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Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests


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  #41  
Old 02-09-2016, 12:06:42 PM
Nickel City fab Nickel City fab is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

That Atkinson design is just plain fascinating if only because its so different. I do wonder if you could instrument one by gluing strain gages along the length of the cylinder, with enough data channels to create a sort of indicator card. That engine is fascinating, I wonder with modern materials and methods...
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  #42  
Old 02-09-2016, 06:27:24 PM
imotorhead64
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

It seems Toyota is all over the Atkinson cycle... too bad they didn't give miller any credit.

http://news.pickuptrucks.com/2015/01...son-cycle.html
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  #43  
Old 02-09-2016, 08:04:18 PM
Amax Amax is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
Originally Posted by imotorhead64 View Post
It seems Toyota is all over the Atkinson cycle... too bad they didn't give miller any credit.

http://news.pickuptrucks.com/2015/01...son-cycle.html
This raises an interesting point.

All modern 'Atkinson' engines use valve timing to synthesize a shorter intake stroke. Suck in less and there is less residual pressure at BDC of the power stroke.

But this is not the same as that fancy configuration of rocker shafts illustrated a few posts back.

It would be interesting to see a 'real' Atkinson engine made with today's low-friction bearings and lightweight materials. Just as a science experiment; I have no delusions that something like that would ever be manufactured in volume.

The implied question is what defines a true Atkinson engine?
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  #44  
Old 02-09-2016, 09:37:27 PM
imotorhead64
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

I think this guy has a good explanation for that....

https://www.youtube.com/watch?v=Ac7G7xOG2Ag

more seriously.... the idea of applying a differential compression / expansion stroke seems to be nothing new... When it is done with valve timing some people call it the Charon cycle.







Last edited by imotorhead64; 02-09-2016 at 09:51:34 PM.
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  #45  
Old 02-09-2016, 10:45:33 PM
imotorhead64
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests





It appears the true Atkinson was hard to classify... because the piston made 4 strokes for every one revolution of the flywheel.



---------- Post added at 10:45:33 PM ---------- Previous post was at 09:57:49 PM ----------

Quote:
It would be interesting to see a 'real' Atkinson engine made with today's low-friction bearings and lightweight materials. Just as a science experiment; I have no delusions that something like that would ever be manufactured in volume.

The implied question is what defines a true Atkinson engine?
Hello AMAX, I believe there are several participants in the Shell eco marathon that have use true Atkinson cycle engines (I would classify a true Atkinson as having a compression / expansion differential and an over center crank) . It seems most participants are using the modified version of valve timing to create the differential. There must be something to it because many of the cars get 2000-3000 MPG.

I believe the engine on the left is an Atkinson cycle with an over center crank.

http://energyblog.nationalgeographic...soline-engine/

here is a honda version

http://www.roadandtrack.com/new-cars...tkinson-cycle/

http://www.bikesales.com.au/editoria...chnology-26295

Last edited by imotorhead64; 02-10-2016 at 08:31:29 AM.
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  #46  
Old 02-10-2016, 05:45:14 AM
Wayne Timms Wayne Timms is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
Originally Posted by imotorhead64 View Post
It seems Toyota is all over the Atkinson cycle... too bad they didn't give miller any credit.

Hi,

I am fairly confident that Toyota's are running to the Charon cycle, not Atkinson. I don't know why Toyota refer to it being the Atkinson cycle.

Part of the Charon cycle is the variable valve timing depending on the power required, this is not an Atkinson cycle trait.

Photo below of the Charon in my collection, from the late 1890s. I can't find any difference between the Charon cycle and the cycle Toyota run today.

Regards,
Wayne

www.bluefuel-whitesmoke.com
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  #47  
Old 02-10-2016, 09:45:24 AM
Bill Hazzard Bill Hazzard is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

I think it is more of a synthetic Atkinson cycle. It's not real but it gives the end result of more expansion.

I am not familiar with the Charon, does your engine hold the intake open for part of the compression stroke?

