Quote:
Originally Posted by Casper
Very few people realise the differences between a two valve motor and the 4 valve motor because it is rarely spoken about. Down low the two valve motor will stomp on any 4 valve of the same capacity (NA) but if the upper rpm limit is too low then the 4 valve loses out because it performs better at higher RPM. That MB and Nissan motors never worked properly in SC is not surprising given they were handicapped from day one by the 4 valve configuration.
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Is that 100% true in all cases? So a 1995 Corolla 16-valve 1.6L would have less low down torque than a 1995 VW-Golf 8 valve 1.6L?
It seems curious that almost all economy car engines -- including General Motors' own normally aspirated four cylinders -- would bother with a more expensive 16 valve layout if it didn't bring any significant benefits, even in low rpm tractability which is important in an economy car.
There are some engines like the VW 4-cylinder, the VW VR6, and the Alfa Romeo Busso V6, which came with both 2-valve per cylinder and later 4-valve per cylinder versions, so it would be curious to compare dyno plots for the two layouts.
Here's one:
8V VW GTI, tuned
16V VW GTI, tuned
It would seem the 15% loss in low rpm torque is worth the peak power being 15% superior. To compare engines of the same era, I'd guess you'd need to put a 16V Toyota 4AGE car on the dyno on the same day as the 8V VW GTI, to compare low rpm torque of the two 1.6L motors and observe the difference of two layouts between competitor engines.
[PS. Why aren't we racing interesting cars like Golfs and Corollas in the ATCC again?
https://www.youtube.com/watch?v=ebNBhr2ZWNE Their omission is most curious!]