Megasquirt M116? Fuel Economy?

[JamesDean]

Hey everyone,

I was just having a discussion with my cousin on how if my 420SEL got better or equal mileage to my 190E I would just daily drive that, then I remembered about the Megasquirt EFI conversions that are common on m103/m102s...

I was wondering if anyone had any thought/experience with the same on a m116/7? What kind of economy gains would one expect to see?

Also if any one has done it on a m103, what kind of mpg gains did you see? Currently my 190E 3.0 gets about 24mpg at 65-75mph.

[Hit Man X]

I bet starting with that exhaust will help a bit... that 1-5/8" OD crossover pipe is not doing you any favors nor is that silly precat. Are your cams timed properly?

I seem to recall seeing someone pick up 44rwtq on a W116 with a 4.5L V8 with MS, which is a pile of power. Fuel econ will obviously go up as you are not stuck with all eight injectors firing at once, you should be able to go to four banks of two for semi sequential now since MS has evolved. Worst case, you would be two banks of four. Hell, emissions would drop significantly too.



Yes, that is the crossover pipe with the heatshield removed. Shocking.

[Adler]

What is the function of the exhaust crossover pipe? Noise reduction and smooth flow of gases or is it more ?
In four /six cylinder it seems to be a "V " joint to merge the exhausts .
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[Hit Man X]

Originally Posted by Adler

What is the function of the exhaust crossover pipe? Noise reduction and smooth flow of gases or is it more ?
In four /six cylinder it seems to be a "V " joint to merge the exhausts .
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That pipe connects the driver's cylinder bank to the passenger side. I will try to take a picture of this setup, it is awful (and comical) at best.

US M116/7 cars did not have true dual exhaust like the Euro versions, I guess this had something to do with cold start emissions as the CIS system is not known to be very efficient then... hence the addition of the AIR pump (to passify the EPA guys) and the precat right at the end of the manifold collection point.

MB should have used two precats and one main cat like GM did on the C4 TPI Corvettes. One more precat would not have been that much more expensive and I bet it would have boosted power and efficiency nicely. Like this:

MagnaFlow Catalytic Converters - 49-STATE & CANADA Catalytic Converters For Trucks, Suv's, American Muscle, Diesel, & Sport Compact Vehicles



All else I have seen when working on the top end of my old M116 and this M117 is that the heads appear to flow well as does the intake plenum. The throttle body is about 70mm, too. I am sure the camshafts are small, but one look at the exhaust will show you that is the major source of restriction.

The EZL has very low ignition timing advance (been on 87 fuel for years now) and I am pretty confident there is no power enrichment when the car goes WOT... well not to mention these cars do not seem to have true WOT from the factory, due to part of the linkage at the firewall side of the intake plenum.