Maverick Hybrid Climbed Mt Washington Today

[EriktheBikeMan]

Doing this always seemed penny wise and pound foolish. Brakes are cheap, engines are expensive.

I suspect crashing because you cooked your brakes instead of using engine braking is most expensive

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[Phimosis]

A quick dig into the specs of the 2.5L "Atkinson" 4 cylinder motor shows that it has a compression ratio of 13.0 versus 9.3 for the EB. With that high a compression ratio, engine braking is bound to be pretty helpful. Higher compression ratio basically equates to a greater amount of braking and the higher the engine RPM, the more braking as well. Easily illustrated by downshifting and keeping your foot off the gas pedal.

Incidentally, diesel engines typically run even higher compression ratios, and thus have superior engine braking. Also, they often are equipped with the "jake brake" which utilizes exhaust valve opening techniques to release build up pressure in the cylinders that have reached the top of the compression stroke, thereby preventing that compressed gas (air) from returning its energy to the crankshaft - when they use this brake, you hear it in the loud "BRRRAAAAAPPPP" that trucks make when using the compression braking to slow down.

Because of the loud sound, many municipalities have ordinances prohibiting the use of compression braking within city limits.

Atkinson cycle engines do not have superior engine braking. The Atkinson cycle engine has reduced energy density and reduced mean effective cylinder pressures compared to a similar displacement Otto cycle engine, despite having a higher compression ratio, due to the late closing of the intake valves, which occurs after bottom dead center, which decreases the duration of the compression stroke.

Most of the difference in compression ratio. Between the hydrid and the EB is because the EB has a turbo, not because the hybrid uses an Atkinson cycle engine.

Diesel engines have no compression braking, unless they design a compression brake into the engine. Gas engines use a throttle plate to restrict air flow, to create a stoichiometric air fuel ratio. Trying to draw 1 atm of vacuum against the closed throttle plate is what causes the resistance that we call engine braking. Diesel engines do need throttle plates, because they do not need a stoichiometric air fuel ratio to get optimal combustion. So a diesel engine will let the air freely pump through the engine going downhill and freewheel, without providing engine braking.

 

[Tom 71 Maverick 24]

Atkinson cycle engines do not have superior engine braking. The Atkinson cycle engine has reduced energy density and reduced mean effective cylinder pressures compared to a similar displacement Otto cycle engine, despite having a higher compression ratio, due to the late closing of the intake valves, which occurs after bottom dead center, which decreases the duration of the compression stroke.

Most of the difference in compression ratio. Between the hydrid and the EB is because the EB has a turbo, not because the hybrid uses an Atkinson cycle engine.

Diesel engines have no compression braking, unless they design a compression brake into the engine. Gas engines use a throttle plate to restrict air flow, to create a stoichiometric air fuel ratio. Trying to draw 1 atm of vacuum against the closed throttle plate is what causes the resistance that we call engine braking. Diesel engines do need throttle plates, because they do not need a stoichiometric air fuel ratio to get optimal combustion. So a diesel engine will let the air freely pump through the engine going downhill and freewheel, without providing engine braking.

interesting information. Although there aren't a lot of normally-aspirated engines with compression as high as 13:1, so I don't think the 9.3 of the EB is necessarily a characteristic of a turbo engine. A lot of the older engines were in the 8 to 9.5 range, with higher ratios generally related to higher performance engines that needed premium fuel.

Anyway, I'll have to ponder the increased compression ratio against the intake valves being open beyond BDC, because that would imply a reduction in compression ratio. Then again, combustion chamber size, a few other variables involved. Must read more.

I really thought that they didn't make diesels without the "jake brake". But that's another story for another time.

But that's a different situation - if I were driving a diesel down a steep hill and downshifted, there is engine braking that takes place without applying the "jake" (BRRRRRRRRRRRP). Same with any engine, though my poor 3 cylinder Escape didn't seem to offer as much of a slowing effect as other vehicles I've had. That can't just be friction from all the moving parts, can it?

