Stuff below is opinion/experience/educated guess. it's not locked in stone, just my best 'take' on things at the moment.

The invisible flame is no small concern. It doesn't happen every day, but I've seen a number of fires during pitstops (on tv) - and they don't realise it's on fire, until they just barely catch the heat haze 'ripples' in the air above the car. One time i recall the first sign the pit crew had was the driver flailing about (not injured thanks to safety gear/apparel)

Although it is higher octane, that alone isn't the whole story. It's octane rating aside, the latent heat of vapourisation (heat sucked out of the surrounding gases to enable a change of state into a gas) sucks enough heat out to prevent detonation in and of itself in a lot of cases. The fact it requires about twice as much fuel for any given amount of air (vs petroleum based fuels), there's a hell of a lot of it in there, and the cooling effect is far greater than would otherwise seem likely.


Aside from the higher compression/boost that could be safely used, the cooling effect of the methanol also means that the air/fuel that finally gets into the cylinder is cooler and denser - so even without boost, there's relatively more cylinder filling. (it's still about the same VE, but it's denser charge at that given VE)

The cooling potential itself is significant enough that drag racing engines can use it to help keep the engine cool enough to complete the drag race itself with a grout filled block and possibly no coolant at all.

In champ car (and prior to that, I think indycar, basically before the 'split', not sure what IRL use any more or the state of play of either of those categories, I haven't watched it in years) they aren't allowed intercoolers, but they are allowed an additional injector in the plenum area of the intake manifold - this extra injector sprays methanol during peak boost situations. It's placement further away from the cylinders means it cools the charge entering the plenum, i.e. it has more time to do it's job than the injectors nearer each intake port. And it does it very effectively.


Rather than going any of the options - how about a middle ground option - run standard (albeit high octane) pump fuel (which won't break the bank) and one boost setting, and for the competition days, run methanol injection (basically just 'water injection' but run more methanol - 50% or so) so that it prevents detonation and allows more boost safely. The good thing about methanol is that over and above the need to run twice as much (compared to petrol) - you can go way richer still and it'll still run well, so you have a lot more cooling effect available, a bigger safety net.

You could of course run straight methanol as the aux spray, but it can only go so far as an anti-detonant, after all it can still burn, so eventually you'd reach a point where it'd see pre-ignition or detonation, no matter how much methanol you added. On the other hand, straight water isn't flammable, so you can add more and more and suppress detonation. Of course you eventually get to the point that there's so much water and (due to higher and higher boost that the extra water allows) heat, you eventually reach a stalemate as more water (assuming it doesn't first lead to misfires or incomplete combustion) and boost don't return any further gains. In general the ww2 era testing of water injection and various ratios of water and methanol, they concluded (in big military aircraft engines that produced huge outputs) that more methanol would tend to allow the greatest peak power (when you ramp it up, and the boost with it). The straight water wouldn't make the same power, but it would allow the highest boost/compression safely without any danger of engine damage. These engines were routinely tested to destruction to see just where the limits were. There's some decent info (albeit not the easiest to interpret if you aren't an engineer, and I'm certainly not!) on the 'NACA' archives website:

naca archives

NACA was basically the predecessor to NASA and the reports/papers on that site contain the bulk of their developments

They tested water injection rates ranging from about 1:10 (ratio vs normal fuel delivery rate - i.e for every 10 litres of petrol, 1 litre of water sprayed in) right up to 1:1 and beyond (for the record, as far as I can recall, they actually cited ratios by _mass_ not volume, so I'm approximating there).

One thing they did note was that at higher levels of water (i.e. closer to 1:1) - with big bores, hard cylinder sleeves and hard rings, all of which see a little more blowby - well they found that the oil was contaminated by water to the extent that it'd have to be replaced frequently.. This should never come up on a street care with more conservative amounts of water added, but worth a note.

