ESE's works engine tuner

[F5 Dave]

But then again, you have Never worked in the industry....

Any reason for this mind numbing advise?

How do you know I've never worked in the industry? I could easily have spent a year as a grease monkey changing tyres & wheel bearings on flogged out dirtbikes, or reassembling exploded GN250 motors. But I had better things to do. Like spend my working day thinking about tuning 2 stroke engines. & the evenings with the dremel. Don't have much time for that these days.

I didn't offer my comments as 'advice', I was stating that that was my practice & had worked ok for me, at least in terms of reliability. If Wobbly had come back & said for instance 'Steel cages create more drag than resin no matter what they were run in' then I would listened because I respect his advice.

But I doubt that is the case as the rest of the gearbox runs steel cages immersed in oil. The difference of course is the speed of the shafts & I have no quantifiable way of measuring that this side of consecutive dyno runs with a lot of work in between.
Either way I have gleaned a lot more or challenged my own understanding since Wobbly has been contributing to this thread.

SS if I have numbed your mind then I'm sorry, clearly your clear thinking incites have been lost on me, someone who shamefully has never worked in the industry. Must be because I'm stupid.

[marsheng]

I now have sets of FXR 150 cam sprocket verniers adjusters for sale. I do an exchange with your sprockets as they need to be drilled and slotted for the verniers.

Each tooth on the sprocket is 10.6 degrees. The verniers split the 10.6 degrees into 10 equal measurements. The disks labelled 0-5, 0 being 0 degrees and 5 being 5.3 degrees. To get from 5.3 to 10.6, you advance the sprocket 1 tooth and put the verniers in back to front.

The verniers can be changed without removing the sprocket from the camshaft. Very easy.

The exchange set is $85

[F5 Dave]

No disprespect, but keep your Feeelthy 4 stroke parts out of this fine 2 stroke thread into some other Diesel thread.

We don't need no Steekin camshafts.

[timg]

I now have sets of FXR 150 cam sprocket verniers adjusters for sale. I do an exchange with your sprockets as they need to be drilled and slotted for the verniers.

Each tooth on the sprocket is 10.6 degrees. The verniers split the 10.6 degrees into 10 equal measurements. The disks labelled 0-5, 0 being 0 degrees and 5 being 5.3 degrees. To get from 5.3 to 10.6, you advance the sprocket 1 tooth and put the verniers in back to front.

The verniers can be changed without removing the sprocket from the camshaft. Very easy.

The exchange set is $85

Hope you've still got the rest of my set We must get around to finishing the job one day....

[koba]

One thing some have overlooked here, is that plenty of us know fuck all about stuff we do work on in our chosen industry as well.
But back to more useful time wasting.
C4 isnt just the end float - its the total radial clearance.
Usually its designed in for where the bearing is pressed onto a shaft ( expanding the inner race) and pressed into a housing ( crushing the outer race).
In our application it also gives the case the ability to move around due to heat expansion and not take up all the end float.
Floating at least one inner race allows the crank to self center and reduces rolling friction heaps, doing both with a set amount of total end movement is even better.

My old RG 150 engine had one journal that was a very loose fit, I was never sure if it was a design aspect or simply due to wear. I still don't know but what I have learnt is that I probably shouldn't have used bearing retainer on it...

[husaberg]

Now if I can do something about the 4.5kg gas tank and get my new pipe on there I might be down to around 85kgs.

Are you planning to gut the tank?
An easy couple of KGs in there.
I used gut the tanks and use the std oil tank as a fuel cell good for 10 minutes at least.
I just rammed a lawn mower accessory fuel tap in it. It also helps to keep the slosh factor down when running a light fuel load.
Be aware though I no longer work in the industry.
So my suggestions may not be SS90 approved.
Then again John Britten was a property developer. He came up with a lot of his innovations like the cats cradle method for the carbon fibre and using plywood sheets as per the blueprints for the crankcase patterns because he had less preconceived ideas of how it should be done than some who work in the industry
RIP John.
Hard to believe it will be 16 years this September.

[TZ350]

STA or Specific Time Area, (Port Time Area) is at the heart of 2-Stroke port timing design.

For what its worth and as I understand it. How to determine the STA numbers you have.

Mean open Port Area is the effective port aperture seen when the piston is positioned half way in terms of crank angle between the port starting to open and fully open.

For an Exhaust port that starts to open at 80 deg ATDC and is fully open at 180 deg ATDC. Then the mean port area will be the area of the port uncovered by the piston with the crank angle set half way between 80 and 180 ie, at 130 deg ATDC.

The rough rule of thumb is that this exposes about 70% of the port window, rod length and the bore/stroke ratio influence the actual amount.

The units for STA numbers are Time Area per Unit Displacement or “sec-cm2/cm3”

Derived by dividing the Mean-Port-Area in “cm2” by the cylinder volume in “cm3” and then multiplying it all by the time in seconds “sec” that the port is open (time of total duration).

