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Old 06-16-2011, 10:28 AM   #1
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Volvo project

I have been making some modifications to a 92 Volvo 940 (non-turbo) 2.4 ,Automatic 4 sp
When I first bought this 250,000 mile car last year the MPG was real bad .
I was getting 14 city and 20 hwy.. I feel it could do even better with some mods.. I installed a K and N cold air intake to help the engine breath better
and bough tires with a lower roll resistance this improved to 15 city 23 Hwy
I felt I could do better.. I run slightly higher tire pressure 35 rather than 32 psi.. Replaced the O2 sensor because it was slow to respond, A new CAT and
high prefomance muffler to improve flow That stepped me up to 19 city 26 Hwy... Swithced to a 5W 30 synthetic motor oil and Platunim plugs..
Other mods ... I wrapped the fuel tank with insulation to keep the road temprature of the fuel down, I wrapped the A/C acumulator with 5/16 stainless steel tubing and diverted the fuelrail return line over to it ,This helps to remove most of the heatcharge from the hot rail so the tank will maintain a lower temprature... On My trip to Austin Texas this week it is 104 deg , driving 65 MPH used the cruze control, I got 31.2 MPG Hwy Running the A/C on MAX all the way.. This may not be great Milage to everyone here ,But I was proud of it.... Me next step will be to lower the suspention 3 inches to give the car lower wind resistance .. Next road trip I'm not running any A/C to see if it pick up a few more MPG.... Ron Clark ,Weatherford,Tx
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Old 06-16-2011, 12:42 PM   #2
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Re: Volvo project

Welcome, Ron!

Some thoughts on your post:

K&N CAI: Done properly, no effect. Modern vehicles tend to already get free-flowing cold air with the factory intake system, as it's a free way to include more HP with the car. Your 1992 model might differ from more modern cars. Warm air is known to increase fuel economy in some cars (for a number of reasons I won't get into here); and an improperly setup intake upgrade often gets warm air from under the hood. Finally, anyone who is interested in fuel economy shouldn't be flowing enough air to encounter any resistance/obstruction in their intake.

Increased tire pressure: This is the most universal and cost-effective way to increase fuel economy. You should feel free to experiment with increasing all the way up to the tire's maximum, paying attention to ride, handling, traction, and wear.

Replace O2 sensor: If old (like, 250,000 miles old) and ineffective, then this will surely help.

Cat and muffler: As with intake, anyone concerned with fuel economy shouldn't be flowing enough to encounter any restriction. A system that restricts enough to reduce fuel economy for an economic driver would choke it off entirely at higher output. (Example: I had a converter failure in my 2008 VW that blocked it off severely; my MPG stayed about the same, but the car could barely reach highway speed.)

Fuel cooling: I can't say that I understand how this would help. A common discussion is fuel heating, which is poopooed as ineffective because at 14.7:1 the fuel just isn't a large enough portion of the intake charge for its temperature to have a measurable effect. That argument is countered with the suggestion of better atomization from warmer fuel. I'd be curious to hear the theory behind colder fuel increasing fuel economy.

Lowering: Often helps. Do you have a cost-effective way to do it? If you're trying to save fuel for the sake of saving money and invest $800 in suspension, don't hold your breath waiting for it to pay off; but if you have a free or near-free way to do it, it will almost certainly pay off.

Anyway, regardless of what should or shouldn't work (or whether it should wok in your car vs. other cars), I'm glad the effort is paying off and you're getting better fuel economy! Have you considered any economic driving techniques?
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Old 06-17-2011, 08:09 AM   #3
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Re: Volvo project

Thanks for the welcome ... I must go on record to say I have almost no idea what I'm doing , But I do it anyway..lol


The cold air concept.. I have an 05 Mustang GT with the 4.6 and I installed a
K N kit and it improved the over all throttle response can’t say Iv seen better fuel economy from the installation, the top out MPG was 27 hwy on a road trip running 87 octane wal mart gas.
I don’t drive it much ,its hard to behave your self with 300 HP under your foot..lol

I sometimes have a problem with the natural safety switch on the Volvo and it would only start in park , so I modified a remote starter switch I picked up at the auto parts store I installed a small toggle switch in the side of the handle and replace the two wire with a four wire cable , Mounted two relays under the hood on the firewall ,One relay will activate the starter solenoid when you squeeze the trigger switch and engage the starter (Warning ) the engine will crank in any gear ! … I hardwired the other relay into the B+ voltage on the fuel rail in the normally closed position so when it is activated by the toggle switch it effectively kills the fuel at the injectors and allows the ECU to remain live at all times ,it comes in handy at long red lights , I disconnected the cold start injector on the intake manifold so the engine has to crank over one revolution before the control module will see TDC from the crank sensor .. The kill switch works good on de-acceleration… Why fire injectors when you are stopping ? If the road speed drops below 10 MPH I have to use the trigger and restart again ..I don’t have a system down yet and I need some practice before use it every day .. Sometimes I forget to restart the engine at takeoff..lol
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Old 06-17-2011, 10:00 AM   #4
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Re: Volvo project

Yup, cold air definitely helps improve maximum power; it provides more air through increased density. The fuel injection system, of course, adds more fuel to compensate. With increased air and increased fuel you have increased power.

