Congrats to COZX2 on the 100+ MPG fill! - Page 3 - Fuelly Forums

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Old 07-06-2007, 02:54 PM   #21
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It's freaking awesome you got 100mpg, but it would be even better if it can be real world driving IE not taking off alternator. The aero mods rock and the driving technique but on the alternator it's allmost like cheating it's something you need that you take off to get better mileage until your battery dies.

But still the mileage you got before the alternator was off is amazing.
korax123, Thanks. I only had the alternator off the car once for 6 miles. While it was off wired it with a switch. I guess some of my posts I did say alternator off, I meant switched off. All the miles in my recent tank were to my place of business and back, pretty real world.
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Old 07-06-2007, 03:14 PM   #22
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atomicradish -

CO ZX2 has been questioned before but he has proven his case to us over and over again. In my opinion his auto-performance background has dovetailed nicely into the work he has done on the car. He has exploited his car, his knowlege, and his environment to the fullest.

PS - I do admit that if you read it for the first time, it's hard to believe. But, keep reading.

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Old 07-06-2007, 03:56 PM   #23
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Yup, what Carlos said X2. If you run the numbers, you can see that 100mpg at an average speed of ~40mph is possible with a car like that.

Assuming (approximations) Cd=.25 from mods, A=2m^2, Crr=.007, W=12000N, and ro=.85. We get that at ~40mph=18m/s the car needs ~3kW=4hp on average. Minimum BSFC for most engines is ~250g/kWh, so the best mileage this car could get would involve using ~750g of gasoline per 40 miles. Or, since a gallon of gas weighs ~6lbs, or ~2700g, assuming he has the conditions available to run the engine at peak efficiency, he should be at ~110mpg@40mph. The thing is, his drag coefficient may be less than .25, and the CRR may be less than .007, especially with all the tires at 60psi, so until I see otherwise, I'm won't call BS. What he's getting squares pretty well with a car/route optimized for efficiency. If he started claiming 150mpg, then yeah, it's BS, but the physics pans out.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 07-06-2007, 05:47 PM   #24
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Thanks.

MetroMPG, thanks for putting this thread up. I, too, expected you or basjoos to be the first to post a 100 mpg tank on gasoline. And you very probably would have been first except for the time spent on ForkenSwift. I thank you for the thousands of posts you have made to date and your huge contribution to GasSavers success.

To all who have made comments on this thread: I appreciate your interest and kind words. Most of you seem to realize that the good fortune that has befell Old Reliable and me did not just happen, it did take a lot of work, a lot of thinking, an unrelenting desire to improve, and a lot of help and encouragement from fellow GasSavers members.

Hopefully I can pass on some of what I have learned in the spirit that prevailed here when I had questions to ask.

To try and answer questions that have been asked here, I will post later tonight with a detailed good faith estimate of what I feel my car mods have proven to be worth in FE. Searching my notes and working at it now.

Thank you all again. GasSavers is a great place to be.
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Old 07-06-2007, 06:25 PM   #25
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Hey CO, great job! What are all those dials/gauges in that black box. I think that what you've done is such a great controversy, I hope it brings more people to greater success in their FE. Its so much fun to tell non gassavers about you and your car and hear them scoff... and then actually consider it.
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Old 07-06-2007, 06:51 PM   #26
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Regarding your calculations, I recently found an aircraft site that cited 14% air drag difference 1000 ft. versus 10,000 ft. I would agree that the power drop is 30-35%. I am not very sure that should be considered an advantage.

Might be worth the trip. Whatever the results, we could have some fun. Lots of scenery, old homesteads from the mid 1800s, 80s max summer temps, 10% humidity, few mosquitoes and trout fishing.

Yeah, you're right, in comparing 1000ft to 10,000ft, aero drag drops 15% and ICE power drops 32%. But (assuming your ICE adjusts air/fuel ratio to compensate for altitude) that power drop would result in improved ICE efficiency since the ICE is having to operate at a higher throttle setting (less pumping losses) to get the same power output. Your high mileage is a result of your driving skills and aero mods, but the low air pressure driving environment also is a factor. If you were driving an Insight, you'd probably be getting 160mpg.

