EFI vs transmission upgrade

[jagwit]

These old cars of ours are, with the benefit of 45 years of technological progress, rather compromised in terms of efficiency. The lack of vacuum timing advance on a standard V12 E-type is a good example.

Take my '74 Mk3 Jensen Interceptor as another example: 440 Cubic inches (7.2L) of engine but at our speed limit of 120km/h (75mph) this massive engine is turning over at 3100rpm in standard form (when fitted with the 3.07 diff)!

This very same car is now fitted with EFI (Megasquirt-2 controller) and a GM 4L60e transmission (Megasquirt GPIO controller). Now she is turing over at 2100rpm at 120km/h and I get 7.3km/L (17.17mpg US, 20.6mpg UK, 13.7L/100km) - open road. In standard form you would be lucky to get 4.5km/L - a huge improvement.

Was it the EFI or the transmission that brought about this improvement? Both.

Did EFI or the transmission bring about the biggest improvement? Transmission - by far!!!

So if you are wondering if you should rather spend money on EFI or a transmission upgrade, my answer is that spending money on a transmission upgrade* is imho BY FAR the better upgrade:

1. With a deep overdrive (typically 0.7), you will improve the car's fuel economy substantially;
2. You will have a much more pleasant drive with a more "relaxed sounding" engine;
3. Noise levels will be less;
4. Less heat is generated by the engine (per minute) and thus the cooling system will be less stressed;
5. In my view, the APPEAL of the car will also be improved, but perhaps not the value wrt originality.

Please note, it is far more economical to drive in top gear with your foot flat on the floor than in a lower gear with a light foot to maintain a certain speed.

* This statement may not apply in a country like the UK where driving in top gear is a rare occasion due to road congestion.

I owned a Series 3 V12 OTS, which I EFI'ed. The EFI really brought the engine "to life" BUT.... it left me pining for a transmission upgrade. Now I again have a V12 E-type (coupe), but now I find myself wishing the BW auto to pack up so I have an excuse to fit the GM 4L60e (or TH700). Even so, the engine has been fitted with vacuum advance and it does give better than 6km/L even though its spinning away at 3300rpm at 120km/h.