Mystery switch or lockup controller?

[KWilkinson]

Well we just had a little dyno day in Arizona yesterday, and a lot of us Auto trucks were having problems getting a good low RPM pull in 3rd gear, had to stomp on it from about 2000 RPM. Would a mystery switch or lockup controller allow a pull from say, 1500RPM or even lower, without downshifting? Any thoughts? I'd like to know how some of you guys with auto trucks are running on the dyno.



Some of our trucks didnt see the torque numbers that we were expecting. Mine for instance, and the truck just before me which is pretty much the same mods, put down around 450 horsepower (which seems right) but only 770-780 ft. lbs. It might have been due to a high rpm launch on a unloaded dyno, and not building boost low enough to get the torque. I think only one or two auto trucks that were also modded the same got around 900-950 ft. lbs. which sounds right. One of them I know had a built DTT trans, but no lockup controller, just the enhancer. Maybe just the way he did it? Maybe the enhancer kept the converter locked at a lower rpm to build boost? Im pretty sure on a few of his runs it kicked out of lockup, maybe even hit 2nd gear... but not positive. I know they tried loading the dyno by bumping the brake but his truck grabbed a gear and looked like it was gonna jump off the dyno...



And by the way, we all ran our own trucks on the dyno. First event I had been to that someone there didnt run it. It was a fun day :-laf

 

[cerberusiam]

I am assuming this was a Dyno jet apparatus. If it was a mustang then you have another problem.



Your short on the TQ because you were running in drive and not OD. You need to load the motor as much as possible in OD to get the full TQ readings across the rpm range. Even a with a brake most of the DynoJets can't load the motor enough to get full readings.



Forget the 1500 rpm runs, unless you run a TNT R tune or Crazy Larry, these engines derate starting at 1800 rpms and at 1500 they are 50% or more derated. The auto trucks are made to run and pull above 1800 rpm's so use that as a baseline.



Yes, the lockup switch will make a big difference in your runs. It allows you to lock it into OD with no downshifts and get a good map. I run the truck up until it is locked in OD then start applying brake and throttle to get some boost into the motor, remeber these things severally derate fueling under 12 psi. Once I have about 15 psi built I give the operater the nod to start the data collection and floor it.



Smarty #7 with moderate TQ management it runs ~ 450 HP 900 TQ with rpm's running from 1800 to 3200.

 

[KWilkinson]

Well that does make sense, but I was always under the impression that you wanted to make your pull in direct drive (which would be 3rd lockup).

 

[cerberusiam]

Well that does make sense, but I was always under the impression that you wanted to make your pull in direct drive (which would be 3rd lockup).

Theoretically, you should see the same numbers in drive as OD. Functionally, a typical dynojet is tuned for gas motors and HP and not for diesels and their TQ band. Its the dyno's inability to load the engine to produce the power thats the problem.

 

[KWilkinson]

Well I'll give it a shot next time I dyno on April 12th. Was just going to go up and watch, but I'll dyno to try this out. Thanks for the help

 

[bluthndr]

Dunbar told me that trucks usually dyno better in OD because it loads the turbo better. Makes sense - I think the rollers are a little over 4000 lbs, and most trucks are almost 7K. Dynojets (most) just measure how long it takes for you to accelerate that known mass (drum) to figure out your hp. Since our trucks are designed to accelerate more weight than the dyno rollers, it doesn't work well. I think you would find the most powerful trucks (modified sled pullers) would dyno poorly, as they are designed to accelerate a 20,000lb + mass.