PORTING (making sense of it all)

[Grant Monkhouse]

If you were to fill the "bowl" of a 9.0-1 comp rotor with water and measured that volume of water in ml. Then filled a 7.5-1 comp rotor with water and measured that would they be the same?? That\'s how I always though of as comp ratios, where piston or rotor.

[HaywardRotary]

And not one swear word or derogatory comment posted :Ladys-man

Good job! This is a family site! LOL:spank

[Grant Monkhouse]

And not one swear word or derogatory comment posted :Ladys-man

:Ladys-man:Grrr lol

[HaywardRotary]

If you were to fill the "bowl" of a 9.0-1 comp rotor with water and measured that volume of water in ml. Then filled a 7.5-1 comp rotor with water and measured that would they be the same?? That\'s how I always though of as comp ratios, where piston or rotor.

Displacement in the rotor in each case is the same but the total volume of the whole chamber is not.
The amount of air/liquid that is pulled in and pushed out is the same, BUT if you were to fill the combustion inlet area when at maximum expansion on the inlet phase with a fluid you would get more fluid into the lower compression engine, but after it is filled it would only physically push out the same total capacity as the higher compression engine.

[PGiljevic]

If you were to fill the "bowl" of a 9.0-1 comp rotor with water and measured that volume of water in ml. Then filled a 7.5-1 comp rotor with water and measured that would they be the same?? That\'s how I always though of as comp ratios, where piston or rotor.

But you have to empty the bowl and it is not just poured out like you do down the sink, it is "pumped out" and this is the clearance volume at top dead center, this is a dead area where nothing much happens, it is very hard to clear and in fact never really is very well at if ever.

WORKING Capacity is BDC volume - TDC volume

If you could amazingly increase power by lowering compression ratio, everyone would do it, you only ever can if you are limited by knock limitation of fuel ........... simple.

This is why full race methanol set ups typically do not care to waste time with "low compression" rotor sets, it is counter productive as the fuel is not a limiting factor

See the 13B S5 block I listed making 917bhp on an engine dyno with only 32psi boost pressure used

[Grant Monkhouse]

How about nitro then? They need huge compression to ignite the fuel:D to make the power

[Erdin]

How about nitro then? They need huge compression to ignite the fuel:D to make the power

they use a methanol mix grant as rich as 2:4 ratio!

[PGiljevic]

they use a methanol mix grant as rich as 2:4 ratio!

RC two stroke is no different, I do allot of development work on that as a hobby lol.

I use 40% Nitro and 60% Methanol (bit of oil added!) anyway. If you use too high a compression ratio you can and DO detonate the engine! Too little compression and the performance is just not there (slower on straights and on dyno).

AFR simple, you measure it the same as you do petrol, I mad a jig to test RC motors and I tune them to 12.7:1 in petrol AFR scale (same as Lambda) the numbers are not important here it is just what has "meaning to the tuner" so anyway with RC 2 strokes they make maximum power around that 0.85 lambda region, but its a balance of head temperature and how the AFR changes over a tank load of fuel in a race etc.

The points are as you increase compression ratio power goes up, but even on 40% Nitro and Methanol as a base fuel it is still prone to detonation small scale or large same thermodynamic principles apply .

[HaywardRotary]

they use a methanol mix grant as rich as 2:4 ratio!

Nitomethane you mean, a liquid form of TNT.
They run around 3 to air fuel ratio.
Also they are supercharged. approx 8000 hp
They used to run 100% but gradually to slow the cars down Methanol was introdeiced 1st at 5% and now its 15% so the cars were developed more in the clutch department and now are quicker than ever, so much so that they dont run 1/4 of a mile anymore in the states, they now run 300 meters.

[Ed_RX7parts]

:WaveBye..........

[HaywardRotary]

RC two stroke is no different, I do allot of development work on that as a hobby lol.

I use 40% Nitro and 60% Methanol (bit of oil added!) anyway. If you use too high a compression ratio you can and DO detonate the engine! Too little compression and the performance is just not there (slower on straights and on dyno).

AFR simple, you measure it the same as you do petrol, I mad a jig to test RC motors and I tune them to 12.7:1 in petrol AFR scale (same as Lambda) the numbers are not important here it is just what has "meaning to the tuner" so anyway with RC 2 strokes they make maximum power around that 0.85 lambda region, but its a balance of head temperature and how the AFR changes over a tank load of fuel in a race etc.

The points are as you increase compression ratio power goes up, but even on 40% Nitro and Methanol as a base fuel it is still prone to detonation small scale or large same thermodynamic principles apply .

But not turbocharged Peter so boost does not come into account here. I also play with these engines and even have 2 rotary engines. 4.9cc and 1.2hp.

[PGiljevic]

Nitomethane you mean, a liquid form of TNT.
They run around 3 to air fuel ratio.
Also they are supercharged. approx 8000 hp
They used to run 100% but gradually to slow the cars down Methanol was introdeiced 1st at 5% and now its 15% so the cars were developed more in the clutch department and now are quicker than ever, so much so that they dont run 1/4 of a mile anymore in the states, they now run 300 meters.

weak! they should run them over a mile!

[HaywardRotary]

weak! they should run them over a mile!

When Scott Kallitta was killed they changed things, the thing is they are still running the same terminal speeds at 300 meters now as they were at 400 meters before. often 330mph. The shutdown area is longer now cost of running a shorter track.

Scotts crash
http://www.youtube.com/watch?v=ucUL6296Ue0

[Grant Monkhouse]

oops i did mean nitromethane, they are at 1,000ft now but they keep it going through the 1/4 for the show:D

[PGiljevic]

But not turbocharged Peter so boost does not come into account here. I also play with these engines and even have 2 rotary engines. 4.9cc and 1.2hp.

I have had lots of the OS Wankels, too slow for me, I run my own modified AXE Rossi LSK motors fully modified and they make over 3.5bhp @ 26000rpm (runs to 36000rpm), very strong mid range and huge revs and can use proper tuned principles like 2 strokes can, which sadly the wankel can not... all from only 3.5cc.

I mad emy own bored out carburettor lol and crank shaft, and ported the sleeves too, stupidly good fun. I gave up racing mine as always people would come to me at the track to tune theres! and I took up the hobby so people would leave me alone and to destress from working on cars all the time. :yes

You should see my little tuning log, its funny reading back on it, AFR\'s, engine temps, engine rpm, all done through telemetry ! I ran over 20lt of fuel through one engine to prove it, was renoud for completeing a race then filling the car and ripping donuts contstanly for 15 minutes as a victory celebration.

:burnout

We should start up another thread on this alone!