Last edited by dinamik2t; 8th June 2012 at 17:36. Reason: straw* hat, not staw
Using the det sensor with lights makes it dead easy to shape the curve to suit the engine, you dont need a brake at all.
You can dyno load cycle the engine as fast as you like, and for the short period it may deto, in a small band of rpm - the lights go off like a Xmas tree.
Takes a bit of fiddling with sensitivity to get in the ballpark and read actual deto - not normal noise, as the det frequency is
determined by the bore diameter.
Just make sure the M8 bolt thru the Bosch sensor is tightly fixed to the head or case, with no washers to crush etc.
Data logging the sensor output against rpm is the trick way to go, but simply watching the revcounter and the lights to see where deto is happening during a pull, is easy.
Works just like the deto warning when running EngMod - see the warning and fix the excess advance before a rod comes thru your screen, your choice.
In this case we are dealing with an aircooled scenario - remember two things here, Avgas loves com to make power, and the pipe loves retard to get heat for revon power.
Whenever you have high com or lots of advance a larger % of the heat of combustion is directed out from the chamber into the finning, via mainly the ring contact with
the bore, reduce either or both and more heat ends up in the pipe, making it appear shorter due to the increased wave speed..
Thus when you are thermally limited by the finnings capability to reject heat, you must reduce the heat input by limiting the com.
This then means more heat is available in the pipe, so more power can then be made by upping the advance - just another balancing act.
Its a Catch 22 when there is high dynamic com - ie, when the engine is on the pipe,there is danger lurking, but below that point - the cylinder filling is so piss poor the only way to get good
throttle response off slow corners is to pile in plenty of advance - its safe as houses as there is very little effective com.
This engine has no powervalve so the cylinder filling efficiency comes on slowly, so you roll of the advance slowly, then pull it out quicker as the system starts to work well.
With a powervalve its the opposite - as soon as the valve starts to lift the efficiency increases dramatically, so the advance needs to be pulled out much quicker and sooner.
Any well set up race engine will love 28* below the pipe when running Avgas.
In one of the World Champ skis I did we had 35* of mid advance, as the only time it was in that band was at full throttle from a standing start.
It would jump real hard using that advance to generate cylinder pressure - but troll around on part throttle at that rpm and it would kill the engine by loosening the barrel nuts with rampant deto.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
but presumably in that situation you could get the TPS to tell the ign to back off 10 deg at less that full throttle, yes? That would save trawling round issues I assume?
I often go first warm up laps of the day quite calmly to get tyres warmed up/ cleaned off & brain in gear.
Don't you look at my accountant.
He's the only one I've got.
Yep, easy to construct a 3D map with tps in the Ignitech by doing runs at 1/4, 1/2 and 3/4 throttle.
Or use the technology properly and use the deto sensor output as well to tell the ecu to retard at any time/rpm when the deto is happening , on the fly.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
cool, but yeah one thing at a time & deto sensor is still . . .hmm, I'll have to look back & read up, car ones are virtually free. But think we needed a decent one to drive.
Don't you look at my accountant.
He's the only one I've got.
That was easy, I don't think I've bought car parts before.
oh hold on, I got a carb for my 3.3 Vax-haul Victor back in the 80s when I owned a car.
Don't you look at my accountant.
He's the only one I've got.
Well.. At least you'll definately have the beers always cold!
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monsieur Wob, thanks for the analysis!
I confess you got me confused with the ADV though. I thought the 'common' 28 to 14 degrees was for unleaded GPs. If that is the case, combined with "unleaded likes less compression-more advance", the unleaded world would need to rise the latter higher than those numbers?
It's something that I was always curious about in EngMod too: eg at max torque + 15/14* ADV, TUbMax is below 900 and it won't detonate even with 16 or 17* of ADV - while power still rises. But I stopped at 15 due to peak cyl temps rising much above those of the RS/TZ example files..
You must take into consideration the fuel being used, and how the factory engineers approached the problem.
Unleaded ( FIM that needs gloves and a respirator ) will go to 15:1 but must be run VERY rich to achieve best power with that level of com.
Leaded was run up at 19:1 in GP engines and at the end of the day the result was that the advance curves changed very little.
The big advance was in using the powerjet solenoids.
The unleaded scenario uses BIG powerjets ( 60 + ) to turn off the rich mixture past peak power.
The leaded setup was very lean at peak power, so only needed small ( 35 ) powerjets to keep the pipe temp up, over the top of the pipe.
Later of course that bastard Thiel came along and did the clever thing of PWM controlling the powerjet, thus even closer continuously matching the A/F ratio to the pipe
temp needed for max power.
Makes me sick just thinking about how clever he was, and how advanced the results became.
We are all just wankers floundering around in the mire of a mediocratic 2T wasteland - buckets.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
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