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Hi,

I know I'm not a conventional poster, but could you lend a hand anyway?

I like to have fun driving, but be reasonably efficient, so I've got a Saab 900 (turbo 4-cylinder). I'm averaging 31MPG with largely city/rush hour highway driving, but I'd just assume tweak anything out of it I can (EPA is 21cty/28hwy, so I'm doing decent).

I'm wondering what I can do that will help mileage. I do the basics of looking far ahead while driving, coasting (or engine braking when applicable - 5speed manual), and accelerating/decelariting sparingly. I'm in Wisconsin, so I'm a little hesitant to get tires with to much of a low rolling resistance; after all I still need good traction in 5" of snow.

Because the car is a turbo, I realize there are some other options outside of a normal vehicle. Specifically, would a cold air intake, or intercooler help MPG? I know it helps performance by cooling the intake air, allowing a greater temperature change in the ignition of the cylinders. Does this also help fuel efficiency?

Cold air intake = fresh air
intercooler = recycled air from turbo

I've got a restrictive intake, was thinking about larger intake filter for cold air, wondering if this helps MPG or just HP :rolleyes:

Thanks

Posted this in Fuel Efficiency category first, realized this is probably a better spot for it.

Part modifications for MPG improvement?

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Hi,

I know I'm not a conventional poster, but could you lend a hand anyway?

I like to have fun driving, but be reasonably efficient, so I've got a Saab 900 (turbo 4-cylinder). I'm averaging 31MPG with largely city/rush hour highway driving, but I'd just assume tweak anything out of it I can (EPA is 21cty/28hwy, so I'm doing decent).

I'm wondering what I can do that will help mileage. I do the basics of looking far ahead while driving, coasting (or engine braking when applicable - 5speed manual), and accelerating/decelariting sparingly. I'm in Wisconsin, so I'm a little hesitant to get tires with to much of a low rolling resistance; after all I still need good traction in 5" of snow.

Because the car is a turbo, I realize there are some other options outside of a normal vehicle. Specifically, would a cold air intake, or intercooler help MPG ? I know it helps performance by cooling the intake air, allowing a greater temperature change in the ignition of the cylinders. Does this also help fuel efficiency?

Cold air intake = fresh air
intercooler = recycled air from turbo

I've got a restrictive intake, was thinking about larger intake filter for cold air, wondering if this helps MPG or just HP :rolleyes:

Thanks

Hey there Saab900! Welcome to CleanMPG. :)

With respect, the best way to get better FE is to simply stay out of the turbo's boost range. A CAI will help for hot climates, but actually, a warm-air intake will keep the engine running at NOT on less fuel. An intercooler will cool the air, but again you're looking for fuel efficiency, not power.

Simply put, keeping your Saab out of boost will do the best to boost your FE. And you don't even have to mod your car! :)

I do the basics of looking far ahead while driving, coasting (or engine braking when applicable - 5speed manual), and accelerating/decelariting sparingly. I'm in Wisconsin, so I'm a little hesitant to get tires with to much of a low rolling resistance; after all I still need good traction in 5" of snow.
Welcome to cleanmpg!
I agree with johnf514, and have three additional thoughts:
(1) avoid engine braking - even if fuel cuts off in decel with this car, you will lose coasting distance and even worse it gets you in the habit of using partial throttle closing to reduce speed gradually, which DOES use more fuel than going to neutral, letting the engine drop to idle, and using brakes
(2) raise your tire pressures to the sidewall max ratings, in stages if you're worried about doing it all at once - this will dramatically increase your coasting distances
(3) get some inexpensive steel rims (junkyard or buy them) and put proper snow tires on them for the winter, then get LRR tires for the spring/summer/fall and put them on your original rims - this will work better both ways!

Oh and try pulse and glide. I was rather rough at it initially but now am smooth enough that most people can't tell I'm doing it. Especially if I can match it to the ups and downs of the terrain.

Good luck!

Well the easy "mods" are


ScangaugeII - always helps.
Religious tire maintance - even if you don't get LRR, keep the tread and pressure even
Continual alignment checks - This is a huge factor in cars with a few miles under their belt.
Synthetic oil - I do it for engine life, but hear it helps. There is also some play with weight and viscosity, but I don't know much about it.
K&R Air filters - I don't play with these either, but I hear they help.
May be some ground effect kits to help reduce drag on the HW, but I like my Prius stock.


11011011

I only use engine braking on hills big enough that I would get going too fast without it. This is only used during rush-hour, because I've found it more effective than fighting with cars around me. (going down some hills, I catch up to cars in front of me to fast, then use engine breaking)

As for pulse and glide, does that really work for non-hybrid cars? Again, most of my issue is in traffic, but I'm reasonable about following distance to 'use' hills to my advantage does p&g add much?


As for hardware modifications, do anything like K&N air filters help due to improved airflow? I'm trying to start with the inexpensive hardware improvements (before new tires - I just bought the car, starting small)

As for pulse and glide, does that really work for non-hybrid cars? Again, most of my issue is in traffic, but I'm reasonable about following distance to 'use' hills to my advantage does p&g add much?
Absolutely! The idea is that you use your engine to accelerate briskly, a mode that burns fuel more efficiently than light throttle acceleration. IOW it uses more gas/minute for less time and also generates more kinetic energy per gallon burned. Then you coast in neutral, which burns very little fuel, or even engine-off, which burns zero fuel. Repeat over some range, usually dictated by what traffic around you will tolerate (less traffic => wider range). Your net mpg is lower than if you drove at constant speed. P&G in my Outback yields 33-36mph highway, and it's an aerodynamic lump with AWD.

