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Looking to get better mileage 940se M90 swap

okoye

okoye

Well-known member
Joined
Jul 27, 2009
Location
Connecticut
I'm looking to get some better mileage out of my 940se I've currently got blue top injectors but I have green tops that I want to put in 440 cc. I'm using an ebay 50 trim, Npr, M cam, 5 speed m90, Mechanical fan and no I will not swap to electric fan.

Any suggestions?
 
What are your AFRs at cruise? The best mileage I've ever gotten with my 92 and TLAO chips was around 24 MPG highway (no lockup converter, AW71). I've never heard of a 7/9 series getting mpg in the 30s.
 
Well I averaged 14 mpg with my current setup. So anything better than that would be more than welcome.
 
use cruise control as much as you can.
drop a T-cam back in (like the engine was designed to have in the first place.). It will help spooling up that turbo giving you useable torque from as low as 2k rpm.
what axel ratio is your car using? 3.54:1 or taller will give good highway mileage because low cruising rpm at a given speed. Downside: a tall ratio dulls the performance.
convert to e-fan, any other fan is a parasitic powerdrain on the engine.
watch this video to learn how much power goes wasted in driving a mechanical fan
 
Janspeed said:
use cruise control as much as you can.
drop a T-cam back in (like the engine was designed to have in the first place.). It will help spooling up that turbo giving you useable torque from as low as 2k rpm.
what axel ratio is your car using? 3.54:1 or taller will give good highway mileage because low cruising rpm at a given speed. Downside: a tall ratio dulls the performance.
convert to e-fan, any other fan is a parasitic powerdrain on the engine.
watch this video to learn how much power goes wasted in driving a mechanical fan
Click to expand...

I've got a factory 3.73 in the car. A 3.54:1 is not readily available in my specific chassis because of the IRS. The only option I have is a 3.31 from the 1st gen 960.

My euro 960 turbo does have the 3.54 IRS rear end but I will not be tearing that car apart.

The engine came with an M cam and I haven't swapped my RSI stage 2 cam in yet.
 
So you want to keep your short rear gears, keep boost, and swap in a more aggressive cam, refuse to swap to an electric fan but you're asking how to get better mileage? :grrr: Might as well just pull the fan altogether, it is just uneccessary drag on the engine, after all. While you're at it, pull the A/C compressor, power steering, alternator, and even the water pump! They do drag on the engine, after all... If you really want to get crazy with it, pull out the whole interior, engine, and drivetrain. Leave the hubs bolted to the spindles but remove the brake rotors and calipers, as well as all of the shocks/struts. (Leave the springs in or you'll look like a total fool With your bumpers dragging on the ground) With this, you'll have a very lightweight package that will allow you to cruise in style (mostly down hill) while maintaining maximum scene points and fuel economy. Watch the money and fame roll in as you spend nothing on gas and people take your idea. (Copyright it beforehand and retire on the piles of cash you'll be making)
 
okoye said:
Well I averaged 14 mpg with my current setup. So anything better than that would be more than welcome.
Click to expand...

I might argue that if that's what your mileage is... there's something wrong.

I have a +t in a 245 with working AC and AW7x trans at ~14psi with IPD turbo cam 330cc injectors and TLAO and I'm at 18.79 US MPG for a 3 month data set (I use aCar on android and would recommend).

Car even has an exhaust leak currently and a wheel bearing going out (humming above 80). On Hydras with one tire low on air lol. #volvo

Also... my highway speed is 80.
 
EventuallyAyrton said:
So you want to keep your short rear gears, keep boost, and swap in a more aggressive cam, refuse to swap to an electric fan but you're asking how to get better mileage?
Click to expand...

EventuallyAyrton said:
:grrr: Might as well just pull the fan altogether, it is just uneccessary drag on the engine, after all. While you're at it, pull the A/C compressor, power steering, alternator, and even the water pump! They do drag on the engine, after all... If you really want to get crazy with it, pull out the whole interior, engine, and drivetrain. Leave the hubs bolted to the spindles but remove the brake rotors and calipers, as well as all of the shocks/struts. (Leave the springs in or you'll look like a total fool With your bumpers dragging on the ground) With this, you'll have a very lightweight package that will allow you to cruise in style (mostly down hill) while maintaining maximum scene points and fuel economy..........
Click to expand...

Let me address the first quarter of your post and not the latter...

The reason I keep the mechanical fan vs an electrical fan is that I've owned cars with both electric and mechanical fans. I prefer the mechanical fan as it's always cooling the engine as opposed to the electric fan that pops on when the car starts getting too hot.

As far as gears are concerned I will state once more. The only gear set that was available in America for the independent rear cars are the 3.31 or the 3.73.....
Europe got the 3.53 for their manual cars. I manual swapped my vehicle if that was somehow missed.

I do not want to change to a 3.31.

