💾 Archived View for the.teabag.ninja › resources › methanol-ignition-timing captured on 2024-05-10 at 11:00:59. Gemini links have been rewritten to link to archived content
⬅️ Previous capture (2023-09-28)
-=-=-=-=-=-=-
Neville Higgins MPH 654 Page 20
John Macdonald contradicts himself in his May letter, and I quote - "Slopping methanol through the large jets needed is not conducive to economy. Doing so on a standard petrol c.r. is pointless but would require extra ignition advance, granted." This is exactly what I said, and proves that methanol IS slower burning than petrol - what on earth is the man arguing about? I think he is really sticking his neck out to tell me that he is right and I am wrong when he bases his argument on a table in Tuning for Speed which was compiled in 1948 as a general guide against my own practical experience of racing Vincents on methanol for nearly 40 years from 1961 to date, (with the exception of the 1970's when I first came to Sweden). Proof that Mac only quotes the bits that help him is on page 158 of Tuning for Speed, wherein lies the table on which he bases much of his argument. In the middle of the page below this table Irving writes quote, "The rate of burning of methanol is slow compared to petrol and for this reason requires nearly as much advance at 14:1 compression as petrol does at its max permissible compression ratio in the same engine." Exit Macdonald with his arse on fire? No, not yet, I have more heat to apply! In his next sentence Mac says, "The really serious would mix a bit of petrol in there, knock off the CR a bit and find a bit of extra advance ups the power... which is on the same page of T for S". What it ACTUALLY says in T for S follows the sentence quoted above and reads "But with blended fuels which contain a proportion of petrol and alcohol yet can be run at over 12:1 CR, the ignition point may be perhaps 4 deg later". NOTE: the same CR and less advance - which is exactly the opposite of what Mac claims it says!!!
While building The Heap during 1959 and 1960 I read up all I could on tuning and fuels -including Tuning for Speed, and a number of chemical treatises which confirmed that methanol is slower burning than petrol - though I can't give you any references after more than 40 years. I set the C.R. at 12.5 and the ignition at 33 to 34 deg - exactly as recommended in T for S. I bought a couple of gallons of M100 "dope" from Hartley of Ariel fame down in London, as this was reckoned to be THE stuff for speed at that time. Pump petrol was then less than 5 shillings a gallon, and M100 cost £1 a gallon, which was very expensive to me. I ran it for my first two meetings and it went well - then I found I could buy straight Newton's methanol for 6 shillings a gallon in Birmingham - so I bought 5 gal and mixed it 50/50 with M100. I could detect no decrease in performance, so when the M100 ran out I tried pure Newton's; again there was no decrease in performance. Next I found I could buy straight meth as an industrial solvent in Coventry for 4 shillings a gal. Still the same performance, so I used it right through all my racing in England in the 1960s.
During this time I gradually pushed the ignition setting up to 37 deg and went faster and faster; more confirmation that meth is slow burning. In the 1980s and 1990s in Sweden, I ran classic road races due to the absence of sprints, and after pushing the C.R. to the mechanical max of 13.7 I have run 38 and 40 deg of advance, again on straight meth. My instinct, and my "feel" for what I call "a happy motor" told me I should not go beyond 40 deg and with no loss in performance I now run 38 or 39 deg. Shooting holes in Mac's theories again - I run exactly the same settings for a 30 min road race as for a quarter sprint! Further confirmation of the correctness of my settings comes not only from the performance (which no other classic in Sweden can live with), but also from spectators who come up to me in the paddock at almost every meeting to say "Your motor sounds beeeoootiful out there - it never misses a beat" and "We can always tell when you are coming round, your exhaust is a deep, powerful, booming sound, quite different from anything else on the track".
The only thing I have altered (apart from a big fuel tank) when going from sprint to road race is to increase the throttle cutaway. I ran 4.5 slides for sprints, which is very rich, to get the snap throttle response essential for a good wheelspin start. In racing this caused erratic running in long part throttle corners which threatened to have me off many times. I increased cutaway progressively to 8.5 which gave me steady even running from 2500 rpm upwards on part throttle in long fast corners. When running The Heap at Ramsey Sprint I was lazy and left the 8.5 slides in, and noted that the engine tended to bog down on take off and would not spin the rear wheel; nonetheless, I still had enough torque to lift the front end for 30 yards in spite of lying absolutely flat on the tank.
Mac is talking more nonsense without knowing the facts when discussing my blown dragster. At the 1999 International the consensus seemed to be that it sounded good, and it was running straight alky (methanol) on an equivalent C.R. of 14.2 and the same 38 deg ignition advance. Furthermore, far from being on the point of detonation at 441 yards as Mac suggests, it ran the same settings for a kilometer sprint, when it was still accelerating hard at 175 mph over the finish line. And since Mac will probably want to argue about the C.R. as well, I will tell you now that the correct way to calculate the equivalent compression ratio of a blown motor is to multiply the piston C.R. by the square root of the blower ratio. The engine C.R. is 9:1 (measured) and the blower runs 20 psi overpressure which is approx 1.5 atmospheres. Thus the blower pressure is 1 atm inlet and 2.5 atm out (absolute) giving a pressure ratio of 2.5. 9 times root 2.5 gives 14.2 equivalent ratio.
7o be continued...
---------------