Intake Manifold: MPG increase?? - PeachParts Mercedes-Benz Forum

Gregory · #1 11-12-2012, 02:34 PM

I used the point & shoot thermometer to determine that the #3 glow plug on the '87 190D 2.5 turbo is useless. The other exhaust ports were getting to 80F and 90F but #3 was still 30F, until the cylinder finally decided to start firing. #1 also seemed a bit slow to warm up.

So I got 2 glow plugs and then looked at the job. Its impossible to get to #3 without removing the intake manifold. I may as well get 3 more glow plugs and do all of them at the same time.

So long as I'm gonna take off the manifold, is there anything I can do (within reason) to improve MPG, even a bit?

My goal with this car is to approach 40 MPG if possible, with little tweaks.

I put on a K&N air filter last week. The old filter was so crapped up, that change should be worth 3 to 4 MPG. Before that, I made a copper plate to block the ERG.

Simpler=Better · #2 11-12-2012, 03:04 PM

Nothing that's going to net you a noticeable increase, I'm afraid. However, if you have the time to spare you might as well play with it.

You can do the general stuff, like port matching (assuming the stock manifold doesn't match the head) and adding a fillet/ smooth transition to any connections that can use it. You want mates surfaces to look like this(as seen on Ken Rockwell's site):

and couplings/ transitions to look like this:

Can the exhaust be wrapped easily? I'm unfamiliar with the 190D

Gregory · #3 11-12-2012, 04:39 PM

Thanks. Wrap the exhaust with what, and for how far along it? Looks like it wouldn't be difficult.

winmutt · #4 11-12-2012, 04:44 PM

Take the K&N off and put on a proper filter.

Gregory · #5 11-12-2012, 04:49 PM

Quote:

Originally Posted by winmutt

Take the K&N off and put on a proper filter.

If I do that, how much will the MPG increase?

sokoloff · #6 11-12-2012, 05:14 PM

Quote:

Originally Posted by Gregory

If I do that, how much will the MPG increase?

As much a K&N would give you and you'll get better filtering. Mercedes diesels get more air than they can use as it is. Adding a K&N will do nothing.

Gregory · #7 11-12-2012, 05:29 PM

Just removing the old clogged filter had to be an improvement. The PO must not have changed it in a really long while.

Still on the same tank of fuel, so can't calculate the MPG for that yet.

Simpler=Better · #8 11-12-2012, 05:51 PM

Fiberglass wrap-I've been using the cheapest stuff money can buy on eb*y on my motorcycle and truck, it hasn't caused the headers to implode despite crazy heat cycles and driving both in the rain. The main trick with the wrap it that you need to paint the manifold below it, and also paint the wrap itself with a heavy coat-otherwise you will have a TON of small fiberglass splinters EVERYWHERE.

On my bike it ended the stoplight overheating, quieted it down, and gave it a butt dyno improvement. The truck's underhood temps are significantly lower-can't comment on power because I changed from an unwrapped cast manifold to wrapped tubular header when I installed it.

Gregory · #9 11-12-2012, 06:01 PM

Quote:

Originally Posted by Simpler=Better

Fiberglass wrap-I've been using the cheapest stuff money can buy on eb*y on my motorcycle and truck, it hasn't caused the headers to implode despite crazy heat cycles and driving both in the rain. The main trick with the wrap it that you need to paint the manifold below it, and also paint the wrap itself with a heavy coat-otherwise you will have a TON of small fiberglass splinters EVERYWHERE.

On my bike it ended the stoplight overheating, quieted it down, and gave it a butt dyno improvement. The truck's underhood temps are significantly lower-can't comment on power because I changed from an unwrapped cast manifold to wrapped tubular header when I installed it.

Interesting. Why does wrapping the exhaust system increase MPG?

rscurtis · #10 11-12-2012, 06:02 PM

Quote:

Originally Posted by sokoloff

As much a K&N would give you and you'll get better filtering. Mercedes diesels get more air than they can use as it is. Adding a K&N will do nothing.

