ESE's works engine tuner

[F5 Dave]

That's real interesting and introspective empirical information, so thank you.
But why did you spell realised with a 'z'? I assume autocorrect.

[JdG]

Thanks a lot for the detailed information Wobbly!

Very interesting to know that one can vary quite a lot with the oil : fuel ratio without having to change the jetting.

Also like you said: no race engine should run 50:1, but there’s still heaps of people around that think that more oil reduces power (because of less fuel, if you don’t consider the oil to be a good fuel also) and who are scared that their engine will foul in no-time because of the additional oil.


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[lohring]

On our 26 cc race engines we found doubling the manufacturer's recommended ratio to 16:1 increased power significantly. Power still increases up to around 10:1 and the big end bearings live longer at 16 to 19,000 rpm. More oil doesn't seem to increase power further. We tested several different oils at the same ratio and there was no power difference. All this i believe comes from better sealing on our 36 mm, single ring pistons. I would expect this to make less difference on larger pistons. Below is our fuel test data.

Lohring Miller

[wobbly]

The other side benefit of the 20:1 oil mix was that due to extra oil cushioning, having the reed corner tips fretting with constant serious overev was eliminated in the KZ engines.

[lodgernz]

The only properly conducted oil ratio test I have done was testing HTX 909 on the dyno several years ago when we still used KT100 Yamaha's.
As no one would ever use 2% in any race engine the test started at 32:1 = 3.124% , then 25:1 = 4%, then 20:1 = 5% , then 16:1 = 6.25%.
The tests were all immediately back to back, and the tune was monitored with a CHT clamped to the case determining the warmed up start temp, and the EGT determining the final run temp.

The only result that was of interest at the time was did more oil make more power.
The answer was yes, each change from 32 to 25 then 20:1 all made small increments in power, 0.75 Hp in 16Hp when changing the oil ratio to 20:1 from 32:1.
At 16:1 it made no more power.

In all cases the final EGT was practically identical, within 5*C of the final temp of 650*C thus no jet change was needed nor attempted.
It may seem " logical " that more oil, displaces fuel in the mix - thus making it run leaner, but what many dont realize is that there is also more energy value in the oil, than in the fuel.
If there was any change in the jetting needed, the EGT value would have immediately been obvious, there was none.
So just maybe the combination of less friction, and more fuel energy contributed to the small power increase in that air cooled engine.

I have also tested, over extended time frames, using more oil in the KZ engines, in this case using Vrooam semi castor - a super clean burning oil, or Maxima 927.
On the dyno changing from 32 to 25 to 20:1 made no discernable difference in power, nor the jetting needed ie less than 2/10Hp in 50Hp with absolutely identical EGT - but the piston skirt wear rate, and the wear on the big end washers silver plating is easily measurable and visually better at 20:1.
In this case the parts are changed at the same run hours on the data logger, but imho its making the engine safer and holds up its as dyno'd power longer.

Wobbly, do you think that similar results would be observed with a fully synthetic oil such as Motul 800? I realise that HTX909 is only partially synthetic, partly bean.

[ApolloMotoMoto]

Aprilia RSA 125 Electronics Question....

Does anyone here have any familiarity with the electrical specifications of the AC Magneto system on the Aprilia RSA125?

Picured here;

It "appears" to be a similar configuration to the KTM 50 AC Magneto;

Bi-Symetrical rotor magnet (inner rotor style).

Exciter coil "pairs" with the exciter coils wrapped around a stator "pole piece" which face/engages the rotor magnets flux through the air gap.

I am ASSUMING (but would love confirmation) that the exiter coils are wired in PARELLEL such that each exciter coil "pair" behaves similarly to a single coil with a number of winding turns equal to the summed turns of the pair, but with HALF (roughly) the effective inductance.

This dual exciter coil "pair" configuration allowing for half the inductance for the same voltage output slope, yielding more efficienct charging of the main charge/discharge capacitor in the CDI.

I am ASSUMING this is the configuration used in the Aprilia RSA125....


Furthermore, the Aprilia Stator has an ADDITIONAL pair of exciter coils (compared to the KTM 50 example) that are 90 degrees opposed to the first pair.

This leads me to assume (given the assumed bi-symetrical 2-pole rotor magnet) the out-put waveform from the Aprilia RSA125 magneto stator would show TWO electrical cycles per engine revolution;

Essentially doubling the "charge availabe per revolution".



Picutred along with the Aprilia RSA125 magneto is the KTM 50 magneto (1x pair of black potted coils) and the magneto from my engine system (1x single coil wrapped on red winding bobbin).


Does anyone know the specifics electrical specifications for the RSA125 magneto or enough to answer/ confirm my suspicions?

[wobbly]

Lodger, part of the answer lies in the introduction of many fully synthetic race oils, they all started to appear around the time that GP racing converted to Unleaded fuel.
Motul 800 Elf 976 etc.
Unleaded is best when operated rich, with less compression and more timing.
Up to that time the most widely used oil was semi castor Castrol 927, in fact I know for sure that many teams with oil sponsors actually secretly substituted this so as not to upset anyone.

In the tests I did ALL the fully synthetic oils LOST power when run in the KT100 up at an EGT of 650*, no matter what the oil ratio was, compared to the HTX 909.
What you have to realise is that all the synthetics, when tested in a Timken/Falex machine, have huge oil film strength, but the instant they loose this film and are overheated, they break down into their component
constituents, that are NOT actual lubricants at all.

The very old R30 castor oil has probably 1/10th of the film strength, but when its overheated and breaks down, those component chemicals still operate as lubricants.
And I know some experts have rubbished the Falex machine as being unrealistic in a 4T, but empirical evidence in a 2T shows exactly the same characteristics as the machine demonstrates.
When a synthetic film is broken down, it tears the shit out of everything, a Castor type fails sooner, but the wear pattern is perfectly smooth on the test shaft.

In the KT100 test at very high run temps, I was seeing really premature piston skirt wear using Motul 800 and several other full synthetics - plus the obvious power losses.
I had used Maxima 927 in the USA with 110 race gas in World Champ Jetski's, as the HTX909 was not compatible and would separate out very quickly.
Both are semi castor mixes, and that seems to be the holy grail in 2T race engines operated out at the limits.
HTX909 separates real quick in AvGas, the Maxima doesnt, but both those oils are perfectly fine in pump gas, or the unleaded fuels mandated for CIK or FIA racing.