The number of revolutions in one second = RPM/60

The total number of degrees the crank has turned in one second = (RPM/60)*360 or RPM*6

Finding the Time in seconds of the Total Port Duration. = Total Port Duration / (RPM*6)

Your STA = (Mean Port Area / Cylinder Volume) * Time of Total Port Duration

After measuring Yamaha’s TR3 GP racer and as many other good racing engines as he could using only graph paper, compass and a ruler. And doing the “(Mean Port Area / Cylinder Volume) * Time of Total Port Duration” math, Jennings came up with these numbers and called them Port-Time-Area.

Exhaust 0.00014 to 0.00015 sec-cm2/cm3
Transfer 0.00008 to 0.00010 sec-cm2/cm3
Piston Port Inlet 0.00014 to 0.00016 sec-cm2/cm3
Rotary Valve Inlet 0.00018 to 0.00019 sec-cm2/cm3

In his ground breaking reveal all book that showed the budding tuner how to modify their own cylinders to get GP like porting.



Jennings didn’t give a number for Blow Down. And for that reason, I think the importance of the “Blow-Down-Time-Area” and its affect on power output was largely over looked by the old style home tuners.

Bells book with its useful list of port timings for various engine capacities and RPM was also a blessing and a curse as it also didn’t emphasis the importance of blow down. It was great to see what the ballpark timings were, but too many tuners just used the numbers blindly.

With the result cylinders were packed up with spacer plates to get the transfer timing numbers right and the inlet and
exhaust was then ported to match their own set of essential numbers found in Bells book without much regard for blow down area.

Whether you used Jennings Port-Time-Areas or Bells numbers for the inlet, transfer and exhaust the end result was that the essential Blow Down Time Area was often overlooked and a lot of the old engines were less successful than they could have been.

Port timing by itself does not mean much, its the STA numbers that are important.

Early Honda RS125

Low and wide for the transfers is the trick to getting good Blow-Down STA numbers.

Gordon Blair after studying many 2-stroke engines and their behaviour developed a number of formulae that covered the various ports. The beauty of these formulas is that they allowed the designer to start from a target RPM and BMEP or Power-Output and use a computer to crunch the numbers.

Blair called the results of a port time area calculated by his formula based on a specific rpm and target power output, a STA or Specific Time Area for that design criteria.

Blairs STA numbers for a GP racer turning 11,500rpm and producing 26.5kW at 11 Bar

Exhaust 0.000162 sec-cm2/cm3
Blowdown 0.00113 sec-cm2/cm3
Transfer 0.0086 to 0.0185 sec-cm2/cm3
Piston Port Inlet 0.0162 sec-cm2/cm3

Blairs calculated STA results and Jennings Port-Time-Areas are both physically measured in the same way. = (Mean Port Area / Cylinder Volume) * Time of Total Port Duration. The difference is that Jennings very cleverly figured out what the Factory was up to and Blair developed a method of predicting what is required.

Even the basic CAD type programs that use STA as a basis for getting the ports in the right place for the rpm,power needed and swept vol are hugely better than the old references.

A handy (and cheep $16 USD) Porting Calculator from:- http://www.porting-programs.com/ it is based on Blairs and Jennings work. Use the Blair data for STA and blowdown required for a selected power output.

Kel gave me this link to Blairs very interesting book. www.prme.nl/download/engine-1.pdf

The decade pages from p80 have link collections, links to Jenning and Bells books can be found there somewhere.

[ac3_snow]

Cheers for the advice re bearings, I will get to that some as soon as I have the spare $ and time to pull it down again. I was only aware of the c3/c4 clearance when I brought that last bearing and asked specifically for c3, I have no idea what the others may be, I simply took in the old ones from the original TF and asked for new versions.

Dave: its a 1991 CBR250RR (MC22), is fairly wide, will let you know how it handles after next weekend.

The standard roundslide mikuni carbs have three small holes in the bottom of the inlet trumpet. one is blocked by a brass ball, the middle one lets air through into the main jet(?) and the third one is a little smaller, should this third one be blocked? I suspect it somehow helps with the pilot jet operation but mine appears to be blocked. Below is a pic not of my carb but just to show what I'm talking about.

