Gar or Bruce..exotic fuel AFR question.

[Bruce Plecan]

I wouldn't count on it.
No sure about how much But, your going to probably also be changeing the timing.  Nitro needs like a 2 day head start on ignition.  Then again a 2% charge might not matter much, but I wouldn't asume anything.  If max HP is at 12.5 then I would also get a EGT there, and be damn sure to get best atmospheric data available, and use all that when tring even a *short* load of Nitro.

Folks really tend to forget gasoline is about like playing with dynamite, and when you get to Nitrometh, nitro propane, hydrazine, and this other stuff your in the world of nuclear devises.   
Watch a top fuel or funny car in early season testing, them boys been at it for years, and start way down on the base cals  when cranking up a new combo / season.

Personally, after having the EGT, AFR, and climate stuff, I'd probably start out with 4 degrees les timing, and at least 5% rich on fuel, and short shift it, and see what things are like (plug wise).
Then see what the AFR read, and start tuning from there, again, that's what I'd do, no quantie, or waranty implied ot expressed, racin inheitanty dangerous yada yada
Bruce    


  ----- Original Message ----- 
  From: Phil Rickard 
  To: gmecm at diy-efi.org 
  Sent: Tuesday, September 26, 2000 1:31 PM
  Subject: ATTN: Gar or Bruce..exotic fuel AFR question.


  Hello gentlemen. I have a brief but confusing question. As you may have read in the past, I'm building a 377 SBC, suited to burn a 2%-3% mixture of Nitromethane and 100 octane racing fuel from VP and my question is related as to what I can expect to see for AFR readings, respectively. I have done some research on the subject and have found out that Nitro is approx. 49.6% oxygen by weight/volume and that increased fuel flow is expected, however, what I'm not sure on, is how to determine if I need to concentrate on the already known 12.5 AFR as a tuning benchmark for proper combustion at WOT? This engine is N/A.

  The problem of fuel separation has been addressed and is not a factor here, as there are additives to add to the racing fuel to keep the nitro reliably suspended for up to six months; I've found a source for that.

  Is my reasoning correct to think that I can tune the engine conventionally on 100 octane race fuel to start out with, so that I give myself a benchmark of correct AFR, then switch to the exotic fuel and see where the addition of it places my AFR in relation to the original tuning curve? I would think that given the relatively small amount of nitro actually in the fuel, that I could still tune the engine's AFR as if it were gasoline only. Afterall, nitro is essentially adding an oxygenant to the fuel the same as N.O.S. would...correct? I don't know if the other by-products of nitro would effect this. Any ideas?

  Thanks in advance.

  Regards....

  Phil Rickard- Engine builder/Tuner, Les Stanford-Pirate Racing Corvette C5R......Formerly with L.P.E.
  vettebuilder at skyenet.net
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