What happens on a Rolling road dyno tune!

This is a mini on my Sun Ram 300 Rolling road dyno, its a 1990 1275cc mini cooper with twin carbs and a lightly modified head. The vid shows a walkthrough with some tips as to the rolling road tuning process.
I set the timing on this car -with the distributor vacuum unit disconnected for setting- to 12 degrees at idle and 30 degrees at 4000 rpm, if its turbo or supercharged , you would prob want to aim for 25 degrees at 4000 rpm depending on boost as a higher pressure mixture burns quicker and therefore needs less advance /time to burn.
Hif 44 and 38 carbs turn mixture screw anti clockwise -as you look at the screw- to weaken the mixture.
The needle on both HIF and HS carbs is retained by a picnch screw in the piston, HS 'fixed needles' have a straight shank for the pinch screw , HIF carbs have 'floating needles' -there is a small collar for the pinch screw to hold on and a small spring on the top of the needle.
The rolling road holds the engine at a certain rpm and reads the maximum power at that point, measurements are usually taken at 1000 rpm or 5000 rpm increments.
Mixture with air fuel ratio wideband is 14:1 at cruise 12.5-12.7:1 at full load. For turbo / supercharged cars I would aim for 12-12.2 :1 afr
This mini, after calculating the transmission loss, showed 81bhp @5250 rpm and 88 ftlbs of torque @4000 rpm after tuning.
A pre-running in session is good to check you have the correct mixture and timing before running in so as not to cause damage to a new engine, just light loading is applied for this .
Most rolling roads take around 1-2 hours, or longer if say mapping is required to an injected mini with a mappable ecu.

Видео What happens on a Rolling road dyno tune! канала Vmaxscart