968 Turbo boost problems whilst mapping

[Thom]

See here.
Around 400 hp and 700 N.m at 4000 rpm.

[Rickuk1]

See here.
Around 400 hp and 700 N.m at 4000 rpm.

Wow great figures

[Thom]

Thanks.
In what gear was your dyno run done? I assume you still run the original 968 gearbox and ratios?

[Rickuk1]

I think it was in fourth gear for the run. The gearbox is 968 standard box other than limited slip differential.

[Thom]

I can't remember exactly but I suppose the 4th gear ratio in the 968 gearbox may be about as tall as the 3rd one in the 944 turbo gearbox, meaning you may want to try doing dyno runs in at least 5th gear as the extra load should help spooling the turbo earlier.

[333pg333]

...

[Thom]

Looks like a comparison of the 944t ratios with the regular 944's?

Here is the diagram for the 968 'box :

_20250325_083611.JPG (122.6 KiB) Viewed 4354 times

[333pg333]

Hmm, you're right. Not sure what happened there. I've removed it. You're also correct Thom re the 951 4th gear vs the 968 5th gear. Very close in road speed. https://members.rennlist.com/951_racerx/gearing.html

[Thom]

Well, I am wrong re 951 3rd vs 968 4th, as the gap between these two is much larger than for 951 4th vs 968 5th.
It still seems correct to me though to perform a dyno run in 5th with a 968 'box with stock ratios, at least with such an engine set up.

[333pg333]

According to the chart in that link. 951 in 4th gear is doing 21.2mph per 1000rpm and the 968 is doing 21.50mph in 5th gear under same conditions with same size tyre. So yes, testing in 5th with a conventional 968 transmission is most suited.