Choosing Gear ratios or gearboxes - Using dyno data?

So i've have made some thrust curves to compare different final drives. This isn't taking into account any losses or drag, just assuming no loss and extimating from the dyno torque curve. Assuming it is calculated right.

Tyre size = 195/50-15


What car has in now. DPA box. Spins up easily in 1st and 2nd, some slip in 3rd at peak torque.



Now with a 3.4 final drive from a VR (my assumed choice)



Now showing same box with lowest final drive available. Ie CTN. 3.125



All combined.



Hopefully some idea of how to use these will be available soon.

For good measure i've added the CTN Box which was first dicussed on here. But from looking at this box. It seems, as a box to put in with no changes it still would have a problem with 1st and probably second too as its very similar to the CDA. 3rd and 4th may be ok, but 5th too long. Although 5th is easy enough to change, it would need too much to make it a worthy change on this engine.

 

Some great info here guys, nice read whilst eating my breakfast....

Now could you possibly give me a breakdown of top speed/RPM with the following boxes please as I current have a MK3 16v box in my MK2 20vt but would like to see where i will gain speed and how uch wider spread the power would be delivered using each box-
MK3 16v
MK3 TDI
MK3 VR6

Thanks

 

Its shown on the graphs. Max RPM for this is shown as 6.5k

 

I opted for an ASD gearbox, it has the longer 1st and 2nd, good close and evenly spaced 3rd and 4th, the 5th is major long but if you can sacrifice 1st completely, fit a lower FD say 3.6 or 3.9 and think of it as a nice 4 speed box. I know a bit vague but I'm struggling to find my spreadsheet with ratios and graphs, might be of use.

 

ASD is similar to an ABF in ratios with a long 5th and taller final drive. You could improve it by putting an ABF 5th in, But it think you would be changing up and down the box a bit much to keep it in the torque band.

 

Variation on a theme?

 

I'm reading this, thinking about it, and wondering if it doesnt go a bit pear shaped when wheels start spinning...not ideal, but very likely under competitition scenarios in the lower gears, or under less than ideal grip scenarios

 

That's looks like some carefully chosen ratios.

 

Wheel slip will occur when the g's exceed a threshold based on the vehicle configuration i.e. FWD, AWD, RWD and gear.

For example in first and FWD generally, you are likely to slip when Gs exceed 0.7 I am told by a drivability engineer. This is why some light FWD applications, with a pokey engine and short overall gearing, first gear becomes useless.

 

Any way of confirming this with some G meter tests?

 

So Russ, did you use the DPA box with a VR6 final drive in the end?

I am looking at this combo for my 1.8T in my MK3.

 

Haven't done it yet but am planning to. Got the spare box and need to get diff before doing it.

 

After looking at these charts again, i've noticed on the combined chart there is an error with 3rd gears all having the same peak thrust. I'll check and correct later.

 

Combined curve chart corrected.

 

Russ are you going to fit an LSD?