Last little tid-bit from the naca stuff - which is a cool thing for most of us. What they _did_ find was that the use of small amounts of water - let's say 1:5 or so, then all the cooling/safety that was previously done by running a very rich mixture under boost, well that could be replaced with water, and the fuel leaned off (relatively speaking) with no loss in power or protection. In other words - if an engine running 10psi needed an a/f ratio of 11:1 to stay safe, and at 11:1 it was using 3 litres of fuel per minute, well if you added sufficient water, you could drop the fuel back to 12.5:1 (2.64 litres per minute down from 3) and get the same power, same safe running. You'd never go down to true stoich in practice as it would start to drop power. Then again, you _could_ do it if economy with a certain output was needed for whatever reason. Water is of course practically free, so it can pay off to consider it. Purely for trivia sake, the rate of water to add would be about 0.29 litres (since it's by mass, and fuel generally has a lower specific gravity than water)

You can 'sorta' get nitromethane, it's used in some model engines (usually in a mix of nitro, methanol, and some small amt of trans fluid or similar). It's easily the gateway to big power. Since it releases oxygen to be burnt during the power stroke, it can supply it's own air, and practically run off itself alone. That is a situation that allows you to run ridiculously rich and get more and more power..The trouble ith nitromethane is that it's far more susceptible to knocking and detonation (and even pre-ignition). Yes the potential is there, but you actually have to run lower compression with nitro (assuming you actually use a decent amount of it) than you would with any pump fuel and way way way lower comp than straight methanol would like. This can't be overstated as it means you'd have to theoretically build and engine to get the right result, which would be very ordinary if it was later run on petrol or methanol. blown alcohol drag engines can run over 11:1 compression and massive amounts of boost. Top fuel, which run nitro (and it's percentage is down a fair bit these days to try and keep them from going faster/harder than the tyres can endure) tend to run anywhere from 6-7.5:1 compression depending on the weather and god knows how many other factors.

Aside from it's volatility, nitro (since it's releasing oxygen during the process, and a hell of a lot is in there) takes a long time to burn (compared to other fuels). This means to get the 'right' amount of push on the piston, they need to run a hell of a lot of ignition advance - 50 degrees isn't a lot by top fuel standards, more in some cases. You'll see that some of it's still burning as it leaves the exhaust pipes on dragsters. So much of it is burning, that if you watch them, and the engine drops a cylinder, the thrust this still burning fuel produces is enough to push the cars slightly sideways to the 'weak' side if one of these 'jets' drops out. Not enough to launch the car, but a considerable enough amount. The reason I add this is that the zoomie pipes on dragsters are there for that reason. It's also the case that since the gases are still burning and expanding, traditional extractors won't work too well, they only end up clogging up the exit path relatively speaking. Which brings it full circle. this still burning fuel will be a massive issue to the turbine of some turbocharged application. The exhaust wheel will be exposed to far more heat energy. Probably enough to wreck them with extended use. Obviously it would depend just how much nitromethane was going to be used, but I'd doubt that any current turbo would last more than a race weekend (if that) on 80% nitro (not that there is actually a category for such high amts of nitro and turbos).

If you were just spraying something like 10% nitro (vs total petrol usage) for drag racing (and the rest of the combo could handle it) I'd not be too worried about the turbo surviving it.

If I was to pay the full amount, would you be able to hold it for a couple of weeks whilst I organise freight? I'm in Mlelbourne.

I have to say up front I haven't played with hitachi diffs a lot, but I've got some experience with diffs from ford/holden/valiant stuff. You absolutely can't re-use a crush tube. If you do, it'll tend to want to destroy the bearings. Ironically, or not, the same thing can happen even with a new crush tube, though in this case it won't be from overtightening, it'll more likely be from insufficient tensioning of the pinion nut. The forces on diff internals are massive, under power, the pinion literally tries to force the crownwheel away from it and spreads the housing. They are a tapered bearing, and just a fraction too little preload, and they'll allow a slight angularity and focus all the stress/load on one tiny section of the rollers, and fail. With the right clearance (in this case so tight that it's actually preload, or negative clearance) the load is spread across the entire tapered roller and it can handle very high loads in contrast.

