ESE's works engine tuner

[peewee]

the intention certainly wasnt to reduce case volume but its innevitably one of the side affects i guess. the reasoning was to reduce voids in the reed area that contribute to nothing. thats assuming the voids have no value but i dont know for sure. i thought about filling in some of the extra space above and below the reed stoppers also. if nothing else, atleast the reed screws wont ever fall into the engine . anyways heres where im at now

[ken seeber]

KERS for bikes

If we consider a 125 (2 stroke, of course !!) road racer weighing 140 kg all up undergoing maximum braking. Assuming that it might be travelling at 100 km/hr at this time and that it was de-accelerating at 1.4 g (an estimate) and all the braking was being performed by the front wheel only, then the tractive force being exerted by the front tire against the road surface can be calculated from:

Force = ma = 140 * 9.8 * 1.4 = 1920 newtons, or more understandably 196 Kg

At 100 km/hr, the actual braking power being dissipated by the front brake can be calculated from:

Power (kW) = F (newtons) * velocity (met/sec)

= 1920 * (100 * 1000/(60 *60)/1000

= 53 kW (= 71 hp). At 200 km/hr, this would be doubled.

At 100 km/hr, the wheel (assume 600 in diameter) would be rotating at:

= (100 *1000/60)/(pi * 0.6) = 884 rpm.

So, with all that in mind, let’s consider the additional following:

1. Any energy recovery from the back wheel is not available, as pointed out by Frits
2. Going back in time as kids on our pushies, we used to have lights that were powered by a small friction driven generator that was flicked across on to the side of the front tire and driven with a small serrated roller on the end of the generator. Crude & inefficient I am sure, but it did work.
3. Attached is a picture of a 6000 rpm 20 kW electric motor, weighing just over 4 kg. This has an outside diameter of around 110 mm. In this case, the actual body of the motor actually (& usefully) spins.
4. That any energy recovered during braking and can be returned to provide some motive force must be considered useful, assuming that any gains are not offset by any losses due to the extra weight, complication, cost etc
5. It would be very undesirable to add mass (eg, 4 – 5 kg) to the unsprung mass to the front wheel assembly

So, combining these technologies, we could have the outside diameter of the motor rubbing/rolling against the outside diameter of the tyre. See attached sketch. The electric motor/generator in this is shown to be mounted on an arm that is suspended from the frame near the steering head. Alternatively it could be suspended from the lower triple clamp (so that it rotates with the total steering assembly). The motor in this position would not add to the unsprung mass, but being at approx 90 degrees to the wheel centre it wouldn’t be to so sensitive to wheel up & down movement. At 100 km/hr it would be spinning at 4820 rpm, within its 6000 rpm range

Obviously it would require some means of actuating to apply pressure against the tire whilst braking (& accelerating). In absorption mode, it might only be taking a quarter or so of the total braking power required, so it wouldn’t dominate the overall braking feel.

So, we have taken this percentage of braking power that is normally just lost to heat. If this recovered energy was then stored in some form of battery, probably a capacitor. Should the bike be driven thru the rear wheel electrically, then this energy could be transferred to that drive system. However, should it be a currently conventional mechanical drive , then the energy cycle could be reversed so the electric motor was engaged with the front tire again and the energy in the capacitor discharged via the motor to the front tire/wheel. Not sure if you would see tire smoke pouring from the wheel spinning front tire of a bucket though.

Even if it was grossly inefficient in terms of braking, then who cares, as we are still dissipating braking energy, just not all via the front brake.

What could you get out of it? Well, say there was a 10 second total braking period (for a one minute lap) and it was 80% efficient during braking and 80% efficient during acceleration, then we could experience a 20 * 0.8 * 0.8 = 12.8 kW = 17 hp hit under acceleration for 10 seconds each lap. This is on top of your 60 hp 125 cc Wobbly ported, Frits exhausted, 45 mm carb engine. Maybe the figures are a tad flaky, but I would consider that short power return to be useful.

So, possibly a touch of too much dreaming and not really suggesting that it might be feasible cos it raises all sorts of practical questions, but it embodies some of the principles that might be required to apply KERS to a race bike. Another option might be a shaft drive style rear hub at the front, driving a shaft parallel with the telescopic fork axis, with the elec motor/generator at the steering head area.

Your turn fellers.

Ken

[speedpro]

Yeah, I'm going slowly mad thinking about mine, have the ignitch pulgged in now, unable to improve on a straight 15 degrees all the way through.

