Tom O'Kelly's Porsche 997 Carrera 2S 3.8 | Testimonial & Pictures | Stage 4

CONTENTS

Tom's Testimonial - Stage 4 Modifications  (list of modifications)

“The clutch and damper upgrades were to replace worn out standard 997 items, the clutch was worn and the dampers were pretty much shot at 38k miles. Having said that the car has been driven hard with upgraded brakes and roll bars for some time so they have had a work out and a half.”

Tom O'Kelly's Porsche 911 997 Stage 1 Modifications

“As I had the clutch out, this was the time to go for the single mass flywheel. The higher quality item weighs about 1/3 of the dual mass item so there is far less inertia in the engine as it revs.”

“Ian & I had worked for some time on various jigs for an induction system that could actually supply enough air to the beast at low speeds - Power kit engines are really hungry for air. Finally the preferred solution was designed, built and put in place (dual cone, massive input pipe).”

“The Bilstein B16's for any ones reference are near or at the top of the Bilstein tree, so much higher quality than the stock ones on the 997 but they also fully integrate with PASM so work exactly Porsche intended.”

“EuroCupGT remap - we had the chance to compare the power kit with a standard C2S engine, as Ian's latest project car went on aback to back remaps with mine - both with identical clutch, exhaust and induction systems - same rolling road, same day and same temp/environmental conditions.”

“When I picked the car up it felt like a factory new car - brand new suspension (yet to loosen off) tight clutch and engine - so hard to assess the effect of individual changes.”

Initial Views

“Driving back from Porscheshop I found the low speed ride harsh to say the least, a few people who have upgraded to B16's have said the same. But once at motorway speeds 50mph+ seemed t match he standard set up for comfort. Bad road surfaces at low speed could be a bit bone shaking.”

“However what became obvious was that the car was much flatter through any curve or corner and much more pointy via the steering , with much more linear/predictable responses”

“What dominated proceedings though was the transmission changes - the EuroCupGT remap brought the car back to feeling like a factory car, much smoother on road progression the drop off in torque from 2k - 2.8k revs seemed to have vanished and the car pulled evenly and flexibly all the way from 2k to the 7.5k cut off. It still went like a scalded cat over 3k revs but without the lag below it.”

“The single mass flywheel allowed the engine to rev up to that 3k+ band so easily and was much more responsive to throttle inputs, the car can now be driven very delicately on the throttle.”

“Any negatives - well the car stalls if you don't give it approx 1500rpm from stationary but before hand it would bog down if you ran under 1300rpm, so a slight adjustment then. There has been a slight loss in absolute torque and with the single mass flywheel its happier in gear up the rev band- so uphill now needs 2k revs in what every gear or it complains.”

Tom O'Kelly's Porsche 911 997 Stage 1 Modifications

“Using the revs more has slightly reduced fuel economy - mostly noticeable on long motorway runs with cruise control where on a good day I'd get 30/31mpg now its about 27mpg. Worst end of consumption is about the same. this could also be due to em driving the car a bit arider as well........”

So Power kit engine - was it worth it?

“In short yes - comparing graphs from the C2S engine vs the power kit its not immediately obvious. Peak power on the road is only about 10PS more BUT - this is over a very narrow rev range. Both cars were tuned for drive ability over peak power outputs so you have to look at over the rev range and then the difference becomes very clear - Average power is approx 30-35hp higher at every rev and in every gear apart from 200-300 revs either side of peak power. Torque is a similar story with 30+ lbft extra all the way through the range at some points significantly more.”

“So in answer the power kit engine pulls harder and works harder all the way across the rev range.”

“Having driven both cars on a familiar road the traces bear out in how the cars feel on the road.”

Consequences of the remap

“To match previous numbers I have given - I went back to the figures at the tyre for EuroCupGT and applied the algorithm used to get like for like, as each rolling road gives different results these are approximate.”

“Peak torque is down from approx 370lbft to 350lbft at the crank but this comes in from about 2.8k revs and stays there for a fair chunk of the rev band - so its less peaky and broader. The real comparison is that it runs over (approx) 310lbft at the tarmac, which is the Power kit's quoted crank toque. So the upgrades have made a real difference here.”

“As stated the 2k -2.8k drop off is gone. There is less torque below 2k revs but now it builds smoothly through from 1.5k to 2k and through to 2.8k and then 3k getting stronger all the time but in a very linear fashion - no judders, jerks or drop offs.”

Tom O'Kelly's Porsche 911 997 Stage 4 Modifications

“Power is in the region of 395PS/ 402hp so basically the same as the Gen 2 Power kit. Clearly this number would be slightly higher on the road with greater air flow (the rolling road was in a closed room).”

“Bearing in mind the car was tuned for drive ability (in gear performance) through the rev range as opposed to a high top end power this is not an embarrassing figure. The key thing now is the car pulls hard to the red line whereas before it was all done by 6-6.5k revs)”

“Gains in power from EuroCupGT were very small but the spread of torque, elimination of flat spots, ability to use the wider rev range and single mass flywheel's ability to get you into the power band have now made this one fast car.”

Thoughts after driving it for 3k miles

“Firstly the changes have bedded in and the suspension has settled noticeably and the power train has loosened up again.”

“The engine now revs incredibly freely the noise from the exhaust and induction at full bore is intoxicating and difficult to miss if your in the same county.”

“The real surprise is the B16's, they are settling in the ride has become significantly more compliant - high speed ride (50mph+) is significantly better than the original dampers, low speed ride on a good road surface is firmly damped but very comfortable. It still doesn't like poorly surfaced roads at low speed and was noticeably firmer in the sub zero weather we had recently. The car is flat through corners and to quote Alex who has B16's on his turbo "you don't notice the corners any more so much as you have to look out for the big potholes". I would say that is a very fair assessment.”

“The combination of GT3 roll bars, Drop links and B16's has made this a very agile car - its very responsive to steering inputs at all speed and gives much clear feedback on where limits of grip are.”

Tom O'Kelly's Porsche 911 997 Stage 4 Modifications

“The dampers are settling in though which means I suspect they give a little bit more compliance before they each their normal operating level. At this point I think its a trip back to center gravity to take advantage of this capability.”

“The car I now very pokey and on a few recent run outs its had a surprising turn of speed under full throttle - even considering the heavier than average driver a passenger (with very heavy handbag ) and a car full of stuff.”

“Talking to EuroCupGT we've pretty much optimised the engine now - turning up the wick much more and keeping drive ability would shorten the working life of components - so thats a no. The suspension is fine any additional work would put it the wrong side of comfortable for regular long distance drives.”

“Niggles - Generally there is a lot of refinement form the engine & transmit ion at partial throttle on motorway runs and at 50+ its now very comfortable. As I use the car regularly to travel 200 miles for work this is a must for me - the compromise is the low speed ride over rough surfaces is probably on a par with a 997 GT3 firm and damped but still firm. Of the three choices though high speed control and motorway comfort, I'd live with the low speed ride. This might in part be due to the dampers still settling in and the cambers on the tryes moving around. I'll give it another 5k before full comment.”


Stage 4 Modifications made to Tom's car  (testimonial)


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