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Old Sep 15, 2016 | 07:00 PM
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Default MAP readings

Hi all,

I have done as much research as I can and I can't seem to find the answer I'm looking for. When I am around half throttle, my MAP readings are around 80kpa and around 75+ throttle I'm getting a reading of between 98-100kpa, with idle kpa being in the low 30s. Is this correct or is there some sort of problem? I feel like my truck (1971 c-10 with a 03 5.3) doesn't have as much power as it should and I'm wondering if a bad potential MAP reading could be the cause. If someone can let me know if these numbers I'm seeing are where they should be that would be great.


Thanks,
Avery
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Old Sep 15, 2016 | 09:07 PM
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That doesn't sound too out of whack. You do, however, need to post up the specifics of your combo. The more detail you provide, the more intelligent response you can receive.
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Old Sep 15, 2016 | 09:43 PM
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Sorry. Forgot to do that.

It is a bone stock 5.3l out of a 2003 Silverado with around 150k miles on it. Haven't done anything to it besides delete vats and the associated codes that came with swapping into my truck (emissions,tranny,rear o2s,etc)
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Old Sep 16, 2016 | 02:30 PM
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Originally Posted by aruss99
Hi all,

I have done as much research as I can and I can't seem to find the answer I'm looking for. When I am around half throttle, my MAP readings are around 80kpa and around 75+ throttle I'm getting a reading of between 98-100kpa, with idle kpa being in the low 30s. Is this correct or is there some sort of problem? I feel like my truck (1971 c-10 with a 03 5.3) doesn't have as much power as it should and I'm wondering if a bad potential MAP reading could be the cause. If someone can let me know if these numbers I'm seeing are where they should be that would be great.


Thanks,
Avery
KOEO the MAP should show around 100kPa depending on elevation. MAP reading at idle will greatly depend on the size of the camshaft. The lower the MAP reading at idle the more engine vacuum you have(which is a good thing)30 kpa is around 22 inches of vacuum which tells me the cam is probably stock or close to it.

As far as the 75kPa+ when driving that has to do with how much load the engine is under; Vehicle weight, gearing, tire size, power output, throttle position, grade of the roadway and a few other things will determine that.

At WOT your MAP kPa should be close to your KOEO MAP reading ideally. It's normally a little lower than that if you are running a plastic intake due to the restriction.
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Old Sep 16, 2016 | 02:32 PM
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With that said yes those numbers look normal.
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