If you can't get a new crush tube, the other option would be to get a _solid_ spacer made up so that it no longer crushed at all, and the pinion bearing preload was instead set by the thickness of the solid spacer. That is a pain to machine up (though you could use one main spacer, then a couple of shims a few thou thick to get you right on the money) but ultimately there's no guesswork or reliance on the crush tube to collapse just enough to get it right (which they generally do well, but anyhoo) With the use of a set thickness shim, you also don't have to worry about getting the pinion nut torque perfect, generally you get it as tight as you physically can (and you'll likely need to mount it in a vice or jig to hold it in place, and use a breaker bar with a metre long pipe slid over it to get enough leverage. Of course if you happen to be a weightlifter or something, that might have to be revised.

What carb(s) are you running and are they mandatory? Aside from the overall engine power curve, throttle response is strongly linked to carb setup. In general looking at stuff like more sensitive boosters (if applicable) and tailoring the idle/off idle and acc pump circuits for response (where you no longer care whatsoever about fuel consumption) can make a hell of a difference. The other big deal is ignition. If you aren't restricted to points, a good hei setup, even with the same timing, can produce noticeable improvements out of a corner.

Actually I think you raise a good point. An auto _does_ cost more power, albeit at lower road speeds, when it's 'on' the convertor - i.e. launch. At those conditions, maximum difference between engine rpm and transmission input shaft rpm, the convertor produces a lot of heat. And that's why it requires the big trans oil cooler, and why they can overheat during burnouts.

It's also why it's recommended to avoid high stall convertors for any sort of towing work, as they'll be operating at a point of higher slippage much of the time.

Still you're likely only talking about 25% of it going to heat at lower rpm, and by the time the convertor reaches lockup (i.e. fluid lockup, where engine and trans input shaft are nearly at the same rpms, as opposed to a true lockup with a lockup convertor which engages a clutch and provides true 100% lockup) you're still only talking in the order of about 5-10% max.

It probably won't affect anyone here, but generally it's also therefore the case that stall speed of a convertor shouldn't be near, let alone higher than rpms at cruise speeds or the convertor will always be slipping.

You also end up with differences of opinion about how chassis dynos are setup. A few of the people on another forum are adamant about this in particular with regard to summernats horsepower heroes comps. Their reasoning (and I won't go into all the detail, this is a long enough post anyway) is that no tyres one cares to name will hook up anything like 2000bhp off the line even in a properly setup rear on a production based cars, so the ramp up rates on the dynos for the summernats have to be done to take all that into account, but they don't tend to blow a lot of tyres from the massive tie-down/weighdown measures that are/should have to be taken to get enough traction for such a dyno pull. I'm not suggesting for an instant that the big hp motors don't produce a _hell_ of a lot of power, but I'd be much keener to see what they did on an engine dyno. I realise the summernats is about cars, not just engines and there's less spectacle/entertainment in an engine dyno shootout. Still I think about these things :)

What I'm going to say will sound controversial, but bear with me, I can offer a little evidence. Most of the losses assosciated with chassis dyno readings isn't the drivetrain, it's the dyno mechanism itself.

As proof - if you really lose even remotely close to 25% through the drivetrain, the microscopically small amount of heat soak 1.5-2 litres of gearbox and diff oil would mean that the gears would be glowing red hot in around 15 seconds, and that's on a small setup like the dattos. On something with 6-700 bhp it'd be over in less than a handful of seconds. There's just no way they'd survive if there really was such a power loss.

Sure there _are_ losses, but it's probably on the order of under 3-4% at absolute worst.

I know that sounds a little weird, but it's nonetheless inescapable, as the drivetraiins would disintegrate on the dyno from the heat produced otherwise (as they would if you towed a load that required full throttle up a hill for more than a minute.

Now eventually on circuit racers you get to a point where cooling of the gearbox or diff oil is relevant, but they are producing far far more power, and little airflow (not that it'd do much without heat sinks) under them due to aerrodynamic gear on the car limiting said flow, and they are also on the power with little break in between

EVen having said that, it's well short of what engine cooling is required which deals admittedly with a greater amount of heat energy, but if you look at it and try and scale it down to the amount of power allegedly lost through drivetrains, there's no way known they could possibly be losing that much.

