ESE's works engine tuner

[Buckets4Me]

What's irony about aluminium?

starts with ally head
goes to copper as it trasmitts more heat faster
then goes back to ally

round and round he goes
nobody knows where he will stop

(with a stock engine again)

[TZ350]

Well i think irrespective of the plating on the inside you should definitely gold plate the outside of the head.

YoYo, boys in the hood check out my bling bling [& so on & so forth] A few medallions worn outside your leathers, well, you could be the badest Ho talkin Homie at the track. Word.

Your just making fun of my good looks and charm.
Yes I know looks like I have excitedly run down another blind alley scattering $$$$ behind me.


I haven't given up on the copper yet.

Koba and SS90 make some good suggestions. They are worth looking at but it will take some time to digest them.

Same piston set up, 0.002" clearance, with a new piston but same type, make size Etc., as previous season. I have measured the crankcase volume before using a measuring cylinder but there are differing ideas about what constitutes the crankcase volume, Does it include the transfer ducts?

The stud idea sounds promising.The GP has a composite head gasket standard but I don't use one as I have "O" ringed the barrel. Could be the composite gasket took up some of the cylinder expansion before.

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[koba]

Didn't some old bikes use bronze heads?
Excelsior (UK) Maybe?
I wonder if there is anything to that...

Edit:
Rudge!
Four valves too!

Edit again:
Cut and paste -
The first machine to bear the Ulster name emanating from the Rudge factory was announced during 1928 in celebration of their success in that years Ulster Grand Prix. The Ulster became a fixture at head of the company's catalogue until production ceased in 1940, early versions featuring a pent roof four valve head which was replaced for the 1932 season with a radial four valve head with the option of a foot operated gear change becoming available in the same year. The valve gear remained exposed to the elements until 1937 when a simple cast alloy cover was adopted although the bronze cylinder head remained finally being replaced with a light alloy example in 1939.

Image provided by www.classic-auctions.com.



Thats some high tech shit for its day!

[TZ350]

A 250cc four valve two exhaust ports bronze head Rudge.

[Buckets4Me]

A 250cc four valve two exhaust ports bronze head Rudge.

Looks like a bucket to me

[SS90]

Bronze Cylinder head?

The last time I heard that I fell off my Dinosaur!

Come on people, if Bronze cylinder heads where any good, don't you think that they would have been used later that the 1920's

Seriously, an ally head is completely feasable in this situation, with-out the need for heat sinks (as good an idea as that was), or cylinder heads made out of "unobtainium" or any other precious metal!

Can any one here show me a japanese (or european) (air cooled) 125 GP bike that had anything other than an Aluminium head?

Personally I don't know of one.

The way that the "founding fathers" of tuned air cooled two strokes dealt with this problem, was to treat the cause, not the problem........

Now, I know that you are limited to a piddly little 24mm carb (booooo!), And this in itself will cause a hotter engine (anyone who doesn't know why needs to read a little about two strokes........)
....and, as such, you cannot increase the carb size, but there are alot of other ways to decrease your overall engine temp, (and, in particular,your combustion chamber temp,and therefore your cylinder head temp)

Tee zeee tree fiddee, from what you write, I can see you have read some of Gordon Jennings writings.......take a look and see what he has to say in regards to exhaust port duration, and cylinder head temperature......perhaps it could be considered an option to drop a few degrees (a simple task really, even though that will also lower your transfer timing if you simply use the spacer method)

Lowering your exhaust timing will also increase your torque at lower RPM's, giving you more drive out of the corners.....who knows, that might lower your lap times too!

Who many P.S does the engine currently have, and more importantly, how many NM...... (and at what RPM).... this is THE REAL TEST of an engine (afterall, you cannot measure P.S (or HORSEPOWER), you can only measure torque, then divide it by the RPM and multiply it by 5252 to get P.S (or horse power)

Correction factors not withstanding.

I digress....

Basically, it seems that you have exceeded the thermetric efficency of the materials of your engine (perhaps because of the fact that you are using calculations (port timing and exhaust designs) that where developed for modern (read liquid cooled) engines.

That's how it seems to me.

personally, I would never exceed 191 (MAXIMUM) degrees exhaust, and 131 transfer on an air cooled engine

I would opt for something like 188 and 131..............

I'm not trying to knock all your hard work Teee Zeee, just trying to encourage you too see it through to the end!

[TZ350]

Certainly a lot to think about here.

I have come to understand that tuners often spend much effort tuning their motors up with ports and pipes etc., then have to reduce the power output by tuning their engines down with a rich mixture so that the engines waste heat from that extra power does not overwhelm the (air) cooling system.

From this I understand that by leaning out the over rich mixture I will be able to use more of the power my motor can make from the modified ports and pipe if I can improve the cooling system.

To improve the air cooling system on my motor I need to think about the total distance from the combustion chamber surface to the fins. Ie the total mean thermal path and how to shorten it.

Port timings I have been using.

Short Track Ex opens 86 ATDC 188 Duration.
............Trans opens 116ATDC 128 Duration.
or.........Trans opens 114ATDC 132 Duration. to widen the power band.

Short Track Ex opens 83 ATDC 194 Duration.
............Trans opens 115ATDC 130 Duration.

Taupo Track Ex opens 81 ATDC 198 Duration.
.............Trans opens 114ATDC 132 Duration.

Started with a pipe from a RG250 then modified it to the RM125 specs found in Gordon Jennings book. (A list of books that can be down loaded from the net appear earlier in this thread).

Interestingly the port specs below are much like what you sugest.

Suzuki RM 125 Ex opens 86 ATDC 188 Duration.
...............Trans opens 114ATDC 132 Duration.

