Which is worse: Max load constant RPMs or Max load Varying RPMs
 

So I've once again found myself in the comments of an Instagram post arguing with strangers who mostly have no idea what they're talking about, but some people with experience have chimed in supporting both sides of the argument. The video (which I will later link, it is on my phone, and I'm on PC) shows a turbocharged Mustang on the dyno. It reportedly makes 1100+ WHP. The person who posted the video claims that the dyno operator almost blew the engine up due to "10,000 lbs of resistance" in a pull that lasted less than 40 seconds. The pull begins down low, turbo spools up, and RPMs increase until eventually the RPMs stop increasing, not due to the redline of the engine but due to the torque falling off and the very high resistance of the dyno. Everyone in the comments immediately started bashing the tuner for almost destroying the engine during this 35-40 second pull on the dyno. While the tuner did make the mistake of applying too much resistance, I do not believe that the engine should be catastrophically damaged by this. I understand that it is bad for the lifespan of the engine in regards to piston walls, piston skirts, and piston rings, but not any worse than 35-40 seconds of full throttle at or above the same RPM it stalled out at. I simply do not understand how this could potentially cause immediate catastrophic damage (assuming that the engine is built well enough for these power levels). Hell, race engines are built with the expectations of 10-100 hours of track time, which is arguably way worse than this 35-40 second pull. The only exception I can think of is drag cars that have been pushed far enough to need aluminum rods, but those are usually on exotic fuels and/or making way more power than 200hp/liter or 125hp/piston.

Some points people have been making against my argument are:

• This can cook the main and rod bearings. I don't see how this load would be any worse than a normal 35 to 40 seconds of full throttle with varying RPMs. As long as oil flow is adequate and the bearings never contact the crank, I don't believe those parts would even be able to tell a difference.
• This can cause hotspots on the head. Again, I don't see how this is any more likely than a normal 35 to 40 seconds of full throttle with varying RPMs. As long as AFRs, ignition timing, and therefore EGTs are safe I don't see how this could cause issues.
• The OP himself said "no vehicle is designed to hold wot at over 100 percent load for that long , it will destroy it self", which is goofy. He doesn't elaborate as to why, which is what I've been asking for. Plus his statement is just false, plenty of cars put out more power per liter and get abused much more than this 35-40 second pull. The OP also says that a car traveling at its maximum speed for an extended duration due to drag isn't the same as what was going on in the video, which is just false other than airflow through the intercooler and radiator but in such a short period it again shouldn't matter assuming the car is safely tuned and not extremely heat soaked.
• Some idiots are even saying the top end could have easily been damaged. Mayyyyyybe the exhaust valves, but again if the AFRs and EGTs were safe it shouldn't matter. Every other top-end part shouldn't even be stressed considering it wasn't at its intended redline.
• This is going to induce knock. Well, it might get a little hot and be more knock-prone, but again, if the tune is safe then knock shouldn't occur.
• The same guy who said this would induce knock also said it could bend rods or ruin bearings, but AGAIN, how would this be any different than a normal full-throttle pull?

Also, the OP claims the video is 7 years old and the car still runs, further proving my argument that things are fine. The only way this is bad for the engine in my opinion is the piston wall/rings/skirts like I mentioned before, but I simply fail to see how even this would be any worse than a normal 35-40 seconds at full throttle at or above the RPMs shown in this video.

So I come to you all. Not sure where else to ask, but I know this site is filled with very well-educated and experienced people. Am I wrong in saying that this full-throttle pull that lasted 35-40 seconds before reaching a point where the engine could not produce enough torque to overcome the dyno's resistance is no worse than a consecutive 35-40 seconds of full throttle with varying RPMs? All I see is a good endurance test that proves the engine can withstand what is to be thrown at it in the future. If it blew up on the dyno, it would've blown up later is my argument.

On a side note, I really need to stop wasting my time with these keyboard warriors online who have very strong opinions without any logic behind them. I'm not looking to be proven right or wrong, I want to learn. That is one of my favorite things about engines and tuning, there is always more to learn, but very little to learn in the comments of an Instagram post haha.

I run the hydroplane at about 7500rpm and never lift my foot for about 10 minutes straight. (while the prop comes out of the water and it shoots to 8500 and back) Granted it's a SBC and not boosted. But the GP boys do the same thing with blown big blocks on methanol. If you want to durability test an engine, stick it in a hydroplane.
I've had my bike at WOT for about 3 minutes straight and it was fine. I've done pulls in the Miata that feel like they have lasted 40 seconds.

OEMs torture test their engines for hundreds of hours at WOT max load with basically no wear. A lot of aftermarket engine builders will torture test engines before they ship them too.

If your engine can't handle WOT for 45 seconds, it's a piece of junk.

That’s my logic, meanwhile there’s a profession tuner that works with 1000hp AWD Civics out here telling me I’m wrong in the comments. Conveniently he refuses to elaborate as to why, just doubling down that I’m wrong lol. As a person who always wants to know “why?” a simple yes or no does nothing for me at best. At worst it makes me think worse of you. Can press buttons and get the AFRs and timing where they need to be, but you can’t explain anything, classic haha

https://cimg5.ibsrv.net/gimg/www.mia...1c1280bb6f.jpg

Most Instagram (internet?) comments seem to fall somewhere near the top of the peak on the left.
I can't even look at most Instagram comments regarding car videos. Not that I'm a spectacular car guru myself, but its amazing how some people can be so sure of themselves after just barely grasping the basics of a concept.

Yeah step one is delete your Instagram account. But I’ll put in my two cents. Dyno has shit for airflow. Plenty of cars will over heat on the dyno that wouldn’t on the street. I’ll tune with the eddy current (sp?) to slow a high hp pull down to see what it’s doing. I’ll also do it to hold an RPM at any load and tune the entire column at once. We don’t have the best dyno fan, but even in the 40-50 degree weather we’ve had lately will cause cars to overheat.

Replying for the updates.


Edit: Seems no update.

In general, both scenarios have their drawbacks, and neither is ideal for the long-term health of an engine. However, if I had to choose, constant high load at maximum RPMs is typically considered more detrimental due to the sustained stress it imposes on the engine's components. Varying RPMs under maximum load, while still challenging for the engine, might distribute stress more evenly and allow for brief periods of relief for certain components.