Early 996 - Engine ECU "Learning" ?

[sundayjumper]

Does the ECU "learn" how you drive and alter its settings to suit ? I'm going for a rolling road session on Saturday and obviously want it to be on its best mapping for that, if there is such a thing. Worth disconnecting the battery overnight and then driving it hard on the way there ?

The rolling road session will be interesting, firstly to see how healthy my car is (1999 C2 with 97k miles), but also because my Dad & my brother will be there with their cars - a Merc E500 and a BMW 335i. On paper all three are within a sniff of 300bhp but will surely have very different characteristics:

3.4 litre na flat six
5.0 litre na V8
3.0 turbo straight six

I'm expecting the BMW to "win" on the RR but the Porsche would surely win in the real world around a circuit.... I would hope

[gibbon]

Please post your result, book horse power for each car and actual, would be interesting.

[sundayjumper]

Quoted figures are:

Porsche 996 Carrera 2 - 296bhp

BMW 335i Sport Touring - 302bhp

Mercedes W211 E500 Estate - 302bhp

(my bro gave me those numbers, don't shoot me if they're wrong)

I'll update at the weekend.

[Rockster]

sundayjumper said:

Does the ECU "learn" how you drive and alter its settings to suit ? I'm going for a rolling road session on Saturday and obviously want it to be on its best mapping for that, if there is such a thing. Worth disconnecting the battery overnight and then driving it hard on the way there ?

The rolling road session will be interesting, firstly to see how healthy my car is (1999 C2 with 97k miles), but also because my Dad & my brother will be there with their cars - a Merc E500 and a BMW 335i. On paper all three are within a sniff of 300bhp but will surely have very different characteristics:

3.4 litre na flat six
5.0 litre na V8
3.0 turbo straight six

I'm expecting the BMW to "win" on the RR but the Porsche would surely win in the real world around a circuit.... I would hope

It learns but it won't affect HP/torque numbers. It will respond to the torque demand and feed the engine a slightly richer air/fuel mixture that satisfies the torque being demanded by the driver, how much the pedal's pressed down.

Try to run in the cooler part of the day.

Avoid letting the engine idle too much and heat soak.

Be sure after the dyno run you let the engine idle to cool down. You can switch on the A/C which should turn on the radiator fans which helps remove heat from the engine.

Of course, be sure the A/C is off when doing the dyno thing. No fair reaching in and turning on the A/C in the other cars.

Oh, the shop should know this but a HP robbing gotcha is with independent rear suspensions if the car's pulled down to the dyno so much the halfshafts are no longer parallel with the ground, the angle robs power.

Sincerely,

Rockster.

[MadMark911]

If you want to cheat a little - pump the rear tyres up slightly higher than your normal pressures - the lower rolling resistance can skew the figures upwards unless it's a super flash dyno that can compensate in the calculations.

Also, get some Tesco 99 or Shell V Power (if you don't normally use it) - that can add a few more numbers to a healthy vehicle.

One question, though. Are either of the other cars automatics (I thought the Merc was auto as standard? If so I doubt you'll get properly comparitive figures .....

[sundayjumper]

Well, it's been an interesting day. It turned out my car was a little poorly The handbook quotes peak power as 221kW (300PS, 296bhp) at 6800rpm and this was my best run today:



However, the rolling road operator was confident that the problem was the MAF as he's seen the same thing many times before on 911s and Boxsters. The way the power drops away too soon and the disappointing and uneven torque at the lower end.

So I headed home and got online to find a new MAF. ECP in Reading had one in stock for £160. I rushed over and got there just 10 minutes before they closed ! Literally a couple of minutes to fit it and I headed home. Almost immediately the car felt better. Smoother and stronger at pootling speeds. One of the things I'd noticed right from the start when I bought the car was that it bogged down easily when pulling away. That's vastly improved now. That all fits in with the torque curve being raised & smoothed.

As to whether the missing 45bhp at the top has returned, I don't know. I don't often wring the car out all the way to the redline so I'm not all that familiar with how it behaves at 6000rpm+ and with the traffic and weather today I wasn't really able to test it with the new MAF but based on the improvements at normal engine speeds I'm confident there will be an improvement at the top too. I'll post another update once I've been back for another run on the rolling road.

£160 for an extra 45bhp is a great result

Edited by sundayjumper on Saturday 11th February 19:59

[sundayjumper]

And for comparison, here's the plots for the other two cars, both of which turned in very acceptable results:

2007 BMW 335i Sport Touring - 311.2bhp and appx. 310 ftlb

2003 Mercedes E500 Estate - 304.5 bhp and appx. 335 ftlb

[Magic919]

Looks like it was pretty cold. Hopefully you can get another run with the new MAF.

[Vixpy1]

Hello Steve, thanks for coming down today.

Glad the Maf makes a difference, your car defo felt a bit wolly pulling away.

Hopefully that cures your top end dieing off as well.

Charlie.