1.65 mm timing gets 16.5 MPG

[btoscano]

That's interesting because I drove by 9 states on the way home and they are say 5 MPH off with the stock tires... but the trip meter/odometer is SPOT ON!! Go figure! Is your odometer right on the money?

 

[91W350]

I put on taller tires on my 91 to make the speedometer right, but the odometer was right on before. Now the odometer runs a little behind times. Glen

 

[btoscano]

How much does turning up the fuel screw hurt fuel economy?



I had the diesel shop set the pump on the high end of the specs and maybe they a little above that for good measure. At 1. 65 mm timing I don't get any turbo lag & no visible tail pipe smoke. But this is with stock injectors. I am almost thinking of turning down the timing some, say 1. 45 or 1. 55 and see how the truck runs? Maybe I'm a little advanced on the curve for this particular injector-pump setup?

 

[btoscano]

I am going to get some gauges for my fine tuning. What kind of turbo boost numbers should I see for best fuel economy? Keep in mind my injectors are stock.



Thanks,

 

[TKingsbury]

I have my fuel screw and smoke screw in 1/2 turn. My economy hasn't changed. I still get 18 unless I romp it too much, or tow. I see about 6-10 psi on the freeway @ 65-70 mph depending on wind, grade, etc. Keep in mind that I have a 14cm housing on my turbo, with my 21 it was more like 2-4 psi.

Travis. .

 

[btoscano]

I hadn't thought of the turbo housing changing boost levels.



I just took the truck out for a drive. At 80 MPH indicated (75 actual) I am running about 4-5 psi on flat ground or 8-10 psi on hills. If I slow down to 75 MPH indicated (70 actual) those numbers drop 1-2 psi.



The max boost I was able to get was 17 psi with the foot to the floor climbing a grade in 5th gear around 90 MPH indicated (85 actual). 90-92 MPH is the top speed of the truck going uphill.



I was running empty.



Should I be making adjustments?



Brian

 

[btoscano]

I took it out for another run. I drove around 55-65 MPH and my temporary boost gauge was reading on the lowest tick mark (2-3?) on flat ground and about 4-6 on hills. Running 55-65 takes almost no throttle. It was interesting that if I was climing a hill at 65 and 5th and shifted to 4th, the boost didn't change except for a blip while I shifted.



Anyone care to comment? I am curious if I should be changing the timing based on this information.



Thanks,

 

[Mundgyver]

What was your EGT's doing during this time???

 

[btoscano]

Don't have an EGT gauge yet so no numbers there. I have tried to keep the truck stock to cut down on costs The pump is supposedly set to the highest fuel delivery within 10% of factory specs by the local diesel shop. When I installed it I set the timing to 1. 65 to split the difference between the forum members that said 1. 6 and 1. 7.

 

[btoscano]

Hey all,



For experimentation, I retarded the pump timing a little & I was able to get 15-19 psi easily on the freeway. High boost is reached much faster. I not see tailpipe smoke either. This afternoon I cranked up the timing back up near what it was before and it gets to 15 psi and 16 if I stand on the go-pedal in 5th up towards 90 indicated.



Which is "more desirable" in terms of balance of power and fuel economy and predicated EGT's (don't have a gauage yet)?



Thanks,