The higher the compression ratio, the more likely you need higher octane fuel. You can overcome that neccessity with water injection, however, which lowers the temprature and at the same time makes a more complete burn because the fuel droplets surround the water droplets, being lighter; and when they burn, the water absorbs some of the energy and becomes steam very rapidly which makes the remaining unburned fuel droplets even smaller, so they burn faster and the burn completes before the flamewall gets to the top of the piston and through it, theoreticallyTo understand more clearly, picture a log. It takes it a loong time to burn, like overnight, for instance, in a Jotul stove. Now picture some wood shavings. They are not only easier to ignite, they burn quite fast by comparison. The gasoline gets "atomized" either by a carburetor or fuel injectors. The finer the droplets, the better the burn. Weber makes fine carbs that will cause the fuel to extract more power out of the same engine because the fuel comes out in such a fine mist. Sometimes it is so much more power that it is noticeable when you hit the gas. The engine will use less fuel, also, because more of what it gets, gets burned before the exhaust valve begins to open. Beetle engines came from the factory with about a 7.9:1 C/R. They can use 87 octane. If I were to up that compression in my engine to 10.5 or more, I would either have to use premium or add water injection. I choose the latter because I get more performance and nearly double my mileage from about 31 - 32 to about 58, give or take; plus, the engine stays cleaner; and unless you add an aftermarket filter on a Beetle, that's important, because they have no filter and I used to change my oil every 1500 miles. That wasn't so expensive, because Beetles only use 3 qts. of oil. Just a little more than a Nighthawk.. Actually, what Kyle said below is essentially the same thing; I didn't notice he wrote it after you asked the question (lol). And Kyle - I know of a chap who replaced the pistons in his Ford Focus with hi comp - 12.7s - and added water injection. That's all he did, and it increased his power (don't know how much, but a lot; no dyno) and his mileage went from 25 mpg to 50. This, on regular 87 gas. Kinda like NOS without the risk of blowin' yer engine...
Stanley ________________________________ From: Javier Garcia <[email protected]> To: [email protected] Sent: Tuesday, March 17, 2009 10:31:00 AM Subject: [Nighthawk Lovers] Re: Gasoline, octane and oil Stanley, I'm a little bit confused... in your first message it seems to me you don't agree in using high octane gasoline... in the second, you talked about engines damages due to the use of low octane gasoline... can clarify? I'm not really an expert, so I get lost very easily. Thanks, Javier. On Tue, Mar 17, 2009 at 11:11 AM, Kyle Munz <[email protected]> wrote: I used to run into the same problem with my turbo cars. The higher the boost the higher the octane rating you needed since it effectively ups the compression. Most ppl understand octane meanings backwards. It actually means it's less likely to ignite, which is good if you're running high compression, or high boost. With higher gas prices I understand people wanting to put the cheap stuff in, but like Stanley says, newer cars will retard the timing when they detect knock, which means they burn more fuel anyways, so you didn't save as much money as you would have liked. One of the benefits of ethanol is a very high octane rating, so you could run really high compression or really high boost, and thus get more power, however this just isn't feasible for road cars now matter how much the corn lobby thinks it is. Long and short of it is, just put in what the manufacturer suggests, if the engine was designed for lower octane then put that in the tank. If you want to put "the good stuff" in your tank, then go to a name brand station, such as chevron/texaco, exxon/mobile, or shell and stay away from the discount dealers. This applies no matter what octane you decide to buy. -Kyle On Tue, Mar 17, 2009 at 10:47 AM, stanley/ Randolph <[email protected]> wrote: If you know the research about octane and flamewalls and compression ratios, you would have a different attitude about that. Low octane fuel will demolish a high comp engine. I have taken apart Porsche engines they were putting in Beetle vans, with the rings all cracked and melted into their landings from using low octane for their compression ratio. And this despite the decal by the gas tank stating a minimum of 92 octane!!! This engine was still running, but I have seen engines with holes in the heads, the pistons, one which was ruined beyond repair with the hole outside of the valve insert. It is not good if you use low octane in a high comp engine. The flame wall is meeting the piston as it comes up, and when the heated wall of fire hits the piston and you hear the knock, back off, or you will ruin your engine. The engines today have knock sensors sending data to the computer to retard the timing when the flamewall gets too close to the piston crown. When timing was only a mechanically actuated centrifugal advance, one couldn't actually retard it, so the only thing one could do is back off the gas, or go around with permanently retarded timing, which defeats the purpose of higher compression: greater engine efficiency and/or more power. An old wrench gave me an engine for taking it out of this van he bought cheap and that's what I found when I took it apart. Happy to say, though, bottom end was excellent. Nice thing about those engines - is it was not too expensive to replace those pistons and cylinders. I had me a new engine for the labor and $80.00 for new set of P&C and a valve job with new exhaust valves. Gasket set was the second most expensive item: $29.00; for regular Beetle engines the gasket set was only $4.00, and a new set of P&C was less than $40.00 for Brazilian Cima/Mahles or a Jap brand name escapes me), both of which were close to German quality. The only safe thing to do when rebuilding the Porsche engines is to lower the C/R, because people think, it's just a VW (van/microbus). It doesn't really need premium gas. Until, of course, it's usually too late... Stanley ________________________________ From: Creative Residential Designs <[email protected]> To: [email protected] Sent: Tuesday, March 17, 2009 7:37:45 AM Subject: [Nighthawk Lovers] Re: Gasoline, octane and oil Try telling that to my '69 GTO, Dick. It will NOT run on anything else...period. It doesn't care what you or I think about premium gas, it will ping and knock and carry on until I feed it the best gas there is. (Texaco or Shell premium ONLY). I just read a study on gas on the 'net as well. Interesting how abrasive low-end fuels are to an engine. I'll try and locate it again. Apparently it's one of those "you are what you eat" situations. HotrodMamma. ----- Original Message ----- From: Dick MacInnes To: [email protected] Sent: Monday, March 16, 2009 9:10 PM Subject: [Nighthawk Lovers] Re: Gasoline, octane and oil The only place to get the proper service Manuel is Helm. Inc And premium gasoline is a waste of money, I don't care what anyone has told you. Dick --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en -~----------~----~----~----~------~----~------~--~---
