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Excessive Fuel Consumption - 82 Turbo KJet

Murploid1

Murploid1

Member
Joined
Apr 6, 2017
Location
Houston, Texas
Hi Guys,

Aside from leaking fuel, and playing around with the CO mixture of the KJet system what would one look for when trying to assess why my car is so thirsty?!

From a mechanical perspective it has:
- New spark plugs & Cables
- Fresh oil change and filter
- New air filter
- Correctly inflated tires
- Fuel pumps that are producing a lot of pressure and both working
- Running it on 93 RON

I am mainly using it on the freeway (no AC as new compressor has yet to be installed) so very little start and stop, sitting at around 65-70mph off boost in OD (2500-3000rpm) and I am getting 16mpg?! Surely this car should manage at least 20mpg?!

I am not aware of any boost leaks, car is not short of power, seems to run just fine. No smoke from the exhaust unless I am higher up in the rev range and pushing it (5000rpm)

Also, I have a wide-band fitted and the car seems to be where it should from an AF ratio - 14-15 when cruising. Dips down to 13 when i come off the throttle.

Thoughts?

Nick
 
Kjets On a Plane said:
120psi of compression and a motor that's already dead? :rofl:

+ automatic 240 turbo being driven at 70mph?

Fuel pressures and injectors spray evenly? Injector o-rings?
Click to expand...

I thought the b21ft was a low compression engine and 120-130psi was normal? I am pretty happy with my compression numbers :)

I have installed new injectors and seals - zero leaks.
 
I should also add that the car will not start properly on all cylinders unless I turn on the ignition and let it sit for around 20 seconds (whether hot or cold) I can hear the fuel distributor clicking away, and the main fuel pump makes a ticking sound. I am now wondering if in fact the fuel pressure is low. Although once started it runs fine.

I had the fuel pressure checked (multiple places) - seemed to be within tolerance.

I am not convinced that adjusting the 3mm CO is changing anything. I unplugged the o2 sensor - this made the car VERY rich so that seems to be working. I can push down on the plate (push down 3mm wrench) and the engine cuts out. Adjusting it counterclockwise doesnt appear to be doing anything!?
 
Mine gets about 18 mpg on average when I drive it normally. If I keep my foot out of it, I can get it up to 20 mpg. Can't keep my foot out of it, so I buy more gas. I just accept it as normal and hope gas prices stay low.
 
I took my airbox apart and noticed that it was stuck on the hot side. There is no preheat pipe, but its still sucking in hot air.

I am going to get rid of that flap valve and re-route in some cold air and see if that helps.
 
my 245 N/A with slushbox and my aggressive driving gets 20/25 mpg

So.... especially you have turbo and manual... man check fuel leak, ratio, fuel pressure, vacuum leaks. Your brick is out of normal.
 
120psi if the starter is healthy/all else being equal is fairly terrible. A healthy B21FT should be 150-160ish.

That said, even aligned properly, no brakes dragging etc (lots of variables for fuel economy), in my auto box 240Ts when I first got my 244T it got about 16/21 (non IC not tuned up or sorted out for halfway right stage 0), and it was a DL no sunroof pretty light weight car with no A/C originally.

Only later with a thin HG did I get 17-18-24 pretty consistently (depending on how much city/highway/whatever) not really keeping my foot out of it, nothing on the roof, not towing, just commuting. Boost was turned up a little, intercooled, so i had more reasons to be thirsty, but also thin HG, slightly ported head, quiet 3" exhaust and ATP gate, stock otherwise. If the waste gate came unhooked, which it did once (as in flap all the way open, no boost possible), I got 19/26ish.

Autobox 240Ts are fairly thirsty, but worn out and out of tune, often a little or A LOT thirsty.
 
My 240 Turbo with M46 will do 25mpg on the freeway if I drive it gently, it did that with the original Kjet and it does about the same with Megasquirt. Going faster than about 60 causes a significant reduction in fuel economy but it still easily does 20mpg and I don't remember the last time it did as bad as 16.
 
James10952001 said:
My 240 Turbo with M46 will do 25mpg on the freeway if I drive it gently, it did that with the original Kjet and it does about the same with Megasquirt. Going faster than about 60 causes a significant reduction in fuel economy but it still easily does 20mpg and I don't remember the last time it did as bad as 16.
Click to expand...
I find that hard to believe with a turbo k-jet car as they were 16/20 new from the factory unless you made significant changes to improve the MPG.
 
what kind of fan is on the engine? If it's a visco clutch type fan check if it's locked on all of the time. That would rob about 10-15hp which you would need to compensate for with more throttle.
 
10-15 hp? I dunno, that sounds like it could be an exaggeration.

In any case, you should check out your fan clutch by carefully listening to the sound of the fan running. I recently replaced one that was obviously running the fan all the time, but with the engine stopped I could turn the fan just like normal- it was not seized up.
 
Tuff240 said:
I find that hard to believe with a turbo k-jet car as they were 16/20 new from the factory unless you made significant changes to improve the MPG.
Click to expand...

That was entirely stock, manual trans, 42 psi in the tires, just cruising on the freeway at about 60mph in overdrive, it was pretty consistent 25 mpg, US gallons. The 16/20 quote sounds like the slushbox numbers.
 
Harry Tuttle said:
10-15 hp? I dunno, that sounds like it could be an exaggeration.

In any case, you should check out your fan clutch by carefully listening to the sound of the fan running. I recently replaced one that was obviously running the fan all the time, but with the engine stopped I could turn the fan just like normal- it was not seized up.
Click to expand...
It's true. I had the fan almost permanently locked (I cut the thermostat spring down) on an old 86 245 driver I had to help with the A/C during summer. It made 73rwhp on a dyno. :lol:
 
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