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#254 - Understanding Torque and Power

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Ask questions about webinar lessons here. To see the Previous Webinars for a complete list of archives tuning webinars. 

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I did a quick look around, and couldn't find a spreadsheet to do the tractive effort per gear calculation, so thought I'd throw something together and share.

Hopefully it looks something like the example in the Article Andre mentioned: https://www.hpacademy.com/technical-articles/understanding-torque-and-horsepower-with-tractive-force/

Attached Files


One point worth mentioning is that most NA petrol engines develop around 100 to 120 NM per liter at peak torque which is a pretty good rule of thumb. If you know this then you can use this calculator to work out HP. http://wentec.com/unipower/calculators/power_torque.asp

Last point I will bet you a box of Kiwi beer that I can stop your motor cavitating at 9k using the existing water pump. As I said on the Youtube comment its a lot simpler than you think. If you want to find out how to sort it send me a email and you will be surprised how simple it is.


Oh do share -- pre-pressurise the coolant system?

Andre & everyone -

It was mentioned in the webinar that your Fuel Table should match your torque curve (in-that the engine is running at peak efficiency at peak torque).

Would this same concept be applicable to the Fuel Target Table as well? Or is there good reason to target slightly richer at higher RPMs?

Thank you in-advance

Generally you want to set the target at whatever produces the maximum reliable power. Now to get "reliable", you may want to cool the combustion temps at high RPMs as there is less time between cycles to transfer heat from the cylinder head.

I have not found there to be a significant difference in power with different fuel target depending on the RPM or torque level. For normally aspirated applications targeting Lambda values of 0.88 - 0.90 generally provides the maximum torque.

Back to topic, it may be simpler for some to plot just power curves in each gear ratio, as some dyno's just give that and it saves some messing around.

If you know the road speed, you can use that as d/t to directly work out the sheer/tractive force at the contact patch - that can also save a lot of messing around with final drive gearing, rolling diameters, etc.

Oh, while corrected is all very well for comparisons and BS bench racing - the raw numbers are what you're actually getting and using, so might be a good idea to stick to those?

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