Fuel Economy and Vacuum Pump

[JTodd]

My vacuum pump was making a lot of noise, so I replaced the turbo waste gate actuator with a manual one. I did not replace or remove the pump. I have noticed a significant decline in fuel economy, and I don't seem to hear the turbo spoil as I did before the pump started going bad. In addition to the manual actuator, is there something else that needs to be done to totally remove the vacuum system from the rest of the system?

For comparison, fuel economy was high teens (17 or 18), but latest fill up was under 15. Same driving. I know winter blend will cause a decline, but this seems extreme.

[Hubert]

Avg a few tanks and see what happens.

Is the vac pump starting to drag appreciably? Probably depends on your driving habits and where you cruise (rpm and fuelrate). My understanding is the vac system lowers boost at light fuelrates near 1800-2000 rpm. This is the sweet spot. And during light throttle there is no need for boost anyway its just a restriction to exhaust due to turbo ineffeciency. Where do you cruise most of the time? Do you know what boost was before and after? Boost in and of itself is only good for EGT and power. Making boost usually means you are burning fuel and under load such that you have extra left over heat in exhaust and the turbo harnesses it (it makes a restriction to exhaust gasses to do this). Its my understanding there is a little gray area when boost is not helpful for economy during light driving and one reason GM went to the variable wastegate.

[Hubert]

OR

Something is odd and there is another problem. Most say they hear the turbo louder with the turbo master as the wastegate stays shut more and the turbo "slips" a little air through the turbo to create some whistle. I get more whistle just off idle going up or down with the TM than with vac control iirc.

[JTodd]

I am running open exhaust with a highly trimmed airbox. Before the vacuum pump started to go, I heard a considerable amount of turbo spoiling. The pump started to go, making a lot of ticking or clacking noise when running, so I opted for a turbo master. After the installation, I almost never hear the turbo whine.

[DaveBr]

I don't see anywhere if you have a boost pressure gauge. You need to know how much boost is being produced so you can adjust accordingly.

[JTodd]

I don't have a boost gauge, which admittedly would help. Until then a question I have is about whether there is more necessary to remove the vacuum pump completely from the system other than the turbo-master? I plugged the line from the pump to the now missing waste gate actuator, but is there a computer modification necessary as well?

I have not noticed much additional smoke on acceleration, but I don't tend to jump on it, so that might not mean much.

[DaveBr]

If the smoke is white it would indicate unburnt fuel which would probably indicate the wastegate is opening to soon dumping your boost pressure. You really need that gauge to really find out what's going on. Put more pressure on the spring and see what happens.

[DmaxMaverick]

If the smoke is white it would indicate unburnt fuel which would probably indicate the wastegate is opening to soon dumping your boost pressure. You really need that gauge to really find out what's going on. Put more pressure on the spring and see what happens.

White fuel smoke indicates cold combustion (or lack of complete combustion while cold). Black smoke indicates excess fuel during hot combustion. If the engine is up to operating temp and you get white smoke, you have serious timing (very retarded) or other issues.

[93GMCSierra]

My vacuum pump was making a lot of noise, so I replaced the turbo waste gate actuator with a manual one. I did not replace or remove the pump. I have noticed a significant decline in fuel economy, and I don't seem to hear the turbo spoil as I did before the pump started going bad. In addition to the manual actuator, is there something else that needs to be done to totally remove the vacuum system from the rest of the system?

For comparison, fuel economy was high teens (17 or 18), but latest fill up was under 15. Same driving. I know winter blend will cause a decline, but this seems extreme.

If your pump is still turning via the belt is it still making noise?
If its not then how was disconnecting it helping. You need a shorter belt, and or better option just remove the pump from the motor.

[stezloco]

if the vac pump was making a racket , why didnt you remove it to check that first? it could be coming apart inside ....
your fuel economy is bound to get worse if the turbo wastegate is now controlled by a spring...its closed all the time until max boost is achieved and it starts letting the gate open (still on full boost) you cant hear it spooling up because its already kept turning at a decent rate of knots.....doesnt have to spool from low turbine rpm's to operating speeds...
i had a thought when i first came to this site and was asking a few daft questions about my own 6.5 ...i never received a reply on this one but here goes....regarding your fuel economy...if youre looking for best fuel economy (whilst cruising and not really wanting massive grunt) can the vacuum at the wastegate actuator be totally 'dumped' via a switch activated solenoid or a simple valve in cab ? or is there a way of jumping the vac solenoid? this would have the effect of letting the exhaust gases push open and keep open the wastegate disc and not allow the turbo to receive full flow of gases to it , thereby keeping boost lower or not at all?, and the boost sensor wont see any manifold pressure and the injection pump wont be commanded to add extra fuel to suit that boost....that in theory should keep fuel use down??mpg's up..? any thoughts from the experienced here would be appreciated...i'm going to try it myself anyway...unless theres a simpler method ive not yet read about on this forum...i dream of high teens mpg, i'm only getting 14 at best .....it stinks....imperial gallons too. i'm in the U.K.I should be seeing low 20's SURELY....??
i'm already looking at other issues as well...timing is too advanced .....
i'd go back to the vacuum system and sell your 'turbomaster' with the price of diesel these days......unless of course you are ,as most of us are, being sucked down the road of GETTING MORE POWER from these engines...while the dollars are being sucked from your wallet....