EXACTLY what I got as well, straight 15 degrees was best on dyno, with only a slight gain by rolling off a few degrees right at the top.
Different combustion chamber shape would probably have changed the timing requirement though. My head has a small radius from squish to bowl.

[TZ350]

Page 960

Fuel Talk.

Re the fuel flashing off all its good light front ends.
Next time you go to a gas station have a look around and somewhere you will see several pipes stacked up in a row that are often over 6M high with a U bend on top so the outlet faces down.
These are the tank breather pipes, and the pressure head created in the tank by this high exit vent is there to contain the vapour pressure of the fuel.

When you have a 1/2 empty 20L container of petrol, within several hours the light chemicals in the fuel will flash off and create the vapour pressure you always have when opening a drum - this "good stuff " instantly dissipates to atmosphere as soon as you open the tin, and the more times you do it, the worse the fuel gets.

With fuel sitting in a kart tank, and a direct vent to atmosphere as you must have, the vapour pressure exits to atmosphere continuously, so overnight is plenty long enough to ruin the
already suspect pump gas.

The effect is much worse now that lead has been taken out, and all manner of really bad shit has been put back in to lift the octain to 98 especially.
The number of times I have seen mainly KZ2 but also KT100 and Rotax engines detoed to death by this effect is just amazing - but hey what do I know after all these years at the track and dozens of

National/World No1 plates .
The higher the tune/bmep the worse the effect you see from low octain fuel with low vapour pressure, so alot of racers get away with it, alot of the time - but with fresh fuel you can always rely
on your baseline tuning settings, without that assurance you have no chance against the guys really on the ball.

A superbike team here was pinged for running illegal fuel (not 98 PULP) they provided samples of the fuel, evidence of where/when it was purchased etc etc. The samples showed their fuel was not doctored but just very fresh fuel from a very busy servo on the Tullamarine freeway a mere stones throw from the Shell refinery.

Dead right that Avgas isnt so prone to causing issues with vapour pressure loss - this is simply due to the fact that the lead
content that has so much effect on the deto resistance,does not flash off to atmosphere.
Running the vent hose from a tank down lower than the fuel level, or into an airbox, simply means the flash off runs up, then down and out to fresh air. No free lunch.

At the petrol station the tank is underground so probably at a lower temp so maybe less vapour
the surface area of the petrol at the station is probably quite small in relation to the total volume of petrol in the tank so more light fractions are more likley to stay in the petrol. Do the tank vents in the petrol station let in more air than vapour out ?

Petrols vary widely but the RVP ( Ried Vapour Pressure ) can be upward of 9psi - thats the pressure you hear escaping when you open the drum lid.
Having the tank vent 6M up in the air creates a gas head of pressure above the fuel in the gas station tank.
The RVP climbs in the tank as the fuel evaporates until equilibrium is reached, and the rising column of gas in the vent tube continually keeps the tank under its own pressure.
A vent tube only a few inches above a kart tank does nothing.
Here is a good description of RVP and its effect.

" Now that I have the equipment to test fuel's RVP and it's relative "freshness" I have been testing almost every racer's fuel, and now am thinking about what is actually going on in everyone's combustion chambers. RVP readings indicate the presence of the fuel's "front ends" which are the first to initiate vaporization. Front (or "light") ends are critical to initiate and create fuel vaporization especially in low temperature (air and engine) engines! Remember--fuel will not burn until it vaporizes. Unvaporized fuel only displaces O2 in the combustion chambers and can short out spark plug electrodes. The misfire we hear when people "warm up" or "clean out" their race engines is a combo of lean net mixtures in the combustion chambers and unvaporized globs of fuel shorting out the plugs!

The AMA motorcycle flatrack pros say that they must now use spec fuel--Sunoco Supreme which is supposed to have RVP of 8.0psi, and sold to the racers in "sealed" 5 gallon pails. Connecticut AMA pro #2 Kenny Coolbeth was here with RLJ racing (Ron Jewell of Holley, NY) recently preparing for Daytona with a new modded Honda 450 (Ron Jewell never was able to get Kenny's Kaw 450s to quite match his 63+ hp Honda mods, so Kenny wisely jumped ship). His sealed pail of Supreme's measured RVP was only about 4psi instead of the published 8psi meaning that half of the front ends had escaped into the atmosphere between refinery and the pail! Sunoco tells me they do not put fuel in drums or pails, they only ship rail and truck tankers to wholesalers, and after that it's beyond their control. Once again we needed close to 12/1 A/F (wideband out the muffler) to make max HP at those high revs instead of the 13/1 that is most common with flattrackers who use higher RVP fuel. So surely more of the stale Supreme is going through Kenny's intake and combustion chamber in globule-form and ultimately vaporizing in the exhaust pipe.

