ESE's works engine tuner

[WilDun]

Just as an interested onlooker I'm a little intrigued by Grumph's "2/4" and was wondering if he is intending it to be a 180deg or a 360deg crank. ie is he using the inner journals (360deg) or what?
I seem to remember Speedpro trying something similar.

[Grumph]

thats rob , hope to have good results , got to get me a tread mill to fix me lol

Ha - I've got skinny kids lining up to ride mine...

Will - have a look on the thread here "The sensible twin" - all is explained.

[oldjohnno]

Groundbreaking new ignition module from Bosch:

[SwePatrick]

Never seen Bosch silver - only Brisk, that is what TM sell.
But those have a silver center electrode, not a rare earth ground strap, thus only half the advantage of less voltage requirement and less shrouding.

Search Bosch F2cs on google.
just like an ordinary plug but with silver centercore and no resistor.
I have a couple at home, but haven´t tested them yet as i started fooling around with turbo

Rgds.

[TZ350]

Bosch F2cs

https://www.boschsparkplugs.net/lear...nversion-chart

https://www.briskracing.com/heat-ran...eference-table

NGK

[WilDun]

Will - have a look on the thread here "The sensible twin" - all is explained.

Thanks Grumph, I checked it out last night (went through it all quite quickly but will do it more thoroughly soon), I am a bit too focused on my 3 bucket forums and didn't know that thread existed! - so my question regarding 180 deg and 360 deg is answered. I think the Honda 125 racer twins of the sixties were 180 deg.

Sorry guys, back to two stroke business!

[shnaggs]

Maybe this has been talked about before, but why did the RSW Aux Ex ports not utilize a power valve? Was this for a reason, or was there just not enough room, or did packaging not allow such a design? Reason I ask is because I thought Wobbly mentioned about how having the Aux Ex ports opening before the main port was not ideal. In the case of the RSW, with the power valve down, the Aux Ex ports were opening before the main exhaust.

Now comes the kicker... So I was fumbling around on engmod. I utilized the RSW exhaust parameters on my profiled MX ktm 125. Obviously this was not optimised, with a massive dip down low, so I added power valves to the Aux Ex ports. Well, that didnt work so well. So I kept fiddling and could not get them to work. So i got rid of them, but lowered the main powervalve... and kept lowering it, and so on. Well now I'm in no mans land with how low the main power valve is, but engmod is showing heaps low end!!! So my question is, why did this occur, and is this at all believable? And if so...then maybe having those huge Aux Ex ports doing much of the work till later on in the rev range might be beneficial??? Just FYI I could not replicate this type of low end with a more conservative 3 port configuration, and messing around with the powervalves, soooo is there something to this???

I'm sure Wobbly, Frits or Jan will be by to school me on this

[wobbly]

Having all 3 of the Ex ports closed by a PV in effect reduces the blowdown to virtually nil.
This works OK in a MX situation, where the engine is used well off the pipe and the low PV setting reduces the really bad effect of the pipe being way to short for the rpm.
In a roadrace engine the combination of the open Aux port with the PV down in the main port, allows a usable amount of blowdown at the lower end of the powerband.
Then the PV is lifted over a fairly wide band of rpm, giving a much wider powerband ,in the range that is used on track.
The Aprilia, and many other engines using this setup,they dont have the PV all up until about 1000 rpm before peak power.

[F5 Dave]

Attachment 332386Attachment 332387

Ages ago to increase the airflow through a class legal 24m carb I came up with the idea of a 24mm venturi section in a 24mm carb that had been bored oversize. The idea was that the larger front section acted like a flow straightener and by eliminating turbulence it would allow the venturi to pass more air. Whether it really worked like that I don't know but it did allow Team ESE to make much more power with the old air cooled 125's than people thought possible for the class.

. . .

Hey Rob, this will become topical for the TF as a future mod. I had figured on doing a taper from the back of the carb. Had you tried that and dyno'd to then come up with the bore from the front approach?
Pity you are off site presently.

[Grumph]

Hey Rob, this will become topical for the TF as a future mod. I had figured on doing a taper from the back of the carb. Had you tried that and dyno'd to then come up with the bore from the front approach?
Pity you are off site presently.

Talking to him about this when he was here. He's now confident of getting mid to high 20's HP with parallel bore carbs.
When I did kev's big MB I put a venturi on the engine side of the slide - reducing the 29mm flatslide to the regulated 24mm.
Never tried it with a straight 24 or 29 but taking it down to 24 didn't seen to slow it up any...

[TZ350]

I had figured on doing a taper from the back of the carb. Had you tried that and dyno'd to then come up with the bore from the front approach?

24mm at the very front of the carb and taper bored out to 30mm at the engine end of the carb.



30mm with 24mm venturi at the engine side. Both worked but I don't have dyno results with back to back tests comparing these carbs but I did like working with the 24mm venturi on the engine side best and it would be my pick.

The venturi could be cut in half so that the carb measured 24mm at the rear and the pressure recovery part became part of the rubber manifold. If you do that make the carb side 24mm and the pressure recovery side 25mm. The small 0.5mm step is an enormous help in aligning the flow and avoiding any sharp disruptive edges facing the high velocity air stream. The small step does not seem to affect anything.

Remember someone asked MNZ for clarification on where a carb should be measured and they said at the engine end, total crap but there you go.

[F5 Dave]

Thanks Rob but that picture confusels me. It looks like a 28mm with an insert.

I'd kinda made the inlet rubber about 30mm and the TF inlet needs some space as it separates into the inlet port and crankcase reed.

I could fill that area with Devcon some.

Maybe I need a rethink.

[TZ350]

Thanks Rob but that picture confusels me. It looks like a 28mm with an insert.

AHhhh yes your right. That is a 28, should have been a 24mm OKO bored out to 30 with a 24mm insert, anyway the principle is the same and I found the 24mm venturi at the engine end was better to work with jetting wise than having the 24mm at the front of the carb.

Grumph mentioned that I was of the mind that I could make good hp with an ordinary 24, mid 20's at least, or even 30. I think that 24, 28, 32,34 or 38 won't give any more power in the engines we run because the real (or bigger) problems are elsewhere, like the transfers and exhaust flow coefficient.

Anyway Team ESE are making a 100 and another two 110's with 24mm inlet tract so I guess we will know for sure soon enough.

[F5 Dave]

Yeah,? The RG 50 with a dreadfully compromised transfer arrangement (opps, like the TF) worked better with 28 than 26 or 24 from same family.

Certainly easier to bore from the front than taper from the back.

[TZ350]

Some of the different carburetor configurations I have tried.



36mm EI flat slide smoothbore with a 24mm insert, this one worked well but I didn't have enough needles to get it working perfectly.



A 28 and a 38 with 24mm inserts. Surprisingly the 38 worked very well but would stumble if you grabbed a big handfull of throttle quickly so maybe not so suitable. After optimising the jetting the 38 didn't make any more power than the 28. The 38 flowed more air on the test bench though.

After trying a few different sized carbs it seemed like 32-34mm would be about the size that would work well without stumbling on a big handful of throttle.



By far and away my favorite was the humble 24mm OKO bored out to 30 with a small section at the engine end left at 24 and shaped into the front part of a venturi. OKO carbs machine very nicely and don't crush easily like the pot metal ones do