ESE's works engine tuner

[TZ350]

Hi everybody, my name is Juergen, I'm from Frankfurt (Rhein-Main Area) in Germany.

Hi Juergen, welcome.

[Frits Overmars]

everyone talks about the axial angle on A,B and C but never any mention of the axial for the roof and floor of the aux. got any suggestions ? tried to look at the rsa but couldnt really tell much from the odd angle photos ive seen

The roof axial angle should be about 20° down; the floor could use a bit more downward angle, but that would land you in the A-transfers, so you'll have to becareful there.
The radial position angle of the RSA's aux. exhaust ducts is quite radical; past mid-cylinder. But the radial direction angle is less severe.
The drawing below shows that the flanks of the aux ducts start with 20° less than the radial position angle, irrespective of the radial position angle that you may choose. And don't overdo it or you might get massive short-circuiting from the A-ports to the exhausts, even when using RSA-type closed-end piston pins.

[Frits Overmars]

As per good advice I got the EngMod software paid by my wife (with the basic idea better to simu some pistons to dead rather than buying new ones).

Hallo Jürgen, herzlich willkommen. That certainly was a good advice. Now I could use some advice from you: where can I find a wife like yours? Has she got any sisters?

is a TL for the pipe of 950mm too long for max. power at 10500 rpm and 130 tr and 200 ex timing? The power / torque curve shape looks not too bad with having max power at 11.000 rpm but than going down fast (even with playing with the ignition and AFR).

The tuned length is in the neighbourhood; maybe a bit on the long side. Long pipes will force you to run a late ignition timing and/or a lean mixture if you insist on reaching a certain rpm level. But I suspect that the main reason for the power collapse after 11.000 rpm maybe the blowdown time.area. Short-stroke engines tend to suffer more than average in this respect.

[wobbly]

950 pipe will work fine, but if you are getting deto then the Comb eff is too high ( around .85 to .88 in big bore RZ ) the stinger is too small
or too much ign timing.
12:1 AFR is normal, and you can only change this if you are using a solenoid powerjet over the top.
130 transfers is very high - I would be looking to increase the width and reduce the height, plus make Aux Ex port top edge as big as possible
+ 72% width at the top of the main.
As Frits says the big power drop is likely blowdown related, do you have a big rise in pressure in the transfers as they open.
Here is RZ400 dyno curve for road racing with 955 pipe

[speedpro]

.. Yes Auto ignition and I think you are right about the EFI creating a weak mixture in the transfers.

Auto ignition - yes, weak mixture - no.

The problem as I understand it is that because the throttle is closed there is hardly any crankcase compression. As the transfers crack open, even though there was not a lot happening on the previous power stroke and not much exhaust to be spent, because of the minimal crankcase pressure there is an amount of exhaust blown down the transfers. This mixes with the fresh charge. Eventually this mix of old & new makes it's way into the cylinder where it doesn't do a particularly good job of scavenging the cylinder, is trapped as the ports close and then compressed. This mixture of combustion products from the previous cycle and fresh mixture is prone to auto-ignition, which as I said is worse for methanol. I don't know exactly why but guess it's due to the chemical composition of the gases and a bit of heat.

Changing the ignition timing has no effect as it isn't the ignition spark that ignites the mixture. Changing the fuel ratio "might" have an effect but as the unburnt gases from the previous cycle remain in the cylinder so will the problem remain.

I think Frits suggested somehow lowering the transfers and therefore blowdown which could have a positive effect.

Didn't Honda deliberately use this characteristic in a 250cc Paris-Dakar type bike?

[Drew]

What Speedpro is saying makes sense, but lowering the piston crown temperature (by running rich and backing off timing) reduces det (pre ignition in old speak?) I thought.

Oh yeah, please read all my posts as questions rather than facts. I am perpetually ignorant and have a mongrel habit of blending several pieces of unrelated info together.

[wobbly]

Do some study - Deto and PreIgnition are completely unrelated phenomenons.

[speedpro]

Detonation as I understand it - The regular ignition event starts the process of combustion. This process is not instantaneous but involves a flame front burning it's way through the mixture. As this happens heat is created which raises cylinder pressure. This heat is radiated to the remaining unburnt mixture which is also heated by the rising cylinder pressure. Detonation is the event that happens when the rising heat and pressure from the advancing flame front gets to the point where the so-far unburnt mixture attains a state where it ignites spontaneously rather than as part of the flame propagation of normal combustion.
Reducing temperatures will of course reduce this tendency as will concentrating the mixture to be burnt in a smaller space and also increasing the flame propagation rate, typically for our motors by keeping the squish tight which concentrates the mixture and also creates turbulence by squishing(get it? - squishing) the mixture in the squish band area into the chamber at something like 30m/s. The small amount of mixture remaining in the squish area is cooled by the very close proximity of the piston and head and therefore is less prone to detonation, or even combustion which does not help emissions.

Preignition is exactly what the word implies. Prior to the regular ignition event there is something that starts ignition prematurely. Typically I'd imagine something like a hot valve or bit of carbon or possibly an overheated spark plug.

[husaberg]

Do some study - Deto .

