Knackered old Porsche with loads of miles - 996 content
Discussion
Reposted from 911UK:
Preliminary Results
So with around 1200 miles on it now I thought it was time to see where we were in terms of power compared against the previous engine. Now the below is fairly accurate, even when compared to what a direct measure would be, but it's very reliant on the figures you are plumbing into it. It's really a system we use to monitor how the engine health is doing over life in a racing car but it does provide repeatable results and obviously having some 200K miles of data to compare it against is the important thing for measuring a gain. The below is based on linear acceleration over time to determine the wheel power developed to move the specific amount of mass with the specific amount of aero drag at the measure rate of acceleration.
It's fairly simple stuff, firstly we calculate the power absorbed moving the car through the air at the current speed which we can do by knowing the frontal area of the car and the drag coefficent along with the speed in metres/second. Once we have this value we can then calculate the wheel power of the car (it's important we know aero drag or the resulting figure would be vastly different for a given RPM in first gear vs 6th gear due to the greater vehicle speed), to do this we need to know the mass all up (so with fuel, driver, additional kit etc.) which I have from time spent on the corner weight scales along with the linear acceleration of the car - linear acceleration being essentially the rate of change in velocity. For the sake of accuracy we are using a 10hz GPS to determine the start and end velocities and validating this with a longitudinal G measurement i.e. to accelerate from X to Y speed in a certain time has to have yielded an average accelerative G of Z so if our measured G is vastly different at one point or our measured average G between the points doesn't match our calculated average then we disregard this measurement as flawed. To get to flywheel power from wheel power we use a simple formula based on a known measure of wheel power against a known OEM SAE corrected engine dyno result, in this case what my car made as a standard 100 and a bit thousand mile car vs Porsches 300PS no aircon, no PAS, engine dyno rating. It's a sliding scale based on torque produced but at peak power the total loss between flywheel and tyre contact patch is about 14.8% by my math.
It might all sound a bit math heavy but with a decent logger you can do this live on the box and it's pretty much the same system we used in pro motorsport in the days before we had reliable and long lived drive shaft torque sensors.
So here is where we have ended up from testing today. This is an average across 12 runs with 6 in each direction to account for the slope of the runway:
According to this it's making 363.2bhp at 6250RPM and a peak torque of 318.8ftlbs at 4750RPM. What's nice is that it makes over 300ftlbs from 3500RPM to 6200 and a bit RPM. It is quite clearly all done by 6.5K and torque drops away rapidly here to the rev limiter at 7200rpm.
Lambda is fairly good considering the ECU calibration is pretty much standard. There is something odd going on at mid RPM in low gears where the ECU is winding the throttle down during 100% PPS which is likely to be the result of a torque limiter somewhere being exceeded (not surprising all things considered!) and performance could clearly be found by going richer below 4500RPM, at the moment the ECU is staying in closed loop mode until this point to keep the cats happy (which is fairly pointless as mine hasn't had cats since 2013).
Gains wise when compared against the old engine (and that is compared using the same math as determined this engines performance so it is a good comparison!) this engine is about 30ftlbs and 25bhp up on it when the old motor was at its best with considerably more torque at lower RPM - indeed the additional low RPM torque is far more than I would have thought would be gained by going up a relatively small amount in capacity, it's likely there are some improvements in cylinder filling at lower port velocities/engine speeds as a result of the larger bore/swept capacity.
For those interested the full spec of this engine is:
- Autofarm 3.7L castings.
- Autofarm cylinder heads
- CP Pistons in standard C/R with reduced size skirts for friction reduction.
- Standard size inlet and exhaust valves.
- Standard Cam Shafts
- Variocam fitted and working.
- Cams timed to Autofarms spec for 3.7L
- FVD Equal length exhaust manifolds
- Cat delete crossover pipes.
- No name perforated tube stainless silencer boxes (I think these are the same as D911, Porscheshop etc. sell).
- 996 GT3 Throttle Body
- Slightly hooky IPD plenum to suit the above
- 997 Airbox
- Large diameter silicone hose to suit the above joint to the GT3 throttle.
- No Secondary Air System
- No Air Con Compressor.
- ECU Calibration is essentially standard but with lower fan on temps etc.
