Hotter the weather = engine running leaner?
Thread Starter
Joined: Jan 2002
Posts: 249
Likes: 0
Hotter the weather = engine running leaner?
Does an engine run leaner when circuit racing/autocrossing during really hot weather as opposed to canyon racing at night? I know a hotter engine requires higher octane, just wasn't sure if it leans out from cool to hot weather.
Joined: Oct 2002
Posts: 582
Likes: 0
From: So Cal
Re: Hotter the weather = engine running leaner? (SloEG)
The simple answer: no.
The complete answer: the ECU has an IAT sensor (Intake Air Temperature), along with an 02 sensor and several others (such as MAP, or Manifold Absolute Pressure), meaning the ECU fuel delivery tables take into account changes in air density and temperature. Based upon sensory input the ECU dictates fuel delivery output, meaning that under any variety of commonly encountered circumstances, the ECU delivers the proper amount of fuel for the given circumstance. So again, no.
[Modified by texan, 1:28 AM 10/30/2002]
The complete answer: the ECU has an IAT sensor (Intake Air Temperature), along with an 02 sensor and several others (such as MAP, or Manifold Absolute Pressure), meaning the ECU fuel delivery tables take into account changes in air density and temperature. Based upon sensory input the ECU dictates fuel delivery output, meaning that under any variety of commonly encountered circumstances, the ECU delivers the proper amount of fuel for the given circumstance. So again, no.
[Modified by texan, 1:28 AM 10/30/2002]
Joined: Feb 2002
Posts: 432
Likes: 0
From: Long Island, US
Re: Hotter the weather = engine running leaner? (SloEG)
OK, this is from a carbureted motorcycle perspective, but it does technically apply (though on an EFI vehicle your ECU will compensate and you don't have to do anything).
In warm weather, the air is less dense, so to maintain the proper air/fuel ratio, you would set the mixture leaner. The opposite is true in cold weather...the air is more dense so the air/fuel mixture needs to be richened. This usually isn't much of an issue on 4-strokes, but is very important on a 2-stroke. Again, not particularly relevant to fuel-injected vehicles aside from the fact that the concepts are the same.
In warm weather, the air is less dense, so to maintain the proper air/fuel ratio, you would set the mixture leaner. The opposite is true in cold weather...the air is more dense so the air/fuel mixture needs to be richened. This usually isn't much of an issue on 4-strokes, but is very important on a 2-stroke. Again, not particularly relevant to fuel-injected vehicles aside from the fact that the concepts are the same.
Joined: Feb 2002
Posts: 432
Likes: 0
From: Long Island, US
Re: Hotter the weather = engine running leaner? (SloEG)
It might...I'm a carbs guy so I'm hardly an authority on it. My concern would be that the stock ECU is probably tuned toward the lowest emissions with stock equipment, and as such might not have the adjustment range to compensate for bolt-ons and maintain a correct air/fuel ratio. Best way to find out is an air/fuel ratio gauge if you've got access to one...another good way is to check the spark plugs. There are lots of web pages out there with pictures of what plugs should and shouldn't look like.
Thread
Thread Starter
Forum
Replies
Last Post
