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Today was an interesting day, the weather was 24 degrees C ,not really weather for turbo charged cars !. I arrived at the dyno complex around 11.30 am , we started strapping the car on the rollers, this is a Dastek 4wd rolling road with limits of 1000 hp only.
As I mentioned before , the purpose of today was to make sure the AFR readings on the piggyback ecu were in line with the stock AFR tables .
On doing some 5 gear pulls on the dyno, traction was becoming an issues with the heat and the michelin super sports . The readings after 4 pulls varied from 580hp to 640hp . The dyno engineer said that the traction issue causes the dyno to read wrong and he would suggest looking at the lowest value . Unfortunately the graph is like the Himalayas but peak Hp was from 580 to 640hp.
The AFR readings started from 15 and down to 11.8 starting at 2500rpm to 7000rpm. When I installed the piggyback , the readings for the AFR were consistent with the stock reading , unfortunately with the setting set at 3 on the BMS ecu settings ,at 3300 went down to 9.5 and climbed at 5500 to 12.4.
This demonstrated why the car feels a little un responsive at those revs compared to stock as it's over fuelling and killing the power, then we changed the value of 3 down to 2.5 which is a stock setting on the BMS software ,The AFR readings were then comparable to stock at 12.5 -13.
So adjusting the setting in increments of .25 we got to 2.75 on the user interface , the AFR were comparable to stock , with around .4 difference to 7200rpm.
Even though peak hp seems better with setting set at 3 , it seems to rob power in the mid range , you can tell when you accelerate and hear the engine tone change to a lower frequency . Then you feel a huge serge in acceleration after 5500rpm because it is going leaner .
Top end hp is pointless when you loose the midrange torque and hp. The car is set to 2.75 on the BMS interface and it does feel very strong all the way through the rev range , it may loose a little hp top end but the overall drive is as good as stock .
After letting the tyres cool down , we managed to get 2 dyno runs with the piggyback set to 2.75 , it showed 650hp and 612lbs of torque with a discrepancy of around 15 on the second run. On the third run , the figure went to 730hp, but this was due to traction issues .
I achieved what I wanted to know about the AFR with the piggyback tune , but it shows that there is sacrifices if you want more hp up top . I am hoping to get on a hub dyno to get an accurate reading in the future. I am not really a dyno queen so numbers don't really matter, the sensation of the car is much stronger overall now and this is all the matters.
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