I want to run an idea past you guys.... - PeachParts Mercedes-Benz Forum

PanzerSD · #1 02-15-2006, 12:45 AM

My mechanic was talking to me today about a Subaru WRX and he tried to tell me that they get decent gas mileage, I know for a fact that they don't. then he jokingly piped up if you keep the Boost at 0. and it got me thinking..

If I can rig up a system in which I can flip a switch and a vaccume solenoid trips the wastegate, in effect turning off the turbo? so if I'm tooling around town, and don't really need any great power or accelleration, I can have it off? is opening the wastegate bad for the wastegate?

or can this be done by tapping into the overboost protection circuit?

Brian Carlton · #2 02-15-2006, 01:01 AM

The turbo doesn't function around town if you keep the rpm's below 2200 or so. If you don't ask the engine for more power, it will easily shift below this speed. If the acceleration you get is not sufficient, then you press further down and the rpm's climb higher and the turbo provides more air and the ALDA provides more fuel.

Why do you need any more modifications than what you already have?

Attempting to cut fuel use by eliminating boost is not at all necessary and probably won't yield any fuel economy benefits.

It's a diesel........not a gasser.

PanzerSD · #3 02-15-2006, 01:31 AM

On the highway, is the turbo going full tilt? if I were cruising on the highway, and I wanted more fuel economy, cuz i know a non-turbo engine will get more than a turbocharged engine.

Anyway, I'm just curious...i'm always thinking of crap like this, more switches to flip when i start my car I guess

speedy300Dturbo · #4 02-15-2006, 01:34 AM

Quote:

Originally Posted by Got_The_Benz

My mechanic was talking to me today about a Subaru WRX and he tried to tell me that they get decent gas mileage, I know for a fact that they don't.

Just checked Fueleconomy.gov, and the WRX (2.0L turbo) gets 20/27 according to the EPA rating, and 22 combined. That's not too bad for a pocket-rocket type car, and isn't much worse than the typical OM617 equipped car.

Addicted · #5 02-15-2006, 01:42 AM

hmmmmmm,

Maybe I need some clarification and had this question about the difference between a gasser and a diesel.

I thought the whole reason they stuck Turbo's on Big Rigs was becuase of the added Fuel economy/power they provided.

Does a supercharger for a gasser do the same or decrease mileage?

Sounds like something I could google but since I saw this post I thought I would ask here.

#6 02-15-2006, 01:45 AM

Suprised nobody has mentioned this yet...

...you will get WORSE fuel economy (I would venture) if you ran the car without any boost at all. Around town you are into the boost more often than you think (partial boost) and this helps make the engine more efficent. If you are putting in the proper amount of air for the proper amount of fuel, you will be getting the best possible mileage. Cutting either of those will start to suffer with mixed driving.

Now if you want to TRY an experiment, remove the ALDA line from the overboost protection valve and plug it properly. You will now drive around with non-boost fuel. The off idle will be similar yet when you need the power you will find yourself mashing it to the floor to get going....and thus...using a similar amount of fuel anyway except having it come on too late to be as fuel efficent as it would have origionally.

I could only see gains from running with no turbo working and making boost if you were ALWAYS at low rpm's and the slight turbo backpressure was hurting you....but at these RPM that pressure cannot be that much...

BTW in a gasser they have to meter fuel with the boost at exact quantities...and since they are adding more fuel for the boost they tend to suffer on mileage when people are "really into the boost"...

...but then again with exact driving conditions with one making boost and one not, they should be realitively comparable. Its rather subjective to compare when driving styles are being factored in

PanzerSD · #7 02-15-2006, 02:01 AM

I Stand corrected, Thanks guys, for putting that potentially expensive AND destructive idea of mine to sleep

So, really, the only really effective modification I can do to the turbocharger to make it better is to leave it alone? LOL

Because Gasser meters air, and a diesel Meters Fuel.....I get it now, I had it, but somehow I lost it....ok....