 

[Phimosis]

interesting information. Although there aren't a lot of normally-aspirated engines with compression as high as 13:1, so I don't think the 9.3 of the EB is necessarily a characteristic of a turbo engine. A lot of the older engines were in the 8 to 9.5 range, with higher ratios generally related to higher performance engines that needed premium fuel.

Anyway, I'll have to ponder the increased compression ratio against the intake valves being open beyond BDC, because that would imply a reduction in compression ratio. Then again, combustion chamber size, a few other variables involved. Must read more.

I really thought that they didn't make diesels without the "jake brake". But that's another story for another time.

But that's a different situation - if I were driving a diesel down a steep hill and downshifted, there is engine braking that takes place without applying the "jake" (BRRRRRRRRRRRP). Same with any engine, though my poor 3 cylinder Escape didn't seem to offer as much of a slowing effect as other vehicles I've had. That can't just be friction from all the moving parts, can it?

Ford mustang is 12:1 compression, Corvette Z06 is 12.5:1. The 911 GT3RS is 13.3:1. The 2015 Ferrari 458, the last year they were N/A, they had 14.0:1 compression ratio. Then in 2016 when they went turbo and renamed it the 488, the compression ratio dropped to 9.4:1, same as the good old ecoboost.

 

[Grabber Rick]

There are two Mt. Washingtons that battle it out for cold and wind - New Hampshire and Washington - which was it ? and don't get me started on Maine etc.

Can't forget Mt. Washington in Pittsburgh Pa.

 

[Tom 71 Maverick 24]

Ford mustang is 12:1 compression, Corvette Z06 is 12.5:1. The 911 GT3RS is 13.3:1. The 2015 Ferrari 458, the last year they were N/A, they had 14.0:1 compression ratio. Then in 2016 when they went turbo and renamed it the 488, the compression ratio dropped to 9.4:1, same as the good old ecoboost.

But those are all performance cars. 302, 351, small block Ford engines of yesteryear shared compression ratios of 8.0:1 to 9.5, with the exception of performance oriented versions which ran something on the order of 10.5. The 2-valve 4.6 L was 9.0, and the 4 valve was only 8.5:1. The 5.4 2 valve was 9.0 and the 3 valve was 9.8. Granted, old-school ignition and carburation weren't as precise as today's engine controls, so preignition was a bigger concern. But the 5.4 was injected, as was at least the more recent 4.6 V8 engines.

Godzilla, Ford's 7.3L truck engine, has a 10.5 compression ratio. Along with a lot of durability-related parts. Old school but rugged (and given the things you have to go through with diesel, a pretty good alternative for moderate towing and motor homes).

For the record, I believe that engine controls and manufacturing techniques are superior to a lot of those older engines. Still, high compression generally has been found more in performance oriented engines.

 

[Tom 71 Maverick 24]

Can't forget Mt. Washington in Pittsburgh Pa.

As a Browns fan, I don't think I'm allowed to go there.

 

[bobbyd454]

My wife and I checked Mt Washington off our bucket list Mav did fine, the brakes definitely got hot lol.

I guess you have to be a native to know what Mt. Washington is. We have a Mt. Washington, but it is a city in Ky.

 

[TomD]

My wife and I checked Mt Washington off our bucket list Mav did fine, the brakes definitely got hot lol.

How did the transmission handle it? Did you need to put the transmission in the lower gear mode. You mentioned that the brakes got hot; were you riding them all the way down?

 

[Edge Haley]

Discovered this on a X-country trip down a 9,550 foot mountain in Wyoming...extremely steep mountain route for 90 miles. Put the Hybrid in cruise control at around 40mph and the engine was continually down and up shifting all the way down the mountain staying at 40 MPH...with me rarely having to touch the brakes.

