warmer weather =less go?

richie · 04-16-2001, 10:49 PM

Since the weather has been warm lately where I live my car seem at times low on power.The longer I drive the worse it gets.Does anybody else have this happen to them?Why does this happen?

84_GT350 · 04-17-2001, 02:31 AM

Well...generally cars run worse when it gets hot...but not enough to notice a big difference. I've noticed that happens with my car occassionally. It's usually a gasket or vacuum hose or something. When it's cold, the temperature keeps things from expanding (metal, rubber, etc) and then when it gets hotter you start to notice a problem. That could just be me though.

------------------
1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, MSD distributor, MSD coil, FMS 9mm wires, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s

smokedchevy · 04-19-2001, 12:09 PM

As a car gets hotter it runs worse, this shows up in E.T. at the drags, but on the street you probably shouldn't notice too big a difference. Also as you rcar gets hotter it is more prone to detonation. What kind of octane are you running?

302 LX Eric · 04-19-2001, 12:50 PM

Hot is a relative word in that your 5.0 engine will actually make less power when it is cold than when it is at proper operating tempature. Here is why: When you first start your car the engine is cold and therefore the computer runs in what is called "open loop" or said another way, the computer is dumping more fuel into the motor and making it run richer or less than optimal (14.7:1 A/F ratio). This is done to help the motor reach operating temp much quicker. Once the engine reaches operating temp. then the air/fuel ratio becomes more favorable for making power.

Although, I think your point may be that when it is very hot out (with a warmed up engine) your car feels like it has less power than when it is cooler (with a warmed up engine). Given this situation, yes, a warmer day will cut back on power due to the fact that the air is less dense and therefore contains less oxygen molecules per unit of air.

Hope this helps.
E

------------------
1991 5.0 LX Coupe - 38,000 miles

13.17 @ 106.14 mph w/ 2.138 60'

Mustangbelle306 · 04-19-2001, 04:52 PM

Funny, mine actually runs so much better in warm weather. My temp is screwy: it stays between the C and the N in normal allll the time. I don't know what's wrong with it, but in warm weather its like a different car. I guess maybe it runs at a more "normal" temp. Who knows? My pony is SO tempermental HA.

------------------
Elisha (Mustangbelle)
1994 GT: Cartech intake,4.10s, full exhaust, and pulleys.
Sold the 1986 LX sedan

http://www.geocities.com/mustangbelle_306
AOL name: GT306Chick

Dark Knight · 04-20-2001, 12:09 AM

colder air is denser, so you can get more in the cylinder.. more power... I lose about .4 or so in the 1/4 in the summer here in Az.. when it's 100* at night ;-(

------------------
84 convt,'95 302,AFR's, performer
3.55's, underdrives stock shorties
stock cam, 1.7's
14.06@100.21, 255RWHP on a hot day
265 on the mph/weight chart

Unit 5302 · 04-20-2001, 12:17 AM

302 LX Eric, every time the 5.0 get's floored it goes into "open loop." Yes the car does add more fuel when cold, but the the air coming into the engine is more dense as well. When the engine is cold less heat is transferred to the air as it makes it's way through the intake into the cylinder heads.

Also, the colder the intake air, the denser it is, which means more power. My SD car likes serious cold. I'm talking like -20*f. It gets crazy extra power when it gets super cold out.

As far as the notion your car will make less power at operating temp, depends on what you consider operating temp. Operating temp is just where the engine runs most efficient, not with the most power, which is why people like to keep their car running as little as possible when they are at the track making passes.

Capri306 · 04-20-2001, 12:43 AM

Haven't you guys ever heard of "corrected horsepower"??? A little something to do with barometric pressure and temperature.

I had the exact same problem with my 5.0 last fall. It ended up being the TFI module going bad. Luckily for me it was going slowly, so I could at least get to a parts store and install a new one. Check yours out and read the plugs.

...mebbe needs a T-stat & coolant change, tune up, and a timing check while you're at it???

------------------
Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch

[This message has been edited by Capri306 (edited 04-20-2001).]

04-16-2001, 10:49 PM	#1
richie Registered Member Join Date: Apr 2001 Posts: 47	warmer weather =less go? Since the weather has been warm lately where I live my car seem at times low on power.The longer I drive the worse it gets.Does anybody else have this happen to them?Why does this happen?