Point is that 275 miles out of a 21 gallon tank is horrible.
 
DET17 said:
What are your AFRs at cruise? The best mileage I've ever gotten with my 92 and TLAO chips was around 24 MPG highway (no lockup converter, AW71). I've never heard of a 7/9 series getting mpg in the 30s.
Click to expand...

I got 31 a few times driving 60-65ish in the flat with the cruise on in my 1990 744T M46 w/T25 turbo. 2.5" straight thru exhaust with 2 mufflers, basically totally stock otherwise. I think I maybe even had the a/c on. Stock hydras, stock size tires near new Yokohama fuel max performance something or others (drove real nice when newer).

It got 28-30 highway most of the time and 22 city/mixed banging around. Not driving crazy slow or doing anything special either. A/c s lot of the time, 10.5psi. I'd get 26-27 if I drove 75-80 and it was windy but even in traffic and beating on it never below 25 really mostly highway st the very worst.

Just keeping it tip top cheaply preventatively and s good stage 0 the neighbor did to it along with keeping tire pressure just right. , suspension tight, aligned etc...you know, boring stuff no one cares about here :lol:

Thet only had like 140k on it and 1 previous brain surgeon anal owner prior, super tight no leskdown/blowby or oil throwing original b230ft with no piston slap. Anal tightwad monied previous owner maintenance back to new. There was one tiny rattle of the shifter logo and he made them fix it and double check every ref miserable thing on that car st the dealer but I don't think they hated him as he did spend $ and do everything they recommended. I didn't personally do all the repairs but it was "in one extended family" since new and generally was a very good car.

idk the mech fan when it works was never a major factor. At some point I put and tropical fsn. clutch on the 744T.

The '86 745TD m46 I had would get high 20s city and 33-34 freeway.

Idk if a 940se will do quite as well, those things are heavyier and electrically laden.

So, uh, restore to stock? :lol:
Less of the modified kool-aid on the average probably tired/unknown old heap? :uh:

80mph, 17x10? steamroller # stupidheavywheels, average blow by special b230Ft (with an m-cam instead of a T? :lol:), no splash pan/air guides?, ??? Other strange modifications...why the surprise at 14mpg?
 
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The highest I ever got in my '87 744T with M46 was 29.5mpg. That was a whole tank of nearly all freeway driving, kept it right around 60mpg, stayed out of the boost entirely, let the car slow a bit up slopes and speed up on downhill stretches. Overall driving like there was an eggshell on the gas pedal. Engine was completely stock, stock cam, stock fuel, stock turbo, stock boost level, stock stock stock. 14MPG sounds like something is wrong, but if you manage to get 25mpg consistently you're doing pretty well. I don't drive a Volvo turbo for the fuel economy, although my mom's NA '86 M47 245 will do 30+ on the highway. 340k on the motor so it's probably nice and loose.
 
okoye said:
Let me address the first quarter of your post and not the latter...

The reason I keep the mechanical fan vs an electrical fan is that I've owned cars with both electric and mechanical fans. I prefer the mechanical fan as it's always cooling the engine as opposed to the electric fan that pops on when the car starts getting too hot.

As far as gears are concerned I will state once more. The only gear set that was available in America for the independent rear cars are the 3.31 or the 3.73.....
Europe got the 3.53 for their manual cars. I manual swapped my vehicle if that was somehow missed.

I do not want to change to a 3.31.

Point is that 275 miles out of a 21 gallon tank is horrible.
Click to expand...

Stop arguing pointless crap... what is actually wrong with your car?
 
sbabbs said:
James was that the one you used the custom ignition chip in that you got from me? If so then it wasn't stock...
Click to expand...

I tried that chip but it didn't have it in it those trips back From Seattle

It was just pretty flat and I had the cruise on, though i wasn't doing anything special :e-shrug:. In fact I was driving 65-70 for some of hr really boring flat stretches. I just stopped for gas from empty and filled up a few times on a long trip and did the math in that car often. It was a dry night, no head wind, flat. Road conditions were all good.

Got about the same fuel Econ as ever with the chip but had a little more power. Which isn't to downplay the chip...

Point is, no radical earth shattering modifications here.
Wasn't your 90 t25 m46 745 pretty easy on fuel when it was basically all stock?

I think tucking the exhaust closer to the floor and the 2.5. straight through mufflers did help slightly as I recall. Seemed to breathe s little easier.
You shouldn't *need* to modify what the factory did radically or drive in such a style as to be always thinking about fuel economy to get acceptable highway economy all else being equal...

Obviously if you are full boost-no boost and driving 80mph+ the whole time on the average tired motor shoving the steam roller tires around with other strange modifications...
Bonus points for cold weather to hurt fuel Econ some more.
Or i suppose extremely hot weather with the a/c on too...

At 14mpg you might as well just crush modified brick and drive an SUV or actual fast car from the factory...
 
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