So, if someone is tuned spot-on with his RVP pump gas blend at 13/1 out the pipe, then splurges for some of that expensive Supreme that he sees Kenny C pouring into his tank, his bike will probably slow down from suddenly being way too lean in the combustion chamber. "Over-Octaned" is the commonly offered, but incorrect explanation for the HP loss.

Lower than published RVP is very common--the last test I did on some VP Import fuel for a turbo two-stroke measured ZERO psi meaning it was DOA in a sealed pail. Yes, we were able to use it, but we were careful to have the engine smoking-hot (engine heat helps vaporize the stale fuel) and A/F in the conservative 11.5/1 range--staying far away of the 13/1 max HP A/F ratio".

And this is starting to answer the question I posted pages back about what was happening with my dirt bike that it often would run dreadful until it had passed through the gearbox then would run sweet. Yet 2stroke drag bikes run cold.

I was wondering about the physics of why.

Of course the dirt bike has old gas in it. Even some residue in the bowl, but has to use old gas and worst effect is when it is cold. Once the engine is hot the fuel will vapourise better.

I'm not keeping up, they were running leaner by exhaust reading to run richer in the blast pot?

NO - when globs of fuel do not vaporise, they pass thru the engine unburned and this gives rich readings on both egt and Lambda.
If this situation is " fixed " by the tuner jetting down, we then get a chemically lean condition in the combustion space but this then reads as "normal " for best power at say 13:1.

This is what happens to the KZ2 engines that regularly deto the piston and head to death,when crap fuel is being used with what the driver thinks are safe jets.
In the quoted article, they kept the bad fuel under control by not going leaner than 12:1,this saved the engine, but made alot less power.

Fuel vaporisation is very good with a carb such as the Lectron, and for years it has been seen that these carbs are way less sensitive to A/F ratio than your average VM round slide Mikuni for example.
If you read the marketing blurb by SmartCarbs, they are telling us that the fine mist from that carb is way better than that we get from what we would regard as normal injection.
But running super high pressures and or air over fuel as we see in Etec etc may ameliorate this , dunno.

To answer the two questions, yes fuel mist will drop out of suspension and become raw fuel sitting on the walls of the ducts.
Conventional wisdom tells us that in a 4T this can be minimised by making the inlet port walls surface finish equivalent to 180 grit wet and dry. Now this is interesting as in most cast 2T transfer ducts end up being around this number - and so called " beautifully " cast ones and those polished up by
expert tuners end up way smoother - loosing power in the process.

The other question around the SmartCarb fuel needle issues.
I told them right at the beginning that the only way to enable fine tuning of the carbs - especially when on a twin Banshee for example, was to run a powerjet with very small jet increments as Lectron
did with great success very early on.
But they are /were so enamored with their own cleverness re the insensitivity of the carb thus not needing to be fine tuned, I was ignored.

The possibility was / is there to finely emulsify the powerjet fuel using the so called AdjustaJet principal of having a variable air bleed into the powerjet suction circuit but sadly
some horses dont even like water.
Those carbs do work supremely well, but seems for now the only way to get fine tuning is to be fucking about sanding the needle tips with a digital micrometer in the other hand.

Sorry Frits I gave the wrong impression with that statement, but as per the article I quoted above ( from Dynotech Magazine a superb mine of info on 2T testing )
"unvapourised fuel only displaces O2 in the combustion space " so we do have excess fuel dropping the egt and if the engine is then leaned down it will deto due to the actual lean condition in the chamber.

But if using Lambda we cannot run fuel that has low amounts of light front ends at the "normal " best power ratio of 13:1 as the unburned droplets contribute nothing to the combustion process.
So the actual " burning " A/F ratio in the chamber is in effect lean.
As in the Dynotech example they gave they had to run under 12:1 or the engine would have been destroyed by deto in an instant, when running the new fuel with zero RVP.

I have done the tests on a Superflow and the so called HV Lectrons will outflow a size for size Mikuni or Kehin easily , and ,as say a 38mm HV has a 34mm venturi
behind the slide it acts like a much smaller carb at 1/2 throttle.
In Europe I know they are using 30mm Lectrons on 50cc race engines with great success.
The SmartCarb does not have a venturi, but has an egg shaped bore at the slide that probably does the same thing.

