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GT86 Cosworth
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Discussion Starter · #1 ·
Ok lets do it.

gt_sjo said:
GT86Owner said:
gt_sjo said:
You don't tend to tune based on gear.. the engine requires the same fuel whatever the gear.
Longer gearing and thus lower rpm will mean less losses as heat and sound, which will make it more efficient.

That isn't really how it works. But I don't want to
tie up another thread with mapping chat. Feel free to create a thread to
discuss if you want

My understanding:

Energy out = Energy in - losses

Higher rpm = higher losses due to friction (heat and noise),

which means for a constant speed (and output energy) you need to put more engergy in (fuel) if you have higher losses.

So if you make gearing shorter (higher rpm for a given speed) the car will be less efficient because thre will be more losses in the engine.

It does mention in the GT86 book in the dealer that tada-san wanted 150lbft of torque to keep rpms down and increase cruising fuel efficientcy.

Im no expert on engines. lets discuss!
 

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I'm not disputing that different gear ratios will have different effects on efficiency.. but it's not something you 'tune' or 'map'..

An engine doesn't know what gear you're in. All it knows is it needs X amount of fuel at Y amount of load (airflow) at Z amount of speed (rpm). It wants the same amount of fuel at XYZ irrelevant of what gear you're in.
 

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The usual swap would be a different final drive rather than individual gear ratios. I have no idea who would make these or whether there is a good Toyota/Subaru donor. To increase performance, you'll lose out on economy and your RPM/speed will be higher. This means it'll likely be less of a GT as such as you'll be revving it to cruise motorways etc....
I would only recommend it if you weren't likely to use it for long journeys and did trackdays alot.

Individual ratios are a different matter as you could make 1/2/3 and maybe even 4 quicker and keep 5 and 6 as they are for decent cruising. This is more likely to be expensive but allows better customisation
 
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