ESE's works engine tuner

[Frits Overmars]

....harking back to my real shit fight with Patrick about converting RWHP to EngMod crank power - where he was absolutely adamant i was spouting garbage, he is now suddenly quoting exactly , and completely agreeing with my and Neels assessment of 12.5 to 15% depending upon if its a Dynojet or not.

Wobbly, Are these figues of 12.5% to 15% that you quote, the estimated loss between crank and wheel HP on an inertia dyno?
I seem to remember that Frits long ago posted a quite detailed analysis of this and concluded that the loss would be about 10%, including tyre/roller friction loss.

As you say, it's long ago.
First let's take a look at Wobblys "if it's a Dynojet or not". I ran comparative tests at Ten Kate with my hard- and software connected to their Dynojet, with their world championship-winning superbike driving it, so we obtained simultaneous measurements.
The Dynojet software was found to exaggerate by 11%. If you measure 100hp on the drum, Dynojet will say you have 111hp.
It's one way to make the customers happy, I suppose...

A set of well-lubricated straight-cut gears gives about 2,5% transmission loss and a well-lubricated chain transmission does about the same. So from the crankshaft to the clutch & gearbox input shaft, to the gearbox exit shaft, to the rear wheel, you have three times this 2,5% loss. 97,5% of the 100% crankshaft power arrives at the gearbox. 97,5% of those 97,5% exits the gearbox, and 97,5% of 97,5% of 97,5% arrives at the rear wheel. That's 92,7%.

Now the calculation becomes less straightforward. The tyre must be pressed against the dyno drum with a certain force or it will slip. This force deforms the tyre which consequently gets hot, which means a power loss.
How large this deformation and this loss are, depends on the weight of the person sitting on the machine, on the drum diameter, and on the tyre pressure.
And because the tyre gets hotter, the tyre pressure increases during the dyno run. By how much? God only knows, and I haven't got his mobile number.

With at least 3 bar tyre pressure and a drum of at least 400 mm diameter there may be somewhere between 5% and 10% power loss between rear wheel and drum. So the drum is accelerated with something between 83% and 88% of the crankshaft power.

In all, while a rear wheel dyno may be nice to check if the engine is still in good shape, it is unsuitable for development work, in my opinion.

I even prefer to keep the transmission chain out of the measuring setup. I remember Jan Thiel sitting comfortably behind the double glazing of the Garelli dyno cell and me kneeling beside the engine with an oil squirt in my hand. A squirt of oil on the chain immediately produced an extra 1 hp.

Some track marshals also have experience in that area. I once saw a broken chain left in the middle of the track. The marshal who quickly tried to remove it with his bare hands will never forget it....

[F5 Dave]

So the take away message is; lube your chain at the race meeting .

[Frits Overmars]

So the take away message is; lube your chain at the race meeting .

Yup. Just make sure the chain doesn't lube the tyre.

[lodgernz]

As you say, it's long ago.
A set of well-lubricated straight-cut gears gives about 2,5% transmission loss and a well-lubricated chain transmission does about the same. So from the crankshaft to the clutch & gearbox input shaft, to the gearbox exit shaft, to the rear wheel, you have three times this 2,5% loss. 97,5% of the 100% crankshaft power arrives at the gearbox. 97,5% of those 97,5% exits the gearbox, and 97,5% of 97,5% of 97,5% arrives at the rear wheel. That's 92,7%.
.

Thank you Frits. That's what I was hoping for.

So, a brake dyno connected directly to the gearbox output shaft (no chain), should measure 97.5 * 97.5% = 95% of crank power.
And, I suspect, far more realistically than an inertia dyno.

[husaberg]

I seem to remember Jan saying there was a measurable difference. Between a primary drive output from the center vs one from the side.
I can't recall what was better but I think it was side?
There were stuff about toothed belt being more efficent when compared to chain. But not sure if that took into account the wet vs dry clutch. But as it was with g50 and Manxs Norton I assume it does.

[Frits Overmars]

Thank you Frits. That's what I was hoping for.
So, a brake dyno connected directly to the gearbox output shaft (no chain), should measure 97.5 * 97.5% = 95% of crank power.
And, I suspect, far more realistically than an inertia dyno.

In fact, an inertia dyno works at least as accurately as the very best braked dyno, and it is much simpler and cheaper. But it can't do everything; if you want to measure at static revs, you need to augment the inertia dyno with some kind of brake.
On the other hand, an inertia dyno is ideal for developing a competition engine which is never going to be used statically but is constantly accelerating.
And with the right choice of transmission ratio you can ensure that the rate of acceleration on the dyno is identical to the rate of acceleration on the track.
This is especially important for a realistic exhaust gas temperature behaviour and thus for an optimal functioning exhaust pipe which as you know is the single most important factor in two-stroke power.
Another advantage: a dynamic dyno run may take roughly ten seconds and therefore the engine might survive an ignition timing that is too early or a mixture that is too lean, whereas a static measurement, which can take up to five minutes, would destroy that engine.

[Frits Overmars]

I seem to remember Jan saying there was a measurable difference. Between a primary drive output from the center vs one from the side. I can't recall what was better but I think it was side?

It was. The power take-off from the crankshaft center required an intermediate shaft (with an extra pair of gears) between crankshaft and clutch.

[F5 Dave]

Wobbly typically posts something about no free lunch about this point. Usually as I'm hungry.
Ok I'll pay for my lunch.
Ooh bacon egg paninini.

[ApolloMotoMoto]

Question on crankshaft contruction;

Crank-halves...

Nothing fancy, just trying to ensure we get a good press fit on the crankpin....

Looking at JIS S45C steel hardened to HRC 35.

That sound appropriate?

