ESE's works engine tuner

[Bert]

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Chambers had a lets just try and see moment..... clever though.

I think his plan is to re-sleeve an air cooled GP125 cylinder with a alloy sleeve and then plate it.

Nice plan.
Scary $$$ for plating though? or is it ??? Watching this development with interest.

So what grade alloy would you be using to do this?

And when are you going to be making a RGV100 conversion kit for a GP bottom end?
longer conrod, plated sleeve, spacer block for barrel, shiny new piston and away you go...

[speedpro]

They'll probably do it themselves, smoko, Wednesday arvo.

[F5 Dave]

Yeah I looked at that some time back. I had some 2011 free machining ally, but when I looked into it it is not suitable for welding. Which makes me think I should have chosen 6060 or 6261 which anodise well, so are probably suitable for plating. I guess. It's the Silicon or copper content that make them unsuitable for plating so if they don't weld or anodise well they probably won't plate well.

4042 is apparently the go, but not so common in NZ.

[TZ350]

So what grade alloy would you be using to do this?

And when are you going to be making a RGV100 conversion kit for a GP bottom end?
longer conrod, plated sleeve, spacer block for barrel, shiny new piston and away you go...

There is a grade of alloy that suits plating best but I have forgotten what it is, When I find out again I will post all the details.

I allready use a longer rod to get some space for my under barrel finning and for the better range of pistons that can be had with 16mm little end pins.

Definatly looking at a spacer plate like your pic with the RGV cylinder and all sorts of options but the GP might have to remain air cooled as it looks like a reed valve inlet may be the way to go.

Is that a pic in your post one of your projects?

[TZ350]

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As carbs are becoming a thing for us...............

An interesting book by Eric Gorr. http://books.google.com/books?id=4Me...um=6&ct=result

[F5 Dave]

Yeah it's a good book, go buy it, he's a decent guy.

Incidentally he gave me the learn on plating in response to a question some while back (some of which I refered to in above) as he used to work at a plating company.

[wobbly]

Both Fletchers and Ulrich do heavy wall alloy tube in 6000 series.
This plates just fine according to Grant at the platers down South

[Bert]

I all ready use a longer rod to get some space for my under barrel finning and for the better range of pistons that can be had with 16mm little end pins.

Definatly looking at a spacer plate like your pic with the RGV cylinder and all sorts of options but the GP might have to remain air cooled as it looks like a reed valve inlet may be the way to go.

Is that a pic in your post one of your projects?

nothing better than a gaping great big reed block to scare the natives off, I'm looking forward to finishing off my thing. just dropped my barrel and head off to the Dave Griffiths to sort out o'rings and a couple of other bits....

As for the photo, nope just a continuation from the series I posted up a while back.

I like the idea of alloy sleeve and plating, wish i had come up with that one before doing the steel option...

[Yow Ling]

Nice plan.
Scary $$$ for plating though? or is it ??? Watching this development with interest.

So what grade alloy would you be using to do this?

And when are you going to be making a RGV100 conversion kit for a GP bottom end?
longer conrod, plated sleeve, spacer block for barrel, shiny new piston and away you go...

Wouldnt using a big thick adaptor on a 125 size crankcase lower the crankcase compression especially as you would be putting a 100cc barrel onto it ?

[TZ350]

I like the idea of alloy sleeve and plating, wish i had come up with that one before doing the steel option......

We figure that if the sleeve was much thicker, say 50mm id and 80mm od then the inner radius of the transfer ports can be cut into the sleeve easily and the larger sleeve outside dia gives a much greater surface area for heat transfer at the liner/cylinder interface.

[TZ350]

Wouldnt using a big thick adaptor on a 125 size crankcase lower the crankcase compression especially as you would be putting a 100cc barrel onto it ?

Bucket and Thomas did some measurements........

Crankcase Compression Ratios Revisited

Primary or crankcase compression ratio is determined by dividing the full crankcase volume including transfers with the piston at TDC by the crankcase clearance volume with the piston at BDC.

