ESE's works engine tuner

[Grumph]

Does anyone here know of a source for round bar in 300M steel or E4340AQ steel, something bigger than 16mm diameter
so I can have a go at making some steel rods. I am after like a 1m length or what ever they will sell, as long as I don't have to buy a mill run.
Thanks
Neil

My first call for that stuff used to be Atlas Steel here in ChCh but they've changed hands and dumbed down...still worth a call.
I have also used Special Steels & Metals Ltd again here in ChCh.
There must be someone in the Hamilton area, I know a guy who works for Les DeLacy who makes a lot of crankpins for classic motors. Les' core business is aircraft engineering for which they need access to the good materials...

[speedpro]

Heat Treatments might be worth a call as well. They have a huge machine shop making interesting stuff so may have a small pile of useful steel.

[teriks]

The MB40 engine has 190°/130° timing, like you would expect from any decent two-stroke.

Some people run them close to 200° exhaust timing nowadays with good results.
Modified in the simplest way, shim under the cylinder.

I don't recall the rotary inlet timing of the hollow crankshaft shown below but it will probably be something like 140°/60°. That may seem tame and it is; this is not a high-revving engine . It doesn't exceed 35000 rpm and then the mean piston speed is only 23 m/s. Compare that to 26,3 m/s for an Aprilia RSA (or 54 m/s for a Ryger).
Anyway, I feel that this kind of shaft rotary inlet for model engines is a fashion thing more than anything else; I wouldn't be surprised if simple piston port induction would perform better (it would certainly flow better).

I dont run the shaft intake myself, but have 138°/65° on file for that one.
Piston port, now that's an interesting thought, in my opinion mostly from a friction point of view.
Might have to visit that idea in Engmod...

[wobbly]

Does anyone have a PWK38 NON Airstriker carb that i could use for a dyno test on CR125.
Both PWM and PWK carbs are legal for SKUSA racing.
No one uses the old longer PWK so thats a good reason to try one.

For anyone still wondering about steps ( or not ) in the Ex or if a race plug is worth buying then this dyno sheet should
give you the idea.
Green is a straight round spigot with steps, brown is a CNC oval/round transition,red is the same transition but replacing the R7376-10
plug with what is commonly used alot in USA, a BR9EIX.
The transition needed 2 jets leaner to hit the same 650*C egt in the tests.
It might cost 4X the price but the race plug is the cheapest 1Hp gain in a box stock engine you can buy.

[F5 Dave]

Sorry just a 35 but I just stole the turret to fix a damaged needle jet on my 39A/S, same part it appears.

Wow that is a pronounced change in the transition modification. Don't suppose you have a before & after picture?

Why do you think there is an improvement with the racing plug? Appears after 11k onward where combustion pressure comes to a peak but continues well after indicating that it could well be a time of combustion product.

My experiments on a 40mm bore showed no improvement in my bike & 1hp on a mates which had a super flat & shrouded chamber, both were around 13hp at 12k back in the day. Recent tests have been similar but my experience with these plugs is minimal. Perhaps the tiny bore size underrepresents the improvement potential. Clearly in your case it is well worth it.

[wobbly]

Sure - here are the two manifolds.
The plug result just confirms that having a rare earth fine wire center AND a fine wire platinum ground electrode makes the ignition
power required to initiate ionization under heavy compressive loads is way less with the race plug , when compared to the simple iridium
plugs cast iron plank hanging off the side of the body.
The dyno doesn't lie - check the overlay at the bottom of the curves, near as damn it identical in the range where the plugs efficiency makes no difference.

[speedpro]

The plug result just confirms that having a rare earth fine wire center AND a fine wire platinum ground electrode

Funnily enough that is the configuration of the standard plugs in my car. Makes you wonder.

[F5 Dave]

Thanks. So the barrel was a convenient oval shape, I was expecting there to be some bored into the port to get to that point. But you said there was a step so that looks like a good comparison. . . . And largely like my barrel once I'd welded a new tunnel area in exposing the oval and leaving a step top and bottom, next test was to be a transition. Those results make me excited.

One wonders how far away from the piston this transition should be and effectively start the header.

[husaberg]

Dunelt again

seems a simple way to have No dirty crankcase nor any need to seal of the crankcase.
So if it was set up as a single without a wet crankcase would the inlet mixture actually be compressed twice.
once under the piston then again prior to entry into the transfers?



Plus an internal drawing of the Garelli twingle

[jonny quest]

Wobbly, who sells yhat manifold?

[wobbly]

This 125 engine only just cracks 40Hp so isnt really stressing the conventional ignition that much, but as soon as things get tough
the good plugs configuration makes a difference.
A low bmep engine with rezo spark would as you say make bugger all difference, as it simply doesnt need the extra grunt.
When you really stress the hell out of the system, as in the Aprilia where simply changing to a bigger coil made more power, or when running
big com on rich methanol engines the power difference can be really worthwhile.
Ages ago my best TM125MX kart engine went up 2Hp to around 50 when changing from a BR10EGV.

The manifolds for the 2001 CR125 I had 3 very different ones CNC made direct off my solid models.
I modified the best one by hand grinding,then got that digitized and remade properly.
Not a cheap exercise doing small runs and one offs, but I was a few favours owed by a CNC workshop manager.
But when you want to win a box stock World Champ class thats what you need to go to, the customer is smiling ear to ear at the moment,
but hasnt got the invoice yet.
Ive been thru 50L of C12 at $8 a litre on the dyno and I aint finished.

Still searching for a 38PWK - anyone

[Haufen]

Still searching for a 38PWK - anyone

I should have one somewhere that you can borrow, but it's located in Europe. I have no plans with it for the next 2 month or so, but I have no idea about shipping time and cost to NZ. But as long as the package is not too heavy, it's not overly pricey sending around the globe as far as I remember.

[jonny quest]

I figured it was one off... i have a couple of CNC machines. .. but sometimes it's cheaper to just buy them.

[F5 Dave]

Is there any rule of thumb for where the transition should be from the piston face?

A manifold could be as short as 50mm, but a PV arrangement could be considerably longer and at what point does one start the header or delay the process by doing transition in the manifold?

[husaberg]

I was looking for a short closed 54mm piston with a low crown height and came across this.
Its an old McCulloch
look the closed gudgeon /cover any ideas how this is done?
It appears to be missing one or only on one side.
http://www.ebay.com/itm/McCULLOCH-CH...-/360321382696