They also have an aux venturi above the top of the entry trumpet, that is connected to the bowl air space - and it is this that gives the carb its auto adaption to air density,be it weather or altitude.
This for sure works a treat, with no jetting change when climbing Pikes Peak - but at the moment they do seem to be having endless trouble getting the things into the ball park at sea level.
At this stage Lectron do have a huge range of incremental needles to suit any application and also have a powerjet with very fine flow sizing that makes fine tuning a twin super easy.
I have just got a 30mm SmartCarb here for a Giggle project , so if someone with 1/2 a clue wants to do some testing im sure we could arrange something.

Here is a link to DynoTech,that mentions stale fuel as well.
I have been using the copper tube deto detector into my dyno headphones for years, so as im in a good mood again today here is the detail
on how to do it and why.

http://www.dynotechresearch.com/blog...nYear=2013#294

Nowdays, I like to use the Czech deto box running into the dyno data logger, so i can see at a glance where the deto occurred exactly.

I was dreaming late last night ( about 2Ts - what else ) and thought thru the statement that Frits was questioning ( a complement to a very skilled bullshit detector that man I must say ). Maybe the logic of " unvapourised fuel only displaces O2 in the combustion process " leads to the Ex gas then also being low in O2 so the Lambda reads rich ?

I dont know to what extent ie what % of O2 can be displaced by fuel that is never burnt, and if that level is then sufficient to affect the Lambda reading.

That then leads me to the question - wouldn't a continuously misfiring engine read rich on the Lambda, and isnt that then the same end result as unburnt fuel droplets passing thru an engine?
This is too early in the morning for this - I need strong coffee.

I hope you had that coffee, Wob. And as you are ten hours ahead of me, I suspect you are sipping something tastier by now.

First let's look at the 'logic' of unvaporized fuel displacing O2. The fuel is carried into the combustion chamber by the air; air and fuel are in there together and there's no way that the air could be forced away by unvaporized fuel droplets.

Unvaporized droplets won't be doing much forcing anyway because the volume of an unvaporized droplet is about a thousandfold smaller than the volume of a vaporized droplet.

Wob, detecting bullshit is quite easy if you produced that bullshit yourself in the past.
I once ran an engine on the test bench and the Lambda sensor said 'lean', or so I interpreted it at the time. So I jetted up.

Then the Lambda sensor said: 'now it's even leaner!' What really happened was: at the first test the engine was so rich it was misfiring. And no combustion meant: unused oxygen in the exhaust gas.
Naturally when I jetted up, the misfiring became worse, even more combustion cycles failed and even more unused O2 hit the Lambda sensor.

Lesson learned: a Lambda sensor does not say 'rich' or 'lean'. All it says is: I see ogygen'.

Amazing Frits how complex logic can get, and more amazing that in reality its all simple when you finally get to understand. Of course Lambda only reads the O2, what a dumb shit.

FUEL DROPLET SIZE REALITY CHECK

Some pages ago, there was some discussion on fuel droplets. Got me thinking as to what size a fuel droplet might be.

So, using the RSA 125, 54 hp @ 12,000 rpm as an example. Rounding numbers as we go, this equates to 40 kW. Referring to an SAE paper 2004-01-3561, the instrumented dynamometer performance of a Honda RS125 engine was measured and compared to various computer predictions. This showed a best BSFC (brake mean specific fuel consumption or basically fuel mass flow rate per unit of power) of 400 gm/kWhr. Using this figure as a general guide, we can calculate a fuel flow rate of 40 * 0.4 = 16 kg/hr = 0.27 kg/min = 270 gm/min.

At 12,000 rpm, this gives us 0.023 gm/cycle. Using a fuel density of 0.74, this gives us a fuel volume per cycle of 0.031 mm^3.

If this was a cube of fuel, it would be of (0.031)^0.333 = 0.31 mm per side or if a spherical droplet, it would be of (0.031 *3/4 * π)^0.333 = Ø0.4 mm.

Pretty small stuff really, not something like the Ø3 -4 mm as one might imagine a droplet might be.