The Suzuki GP125 has a crankcase compression ratio or primary compression ratio of 1.36:1

From memory the results were std GP125 470cc, just the lower crankcase 280cc and a 10mm spacer plate was another 60cc.

With the spacer plate there is a lot of room above the flywheels that can be filled to reduce crank case volume and contoured for better flow into the transfer ports.

Although, I think a lower ratio (more crankcase volume) could be a good thing in some ways.

[TZ350]

Both Fletchers and Ulrich do heavy wall alloy tube in 6000 series.
This plates just fine according to Grant at the platers down South

Thats interesting, thanks for that.........

[Bert]

Wouldnt using a big thick adaptor on a 125 size crankcase lower the crankcase compression especially as you would be putting a 100cc barrel onto it ?

Yes, not forgetting that you loose a little with the bore size. That that a good thing for high rev'ing strokes isn't it? like yamaha putting in reed block spacers to increase 1 carb to piston face length and 2 case volume. I'm sure speedpro, dave, wobbly and others (where's SS90 when you need him) will have some views on this.

We figure that if the sleeve was much thicker, say 50mm id and 80mm od then the inner radius of the transfer ports can be cut into the sleeve easily and the larger sleeve outside dia gives a much greater surface area for heat transfer at the liner/cylinder interface.

my steal insert is 50 id and 70 od, with some modifications to the transfer port alignment; but no thought went into heat transfer...

[bucketracer]

Wouldnt using a big thick adaptor on a 125 size crankcase lower the crankcase compression especially as you would be putting a 100cc barrel onto it ?

Yes your right, it would change things alright. Both the GP100 and 125 have the same size crankcase volume at 280cc, so the extra cc of the spacer plate would affect the 100's original overall ratio more than it would the 125's.

But what is the correct ratio?

Speedpro I think it was, said "The crankcase is a good place to store air/fuel and its easier to take a swig from a large mug than from a thimble" SS90 disagreed..........

Me, I think the pipe will have something to do with it all .........

[wobbly]

Case com is a very complex subject but a few rules of thumb apply.
The higher the bmep of an engine then the higher the delivery ratio, thus a larger case can store the higher volume of ingested air at a higher pressure and this is then available to the transfer ducts.
But the quality of the duct and port geometry also affects the case com required.
The smaller the case vol (higher ratio) the greater the pressure rise in the case as the piston drops - this suits compromised transfer ducts with little or no inner wall shape, as it helps force the flow around thru the ducts quicker.
Good duct/port geometry allows the use of a bigger case as they dont need a large pressure ratio across the port to initiate good flow.
Lastly is the effect of the pipe geometry, the diffuser sucks like hell on the Ex port around BDC, pulling flow thru the transfers, and it is important to match the pipe diameter ( and thus the diffuser included angles) to the transfer port/duct geometry.
Suck too hard on crap transfers and they loose directional control - giving greater short circuiting out the Exhaust port.

Thus you have a Catch22 in that you need a small case to speed up the flow, but this limits the available stored mixture, and you want to suck on the transfers as much as possible, but no so much as to loose the control of the flow direction - or to speed up the loop velocity excessively thus reducing the trapping efficiency..

One myth that needs busting here is that the bulk of the flow thru the transfers is initiated by the piston dropping.This happens in lawn mowers, not racing engines.

Pipe diffuser suction when the piston is around BDC forces the bulk of the flow volume, NOT the pressure in the case forcing flow up the ducts.
When the transfers open there is more pressure in the cylinder than in the case.
Thus we get flow reversal at the initial transfer opening point.
This also means that the transfer port that opens first - flows last, as it has the greatest flow reversal affect,down the duct.

In general, high bmep engines that by default will have good port/duct geometry, will like a case com down near 1.3:1, lower performance engines with crap transfer/duct geometry will perform best with the ratio higher, up near 1.4:1.
Thus as you develop an engine, increasing its efficiency with better porting, then this will allow the use of a bigger case, and bigger pipe diameter/vol, to work with that - the two go hand in hand.