- FVD Large Capacity Sump (not that this really has any effect on power)
- Low Temperature thermostat (as above)
- Metal impeller water pump (12 months life) (as above)
- Roller bearing IMS (as above)
It will go on a dyno at some point in the near future as it's very clear there is more to be had from some engine calibration development (not least solving the torque limiter problem that rears it's head when launching the car hard) and the instant 30 second feedback a chassis dyno provides when doing this does rather minimise the time required. It's also pretty clear the cams that are in it are probably too soft for an out and out performance engine as the additional low RPM torque could be traded off for high RPM power, however as my car is 99% a road car and the lower the revs the longer the engine life I'm quite happy setting the last shift light at 6.5K RPM Very Happy
For those interested in how I'm logging this data the car has an AIM EVO5 logger onboard with two LCU-One wideband controllers, a GPS08 GPS/Glonass receiver and a GS-Dash (with motorsport cable tie mounting!). It takes basic data from the car via OBD2, RPM from the tach signal at the OBD2 connector and oil pressure on a dedicated sensor.
To sum up - I'm rather pleased with how the old girl goes now and it would be interesting to see where we are vs a 996 Mk1 GT3 Very Happy
Preliminary Results
So with around 1200 miles on it now I thought it was time to see where we were in terms of power compared against the previous engine. Now the below is fairly accurate, even when compared to what a direct measure would be, but it's very reliant on the figures you are plumbing into it. It's really a system we use to monitor how the engine health is doing over life in a racing car but it does provide repeatable results and obviously having some 200K miles of data to compare it against is the important thing for measuring a gain. The below is based on linear acceleration over time to determine the wheel power developed to move the specific amount of mass with the specific amount of aero drag at the measure rate of acceleration.
It's fairly simple stuff, firstly we calculate the power absorbed moving the car through the air at the current speed which we can do by knowing the frontal area of the car and the drag coefficent along with the speed in metres/second. Once we have this value we can then calculate the wheel power of the car (it's important we know aero drag or the resulting figure would be vastly different for a given RPM in first gear vs 6th gear due to the greater vehicle speed), to do this we need to know the mass all up (so with fuel, driver, additional kit etc.) which I have from time spent on the corner weight scales along with the linear acceleration of the car - linear acceleration being essentially the rate of change in velocity. For the sake of accuracy we are using a 10hz GPS to determine the start and end velocities and validating this with a longitudinal G measurement i.e. to accelerate from X to Y speed in a certain time has to have yielded an average accelerative G of Z so if our measured G is vastly different at one point or our measured average G between the points doesn't match our calculated average then we disregard this measurement as flawed. To get to flywheel power from wheel power we use a simple formula based on a known measure of wheel power against a known OEM SAE corrected engine dyno result, in this case what my car made as a standard 100 and a bit thousand mile car vs Porsches 300PS no aircon, no PAS, engine dyno rating. It's a sliding scale based on torque produced but at peak power the total loss between flywheel and tyre contact patch is about 14.8% by my math.
It might all sound a bit math heavy but with a decent logger you can do this live on the box and it's pretty much the same system we used in pro motorsport in the days before we had reliable and long lived drive shaft torque sensors.
So here is where we have ended up from testing today. This is an average across 12 runs with 6 in each direction to account for the slope of the runway:
According to this it's making 363.2bhp at 6250RPM and a peak torque of 318.8ftlbs at 4750RPM. What's nice is that it makes over 300ftlbs from 3500RPM to 6200 and a bit RPM. It is quite clearly all done by 6.5K and torque drops away rapidly here to the rev limiter at 7200rpm.
Lambda is fairly good considering the ECU calibration is pretty much standard. There is something odd going on at mid RPM in low gears where the ECU is winding the throttle down during 100% PPS which is likely to be the result of a torque limiter somewhere being exceeded (not surprising all things considered!) and performance could clearly be found by going richer below 4500RPM, at the moment the ECU is staying in closed loop mode until this point to keep the cats happy (which is fairly pointless as mine hasn't had cats since 2013).
