My bug - ANGRRR - the ongoing project

[acpaterson]

Yes, it is, and clearly is too powerful for these gearboxes.. Time you invested yet MORE money on a decent tranny Tony..

[Tony Z]

this is (supposed to be) one of the strongest custom built gearboxes in the country

[Jdt1976]

this is (supposed to be) one of the strongest custom built gearboxes in the country

And I think you took it as a challenge.

[acpaterson]

lol

[AlanH]

Ouch, maybe take it easy on pull away, when I suspect most torque is produced/used and only hammer it once the forces are less.

[Wentzel]

To me it is strange that 4th died like that. I would suspect that the lower gears would die easier with hard acceleration?? Is the forces more in 4th when opening the throttle??

[Tony Z]

As Wentzel said, it was 4th that broke, not the lower gears

I dont have answers for this one...

[retrovan]

The force of the motor is constant in all gears, but the car has the most resistance to move in 4th, so the load is the greatest in top, and normally the smallest gears as well. so if full acceleration is placed on all gears evenly, 4th will go 1st.

Herman

[Tony Z]

Makes sense...
Power = Force x velocity
Power stays constant, velocity goes down (gears turn slower in 4th than in 1st, relative to engine/input speed), therefore force must go up.

[Wentzel]

That makes sense... But I would think the lower gears take more abuse when making black lines etc on the road.

So will 4th stay in its place now?

[Tony Z]

yip, the lower gears will transfer more torque to the wheels and everything in line after the reduction gear. Think of a small motor turning something very large but turning it very slowly. The output side needs to handle the force, not the power. Power = Torque x velocity. Slow the final velocity down and the torque goes up, without changing power. Torque = Force x radius, too small a radius and the force breaks components

I hope 4th sill stay in place, only time will tell

[fourier]

Glad it's back together. I'm sure it ate a pile of money to get the damage repaired.

Would be interesting to know what was done to prevent a reoccurrence...

[Tony Z]

I think it is about time for an update.
unfortunately, not too much has happened that is worth reporting.

Lets see...
While the gearbox was out, I took the engine apart again. This time for two reasons
First (main reason) was because I needed to fit a stronger pressure plate as the stage 1 plate and dual friction clutch combo couldnt hold the torque. Fitting a new pressure plate will throw off the balance, so the only way to fit this properly is to hand in all the rotating parts (again) for balancing (again). I did this after having my flywheel skimmed (again) to make it smooth and flat (again).
The second reason was because I have had a small oil leak out of one of the head stud bolts for ages. This was from the crankcase, leaking out. So while the engine was open for balancing, I did what I could to hopefully fix this one once and for all.
Then I decided to advance my cam 4 degrees. Why? Why not???

When I put it all back together, the only new parts I used were the intake gaskets and the crank seal. To be honest, I'm not even sure if I changed the spark plugs or not.

Gearbox made its way back to CPT and I put it back in.
After fitting the gearbox, I decided to tackle my rear brakes which have always been the golf2 GTi rears (234mm diameter). They have always felt like they arent actually working all that well. So I did the same conversion that I did on the 1302, I made my own caliper brackets and fitted VW T5 VR6 Eurovan rear discs (280mm diamter). I also fitted new pads. This conversion was much easier the second time around, but its still nowhere near a bolt on arrangement.
While doing this I looked closely at how the rear setup is assembled and how the gearbox oil is held inside the tube and compared it to the axle seal kit that I was supplied.
After doing all sorts of measuring, I decided that the paper gaskets supplied in the kit shouldnt be used as they will move the bearing cover outwards a little and this will give the bearing some freedom to move in and out. So I fitted only the two O-rings and the shaft seal. Looking at it, these three seals together should be enough to stop any and all leaks. Only time will tell, but so far, so good.

Engine back in...

Test driving... the car seems pretty damn rapid with the advanced cam, but it was a while since I drove it last, and that car is pretty damn rapid anyway.
Unfortunately, the gearbox often grates quite badly going from 3rd into 2nd and sometimes I cant even get it down to second even after double clutching. So yea, a bit disappointed with that one.
I've thrown in synthetic oil to see if that will help.

Then I decided that t is time to sort out that elusive flat spot of mine which I've had since 2007 and always sits between 3000 and 4000 rpm. Over the years I've made massive improvements on this one, but it hasnt gone away completely.
I've now logged over 80 runs testing low speed jetting, medium power jetting, high speed jetting, transition and high power jetting... needless to say this didnt take a few hours to complete. I logged each and every change I made and how it works.
I've run all sorts of main, idle and air jet combos. Tried various float heights and changed emulsion tubes (F2, F11, F15, F16 and F3). Lets not forget that each emulsion tube change requires the jetting process to begin again from ground zero to find the jets that work best with that tube. Each float height adjustment also requires jetting to starts again at ground zero... So this has been a long tedious exercise.
After that, without any major improvements, I swapped out the 40mm venturis for 42mm ones and have started again. I do have to admit now that the bigger venturis have improved the flat spot, it is no longer a full 1000rpm long, now it seems to be only about 300rpm long. So thats a big improvement.
Unfortunately I have not yet narrowed down the best jetting combo for these venturis yet. I've only had time for about 5 runs. But now at least it seems that I am feeling the "quirks" of the emulsion tubes whereas before, changing them had no effect at all.
The only thing that I can think of that has been causing my issues, seems to be air speed vs rpm and the effects of a long duration cam and air intake reversion. This flat spot of mine goes massively rich and nothing that should work has worked. Putting in bigger venturis has slowed down the air speed which seems to have helped improve things... but only time will tell on this one.
That and I have a few new ideas to try out too.

[fourier]

Pity the gearbox is still giving you trouble. Are you sending it back to JHB? Certainly not a quick job removing and replacing, with all the extras fitted to your car.

[Tony Z]

thats a question that I dont yet have an answer for...