HCH II-Specific Discussions Model Years 2006-2011

What's your lowest RPM at 70 mph?

  #1  
Old 11-02-2006, 04:26 PM
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Default What's your lowest RPM at 70 mph?

I think I may be on to something here. During the trip home from Milwaukee this past weekend I noticed that I was at 60 mph and the tach was at 2,000 RPM and the IMA was neutral (no charging/no assisting). I was able to maintain this "steady state" of driving for quite some time though the terrain was mild (northwestern Indiana along I-80). It wasn't until an hour later when I was still on I-80 in Indiana that I was now doing 70 mph but the tach was STILL at 2,000 RPM. Next I tried to inch just a hair faster but anything over 70 mph causes the tach to move to 2,050/2,100/2,200 RPM and so on.

I'm wondering if anybody is able to go over 70 mph and have the tach at or below 2,000 RPM. If not then I think I found the sweet spot for cruising. Some stretches (wind, hills, etc.) allow you to go 65 mph for 2,000 RPM but other times it can only be achieved at 55 mph. Like I said, this is with neutral IMA and I think it really gets a good FE but am looking for other input.

Sure you get great FE at 55 mph but it is also possible to get great FE at 68 mph if you maintain proper throttle position and note the IMA charge/assist status rather than coasting down a hill to charge the IMA and zoom back up the hill and lose the charge.
 
  #2  
Old 11-02-2006, 06:02 PM
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Default Re: What's your lowest RPM at 70 mph?

Darren,

Interesting observation.

Having close 2,000 miles on the ol' "PinBall" all ready, the one thing I have tried to do remain constant with as been the revs per min. @ 2g's. Oh, it's It been the up's & down's from that number, as I try to master the tricks of "Pulse & Glide/Pedal Feathering", But one thing tends to remain a constant. The motor seems to have been designed to run @ 2 g's.

Like yourself, I have seen the mph spread quite wide, but depending upon terrain/weather conditions & foot feed pressure 2g's is a take even at 70 mph ( yes i have seen short runs 70 @ 2g's, but not sustainable because of the slight slopes/grades to the interstate here ). Kinda wondered how you were going to do on your trip, particularly thru Ohio & Indaina, because of as you said, the midness of the terrain. I have traveled that stretch many times. I would think it would be ideal for the even criuse. I get my shot this upcoming Thanksgiving with a trip out to the Toleto/Ann Arbor area to see my parents/oldest in school.

"Thee 2g's Factor" has been one of things, that even though it has only been 2 weeks of "Playing the Game", has caught my attention. It certainly makes me wonder just how all the mix comes-in to make it work. The fact the tranny operates the way it does with its belt & clutches may well have something to do with depending upon the amount of load being fed thru it. Wouldn't suprize me in the least if 2g's can be attained at a greater speed.

Interesting car.

John

p.s. What kinda mpg were you getting @ 70 mph bro ????
 

Last edited by nitrojohnny; 11-02-2006 at 06:43 PM.
  #3  
Old 11-02-2006, 06:11 PM
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Default Re: What's your lowest RPM at 70 mph?

Sounds like DWL (Driving With the Load) to me! If traffic allows, allowing the car to lose a little bit of speed over the smaller hills ought to prevent dropping to a shorter gear ratio in a situation where the car would otherwise "kick down" (if that term even applies to a CVT).

But I have a question. Even if you can drive 70mph at the same RPM that it wants to drive 60mph, aerodynamic drag loads still increase substantially. So what happens to the instantaneous fuel economy reading? I'm thinking that more fuel must be used to overcome the extra resistance.
 
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Old 11-02-2006, 06:40 PM
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Default Re: What's your lowest RPM at 70 mph?

Tim, you're definitely using more gas by going 70mph versus 60mph, but if you travel a greater distance across that loss, it could be a wash, or you might still come out ahead.
 
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Old 11-02-2006, 08:46 PM
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Default Re: What's your lowest RPM at 70 mph?

Or if the ABF triple-semi truck that you are following through OH/IN is doing 68 mph than I too am doing 68 mph and drafting behind him and at times this means going 56 mph up a hill (in a state with 65/70 mph speed limits) so it all averages out.

Nitro - On the way TO Milwaukee I got 45/47 mpg roughly but on the way back going WITH the wind I got 53 mpg (displayed). Some of the way back was at 70 mph and some was at 55 mph. I did the first 60 miles at 61.8 mpg (from Delafield, WI to near Chicago, IL). My wife drove the last 30 miles to the hotel and dropped me from 57.5 mpg at 145 miles to 54.5 mpg at 175 miles. HOW is it possible to drop 3.0 mpg in just 30 miles!?!? I have no idea but I banned her from driving any part of the leg home which was an additional 460 miles. I got home with 630 miles at a calculated 56.8 mpg. During those 70 mph stints the instantaneous was well over 50 mpg and that is why I stayed at 70 mph. As soon as that dropped to 40 mpg then I slowed down to 60 mph until the instantaneous climbed again.

So it sounds like others have found that 2k RPM at 70 mph to be the max speed but I'll await other responses. There are always hills where you go 80 mph down just to bleed off speed going up the next hill to reach the top at 55 mph and things like that. You are always playing the game but if there is an option of going 72 mph at 2,200 RPM and using IMA and charging IMA and using more ICE than minimum vs. going 68 mph at 2,000 RPM and no engine load and neutral IMA state then I will go 68 mph anytime. Sometimes this is 68 mph vs 62 mph due to wind and hills and things but I'm always trying to find that magical spot.
 
  #6  
Old 11-03-2006, 05:39 AM
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Default Re: What's your lowest RPM at 70 mph?

Originally Posted by mmrmnhrm
Tim, you're definitely using more gas by going 70mph versus 60mph, but if you travel a greater distance across that loss, it could be a wash, or you might still come out ahead.
Right, it's a given that you are using more fuel. But I was thinking more in terms of the fact that drag goes up exponentially with respect to speed. It might be a wash if drag is somehow matched by reduced pumping losses at a wider throttle position, but I really don't think that's likely. Fuel economy ought to go down somewhat.
 
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Old 11-03-2006, 05:41 PM
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Default Re: What's your lowest RPM at 70 mph?

brick - First of all, "I love lamp." Second of all, if you can get 50 mpg at 60 mph and a big truck is going 65 mph you just tuck in behind the big truck with your foot not giving any more throttle and suddenly you are getting 50 mpg but are doing 65 mph though using the same throttle (aka fuel) as going 60 mph. Sounds like a win-win situation to me. Sometimes you even use LESS fuel by traveling faster since you are drafting. Until you accomplish this I agree it seems odd to comprehend.
 
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Old 11-04-2006, 04:13 AM
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Default Re: What's your lowest RPM at 70 mph?

I believe drag increases as the cube of the speed, in case anyone is wondering how much they are costing themselves by going faster.

obviously there are other concerns such as the coefficient of drag. I couldn't quickly find the data for the 2006-2007 drag coefficient. You get the idea though. Basically its far worse than the square of the speed.
 
  #9  
Old 11-04-2006, 06:44 AM
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Default Re: What's your lowest RPM at 70 mph?

  #10  
Old 11-04-2006, 07:22 AM
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Default Re: What's your lowest RPM at 70 mph?

I don't think my car's been up to 70MPH....
 

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