View Single Post
Old 05-07-2001, 12:34 AM
JimF's Avatar
JimF JimF is offline
'94 S500: only 793 sold!
Join Date: Mar 2001
Location: San Diego, CA
Posts: 1,924
Why WW?

My point of 80/20 mixture and WW was to lower the operating engine temperature from 110C to something like 90-95C. The reason is not based on 'myth' but maintaining engine performance with the gas we have in CA (91 octane max).

Per WW: Coolant Effects on Performance
Under moderate load conditions, each percent glycol raises cylinder head temperatures by 1F. 50% glycol raises head temperatures by 45F. This increase in temperature will raise the octane required for trace knock levels by typically 3.5 octane numbers. A car equipped with a knock sensors (my S500) will retard the timing to compensate for the increase in octane requirement by approximately 5, which will reduce the maximum brake torque by about 2.1%.

Agreed that there is a "TOO" cool engine temperature but, per MB specs, anything past 80C is OK and that temp or greater is where "warm" engine tests are run.

If you can achieve a temperature difference as mentioned above (110C to 90C), that gives a 68F engine temperature difference. That roughly amounts to 8 LESS of retarded timing. Guess why I like the lower temperature operation?

So if you can get close to that, the car's happy, and it has much more power! This makes me happy!
Regards . . . . JimF
'94 S500 Cpe

Visit my Mercedes Web Page
Reply With Quote