Archives

Hello Hobbit

Hallewis sent an attachment in a PM on the FEH yahoo forum of a MMH slide show that I could not copy or send a link from. The torque curve was part of that slide show. I was able to take pictures of my PC screen to keep the information on my computer. I could not copy that picture here, so I sent an EMail to Wayne with a copy. Wayne will need to post that photo for you and others to save. It's not that I want to keep the torque a secret, it was just hard for me to post it. Many people on GH have ask for this information also. Looks like they will have to come here for it if Wayne post it here. Otherwise, PM me with your personal email address and I will send the picture to you.

This information is why I avoid 1900-2200rpm's as well as 3000-3500rpm's in the FEH. If I want WOT, I go to 3500-4000rpm's and hold till I reach enough speed and drop to 1800rpm's ASAP for that FE. This is also why I stated to Tarabell, I don't use the FS for RPM management anymore. Controling the RPM's at all times is my personal goal and you get much more FE in the higher torque areas IMHO.

GaryG

Here is the link http://www.cleanmpg.com/photos/data/508/FEH-MMH_Torque_Curve.jpg

GaryG

Ah, thanks. That's fairly peaky, in contrast with the Prius
Atkinson curve which is nearly flat. Does that curve represent
*maximum* torque, e.g. WOT or nearly so, across the whole RPM
range? Or is that accounting for how the engine is loaded
in some fashion?
.
_H*

My thoughts on this curve is that it represents the amount of foot pounds of torque the engine develops along the RPM scale.

The FEH electric motors kick in at max load (or WOT) at a given RPM on the Atkinson cycle engine. When the engine is cold, WOT can be at 1500rpm’s because the load exceeds what the Atkinson’s torque can put out under acceleration. You can see the Assist needle (electric motors) helping the engine at this point. This generally happens during the first half mile from a cold start here in FL. For this reason, I pack a FS or two in “L” into the battery as soon as I get to 30mph. Of course the battery is pretty much drained when I park it at night, so the ICE is using much of its torque spinning the generator which is feeding the traction motor and battery. Together with the engine not warmed up, and the heavy generator load, assist from the traction motor is necessary with a low SoC.

On the freeway, 1800rpm’s at 60mph is where I prefer to be. If I go faster, the tach starts getting hard to hold steady in the 2000-2200rpm range because of the torque output in that range level. Even head winds can cause assist off and on from the motors trying to hold say, 70mph. When I climb a bridge, I can hold 2300-2500rpm’s much better because of that torque range. The range from there is pretty good up to 3000rpm’s like Wayne pointed out, but the lower the RPM’s result in better FE.

If you have a link comparison of the Prius torque curve, it would be nice for us FEH owners to compare the two Atkinson’s.

GaryG

Ah, I made the assumption that people knew where to find my stuff...
http://techno-fandom.org/~hobbit/cars/prius-curves.gif
and everything else I've chosen to document or point to under
http://techno-fandom.org/~hobbit/#prius [which is my "website"
profile link anyways]
.
_H*

The March 20, 2006 issue of Design News, page 82-88 has an article on the engineer of the year, who designed the FEH. On page 86 there is a slightly different graph for the torque-rpm than what was posted earlier. Someone from GH scanned it in and posted it at http://www.greenhybrid.com/discuss/ice-horsepower-and-torque-curves.6445.html?page=1
(The on-line version of the article did not include the graph.) In this graph, the torque curve is flatter and more like the Prius, which one would expect. It also shows the combined ICE/motor torque output.

If Wayne would like to post this graph on CLeanMPG also, I can e-mail him a cleaned-up copy.

Thanks Hobbit and Green FEH

It looks like these curves, all are making different points. When I look and compare the two FEH and MMH curves, they match from 2500rpm's up. The MMH chart starts at a much lower RPM and the torque curve climbs fast to 150 FT pounds at 2500rpm's. The FEH chart begins at 2500rpm's and peaks at 170 Ft pounds, the same as the MMH curve. Since I prefer to hold RPM's below 2500, the lower curve give me much more info for my style of driving.

If your trying to show a V6 Escape that the FEH has more power (torque), that FEH curve shows the electric motors kicking in with much higher torque than the V6. Too bad the curve didn't start at a much lower RPM for comparison. If your in EV at about 5mph and floor it, the electric motors light those big tires up as the Atkinson starts up. The V6 would have a hard time staying up with the FEH till about 80mph from that kind of start.

Ah, the racing days. Stopped at Bev Smith Ford to look at the new GT500 Shelby Mustang sitting out front. If I never had the FEH experience, I'd be driving that 500 HP dream today. They made to look like my old 67 GT500, so my smile lasted all day. There was no window sticker on it, so I couldn't even see the price or EPA Estimates for hypermiler goals.

GaryG

Hi Green FEH:

___By all means, send it along ;)

___All of you have access to the Gallery so you can perform uploads of your own if you would like as well?

___Good Luck

___Wayne

Personally, I think the engine torque curve is not the curve you want to see to decide what RPMs to operate at.

What you need to plot is the specific efficiency - net watts per litre of fuel - as a function of rpm and throttle.

In other words, how efficiently is fuel being converted to mechanical energy.

The standard torque curve is more a statement of volumetric efficiency than overall efficiency. IE How well the engine is breathing per cylinder stroke.

anyhow, that's how I see it.

Personally, I think the engine torque curve is not the curve you want to see to decide what RPMs to operate at.

What you need to plot is the specific efficiency - net watts per litre of fuel - as a function of rpm and throttle.

In other words, how efficiently is fuel being converted to mechanical energy.

The standard torque curve is more a statement of volumetric efficiency than overall efficiency. IE How well the engine is breathing per cylinder stroke.

anyhow, that's how I see it.

What I've learned from the torque curve is what not to operate the engine RPM at. The lower the RPM seems to be the most FE way in my FEH. When I need more power for traffic situations, I look to the torque curve to set my RPM's and stay away from flat areas.

I'd be willing to look at:
"What you need to plot is the specific efficiency - net watts per litre of fuel - as a function of rpm and throttle."
to improve my mileage, but I haven't seen that in any graph I've found to date.

GaryG

Does this (http://techno-fandom.org/~hobbit/cars/SAE-bsfc.gif) help at all? It's from an SAE paper discussing Prius
throttle control, but shows a fairly typical BSFC contour where
the numbers become "smaller" as you climb the mound. The dark
lines indicate how the Prius tries to stay in the efficient regions
at high torque, low RPM as much as possible. I have this chart
semipermanently taped into one of the back triangle windows of
my car, and am always pointing at it to explain Prius efficiency
features to people.
.
The curve is fairly flat, I think because of the Atkinsonization,
in a somewhat atypical way from "normally-tuned" engines, but
in my mind that's far offset by the FE benefits.
.
_H*