This is odd
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Joined: 09-02-09
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From: Wisconsin
This is odd
This is somewhat odd, and from my understand of mechanics, damn near impossible....
I was driving home from work last night. I was in 4th gear. I was going about 50mph, and about 2500 RPM. When I noticed how fast I was going, I was a concerned that Id get pulled over as the speed limit is 40. So, I left off the gas, and pushed on the brake to slow down. I left the clutch engaged. However, when pushing the brake, the RPMs dropped off quicker then the speed. WTF? How in the name of Zuse's butthole is that possible? How is it that my clutch had NEGITIVE ammount of slippage? If my clutch was worn and slipping, the Speed would have dropped off faster then RPM due to the brakes being on the wheels.
The only other solution to this, is that the responce time for the spedometer is slower then for the tach. But why would that be? The only diffrenace between a tach and a spedomoeter is the lableing on the face of the gauge.
I was driving home from work last night. I was in 4th gear. I was going about 50mph, and about 2500 RPM. When I noticed how fast I was going, I was a concerned that Id get pulled over as the speed limit is 40. So, I left off the gas, and pushed on the brake to slow down. I left the clutch engaged. However, when pushing the brake, the RPMs dropped off quicker then the speed. WTF? How in the name of Zuse's butthole is that possible? How is it that my clutch had NEGITIVE ammount of slippage? If my clutch was worn and slipping, the Speed would have dropped off faster then RPM due to the brakes being on the wheels.
The only other solution to this, is that the responce time for the spedometer is slower then for the tach. But why would that be? The only diffrenace between a tach and a spedomoeter is the lableing on the face of the gauge.
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Joined: 09-25-08
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From: Depew, NY
This is somewhat odd, and from my understand of mechanics, damn near impossible....
I was driving home from work last night. I was in 4th gear. I was going about 50mph, and about 2500 RPM. When I noticed how fast I was going, I was a concerned that Id get pulled over as the speed limit is 40. So, I left off the gas, and pushed on the brake to slow down. I left the clutch engaged. However, when pushing the brake, the RPMs dropped off quicker then the speed. WTF? How in the name of Zuse's butthole is that possible? How is it that my clutch had NEGITIVE ammount of slippage? If my clutch was worn and slipping, the Speed would have dropped off faster then RPM due to the brakes being on the wheels.
The only other solution to this, is that the responce time for the spedometer is slower then for the tach. But why would that be? The only diffrenace between a tach and a spedomoeter is the lableing on the face of the gauge.
I was driving home from work last night. I was in 4th gear. I was going about 50mph, and about 2500 RPM. When I noticed how fast I was going, I was a concerned that Id get pulled over as the speed limit is 40. So, I left off the gas, and pushed on the brake to slow down. I left the clutch engaged. However, when pushing the brake, the RPMs dropped off quicker then the speed. WTF? How in the name of Zuse's butthole is that possible? How is it that my clutch had NEGITIVE ammount of slippage? If my clutch was worn and slipping, the Speed would have dropped off faster then RPM due to the brakes being on the wheels.
The only other solution to this, is that the responce time for the spedometer is slower then for the tach. But why would that be? The only diffrenace between a tach and a spedomoeter is the lableing on the face of the gauge.
5-Speed FGP F35 Transmission:
Type: Transverse front wheel drive, five-speed manual transaxle ( Optional with limited slip differential )
Engine range: 2.0L I-4 supercharged
Maximum engine torque: 200 lb-ft ( 271 Nm)
Maximum gearbox torque: 258 lb-ft ( 350 Nm )
Wheel+Tire Circumference: 2044mm
Gear ratios: MU3
First: 3.38
Second: 1.76
Third: 1.18
Fourth: 0.89
Fifth: 0.7
Reverse: 3.17
Final Drive Ratio: 4.04
Thread Starter
Senior Member
Joined: 09-02-09
Posts: 4,210
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From: Wisconsin
Doesnt really explain what happened. I noticed that on my gauges in 4th gear, the needles move together. Pointing at the same angle always. Makes downshifting into 4th revmatching easy 
but the RPM droped BELOW what it should have been for my speed drop. That is what confused me.
Thanks for the gear ratios though
one day I was going to try to do the math to figure it out
but the RPM droped BELOW what it should have been for my speed drop. That is what confused me.Thanks for the gear ratios though
one day I was going to try to do the math to figure it out
Senior Member
Joined: 09-25-08
Posts: 5,384
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From: Depew, NY
Doesnt really explain what happened. I noticed that on my gauges in 4th gear, the needles move together. Pointing at the same angle always. Makes downshifting into 4th revmatching easy but the RPM droped BELOW what it should have been for my speed drop. That is what confused me.
but the RPM droped BELOW what it should have been for my speed drop. That is what confused me.
Thread Starter
Senior Member
Joined: 09-02-09
Posts: 4,210
Likes: 2
From: Wisconsin
You don't need a 1:1 ratio to get the RPM gauge and MPH gauge to match up angles.
In 4th gear, they happen to match up.
If I redesign and recalibrate my MPH gauge, I could it to match up in 3rd gear angle for angle, or 5th gear, or 2nd gear i could get them t read the same angle.
I experimented abit more, and on a rapid deceleration with clutch engaged, once my vehical has stopped de-cellerating, the spedo meter was still moving. This tells me that it's an indication only lag. No big deal really,
but why does the RPM gauge have a faster responce time then the MPH gauge?
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