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6th December 2021, 16:49 | #11 |
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Putting A/C on means extra load on the engine, leading to a dip in RPM. This is countered by producing additional torque which stabilises the RPM back to the original level. The car thus needs additional air and fuel to produce the extra torque that is required to maintain the RPM at a constant level. Ideally, the air to fuel ration should remain at a constant 14.7 but I suspect will vary around this value in practice. This is very similar to what occurs when driving uphill.
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9th December 2021, 05:36 | #12 | |
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Quote:
The OP has a diesel Simon so we can forget all the talk about mixtures. The ECM will simply inject more fuel to return the engine revs back to the desired idle speed. |
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9th December 2021, 05:51 | #13 | |
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We are talking diesels here gents, so the air/fuel ratios will vary all over the place depending on engine load. 1000 to 1 at idle - no problem! The engine takes in the maximum charge of air on each inlet stroke. That amount will vary depending on the air density, how fast the turbo is spinning etc, but it will always be the maximum amount - there is no throttling involved, and that is why they fit a separate vacuum pump. |
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9th December 2021, 08:52 | #14 |
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Why did I not spot that he had a cdt?
Ah well, it was a good exchange of view anyway. My comment about torque still applies, it's just that only additional fuel is injected. |
10th December 2021, 07:21 | #15 |
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Clarification
It was David (b152krz), not the OP, who raised the question of mixture and he was referring to a claim in "something" he'd read. He also referred to his own car but without saying which one; diesel or petrol. I replied on the basis that it was his petrol KV6.
I hope that clears up the confusion. Simon
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10th December 2021, 21:21 | #16 | |
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When you put a greater load on the electrics your alternator has to put an extra kinetic load on the engine. This extra draw of energy is what slows the tick-over down until the ECU compensates for it. Don't worry all is well and doing what it is programed to do.-- |
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12th December 2021, 19:09 | #17 |
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