thepest
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| posted on 18/4/10 at 03:14 PM |
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Increasing compression
My Question is, if you increase the compression ratio of an engine (IE change pistons or skimm block etc) how will that affect the mixture if
everything else remains as standard?
+EG: if you had an engine running on webers or standard EFi if you increase Compression ratio how will that affect the mixture?
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mookaloid
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| posted on 18/4/10 at 03:22 PM |
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Hi Mate
I would think you will need a richer mixture. The higher the compression ratio, the more it is likely to pink so you will need a richer mixture or a
higher octane fuel and probably you will need to change the timing too.
Cheers
Mark
"That thing you're thinking - it wont be that."
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brianthemagical
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| posted on 18/4/10 at 03:27 PM |
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Possibly. It depends a lot on the engine and set-up. Theoretically no, as the new charge is drawn in at the same AFR, and all the old charge is
expelled.
I doubt you'd notice it if the AFR did change.
Edit:are you asking if the AFR would need to be changed, or if with the same fueling the AFR will change?
[Edited on 18/4/10 by brianthemagical]
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thepest
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| posted on 18/4/10 at 03:37 PM |
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Yes, my question is would it require re-jetting or re-mapping... and if so would it required to be leaned off or enrichened?
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brianthemagical
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| posted on 18/4/10 at 03:43 PM |
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You'd be able to get away without a re-map, depending on what the CR's are. Ignition timing would possibly be OK, but there's a
chance it may det, depening on the engine. You'll probably find gains from a re-map though, and why go to the trouble of changing the CR without
a re-map.
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thepest
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| posted on 18/4/10 at 11:58 PM |
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Basically I have rebuilt a toyota 3s-gte engine. I have used the same exact parts (IE no upgrades) but its running incredibly rich under heavy load
& boost IE 10:1 AFR, I had skimmed the block and the head plus pocketed the pistons to suit CR. I obviously have done something wrong but cannot
figure what 
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brianthemagical
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| posted on 19/4/10 at 01:11 AM |
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What kind of managment/fueling does it use?
What kind of AFR's was before the rebuild?
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thepest
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| posted on 19/4/10 at 06:54 AM |
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Standard Management using an airflow meter not map. I used to have 11.7:1 now its way below 10:1 under boost... way to rich.
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