Taking this one stage further, if the A/F ratio was 12:1, this would mean 0.023 * 12 = 0.28 gm air was entering the engine per cycle. Using an air density of 1.2 kg/met^3 (at sea level & 15 deg C), this would give us a volume of air entering the engine of 0.000233 met^3 = 233 cc. From this the Delivery Ratio can be calculated at 233/125 = 1.87 : 1. This is pretty good, and sort of correlates with the DR indicated in the SAE paper of around 1.4 : 1, this engine under their test conditions was around 30 kW, not the 40 of the RSA.

Comparing the 233 cc to the volume in the cylinder at the time of exhaust port closure. This (trapping) cylinder volume at the time of exhaust port closure (based on a 120 mm rod, 54 stroke and 192 exh open duration, gives a stroke of 27.45 mm from port closure to TDC) would be 63 cc.

So, ignoring all temperature rises and pressure variations, this means we are stuffing 233 cc of air into a 63 cc volume, a ratio of 3.7 : 1. Some time ago on pitlane.biz, Frits (I think) stated that Jan Thiel took the entire exhaust off the RSA engine and tested it. Would have been a tad noisy I’d imagine. It obviously would have had no benefit of any harmonic supercharging (as with the expansion chamber) and resulted in a power output of 18 hp, compared to the 54 hp which is 3 times the power. Sort of matches the 3.7 : 1. Tells you just how useful the expansion chamber exhausts system.

There you go, a bit of rough trivia.

Ken

Ok my problem; along standing issue of ring seal and bore wear. MB100 running KT100 piston. Both steel bore std so ring are compatible.

There was an. Issue when the. Rod continued on its path extending the inlet port to the bottom. As I've case reeded it I've glued some ally in the hole to make a boost port fully formed. So I do have a question that this lack of support at the bottom could be affecting the bore at the top. But I've never had the ally crack it's epoxy or fall out and the barrel is complete for a cm below the ports so should be ok.

anyhow I always get a polished bore above the ex and the boost port. Always wears there and a hone won't bring it back round easily. The area is scooped out above the exh the longer it runs. I'm also seeing scooping above the boost port. Running 20:1 castor oil. Ex port is 68% width , heavily chamfered and very oval and symmetrical. Ring seal has never gotten better than 25% (often much worse) despite using torque plates and heating to operating temp before honing. KT runs say 8% as comparison . Barrel is water cooled now.

so the KT piston runs it's ring peg centrally at the back over the open back boost port which we all knows works in many engines from where I first saw it in the 256. A difference I'm wondering is that the Rotax and everything more modern is plated. Contemplating one more go last oversize moving the peg to between boost and transfers. Thoughts?

The rod angularity is at a max 1/2 way down the bore so if the lower skirt isnt supported properly the piston will cock over, dragging the ring edge into the bore and creating the wear pattern.

Dump the 18th century fish and chip cooking oil and get something in there that has at least a modicum of film strength.

Whiiir.CLICK. ok we'll get to that later.

Ahh Wob, you have a way with words that makes me laugh. . usually at myself.

I'd only changed to Castrol R30 in an attempt to get better ring sealing. I thought the old bean oils were supposed to have surprisingly good film strength esp when hot (& teh bike was air cooled not that long ago).

Anyways, since it has a full reed conversion I trimmed the back of the piston from 56mm to 48 as it stuck down in the way at BDC. I'd noted the old aircoold YZs had most of the piston back missing and the KT100 .skirt was reasonably long and parallel. A few pages back you indicated that the most flow isn't happening at BDC. Perhaps I should go back to full length skirts (except on Saturday nights when its dark).

Most of the transfer flow IS at around BDC if the pipe is correctly designed to give max depression at this time.

Inlet flow occurs when the case starts to go negative ( and helped by the inlet length if its tuned correctly, as this goes positive ) due to the pipe suction pulling the mixture in the ducts into the cylinder,and this depression eventually opens the reeds via the case,near BDC as well. Thus piston holes, Boyesens and short skirts all help the initial flow as the piston starts to rise.

Bean oil always has had crap film strength, what it does have is the ability to give a nice smooth wear surface - as you said when things get real hot it retains this superior wear pattern, wheras a full synthetic disassociates into non lubricating shit chemicals.

But the new generation of oils based on esters that mimic castor but have the huge film strength of synthetics are way superior to both.

The best oil from much testing by many clever tuners for the air cooled KT100 now,is Elf 909, the most castor like of the new blends.

In my testing the best oil now for watercooled engines on pump gas that get close to being overheated by 640C in the header like we used to on Avgas, is Motul Kart at 20:1.

The super oils like Elf 927 were developed for unleaded race engines, as these run fastest when alot richer than a leaded setup and they never see the temps that killed full synthetics badly.