I dare say there'd be more lost through the _tyres_ than the geartrain itself, though it's still predominantly the dyno itself (and that's not a criticism of the dyno either, in case I'm sounding that way). Which is essentially why any serious race effort still goes to the trouble of engine dynos (and likely as not tries to simulate underbonnet conditions in the dyno cell, right down to any effect low pressure areas under the car might have on the exhaust exit point at high speed.) as well as on track testing/monitoring.

The engine vs chassis dyno figures generally 'differ' by around 20-30% but that's not necessarily indicative of a drvietrain loss.

I haven't had any contact with them in a number of years, but I've had 9" diffs shorted/splined by Keysborough Diffs in the past. they weren't the cheapest (not the most expensive either) but I've had the diffs outlast engines and bodyshells. I've had mixed results elsewhere (which I won't name) but can recommend the work they do at Keysborough Diffs. I actually live the other side of Melbourne, so it's quite a hike to even go there, probably passing a dozen other closer options on the way there.

Unless they've changed in a major way in the last 5 years, I'd trust them with any driveline work.

Hello everyone, I've picked up a 1200 coupe not so long back. I'm not a basketball player, but I am large enough that with the stock seats all the way back I can only just fit my legs under and operate the pedals.

Obviously altering the seat (and possibly a smaller steering wheel) will see to the leg room issues, but the other issue is that even slightly slumped, my head is touching the rooflining.

What I'm after is feedback from people with either of the cobra seats metioned. Specifically - with the most compact rail/attachment being put in place (or just securing direct to the floor (done properly of course)) - do the cobra vintage or classic actually end up putting the driver closer to the ground.

I intend to go out to revolution next week with a tape measure, but I'd kind of like to find out if they are lower by enough of a margin that the driver would instantly notice it, not just barely noticeable.

Any other thoughts as to seat options that would put my backside closer to the asphalt? If at all possible i'd want something not entirely 'race only' in appearance - hence the look of the cobras mentions would be a much more appealing option.

Thankyou for any insight you can share.

For pure trivia's sake - a weber on that particular short necked, abrupt turning inlet are actually noticeably worse than twin SUs -for both power and economy. The sharp turns lead to fuel drop out, and the mixture distribution (within the cylinder, not necessarily the overall from cylinder to cylinder) is atrocious.

The mini uses siamesed intake ports - 1 &2 share a single intake port, and 3&4 share the second intake port. So even with twin webers, they don't get one carb throat per cylinder, and sonic tuning of the intake is pretty much out.

If you can afford it, the widest powerband (arguably a little less peak power - probably less than 2% vs a large single carb with decent plenum - which is an intake manifold which doesn't actually exist for these) for an a series datto would be with twin webers, and one carb throat per cylinder.

My personal take would be that if you can only afford (and i can't afford either right now!) two carb throats per engine for whatever reason, you might as well go for the SU type carbs. They'd drop less output against a single weber than they'd drop against twin webers, and they tend to be easier to get the part throttle efficiency decent (provided you spend time finding the right needle profile)

Probably wouldn't also hurt to mention that webers can be fitted with chokes to make them responsive and have the best possible output (for that whole combo of head, cam exhaust etc) on even a stock 1200 engine. The problem of course is that the webers themselves and the intake, and the setup time/costs mean that it can be darn expensive, and it's hard to justify unless you spend extra money on stuff like a more sporty cam profile, headwork etc - so that then the money spent buying and sorting the webers produces a larger output. Cost to benefit ratio and all that.

I should probably mention that I'm far more familiar with minis than dattos, but that is slowly changing (in no small part due to this forum)

John McKenzie

ballpark figure you'd be chasing?? (I really have nfi what the going rate is, and wouldn't want to make an offer that was unintentionally an insult. I bought a coupe recently for a song, but it was sheer luck, I have a feeling that that price would be nowhere near a fair price for yours) further - do you still have the original struts by any chance?