Different cam profiles on the same engine?
Different cam profiles on the same engine?
(OP)
Are there examples of engines that used different cam profiles on different cylinders of the same engine?
Obviously due to variable valve timing this would be an obsolete way to flatten the torque curve, but have engine designers in the past ever produced engines with different cam profiles on the same engine?
(Example: 1st and 2nd cylinder peak at 3000 rpm and 3rd and 4th cylinder peak at 5000 rpm.)
Obviously due to variable valve timing this would be an obsolete way to flatten the torque curve, but have engine designers in the past ever produced engines with different cam profiles on the same engine?
(Example: 1st and 2nd cylinder peak at 3000 rpm and 3rd and 4th cylinder peak at 5000 rpm.)





RE: Different cam profiles on the same engine?
RE: Different cam profiles on the same engine?
Similarly, the old VW bug's flat four has slightly retarded cam timing on the cylinder whose airflow is impeded by the oil cooler.
Mike Halloran
Pembroke Pines, FL, USA
RE: Different cam profiles on the same engine?
They have the ignition timing on # e cylinder retarded 2 deg distributor. This is built into the distributor cam.
# 3 is the front RH side when viewing the engine from the rear of the car. It is the cylinder that is under the OEM oil cooler, and runs hotter as in the factory set up, the oil cooler steal some of # 3's cooling air.
I found that if I removed the OEM cooler and fitted a much bigger, remote cooler and reworked the air ducts to even out and maximise the airflow, I could raise the compression about half a point, and slow the cooling fan, or use a smaller fan and therefore pickup both fuel economy and power you could feel in the seat of the pants.
Regards
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RE: Different cam profiles on the same engine?
Mike Halloran
Pembroke Pines, FL, USA
RE: Different cam profiles on the same engine?
I read some place that some stock car engine builders have been doing that for years. To compensate for different induction flow charateristics, and other cyl to cyl variables.
RE: Different cam profiles on the same engine?
This is to do with the cylinders which de activate.
It is rare to have this phenomenon on a modern production road engine as it could lead to un even amounts of residual gas content at idle speed/ or even different power contributions from each cylinder- this would not only lead to a rough idle, but could also make it difficult to calibrate good equal EGR rates per cylinder....
RE: Different cam profiles on the same engine?
RE: Different cam profiles on the same engine?
Eg cyl. #2-3 have richer mixture than #1-4 due to worse cooling.
IMO different cam profiles on differen cyls is not so good idea if you're after max power or efficiency (widely understood), as it will always mean compromises.
To make for different working conditions of each cylinders it is much easier to vary timing/fuelling (especially as it is done by the same ECU) saving the same cam profile (easier to manufacture) or each cylinder.
RE: Different cam profiles on the same engine?
RE: Different cam profiles on the same engine?
Pat, FYI, I used a VW exhaust profile on a 1594cc Lotus twincam engine's ex cam along with a 'custom' intake profile to develope in excess of 205hp with 50mm Webers, way back when. VW forged piston blanks, too. Fancy that.
Rod
RE: Different cam profiles on the same engine?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Different cam profiles on the same engine?
Oh, one more thing, the 50mm carbs were ok on the dyno but did not work on the track at all and we switched back to 45DCOE9's with 40 or 42 chokes as I recall. I think we "estimated" that the hp was something like 185/195 with the 45's.
Estimates based on a bad memory ;-( ?
Rod