Adjusting for atmospheric pressure on natasp engine?

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sidewaysstu
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Joined: Sat Jul 21, 2012 3:25 am
ECU Model: S80 Pro

Adjusting for atmospheric pressure on natasp engine?

Post by sidewaysstu »

Interested in informed views on this as I've heard completely opposing views on this...

How much value is there in including a MAP sensor to adjust for variations in atmospheric pressure due to weather and elevation on a nat asp engine used in the UK? (IE Using TPS for load, MAP sensor connected to atmosphere not to inlet manifold).

Looking at a few rally venues in the UK elevation varies from 0 to 200m which is ~2% pressure difference.
Looking at some weather charts low to high seems to vary <1%
Oh - the car would be mapped at Northampton which is somewhere around 100m above sea level so pretty much in the middle of that range!

Moving from E48 to S80 Pro this autumn so easy to incorporate this in a new loom if its worth it.

Thanks
Stuart
lumley32
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Re: Adjusting for atmospheric pressure on natasp engine?

Post by lumley32 »

with the race bike engines we run air box pressure, this gives us the baro comp and accounts for any ram air, some of the races we do change altitude by 2000ft in a lap, so its worth having.

after all 2% in pressure diffrence is 2% fuel and 2% power!

should have said that air box is before the butterflies and you need to find a point of still air!

also the ram air is doable, we get an increase in air pressure from around 120 - 160mph
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ignitionautosport
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Re: Adjusting for atmospheric pressure on natasp engine?

Post by ignitionautosport »

If you make provision in your wiring harness for a MAP/BAP sensor as well as TPS (which you should anyway) then you'll be covered.
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stevieturbo
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Re: Adjusting for atmospheric pressure on natasp engine?

Post by stevieturbo »

IMO for future use, it's always worth populating all ecu pins. If there are unused sensor inputs or outputs etc, you can either leave a short lead and 3 or 2 pin plug somewhere pre-wired, so if you did decide to use them you can simply plug into them

It also leaves them flexible for you do mess around with. Pretty much all outputs would be covered with a 2 pin plug. 12v and the output.
If you wired the inputs to a 3 pin, 5v ground and signal, that again would cover almost anything you could ever want to plug into them

Most annoying thing is making a loom, running the car then a few days or weeks later thinking....mmm maybe I should have put this here, or added that there.
lumley32
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Re: Adjusting for atmospheric pressure on natasp engine?

Post by lumley32 »

very much agree with putting more in rather then less, but you do need some sort of pressure comp if your running tps as load its not a "put it in just in case" if you dont have pressure comps then your not even gonna get your fueling as good as carbs!!!
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ignitionautosport
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Re: Adjusting for atmospheric pressure on natasp engine?

Post by ignitionautosport »

oh I agree! I was thinking more along the lines of "put it in anyway".
I agree about also having a connector with spares in it, I do that on a lot of projects.
| '94 GSR Lancer | '96 Toyota Carib 20V | '83 Toyota Starlet | www.ignitionautosport.co.nz |
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