jmac wrote:
I can't say 100% for sure, but personally I'd be worried about 79mm and more boost - enough to get you the 280bhp goal. Is there any chance you could sell them to somebody with a NA datsun engine project that is high revving/output. I'd honestly personally prefer going 76.5 or 77mm if absolutely no option. If you can tune it very safe, rich under boost and not too much timing (richer than you would go for another turbo setup with the same boost but stronger bore walls), water injection, then it's probably doable, but not ideal.

NO engine in the world will stand up too long with detonation (or preignition, which is usually actually worse, esp in a boosted setup, due to the sheer amount of air/fuel to be burning too early (as the piston is still rising in the bore, which causes the burn temperature to go through the roof. Generally there's a small gap between the piston top and where the flame actually reaches (it's only a few thou) so it protects the piston crown a little. (it's why tight quench helps prevent detonation - flame can't pass through the small gap - it's why some old kerosene home heaters have a wire mesh over the flame to stop it reaching any higher).. Anyway, if you experience any severe shocks (detonation) or just massive pressure (more related to pre-ignition) then it can compromise that layer, and the heat the piston is exposed to is higher still.

SO obviously - no engine will handle det/pre-ign for long at all (and every little tiny bit of damage just stacks up on top of each other) - but even if you avoid that, it might still be pushing it.

Don't get me wrong, the datto engine is darn strong, esp for when it was made. And it's a smaller engine and 2 valve/pushrod valvetrain. Effectively a turbo would have to work harder to produce 280bhp out of an a15 than it would out of an sr20 (esp since it could do it at less boost, so less heating up of the intake charge. So that means (usually) more heat in the intake charge, but you also lose a little more power to exhaust pumping losses, and the pumping losses scenario leads to more heat trapped/lingering between the exhaust valve and the turbo exhaust housing, so more heat the exhaust valve has to deal with. It sort of goes around in circles, with these issues all affecting each other.

Sometimes you have a 'win' here and there with boosted projects. For example - supercharged setups - if you mounted a blower on a bench, and then spun it with an electric motor (and a restrictor on the blower outlet that is adjustable, you could spin it to any rpm you liked, and then adjust the outlet restrictor size until the supercharger is making X amount of boost (lets say 10psi). Now you could calculate how much power was required by the electric motor to achieve that. So then you could work out how much power the supercharger is stealing in order to produce 10psi at (for example) 6000rpm. And you'd have the answer. Except it wouldn't be the real answer. Here is where things get interesting - essentially that 'force' of pressurised air being shoved into the cylinder - well it actually creates some 'push' on the piston going down in the bore. So 'some' of the superchargers energy cost is actually paid back. The difference isn't like night and day, but it's one of those weird ones that hardly anyone might think about (and for the record, I didn't come up with this myself, it was a result of a discussion on the jyturbo list, where one of the posters there was - no kidding - a rocket scientist)

What is the situation in Koskela with available fuel and octane ratings? Recently in Aus we've been seeing the introduction of ethanol blended into petrol (which increases fuel consumption, and isn't profitable/viable without government subsidies or brazil where wages are lower on average,so there's a cheap workforce) - anyway they do it because of 'climate change' - basically to get votes).. OK so the regulr unleaded is being phased out to be replaced with e10 - 10% ethanol.

That's bad, but on the flip side, there's also (in probably 20-30 places around the country, but growing slowly) e85 - which is 85% ehtanol and the rest regular fuel. It doesn't require as much fuel as methanol does, but it has a _lot_ of the same sort of cooling effect that methanol does. So effectively you have to increase flow by about 40% or so (vs 100% or more for methanol) - which increases fuel consumption even at part throttle. It's still reasonable enough that a car can be street driven with a fuel like E85 (methanol goes beyond that0 but you'll get the chance to run more boost safely (or the same boost but maybe not needing water injection or a bigger intercooler)

People here are using E85 in various racing categories, and the power it makes is higher than when they previously ran on special high octane petroleum/gasoline based race fuel - and it only takes them literally the first few corners of the start of the next race to se just how big the improvements are. If you can get something like that fuel, certainly it'd be a good option

If

A14force wrote:
99 octane?!!!! Holy hell, I though 98 ultimate was a good thing. Is your fuel rated by it's MON, RON, or AKI number?

nick_m wrote:
When I was over in oz last I saw shell had a ethanol blended 100 octane (RON) Even rang Shell when I got home to check they weren't supplying it here (or going too)
seems every one gets better fuel than us Bart!