Modern cars, under some conditions, will cut fuel during deceleration exactly as you describe manually doing. Your car might do it too, although it is less likely than a more modern one. That function is called Deceleration Fuel Cut Off (DFCO). It's very cool that you've installed a manual fuel cutoff button that you can use more aggressively than the automated programming (which can't read the driver's mind and can't be allowed to affect driveability). I'm surprised it doesn't trigger a Check Engine Light.
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Old 06-18-2011, 09:07 PM   #5
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Re: Volvo project

air filter was useless investment.. You should have been able to average 20mpg in that car easily without changing anything about the car at all. If you can't, it means the car badly needs a tuneup. All those things you've listed you did to improve fuel economy helped but I feel are going to mask any issues that you may need to address.

Quote:
Originally Posted by theholycow View Post
Yup, cold air definitely helps improve maximum power; it provides more air through increased density. The fuel injection system, of course, adds more fuel to compensate. With increased air and increased fuel you have increased power.

Modern cars, under some conditions, will cut fuel during deceleration exactly as you describe manually doing. Your car might do it too, although it is less likely than a more modern one. That function is called Deceleration Fuel Cut Off (DFCO). It's very cool that you've installed a manual fuel cutoff button that you can use more aggressively than the automated programming (which can't read the driver's mind and can't be allowed to affect driveability). I'm surprised it doesn't trigger a Check Engine Light.
All fuel injected cars have deceleration fuel cut off.. The reason for this is that it reduces emissions immensely and is easy to implement..
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Old 06-18-2011, 11:50 PM   #6
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Re: Volvo project

You need to fix your intake thermostat. Its probably stuck on the hot side, killing ignition timing.
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Old 06-19-2011, 12:43 AM   #7
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Re: Volvo project

Indeed, assuming this beast has an intake thermostat as my 89' 740 has, you should replace it regardless. It's cheap through ipd usa and generally fails to the hot side. Interestingly, if you remove the pre-heat hose or related components altogether, the car's winter FE will SUCK. Mine went down to 10-12mpg's all the time without the preheat hose during winter.... May effect summer driving too, although to a less extent. My theory on that is that the ECU is expecting regulated intake air temps once the engine is warm. If it sees the engine is warm and the intake temp is too cold, it get's confused and dumps full to compensate. The 02 is a simple one wire job, after all. The ECU probably just goes into (stays in) open loop like it does when the engine is cold. Thus, crappy FE.

If the intake thermostat is stuck on one side or the other, too hot=severely retarded ignition timing, too cold=extra fuel.

Good job on the mods so far. K and N filters may actually help you in this specific application. If you feel so inclined, run a tank or two without it and a tank or two with to compare your results. If not, keep it and stop throwing paper air filters in the trash. If nothing else, you'll save yourself $20 every 3 months or whatever. Can't complain there. (yes, the volvo air filters are 15-20 low price filters in my area)

And yeah, what's the theory behind cold fuel?
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Old 06-19-2011, 04:42 AM   #8
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Re: Volvo project

Quote:
Originally Posted by ************* View Post
All fuel injected cars have deceleration fuel cut off.. The reason for this is that it reduces emissions immensely and is easy to implement..
I'm not sure if TBI cars from 20 years ago do...but either way, most do not use DFCO anywhere near as often as they should.

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Originally Posted by benfrogg View Post
If you feel so inclined, run a tank or two without it and a tank or two with to compare your results.
If it was me doing that, I know I'd never be able to trust those results unless they were blind testing.

Quote:
(yes, the volvo air filters are 15-20 low price filters in my area)
The K&N pays off very quickly at that price.
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Old 06-19-2011, 05:58 AM   #9
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Re: Volvo project

Quote:
Originally Posted by theholycow View Post
I'm not sure if TBI cars from 20 years ago do...but either way, most do not use DFCO anywhere near as often as they should.


If it was me doing that, I know I'd never be able to trust those results unless they were blind testing.



The K&N pays off very quickly at that price.
The fuel injected metro is throttle body injection and so is a lot of GM vehicles from the early to mid 90s and I know they have DFCO. The only vehicle I could imagine not having it would be like a 1974 VW Beetle that is Fuel injected but even then I think it has it.
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Old 06-19-2011, 06:46 AM   #10
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Re: Volvo project

Replacing the temperature sensors on the Volvo sounds like a good idea to me , the computer on this old car is primitive and I can’t use a scan tool to look at live data .. Just used a DVOM and watched the O2 cycle … Plug the jumper socket in and hold down the switch to read flash codes , binky,blinky… (Regina/lambda ) system."OBDII would make tech easy"
Thanks for the input ...Ron
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