[husaberg]

Kel gave me this link to Blairs very interesting book.

www.prme.nl/download/engine-1.pdf

What about Fleck , Hiroshi Naito (1971) and Robinson in regards to STA

http://www.suzuki-rg500.com/water.htm

WATER INJECTION
By Randy Norian
SAE paper 931506, expanding the torque curve of a Two Stroke Motorcycle race engine by exhaust water injection", by Robert Fleck at QUB. In this paper, they built a simple system to inject water into the headpipe of a 125cc test motor and recorded power gains of up to 24% in the lower midrange. I decided to copy their setup and was able to reproduce their results on the dyno. After that, I decided to built a usable system that would function smoothly on my streetlracebike.
But first, some numbers.
Fleck recorded pipe temps at several points along the exhaust pipe. In the diffuser, without water injection, he recorded gas temps rising from 425 deg Cat 9000rpm, to 510 deg Cat 10800 rpm.
With the water injection active, the same sensor recorded temps of 150 degrees Cat 9K RPM, rising to 420 deg Cat 10800 rpm.
Lets go back to the equation for tuned length.
If we consider a stock RG500, this distance is about 84cm, (33 inches) and Eo is 188 degrees. Using Vs of 1700 fps, this formula predicts a peak power RPM of 9684 RPM. This is a pretty good estimate, as my bike peaked at 9500 rpm in stock form.
Now we consider Vs with water injection active, let’s say we have a mean 200 degreee C drop in gas temps. If we use Vs of 1700 fps with no water, this figures to a new Vs of about 1430 fps with water. Plug that into the equation for tuned length, and our same exhaust pipe is now tuned for a peak of 8150RPM. So we have been able to shift our peak power down almost 1500 rpm, by injecting water. Obviously, this will reduce the peak rpms of our motor, so the trick here is to turn off the water at some point and let the engine rev out normally on top.
If we were able to cool the pipes all the way down to room temperature, the stock Gamma would have a peaking RPM of just 6270 RPM. Clearly, pipe temperature has a huge role in determining the rev range of a pipe/port combination.
Controlling pipe temperature is an effective way to alter the tune of a 2 stroke

I note Aprilia used use carbon sleeves to raise the temp of the pipe for top end

[kel]

STA or Specific Time Area, (Port Time Area) is at the heart of 2-Stroke port timing design..

Nicely done TZ

[kel]

What about Fleck and Robinson
Controlling pipe temperature is an effective way to alter the tune of a 2 stroke

The Robinson book was a waste of money, I still have it and still looks like new. Bells book fell apart years ago from over use!
The pipe temp cant be changed quick enough with water injection, I posted the Honda article a couple of months back, basically they stated the gains to be had could be easily realised in other areas so the water injection was dropped.

[husaberg]

The Robinson book was a waste of money, I still have it and still looks like new. Bells book fell apart years ago from over use!
The pipe temp cant be changed quick enough with water injection, I posted the Honda article a couple of months back, basically they stated the gains to be had could be easily realised in other areas so the water injection was dropped.

Did you follow the link?

Honda didn't really follow through in my opinion.
The cooling medium need not have to be water.

Remember rotary valves were at least 50 years old when Walter Kaaden reinvented the idea.
I did try to read the article but it wouldn't pop up .

Had the same trouble with the bell book to.
But the Robinson book does cover STA and if you read between the lines it does share quite a bit.
it even had a program for calculating STA.shame its in BBC.

[gav]

I now have sets of FXR 150 cam sprocket verniers adjusters for sale. I do an exchange with your sprockets as they need to be drilled and slotted for the verniers.

Each tooth on the sprocket is 10.6 degrees. The verniers split the 10.6 degrees into 10 equal measurements. The disks labelled 0-5, 0 being 0 degrees and 5 being 5.3 degrees. To get from 5.3 to 10.6, you advance the sprocket 1 tooth and put the verniers in back to front.

The verniers can be changed without removing the sprocket from the camshaft. Very easy.

The exchange set is $85

How about I just drop my bike off, you fit and dial in my cams or whatever it is you do? .


And yeah Ive worked in the industry (errr ... what industry we talking about again?) and I know fuck all ...

[husaberg]

And yeah Ive worked in the industry (errr ... what industry we talking about again?) and I know fuck all ...

My best guess is our English correspondent is referring to the “industry” previously based at Manchester ST
But I could be wrong.
I thought at first he was refering to the adult film "industry" so I fessed up as well.
I did lurk there more than work there though.

[wobbly]

I was in the pit at Philip Island when Doohan tested the NSR with the water solenoids on the headers.
He did 3 laps, immediately full noise as he always did.
Came in and said it was a piece of shit till 1/2 way down the straight, but had heaps of power off the bottom and lost around 1000 rpm on top.
They plugged in the laptops, and I assume wound back the squirt volume.
Another 3 laps, and he said it now came on song much earlyer, but had lost most of the bottom end, and was still 800 rpm down on top speed..
More festering on the laptop, back out again.
This time no useable gain in bottom end,slow to come on the pipe, and still no overev power.
Mick just said - "maaaete,turn the fuckin things off and give it a go."
Went out and put it on pole,easily.
Talking to Burgess in the Cowes pub that night he said it seemed that to get enough water into the pipe to do some good for the bottom end, it took too long for the temp to rise back to "normal" again, so they had ripped the whole thing off, and binned the idea.
Adjusting the PV curve gave better, repeatable results.