[jato]

What type of hardening are you proposing - case hardening? what size crankpin bore? finished after heat treatment i expect - i've been studying a lot of crankshafts in recent times to see which methods defer to cost/ease/quality and am interested to see how people tackle these critical parts

[Frank S.]

Question on crankshaft contruction;

Crank-halves...

Nothing fancy, just trying to ensure we get a good press fit on the crankpin....

Looking at JIS S45C steel hardened to HRC 35.

That sound appropriate?

I would rather use a higher quality steel.
42CrMo4 quenched and tempered to 1000-1200N/mm²
is far superior to a S45C in terms of strength and toughness.
It is also used for some racecar crankshafts.

btw 42CrMo4 is AISI 4140

[Wos]

just wanted to share a new method of calculating exhausts. for a couple of years I've been using 2 very different pipes that give almost the same poweroutput. tried to make better pipes but not luch luck so far. So I thought : the best pipe must lie somewhere in between them. and so I calculated a pipe which has exactly the average dimensions of both . blue pipe = R, green pipe = GY, Average pipe = pink



and the result :




also made an experimental pipe. in the past I used a program of Coker racing to calculate exhausts, and that seemed to work also, but there was something funny about the diameters with that one : as you lower the rpm's, the pipe became fatter which is contrary imho. So I made a pipe using Coker length's and FOS diameters, and included a reverse-cone baffle (here compared to the AVG pipe) :
Attachment 355883
and the result is also good :
Attachment 355882

Many many tanks to you Jan for creating the pipe excel with help of Frits/Jan/ Wobbly.

We made 5 pipes for our needs, setting Peak where we need it for enduro classic races.

We think it works very well!



Hope it isnt old fashioned or obsolete now !??


Think we will use it, till there is something better !!!

Newest projekt puch with rotax 124⁶

[ApolloMotoMoto]

What type of hardening are you proposing - case hardening? what size crankpin bore? finished after heat treatment i expect - i've been studying a lot of crankshafts in recent times to see which methods defer to cost/ease/quality and am interested to see how people tackle these critical parts

crankpin diameter is 16mm

Hardening process is not fully defined at this point, still reviewing option.

After doing a cursory search of what I could find from Wayne on the subject of crank material and hardness; this is what I am comming up with:

From Wayne:

-crank wheels need a ductile core
-EN36B is the "best" material

"(...) all the surfaces that wont be ground need to be painted with a copper based coating to prevent the hardening gas from thru hardening the whole part."


In another post, speaking about press fits tolerance ranges considering different crank web materials using a solid pin vs a hollow pin, Wayne says:

"(...) your press fit (...) final number depends upon two main factors.

Solid pin or hollow pin , and crank material/heat treat.

For a hollow pin and or a case hardened only material ( 4140 ) the number is 0.08 to 0.1mm.

For a solid pin and or thru hardened tool steel ( EN36B ) the number is 0.05 to 0.06mm."

When Wayne says "thru hardened EN36B" I am **assuming** this is because the pin-bore would be thru hardened using the differential hardening technique described above, using the copper masking to keep the crank webs ductile while the pin bore is thru-hardened to a depth of hardness beyond that of case hardening???

Or am I assuming wrong; and the reference to thru-hardened tool steel is merely to give an example material that will require a smaller press fit tolerance number???

Pre-hardened 4140 was also on our "consideration list", but it appears to be less favorable when one considers the differential hardness requirement.


Any advice from here would be greatly appreciated;


Strongly considering the differential hardened EN36B (which sounds like a case hardening process to my inexperienced ear with the copper masking and the reference to hardening gasses).

[TZ350]

As I probably wont get to ride it on the track because of the prohibitive entry costs for big bike racing compared to my regular Bucket racing class.

I thought I may as well have some fun with it on the dyno.



I have the twin fuel Petrol for the pilot jet Methanol for the main jet thing working Ok (42 RWHP). On the dyno it uses one liter of petrol to two liters of Methanol. On the track it would probably be more like 50/50 as you are not on the main jet nearly as much as the dyno.



Now I have turned my interest to Nitro injection. The Ignitech ignition I use has two maps and provision for mapped power jet control.

I use a thumb push button on the handle bar to let the Ignitech know that it is Ok to swap to the second ignition map and to run the peristaltic Nitro pump when the RPM is in the mapped zone.

As I have pointed out before, if the motor has a correctly jetted carburetor for Petrol and/or Methanol then adding Nitro directly to the airstream works perfectly. As Nitro has slightly more fuel than oxygen so it slightly enrichens the mixture while bringing more oxygen with it. The perfect self correcting liquid supercharger.

Anyway previous experiments have shown that this can work reliably.

The concept is to have a bike you can ride around all day on its regular fuel and push a button when you want the Nitro supercharging effect to kick in for that extra boost in power. Other than mechanical strength restraints there is probably no limit to how much Nitro you could pump in.

Now I have to just get it working properly so I can do some back to back dyno runs to prove the concept.

[wobbly]

The first answer here is about the Dyno RWHP numbers to EngMod crank numbers.
I have done many , many racebike projects with big/light wheels and slick tyres , nearly all using AvGas on various DynoJets and the conversion has historically ended up at the 12.5 to 14% number.
On my engine dyno with a chain drive from the engine sprocket to the inertia mass its closer to 5 - 8%.
Patrick is now quoting as gospel , that converting from his RWHP inertia dyno to his MOTA numbers is 15% - but he is not running petrol, one minute its E85 , next its going to be Methanol so of
course those conversions will be very different.

Re the crank wheel press fits.
The best process is using the EN36B and doing the correct rough machine, stress relieve , finish machine , then case harden with masking to 58-60 Rc.
But 4140 can be finish machined in one go then Nitrided on the pin bore and journals only , works just fine for cranks that will only ever get rebuilt a few times.