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Discussion Starter · #1 ·
Car, or not run the A/C.???

Yesterday..doing 70mps with top down and showing exactly 3,000RPM.

Picked up wife, she wanted top up and A/C on. I complied...

Went down same interstate, 70 mph, but this time showing 3,300 to 3,400 Rpm, and engine sounding like it was straining its guts out...

What to do... :(:(:(
 

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Well, I assume if you tell your wife that she needs to lose weight, your decision to kick her out of the car or run the A/C may be made for you.....

I wouldn't think the RPM's would vary with the speed, only the amount of gasoline used would vary. Maybe you were in 5th the whole time (grasping at straws here) or your transmission was slipping?

I think the spider has a combined passenger weight of 400 - 420 lbs rating. How "sturdy" a girl is she?
 

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At 3300rpm you're right in a sweet place for power. If your car is not responsive, even with air running, something is wrong.
Best regards,
Pete
 

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Unless your transmission is slipping, rpm does not vary with mph for any given gear. If you were doing 70 mph @ 3k rpm, it will always be that speed/rpm for that gear regardless of the load placed on the engine.
 

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Discussion Starter · #5 ·
Really.???every time I put on

Unless your transmission is slipping, rpm does not vary with mph for any given gear. If you were doing 70 mph @ 3k rpm, it will always be that speed/rpm for that gear regardless of the load placed on the engine.
The A/c on any car, the RPM would drop, due to compressors kicking in. The car is a six speed manual, and I was in 6th gear. We both weigh about 180 # each... Could clutch be slipping??:confused:
 

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Well, I assume if you tell your wife that she needs to lose weight, your decision to kick her out of the car or run the A/C may be made for you.....

I wouldn't think the RPM's would vary with the speed, only the amount of gasoline used would vary. Maybe you were in 5th the whole time (grasping at straws here) or your transmission was slipping?

I think the spider has a combined passenger weight of 400 - 420 lbs rating. How "sturdy" a girl is she?
Too personal and inappropriate. Do you really believe that, say, an extra 100lbs here or there makes a difference on the street? Geez!!!
 

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Well having lived in Austin, not running A/C is not an option. I'm sure your wife understands that.
 

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Car, or not run the A/C.???

Yesterday..doing 70mps with top down and showing exactly 3,000RPM.

Picked up wife, she wanted top up and A/C on. I complied...

Went down same interstate, 70 mph, but this time showing 3,300 to 3,400 Rpm, and engine sounding like it was straining its guts out...

What to do... :(:(:(
With the top up you are bound to hear a lot more noise. I'm guessing the Tach. reading may have been an operator error.
 

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Discussion Starter · #9 ·
Next time I will shoot

With the top up you are bound to hear a lot more noise. I'm guessing the Tach. reading may have been an operator error.
A picture of the tachometer..of course the wife will be screaming...WTF are you doing...any suggestions on how I should answer?? LOL:D:D
 

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The A/c on any car, the RPM would drop, due to compressors kicking in. The car is a six speed manual, and I was in 6th gear. We both weigh about 180 # each... Could clutch be slipping??:confused:
Don't confuse loading the engine with gearing. With the clutch engaged (released), there is a direct connection between the engine crankshaft and the rear wheels. Basically, there is a relationship between speed and rpm in each gear (if you double the rpm, you will double the speed). In your case, 3k rpm = 70 mph so 6k rpm = 140 mph (assuming your engine will pull 6k rpm in 6th gear).

Go out and check you speed (in 6th) at different rpm's. Assuming your speedometer is accurate you should see the following:

1500 rpm = 35 mph
2000 rpm = 47 mph
2500 rpm = 58 mph
3500 rpm = 82 mph
 

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The rpm would only drop at idle but it doesn't vary much on these cars. And the AC certainly won't affect the rpms needed for any given speed on a manual transmission car unless you have something slipping. It would only affect the time needed (slightly) to get to such speed.







Unless your transmission is slipping, rpm does not vary with mph for any given gear. If you were doing 70 mph @ 3k rpm, it will always be that speed/rpm for that gear regardless of the load placed on the engine.
The A/c on any car, the RPM would drop, due to compressors kicking in. The car is a six speed manual, and I was in 6th gear. We both weigh about 180 # each... Could clutch be slipping??
 

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I do not know how it is possible to have differing gearing with or without air conditioning running and additional weight in a vehicle equipped with a manual transmission. the engine turning at 3k, the shifter in 6th gear the speed WILL be "70 mph". there is no way for the increased rpm not to have been translated into speed. this is a mechanical connection made through the drivetrain. if the connection were to be made through an automatic transmission there may have been slippage within the clutch packs, but if it were to occur with a manual there would be a distinct burning smell, and probably another clutch failure for us to speculate about....
 

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I checked this scenario this morning. In an Auto 70 mph is right at 2000 RPM. Air off or on made no difference. Sport mode kicked it up to 2600 RPM.
 

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:D


Kick wife out or not run A/C.?? Here is pic of my wife from our recent trip to Mexico...

Sooooo kicking her out of car is very very difficult...;););)
if that is to #180, now I understand why there was a variation in your sixth gear rpm / speed equation... #110 = #180, perhaps the numbers were just a little bit off?
 

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I set my cruise control to 70 mph and came in at 2900 RPM. Just to play with it a bit (we scientists do that sort of thing) I put it in sport mode, turned on the A/C and blasted it. No change in RPM's (none expected). Top was down too. I guess I could have rolled down the windows too, but you get the point. No change in RPM's with A/C on or off.
 

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She doesn't like a girl who minds the wind blowing her hair, although having the AC on would be nice to make sure the CAIs are working correctly. ;)
 

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Thread is closed.

This discussion is closed.
I don't know if we have any female members, but I can't imagine one not being offended by the way this went sideways.
best regards
Pete
 
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