What's harder on an engine, a dyno pull or 1/4 mile pass?
Is there to may variables like stick or trans break cars V a foot break car etc.

 

Here is what I can tell you. My Dyno pulls, from 2000 to 6000 RPM take just over 13 seconds. I’m at WOT for 2-3 seconds before I start the actual pull, to let the accelerator empty so that doesn’t impact my AF ratio. So let’s say 15 seconds.

But, I only see 6000 RPM once, where a car will see it 2-3 times, depending on the number of gears.

So my opinion is that a 1/4 mile is harder. Most of your runs will be a few seconds shorter than a Dyno pull, but you will have a higher RPM average than an engine Dyno pull.

Stick or auto? A stick is easier on the engine but harder on the driveline when you dump the clutch. The main issue with autos is that if your flex plate and torque converter clearance aren’t right, you will wipe out a thrust bearing in short order. How many check torque converter end play and clearance at the crank? How many check the tha actual flex if the flex plate?

just my two cents

jerry

 

Also, I bet the temperature of the engine is higher in the car and has a greater rise in temp than the dyno. More heat, while the adiabatic efficiency is higher, is worse for an engines life.

 

2 questions Jerry(or anyone else)

1. I wonder how much acceleration plays into the fluids sloshing around an engine. (or even hard parts)

2. How much torque against an engine does a dyno provide when making a pull? (vs. 3400-400lb weight of a car)

 

The acceleration in a car will cause all the fluids to go backwards. So greater chance to uncover oil sump. You also have a greater risk of uncovering the jets, mainly rear, and making the engine go lean. Super lean is fine, lose power and combustion temp drop. But there is a red zone, like 14:00-15.5:1 that is a danger zone where the engine knocks. The dyno doesn’t have this problem and I watch the oil pressure and A/F ratio during a pull and pull back if anything doesn’t look right.

i don’t know what you mean by question 2, if you explain it differently I’ll try to answer.

jerry

 

I think Peter's question is how does the dyno load compare / to a 3500lb to 4000lb making a pass? Would not the stick / transbrake car not shock load the crank more than a foot brake car?

 

Any automatic car has a torque converter. The torque converter is the worlds best abosorber/damper/etc. It reduces the impact, on either side of it, very, very well. I have about 20 years of OEM background in powertrain development (GM and Ford before starting my own business). The things we were asked to do with the torque converter, to mask issues, would leave most people speechless. So an automatic transmissions torque converter makes all things better and less stress, even if you have a transbrake.

I honestly don't know how to answer the load question, and it's probably the OEM background getting in the way but let think out loud here and maybe it will trigger something for me or someone else. We used the term load to essentially describe how much power/torque the engine is making versus it's potential at the RPM. GM used engine manifold pressure, in KPa, and Ford uses volumetric efficiency. So my brain is stuck refering back to this. The engine dyno and the car basically see 100% load in my mind, so they are the same. I'm not saying I'm right, I'm just saying my mind is relating it all back to OEM background. Certainly on the engine dyno you accelerate slower (in my dyno testing the engine is accelerated at 300 RPM/Sec, that's a "standard" in the industry for a power run) than in the car. So you have more time at lower RPM. When you accelerate faster I can assure you that the engine torque is lower. Engine power is used to accelerate the engine, so during the transient of acceleration the net torque produced at the crankshaft is less and the faster the acceleration the less net torque at the crank. But the engine still makes that power/torque, it's just using some to accelerate itself. So is the "load" different? Right now I'll say I don't think so.

Right now that's all I got.

jerry

 

A normal acceleration test on a dyno would happen quickly and not load an engine down and let exhaust temps climb. At times we ran step tests at 500 rpm steps from say 1500 all the way up to 6000. That will put a bit of heat into an engine so you have to watch your numbers.

 

Without naming a particular manufacturer, could you give an example?

 

It all centers around the torque converter clutch. When the clutch is locked there is no more isolation between the engine and the driveline, there are damper springs like a manual clutch disc, but those don't do very much. Someone wanted us to put logic in to NEVER have the engine run at 1200 RPM because of a serious NVH issue. They totally serious and even submitted a change request to the software people to make this happen. They wanted the converter and shift schedule to be manipulated, in real time, to prevent this.

jerry