Hot outside temp and bogging
Jun 24, 2003, 04:39 AM
#1
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Hot outside temp and bogging
Has anyone noticed the bogging since it is getting hotter outside?
Especially in stop/go traffic. I wish there were a remedy instead of having to work the clutch so much to take of in fear of stalling the engine.
Especially in stop/go traffic. I wish there were a remedy instead of having to work the clutch so much to take of in fear of stalling the engine.
Jun 24, 2003, 11:50 AM
#2
Re: Hot outside temp and bogging
Originally posted by Peazoo
Has anyone noticed the bogging since it is getting hotter outside?
Especially in stop/go traffic. I wish there were a remedy instead of having to work the clutch so much to take of in fear of stalling the engine.
Has anyone noticed the bogging since it is getting hotter outside?
Especially in stop/go traffic. I wish there were a remedy instead of having to work the clutch so much to take of in fear of stalling the engine.
.... All kdding aside, the hot summer temps are very hard on FI cars, the EVO seems to suffer even more than did my WRX 
Jun 24, 2003, 12:07 PM
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Hot, low density air is hard for anything (car, boat, plane) with nearly any type of engine. If it's a typical 95deg day with high humidity and you're at sea level (or close), the actual performance (or density altitude) might be around 7000ft. So imagine being higher up than Denver, you're going to notice lower performance. The turbo would have to spin even faster to generate the same boost pressure as on a lower temperature day so it takes somewhat of a efficiency hit as well.
Eventually in the hottest parts of the summer places such as Phoenix / Sky Harbor Airport get so hot that many types of jet aircraft can't take off during the day since they are so performance limited due to the ridiculous density altitude.
Eventually in the hottest parts of the summer places such as Phoenix / Sky Harbor Airport get so hot that many types of jet aircraft can't take off during the day since they are so performance limited due to the ridiculous density altitude.
Jun 25, 2003, 05:56 AM
#5
Originally posted by Peazoo
I understand it affects all cars. Doesn't give me much confidence to drive it hard though.
I understand it affects all cars. Doesn't give me much confidence to drive it hard though.
Jun 25, 2003, 06:20 AM
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Originally posted by silverEVO8
Actually, the car is probably safer at the hotter temps because the mixture will run richer (the air density is lower for a given amount of boost). I think the most dangerous times for detonation are those very cold, low humidity days, when the car makes lots of boost with high density air and the mixture is too lean... Please correct me if I'm wrong.
Actually, the car is probably safer at the hotter temps because the mixture will run richer (the air density is lower for a given amount of boost). I think the most dangerous times for detonation are those very cold, low humidity days, when the car makes lots of boost with high density air and the mixture is too lean... Please correct me if I'm wrong.
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Jun 25, 2003, 06:43 AM
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I believe the ECU compensates anyways for the air density. I was talking about lack of performance because of the temp. I don't wish to punch it vs a vette when its so hot outside.
Jun 25, 2003, 07:15 AM
#10
Originally posted by Peazoo
I believe the ECU compensates anyways for the air density. I was talking about lack of performance because of the temp. I don't wish to punch it vs a vette when its so hot outside.
I believe the ECU compensates anyways for the air density. I was talking about lack of performance because of the temp. I don't wish to punch it vs a vette when its so hot outside.
Jun 25, 2003, 09:06 AM
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Originally posted by silverEVO8
I believe the MAF measures air flow. It does not know how dense the air is. That is why it's so important to watch the EGTs and A/F ratios when the temps drop. The hot air has less O2 than cold air relative to volume, therefore the fuel adjustment based on the air mass would be richer for hot air than for the same mass of cold air.... Or at least that is what it seems to me.
I believe the MAF measures air flow. It does not know how dense the air is. That is why it's so important to watch the EGTs and A/F ratios when the temps drop. The hot air has less O2 than cold air relative to volume, therefore the fuel adjustment based on the air mass would be richer for hot air than for the same mass of cold air.... Or at least that is what it seems to me.
probably both.just checked manual. "When the engine is cold or operated at high altitudes, the ignition timing is slightly advanced to provide optimum performance." High altitude or low density air is the same thing. So we know at least the timing is advanced.
There's pretty good description of the MFI system starting on 13A-671 of the tech manual. Should help give an idea of the relationship between O2 sensors, Emissions system, Intake air tem sensor, Engine coolant temp sensors, CAS... hopefully someone that knows the ECU well can chime in with real world applications rather than me just quoting from a manual. Vendors maybe?...
Peazoo, the Evo already has low power in the lower rpm range. With increased air temps that power is weakened even more. this causing more bogging.
Thats what I am working on,I think I have made it work,95degree here and I am back at 19.3PSI with no bog down or lag
Last edited by mayhem; Jun 25, 2003 at 09:11 AM.