Novice Ignition MAP kPa question

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Adrenalin
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Novice Ignition MAP kPa question

Post by Adrenalin » Tue Dec 08, 2015 2:03 am

Hi,

I have a newbie ignition map question.

I have been playing with the map for my D21 Ka24e (standalone high energy ignition kit) with poor results (all road tested).
I've been looking at images of maps of this forum as well as on the net in general for reference and to get my head around my issues.

Question: Many of the maps I have seen (I think they are mega squirt) show the kPa scale on the left hand side starting from nominal 20kPa then scale up to around 220kPa. As far as I understand, most engines would run maximum 60kPa vacuum (absolute), so why would people map below this. Is this because their maps are not absolute reference? Would have thought that most systems would run 100kPa as atmospheric???

I can nominate minimum and maximum load point values on my map which translate to voltages from the MAP sensor.
So I have my map running from 60kPa up to 200kPa for my supercharged setup. I should alos mention my setup runs on dedicated LPG not petrol etc, so I can't use anyone else's maps as starting point. LPG needs a very different curve :violin: .

Any answers, feedback or comments would be much appreciated.
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Matt Cramer
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Re: Novice Ignition MAP kPa question

Post by Matt Cramer » Tue Dec 08, 2015 8:02 am

60 kPa would be idle vacuum on an aggressively cammed motor. Motors in less aggressive tune often will pull 40 kPa or lower, and you can often get the MAP to drop even lower if you lift off the throttle while cruising on the highway. I've seen some engines pull less than 20 kPa on the highway before.
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BigLoukaT
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Re: Novice Ignition MAP kPa question

Post by BigLoukaT » Tue Dec 08, 2015 8:44 am

To add to what Matt posted... Ka24e here, stock cam idling at 29-30 kpa on megasquirt.
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npx from 240sxforums wrote:i figure from my very limited knowledge about the 240 and under the hood about cars in general i would follow the sr20det trend.

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Adrenalin
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Re: Novice Ignition MAP kPa question

Post by Adrenalin » Tue Dec 08, 2015 2:05 pm

Thanks for the reply guys. After your comments and some more conversions i have realised i was looking at the 70kpa backward. 70 of 100kpa being 30kpa absolute rather than gauge. Thanks. Now to adjust my map.
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viewtopic.php?f=42&t=60135

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