I got this car out running:
It is basically a B234 with Garrett turbo from a scania 8,8liter bus, 48,3mm long manifold, 4" exhaust, V-power 99 in the tank, stock cams, stock pistons with larger dish, 140mm intercooler, E39 M5 6speed gearbox, 3,54 diff with eaton truetrac running Toyo R1R 255/40-17.
Im running it in a fully equipped 245 turbo with power everything, i.e. in maximum weight condition. I do not know how heavy it is, but its not light.
Anyway, after DHB 2015, which was the first time the car ever ran outside the shop floor, i made the final run out of +15 like this:
60` 2,02sek
1/8 in 8,2sek @155km/t
1/4 in 12,32sek @ 196km/t
Im quite pleased with this result as it basically was a shakedown test, and i feel there is quite a bit potential left.
Some videofootage from Saturday(Mine is the 245): Sadly noone was there to film the faster runs:-(
https://www.youtube.com/watch?v=j_99Nq93knI
Now to the point:
Using the 6speed E39 M5 gearbox gives a very easy launching car, running consistently 2,0-2,1 sek 60`times, however, i need to run through 5 gears to complete the 1/4mile being halfway through 5th crossing the line.
Im thinking i could do this with 3shifts only.
Now, this is the speeds @ 7000rpm for each gear in current setup:
E39 6spd 3,54 7000
54,8
93,3
146,2
192,6
236,9
285,4
Starting in second gear will give a loong "1st gear" and i dont think i can do this without stalling or abusing the clutch too much.
If i change the diff to 3,91, and then start in second:
E39 6spd 3,91 7000
84,4
132,4
174,3
214,4
258,4
Which is much better, allthoguh still im not sure i can launch it without stall.
Now, if i pay around with gearboxes, then a M90 could look like this:
M90H2 3.31 7000
71,6
123,6
183,6
253,3
361,9
Not bad for 1st in think, but the steps between the gears in the higher end becomes larger.
Another option could be this gearbox:
GS6-53DZ 3,91 7000 skip 1st gear
76,6
120,5
170,2
214,4
255,3
I would then get a longish 1st, and run 4th gear out at 214km/t.
Im thinking this combo should be rather strong, but its the first time i play around with gearratios, diff ratios and a powerfull B234 turbo in a heavy 245 on streetable tires.
If we were free to choose gearbox for this car, what gearratio would we then aim for? I still do not have any power figures for the engine, exept i know the current combo could do 12,32@196 the first time out.
Any good suggestions?