My grandfather built a small block Chevy in the 1970's which worked the same way the Toyota is now. He had a custom cam ground and had 12:1 pistons in it and he got 30 MPG in a 4 door Impala.
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  #48  
Old 02-10-2016, 11:14:16 AM
imotorhead64
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
My grandfather built a small block Chevy in the 1970's which worked the same way the Toyota is now. He had a custom cam ground and had 12:1 pistons in it and he got 30 MPG in a 4 door Impala.
Isky sold them as Mile-A-More cams... Crower also sold them as an economy kit which included new pistons. I once spoke to Bruce Crower about them and he told me it was useless to just replace the cam without replacing the cam without the 12-14:1 pistons. The engines had about a 9:1 compression ratio with the cams installed. He referred to it as a Miller cam although Miller used a supercharger. I agree with Wayne T... the Charon Cycle is the correct description for what Toyota is doing.

https://en.wikipedia.org/wiki/Miller_cycle

Last edited by imotorhead64; 02-10-2016 at 11:28:44 AM.
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  #49  
Old 02-10-2016, 01:26:35 PM
Bill Hazzard Bill Hazzard is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
Originally Posted by imotorhead64 View Post
Isky sold them as Mile-A-More cams... Crower also sold them as an economy kit which included new pistons. I once spoke to Bruce Crower about them and he told me it was useless to just replace the cam without replacing the cam without the 12-14:1 pistons. The engines had about a 9:1 compression ratio with the cams installed. He referred to it as a Miller cam although Miller used a supercharger. I agree with Wayne T... the Charon Cycle is the correct description for what Toyota is doing.

https://en.wikipedia.org/wiki/Miller_cycle
I didn't know that they had kits available but he did have a Crower cam in it.
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  #50  
Old 02-11-2016, 09:09:52 AM
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lenoir lenoir is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

[QUOTE=Wayne Timms;1252848]Hi,

. I can't find any difference between the Charon cycle and the cycle Toyota run today.


wayne, bonjour

on the Charon engine; excess gasses expelled on compression stroke are stored on a huge tube coil located on the engine base for re-use on the next cycle


how Toyota manage to do it ou modern engine ???
amicalement jp

Lenoir
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  #51  
Old 02-11-2016, 10:44:54 AM
Bill Hazzard Bill Hazzard is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

[QUOTE=lenoir;1253238]
Quote:
Originally Posted by Wayne Timms View Post

wayne, bonjour

on the Charon engine; excess gasses expelled on compression stroke are stored on a huge tube coil located on the engine base for re-use on the next cycle


how Toyota manage to do it ou modern engine ???
amicalement jp

Lenoir

The Toyota is a multi cylinder engine so the reservoir is the intake manifold.
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  #52  
Old 02-11-2016, 01:51:27 PM
imotorhead64
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Another way to limit the compression is to close the intake valve early, this requires a valve spring capable of holding the valve shut while the piston pulls a vacuum on the cylinder. It seems to me this could be a more efficient method since moving the air fuel in and out of the cylinder requires some energy output... any guess why one method is better than the other?
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  #53  
Old 02-11-2016, 01:54:44 PM
Bill Hazzard Bill Hazzard is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
Originally Posted by imotorhead64 View Post
Another way to limit the compression is to close the intake valve early, this requires a valve spring capable of holding the valve shut while the piston pulls a vacuum on the cylinder. It seems to me this could be a more efficient method since moving the air fuel in and out of the cylinder requires some energy output... any guess why one method is better than the other?
Throttle governed Otto's work that way and some Jacobsons and I am sure others as well. Both ways take energy, pulling a vacuum takes energy too. No engine moves air and fuel in and out of the cylinder. It would be air going one way through the engine when the fuel is governed or exhaust only when the exhaust valve is held open.
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  #54  
Old 02-11-2016, 02:13:28 PM
Amax Amax is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
Originally Posted by imotorhead64 View Post
Isky sold them as Mile-A-More cams... Crower also sold them as an economy kit which included new pistons. I once spoke to Bruce Crower about them and he told me it was useless to just replace the cam without replacing the cam without the 12-14:1 pistons. The engines had about a 9:1 compression ratio with the cams installed. He referred to it as a Miller cam although Miller used a supercharger. I agree with Wayne T... the Charon Cycle is the correct description for what Toyota is doing.

https://en.wikipedia.org/wiki/Miller_cycle
I had once wondered if a poor man's 'Atkinson' cycle (OK, now we know it is really a Charon cycle) could be cobbled together simply by changing the rocker arm ratios on a SBC, since different rocker arm ratios are available from the aftermarket. Simply use the shortest intake and the longest exhaust ratios available.