Went thru the Porsche Driving School last year in Carson, Calif....Instructors all taught engine braking due to far safer control in turns...all 911's were PDK (Automatic) transmissions...also taught cruise control as safer control in high altitudes.

 

[Old Fart]

My wife and I checked Mt Washington off our bucket list Mav did fine, the brakes definitely got hot lol.

You are a year late, did that last summer.

 

[Phimosis]

But those are all performance cars. 302, 351, small block Ford engines of yesteryear shared compression ratios of 8.0:1 to 9.5, with the exception of performance oriented versions which ran something on the order of 10.5. The 2-valve 4.6 L was 9.0, and the 4 valve was only 8.5:1. The 5.4 2 valve was 9.0 and the 3 valve was 9.8. Granted, old-school ignition and carburation weren't as precise as today's engine controls, so preignition was a bigger concern. But the 5.4 was injected, as was at least the more recent 4.6 V8 engines.

Godzilla, Ford's 7.3L truck engine, has a 10.5 compression ratio. Along with a lot of durability-related parts. Old school but rugged (and given the things you have to go through with diesel, a pretty good alternative for moderate towing and motor homes).

For the record, I believe that engine controls and manufacturing techniques are superior to a lot of those older engines. Still, high compression generally has been found more in performance oriented engines.

I simply used N/A Otto cycle examples I could think of off the top of my head, because there are only a handful of them left.

So after a little googling… a non-turbo Subaru Ascent, their largest SUV, uses 12.5:1 compression. Blasphemy, that’s sports car territory!? The higher trim versions use the same engine with a turbo and gets a 10.6:1 compression. Again, the point is that turbo engines have to have a lower compression ratio than N/A engines to keep the cylinder pressure out of the danger zone, lest you grenade the engine.

To refute your point about all of my examples being performance car engines, the Mustang gets a 12.0:1 compression ratio. The F-150 with 5.0 liter V8 gets a …. You guessed it, 12.0:1 compression ratio.

Just because a carbureted 1974 Ford LTD has a 6.0:1 compression ratio, doesn’t mean it has any relevance to the conversation about the compression ratios in 2022-2024 mavericks. Ancient tech couldn’t support modern compression ratios.

One last little tidbit that you’re probably not thinking about is direct injection. Because DI blasts fuel into a gaseous fog at insanely high pressures, that drops the charge temperature, which prevents detonation, which allows for higher compression ratios. That is just one of the many advances that have allowed for higher compression ratios in the last 40 years, but it is the most recent and has had the most dramatic bump in CR.

 

[HeyBales]

I always wondered if the 2.5 compression ratio of 13 was merely the mathed figure, not taking into account the valve open timing difference.
Wasn't one of the aspects of the Atkinson engine less work due to less compression due to the valve timing?

 

[Phimosis]

I always wondered if the 2.5 compression ratio of 13 was merely the mathed figure, not taking into account the valve open timing difference.
Wasn't one of the aspects of the Atkinson engine less work due to less compression due to the valve timing?

Yes, the compression ratio is just a mathematical formula of bore area X stroke length divided by combustion chamber volume.

The late valve closing on an Atkinson cycle engine doesn’t change the compression ratio (a math formula), but it is causing incomplete compression of the air charge, which lowers cylinder pressures, which allows them to bump the compression ratio up some without running into detonation. If they changed the cam shafts and the engine map and made this back into an Otto cycle engine, they would have to lower the compression ratio down to 12.0-12.5:1 to prevent detonation.

 

[Dad]

I took my Ecoboost maverick up to the Southgate Meadows Trailhead on Mt Shasta, 7,800 ft elevation, towing a 1,900 lb load. It didn’t break a sweat going up or down. The closest town and staging point, Mt Shasta, is at 3,400 ft. That means 4,400 feet of decent in 20 or so miles. No squishy brake pedal. No fires.

Glad to hear it. I'm of the thinking that overheating is much less of a problem with disc brakes than the older drums.

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