Gains wise when compared against the old engine (and that is compared using the same math as determined this engines performance so it is a good comparison!) this engine is about 30ftlbs and 25bhp up on it when the old motor was at its best with considerably more torque at lower RPM - indeed the additional low RPM torque is far more than I would have thought would be gained by going up a relatively small amount in capacity, it's likely there are some improvements in cylinder filling at lower port velocities/engine speeds as a result of the larger bore/swept capacity.
For those interested the full spec of this engine is:
- Autofarm 3.7L castings.
- Autofarm cylinder heads
- CP Pistons in standard C/R with reduced size skirts for friction reduction.
- Standard size inlet and exhaust valves.
- Standard Cam Shafts
- Variocam fitted and working.
- Cams timed to Autofarms spec for 3.7L
- FVD Equal length exhaust manifolds
- Cat delete crossover pipes.
- No name perforated tube stainless silencer boxes (I think these are the same as D911, Porscheshop etc. sell).
- 996 GT3 Throttle Body
- Slightly hooky IPD plenum to suit the above
- 997 Airbox
- Large diameter silicone hose to suit the above joint to the GT3 throttle.
- No Secondary Air System
- No Air Con Compressor.
- ECU Calibration is essentially standard but with lower fan on temps etc.
- FVD Large Capacity Sump (not that this really has any effect on power)
- Low Temperature thermostat (as above)
- Metal impeller water pump (12 months life) (as above)
- Roller bearing IMS (as above)
It will go on a dyno at some point in the near future as it's very clear there is more to be had from some engine calibration development (not least solving the torque limiter problem that rears it's head when launching the car hard) and the instant 30 second feedback a chassis dyno provides when doing this does rather minimise the time required. It's also pretty clear the cams that are in it are probably too soft for an out and out performance engine as the additional low RPM torque could be traded off for high RPM power, however as my car is 99% a road car and the lower the revs the longer the engine life I'm quite happy setting the last shift light at 6.5K RPM Very Happy
For those interested in how I'm logging this data the car has an AIM EVO5 logger onboard with two LCU-One wideband controllers, a GPS08 GPS/Glonass receiver and a GS-Dash (with motorsport cable tie mounting!). It takes basic data from the car via OBD2, RPM from the tach signal at the OBD2 connector and oil pressure on a dedicated sensor.
To sum up - I'm rather pleased with how the old girl goes now and it would be interesting to see where we are vs a 996 Mk1 GT3 Very Happy
As a early 996 owner, this thread is heartwarming.
My 2000 C2 is now on 163k miles, and shows no sign of any engine issues (touch wood). Bores were checked in 2015, and showed no signs of wear, and it uses no oil between services... I'd be very happy to get another 100k+ miles before it requires attention.
A recent full exhaust (manifolds/cats/backboxes) has transformed the performance - not exactly a cheap job (22 hours labour!), but it was running a bit rough in the low/mid range and now is absolutely flying again... feels like someone's given it another 50bhp.
Maybe 996's will appreciate enough for me to justify a 3.7 upgrade in the years to come.
My 2000 C2 is now on 163k miles, and shows no sign of any engine issues (touch wood). Bores were checked in 2015, and showed no signs of wear, and it uses no oil between services... I'd be very happy to get another 100k+ miles before it requires attention.
A recent full exhaust (manifolds/cats/backboxes) has transformed the performance - not exactly a cheap job (22 hours labour!), but it was running a bit rough in the low/mid range and now is absolutely flying again... feels like someone's given it another 50bhp.
Maybe 996's will appreciate enough for me to justify a 3.7 upgrade in the years to come.
Paddy_N_Murphy said:
911's are the answer.
I've just had to drive from Teesside to Great Yarmouth after a family funeral. I was going to take the company pool car / Merc, but brought my 'old' (2007) 997.
3h10m.
Exactly the journey a 911 is made for IMHO - 250miles of getting it on.
I was hoping to make last orders in the hotel.
I got dinner instead
It's not just how nicely they convey you, or how effective they are at covering the distance, but also the relish with which they take to it.I've just had to drive from Teesside to Great Yarmouth after a family funeral. I was going to take the company pool car / Merc, but brought my 'old' (2007) 997.
3h10m.
Exactly the journey a 911 is made for IMHO - 250miles of getting it on.
I was hoping to make last orders in the hotel.
