ESE's works engine tuner

[marsheng]

One of the advantages of a belt drive and disk is the timing can be changed with RPM.
I suppose you could do the same with a gear driven disk and a centrifugal weight arrangement. There can't be much power required to drive the disk so should be feesable .

[marsheng]

I have an interesting carbon band build up on the exhaust side of the head. A clear neat semi circle, about 0.15 mm thick. Just wondering what was the cause?

http://www.marshland.co.nz/ftp/MaicoBimota/Head.JPG
http://www.marshland.co.nz/ftp/MaicoBimota/Piston.JPG

[Frits Overmars]

One of the advantages of a belt drive and disk is the timing can be changed with RPM.

By using a belt tensioner at either side of the belt and shifting them, like Porsche did on their first variable cam drive? It works, but the obtainable angle variation is limited.

There can't be much power required to drive the disk.

That's what Derbi's technical director supposed when he overruled Jan Thiel and gave the Derbi DRVE (nowadays known as the Aprilia RSA125) an 8 mm disk drive shaft. They're still counting the DNFs.
The torque required to overcome the disk friction is small. The torque on the disk drive when a rider downshifts, depends on the rider. Some have very heavy feet.

I suppose you could do the same with a gear driven disk and a centrifugal weight arrangement.

It's been done but the benefits did not outweigh the complication.


I think Flettners variable disk cover will be a better bet: more reliable, more versatile and simpler.

[breezy]

Mallory metal, now I can start putting the crank together for the sleeve engine. It needs a lot of weight to balance the reciprocating parts. Still weighting for two more lumps.

Have you considerd having the sleeve valve just to close the exhaust port as required and using a turbo or supercharger . then forget about using the return exhaust pulse and its associated problems?

[wobbly]

The carbon build up is exactly the same issue as so many people get with KZ2 kart engines.
Its why the piston always gets detonated on the boost port side.
Carbon builds up where the local temp is low enough not to burn it away, deto starts where the local temp is highest.
As the piston rocks over TDC one side approaches the head alot closer than the other
due to the rod angularity and thats why you see alot more carbon on one side - the much different MSV and temp gradient at work.
If you remember back to the old offset chamber design that Dr Erchlich sold Yamaha, it even more so had a huge MSV on one side and none on the other - and
it detoed like crazy where the end gases were trapped in the high MSV zone ( more MSV = more local turbulence = faster flame speed = advanced effective timing in that sector).

[wobbly]

Just been sent this link to a new Britten video.
Some bloody cool stickers on that bike eh.

http://www.asphaltandrubber.com/news...00s-hit-track/

[marsheng]

The carbon build up is exactly the same issue as so many people get with KZ2 kart engines.
Its why the piston always gets detonated on the boost port side.


What can I do about it ?

Thanks Wallace.

[wobbly]

The end gasses trapped in the squishband are being overheated - is the squish tapered slightly the wrong way ie
does it close down toward the chamber centre.
If not, then the only way to help is to increase the squish depth slightly by tapering outward a little - 0.2mm would probably do it.
You could then increase the width to get back the MSV.

[Flettner]

Have you considerd having the sleeve valve just to close the exhaust port as required and using a turbo or supercharger . then forget about using the return exhaust pulse and its associated problems?

Yes, possibly, but first I would like to get this crank case, 24/ 7 reed version running.
I've got the patterns finished, just gearing up to run my own furnace to cast them. Get other people involved and it always ends up a cock up.

[TZ350]

I think I have shot myself in the foot again.

After the poor showing at Taumarunui where the bike would not come back on the throttle I thought I had better run it up on the dyno with the Ecotrons Procal tuning program displaying the Gauge monitoring screen in the hope of seeing what was going on.

The bike would start and trickle out onto the track easily enough and it would fly like a cut cat when it was shown a bit of stick. But it had two real bad faults, at about 8,000 rpm it would jump around like a demented kangaroo and when it was shut off at high rpm it would not come back on the throttle until the rpm had dropped under 7,000 rpm or so.

I thought it may be to rich/lean at lower throttle settings on over run at high rpm or it needed some adjustment to the throttle blip virtual fuel pump. But no amount of Map fiddling improved things.

Sorry about the jerky video but that is the bike shaking me around as I was recording the gauges. Its not dangerous to run a bike up full tit on the dyno by yourself with one hand while trying to record video with the other - yeer right its not dangerous.

