ESE's works engine tuner

[koba]

The 0.8mm clearance is for the "normal" big washer setup, so I cant say what would be the go with the open type - except to say that the whole idea of the 0.8 was to get more oil into the bearing and the open type wont have this issue at all.
The 0.2mm is side clearance, I just polish the journal such that the bearing inner race will "just" slide on by hand.
The floating crank allows the crank to move on the bearing as the case heats up and takes up all the side clearance in the main bearing.With it just floating the bearing will always centralise, thus reducing friction.
I would machine the case to get the 1mm clearance everywhere.

Huh, waddya know!
I had a performance mod on my streetstock just by starting with a worn out pile of poop...

[Chambers]

It might not be Buckets but there is a lot about Av.

http://speedweek.com.au/?p=2168

Av riding her stocker against the super tuned 125's

Bit of talking head stuff in the beginning bit, but then it gets interesting with Av blitzing them off the start.

[Rick 52]

Good coverage cheers Chambers.

[ac3_snow]

I have spent most of the afternoon playing around with the new port calculator/analyzer I downloaded recently, and have been rather confused as to the desired figures that I'm after

After finding the screen shots TZ350 posted of his figures for the Gp125 through ther same program (the origional post now eludes me) and thumbing through Grahams Bells book again I was able to make something I perceived as progress!

These are the figures I have at present, with the need to raise the ports by a further 1mm each. are these appropriate durations? (I will raise the barrel and take 1mm from the bottom)
I used the CAD application to estimate the shape I need for my exhaust port in order to get the required blowdown time area (I think?)

here is the port map of my barrel in its current unfinished form

It's a TF125 barrell, what I'm looking for is confirmation that I 'am going in the right direction, I'm not hundred percent sure that I utilized the program correctly either.
Any advise or constructive abuse would be much appreciated!

EDIT: I just realised the blowdown time area displayed on the calculator and the CAD application are different, I did have them equal at one point and assume this is the right thing to do?

[TZ350]

Ive been dabbling with this engine for sometime now, when TZ350 started his RGV project we got together and started working with Wobbly to acheive a reliable and fast package. Some things are different between our camps, cohice of bottom end being the main difference. Ive gone with a RG125 its similar to an rg150 but not quite the same.

Yow Ling sent me these photos of his progress, looks good and I hear there is another similar one being started in Christchurch too. So I had better get a move on with my own or I am going to be left behind.

And thats one serious looking carburettor.

Other interesting pic's

[wobbly]

With 200 and 135 and no powervalve it would be a peaky piece of shit.
You can run 72% no problem on the Ex width and drop the timing, but unless the program spits out STA im lost.

[speedpro]

I note the spark plug is at the original angle and therefore you probably have the original combustion chamber. I got instant horsepower with no other changes other than welding up the head and putting the plug in the middle of a standard shape chamber. It was more power everywhere measured on a dyno.

[ac3_snow]

With 200 and 135 and no powervalve it would be a peaky piece of shit.
You can run 72% no problem on the Ex width and drop the timing, but unless the program spits out STA im lost.

would an exhaust duration of 195 be more acceptable or could it still be peaky? I'm assuming transfer durations are semi appropriate.
not entirely sure as to STA, only figures it gives are..

[TZ350]

Handy porting calculator based on Jennings and Blairs work.

On the top right side you can toggle between Jennings or Blair. Blair gives you mean Blow Down Time Area.
Port durations are just a guide. its Port Time Area that is the true measure.



Chose the rpm using the vertical yellow line.

Horozontal yellow line is for working out the Ex and Trans durations for your rpm.

The numbers along the top left are used for working out the port heights needed to get the durations indicated.

The round dial thing is for selecting the Power/BMEP you want from the rpm you have chosen. 9-10-11 bar BMEP is typical and whatever you chose here effects how much Blow-Down-Time area is required.



Portcad starts with the data you entered, then you can adjust the ports in Portcad to get the Time Areas needed.

Top right, the yellow line that I drew shows you what Blair thinks you need for exhaust blow down time area based on the power and rpm you selected and bottom left what port cad calculates you have.

There is also numbers for transfer and exhaust time area.

Use port cad to adjust the ports, widths and heights to get the time areas you need, then go back and adjust the port heights to get the dimensions right.

Remember "Keep the Transfers Low and Wide" to increas blow down without increasing the exhaust port height (duration).