#8 02-15-2006, 02:13 AM

Quote:

Originally Posted by Got_The_Benz

I Stand corrected, Thanks guys, for putting that potentially expensive AND destructive idea of mine to sleep

Hehe no worries. Hairbrained ideas are what fuels the future

As far as helping out your in town MPG...get your ALDA adjusted properly and have a good clean air filter. Also making sure your tranny is tip top and not having a bad alignment can help a little.

Anything you can do to help the off idle power and such is actually helping your engine become more efficent and thus helping out MPG numbers. Many believe that tweaking the ALDA to add fuel will hurt you but the truth of the matter is that if you drive realitively consistantly, it will actually help

It helped mine.

PanzerSD · #9 02-15-2006, 02:18 AM

Right now, I'm thinking Propane Injection, sounds like a viable power adder...

MUAHAHAHA!

#10 02-15-2006, 02:19 AM

Quote:

Originally Posted by Got_The_Benz

Right now, I'm thinking Propane Injection, sounds like a viable power adder...

MUAHAHAHA!

Pyrometer first

speedy300Dturbo · #11 02-15-2006, 02:32 AM

Quote:

Originally Posted by Brandon314159

Many believe that tweaking the ALDA to add fuel will hurt you but the truth of the matter is that if you drive realitively consistantly, it will actually help

Part of the reason for this belief is rooted in the aftermath of ALDA tweakage. Some cars respond exceptionally well and the drivers find themselves hauling a lot more ass, thus burning more fuel.

#12 02-15-2006, 02:34 AM

Quote:

Originally Posted by speedy300Dturbo

drivers find themselves hauling a lot more ass, thus burning more fuel.

Guilty as charged!

240Demon · #13 02-15-2006, 02:52 AM

Turbochargers, especially in Diesels, and effectively increase the engine's efficiency. A higher volume of air and fuel is introduced into the combustion chamber per cycle, therefore making more power per revolution than with a naturally aspirated engine.

btw...Turbo Subarus get pretty decent mileage, I have gotten 28mpg with my Turbo Legacy before...

I still miss the 240D!

t walgamuth · #14 02-15-2006, 05:32 AM

i had an 85 300sd for a couple of years. when i first got it it was very doggy but got really great mileage. on the highway i got 29 on a trip once driving the way i always do. but it just wouldnt accelerate right. i knew something was wrong. i could hear the turbo spooling up.

i took it to the dealer and their service guy told me that it was fine. i said you are crazy, come take a ride with me. i drove out on the highway and at 60 kicked it down and floored it. the motor made more noise but almost no acceleration.

so he said yeah that isnt right. but they couldnt figure it out. duuuuh.

so i took it to a small indie that specialized in mbs that was highly recommended and about 3 hours away. the mechanic found the cracked plastic line to the alda in two minutes.

so if the alda is unhooked it will drive about like an automatic 240 or maybe even slower, but it didnt seem to hurt anything and the mileage was excellent.

and with it hooked back up the car was transformed and the mileage dropped back where it should be expected mid twenties on the highway.

tom w

deerefanatic · #15 02-15-2006, 08:14 AM

Quote:

Originally Posted by Brandon314159

As far as helping out your in town MPG...get your ALDA adjusted properly and have a good clean air filter.............

How often (mileage) should you change the AF? I usually always figured 15,000 miles (valve adjust intervals) but the local AutoZone has 6,000 printed on their shopping bags..

Mine has a good 13,000 on it now (put it on in June when the car was bought...)

I routinely only get about 21.5-23.5 MPG per tank, mixed driving, though I took it on a 1 hour trip doing between 72-80 and then intown only to go back home at the same hi speeds. That fillup got me 25.4 mpg. Doing 60 on the two lanes for 100 miles to my grandparents will net me about 28.

Do these numbers sound about right?

In case you're wondering, yes, I do drive slightly hard, but not really hard. (I.E. I go easy enough that I have a good "smoke reserve" for when I need it!)