short shift, how short?

[lovemysan]

I get better in town mileage when shifting at very low rpms.

1-2 700-1000rpms
2-3 1100
3-4 1300
4-5 1500

level ground, downhill slightly less rpm, uphill slightly more rpm. The saturn pulls cleanly off idle in most situations

[slurp812]

Originally Posted by lovemysan

I get better in town mileage when shifting at very low rpms.

1-2 700-1000rpms
2-3 1100
3-4 1300
4-5 1500

level ground, downhill slightly less rpm, uphill slightly more rpm. The saturn pulls cleanly off idle in most situations

I guess it really depends on the vehicle! Theres no way I shift into 5th at 1500 rpms, no way. In 5th at 1500, it has a hard time accelerating on flat ground at all. But it is a jap car. they are more upper rpm HP, and not mucch bottom end. Its gutless below 2000 in any gear. Prefers 3000+. I will have to try a tank shifting at 3000, instead of my now usual 2500.

[Bill in Houston]

Hey, byobbq, say something intelligent about what this graph says about where to shift.

To me it seems to say that you would want to be asking for nearly the maximum torque, and shifting at about 2600 rpm, trying to keep the revs and the torque demand right on that region of the best BSFC.

[landspeed]

However the 'previous engine' had the most efficient areas not so tightly concentrated.

On my car with SuperMID, I have found that keeping the revs low does help fuel economy - seeming a lot more important than most other things!

And it is a 1.8 japanese engine!

[rvanengen]

Originally Posted by Bill in Houston

<snip>To me it seems to say that you would want to be asking for nearly the maximum torque, and shifting at about 2600 rpm, trying to keep the revs and the torque demand right on that region of the best BSFC.

Bill...does that mean I would be better keeping my car near it's torque peak...or just keeping it at the lowest % throttle that I can?

[Bill in Houston]

From the graph, it looks like you want to be pretty close to the peak, meaning stepping on it pretty hard... Still hoping for BBQ (or someone else) to confirm my understanding of the graph...

[rvanengen]

What kinda toyota do you have that motor in?

Do you know if you can find that kinda graph for a Mercedes 103.940 motor, or did you get this from a dyno?

[Bill in Houston]

Ya, exactly. BYOBBQ posted it. He has (or had) a Camry. I have not been able to find one for the K24 engine in my car. It seems to me that if the engine in every Accord, Element, RSX and TSX for the last 5 years doesn't have a BSFC chart that is findable on the internet, finding one for the Mer will be difficult...

[minic6]

Remember your gear ratios will make the biggest change between cars. A 3.5 versus a 4.1 will have to spread the shifts out further to get the same results. Also your trans ratios have much to do with it. I can right now be in 3rd gear in about 3 car lengths of the geo, it will be interesting to see what will change when the 14s are installed. Experiment and see it's the only real way to see. Japenese or European cars like to rev. american cars usually have lots of torque. Thats why in cars equiped with skip shift under 30&#37; throttle will go 1st to 4th.

[lovemysan]

Originally Posted by slurp812

I guess it really depends on the vehicle! Theres no way I shift into 5th at 1500 rpms, no way. In 5th at 1500, it has a hard time accelerating on flat ground at all. But it is a jap car. they are more upper rpm HP, and not mucch bottom end. Its gutless below 2000 in any gear. Prefers 3000+. I will have to try a tank shifting at 3000, instead of my now usual 2500.

My car is pretty gutless all over. Especially in 5th gear. Sometimes I shift and wait for the acceleration to happen. la la la, anyday now! That sort of thing. I tried the short shifting in an altima and it just wasn't compatible. Too much weight and not enough low end torque.

Thing biggest thing that will help you decide which method is a supermid or an SG2.

good luck