I got dinner instead
My 996tt doesn't use oil as much as the owner's manual suggests is 'normal', but, the miles it used the very least in were the hardest worked; a trip last year through excellent, twisty (and no fences, hedges, ditches or traffic) French country roads, autobahns and a day lapping the Nordschleife.
olly22n said:
Chris Stott said:
As a early 996 owner, this thread is heartwarming.
My 2000 C2 is now on 163k miles, and shows no sign of any engine issues (touch wood). Bores were checked in 2015, and showed no signs of wear, and it uses no oil between services... I'd be very happy to get another 100k+ miles before it requires attention.
A recent full exhaust (manifolds/cats/backboxes) has transformed the performance - not exactly a cheap job (22 hours labour!), but it was running a bit rough in the low/mid range and now is absolutely flying again... feels like someone's given it another 50bhp.
Maybe 996's will appreciate enough for me to justify a 3.7 upgrade in the years to come.
I'd say the fact they aren't depreciating is enough! Go for it!My 2000 C2 is now on 163k miles, and shows no sign of any engine issues (touch wood). Bores were checked in 2015, and showed no signs of wear, and it uses no oil between services... I'd be very happy to get another 100k+ miles before it requires attention.
A recent full exhaust (manifolds/cats/backboxes) has transformed the performance - not exactly a cheap job (22 hours labour!), but it was running a bit rough in the low/mid range and now is absolutely flying again... feels like someone's given it another 50bhp.
Maybe 996's will appreciate enough for me to justify a 3.7 upgrade in the years to come.
And I'd like to upgrade the suspension before moving to the engine. Although it would be nice, it doesn't really NEED more power... a stock 996 has a lovely balance of performance... quick enough to make very good progress, but not that quick you can't use the performance without risking life and license. A set of coilovers will likely be my next upgrade (arms/bushes/top mounts renewed last year).
Chris Stott said:
olly22n said:
Chris Stott said:
As a early 996 owner, this thread is heartwarming.
My 2000 C2 is now on 163k miles, and shows no sign of any engine issues (touch wood). Bores were checked in 2015, and showed no signs of wear, and it uses no oil between services... I'd be very happy to get another 100k+ miles before it requires attention.
A recent full exhaust (manifolds/cats/backboxes) has transformed the performance - not exactly a cheap job (22 hours labour!), but it was running a bit rough in the low/mid range and now is absolutely flying again... feels like someone's given it another 50bhp.
Maybe 996's will appreciate enough for me to justify a 3.7 upgrade in the years to come.
I'd say the fact they aren't depreciating is enough! Go for it!My 2000 C2 is now on 163k miles, and shows no sign of any engine issues (touch wood). Bores were checked in 2015, and showed no signs of wear, and it uses no oil between services... I'd be very happy to get another 100k+ miles before it requires attention.
A recent full exhaust (manifolds/cats/backboxes) has transformed the performance - not exactly a cheap job (22 hours labour!), but it was running a bit rough in the low/mid range and now is absolutely flying again... feels like someone's given it another 50bhp.
Maybe 996's will appreciate enough for me to justify a 3.7 upgrade in the years to come.
And I'd like to upgrade the suspension before moving to the engine. Although it would be nice, it doesn't really NEED more power... a stock 996 has a lovely balance of performance... quick enough to make very good progress, but not that quick you can't use the performance without risking life and license. A set of coilovers will likely be my next upgrade (arms/bushes/top mounts renewed last year).
the_engineer said:
Where did you get your suspension work done if you don't mind me asking? Mine is overdue and I'm looking for a decent specialist (preferably near/around West London). Cheers,
GT One in Chertsey (off J11 M25) do all my servicing/repairs.Probably not the cheapest, but they do very high quality work and handle some very high value cars (I've seen multiple 964/993 RS's in there, and even a RUF RGT last time I was in).
Really nice bunch of blokes as well
HDM said:
Poppopbangbang,
I don't know if you have seen this, but in the most recent issue of "Car" magazine, there is a feature on Autofarm, and the rebuild of your engine is mentioned, small world!
Do they build good track rod ends? I don't know if you have seen this, but in the most recent issue of "Car" magazine, there is a feature on Autofarm, and the rebuild of your engine is mentioned, small world!
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Gassing Station | Readers' Cars | Top of Page | What's New | My Stuff