Manual transmission/shifting question

Hi;

I just bought my car this summer, and had never driven a manual before. I have shifting down fine, but had a question about shifting for optimal gas mileage and power.

Some stats I found say my car (2.0 SOHC) has 115hp @ 5400rpm and 122 torque @ 3200rpm.
I usually shift at about 3000 rpm, and was wondering when I should shift for best gas mileage.
Also, I know my car is slow, but if I felt the need to drive it as fast as possible some time, is it best to run it up to 5400rpm in each gear?

Any help or advice is appreciated, thanks ! :smile:

anyone ?? :confused:

Don't know about drivin for optimal gas mileage :grinyes: but for maximum performance yes you should shift just before the rev-limiter kicks in, and with enough practise you can make lighting fast shifts that will help make your car seem pretty damn quick.

LOL! I dont think he would have a rev limiter in it, unless your talking about something other than drag racing one's.

My lawnmower kinda has one, after it get's so high, it will kick back, and I have to adjust the RPM.

Every car has one. :shakehead

Every car has one. :shakehead
Thats not true. MOST every car has one

shifting at 3000rpm should be good, you drive a 4-banger does gas mileage really matter? There are so many things that effect gas mileage beisdes accleration. For optimal shift at high RPM(before rev-limiter)you should feel the power drop-off before redline - shift at that time. Nice smooth quick shift - there is no reason to slam gears even though it seems fun.

Accelerate hard on a low gear until you have reach the speed you want, then shift to the highest gear the engine runs well on. This means that you don't have to go through all gears.

If you want low gas mileage you don't need to be so careful when you shift, just accelerate fast and then keep you speed. If you need to brake, try using the engine. If you also want low emissions don't go over half throttle and around 3000 rpm (also depends on what engine you have).

For maximum performance you should go through all gears since that will give the highest mean power but it would also be easier on the gearbox than skipping a few gears.

thanks for the help everyone :)

If you need to brake, try using the engine? This is bad.

:werd:

Brakes are cheapier than clutches, transmissions, engines . . .

So what cars don't have a rev-limiter? Really old ones? And what happens if you don't back off? BANG?

I think you blow your gears or something if you go too fast in a particular gear ... my friend said he went 70 in 3rd or something and lost a gear, lol.

later he totalled his car :uhoh: idiot

The clutch should not be used to brake with, the engine is however an excellent brake. Newer fuel injected engines also shut off the fuel when the engine is used to brake and this can save a lot of fuel. This will also help to cool down the combustion chambers.

The engine will not break because it's used to brake the car, but if one change to the wrong gear it can (too high rpm), but this can happend both under upshift and downshift. If it happends it's usually the conrods that break and go through the engine block or the valves that hits the pistons.

I think you blow your gears or something if you go too fast in a particular gear ... my friend said he went 70 in 3rd or something and lost a gear, lol.

later he totalled his car :uhoh: idiot

No, you won't blow your gears. Gears usually fail because the torque or temperature is too high not because of high speed.


By the way... some cars can do 70 in 1st gear.

The clutch should not be used to brake with, the engine is however an excellent brake. Newer fuel injected engines also shut off the fuel when the engine is used to brake and this can save a lot of fuel. This will also help to cool down the combustion chambers.


How exactly would you use the clutch as a brake in the first place?

You should NOT use the engine as a brake. For one thing, you will be wearing out your clutch much sooner if you do. God invented brakes for braking so why the hell would you use the engine as a brake. :nono:
You're crazy. :shakehead

Using clutch as a brake - depress the clutch, let off the gas pedal (RPM fall to idle), then put the car into lower gear and gradually release the clutch. This way you, obvioulsy wear down the clutch.

Using engine as a brake - depress the clutch, but blip the gas pedal so that the engine revs at the same RPMs as with the car in a lower gear at that speed shifting into lower gear at the same time, and then release the clutch. This way clutch wear is minimal. Clear enough?

How exactly would you use the clutch as a brake in the first place?

You should NOT use the engine as a brake. For one thing, you will be wearing out your clutch much sooner if you do. God invented brakes for braking so why the hell would you use the engine as a brake. :nono:
You're crazy. :shakehead


Well, you have already got an explanation in ales post.
The only thing I can wondar now is where you learned to drive? The engine will act as a brake as soon you release the throttle, and the car manufacturers have built the engines in such a way that the injection of fuel is stopped during that time to save fuel.

Using clutch as a brake - depress the clutch, let off the gas pedal (RPM fall to idle), then put the car into lower gear and gradually release the clutch. This way you, obvioulsy wear down the clutch.

Using engine as a brake - depress the clutch, but blip the gas pedal so that the engine revs at the same RPMs as with the car in a lower gear at that speed shifting into lower gear at the same time, and then release the clutch. This way clutch wear is minimal. Clear enough?

Technically on both situations you described you are using the engine as a brake. Saying you use the clutch as a brake is confusing and incorrect as the clutch on it's own won't do any braking. That's what I ment when I asked how would you use the clutch as a brake.

I misunderstood what SaabJohan said earlier. He failed to mention blipping the throttle to match engine speed to road speed during downshifts. That is the only way you should do it.

Newer fuel injected engines also shut off the fuel when the engine is used to brake and this can save a lot of fuel. This will also help to cool down the combustion chambers.

Is this true? Can someone confirm this?

Information about Saab Trionic 7 engine management.

If any of the following criteria are fulfilled, fuel shut-off will take place:

- no power supply (+15 circuit)
- full throttle during starter motor cranking
- engine speed above 6200 rpm
- air mass/combustion exceeds 1300 mg/c
- immobilizer code faulty
- throttle turned by hand when engine running
- seriuos fault in throttle valve control
- a pedal position fault if engine speed exceeds 2200 rpm
- ignition discharge module not supplied with current
- engine speed above 1800 rpm and throttle pedal fully released. For manual gearboxes, this applies to 3rd, 4th and 5th gears. For automatic transmissions it applies to 2nd, 3rd and 4th gears. Fuel injection is reactivated at 1400 rpm.