Compression ratio

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
mep
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Compression ratio

Postby mep » Mon Aug 23, 2010 10:34 pm

What compression ratios are current (F1) engines running?

A colleague told me last week that otto-engines for motorcycles can run compression ratios up to 1:13.
I thought that this would lead to high peak pressures because of the isochoric process during combustion.
There must be a point(compression ratio wise) where the peak pressure goes over the peak pressure of a diesel engine.


I think peak pressure depends on engine revolutions. Because the time for combustion will go into expansion phase of volume (piston already going back) and therefore you get more of the isobaric process (diesel like).

Edis
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Re: Compression ratio

Postby Edis » Tue Aug 24, 2010 1:30 am

I would suspect current F1 engines use compression ratios around 12-13:1. As F1 engines use very short strokes it is difficult to reach a high compression without blocking the combustion chamber and the flow around the valves.

Peak pressures are around 110 bar, passenger car diesels are around 180 bar these days and commercials diesels go as high as 200-250 bar.

With both the diesel and the spark ignition engine the piston moves during heat addition changing the volume which means the heat addition isn't fully isochoric, and they are in practice not that different when they operate at high load. At low load the diesel has a rapid pressure increase early in the combustion phase which results in a small pressure peak before the main peak. In theory this is interpreted as the Seiliger cycle with constant volume and constant pressure heat addition. The reality is something in between. Both for diesel and gasoline engines.

By the way, the racing diesels that are used on Le Mans doesn't use much higher compression ratios, 14-15:1 or something like that.

autogyro
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Re: Compression ratio

Postby autogyro » Tue Aug 24, 2010 2:52 am

Helped build a spark ignition engine for touring cars, designed to run on LPG.
It had a compression ratio of 15.5:1 and could run well at 17:1
...
Petrol is nowhere near the best ic fuel.
LPG needs no additives to prevent detonation and neither does ethanol.
You want power, just keep adding nitro to methanol, I used to wear a special wizards hat when doing that.
Last edited by Steven on Thu Aug 26, 2010 12:10 am, edited 1 time in total.
Reason: Removed ignition of a possible rant

WhiteBlue
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Re: Compression ratio

Postby WhiteBlue » Tue Aug 24, 2010 6:39 am

Dual fuel engines reach very high compression ratios as well and deliver high efficiencies. For instance you can run a diesel engine with LPG and inject a tiny amount of diesel or bio oil to start the self combustion.
Formula One's fundamental ethos is about success coming to those with the most ingenious engineering and best .............................. organization, not to those with the biggest budget. (Dave Richards)

strad
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Re: Compression ratio

Postby strad » Tue Aug 24, 2010 8:36 am

No it doesn't require additives...It requires twice as much volume in the case of alcohol and even more in the case of LPG.
One can run alcohol at extreme compression ratios but fuel mileage sucks.
I would agree that F1 engines probably fall into the 12 - 13 to 1 range...I don't think shrouding of the valves is much of a problem with the straight shot intake tracks they run..but piston top shape could play havoc with the combustion and swirl...not to mention the weight,,,you seen these pistons? there is no real piston,,just a place for a ring or two and a top.
Motorsport without danger is like cooking without salt
Sir Stirling Moss

Jersey Tom
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Re: Compression ratio

Postby Jersey Tom » Tue Aug 24, 2010 12:29 pm

Sport bikes on pump gas already run compression ratios up to 12.5:1, and I'm fairly sure race bikes are in the 14.5:1 range (though I'd have to check).

I'd have to imagine F1 is in that range. Then again engines aren't my strong point.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.

CMSMJ1
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Re: Compression ratio

Postby CMSMJ1 » Tue Aug 24, 2010 12:45 pm

You are right JT.

My race bike runs 12.5:1 and it is 21 years old..

If I could afford some new Cosworth pistons for my bike I would get a 13.5:1 ratio no problems and could then also skim the head to improve that still.

I run 98RON fuel unless I can get my hands on some BP Race 102.
IMPERATOR REX ANGLORUM

ringo
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Re: Compression ratio

Postby ringo » Tue Aug 24, 2010 7:14 pm

Jersey Tom wrote:Sport bikes on pump gas already run compression ratios up to 12.5:1, and I'm fairly sure race bikes are in the 14.5:1 range (though I'd have to check).

