GT350 Engine Mean Piston Speed (Estimated Predictions)

[Doc Holliday]

So let's just say hypothetically, you do a half-second money shift coming from 60-75 and slot it in second; revs spike, rear locks up for a sec, and the clutch gets pushed back in. Would that do any kind of measurable damage?

Hypothetically speaking... yeah...

So yes, ahem...hypothetically.... doing that can cause some serious engine damage. So lets just say for a minute, again hypothetically, that you did that in your 2015 GT PP. It could cause you to throw a rod, but if that had happened, you'd already know about it because that's instant catastrophic failure. You could also damage valves and/or pistons if you had contact between the two. Valve springs could break. Cam followers can pop out of place. There are other damages that can occur as well, but these would be the more common things. If this hypothetical situation were to occur, and you really wanted to reassure yourself, you could have compression and leak-down testing done on all the cylinders, and remove the cam covers for visual inspection of the valvetrain.

Now that said, doing said hypothetical mis-shift does not 100% guarantee that you will have engine damage. The quicker you recognize it and correct it, the less likely it is to do damage. I'll admit that I did something similar once on the strip with my GT500. Luckly, I realized what had happened almost immediately and quickly depressed the clutch. It ran fine then and has ever since. I didn't do any leak-down testing or compression testing. I consider myself lucky with that one.

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[FPCV8YO]

In regards to the longer rod idea.
My question would be does using a longer rod smooth out the moment of accel/decel of the piston as it changes direction at the top and bottom of the stroke? In effect reducing the maximum stresses experienced by the piston/rod combo.

Is there any way to quantify how much damage a missed shift would do? Like say 5th to 2nd instead of 5th to 4th? Would it matter if it's for a split second? This is my nightmare.

There's no rev limiter?

 

[OppoLock]

So yes, ahem...hypothetically.... doing that can cause some serious engine damage. So lets just say for a minute, again hypothetically, that you did that in your 2015 GT PP. It could cause you to throw a rod, but if that had happened, you'd already know about it because that's instant catastrophic failure. You could also damage valves and/or pistons if you had contact between the two. Valve springs could break. Cam followers can pop out of place. There are other damages that can occur as well, but these would be the more common things. If this hypothetical situation were to occur, and you really wanted to reassure yourself, you could have compression and leak-down testing done on all the cylinders, and remove the cam covers for visual inspection of the valvetrain.

Now that said, doing said hypothetical mis-shift does not 100% guarantee that you will have engine damage. The quicker you recognize it and correct it, the less likely it is to do damage. I'll admit that I did something similar once on the strip with my GT500. Luckly, I realized what had happened almost immediately and quickly depressed the clutch. It ran fine then and has ever since. I didn't do any leak-down testing or compression testing. I consider myself lucky with that one.

Okay, so if my hypothetical self would have done something like this in the past, but the car hasn't shown any sign of issue since then, I'd likely, hypothetically be okay? Because that's good to know for future reference. I totally don't make mistakes like that, but I was just curious...

 

[OppoLock]

There's no rev limiter?

The pucker factor was so strong that my left leg reflexively damn near punched a hole through the firewall, so I can't really say.

 

[Hack]

There's no rev limiter?

The rev limiter won't help you when you downshift into the wrong gear. It's a question of whether the rear tires have enough traction to turn the engine at whatever speed is required by the gearing. The momentum of the car can force the engine to spin at a fast rate with no ignition or fuel present.

 

[Hack]

I think that quote kind of points out a clash of understanding between an engineer and a technician. An engineer worries about rod/stoke ratio because it is part of the design of the engine. He/she does not worry about the connecting rod bolts being properly torqued because he/she assumes the technican can do his/her job.

I don't agree. I think the article is written from the standpoint of an engine designer.

I think you both make good points. Reher Morrison specializes in drag racing engines, the demands of which are very different than an endurance racing engine, like say NASCAR or F1, which will see long sustained periods of high RPM. The drag racing engine may actually see higher mean piston speeds, but for much shorter bursts. The drag racing engine is also able to take advantage of the some of the benefits of a shorter rod ratio for its intended purpose.

I do think that the rod ratio is not quite as critical as it once was with the quality of modern materials and machining tolerances. Engine components are able to more reliably withstand stresses today than they once were. This allows engines designs to 'get by' with lower rod ratios. However, I'm sure it's something that is still considered in the design.

I think Nascar has pretty strict rules that limit engine architecture, so I'm not sure whether that's a good example. F1 engines spin really high rpms so they really aren't living in the same world either.

 

[domingos35]

If you going 80mph in 6th and mis shift from 6th to 2nd or 3rd and don't correct it your engine is toast right? Glad I drove stick cars most of my life

 

[Falc'man]

V10 5.2 Lamborghini Huracan has 8250rpm and 92.8mm stroke. Should place it in 3rd spot? Or is that considered the same engine as Audi's?

Once multiplying the speed with the mass of the piston I imagine Voodoo could have the highest number. That there is the killer.

