Porsche Enthusiasts Club Forum

Where has all my power gone

Had my 944 S on a rolling road this morning (Alan Jeffry in Plymouth) and only managed 159.1 BHP. Apart from running a little rich everything else checked out OK (ignition circuit, cylinder compression etc) In fact it was commented on how smooth it was running but at a loss to explain where the extra horses have gone to given its only done 96000 miles.
Anyone any ideas ?

160ish bhp @ the wheels is fairly typical.

An old 944 lux would be lucky to push 115bhp @ the wheels (with maybe 140 corrected) compared to claimed 160bhp @ the crank


have a look here

http://www.cannell.co.uk/944%20UK%20League.htm

Assuming it actually had it's 190BHP originally then that's around 15% driveline losses which is quite good.

My lux made an estimated 163.2BHP at the flywheel earlier this year and was approaching 90kmiles at the time. The graphs are on 'ere somewhere if you look back.

I don't think it takes the fueling or electrics to be too far away from 'right' for the the output of these engines to be affected quite markedly.

Adam

I would think he is talking 159 at the flywheel -15% losses from wheels to flywheel is v.unlikely more like 25% I believe.

I'm sure a 15% loss could easily be realised with plugs, dizzy cap r.arm leads, AFM etc

16V heads soon start losing power even with small carbon build-ups.

Also depends on how accurate Porsche's claim is??

Rich

155 is typical for an S at the wheels. How fit is the engine? Has it had the injectors cleaned/replaced ever. Head overhaul? The hydraulic lifters get tired & don't start to rattle until really goosed. What do the cam lobes look like? Can you spin the balance shafts with your fingers (Belts off) I could go on. Most owners never bother to test the car on the rollers. So your already one up on most. I'm up to 140 with this kind of stuff so there was nothing wrong with the original Porsche power figures. It is adictive though & increasingly hard on the wallet. Going back to fix the fueling soon. Should be 145 ish when finished.

If it was 160 at the wheels I'd be more than happy, unfortunately its 160 at the flywheel. Car has just had new dizzy/rotor and ignition leads when it had a major service done.
Whilst i fully appreciate the cars age and the issues involved with rolling roads, I was suprised that the disparity was so large. However it will be back to the specialist towards the end of January to have the new belts checked and tightened and so will have a chat and see what (if anything) can account for it.

Can you scan the dyno printout and post it up? It might give some indications you never know?

Heres my Dyno printout, power curve looks fairly smooth. I was a slightly suprised at the relatively flat torque
curve but as I'm new to all this I dont really know if this is normal or not. I have a lot to learn

Looks like overall you're torque is a bit low across the range, but I think the general shape (width) of the curve is one you would typically expect of a 16V engine.

According to clarks site you should be making about 170ftlbs @ 4300rpm.

You said it was running rich so I would start with that first, should you decide to try and improve things.

Yup torque looks a little flat, for an S I'd expect more of a peak & also I'd expect it to be higher as well. A couple of points, check the throttle opens fully & also that the cam timing is correct. Either could produce this issue.