Honda RS 125 Ex opens 86 ATDC 188 Duration.
................Trans opens 115ATDC 130 Duration.

It might be Gordon Jennings et.,all and the approch I have followed from them is a bit old school.

I see current trends like The Wobbly port/pipe specs are for shorter durations. ie., Ex opens 87.5 ATDC Trans 116.5

Speedpro has just finished a Wobbly spec port/pipe setup and his bike runs realy fast.

I don't know why a smaller carb would cause a two stroke to run hotter, will have to find out.

This is buckets, having a go, finding out, and trying it out is all part of the fun, with my old TZ I could never have afforded to experiment like this.

.

[F5 Dave]

I don't think one can just throw around port timing numbers with much sense. Ok here's some; I used to run 202deg ex. Worked well on that particular engine.

Taken out of context it means nothing. No talk of where peak power is or spread, or other constraints of the engine, rings etc.

TZ I would be careful about going down the lower transfer path. MBs for example have quite okish transfer ports. GPs are a little less cool.

2thou clearance is quite loose, but entirely appropriate for this engine I'd say & what I ran on the aircooled H100 with no drama & no seizing, wear or excessive overheating. But that was a lowly stressed low revving midrangey 18hp aircooled 100cc.

[F5 Dave]

........ Now, I know that you are limited to a piddly little 24mm carb (booooo!), And this in itself will cause a hotter engine (anyone who doesn't know why needs to read a little about two strokes...........

Well it will greatly increase the intake velocity as the revs go up, but I can't see why it would increase engine temperature, one could easily make it as rich as you wanted & in fact with less charge being burnt there is less energy to dissipate. They of course came with 24mm as std.

I'd consider myself well read in this area, but that's not something I have come across.

[Bren_chch]

[Skunk]

Me too...

[SS90]

Well it will greatly increase the intake velocity as the revs go up, but I can't see why it would increase engine temperature, one could easily make it as rich as you wanted & in fact with less charge being burnt there is less energy to dissipate. They of course came with 24mm as std.

I'd consider myself well read in this area, but that's not something I have come across.

Quite right on the fact that they came with a 24mm carb..... and this is a perfect example.

I am going to assume that the original engine, due to the fact that it did not have a) an expansion chamber
b) "squish band head"
c) high compression
d) a "gas flowed", or "chamfered" intake web
would only rev to say....5000 RPM (or thereabouts)

a 24mm carb would be adequate, given the fact that the engine does not require large amounts of air, and it would run as designed.

Quite nicely actually.

Now, the engine is really spinning (11,000 RPM?) particularly at high RPM, the pumping losses (horsepower absorbed by the action of operating the crankcase "pump") go up exponentially (regardless of the fact that the chamber is "helping" scavenge, and decreasing this loss a little)

This is really unevoidable, but, in this case is compounded by the fact that the carb is simply too small for a 125cc engine spinning at 11,000 RPM

Think of it like this.

If you are cycling (possibly to the pub), and you are breathing only through your nose (not getting enough air), you will overheat, as your "pumping losses" are increased.

O.K, the human body is not a pump, but I think it's a nice example, as we can all relate......

If you where then to start breathing through your mouth, and allowing your body to get more air, you then become more energy efficient, and you will in turn run cooler.

An engine (particularly a two stroke, as you all know is just a pump), if you restrict the amount of intake ( to a point that is too far below optimum), efficiency will go down, and temperature will increase.

I think you would all agree that a good size would actually be something closer to 29mm - 32mm (max), and, as you pointed out a smaller carb would increase velocity as revs go up, but as velocity increases, so to does the temperature of the air fuel mixture....not always a good thing.....

I believe if he did away with the whole disc valve set up, and adapted a reedblock to the intake port, then this would also help as the negative pressure under the piston will control the intake as and when the engine needs it.......but, my god, I don't want to kill the guy with trying out theories that may only slightly alleviate the problem, or not even make a difference

The little GP125 has Asthma..........

And, this is unevoidable, because it's in a semi "controlled" class.

I agree also with the notion that it is aimless to talk about port timings "willy nilly", as, in reality, as you pointed out, every single design is different (reed valve, crankcase induction engines (Mb100 for example) are quite different in what they run "best" at in regards to port time areas.



I did, however, ask where is peak torque was, as that is quite important..........

The only reason I mentioned it was to point out that larger exhaust port time areas increase cylinder and cylinder head temperatures, and I want to suggest that if the engine was a little "down tuned" ( A little less peak power, and more torque in the lower RPM), ( But can you consider that "Downtuning", or is it really UP tuning...... it's all about perspective I guess) then the engine will run cooler, and be alot easier to ride.

[bucketracer]

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SS90 I see some very confident statements being made and it would be a mistake I think, for any one to judge TZ's understanding to harshly. I suspect, just because he listens to you and considers what you say, doesn’t mean he is without any clues himself.

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[TZ350]

A preview of Kevin Camerons book “Sportbike Performance Handbook” can be found here:-

http://books.google.co.nz/books?id=L...esult#PPA81,M1

It's worth a look.
.

[TZ350]

The little GP125 has Asthma..........

And, this is unevoidable, because it's in a semi "controlled" class.

I did, however, ask where is peak torque was, as that is quite important..........

Quite right about the Asthma.

The Std GP125 from memory is 13HP or 15HP (depending on who you listen too), at 8,500 Rpm and peak torque at 7500.

With the limitation of a 24mm carb I am looking at a peak Rpm of 10,000/10,500 and peak torque around the 9,000 mark and have tried to adjust the time area values of the ports to suit these constraints.

.