After seeing yours and Bill H's posts, I realize that to get much benefit the compression ratio would also need to be looked at. Still, I wonder what advantage, however small, would result from a rocker-only swap to create a more economical engine. (Yes, assuming OK valve to piston clearance.)
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  #55  
Old 02-11-2016, 02:13:57 PM
JSWithers JSWithers is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
Originally Posted by Bill Hazzard View Post
Throttle governed Otto's work that way and some Jacobsons and I am sure others as well. Both ways take energy, pulling a vacuum takes energy too. No engine moves air and fuel in and out of the cylinder. It would be air going one way through the engine when the fuel is governed or exhaust only when the exhaust valve is held open.
My experience with the Oto and the Jacobson throttle governor is with a 50hp Otto we have and a 14hp Jacobson we use to have. Both throttled by the governor changing the intake rocker arm stroke. More "lift" the faster it ran, less "lift" the slower it ran. They didn't have a butterfly in the intake to control speed like more traditional throttle governors.
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  #56  
Old 02-11-2016, 02:25:19 PM
Amax Amax is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
Originally Posted by imotorhead64 View Post
It seems Toyota is all over the Atkinson cycle... too bad they didn't give miller any credit.

http://news.pickuptrucks.com/2015/01...son-cycle.html
That article is incredibly badly written. Clearly the author knew little about the subject matter and was incapable of lucidly describing what happens.
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  #57  
Old 02-11-2016, 02:48:18 PM
JSWithers JSWithers is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

I should add that the 175 Otto at Coolspring is the same as our 50.
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  #58  
Old 02-11-2016, 03:00:50 PM
imotorhead64
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
My experience with the Oto and the Jacobson throttle governor is with a 50hp Otto we have and a 14hp Jacobson we use to have. Both throttled by the governor changing the intake rocker arm stroke. More "lift" the faster it ran, less "lift" the slower it ran. They didn't have a butterfly in the intake to control speed like more traditional throttle governors.
I'm assuming that for full power the intake valve would be open the entire stroke?

The interesting thing is Otto cycle engines have a variable peak cylinder pressure according to how much air is or is not let into the cylinder. At partial loads a throttle governed engine sees much less peak pressure. Have you ever measure the peak pressure at partial throttle?

Quote:
I had once wondered if a poor man's 'Atkinson' cycle (OK, now we know it is really a Charon cycle) could be cobbled together simply by changing the rocker arm ratios on a SBC, since different rocker arm ratios are available from the aftermarket. Simply use the shortest intake and the longest exhaust ratios available.

After seeing yours and Bill H's posts, I realize that to get much benefit the compression ratio would also need to be looked at. Still, I wonder what advantage, however small, would result from a rocker-only swap to create a more economical engine. (Yes, assuming OK valve to piston clearance.)
I think the for purposes of efficiency the combustion space must be made smaller to increase the expansion ratio.

I'm not sure how much difference it makes to ether close the valve early (on the intake stroke) or close the valve late (on the compression stroke) but a partial opening of a valve would eat up more energy. I think for purposes of efficiency a valve needs to be open or closed fully and quickly. Btw Hicks engine have adjustable intake rockers.

There are some folks proposing engines that throttle by means of the intake valve closure / timing and not a butterfly. When throttling by butterfly the air / fuel is moving in and out of the cylinder thus consuming more power. A new old idea...

http://www.mechadyne-int.com/vva-ref...sses-si-engine
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  #59  
Old 02-11-2016, 04:12:51 PM
Amax Amax is offline
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
Originally Posted by imotorhead64 View Post

I'm not sure how much difference it makes to ether close the valve early (on the intake stroke) or close the valve late (on the compression stroke) but a partial opening of a valve would eat up more energy. I think for purposes of efficiency a valve needs to be open or closed fully and quickly. Btw Hicks engine have adjustable intake rockers.

There are some folks proposing engines that throttle by means of the intake valve closure / timing and not a butterfly. When throttling by butterfly the air / fuel is moving in and out of the cylinder thus consuming more power. A new old idea...

http://www.mechadyne-int.com/vva-ref...sses-si-engine
First of all, I acknowledge that my labeling of my hare-brained idea 'poor man's Atkinson' is insulting to Atkinson and poor men alike.

From you explanation, I am confused if the net affect (in terms of economy) would be better, worse or the same.

If the intake rocker ratio is 1.5:1 and the exhaust rocker ratio is 1.7:1, then for a given cam profile the intake will not be opening as far compared to the exhaust. (I realize that I am oversimplifying the oversimplification.)

What would this accomplish?

And yes, if it was such a screaming great idea, it would already be in use.

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  #60  
Old 02-11-2016, 08:22:53 PM
imotorhead64
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Default Re: Historical Engine Article Series I - Early Crossley Slide Valve Engine Tests

Quote:
From you explanation, I am confused if the net affect (in terms of economy) would be better, worse or the same.
Hi Amax, for purposes of increasing efficiency using the Atkinson / Charon cycle a large expansion ratio is required... The advantage comes when very high compression pistons are used because they create a small combustion space. However if a full intake / compression stroke is used (Otto cycle) the peak pressure the 14:1 pistons will make is too high for common gasoline so the valve is ether closed early or late to create ( in effect) a short compression stoke with lower peak pressure and a longer expansion stroke. Does that make sense?
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