I'd have to imagine F1 is in that range. Then again engines aren't my strong point.

I believe the ferrari 458 italia has a compression ratio of 12.5:1 as well.
Not bad for a production car.
For Sure!!

strad
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Re: Compression ratio

Postby strad » Tue Aug 24, 2010 7:31 pm

Stock Porsche' run like 13 to 1
Motorsport without danger is like cooking without salt
Sir Stirling Moss

Agenda_Is_Incorrect
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Re: Compression ratio

Postby Agenda_Is_Incorrect » Tue Aug 24, 2010 8:23 pm

autogyro wrote:I used to wear a special wizards hat when doing that.

...
LPG is in general extracted by oil companies and even sold by them and so is ethanol in most countries that it is sold to the public. Both have problems and specially LPG has with packaging and lubrification. Coming from a country with ethanol I can also say for sure mileage is bad even with high compression, making it unusable as a replacement for oil in the current stage of biofuels. Stop saying nonsense and taking topics out of the way to promote your religion. Reported again. Moderators please fell free to edit this post after solving this topic problem.
Last edited by Steven on Thu Aug 26, 2010 12:08 am, edited 1 time in total.
Reason: Removed smell of personal offence

diosol
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Re: Compression ratio

Postby diosol » Tue Aug 24, 2010 9:32 pm

mep wrote:What compression ratios are current (F1) engines running?

A colleague told me last week that otto-engines for motorcycles can run compression ratios up to 1:13.
I thought that this would lead to high peak pressures because of the isochoric process during combustion.
There must be a point(compression ratio wise) where the peak pressure goes over the peak pressure of a diesel engine.


I think peak pressure depends on engine revolutions. Because the time for combustion will go into expansion phase of volume (piston already going back) and therefore you get more of the isobaric process (diesel like).



We run compression ratio of 16,8:1 in our engine with ordinary 95 octane gasoline. http://remmi-team.com/content/vehicles/r7/ How do you think about that?

autogyro
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Re: Compression ratio

Postby autogyro » Tue Aug 24, 2010 9:45 pm

diosol wrote:
mep wrote:What compression ratios are current (F1) engines running?

A colleague told me last week that otto-engines for motorcycles can run compression ratios up to 1:13.
I thought that this would lead to high peak pressures because of the isochoric process during combustion.
There must be a point(compression ratio wise) where the peak pressure goes over the peak pressure of a diesel engine.


I think peak pressure depends on engine revolutions. Because the time for combustion will go into expansion phase of volume (piston already going back) and therefore you get more of the isobaric process (diesel like).




We run compression ratio of 16,8:1 in our engine with ordinary 95 octane gasoline. http://remmi-team.com/content/vehicles/r7/ How do you think about that?


Superb result. Perhaps you can explain to some of the posters on here that compression ratio does not on its own define combustion chamber pressure.
Also that simplistic references to different fuels means absolutely nothing.

diosol
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Re: Compression ratio

Postby diosol » Tue Aug 24, 2010 10:41 pm

autogyro wrote:
diosol wrote:We run compression ratio of 16,8:1 in our engine with ordinary 95 octane gasoline. http://remmi-team.com/content/vehicles/r7/ How do you think about that?

Superb result. Perhaps you can explain to some of the posters on here that compression ratio does not on its own define combustion chamber pressure.
Also that simplistic references to different fuels means absolutely nothing.


http://forums.evans-tuning.com/viewtopic.php?t=136
Image

http://en.wikipedia.org/wiki/Octane_rating
Octane rating does not relate to the energy content of the fuel (see heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner.


Our engines cylinder stats:
Bore x Stroke / Volume
27,7 x 70 mm / 42 cm3

That's a quite a bit longer stroke than usually. Do any gurus know why we have do it this way?

mep
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Re: Compression ratio

Postby mep » Tue Aug 24, 2010 11:15 pm

By the way, the racing diesels that are used on Le Mans doesn't use much higher compression ratios, 14-15:1 or something like that.

Quite interesting. What is the reason for it?

Holm86
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Re: Compression ratio

Postby Holm86 » Wed Aug 25, 2010 2:34 am

Perhaps because of the very high turbo pressure??




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