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04-17-2001, 02:31 AM	#2
84_GT350 Registered Member Join Date: Apr 1999 Location: Overland Park, KS, USA Posts: 1,631	Well...generally cars run worse when it gets hot...but not enough to notice a big difference. I've noticed that happens with my car occassionally. It's usually a gasket or vacuum hose or something. When it's cold, the temperature keeps things from expanding (metal, rubber, etc) and then when it gets hotter you start to notice a problem. That could just be me though. ------------------ 1984 1/2 GT350 (#842 Hatchback w/ T-tops), 302HO, Comp cams Xtreme Energy cam, Carter 625cfm carb, Weiand Stealth intake, MSD distributor, MSD coil, FMS 9mm wires, 1 5/8" MAC unequal shorties, 2 1/2" MAC Prochamber H-pipe, Flowmaster 2 chambers, KYBs, 16"x8" 4 lug Cobra Rs, Falken 245/45ZR16s

04-19-2001, 12:09 PM	#3
smokedchevy Registered Member Join Date: Jun 2000 Location: ventura,CA Posts: 438	As a car gets hotter it runs worse, this shows up in E.T. at the drags, but on the street you probably shouldn't notice too big a difference. Also as you rcar gets hotter it is more prone to detonation. What kind of octane are you running?

04-19-2001, 12:50 PM	#4
302 LX Eric or '331 LX Eric' Join Date: Jan 1999 Location: Columbus, Ohio Posts: 2,142	Hot is a relative word in that your 5.0 engine will actually make less power when it is cold than when it is at proper operating tempature. Here is why: When you first start your car the engine is cold and therefore the computer runs in what is called "open loop" or said another way, the computer is dumping more fuel into the motor and making it run richer or less than optimal (14.7:1 A/F ratio). This is done to help the motor reach operating temp much quicker. Once the engine reaches operating temp. then the air/fuel ratio becomes more favorable for making power. Although, I think your point may be that when it is very hot out (with a warmed up engine) your car feels like it has less power than when it is cooler (with a warmed up engine). Given this situation, yes, a warmer day will cut back on power due to the fact that the air is less dense and therefore contains less oxygen molecules per unit of air. Hope this helps. E ------------------ 1991 5.0 LX Coupe - 38,000 miles 13.17 @ 106.14 mph w/ 2.138 60'

04-19-2001, 04:52 PM	#5
Mustangbelle306 Yay for Chickys Join Date: Feb 2001 Posts: 1,532	Funny, mine actually runs so much better in warm weather. My temp is screwy: it stays between the C and the N in normal allll the time. I don't know what's wrong with it, but in warm weather its like a different car. I guess maybe it runs at a more "normal" temp. Who knows? My pony is SO tempermental HA. ------------------ Elisha (Mustangbelle) 1994 GT: Cartech intake,4.10s, full exhaust, and pulleys. Sold the 1986 LX sedan http://www.geocities.com/mustangbelle_306 AOL name: GT306Chick

04-20-2001, 12:09 AM	#6
Dark Knight Registered Member Join Date: Oct 1998 Location: Az Posts: 854	colder air is denser, so you can get more in the cylinder.. more power... I lose about .4 or so in the 1/4 in the summer here in Az.. when it's 100* at night ;-( ------------------ 84 convt,'95 302,AFR's, performer 3.55's, underdrives stock shorties stock cam, 1.7's 14.06@100.21, 255RWHP on a hot day 265 on the mph/weight chart

04-20-2001, 12:17 AM	#7
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	302 LX Eric, every time the 5.0 get's floored it goes into "open loop." Yes the car does add more fuel when cold, but the the air coming into the engine is more dense as well. When the engine is cold less heat is transferred to the air as it makes it's way through the intake into the cylinder heads. Also, the colder the intake air, the denser it is, which means more power. My SD car likes serious cold. I'm talking like -20*f. It gets crazy extra power when it gets super cold out. As far as the notion your car will make less power at operating temp, depends on what you consider operating temp. Operating temp is just where the engine runs most efficient, not with the most power, which is why people like to keep their car running as little as possible when they are at the track making passes.

04-20-2001, 12:43 AM	#8
Capri306 Moderator Join Date: Sep 1998 Location: Grand Rapids, Michigan, USA Posts: 1,001	Haven't you guys ever heard of "corrected horsepower"??? A little something to do with barometric pressure and temperature. I had the exact same problem with my 5.0 last fall. It ended up being the TFI module going bad. Luckily for me it was going slowly, so I could at least get to a parts store and install a new one. Check yours out and read the plugs. ...mebbe needs a T-stat & coolant change, tune up, and a timing check while you're at it??? ------------------ Capri306, Moderator, The Mustang Works Online 1979 Mercury Capri, 5.0L -- C4 -- 2.73 1987 Mustang LX Notch [This message has been edited by Capri306 (edited 04-20-2001).]