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[minifreek]

Will a 3.2 crank fit a 3.0 and work 100% please

[Kevin Wood]

I'm afraid not. The stroke is different.

[chrisgixer]

Would, just out of interest, a combination of v engine parts give better compression on the 3.2?

I remember master saying the 3.2 and 2.6 had lower compression for some reason.

[Diamond Black Geezer]

Last I heard this required someone to try it - yes there is a different compression ratio but whether this would give any gain or simply spoil things elsewhere, not sure. Remember there's a computer there always trying to 'correct' things - a bit like the higher fuel pressure 'mod' - the engine will simply say 'oh, too much fuel - back off a bit' 3.2s/2.6s have the lowest compression iirc

[Kevin Wood]

Yes, you'd really need a big box of bits and play around until something fits.

You need to reduce the size of the combustion chambers to increase compression. Best potential is to fit a 2.5/2.6 head to a 3.2, IMHO. Might need to open the ports out a bit to bring the flow up to that of the original head, and fit the sodium filled exhaust valves of the larger engine. IIRC, the valves are the same size.

[chrisgixer]

Last I heard this required someone to try it - yes there is a different compression ratio but whether this would give any gain or simply spoil things elsewhere, not sure. Remember there's a computer there always trying to 'correct' things - a bit like the higher fuel pressure 'mod' - the engine will simply say 'oh, too much fuel - back off a bit' 3.2s/2.6s have the lowest compression iirc

Ecu doesn't control compression though. Obviously....

[Diamond Black Geezer]

No, no, indeed. My point being simply that if you alter something on a modern engine in order to 'make it go faster' there's often an ECU somewhere in the mix to compensate, so this need bearing in mind, is all.. 

[chrisgixer]

No, no, indeed. My point being simply that if you alter something on a modern engine in order to 'make it go faster' there's often an ECU somewhere in the mix to compensate, so this need bearing in mind, is all.. 

Indeed. An argument often reserved for the ins and outs of chavs fitting uprated fuel pressure regulators without touching any other part of the engine, as the Ecu will simply trim back injector duration to match the same lambda signal. As it would of course.

Compression however, if increased at least to match the 3.0 would in theory give a bigger bang for the same fuel air mixture. ...obviously needs to remain within limits but there's no obvious reason why the 3.2 needs less compression for .2 bigger cylinder capacity afaik.

[Kevin Wood]

Indeed. An argument often reserved for the ins and outs of chavs fitting uprated fuel pressure regulators without touching any other part of the engine, as the Ecu will simply trim back injector duration to match the same lambda signal. As it would of course.

Compression however, if increased at least to match the 3.0 would in theory give a bigger bang for the same fuel air mixture. ...obviously needs to remain within limits but there's no obvious reason why the 3.2 needs less compression for .2 bigger cylinder capacity afaik.

Yep, absolutely right. More compression will give you a little more power from the same charge of fuel in the cylinder, so the ECU will know no different. The only potential fly in the ointment is that the ignition map might not be ideal but, as long as it doesn't give so much advance that you get knocking with the higher compression (unlikely with only a modest increase), it probably won't lose you much.

[Kevin Wood]

.. and, of course, if LPG is your fuel, more compression can be accommodated easily due to its' high effective octane rating.

[Marks DTM Calib]

Ignition  no issue as the knock control will compensate.

ECU wont notice, the compression ratio was only lowered to reduce cylinder temperatures and hence NOx generation allowing removal of the EGR valve.

[chrisgixer]

Ignition  no issue as the knock control will compensate.

ECU wont notice, the compression ratio was only lowered to reduce cylinder temperatures and hence NOx generation allowing removal of the EGR valve.

Oh is see. But how very disappointing.

Makes it somewhat tricky to remove factory "fitted"  gubbins that purely exist to meet EU/emissions  regs. On a bike it's just re mapped with a filter(but not these days) and free flowing exhaust and bingo, an as Mr Honda/Yamaha/Kawasaki/Suzuki intended engine is ready to go. No flat spots or overly safe fuel fuel mixture. Just crisp throttle response and a few more bhp.

[VXL V6]

I always think back to Obi - 3.0 block with 3.0 heads (later ones with the reservations to allow the use of per bank dispacks) and 2.6/3.2 ECU (So Motronic 3.1.1), manual box and 2.6 standard diff. Or at least I think that was the spec.

That seemed a fab combination, 3rd gear just kept pulling from 20 Mph up to illegal digits with a constant flow of torque.

[chrisgixer]

Ignition  no issue as the knock control will compensate.

ECU wont notice, the compression ratio was only lowered to reduce cylinder temperatures and hence NOx generation allowing removal of the EGR valve.

Oh is see. But how very disappointing.

Makes it somewhat tricky to remove factory "fitted"  gubbins that purely exist to meet EU/emissions  regs. On a bike it's just re mapped with a filter(but not these days) and free flowing exhaust and bingo, an as Mr Honda/Yamaha/Kawasaki/Suzuki intended engine is ready to go. No flat spots or overly safe fuel fuel mixture. Just crisp throttle response and a few more bhp.

....and this is all because of cold starting?

[minifreek]

Errrrrrrrrm......

Thanks for the answer