torque low is it the dyno or the truck

Torque numbers can be manipulated a lot it seems. I made 337/772 on dunbars dyno with the stock turbo. The run didnt start until 1900rpm or so, and i dont think the turbo was spooled till about 2000rpm, so I think I could have had a much better torque number has he started the run around 1400rpm and had it spooled and pulling hard at 1600rpm.

My buddy just dyno'd his 6.7 cummins(i posted a video). He only made around 900ft lbs the first couple runs. Then he started building a bunch of boost down low and letting go of the brake and going WOT. He pulled his torque up to about 1200ft lbs. Almost 300ft lbs more than just rolling into it.

I think the best measure of how a truck runs is on the pulling track or the drag strip. There are a lot of variables there too though.

Eric
 
i dont know if i would call it manipulation of dyno,as stated a turbo diesel doesnt make power til it spools up,builds boost, by braking to build boost you get the engine to build power sooner so the engine is making the extra torque because its spooled up. lower timing puts more heat out the exaust helping spool quiker also, the ve pump advances timing with rpm so it helps spool quiker.
 
:doh:

I was marinating on this and realized I have a flaw with my numbers. The RPM derived is crap.

I'm surprised nobody mentioned it, if that was the case. Serves me right for trying to use math to explain something. Stupid math with physics. :rules:

Ya'll give me a hand here...

The peak numbers stated almost certainly did not occur at the same Engine RPM. I plugged best numbers in from two measurements (force and work or work rate) and used them to solve for RPM (time). The problem is those values didn't occur at the same time. Time is constant. I don't have a Delorian, I can't change time.

As far as I can tell, here's where I stand:
Math is overjoyed.
Physics is pissed.
The value in time (RPM) calculated means nothing to either force or work curves.

My statements about the variables in post 17 with respect to load, turbos affect on work force at varying rpm, and the measurements of force and work are fairly accurate.

The math is right, but the RPM I derived does not apply to either curve on any dyno sheet. :doh: Chit.



Here's what I 'know':
You can solve for torque if you know engine RPM with HP. The torque you derive, will be at the point in time(RPM) for that HP reading.
HP=TQ at 5252RPM
Those are widely used and obtain information of value.

I used a calculator, but there is a widget on the internet to do it for you with the two variables. I found this as I researched this dilemma. It derives the same number I did, but gives no disclaimer with regard to input values occurring at the same time. They cannot since that is the answer they are providing.

See here: http://www.wallaceracing.com/HP-TQ-RPM%20Calc.php

What is it called when math works, but physics is angry? Better yet, what is the value of that RPM or its definition, if any?

Sunnofa*****. I am an idiot. :blahblah1:
 
This is more observation than math/physics, but the peak torque is related to peak boost. Bigger slower spooling turbos typically make less torque than a smaller quicker spooling turbo. Peak horsepower is indicative on how well your setup can handle the heat and pressures of full boost. If the turbine/ wastegate chokes then torque drops quickly through the rpms and the hp number will suffer.

So if you have a stock turbo that makes good torque at a low rpm, you will feel the boost increase power quickly then drop off with rpms. Then you switch to a big single. The slower spool means that there actually less torque thus lower hp through the lower rpms, but at full boost the bigger turbine can process more air so the torque takes longer to drop off. This results in a higher hp number overall by shifting the torque curve to the right.
 
Ph4tty said:
This is more observation than math/physics, but the peak torque is related to peak boost. Bigger slower spooling turbos typically make less torque than a smaller quicker spooling turbo. Peak horsepower is indicative on how well your setup can handle the heat and pressures of full boost. If the turbine/ wastegate chokes then torque drops quickly through the rpms and the hp number will suffer.

So if you have a stock turbo that makes good torque at a low rpm, you will feel the boost increase power quickly then drop off with rpms. Then you switch to a big single. The slower spool means that there actually less torque thus lower hp through the lower rpms, but at full boost the bigger turbine can process more air so the torque takes longer to drop off. This results in a higher hp number overall by shifting the torque curve to the right.
Click to expand...


I like that way of thinking.
 
You must log in or register to reply here.
Back
Top