Slowing down helps a lot too, plus driving slower is very relaxing once you get used to it.

As for hardware modifications, do anything like K&N air filters help due to improved airflow? I'm trying to start with the inexpensive hardware improvements (before new tires - I just bought the car, starting small)
Never tried K&N on a car but all the posts I've seen from people who have say no gain in mpg.

If you can afford $160 get a ScanGauge. It will show you what works and will quickly pay for itself in improved mpg.

Increasing tire pressures = $0

As for the engine braking, just be careful because it's oh so easy to backslide into using it all the time.

HTH!!

I merged the threads to put all the responses in one place. The only thing I can add beyond that is that I don't **think** anybody mentioned the detail that a ScanGauge will only work on vehicles from 1996-on. If this is a recent enough vehicle then it's highly recommended, as you will learn a great deal in a very short period of time.

The SAAB 900 was produced for model years 1978-1993. ScanGauge II won't help.

In conditions where you need to decelerate (like your down a steep grade example), engine braking is *very* effective *AND* efficient IF your car has fuel cut, which it probably does. (SAAB was one of the pioneers of electronic fuel control.) Verify in factory service manuals or SAAB 900 enthusiast sites. But the fuel will only cutoff for totally CLOSED throttle ABOVE a threshold RPM. If you leave your foot on the throttle (or, given the age of your car, any misadjustments as well) you might *NOT* be getting fuel cutoff. There's also a posting of a road test you can perform somewhere on the site to verify fuel cutoff. But I'm not finding it right now.

Intercooler *will* *NOT* help fuel economy. When the turbo isn't boosting, the intercooler won't have much effect OTHER than to restrict your intake more. This will HURT, not help. Only when the turbo is compressing the intake charge and HEATING it (a side effect of all compression) will the intercooler come into play.

Others here are right - keep RPMs low and that turbo *NOT* spooled will be the single biggest help to your FE. That's not a bug, it's a feature.

Everyone has overlooked another obvious one - you have a 15-20 year old car. Make sure it's tuned to spec.

On the intake side. More details on which year you've got. But SAAB was a *VERY* early adopter of what they called "Lambda" sensors (fuel/air ratio). This "closed loop" design keeps the air/fuel ratio constant. Colder air = denser air = more fuel. At idle, it'll cost you. Above idle, there's a tradeoff - colder air is more efficient for any given torque produced. At any given RPM you'll have a bit more torque (and HP), BUT you'll also tend to drive with the throttle slightly more closed - which will increase pumping losses. So, it's not an obvious yes or no.

-mr. bill

Thanks for the responses all.

To address your comments specifically Mr Bill, I've actually got a NG900 (new generation), built in 1997 - a predecessor to the eventual 9-3, so I could use a ScanGauge.
Also 'only' a 10 year old car. (I did have a 1990 Saab before).

As for the air intake, I guess it's a specific item regarding my car's design that was driving my question. Reading Saab BBs, the intake air box has a 2 1/2" outlet going to the throttle-body, but only a 2" inlet coming from the air intake filter, so this is a 'pinch point', creating increased resistance. Would increasing that size, and allowing the inlet air to come in more freely (with K&N or other similar free-flow filter), help MPG? Right now the car is having to pull pretty hard to get the air in through the restrictive filter.
The entire idea of 'cold air intake' I realize is an idea from performance tuning, and simply the jargon I thought would help describe where I was starting from in looking for a free-er flowing intake.

Maybe they made the inlet 2" and intake air box 2 1/2" for a reason. When you go from a larger diameter to a smaller one you increase velocity. Like putting your thumb on the end of a garden hose.

So, maybe the manufacturer had a reason for it.

Hi Saab900:

___Welcome to CleanMPG!

___Let us take some of the old school stuff you are discussing and throw it out the window! Unless you know of a way for an un-modded Ranger P/U truck to touch 85.4 mpg over 20 miles from dead cold as she did tonight before hitting the Interstate? IL. doesn’t have any mountains to coast down either ;)

___The basic through advanced techniques work in non-hybrids and diesels just as they do in hybrids. Better in some instances, worse in others. You just have to get to know your car, learn the techniques until you do not even think about them and let that SAAB of yours teach you her secrets. Afterwards, blowing out the EPA becomes as simple as turning the key … again and again and again in some instances :)

___Good Luck

___Wayne

turning the key … again and again and again in some instances :)

LOL -- no kidding! Been doing some of that myself lately. ;)

Seriously though, Saab900, listen to this guy. He definitely knows what he's talking about and I can guarantee he isn't using hyperbole when he throws out a number like 85.4mpg!!!

Check out the numbers in the mileage logs to get some idea what can be done with no mods other than raised tire pressure and an SG to give instant feedback. If you want to put a little elbow grease into it, you can get much more out of your car than any mods could ever give you.

Welcome and enjoy!!

The CAI moves the power band up the rpm scale . Meaning more gas pedal movement will be required to move the car at "Normal" driving speeds. Good for racing Not for FE.I'm sure there are some that show a slight gain more related to improper maintainence than better design. The air intake setups auto manufacturers design are capable of more cfm airflow than a typical engine needs . Change the filter as per the scheduled maintainence interval for your vehicle.
I've been debating the CAI idea myself for other reasons. The 05-07 Duratecs have a "lifetime" filter/housing good for 150k. Only thing about it is: it's *not* serviceable and proven already it doesn't last 150k! Dealer replacement =approx $400 . So when the OE filter begins to plug up , CAI or a modded airbox with replaceable paper filter is the answer.