Kold indsugning

[hasse]

Claus skrev:
\"..Lurer i baggrunden...på trods af jeg ikke rigtig kan se formålet, idet jeg tror at risikoen er for stor, så det ender med brændte stempler eller sodet topstykke.\"

Ja du har da ret.
Fordel-chance><ricisi-ulempe.

[hasse]

Fra Flyinmiata, Jeremy Ferber:

Om temperaturforskellen-højde for den:

\"..We don't KNOW if Mazda did, but we will assume that they do..\"

[Viggoman]

"..We don't KNOW if Mazda did, but we will assume that they do.."

Hvis de gjorde: så er der ikke så meget at hente.

Hvis de ikke gjorde: så har de været heldige at resulatet blev en ret velspillende motor.

Med al den brainware der er hældt i den bil tror jeg ikke de glemte at regne opvarming af indsugninsgluft frem til ventilerne med i ligningerne.

Men det er så en trossag.

[hasse]

Viggoman:

Du må se at få dig nogle dæk med bedre bid. Du kommer jo ingen steder.
Slå den op.
Du bli'r da forkølet af al den kolde luft.

[Viggoman]

Helt rigtigt, det var til at blive rundtosset af. Jeg stiger lige ud og får varmen igen......

[hasse]

Vi er vist færdige - indtil videre - med denne tråd.
Men pudsigt har jeg dd. fået en mail fra autotap.com.
Kan ikke finde et link på deres side til mailen, så jeg har taget noget ud af mailen:


Hi again everyone,

Mike Fahrion back in your inbox with today's topic - how your car's computer maintains the ideal fuel mixture under all conditions. It's pretty impressive when you think about it. In today's cars, regardless of temperature, altitude or mileage we've come to expect that we can basically start a car and go without any change in drivability. On top of that, today's engines are able to do that with considerably higher efficiency and dramatically lower emissions than ever before.

First let's take a quick look at what happens when you step on the gas. The computer reads the throttle position (TPS), checks the coolant temperature (ECT), checks the intake manifold air flow and pressure (MAF and MAP), intake air temperature (IAT) and engine RPM. With all that info the computer then performs a \"look-up\" function. Similar to finding a coordinate on a map, except this map has many more dimensions than horizontal and vertical! Once the computer finds the correct coordinate for all of those operating conditions, it finds the result it was looking for - exactly how much fuel to inject for that condition in order to get *almost* the perfect mixture, giving you the best performance, economy and lowest emissions. All of this is continuously recalculated, dozens of times per second.

Impressive! But why is it *almost* the perfect mixture? Because dozens of things could influence your engine to the point where that factory-programmed value isn't quite right. To \"close the loop\" of information flow, there is a program running on your car's computer that uses information from our friend the Oxygen Sensor to check if the mixture is right where it needs to be. If it's a little off, the computer uses that information to come up with a fudge factor. The name of that fudge factor is Long Term Fuel Trim (LTFT). That value is the amount of correction that the computer will automatically apply to the value that it looks-up. Measured in percent, we typically see stay well under + or - 10% when driving. If it gets over + or - 25%, the check engine light will turn on and a code is set telling you that the fudge factor has become excessive and your engine is running either abnormally rich or lean.

I've simplified this just a bit. Here are a couple of the complications (and there might be a few more that I haven't learned yet). There's another fuel trim called Short Term Fuel Trim. There are also a bunch of those lookup tables for different driving conditions, each one can have a separate fuel trim fudge factor.