ESE's works engine tuner

[RomeuPT]

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.

Nice to read this kind of info.

A good tank respirator, should link the top of the tank end then go down with a rubber tube below the tank? mine enters the ram air box.

Do this type of respirator keep the "good stuff"?

Thanks

[fixer]

So the RS50 has now had it's barrel raised by 1.5mm or so. The result as mentioned by TZ350 is that the pipe that seemed to be the best performing pre-barrel-lift is now the worst pipe post-barrel-lift. However, the beauty of this situation is that the pipe that was the worst before is now the best. And it's the pipe I actually own. Brilliant!

Pre-lift, the power looked pretty gruesome. It's the worst one in the photo below. Just under 10hp max with a massive dip in the middle. A curve that would make a bactrian camel's mother proud:


Post lift, and with a slightly different adaptor in the exhaust header and a little adjusting of the ignition timing, the power looks much nicer:


Of course, we have no idea how much power is actually being made due to our on-going dyno computer issues. However, having had a play at Edgecumbe kart track on Sunday, I'm feeling rather optimistic. Unfortunately, the last time I was at Edgecumbe was about 8 years ago on a minimoto, so I really have no reference point. So in the absence of any actual dyno numbers, I'm going to have to rely on a dry meeting at Mt Wellington next weekend and some lap times to work out if it is as good as it looks and feels.

[2T Institute]

A superbike team here was pinged for running illegal fuel (not 98 PULP) they provided samples of the fuel, evidence of wher/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.

[wobbly]

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.

[Ocean1]

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.

A lot, (most?) of modern cars have PRV/vacuum break valves built into the tank caps.

As a fix it's not free but it's nearly so.

[RAW]

Wobbly, the KT100, With the piston at bdc if I had a hole in the piston aligned with the inlet port how do you think this may effect things

[F5 Dave]

I'm assuming the tech inspector would disqualify you (having seen them in action at last Kart meet, but without knowing kart rules), but also shake his head.

[F5 Dave]

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.

ok, something to be careful with my dirtbike which slurps 95 (I avoid 98 due to unknown Ethanol inclusion) but its not near any BMEP limits, but it does drag through sand & whatnot from time to time.

[Drew]

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.

How does that differ, from what the tank vents do at the petrol station?

[Yow Ling]

How does that differ, from what the tank vents do at the petrol station?

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 ?

[wobbly]

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".

[koba]

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

[Grumph]

thanks for that wob...it explains a few things i'd already worked out empirically.

One further question though - Injection..... i've had a lot of experience with methanol in carbs - and fresh fuel with absolute minimum water content is vital for best results.

When a speedway motor is injected, because of the better vaporisation of the fuel, fuel condition becomes less imprtant. the water content becomes pretty well irrelevant as the pressure through the nozzles will vaporise it anyway...

Do you have any experience yet that may indicate injection on 2 strokes could make the fuel condition less sensitive ?

[F5 Dave]

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.

[TZ350]

While I wait for the new dyno software so I can get back to the EFI project I thought I may as well make some progress on my Air Cooled RGV250 cylinder project. A good 30+ hp Suzuki GP125 with a power valve, ATAC chamber, 30mm Trombone and variable stinger venture and EFI of course. If I can get the water to stay mixed with the fuel (H2O fuel additive for combustion control) things could get very interesting, maybe high 30's.



The 8mm plate gets bolted to the crankcase and the RGV cylinder and heat sink bolts to the 8mm plate.



Some of the heat sink fins will be milled away so the cylinder can nestle down inside the heat sink and be mounted directly onto some copper covering the 8mm plate. The 2mm copper sheet that transfers heat from under the cylinder will also be sandwiched between the 8mm plate and heat sink. The cylinder sits on this copper sheet and the copper distributes the cylinders heat out all over the under side of the bottom heat sink.



A Wobbly designed Toroid combustion chamber will be machined into the block of 6061 alloy and another heat sink on top of that. The water jacket of the cylinder will be filled with copper chips and high conductivity thermal epoxy. Copper will be used to transfer heat away from the head and cylinder and particularly the area under the exhaust port duct to the outer (cooler) edges of the heat sinks. The heat sinks were salvaged from big old VSD drives.