My '93 940 Turbo Wagon runs great, or so I thought. The only problem is the city mileage has been low - 13 to 14 mpg on average. Learned to live with it cuz the tailpipe was super clean, spark plugs medium brown and the idle rock steady. But last week took it in for a smog test to renew the registration and it failed. The smog numbers were slightly high but within range but the EVAP system had a leak, and it wasn't a faulty gas cap. They wanted $100 to pump colored gas into the system and find the leak. I passed on that and took it home. I looked under the car and the hose connecting the gas tank to the purge valve(on the charcoal canister) had slipped off. I did mention poor mileage to the smog mechanic and he said a leak will do that. He said at idle when the engine's not pulling vacuum the valve is closed and everything seems fine. But when you give it throttle and start pulling vacuum the purge valve opens and starts sucking fumes from the gas tank and feeds it to the intake manifold, downstream of the butterfly. In my case, instead of fumes it was feeding fresh air to the system, just like a vacuum leak. That thinned out the mixture and the ECU responded by richning the mixture and there went my mileage. As soon as I reconnected it I went out and tested it and my city mileage jumped up to 17 mpg! What it should be. The highway mileage only went up 1 mpg to 23, which seemed strange. But then I thought about it and it made sense. On the highway you're pretty much holding a steady rpm and not pulling much vacuum, unless you're going uphill. In town though, you're constantly on and off the throttle which will pull vacuum. I had it retested and it passed and the smog numbers had also dropped a bit. Surprising how something this simple can have such an effect.

 

I never ever saw 23 MPG with my 1992 turbo wagon. best on the highway was around 18mpg, and my evap and everything was copacetic.

 

In my case I put in a a 3:31 rear end. In your case it might be your right foot!

 

Huh, I have the stock rear end in my 740 sedan and can get 25 mpg highway without the cruse control, 26 when using cruse control. I only do about 70-75 mph though.

 

Is your car a non Turbo? If so, It has the AW71l transmission, which has a lock up torque converter. A locking torque converter acts somewhat like an overdrive. That's why the Turbos don't have them. The engine needs to keep revving for the turbo to spool up. Also why they have such a low rear end ratio. Both keep the turbo spinning and help reduce turbo lag. How many rpm's is your engine turning at 70 mph?

 

they dont put the L (locking) torque converter on american turbus because leadfoot american drivers would destroy them

non-turbos get around 25, maybe even 28 MPG on the highway, turbos get at best 18.. mileage goes down precipitously with speed, also a roof rack and anything on it will really knock down your MPG at elevated speeds

 

So let me get this right. Canadian drivers are more gentle with their cars?

 

didn't the Canadian's get the low pressure turbo, with significantly less torque ?

 

Not sure about that but I do know this - AW71L's were used in 6 cylinder Toyota Supras and Land Cruisers which had a lot more power and torque than any 940. Durability was not the issue.

 

the 71L was used on the 1982 Supra, 83+ used the 30-40E, which is the electronically shifted transmission used on the 960's. The 1982 Supra US edition had 145 hp and 155 lb·ft torque, I believe our B230FT volvos were 160 HP and 195 lb-ft.

 

and the Land Crusiers?

 

J50 was manual only. J60 used the A440F, which was never a volvo model

the A43D (no lockup, equiv to AW71) was used on 2WD 4cyl Toyota pickups, and even early 4 cyl tacomas, but I doubt any of these exceeded 200 ft-lbs.

 

Interesting. What about the B234f used in 740/940 GLE's? They used a lock up tranny(AW72L) and total hp and torque we're very close to Turbo models.

 

They used a AW72L, which is the same basic transmission with different ratios. the B234F have their horsepower and torque at higher RPMs so need 'lower' gearing (higher reduction ratios).

 

So, is there any country, in the world, where Volvo mated a full boost(6 lbs) turbo with a lock up torque converter? And secondly, why are they so much weaker? If you follow turbobricks there's been a lot of power upgrades done to the engines with these transmissions and I don't hear about them being ripped up, unless they go to the dragstrip.

And btw, how many rpms will a lockup converter drop engine speed?

 

I have heard that european B230FT or ET did get the AW71L. I believe it only locks in OD, and only when the RPMs are fairly matched up, and you're under light throttle, but there's a distinct 'clunk' when the lock engages. I've only had cars with electronic shifted transmissions and lockup, on those, they signal the ECU/ECM to back off the engine torque for a second while they lock or unlock, this greatly smooths the transition.

the biggest issue is when the torque converter lock DISengages when you step on it hard enough to force a downshift from OD, it has to disengage before it can drop out of OD

 

As far as durability, the AW72L was supposedly a light duty version of the 71 and it was used on the GLE(non turbo). Yet, it was also used on the 1992 to 1995 Mitsubishi Montero which had a 6 cylinder engine that did put out more HP and torgue than the turbo Volvos. Very confusing.

 

To clarify, it is a turbo and the AW71. I'm doing about 3k RPM at 70mph.

 

Boy that's hard to believe. Before I put a 3:31 rear end in mine it was also doing 3k rpm's at 70 mph. Now it's 2500 but I still don't get anywhere near the mileage you're getting. Wonder what's different? Mine is a wagon, which weighs about 150 lbs more but that shouldn't make that big a difference. Your mileage figures match a few non turbos I've heard about but never a turbo.

 

Well, I'll tell you what I do with my car:

Both pumps were replaced recently, as well as the main filter and strainer.
Tires are just regular street tires.
The alignment is checked twice a year and adjusted if necessary.
I run 93 octane fuel with a little of octane boost on each tank.
All suspension bushings have been replaced.
Shocks are recent.
Need to replace the air filter.

That's all that I can think of as far as what may change my fuel economy.