When they chose Oklahoma to run last summer's Insight marathon, at the time I was thinking that if they had run it on some fairly level, low trafficked roads on the Colorado Plateau in SE CO or southern UT on the plateau at 8000 to 11,000 feet, they could have gotten better mileage that they did in OK.
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Old 07-06-2007, 07:04 PM   #27
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But (assuming your ICE adjusts air/fuel ratio to compensate for altitude) that power drop would result in improved ICE efficiency since the ICE is having to operate at a higher throttle setting (less pumping losses) to get the same power output.
I'm pretty sure pumping losses remain consistent at different altitudes because I read that oxygen content is proportional to altitude as well. So, if there's 15% less air density that'll help w/ aerodynamic drag, but pumping losses remain the same because the proportion of air to everything else remains the same.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 07-06-2007, 08:24 PM   #28
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radish: if you consider the sum total of the extreme mods to the car (remember: gearbox; ECU; major aero; never a cold start, & more) + driving technique + elevation + terrain + competitive nature of the owner, 100 mpg doesn't seem that much of a stretch.

Ultimately we have to take each member at his word on fill data. But based on what I've learned about CO & his car, I don't have much trouble believing it.
Living in a mountainous area myself, I believe everyone is completely overhyping the benefits of driving in mountainous terrain.

Before you can coast off a hill, you must also drive up it. There is a lot of wasted energy when climbing mountains. As well, when you go back down them, you cannot fully maximize your potential energy because if you value your life and driving record, you'll use your brakes to keep from dying.

Personally I would have thought you to be the most likely to reach the 100 mpg plateau. How are his techniques that much different from any one elses?

Metro, I believe it was you yourself who said that there is must be a maximum MPG for each car. Just look at the numbers - 274% above EPA - yours is only 108%.

I just have a hard time believing that. As I said earlier, I don't want to judge him too harshly. He has made a lot of fine improvements, and I'm glad for him. I do believe he is getting good mpg, but I think the temptation to stretch the numbers for each upgrade has to be there.
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Old 07-06-2007, 08:46 PM   #29
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Living in a mountainous area myself, I believe everyone is completely overhyping the benefits of driving in mountainous terrain.

Before you can coast off a hill, you must also drive up it. There is a lot of wasted energy when climbing mountains. As well, when you go back down them, you cannot fully maximize your potential energy because if you value your life and driving record, you'll use your brakes to keep from dying.

Personally I would have thought you to be the most likely to reach the 100 mpg plateau. How are his techniques that much different from any one elses?

Metro, I believe it was you yourself who said that there is must be a maximum MPG for each car. Just look at the numbers - 274% above EPA - yours is only 108%.

I just have a hard time believing that. As I said earlier, I don't want to judge him too harshly. He has made a lot of fine improvements, and I'm glad for him. I do believe he is getting good mpg, but I think the temptation to stretch the numbers for each upgrade has to be there.

I have to admit, the mpg figures COZX2 has given and some of the others on the top ten seem a little high, but I am willing to take the man at his word. I am interested in seeing his breakdown of mods and the FE improvements they make. It will help me decide which ones I want to do on my car so hopefully I can at least beat the EPA figures on my car.
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Old 07-06-2007, 08:52 PM   #30
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Before you can coast off a hill, you must also drive up it. There is a lot of wasted energy when climbing mountains. As well, when you go back down them, you cannot fully maximize your potential energy because if you value your life and driving record, you'll use your brakes to keep from dying.
Depends on the grade and mods. I'm guessing that CO ZX2 is setup so that he can engine off coast in gear, or N. While EOC'ing in gear is wasteful compared to out of it in terms of time, it's still using no fuel, so whatever the peak mileage is it can still be attained, just at a proportionally lower speed than it could be attained using P&G. In fact, P&G generally bites compared to long enough mountains because by using it, the car can't warm up totally and ends up running through the enriched cycle/inefficient portion of the BSFC map a significant amount of time. In fact, in all my experience, climbing mountains with steepish grades in EFI manuals generally helps because efficiency is way greater than in the flats, something like 50-100% better, and when I'm going down the other side in gear, I'm using no fuel as long as I'm above the idle fuel cut.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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