WOT enrichment means that the computer was programmed to provide a bit of additional fuel at wide-open throttle, boosting HP over the cars that didn't have this. Only US-market 1992 model year cars (500E and 400E) had this "feature"; it was removed for 1993 and 1994 US-spec 500E/E500 and 400E/E420 cars, and from 1995 E420 cars.
On a 500E/E500 car, retrofitting a WOT LH computer is worth a dyno-tested 7-10 HP.
On a 400E/E420 car, retrofitting a WOT LH computer is worth a good 10-15 HP.
Of course, they are different computers for 5.0 and 4.2-liter cars.
It's simple to "retrofit" a later car with an earlier WOT-enriched LH computer, and it takes about 2 mins to do. Direct press-in to the CAN box. Easiest performance upgrade out there for our cars.
You can tell whether an LH computer has WOT or not, by the part number on it -- specifically the first three numbers.
ALL LH computers with part numbers with first three digits LESS THAN "014" DO have the WOT fuel enrichment. Some units with "014" part numbers DO have WOT; others do not. ALL LH computers with part numbers GREATER THAN "014" DO NOT have the WOT capability.
This unit I am selling, is one that happens to NOT have the WOT enrichment. I have another unit for sale, that DOES have the WOT enrichment, for just a few bucks more.
However, this unit IS specifically a part that was used for 400E/E420 applications ... not a W140 unit that was repurposed for 400E/E420 duty.
A couple of notes, though:
- In 98% of real-world driving, you will see EXACTLY ZERO DIFFERENCE between a WOT-enabled and non-WOT enabled LH computer. It's only when the throttle is floored, and kickdown activated, that the WOT kicks in. That's pretty rare, in reality.
- It still is an EXCELLENT idea to pick up a spare LH unit, particularly for long-term 400E/E420 and 500E/E500 owners. In recent years, we have started seeing notable/significant numbers of LH units failing, as evidenced by the dreaded "fuel relay clicking" under the passenger rear seat. When this fuel relay clicks, that means 99% of the time that the LH unit is failing; there can also be other running issues as well that go along with a failed LH unit.
- Generally speaking, any 5.0 liter LH unit from a W140 S-Class or LH-injected R129 SL (500SEL, S500, 500SEC, 1993-onward SL500) works fine in a 500E/E500 application. Again, only the model year 1992 500SEL/500SEC cars have the WOT.
Same thing goes for the W140 4.2-liter cars, with LH computers that work with the 400E/E420.
The R129s and W140s were spec'd with a different part number for the LH computers than the 500E and E500, but we have yet to see any difference in running characteristics or power generation over the "stock" 500E/E500 LH computers. Many folks have been using them for years with no issues, and they are SIGNIFICANTLY less expensive and more common than the 500E/E500 and 400E/E420 specific part number computers, if those can even be found anymore.
Hope this all helps. If you want my WOT-enabled unit, let me know. It's a nice upgrade if you have a 1993-1995 car; or a nice spare if you have a 1992 car.
Cheers,
Gerry
