Anything else whatsoever... Keep it clean though.
#20570
From fueleconomy.gov. You can have lots of fun comparing stuff, but be aware it changes a lot from year to year as they "revise" both reported MPG and even factory-original data. When I was selling my relative's '88 Caddy, I printed the comparisons side-by-side in the window, and there were lots of comments that helped the sale. I did the same thing when selling a 1990 Honda HF boasting 52 MPG stock, with the comp of a new Ford Festiva. Most people were amazed and unaware you could buy 52 MPG off the showroom floor in the late '80s, and the higher MPG made fewer emissions than the new stuff with better emissions but worse fuel consumption. Funny how that works. ;)

David
#20571
PSIG wrote: Wed Aug 09, 2017 10:58 pm Here we go off the tracks again. :roll: Aluminum is relatively irrelevant, and in the real world allows perhaps 0.5:1 additional compression, but at the same time by absorbing the heat more readily it reduces the engine output slightly. It's a draw and does not have bearing to what you're seeking. Again, engines (iron or Al) have been produced for public use, with standardized "pump gas" at compressions higher than 12:1 for over 50 years.

This sends us back to the different "compressions" and how they are used. A 7:1 and a 12:1 engine can both be manipulated to run the same fuel without detonation, as the effective compression (not just static or dynamic) can be altered. This is one of the factors that allow the 18:1 Flex engines to run 87 octane gasoline without detonation, and how the "HiPo" engines of the muscle cars could run factory 11:1+ on pump gas. Yachtsman, all the talk of static compression ratios is not of much value until you read and understand some of how it actually applies.

David
I talk of static compression by preference most people understand it, it is a simple concept, it is what it is. Dynamic compression depends on the camshaft and timing and is more complicated. It's possible that two engines with the same static compression could have very different dynamic compressions. Probably unlikely, but it is possible
The static compression ratio of an internal combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity. It is a fundamental specification for many common combustion engines.

In a piston engine, it is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.[1]

For example, a cylinder and its combustion chamber with the piston at the bottom of its stroke may contain 1000 cc of air (900 cc in the cylinder plus 100 cc in the combustion chamber). When the piston has moved up to the top of its stroke inside the cylinder, and the remaining volume inside the head or combustion chamber has been reduced to 100 cc, then the compression ratio would be proportionally described as 1000:100, or with fractional reduction, a 10:1 compression ratio.
From Wicopedia compression ratio
#20576
Petrol/Gasoline is a completely random mixture of very different molecules that just happen to distil fractionally at the same temperature range while ethanol, methane, and methanol are fluids that are exactly what the formula says which is why they act in a extremely predictable way
#20578
Yachtsman wrote: Thu Aug 10, 2017 7:00 am It's possible that two engines with the same static compression could have very different dynamic compressions. Probably unlikely, but it is possible
If you believe the highlighted portion above, you know less about engines than I thought - and that's not much.
#20580
apollard wrote: Thu Aug 10, 2017 11:23 am
Yachtsman wrote: Thu Aug 10, 2017 7:00 am It's possible that two engines with the same static compression could have very different dynamic compressions. Probably unlikely, but it is possible
If you believe the highlighted portion above, you know less about engines than I thought - and that's not much.
I didn't think it was possible, but I haven't kept abreast in the last few years.
#20581
The engineers at Oldsmobile obviously thought there was some benefit but the bean-counters put a stop to it. The bean-counters at Triumph did the same they stopped the 16 valve TR7 just because they couldn't see much benefit. At 4000 RPM there isn't much in it , but at 6500 RPM 16 valves are worth every penny
#20584
Ethanol is much cleaner burning than petrol, just burn some and see. So I thought it should logically have much lower exhaust emissions. I’ve rebuilt an old British Ford push-rod V6 to have as high compression as was possible using other Ford parts keeping costs down by buying stock parts and I'm told it's nearly done. Ethanol is much higher octane than petrol so it can burn and burn without pinking. Ethanol is of lower energy density than petrol, but when compressed to nearly twice the density 8.9 to 1 to 16.51. I think ethanol will burn with more thermodynamic efficiency making up for it’s lower energy density. It's closer to it's optimal compression than Petrol/Gasoline would be so it's got a better chance of running without knocking like a good-un. And then the effect of the oxygen in the molecule the emissions might be exceptionally low with next to no Nox and no CO at all.
#20590
Macs wrote: Thu Aug 10, 2017 3:15 pm Your control for the pressure in your cylinders, and thus the density of your fuel charge, is under your right foot.
No the energy density is down to chemistry, but as you say the quantity is under your right foot (although my uncle drove a car in his youth that had the peddles swapped around). Also I've driven cars powered by Petrol, Diesel, CNG, and Propane other people have driven cars powered by Town gas, peanut oil, or even ethanol.
Last edited by Yachtsman on Thu Aug 10, 2017 4:32 pm, edited 1 time in total.

Hi, I am trying to assign Signed values to the x-a[…]

Vr Conditioner Noise when cranking

New version 202305 don't fix the issue. Now after[…]

blitzbox

I've finally figured out why MAP and Lambda weren'[…]

Hello, I bring news!! Let me tell you that after […]

Still can't find what you're looking for?