If you want to get the best cylinder surface on a new chromed bore, then slober R30 all over the place, mix it up at 16:1 and ONLY idle the new engine for 5 minutes.

This reduces the ring tension from high cylinder pressure, and the castor oil lets the ring/bore surfaces wear in to each other smoothly.

Once this is done, dump the castor and go racing hard on a semi synthetic.
Ive won dozens of titles with engines done this way.

How is the exhaust bridge? Seems like the problem that the gasgas has, pegging the ring in the bridge, solution was to drill 4 holes with 1.5mm chamfered to 2mm.

Or another note, what do you guys think about the shell racing M oil?
I can't run it on the 125, fouls plugs like there is no tomorrow, A747 doesn't do anything like that, but runs great in the cast iron 45mm CRM liner.

Well as I said, fully synthetics like 2T are not good when overheated in an engine that runs leaded race gas. Where the normal running temp needed to make the fuel work correctly, destroys the film strength - the only good reason to be running a full synthetic in the first place. And at 30:1 it would struggle in any real race engine.

I had no idea you could still buy A747 - easily the best oil made for leaded fuel, many years ago.
Shell M was developed in the stone age,for use with Methanol fuels, so no reason to be using it for anything else, or at all really.

I wouldnt put Amsoil in a race engine if it was given to me, and it ran at only 5,000 rpm.
Last engine I saw on Amsoil, was a microlight that had crashed, due to a skirt dropping off.
The other piston was OK, except for the 0.012" bore clearance after 3 Hrs in the air - running 100:1 like it said on the bottle.

Every RS125 by Honda should have 2 bridge lube holes and 1 each side of the boost,unless you want to be freeing snagged rings all the time.

A T port is absolute hell on any oil trying to keep the ring off the bore, even with super trick piston shapes and properly relieved bridge geometry.

Very good. Reeds are chipping a little even at modest revs with piles of oil.

Motul 800 a similar brew as Castrol 2T but as I said the much later Motul Kart product seems to be a very good imitator of castor - the 800 certainly wasnt, with every engine I pulled down being very "dry" unlike Kart where everything is covered in a slobbery wet film. 20:1 shows gains in the aircooled KT100, but not so much in a watercooled, except in reed engines where the richer mixture always helps reed cushioning and prevents incipient tip chipping.

Ok I found something interesting. it says nothing about this in the ingredients on the data sheets

'Thanks to its high content in specially selected Ricinus oil, ELF HTX 909 provides exceptional
protection against gripping.'

http://www.nkp-karting.com/uploads/products/files/HTX 909 EN.pdf

revised 2-20-2014 http://www.quickfds.com/out/16986-29...967-017784.pdf

The 909 oil mix seems to be specifically directed at the 20,000 rpm direct drive 100cc kart engines, and as I said its for sure the best oil today for the aircooled
KT100 Yamaha, as I have done the direct testing for a customer who is one of the top tuners here.

Those guys are all die hard castor users, and it has taken several years to convince them the 909 is " better " but now they all use it.

Running the 976 full synthetic always lost power on the dyno when run very hard at 650 + in the header, as all top Yamahas do.

This was designed specifically for the unleaded GP engines, that dont run super hot like we did back in the day of full leaded rocket fuel, nor like they do in aircooled race engines.
Here is an old dissertation on how castor works.

http://www.go-cl.se/castor.html

So as I read that if you're aircooled run Castor or ideally 909. If yer watercooled run a decent synthetic ester oil.

I'm assuming you don't consider Av as being a hot burning GP like rocket fuel, its just all that we can run vs pump fuel.

AvGas runs best exactly like the old leaded rocket fuel, if you dont have 650*C in the header you aint doin it right.

So yes 909 is for sure the best in an Aircooled running hot at 650*, but is equally fine in a watercooled on AvGas - just dont use a full synthetic in anything
that runs AvGas properly.

Find some old A747, or stick with Elf 909 or Motul Kart.
If you are running unleaded properly at rich ie cooler temps, then spend up large on Elf 927 full noise synthetic if you feel the need..

I get Elf oils at distributor prices if any one wants some for T2 or T4 bikes

We used this castor mix oil for the first time when winning the KZ2 Nationals.
I havnt dynoed it yet, but will do soon after a rebuild is finished.

http://www.kartsport.org.nz/about-us...-now-available

Seems most top kart teams use this now, no one gets it free, so they must have tested it to death in Europe.

