terrible gas mileage b6t

[Chobobulous]

Since my rebuild I have been getting terrible gas mileage. About 24mpg. I knew swapping to a b6 would lower it some but almost 35% tells me something isn't right. I've checked the compression and im at 160 across all cylinders. The wide band normally reads 14ish during cruising. It will sometimes drop to the 10s if I let off the gas for a second or push on it just a little it will go back to the 14s. I haven't been hot rodding it around. I looked to see if there were any codes this evening and it flashed 1 8 and 17. I reset the ecu by leaving it unplugged for 5 minutes and it hasn't thrown any new ones yet was I in a sort of limp mode?

I changed so much at once I don't know where to start looking. New engine, I have new wheels and tires. Slightly larger 165 65r 14s. Aspire front brakes. Ive read that after a fresh rebuild it takes a while to get peak mpg. Im about 600 miles into the rebuild.

[skimsucka]

i get on high 32mpg occasional with foot stomp and at absolute worst 25mpg str8 romping the whole tank ahah which is usual!

[bhazard]

Somethings wrong. Used to average around 35 mpg with my b6t and still manage 40's on occasion. Look for gas leaks.

[Chobobulous]

I looked for loose gas lines and I didn't see any the rail holding the fuel injectors was a little lose but I tightened it up. Other than that I'm not seeing anything. I do not smell gasoline or anything when I am in the engine bay, but I know gas, especially warm gas, will evaporate quickly.

[Larry Hampton]

Keep your foot out of it? 8P

[Chobobulous]

Keep your foot out of it? 8P

: scared to put my foot in it! I don't need another 13mpg vehicle lol

[Movin]

Anything going on that could make your wide band read wrong ? Simple math says your car has a lot of extra drag, or the wide band reading does not jive with the MPG..something has an error. Are the plugs white - tan ?

[Chobobulous]

Anything going on that could make your wide band read wrong ? Simple math says your car has a lot of extra drag, or the wide band reading does not jive with the MPG..something has an error. Are the plugs white - tan ?

I don't have the grill in. I suppose that could make some difference. You are correct in saying it doesn't jive. I would lean toward afuel leak but I'm not seeing any anywhere.

My plugs are actually both colors. Super weird.

[Movin]

That all looks good but it shows you are dipping into power mode a bit often and you are driving easy. This would make me suspect the advance curve from the disty, at cruise you may not be getting the advance you need to stay at 14 or so. You may have the timing at idle set perfect but you may not be getting all you should get. By getting the part throttle power back you will stay lean under a lot more driving conditions before enrichment happens for acceleration. The plug will lose some of the darker color on the back side of the flame front. The plug looks good and it is a brand that has been working well. A timing light with the degree dial is the easiest way to check but sometimes it is better to physically test and inspect the advance parts. I think you will be really happy with this one!

[Chobobulous]

How do I check the advance curve. When iset the timing I use this procedure.

Ground sti port loosen bolts to the distributor.

Start car let it get to operating temperature.

Attach timing light to battery and to 1 spark plug

Verify the idle speed is 850+-50. If it is move to next step. If not, adjust idle air screw until it is.

Currently I have the timing set to 10° btdc. I set the advance on the timing light to 10 and then ensure it is lined up with the tdc mark. It's little easier for me to see.

If it is within spec remove sti ground.

Verify it is still at same timing. And 850+-50.

[Chobobulous]

So I have recalibrated my wide band and reset my computer. it now shows that while cruising I am getting 9.5-10.3. Using ratios and what not, if 14.7 gets you 40 then 10 will get you 27.2. Very close to the 25.7 I just got on my last tank. During low speed cruising I am still around a 14.7. Highway speeds 2k to 2.5k rpms is when it starts running rich. I am getting new intake piping from a member here to help insure I am not losing any air.

Would using b6 injectors with a b3 computer cause this much of a difference?

[M3NTAL]

I get 27-29 but I'm bored bigger valves 460cc bigger turbo blah blah

[bhazard]

So wait is this a B6 SOHC or a B6T? What engine, ECU, injectors, etc?

[Chobobulous]

So wait is this a B6 SOHC or a B6T? What engine, ECU, injectors, etc?

B6 sohc with a ko3 turbo

From the b6

Throttle body
Intake manifold
Injectors
Iac valve

From the b3
Ecu
Distributor
Thermostat housing
Vaf


I think that's everything.

[bhazard]

Okay so now I'm not so surprised at why its not working out right.

At least use the b6 ecu to start.