[TZ350]

I just realised the blowdown time area displayed on the calculator and the CAD application are different, I did have them equal at one point and assume this is the right thing to do?

Yes, you need to get them equall, the Calculator tells you what you need and PortCad tells you what you have.



Looks like you are doing pretty well with the program.

Here are a couple of the things that I see in this PortCalculator picture.

In the Calculator window Blowdown mean area required is 2.20 and you have in the Cad window 1.97 so you have to change the shape of the exhaust port to get more blowdown area or increase the blowdown time by raising the exhaust port or lowering transfers and widening them to keep their Port-Time-Area where its needed.

In the Calculator window Ex mean area required is 6.37 and you have in the Cad window 6.15, so once again you need to increase the size of the exhaust port.

In the Calculator window Transfer mean area required is 5.22 to 9.34 and you have in the Cad window 6.28, so your OK there.

In PortCad the shape and size of the ports can be changed by pulling the little yellow dots around.

To the right in the PortCad window there are options for changing the angles of the ports and changes to the port angles change the calculated port areas.

The headings "Int Mean Area" and "Intake Total Area" in the PortCalculator window are confusing names as they relate to the Transfers and not the Inlet Port.

[TZ350]

would an exhaust duration of 195 be more acceptable or could it still be peaky?

Remember, its all about getting the "Blow-Down-Time-Area" needed for the RPM and Power your looking for.

Everything else is adjusted to achieve that as well as having enought Port-Time-Area of their own to do their own jobs like exhausting, transfering and inletting.

[ac3_snow]

Yes, you need to get them equall, the Calculator tells you what you need and PortCad tells you what you have.

ok thanks alot, should have been able to figure that one out myself haha was slowly coming around

The transfer port designs in the CAD application are all standard, have'nt changed any of those yet so that will be my next step.
In terms of duration I 'am currently stuck with the minimum of 195 for my exhaust port (although a new barrell should arrive tomorrow with any luck, will be more careful with the next one)

as for power I would be happy with a measly 20-22hp at the wheel as long as its reasonably well spread. I will have to have another look at things now that I kind of almost know what I'm doing

EDIT: so wider ports = less duration.... which would make a broader power spread?I'm sure theres more to it that that but how do I avoid creating, in your wonderful words wobbly, "a peaky peice of shit"?

[TZ350]

as for power I would be happy with a measly 20-22hp at the wheel as long as its reasonably well spread. I will have to have another look at things now that I kind of almost know what I'm doing

You are doing very well, it took me ages, you have the right program for seeing if 20-22 is possible given whatever physical limitations the castings around the ports might impose on the porting you can do.

Once you know the RPM and BMEP you can use the spread sheet I have posted somewhere (try looking on the decade pages 140-130-120 etc) to work out the pipe dimensions you need. The spreedsheat is also based on Blairs work so should give you a good starting point.

[TZ350]

..... so wider ports = less duration....

Yes, you don't have to use the durations shown in the Port Calculator, they are based on the earlier work of Jennings and are the starting point but you do have to pay real attention to the mean Port-Time-Area's based on Blairs work.

And the final durations and port widths are the measurements for the ports so you can make them. PortCad also prints out a port template for you to use.

Wider is good, and especialy with the transfers, wider is very helpfull for fitting the required blowdown time area between the exhaust and transfers and for reducing the ex port duration (you can also reduce the Ex duration if you can increase the Port area) but about 70% of the bore dia is generaly regarded as the max reliable width for an unbridged ex port.

To get a realy low wide ex you need a bridge or multiple exhaust side windows.

There are lots of compromises to make, its all a juggling act (The Black Art).

Anyway thats how I understand it and if I have something wrong hopefully Wobbly will pick it up and set us straight.

[TZ350]

Just a couple of points - I would consider 0.6mm as the very minimum of big end clearance for a race engine.
I shoot for 0.8 with 0.2 in the case.
Do you float the crank on the side not locked by the drive gear/nut, some cranks are not locked and can float the 0.2mm by polishing both main jounals - it does make a difference.
The other thing I just learned from Overmars, Aprilia ( Jan Thiel) found that anything under 1mm clearance anywhere on the crank lost alot of power, due he said to increased fluid shear of the A/F mixture.

Yet Another Crank Rebuild



After a bit of machining, 0.8mm rod side clearance and 2mm clearance between the flywheels and the case every where else. A slip fit inside the outboard main brg and 50% ballance factor.