Huge EGT temps mean Jack Shit, I have seen idiots with a stock head TZ350 running 2 base gaskets that saw 1360 for 20 laps without seizing.
But funnily it was 5 seconds off the pace of a properly tuned one running 1245/1255 on AvGas.
Getting the max com and max advance possible for the fuel ,without deto is the key - and for AvGas or up to 110 race gas ,mid 1200s at max power means you are on the money.
One jet leaner , if it only sees around 20 to 30* hotter, means the optimum is back one jet richer, as the perfect scenario is 50 to 60* per jet change, as this always gets back to the max power available.
Sure the oil must be good with so many top teams running it, but telling me you have seen 1300 ( like some sort of red badge of courage ) just means the rider wasnt watching the gauges/and or ignored
the warning lights ( and should be shot ) or someone made a wrong tuning call on an engine that wasnt on the money to start with.
On unleaded it would be detoing unhappily around 100* richer at 1200 if tuned to the edge.
If it was really on the limit, it would have locked up at 1300 ,no matter what oil was on the bore.

That was a bit of a rant - but having riders tell me afterwards they saw over 1300 on the gauge, but dont understand why the bloody motor siezed
because they didnt change the jets ,from coming off the dyno really piss me off.

[Drew]

Page 960 already!!!

Dude, go into your settings and tell me how many posts per page you are showing. My feed says page 720 and no multiple of five makes that 690.

Edit, maybe I can since it's 960. My bad.

[TZ350]

Dude, go into your settings and tell me how many posts per page you are showing.

I see page 960 and thought the page numbering system was the same for everybody, but can people chose to display a different number of posts per page and therefore see a different total number of pages on this thread?

I ask because on most every tenth page I have been posting collections of links to the last lot of the better technical posts for easy reference for those of us that are interested in two stroke tuning and never thought that other people may have a different page numbering system to what I see.

[Drew]

I see page 960 and thought the page numbering system was the same for everybody, but can people chose to display a different number of posts per page and therefore see a different total number of pages on this thread?

I ask because on most every tenth page I have been posting collections of links to the last lot of the better technical posts for easy reference for those of us that are interested in two stroke tuning and never thought that other people may have a different page numbering system to what I see.

Yeah, it's optional up to 80 posts per page. I had to change mine to try and line up with your count, but I seem to have failed.

[TZ350]

Yeah, it's optional up to 80 posts per page. I had to change mine to try and line up with your count, but I seem to have failed.

Ok ... I did not know that it was optional, makes sense though. Mine is just the default setting, whatever that is.

[Drew]

Ok ... I did not know that it was optional, makes sense though. Mine is just the default setting, whatever that is.

15 I think. Finally sussed it by restoring site default.

Now, where do I find the index?

[Haufen]

EVERYTHING makes a difference in these fekin things, dont assume ANYTHING.
I have been wanting to try reed spacers on a KZ2 kart engine for ages, having spotted one on the grid fitted to the enemy's engine.
So prior to the Nationals at Easter I finally got our good TM onto the dyno to recheck the performance with a new "high inertia" crank.
The crank replaced the so called " factory special tune " version that costs some E600 from TM for a KZ10.
I got hold of the wheels for an old KZ9 that were very simple in that they are plain disks with only 1 piece of Mallory opposite the pin for balance - nothing else.
So I added two 19mm by 19mm Mallory slugs in each wheel, on centreline so the balance isnt affected, only the rotating inertia.
Short story is this mod lost 1 Hp all the way to 13200 where it crossed just under peak Hp - high inertia = harder to spin up ( I think )
After peak Hp the lines diverged, and at 14500 the thing made 6Hp more,up from 35 to 41, with a much smoother roll-off ie no " fall of the cliff " effect.
This enabled at least a 1/2 tooth to be added at the rear, well off setting the 1Hp loss with way faster off corner acceleration due to gearing torque multiplication.
I added a 5mm reed spacer and this lost around 2Hp below 11,000,gained 2 Hp between 11,000 and peak, then lost that 2 Hp and more after, getting progressively worse.
So I started playing with reed and backup tensions,using softer main petals I got back the loss under 11,000 and with wider/stiffer backups,spaced further away from the mains
I got back nearly all the overv loss.
So of course I then took the spacer out to recheck, and it made even more power everywhere,fucked if I know,enough to drive you up the wall - but hey it took the National title so who's complaining now.

