PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Cylinder Volume

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Old Jul 14, 2010 | 04:23 PM
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rjparth's Avatar
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Default Cylinder Volume

I bought my car with a custom tune already on it. I'm now using HP Tuners VCM Editor to compare it with a stock tune for my car. I see, among the differences, that the cylinder volume is slightly different. Would there be any reason to change this as part of a custom tune?
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Old Jul 14, 2010 | 04:29 PM
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Originally Posted by rjparth
I bought my car with a custom tune already on it. I'm now using HP Tuners VCM Editor to compare it with a stock tune for my car. I see, among the differences, that the cylinder volume is slightly different. Would there be any reason to change this as part of a custom tune?
If it's stock displacement, then no, no reason to change it.

PS, if you change it back, you will most likely skew the fueling, as if it's already tuned, it's tuned to the displacement in the tune. If you change it back, you will need to figure out the percentage difference and then scale the airflow tables accordingly.

You should also verify your injector flow rate, and if it's off, and you decide to change it, again, you'll need to figure out the percentage it's off, and then scale the airflow tables by that percentage as well.

Or, wipe the slate clean, put it back to stock and start over. That's what I would recommend. Just read out the existing tune and save it, so you always have a reference to go back to.
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