Didn't Mr Thiel eliminate a lot of the Deto issues with the Aprilia by making the head casting waterways thinner there're by exposing them to better coolant flow.
Maybe TZ350 head doesn't have enough water flow
Seriously though, Rob what are you using to monitor you fuel mixture.
Someone brought up a few pages back that aircoolled two strokes are petrol cooled.

[peewee]

And then test it for leaks. Water inlet in the back - nice. Is that a later CPI like a Wampus or something?

no its one of them cp honda cylinders. cant recall the name. just used it for illistration puposes to show the bubble around the aux tunell

[peewee]

Peewee, I like the look of that Japanese handpiece.
.

i think i mentioned the head is japan but the handle was from a unknown maker. turns out i guess cc makes the handle. well the handle didnt even last 30min and the bearings and shaft inside were flopping around like mad so its on its way back to cc. my other 90 handpiece from germany has been going strong for a couple years now and zero problems. ill let you know how this turns out as im not real happy. im basically on the other side of the country from cc so ill be out of commision for about 2weeks while this gets sorted out. ya i can use my bigger 90 but that small headed one worked alot better in these small cylinders.

[seattle smitty]

You're in the States? I had good luck with everything CC Specialty sent me, but that was all in the Seventies . . . .

Detonation and pre-ignition: I once disassembled two dead Datsun L16 engines, each of which had one holed piston. I kept those two pistons for decades as show-and-tells because one was a perfect textbook example of detonation (sharp-edged, broken hole in the crown) and the other was a perfect textbook example of pre-ignition (hole with melted edges, other melting at piston edge and ring lands). Sort of amazing to get these at one time. When I moved last year, I gave them to the local high school auto shop teacher.

[TZ350]

Attachment 306944 Pumper Attachment 306943 EFI

EFI still detos like crazy especially on over run.

I thought the problem was "auto" ignition caused by the mixture in the transfer ducts being heated by a burst of hot exhaust gas overcoming the weak pressure in the case/duct momentarily before it finally makes it's way into the cylinder where it is polluted by burnt hot gases before being compressed at which point it autoignites.

Detonation was not a problem with the carb and 3D ignition map until well past 12K rpm.

But .. Yes Auto ignition and I think you are right about the EFI creating a weak mixture in the transfers so I intend putting in some effort to get the timing of the injection squirt to coincide properly with the transfer port open time.

When I shut the EFI beast off at 9-11.5K rpm the deto sounds like a swarm of very angry bees.

Auto ignition - yes, weak mixture - no.

The problem as I understand it is that because the throttle is closed there is hardly any crankcase compression. As the transfers crack open, even though there was not a lot happening on the previous power stroke and not much exhaust to be spent, because of the minimal crankcase pressure there is an amount of exhaust blown down the transfers. This mixes with the fresh charge. Eventually this mix of old & new makes it's way into the cylinder where it doesn't do a particularly good job of scavenging the cylinder, is trapped as the ports close and then compressed. This mixture of combustion products from the previous cycle and fresh mixture is prone to auto-ignition.

Hi Speedpro, I agree with everything you say but "weak mixture - no", well not in this case because this engine runs well with a carb but not with transfer port injection EFI so the problem must be with the EFI or at least with the way I am trying to use it.

Remember with a carb all inducted air has fuel mixed with it but with EFI this is not necessarily true. The problem with EFI and transfer port injection is that as the rpm gets up, a lot of air can get through the port but there is not necessarily enough time to inject sufficient fuel into the air stream.

I think that its becoming obvious that with transfer port injection, matching the timing of the injection cycle to the transfer port open period is vital.



The way I see it.

If the injection cycle starts to early a bulk amount of fuel simply loops around with the initial scavenge air and is lost out the exhaust port. Also if the injection cycle ends to early there will be a lean fuel patch. So correctly timing the injection end point is vital.

If the injection cycle is longer than the transfer port air flow period then some of the necessary bulk fuel for the correct air/fuel ratio is left waiting in the transfer duct and is lost on the next cycle along with the initial burst of scavenging air that purges the cylinder.

Adding more fuel (bigger map number) won't do any good because that just lengthens the injection cycle and more fuel is wasted. With a bigger map number no more fuel gets trapped in the cylinder than before as fuel injected before and after the transfer port opens/closes is simply left in the transfer duct waiting to be blown out the exhaust port along with the initial scavenge air. Bigger injectors are slower injectors so longer injection cycle there too.

With transfer port injection it looks like timing is critical and the length of the injection cycle has to match the period that there is bulk outward air flow in the transfer duct and I guess this will be significantly shorter than the transfer open period.

[SwePatrick]

Attachment 306944 Pumper

With a pumper carb this engine reliably made 28hp at 12,250 rpm, with EFI, 24hp at 11,500rpm is the best so far and the EFI is short about 1,000 rpm.

Hi,
A little question, Have you considered loss of 'inertia' in the fresh mixture entering crankcase as a factor of loss of power?
Now with 'dry' flow your inertia is way lower and doesn´t fill the crankcase as a carburated engine does.

Rgds

[F5 Dave]

With a set amount of energy it must take a little to suck and drag along that extra weight of fuel from a traditional carb, so the gain in inertia has to be paid for. But an interesting idea and a bit off normal thought process.