It will. It will give you an education on how to rebuild your engine when the dust from the K&N wears it out.

A friend is an original owner of a 190D 2.5T, and it will do almost 40 MPG if you can keep the speed reasonable.

Simpler=Better · #11 11-12-2012, 07:25 PM

Quote:

Originally Posted by Gregory

Interesting. Why does wrapping the exhaust system increase MPG?

It's another small gain modification-Lower temps underhood *should* help with efficiency, and hotter exhaust gases more faster-helping the turbo spool using less exhaust (slightly). Lower under hood temps should theoretically make plastics longer too.

Diesel911 · #12 11-12-2012, 07:54 PM

Quote:

Originally Posted by Gregory

Thanks. Wrap the exhaust with what, and for how far along it? Looks like it wouldn't be difficult.

For the Exhaust wrap to help it has to be on the Exhaust Manifold.

The makes special material to wrap the Manifold.
It is supposed to keep the exhaust gasses from cooling and hotter so the Turbo turns faster.

Another use for the Exhaust Pipe Wrap is to insulate the Manifold and Exhaust Pipes so that nothing around it gets heated up or burned. Often found in Marine use (Boats and Ships).

Back in the 1970s and 80s the claim was that if you could get rid of 400 pounds of Vehicle weight you chould save 1 mile per gallon.

t walgamuth · #13 11-13-2012, 06:23 AM

I've been driving Mercedes Diesels and other diesels a long time. The first thing to do is make sure your car and engine is running the way it was designed to run. I agree and would not spend my money on a K and N filter.

If you are taking off the intake, I'd clean it really good and make sure it is not obstructed in any way.

The usual ways to improve things like porting and polishing work on low tech sloppily built motors which were built to a price such as the old Chevy small block v8. The mercedes had all that stuff done at the factory along with steel crank and rods, and balanced bottom end.

There are three ways I have been successful in increasing mileage and both are trade offs that would not have been acceptalbe to the engineers who built the car back when it was new and being sold to someone who had a lot of money:
1. Running one muffler instead of two. This is mainly cosmetic but may get you a mpg or two...it will also allow a little growl which I enjoy.
2. Changing the gear ratio in the rear end. This is a lot of work and will only work if there is a higher ratio available second hand. I increased the mpg of my 240/300d 123 from 3 to 5 mpg this way.
3. Changing an automatic to a five speed manual is another way to increase your mpg maybe as much as 5 mpg.

If you hunger for more, check out Ecomodder forum for other ideas. Guys there have come up with a huge number of aerodynamic ideas.

Good luck with it!

Gregory · #14 11-13-2012, 07:48 AM

Thank you walgamuth. Running one muffler sounds good. The '88 190E in the pick&pull still has its diff. My car has some of the bushings gone bad in the rear suspension links. So sooner or later I'll be working on that end of the car. Would the gasser diff have a higher ratio than the diesel diff?

I also thought about tires one inch greater in diameter. For every turn of the wheel the car would go 3 inches further down the road.

lt1fire · #15 11-13-2012, 08:11 AM

Quote:

Originally Posted by Gregory

I also thought about tires one inch greater in diameter. For every turn of the wheel the car would go 3 inches further down the road.

and require more power to turn the heavier tire. I doubt this would work on a MB. It does generally work on more powerful diesels/gassers like a suburban or a cummins ram.

The problem with the mercedes are that they have been grossly misrepresented as to what mpg they actually get in craigslist ads and so on. In reality there is little you can do to increase MPG.

t walgamuth pretty much hit on most of them and then the aero mods..... an electric fan will do a little, more for city mpg than anything.

Maybe a slightly reworked pump for a bit more power.... nothing radical. In some underpowered cars an increase in power will get more mpg in just that you don't have to press the pedal down as far to get up to speed. (more to do with driving style than anything)