slightly bigger and lighter turbo improve mpg? - PeachParts Mercedes-Benz Forum

benzdude42 · #1 09-12-2014, 02:33 AM

I'm looking to improve my 84 300sd to increase mileage with out doing massive hp improvements. I've already gone through the basics, valve adjustment, cleaned intake and ports, and EGR disabled. The highest I got was 32 mpg with 3 gallons of diesel from an empty tank. I wears wondering I put a newer turbo on her with a faster spool on, it would improve the mileage.

Stretch · #2 09-12-2014, 03:10 AM

I'd change the tyres - here in Europe they are all sold with ratings A-E ratings for noise and fuel economy etc. Apparently a few extra MPGs can be squeezed out that way.

Better quality fuel (if available) is also meant to help.

Decent oil change also helps.

At the end of the day you'd probably get the best results from fitting a more modern engine but you have to look at the bigger picture => how much money will you spend to pay less at the pumps...

winmutt · #3 09-12-2014, 07:22 AM

32mpg is very decent. My highest was 34 from ATL -> FL (downhill) in a hurricane (35mph on interstate) in my W123 with 2.88 rear and manual trans. I do not think you will get more than 32mpg without a different engine. More spool earlier on isn't really going to give you better fuel economy, you will be using more fuel earlier. If you want good fuel econ trade your SD for a 190D or something much newer (40mpg with 93 e300d for instance)

Mxfrank · #4 09-12-2014, 07:29 AM

Adding boost without adding fuel will actually DECREASE your fuel economy. It takes energy to pump that extra air into the cylinders, and energy to compress it.

winmutt · #5 09-12-2014, 07:52 AM

Quote:

Originally Posted by Mxfrank

Adding boost without adding fuel will actually DECREASE your fuel economy. It takes energy to pump that extra air into the cylinders, and energy to compress it.

If you notice, he said nothing about adding boost.

rscurtis · #6 09-12-2014, 09:53 AM

I wears wondering I put a newer turbo on her with a faster spool on, it would improve the mileage.

Probably not. I improved the mileage on my Dodge PU by going to a larger turbo that doesn't make boost until you need it. The stocker would make 1# with the engine idling in gear, the replacement is making 2-3 # cruising at 65 MPH. If you want more MPG, you have to lower the drive pressure, which is exactly what I did. IMO, you are already at the top of the fuel economy available for that car.

pmckechnie · #7 09-12-2014, 10:18 AM

Just a thought. If you disabled the turbo or lowered the boost would you get better mileage at the expence of less power?

PaulM

Simpler=Better · #8 09-12-2014, 10:27 AM

Going to a more efficient modern turbo can help, but only when you're boosting. I don't tihnk you're in the boost if you're taking it real slow on the highway.

mach4 · #9 09-12-2014, 10:36 AM

Quote:

Originally Posted by pmckechnie

Just a thought. If you disabled the turbo or lowered the boost would you get better mileage at the expence of less power?

I think that would be true, except the turbo would need to be removed, not just disabled. My understanding is that the purpose of the turbo is to provide more power for the same displacement, not increase efficiency.

For a given engine, the only way to increase mileage is to reduce road load - rolling friction, weight, aerodynamic drag, etc. The easiest and most effective way to significantly increase fuel efficiency is to drive 40 mph.

Other ways to increase mileage is to use hypermiling techniques - interesting, but not very practical. (I once squeezed 38mpg out of my Corvette on a trip from San Diego to San Jose and back. Interesting, but a lot of work, and not all that safe).

vstech · #10 09-12-2014, 10:48 AM

Simple answer is no.

Things that will improve mpg's have been offered. I'm sure there are more ways too.

Switch to the 85 torque converter will help performance.