Engine Gurus, what's your theory?

[ashyers]

Morning Crew,
Here's something to ponder that's been bugging me. I have my own theory, but I'm not going to sway the discussion yet. Truck is stock w/ 4:89's.

On my daily commute I climb a hill that's over a mile long at WOT. I keep myself occupied by watching the speed I crest the hill at very carefully. It's the daily dyno pull.

* If I approach the hill at an indicated 46mph (55mph w/ the 4:89's in the truck) I crest it at an indicated 38mph.

* If I wind up the truck and approach the hill at an indicated 52mph I crest the hill at an indicated 33mph.

Essentially I've found that getting a running start does me no good. I'm better off maintaining my usual cruising speed for as long as possible until I'm at WOT and then just hanging out there until I hit the top.

Thoughts?

Andy

[NAM VET]

I don't know where your engine puts out it maximum torque, but perhaps with your gearing and engine, your motor is at max torque at the lower speed.

NAM VET, back from a nice day at the beach here in SC.

[HingsingM37]

Andy,

After logging over 12K miles in my stock engine/gearing truck on hills and grades back in Ohio and here in NC, I have found that my rig to be most temperamental depending on conditions and I usually end up shifting down into third and enjoying the scenery or playing wait for the governor to kick out until I reach the top. I often yell out to the cars behind me "You won't like my other speed either!" LOL. I am going to have that made into a sign for my tailgate.

These trucks are limited at high end to begin with (the whopping +/-78HP and the stock 5:83's) so 4:89's are going to take away from power to climb at top end with the 230 gas engine. As for your question to the running start difference I assume you are at full throttle at the hill, so given the relation of RPM, torque and velocity your observation makes sense. Gearing is like race engine building, is your power going to be off the line, at top end, or mid way? Take comfort in knowing our rigs will take us anywhere, just not fast. Participating in the hobby and answering questions about your truck from folks make driving a slow relic most enjoyable

David

[Cal_Gary]

I deal with 10% grades here in Utah so using 3d gear is out-2nd chugs along slow and steady. Once I spring for the Pertronix kit and do a complete tune-up should help.
Gary

[jim lee]

At some point on the hill your faster run-up truck is going to be going the same speed as the slower run-up truck.

Hmm..

What you are not telling us is how long each truck takes to crest the hill.

-jim lee

[52PLOWERWAGON]

my theory is you need a high performance camshaft

[RMS]

Im thinking it comes down to throttle position. I imagine if you ran a AF mixture gauge you would notice it getting very rich under load @ wot.

this can easily be observed on a steep hill: load her up @ wot till she starts to lug and slowly take your foot out and watch the rpm's climb.

I also think the ball and ball can be sluggish changing between circuits with minimal vacuum change as after coasting down a hill I sometimes have to give it a bit of choke to get beck to the high speed circuit.