Thanks for this interesting insight. Did you / could you test the engine on a stationay dyno, also? Or did / were you able to change the spin up time on the inertia dyno? And if not, are you planning to do so? I think the results would be very interesting if the effect is due to inertia.

[F5 Dave]

_{but, what, how?}. If the crank weight can affect power curve, surely it would be different in every gear. It's all very odd.

but yeah dyno time usually raises more questions. Not so often power increases.

[Ocean1]

Short story is this mod lost 1 Hp all the way to 13200 where it crossed just under peak Hp - high inertia = harder to spin up ( I think ).

How can it be otherwise? It's work that has to be done in order to increase revs, same as the dyno load itself, and every other parasitic load in between. Most other motorsport disciplines find advantages in trimming rotating mass. I once made an alloy flywheel for a mini, which has a monster standard flywheel. No dyno, but against a known comparable machine over the same distance there was a couple of car lengths in it.

I understand crank mass was one of the variables Yamaha were trying to mess with in their analysis of comparable power characteristics between V twins and IL4s, they quantified crank inertia separately from "normal" power delivery and immediately their numbers agreed with real world track telemetry. They also mentioned the significant issues rotational inertia caused under brakes. All of the energy expended in spooling up the extra mass was completely lost on deceleration, a feature you also found on the dyno as you approached max revs, yes?

_{but, what, how?}. If the crank weight can affect power curve, surely it would be different in every gear. It's all very odd.

Why would the power curve be different in every gear? Power at the crank would be the same in each gear, no? And the difference in leverage represented by each gear change would apply to energy at the crank, no mater what shape it's curve.

[F5 Dave]

Yeah but if the work has been done and the power curve is falling surely it isn't storing 6hp and the load will be different

[wobbly]

The only difference the gearing makes to the power curve as seen off an inertia dyno is the run time.
In 1st gear it would spin from 6000 to 14,000 in an instant.
Not long enough to get the correct heat level into the pipe.
I usually run it in 4th gear as this acceleration rate is all but identical to what happens in the data readout on track.
After doing 3 full throttle pulls, the pipe surface is up to temp, I then do 2 recording runs back to back and overlay them.
They are usually then identical within 2/10 of a Hp so I choose one and delete the other.

There have been arguments for years over crank inertia in a racing 2T, with the basic theory being that with more inertia the in cycle speed variation is reduced.
At TDC where alot of work is done compressing the combustion charge, the crank slows down - to where it then accelerates very quickly toward BDC and speeds up as the
piston runs over the transfers.
This theory has been rubbished by some clever minds, BUT, bottom line is that it was discovered instantly when HRC offered total loss setups derived from A kit parts
that simply removing the flywheel lost ALL the overev power.
Ive done it, when I first started using Ignitechs on the old MX based RS125 Honda - ditch the flywheel and it simply WILL NOT rev out.
So the factory and VHM came up with so called " high inertia " cranks to be used with total loss where no flywheel was used.
This also then enabled lighter ones to be used for short tracks, favouring acceleration, or even heavyer ones for big tracks where overev power is king.

Jan has stated that he could find no advantage to so called heavy cranks on the Aprilia, but that I am sure is an artefact of the design being very " heavy " to start with
and making it higher inertia again simply ran into the law of diminishing returns.A very heavy crank is simply too slow to accelerate, and nothing worthwhile is gained in the top end against that loss.
A stock RS125/250 Honda has a VERY light crank compared to the Aprilia that is full of lumps of heavy metal.
I have recently built cranks for a couple of customers with very expensive Rotax derived tandem twins, using full circle wheels with no steps and full of heavy metal balancing like the Aprilia
and all report amazing gains in overev ability,cylinders and pipes etc being identical.

[Ocean1]

Yeah but if the work has been done and the power curve is falling surely it isn't storing 6hp and the load will be different

But it is storing energy, all of the energy it absorbed on acceleration. And that energy will be the same over any given pull, no matter what the gear, it's effect is just seen over longer times in higher gears.

As the power curve approaches peak the energy stored in the rotating mass begins to shed power back into the dyno load. That's the over-rev capacity Wobb's seeing with heavier cranks, it doesn't come from combustion pressure, that's declining.

Edit: Worth noting that the extra power delivered beyond peak power revs derived from flywheel mass is transient. A fact you won't usually see on an inertial dyno, because with a static, (invariable) load you can't hold peak revs long enough to see it flatten out. On a brake dyno you wouldn't even see it to start with, you normally collect data at constant revs.