SG Fuel cut off value

[theholycow]

Originally Posted by civic lover

Of course I didn't think this. But when I am driving it says it is only like 2 hp. This just isn't correct.

Ok, if it's reading 2hp while steady-cruising, that's definitely got to be incorrect. At what speed did you see that reading?

[dkjones96]

Originally Posted by PaleMelanesian

Wow.
Using that same ratio, on my car, to calculate the value of a transmission swap.

My car currently runs 2750 rpm at 60 mph. Changing to a CX or VX transmission would drop that to 2200 rpm at 60 mph. Using this calculation, it would raise my steady-state mpg at 60 from 43 to 54 mpg!

You are assuming the engine can still produce enough torque that low to still keep you at 60 efficiently.

You'll most definitely find yourself downshifting to accelerate and using more throttle than you used to. In town you might feel you can rev lower but freeway is a whole new ball game. I always wanted a 5th gear for very low rpm in city-only driving and on the freeway it just went back up into 4th for a 'normal' highway rpm. I obviously won't be doing that now but it was planned.

[civic lover]

Originally Posted by theholycow

Ok, if it's reading 2hp while steady-cruising, that's definitely got to be incorrect. At what speed did you see that reading?

When I was watching it I was going 60 mph for 2 hp. I know I know...this isn't right, but that is what it is reading. I don't really care that it doesn't work. I just wanted to let people know that the xgauge isn't great, but if someone can correct me I would love to hear from them.

[slurp812]

Originally Posted by R.I.D.E.

13% of the fuel consumed by vehicles in the US is wasted idling.

My personal number is MUCH less. I am anti-idle.

[slurp812]

Originally Posted by civic lover

When I was watching it I was going 60 mph for 2 hp. I know I know...this isn't right, but that is what it is reading. I don't really care that it doesn't work. I just wanted to let people know that the xgauge isn't great, but if someone can correct me I would love to hear from them.

I see the same thing, maybe it doesn't like Honda's? I have an 2002 si, and its never read over 100, with my foot all the way to the floor.

[theholycow]

Originally Posted by slurp812

I see the same thing, maybe it doesn't like Honda's? I have an 2002 si, and its never read over 100, with my foot all the way to the floor.

How high was your RPM when your foot was on the floor?

[theholycow]

Ok, so I spent some gas on research this morning. We wanted to know how much gas is used at various RPM while not loaded -- in this case, using the normal meaning of "load", not the OBDII "load".

I tried various RPM in neutral in my 2002 GMC 5.3l V8, measuring with my fuel injector duty cycle meter. I repeated it multiple times and got some steady values, some that varied from one test to the next.
RPM Duty cycle
525 1.1 (Idle)
600 1.3 (Idle)
1000 1.7
1200 1.6 (WTF?)
1500 2.5 - 3.0
2000 4.0 - 4.4
2500 5.5
3000 6.9
4000 8.2 - 9.2

There's no redline marked but it's never shifted higher than 5500 and I hate all the ruckus involved with high RPM, so even getting up to 4000 rpm was quite distasteful for me...I wasn't going to bring it up any higher.

[palemelanesian]

Looks nearly linear to me, except for that one anomoly at 1200 rpm. I added in a linear best-fit model, with a 99% correlation between the two. (using excel's correl() function). A linear fit matches with the results from MetroMPG's test above. The only difference is, this is duty cycle and not mpg, so the linear fit is inverse of Metro's.
Attachment 1536

I wonder if there's some sort of intake or exhaust resonance at 1200 rpm. That might explain the dip.

[R.I.D.E.]

Thanks a lot HC and Pale, I was very curious as to what the potential for my original engine design would be.

Linear means my old VX would have used 80% of the fuel at 2000 RPM in maintaining engine speed.

I know increasing the load would increase efficiency, but a significant majority of that 80% is just keeping the engine running at that RPM.

This corresponds with some members who manage to achieve 100% over EPA ratings through hypermiling, because they are reducing (to the greatest extent possible) unnecessary engine running.

In the era of the rotary aircraft engine, prior to 1918, a direct comparison of the 1913 Mercedes grand prix engine and the Gnome racing aircraft engine reveals an interesting comparison.

Mercedes
22 liters@ 2300 RPM= 200 HP
Gnome
11 liters@ 1300 RPM= 160HP

Twice the engine displacement at 40% greater RPM only produced 25% more horsepower!!!!!!!!!!

That is the best direct comparison to the two engines I have ever found.

The question is:

With modern improvements in design and technology, could the basic rotary design offer similar improvements in power compared to a conventional reciprocating engine. With such an obvious difference in the direct comparison, it has been my belief (for almost 10 years) that a current roatry design, especially one that could transform itself into a flywheel, would offer a dramatic improvement in efficiency over any reciprocating engine that will ever be made.

Also you must consider that the air cooled rotary would have lost significant power in the aero drag of cooling itself. My best guess would be 20 HP.

Now we are talking about a theoretical situation (emphasis on theoretical) where you could build a modern rotary engine (not a wankel, but similar to the original aircraft rotary) that would approach 60% efficiency, cpmpared to modern passenger car diesels at 41%. This would also utilize Homogenous Charge Compression Ignition, and not need any emissions controls.

If this assumpition is correct and my in wheel drive produces the simple powertrain with efficiencies equivalent to my VX, we would be talking about a real 150-200 MPG 5 passenger car.

I hope I live long enough to see it happen.

regards
gary

[slurp812]

Originally Posted by theholycow

How high was your RPM when your foot was on the floor?

I did it today, and I was in 5th at 4000 rpms, and it was at 80 something.
I will try on the way home at a higher RPM, like 6500 in 3 or something