blueberry

Hey all,

I have a stock 1993 truck and I have been adjusting the pump timing in hopes of ideal fuel economy/power. When I started, the pump timing was 1.65 mm of lift and I was getting 16.5 MPG on the freeway at 80 MPH (75 MPH actual). Max boost was around 16-17 psi and to get there I'd have to stand on the go-pedal and go about 90 MPH. I've since reduced the timing to 1.4 mm and now I'm getting 17 MPG on the freeway at 80 MPH (75 MPH actual). Max boost is now around 18-19 psi and it builds boost faster. However, pulling up grades, etc. boost values are about the same with either timing. For example, 10-11 psi pulling a 5-6% grade at 80 MPH. I don't notice smoke in either case.

So I guess 1.65 mm is "too far" for this stock setup.

I am wondering if I should try 1.3 mm or 1.5 mm next in hopes of a bit more fine tuning. What do you all think?

Thanks,
Brian

bgilbert

I think you should try about 28*, little bit of ether to start and give it that pullin tractor idle

kennedy

you say stuff like that and people may actually start beleiving you... after all, you are probably one of the upper guru's on here when it comes to these trucks...

bgilbert

Yeah I'm only kidding. I'm just giving Brian a hard time .

Upper guru, though, nah. Just someone that doesn't need the truck as a work or towing truck and could afford to dig deep into it.. er something like that.

BC847

I was recently goofing around with my mess and decided to check the timing by the book. I found it at 2.1mm

I thought it had been running kinda stiff.

I backed it down to 1.75mm. Much better.

charger 69

Since I tow about 12K would advancing the pump be safe or would it run hot?

BC847

FWIW ~

Generally speaking with regards to the first gens, increasing the IP timing will result in trading a little low rpm torque for a little more HP in the upper rpms.

You're pretty much injecting the fuel a little earlier, allowing the heat of combustion a little more time to expand the air. That additional heat converted to work at the crankshaft will present as slightly lower EGTs that will present further as a small drop in boost because less heat's available there.
Keep in mind, you're injecting the fuel closer to TDC so your peak combustion pressures will be much higher. There's generally a little room to work with comfortably, but be well aware the bell rings with a blown head gasket.

While the 1/8th inch bump appears to fit most of our trucks well, you'll find the OEM timing changed toward the end of the 1st gen era due to smog regulations. So assuming one base timing figure fits all would be in error.


I hope this helps.

blueberry

Thanks!

The confusing part for me was that most suggested 1.6-1.7 mm timing but I knew my truck could be better. Setting it at 1.4 mm make a nice improvement. I am thinking about trying for more. My last two tanks averaged 17.3 MPG for 900 miles of freeway driving at 80 (75 actual).

Before I work more on the timing I have some U-joints and brake parts to change.

charger 69

In the search that I did the head gasket was mentioned a few times as being at risk so with the power screw turned up and 16cm housing soon I am concerned about advancing the pump.

flashgordon

BC847 thanks for the chart,lots af good info! Going to have to add this one to my file......If you don't mined!
FWIW ~


Code:
Engine parameter: TIMING is:
RETARDED ( - ) ADVANCED ( + )
EXHAUST TEMP increases decreases
CYLINDER PRESSURE decreases increases
INTAKE MANIFOLD PRESSURE
(BELOW P-TORQUE) WASTEGATED increases decreases
BSFC (brake specific fuel consumption) increases decreases
NOX (oxides of nitrogen) decreases increases
HEAT REJECTION increases decreases
HYDROCARBONS (HC) increases decreases
BLACK SMOKE: 1000RPM increases decreases
BLACK SMOKE: PEAK TORQUE decreases increases
BLACK SMOKE: RATED increases decreases
WHITE SMOKE: < 1000RPM increases decreases
WHITE SMOKE: > 1000RPM increases decreases

BC847

I stole it from here ~

http://dodgeram.org/support_pgs/diesel_ix.htm

See: Engine Timing.