct in assuming without EOC'ing the advantage might not be the same. Also my understanding is gasoline engines are more efficient under more loading, again making EOC'ing more where diesels are more efficient at lower loading.

I should run the same test with the van and see how it fares.

Ok, this proves I am crazy.

I found a stretch of highway that has a 2.1 mile run between turn offs. I ran in each direction twice at the same acceleration and got up to and stayed at 65. When I went to turn off (2.0 miles), I took the reading off scangauge right before I released the throttle. So basically these are 4 runs at each acceleration rate. None of the individual runs ever varied in to the range of the faster or slower run, with amazing close numbers for each run not varying by more then 1 mpg. I have to say I was surprised at the results. I thought the slower acceleration might be a bit better, but thought it would be very close, almost not noticeable. I could have accelerated even slower, but I was turning on to a 2 lane divided highway and wanted to do it as slowly as I could while being safe. Take it for what it’s worth.

slow run up to 65mph
37.5 mpg

normal or medium run to 65mph
33.9 mpg

fast, or as fast as I could shift and go to get up to 65
29.1 mpg

As far as getting up to a good FE cruising speed it will never make up for the extra fuel used to get you there quickly, at least not with my diesel engine. Again with a gas engine and engine off coasting I believe it.

[smartzuuk]

I tend to agree with the initial findings from post # 1 - I know in my diesel smart, getting into 4th gear (of 6) is better for FE in the city than going slower in 2nd and 3rd. I haven't yet had time to verify this with Scanguage, but I will in due course.

Great topic!!