Top left gauge is rpm and it tops out close to 13,000. Top right is the TPS and the two gages on the bottom right are for the injectors. Injector 1 to the left, Injector 2 to the right.



You can see injector 1 increasing in pulse width until it switches over to injector 2 at about 8,000 rpm, just where it starts to jump about. Then Injector two stays at 1.7ms right up to 13,000 ish rpm.

Close the throttle and injector 2 stays at 1.7ms until the rpm drops back below 7,000rpm and the system switches back to the smaller injector 1 at which point the engine will respond to the throttle again.

On over run above the changeover point the engine won't respond to small and medium throttle openings but at higher rpm it will jump back into life when given full throttle.

Previously I had been wanting to get as much fuel in as possible in the shortest amount of time and I had made injector 2 as large as possible and injector 1 was much smaller and only for starting and off pipe running below 8,000 rpm. The smaller the injector the more adjustable it is with the fuel map.

Both injectors have a minimum open time of 1.7ms and what I think is happening is that the big injector is too big and even at its minimum open time it drowns the motor at anything less than near full throttle.

And the jerking at 8,000 rpm is the EFI being confused about whether to use the injector that is to small or the injector that is to big.

I think Injector 2 needs to be smaller so it gets held open over a greater range of time from say 1.7ms at small throttle openings and high rpm to 3.5ms for full throttle at high rpm.

At the moment the EFI works well with injector 1 but it has no adjustment with injector 2, its all or nothing, actually injector two is virtually full on all the time above 8,000 rpm because it can't be run any slower than 1.7ms it needs more adjustment and we can only get that by going to a smaller injector because a smaller injector would need to be held open for longer than the minimum 1.7ms.

To get the greatest range of adjustment out of a fuel injector you need one that is only just big enough to do the job. I think I have been running one that is way too big for the job and even on minimum open time it is drowning the motor on overrun.

Instead of thinking big injector to get loads in quickly I think to get best throttle response I need to think smallest injector possible that is only just big enough to do the job at max fuel demand (max torque).

Tomorrow I will swap out the big injector 2 for a smaller one and see how that goes, here is hoping ....

[Peter1962]

Wobbly, do you think that on a MX engine of 300 cc like the TM or KTM it would be beneficial to adopt a rear RV like in your current project ? To be mounted in the location where the reed valve is now. The comparison made by Jan on the reed valve derbi and the derbi equiped with a rear RV were largely in favour of the latter. I wonder if the same conclusion would be valid for a 300 cc engine that is not tuned to the extreme like the derbi was. What do you think of this ?

[Sketchy_Racer]

Sounds like a valid hypothesis there TZ350, hope it works for you. That damn EFI is a cruel beast, just constantly teasing!

[marsheng]

[QUOTE=marsheng;1130820940]The carbon build up is exactly the same issue as so many people get with KZ2 kart engines.
Its why the piston always gets detonated on the boost port side.

Just measured the compression volume. 19.5 with a 1.2 mm squish. This gives a CR of 8.4. From your calcs should be CR of 7.6, head volume of 21.8 cm3 with a 0.9 squish. I have increased the head volume this evening. Hope that works better.

Cheers Wallace

[Frits Overmars]

Instead of thinking big injector to get loads in quickly I think to get best throttle response I need to think smallest injector possible that is only just big enough to do the job at max fuel demand (max torque).

Using a smaller injector will mean injecting over a longer period of time per cycle; more of the inhaled air will be carrying fuel into the crankcase, so the mixture is already more homogeneous before it is stirred by the crankshaft. That's good.
Your remark 'max fuel demand (max torque)' put me on the wrong track for a moment. The fuel demand is proportional to the generated power, not to the torque.
But the fuel demand per cycle is, as you say, indeed proportional to the torque.

[Frits Overmars]

Wobbly, do you think that on a MX engine of 300 cc like the TM or KTM it would be beneficial to adopt a rear RV like in your current project ? To be mounted in the location where the reed valve is now. The comparison made by Jan on the reed valve derbi and the derbi equiped with a rear RV were largely in favour of the latter. I wonder if the same conclusion would be valid for a 300 cc engine that is not tuned to the extreme like the derbi was. What do you think of this ?

That 300cc MX engine will be able to produce lots of power with a rear RV or indeed with any RV. But that won't be any good for MX; modern 300 cc MX bikes are too strong already for 99% of their riders. If you want power, try an RV (or try 24/7; that is much simpler to implement on a reed valve engine). But if you want to win MX-races, work on your suspension and your throttle response.