 

[Doc Holliday]

The Lamborghini and Audi 5.2L v10 share the same basic architecture, but the Audi has a higher redline, so I only listed it once, in its highest-revving form.

And yes, I would imagine the voodoo piston is probably heavier than any of those engines on the list with a higher MPS, simply because the voodoo bore is bigger.


On the subject of Formula 1 and NASCAR engines:

In the 2.4L V8's that Formula 1 used to run, the reported MPS at redline is approximately 26.5 m/s or 86.942 fps. I haven't found the same data for the new V6 turbo engines.

In NASCAR, the reported MPS at redline is around 27.5 m/s or 89.239 fps. This applies to seasons prior to 2015. In compliance with their mission to slowly neuter the series (a mission that is nearly complete), NASCAR has implemented some new rules for 2015 to decrease horsepower and engine rpm.

 

[DivineStrike]

Okay, so if my hypothetical self would have done something like this in the past, but the car hasn't shown any sign of issue since then, I'd likely, hypothetically be okay? Because that's good to know for future reference. I totally don't make mistakes like that, but I was just curious...

The pucker factor was so strong that my left leg reflexively damn near punched a hole through the firewall, so I can't really say.

The rev limiter won't help you when you downshift into the wrong gear. It's a question of whether the rear tires have enough traction to turn the engine at whatever speed is required by the gearing. The momentum of the car can force the engine to spin at a fast rate with no ignition or fuel present.

on a semi-related note. If this were to per-say happen on the 2015 motor or boss engine. I think the valve-springs could easily handle an over-rev of 7500 to just under 8k rpms.

Now the question is, what is the computer doing to react to an over-rev? is it throwing any fuel in, or is it an empty cylinder when the spark happens? If its throwing any in at all I think that'd be a recipe for disaster. Now if there is no fuel and it's just a "dead" spark; could it be said, that as long as the engine components are being lubricated properly and the valves can handle the rpms, the engine would essentially be fine?

If this is the case, (I don't really know, so if someone could go into a little more detail on how it would work...that'd be great) Engine reliability after an over-rev would heavily rely on how the ECU is tuned, whether it is cutting fuel after exceeding an RPM, and if the valvetrain can handle the energy.

Again this is just a guess as my understanding of tuning and the specific inner workings of the engine is limited.

Again someone please elaborate more

That said, what rpms are our oil pumps good for?

 

[Sered]

There's no rev limiter?

As others addressed, it's a gearing thing; it'll hit the limiter and cut fuel/spark, but the motor will still be revving that high :/ As Doc Holiday put it, the best way to save it is to realize its going on and get out of it ASAP. Besides, if you're going to be downshifting into 4th gear and have it damage something potentially by going into 2nd, you'll most likely need to be going over 70mph. If the gearing is anything like the M3, 4th will top out around 150mph.

I don't agree. I think the article is written from the standpoint of an engine designer.

We'll have to agree to disagree. I feel he's a builder as there's no keywords in there for me that show he thinks from a systems-level perspective. Nothing wrong with what he does; its an extremely skilled position that most of us would never be able to do and he's probably got enough knowledge in that head to fill more than just a book or two. I'd get into it more, but I don't think anyone wants to read a post about semantics :lol:

If you going 80mph in 6th and mis shift from 6th to 2nd or 3rd and don't correct it your engine is toast right? Glad I drove stick cars most of my life

Depends on the car. I'd bet in a GT350 you'd be fine misshifting into 3rd from 6th at 80mph; possibly even into 2nd depending on how they gear it.
Here's the M3 gearing for comparison, I really hope Ford picks a slightly different gear ratio for 1st as the RPM drop off from 1st to 2nd is ridiculous:

BMW M3 6-speed
Gear / Ratio / Max Speed / RPM drop on upshift
1st 4.055 44
2nd 2.396 75 4900
3rd 1.582 113 5600
4th 1.192 150 6300
5th 1.000 179 7000
6th 0.872 205 7300
Final Ratio 3.678
Redline 8400

 

[FPCV8YO]

The rev limiter won't help you when you downshift into the wrong gear. It's a question of whether the rear tires have enough traction to turn the engine at whatever speed is required by the gearing. The momentum of the car can force the engine to spin at a fast rate with no ignition or fuel present.

Aren't most shifters dual gate in order to prevent or at least limit this from happening?

 

[Sered]

Aren't most shifters dual gate in order to prevent or at least limit this from happening?

Dunno. I know my M3's transmission isn't. But BMW didn't exactly spend much time on this transmission (it's the same 6MT shared across quite a few different cars).

 

[JWS]

NASCAR was running 9.000 to 10.000 RPM the last few years, at some tracks. It seems that most of the failures were due to breaking Valve Springs, at least where the engine RPM varied little.

Other failures seemed to come from Belts Flying off, but that was mostly after hitting debris.

 

[Strokerswild]

NASCAR was running 9.000 to 10.000 RPM the last few years, at some tracks. It seems that most of the failures were due to breaking Valve Springs, at least where the engine RPM varied little.

HUGE difference in valvetrain dynamics between a pushrod setup and an OHC one.....

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