sandy309
16-04-2008, 07:22 AM
I finally got to do something recently that I've wanted to do for a long time, a back to back with and without a good TB set up on a 106 GTi.
Nicks car started out with a standard engine, fitted with a Supersprint exhaust manifold and green filter cold air induction kit. This is a popular set up which clearly extracts very good results without further mods. The car has been rolling road tested at Powerstation before, and was indicated to give 152bhp at the flywheel, a bit optimistic, but clearly working well.
When Nick arrived with the car, we immediately warmed it up and put it in the rollers to take a set of "before" figures so we could see after exactly where the figures were changing. The conditions were fairly cool, so ideal for good readings! We test power at static rpm sites using a Sun RAM XII rolling road with DRO, it's calibrated regularly with a torque arm to ensure consistent and repeatable figures.
The figures we got were pretty good, the best "standard" 106 GTi we've seen yet, it had a very strong torque peak (approximately 125lbft flywheel at 5500rpm) and peak power was 118bhp at the wheels (approximately 142bhp flywheel at 6500rpm). I clearly had my work cutout to beat that!
I'd already prepared the loom work to convert to the DTA S40 ECU, so removing the standard inlet and fitting the new inlet (my DCOE "DTH" style design) and the 42mm Jenvey TH bodies was a pretty straight forward task after cutting the scuttle. Once the car was back up and running I did some road miles to hone down the fueling map; I prefer to trim the fuel mapping out in the real world, because the engine is seeing the airflow and temps it will really see, rather than the slightly artificial environment of the rollers. After that it was down to the rollers to optimise the ignition map for best power and check the results.
I fitted 40mm trumpets initially, to allow room for a proper filter to be fitted, it's the practical maximum. The initial mid range results weren't really climbing clear of the standard inlet to though and it wasn't pulling clear of the standard results until 5200rpm, after that it peaked at 128bhp at the wheels (bear in mind that after mapping the conditions were much hotter than the initial standard engine test), which was 10bhp up on the original set up.
I wasn't convinced at this stage that it was all working as it should and set about finding some other trumpets to try, to see if the mid range could be improved. Stuart Hatch down the road had some 60mm trumpets that would fit and kindly dropped them over on his lunch break (cheers Stuart!!). We starting mapping the changes and the difference in mid range was incredible, at 4000rpm it was 15bhp up (18%) up on the 40mm trumpets and kept on making more power all the way to the limiter! The final results being 131bhp at the wheels (approx 158bhp flywheel) and approx 133lbft at 6000rpm, holding over 85% peak torque from 3500-7000rpm.
Here are my plots of the results:
Wheels figures:
http://www.goodhand.co.uk/sandy/files/NickCharlesWheelsBHP.JPG
Flywheel final figures:
http://www.goodhand.co.uk/sandy/files/NickCharlesFlyEstimated.JPG
The small difference in trumpet shape and/or tract length made an huge difference to the end results and to me insists the importance of tuning TB set ups to the engine, rather than just bolting on what you have and judging it as a success or failure.
None of this really illustrates how the car feels or sounds on the move either, which is pretty pleasing too!
Nicks car started out with a standard engine, fitted with a Supersprint exhaust manifold and green filter cold air induction kit. This is a popular set up which clearly extracts very good results without further mods. The car has been rolling road tested at Powerstation before, and was indicated to give 152bhp at the flywheel, a bit optimistic, but clearly working well.
When Nick arrived with the car, we immediately warmed it up and put it in the rollers to take a set of "before" figures so we could see after exactly where the figures were changing. The conditions were fairly cool, so ideal for good readings! We test power at static rpm sites using a Sun RAM XII rolling road with DRO, it's calibrated regularly with a torque arm to ensure consistent and repeatable figures.
The figures we got were pretty good, the best "standard" 106 GTi we've seen yet, it had a very strong torque peak (approximately 125lbft flywheel at 5500rpm) and peak power was 118bhp at the wheels (approximately 142bhp flywheel at 6500rpm). I clearly had my work cutout to beat that!
I'd already prepared the loom work to convert to the DTA S40 ECU, so removing the standard inlet and fitting the new inlet (my DCOE "DTH" style design) and the 42mm Jenvey TH bodies was a pretty straight forward task after cutting the scuttle. Once the car was back up and running I did some road miles to hone down the fueling map; I prefer to trim the fuel mapping out in the real world, because the engine is seeing the airflow and temps it will really see, rather than the slightly artificial environment of the rollers. After that it was down to the rollers to optimise the ignition map for best power and check the results.
I fitted 40mm trumpets initially, to allow room for a proper filter to be fitted, it's the practical maximum. The initial mid range results weren't really climbing clear of the standard inlet to though and it wasn't pulling clear of the standard results until 5200rpm, after that it peaked at 128bhp at the wheels (bear in mind that after mapping the conditions were much hotter than the initial standard engine test), which was 10bhp up on the original set up.
I wasn't convinced at this stage that it was all working as it should and set about finding some other trumpets to try, to see if the mid range could be improved. Stuart Hatch down the road had some 60mm trumpets that would fit and kindly dropped them over on his lunch break (cheers Stuart!!). We starting mapping the changes and the difference in mid range was incredible, at 4000rpm it was 15bhp up (18%) up on the 40mm trumpets and kept on making more power all the way to the limiter! The final results being 131bhp at the wheels (approx 158bhp flywheel) and approx 133lbft at 6000rpm, holding over 85% peak torque from 3500-7000rpm.
Here are my plots of the results:
Wheels figures:
http://www.goodhand.co.uk/sandy/files/NickCharlesWheelsBHP.JPG
Flywheel final figures:
http://www.goodhand.co.uk/sandy/files/NickCharlesFlyEstimated.JPG
The small difference in trumpet shape and/or tract length made an huge difference to the end results and to me insists the importance of tuning TB set ups to the engine, rather than just bolting on what you have and judging it as a success or failure.
None of this really illustrates how the car feels or sounds on the move either, which is pretty pleasing too!