Dry Lakes Racers Australia

in the interest of seeing ever increasing speeds go visit www.racecarbook.com

well worth the read ..I have both bob szabo's books ...though be aware his target is big block mechanical fuel injection with supercharger drag racing stuff ( that's his passion) , where there is excellent practical tuning info.....lots of general knowledge ...but very little for those with pentroof dohc engines and turbos.....you will learn a lot of stuff from these books ......also look up spud miller on google for some excellent lower % nitro /alky info
Good post there Ronnie
cheers

sorta had you in mind when i posted Garry, ,, yeah, ive had these books for sometime now and have found the information very helpfull. As you say, Bobs passion is hemi big blocks, mechanical fuel injection and drag racing, but, using a little nouse one can apply the information given to whatever their particular engine combination is, ,,,,

One thing Bob doesn't really drive home is that methanol (or nitro) increases exhaust mass flow over intake air mass flow........what goes in must come out. In my experience back to back methanol vs petrol dyno runs; methanol has significantly lowered the RPM turbo boost threshold and simply have simply given the turbine more push because of the extra total exhaust molecules.

The extra exhaust mass flow from methanol may have been highlighted and worked well in my particular case (turbo's on the too biggish side), never-the-less many have said methanol doesn't work well with small motors. From what I have seen it's easy to understand how exhaust tuning would be seriously affected by the extra exhaust mass and different exhaust gas temperatures.

[quote="dplecko"]One thing Bob doesn't really drive home is that methanol (or nitro) increases exhaust mass flow over intake air mass flow........what goes in must come out. In my experience back to back methanol vs petrol dyno runs; methanol has significantly lowered the RPM turbo boost threshold and simply have simply given the turbine more push because of the extra total exhaust molecules.

The extra exhaust mass flow from methanol may have been highlighted and worked well in my particular case (turbo's on the too biggish side), never-the-less many have said methanol doesn't work well with small motors. From what I have seen it's easy to understand how exhaust tuning would be seriously affected by the extra exhaust mass and different exhaust gas temperatures.




Yup,, back in the eighties i ran a RaJay turbo on a 1170cc Z1 Kawasaki based motor at the drags,, everyone said (thay still do today) that dump pipe shape and size made no performance difference,, we made and experimeted with a cuppla designs that made no real difference, untill, we started leaning the thing out, dump pipe design really came into play then, like 2-3 tenths improvement in times, noticable, we were kids having a go and monited a/f by me mate standing at the traps and observing how "orange/yellow" the headers were, lol,, so i have no real data to show for it,, btw, we only ever torched one head,,
all well tuned Methanol motors have a "note" all their own, and nitro motors are louder, all based on the reason you mention,, ,

The exhaust gas temperature will be different with methanol too. It runs cooler.

With two strokes that has a big affect on the power band. The cooler temperature effectively increases the speed of sound inside the expansion chamber.

The net effect of this is that the engine will rev higher on methanol than petrol with the same expansion chamber. So if you want to keep your redline and powerband in the same range, a longer chamber is required.

Well I finally got around to starting up Mr Whippy on nitro/methanol/ turbo starting at 30% nitro / 70% alky ...lots of trial and error on the fuel maps ...after stuffing around for a while it finally started .... got the misses to do a youtube or 3 if any one is interested go here

https://www.youtube.com/watch?v=M8ZbV51xg6U

https://www.youtube.com/watch?v=gAv5Ko_kEaw

https://www.youtube.com/watch?v=I-1Vo3viqTY

Well at least it starts haha off to the dyno soon see if it lives through that

cheers

I remember the "1st start" feeling well, including the "pop"
Well done Gary,,CYA soon

Gary, how were the nitro fumes at 30%, make your eyes water,lol, ,,,,

Mine were watering just listening to it , sure i could smell it too

Hope all goes well on the dyno Gary

LOL yes the fumes make your eyes water with 30% and the smell is wonderful..........just wish the starting was easier ......will add maybe 5% acetone as this is supposed to help in that regard.....also fattened up in the very low rpm ranges and added a touch more timing.
Hope all racers are on top of their plans to race soon

3%acetone will do it in hot weather,, mine at 3 is a bit hesident on cold mornings, but will bang into life almost straight away when the temperature is above 23,24%,,, me thinks a larger % for your motor will help control detonation, ya gunna need it when boost kicks in, ,:twisted: ,,

Many years ago, before the VIC wallopers stuffed it, I was in the pits with a mate at the Mildura HD drags, I noticed a beautiful Nitro Panhead had what looked like alloy wedges 'tween the frame backbone and each head, I asked the rider,,WTF ? , yep he replied,,they ARE wedges,,it's the only way we can keep the heads on the engine during startup,,,,,
Be careful Gary,,,,