The Porsche 924 Owners Club
http://porsche924.co.uk/forum/

So this turned up today
http://porsche924.co.uk/forum/viewtopic.php?f=7&t=29819
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Author:  Carrera RSR [ Sat Nov 11, 2017 6:26 pm ]
Post subject:  Re: So this turned up today

Looks like a #4 turbine housing v's #6 but I could be wrong. There are castings on both hot and cold side. Not conclusive what compressor wheel, but if it is an S2 #4 turbine then its quite possible the compressor is an S2 2660 wheel which is far better than an S1 2470 .

Issue is so many are not original, been replaced, rebuilt, swapped by OP, garages and turbo specialists its hard to be 100% certain unless you built it yourself.

See here - https://porsche924.co.uk/forum/viewtopi ... 47&t=13684

Given the results on the dyno, I wouldn't worry too much

Author:  Wes [ Sat Nov 11, 2017 8:01 pm ]
Post subject:  Re: So this turned up today

Carrera RSR wrote:
Looks like a #4 turbine housing v's #6 but I could be wrong.


As suspected - if so it explains the phat torque at 3000rpm with 1bar and the less-than-expected peak rpm power. Running a 'smaller' turbo at higher boost (within reason) gives phat torque. Ideal for the road.

Author:  DrJohn [ Sat Nov 11, 2017 8:08 pm ]
Post subject:  Re: So this turned up today

All good (and interesting points) but I still find it odd, or should I say a huge coincidence, that every dyno curve for a 924 I've ever seen falls off at 5.2krpm - whether it's turbo or not. Surely there must be a common component responsible for that? Has anyone seen the plots for a variety of cam shafts - I've always had my money on it being the cam profile as the cause/explanation?

I'm not saying that it's a bad thing as such, but it certainly limits the BHP figure for bragging rights!

I would love to try a more aggressive cam on mine and see how the drivability/ engine character changes, but can't justify £300 without some confidence I will like it!!

Author:  Carrera RSR [ Sat Nov 11, 2017 9:02 pm ]
Post subject:  Re: So this turned up today

Mittelmotor sent me a comparison table of cams. Unfortunately they did not send me the list of cams used in the comparison test!! Double unfortunately they did not test the Kent cam that is in my car nor suggest where it sits in the table so I could see if it’s good or not. I guess if my car was sat in their workshop and my credit card is poised for use I’d get more feedback. As it is Michael has been very open on most questions I posed to him. But some specifics were kept up his sleeve.

Author:  DrJohn [ Sat Nov 11, 2017 9:09 pm ]
Post subject:  Re: So this turned up today

You can't blame them for that! Although it was definitely worth asking!!

What does your torque do after 5k?

:beer:

Author:  Carrera RSR [ Sat Nov 11, 2017 9:23 pm ]
Post subject:  Re: So this turned up today

DrJohn wrote:
You can't blame them for that! Although it was definitely worth asking!!

What does your torque do after 5k?

:beer:


Posted the May dyno day sheets a few pages ago. Both mine and Richard K turbos torques drop off post 5k.

Author:  Wes [ Sat Nov 11, 2017 9:52 pm ]
Post subject:  Re: So this turned up today

DrJohn wrote:
Has anyone seen the plots for a variety of cam shafts - I've always had my money on it being the cam profile as the cause/explanation?
I would love to try a more aggressive cam on mine and see how the drivability/ engine character changes, but can't justify £300 without some confidence I will like it!!


I think you're right about the cam John. It's a breathing issue, cam+head whether it be the 24 head or Turbo head IMO.

Comparing this car to a real GT though, you'd expect very similar characteristics and more power running 1 bar versus the ~0.78 bar of a GT. The rolling road makes power figures suspect but the torque curve should be accurate which is why I think Steve's probably right about the #4 turbine housing - shoving more boost through it will give great midrange torque but the size still limits outright power. Not an issue for a road car IMO as most people change up before 5000rpm.

I think I have the curve for Joakim's engine somewhere - that had a very aggressive cam and a fully worked head.

Author:  johnboy [ Sat Dec 02, 2017 10:16 pm ]
Post subject:  Re: So this turned up today

It's defiantly got torque :drool:
I'm going to send the car to Jkm performance in Portsmouth in the new year for a bit of reprogramming on the map and have them set it up with two programs one for road use and one for fast road and track use.
They can also fix the cold start and hot start issues with the hot start being the most anoying one when your In a petrol station. :whistle: and this car has no kjet which I can almost probably fix on the drive. :dope:
In the meantime the rad has a leak so that needs replacing and the bottom hose needs replacing, it's then going into aw motor sport next week for a look at the rear brakes they are binding so there going to be 're sealed and serviced I could do it myself but it's quicker to sort on a two post lift :smile:

Author:  johnboy [ Sat Dec 09, 2017 5:47 pm ]
Post subject:  Re: So this turned up today

a couple of hours on the ramps at aw motorsport on thursday to find out why the new rear brakes are binding and they found the hub is slightly oval and causing the hadbrake shoes to bind :bang: they have now been backed off a little and are better but i think ill find a new set at some point

Author:  simonpayne [ Sat Dec 30, 2017 7:09 pm ]
Post subject:  Re: So this turned up today

Just seen this John. Stunning machine. Cant wait to see it! Well done!

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