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Classic Engines, Modern Fuel

Comments on Topic: Best curve for a given engine

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Submitted by Anonymous

Hi all,

I just added one more curve Just to advise that the published curves are not qualified. Nothing tells us if they are adapted to a given engine and modern fuel. A remark field would be desirable to anotate how the actual curve was obtained (standard, tuned with dyno, book reference, chance...) so as a user can chose a valid curve for its engine.


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Submitted by The Author

This is a very good point. Thank you.

I will add two fields to the advance curve.

The first will be a radio button to select the source of the curve. I suggest the options:

  • Published (from a reference, book or the internet)
  • Measured (on the car as per the instructions on this site)
  • Rolling road (best power measurement)

The second field will be a free text comment field.

Do you think this will meet your suggestion?

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Submitted by Rich

Hello Paul,

I too have added a curve, which was a programmed one I installed today, however the 'combustion chamber' section , doesn't have my option in it. The kent Ford crossflow mostly uses a Bowl in Piston as it's chamber rather than one in the head, my head is flat. Not sure if you would add that as a future addition or not.



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Submitted by The Author


I have added the option for "Dished Piston".

The reason I included these options was that ignition advance is dependent on turbulence in the cylinder. The more turbulence, the less advance that is needed. Boat shaped combustion chambers with a squish area improve turbulence. This is not necessarily the case with dished pistons or hemispherical heads.

In practice, I would imagine the performance of the dished pistons was very close to the hemisperical head, in that you have a summetric combustion chamber. I guess the reason Ford "put" the combustion chamber in the piston rather than the head was to reduce production costs. It is easier to turn a dish in a piston than cast and polish a domed area into the head.


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Submitted by Rich

Thank you Paul, I have updated my own curve with the new chamber type.

If I may post this giving full credit to Dave Andrews who wrote it, it does highlight as you say the differences in chamber shape to curve shape, there is a full explaination of this data in a short paper he wrote some time ago.

Type of chamber
Jaguar/Lotus Twin cam
'A' Series,'B' series
Pre Xflow
Max advance
Bowl in piston Xflow 35-37
Closed Pinto 38-40
Wedge Imp 36-38
Open Wedge
Pent-roof 4 valve
Rover V8
Vauxhall16v,Zetec,Cosworth YB

Also for those who run a different cam profile than suppied as standard he also writes...

Cam duration Advance Idle speed expected
270 10-12 600-800
280 12-14 900-1000
290 14-16 1000-1100
300 16-18 1100-1200
310+ 18-20 1100-1400


Please wait .....