Just wondering what are some of the compression ratios you have used, heard of, etc.....
Gas
Diesel
Jet
Gas
Diesel
Jet
compression ratios
- Thread starter mjoekingz28
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My 70 elcamino had a 300hp 350. Stock those had 10.25-1. My quad is 11.5-1...i think our new can am is 12-1isg but ill have to double check
My pickup is 21-1
My pickup is 21-1
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gathermewool
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Originally Posted By: Chris142
My pickup is 21-1
My pickup is 21-1
My vehicles;
92 Caprice 6.6 - 10.5:1
Ram - 17.2:1
Navigator - 9.8:1
92 Caprice 6.6 - 10.5:1
Ram - 17.2:1
Navigator - 9.8:1
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my current diesel: 16.5:1 and 85 bhp/litre
my previous diesel 18:1 and 58 bhp/litre
my old citroen diesel (van engine) 22:1 and 36 bhp/litre
my 155 TS 8v gas: 10:1 and 71.5 bhp/litre
my previous diesel 18:1 and 58 bhp/litre
my old citroen diesel (van engine) 22:1 and 36 bhp/litre
my 155 TS 8v gas: 10:1 and 71.5 bhp/litre
I suspect top fuel dragcars are way up there to achieve the power they do.
Is detonation, heat or metallurgy (strength) the holdback of high CRs? Or what?
Is detonation, heat or metallurgy (strength) the holdback of high CRs? Or what?
Mazda Skyactiv engine in the 2015 Mazda3 has a 13:1 compression ratio.
It has 14:1 in Europe.
Mazda is working on the Skyactiv generation 2 engine which will use homogeneous charge compression ignition. 18:1 compression and no spark plugs.
It has 14:1 in Europe.
Mazda is working on the Skyactiv generation 2 engine which will use homogeneous charge compression ignition. 18:1 compression and no spark plugs.
Is it just the crankshaft and piston tops that determine this, and also the head portion of the combustion chamber?
Originally Posted By: mjoekingz28
Is it just the crankshaft and piston tops that determine this, and also the head portion of the combustion chamber?
(bore x stroke)+ combustion chamber volume devided by combustion chamber volume.
My '96 Maxima has 10:1 and lots of ign. adv. Premium fuel is recommended for good reason.
Is it just the crankshaft and piston tops that determine this, and also the head portion of the combustion chamber?
(bore x stroke)+ combustion chamber volume devided by combustion chamber volume.
My '96 Maxima has 10:1 and lots of ign. adv. Premium fuel is recommended for good reason.
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Originally Posted By: mjoekingz28
I suspect top fuel dragcars are way up there to achieve the power they do.
Is detonation, heat or metallurgy (strength) the holdback of high CRs? Or what?
Top Fuelers make the true power they do by the use of nitro methane fuel. If you compare them to the top alcohol cars, they make over 2x the power. The formula for power is not just compression.
As far as what holds compression ratio back....yes it is detonation. Low octane fuels of today do not allow for high compression engines like they used to. Yes the modern ECU's will retard timing if the knock sensor picks up a ping. But those of us with older carbed engines have to stick with around 10 to 1 compression ratios on average. Using aluminum heads helps as it dissipates heat better and you avoid hot spots in the heads that can cause pinging. Some engine/head designs are more forgiving than others.
As for engine compressions I have now
1970 LT1 Small Block Chevy in a 1970 Nova had 11.5:1
1986 Monte Carlo SS 5.0 "HO" has 9.5:1
2006 Scion TC 2.4L has 9.6:1
2011 Triumph Speedmaster 865cc has 9.2:1
I suspect top fuel dragcars are way up there to achieve the power they do.
Is detonation, heat or metallurgy (strength) the holdback of high CRs? Or what?
Top Fuelers make the true power they do by the use of nitro methane fuel. If you compare them to the top alcohol cars, they make over 2x the power. The formula for power is not just compression.
As far as what holds compression ratio back....yes it is detonation. Low octane fuels of today do not allow for high compression engines like they used to. Yes the modern ECU's will retard timing if the knock sensor picks up a ping. But those of us with older carbed engines have to stick with around 10 to 1 compression ratios on average. Using aluminum heads helps as it dissipates heat better and you avoid hot spots in the heads that can cause pinging. Some engine/head designs are more forgiving than others.
As for engine compressions I have now
1970 LT1 Small Block Chevy in a 1970 Nova had 11.5:1
1986 Monte Carlo SS 5.0 "HO" has 9.5:1
2006 Scion TC 2.4L has 9.6:1
2011 Triumph Speedmaster 865cc has 9.2:1
Originally Posted By: mjoekingz28
I suspect top fuel dragcars are way up there to achieve the power they do.
Is detonation, heat or metallurgy (strength) the holdback of high CRs? Or what?
Top fuel engines have a low CR of around 7. They make all their power because of the massive amount if fuel and air they're able to pump into the cylinder.
I suspect top fuel dragcars are way up there to achieve the power they do.
Is detonation, heat or metallurgy (strength) the holdback of high CRs? Or what?
Top fuel engines have a low CR of around 7. They make all their power because of the massive amount if fuel and air they're able to pump into the cylinder.
Top fuel dragsters consume between 12 and 22.75 US gal of fuel during warmup, burnout, staging, and the quarter-mile run. They inject so much fuel that when they lose ignition, the hydraulic pressure will jack a head right off the block.
They use nitro-methane fuel and run a 14-71* blower at 56-74 PSI boost.
* Equivalent to a General Motors 2 stroke diesel with 14 cylinders of 71 cu in each.
They use nitro-methane fuel and run a 14-71* blower at 56-74 PSI boost.
* Equivalent to a General Motors 2 stroke diesel with 14 cylinders of 71 cu in each.
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I haven't CC'd my head but the book number is 9:1 for my Rocco, 67bhp/litre
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My old 5.0L Mustang was 8.8:1 stock IIRC
My old Town Car (also a 302 was around 8.5:1 stock
My M5 was 11:1
The '06 Charger is 10.5:1
The '14 Charger is 10.9:1
The '02 Expedition is 9.2:1
My old Town Car (also a 302 was around 8.5:1 stock
My M5 was 11:1
The '06 Charger is 10.5:1
The '14 Charger is 10.9:1
The '02 Expedition is 9.2:1
My 1949 Buick with a 248 has a whopping 6.6:1
My KTM 380 EXC (2 stroke enduro bike) has an "effective" compression ratio of 7.4 to 1 with the exhaust valve retracted, in the high RPM, high HP position.
The "effective" compression ratio is about 8.9 to 1 with the exhaust power valve in the lower position. The low RPM, higher torque position.
In either position, there is also a small hole in the side of the cylinder bore, to bleed off compression for easier starting. This calibrated leak reduces compression during low speed operation. Has no effect at higher RPM.
Even with an "effective" CR of 7.4 to 1, it pings like crazy unless high octane fuel is used.
Also, it makes about 55HP at the wheel at about 8500RPM. Not at all bad for a low compression, 380cc (23 cubic inch) engine.
The "effective" compression ratio is about 8.9 to 1 with the exhaust power valve in the lower position. The low RPM, higher torque position.
In either position, there is also a small hole in the side of the cylinder bore, to bleed off compression for easier starting. This calibrated leak reduces compression during low speed operation. Has no effect at higher RPM.
Even with an "effective" CR of 7.4 to 1, it pings like crazy unless high octane fuel is used.
Also, it makes about 55HP at the wheel at about 8500RPM. Not at all bad for a low compression, 380cc (23 cubic inch) engine.
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