Lowest tachometer "red line" indicator you've seen

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Originally Posted By: Nick R
Originally Posted By: Scott_Tucker
The longer the stroke, the lower the redline.


Not necessarily true. My cruze has a relatively long stroke not to mention very small displacement (1.4L and undersquare) but redline is still 6,500RPM.


Your Cruze has a stroke of 3.47" (correct me if I'm wrong) which equates to a piston speed of 3759 fpm at 6500 rpm - hardy anything spectacular (not bad, but not spectacular). The fact that it is undersquare and 1.4 liter has nothing to do with piston speed or your redline.

To those who say redline has nothing to do with stroke length or piston speed, you are wrong. The longer the stroke, the higher the piston speed. The higher the piston speed, the more G forces the reciprocating mass is subject to and the more likely it is to fail.

Originally Posted By: Brenden
Originally Posted By: Scott_Tucker
The longer the stroke, the lower the redline.

Lol, not true...

The lowest I have seen is around 3k in a 24v 5.9 cummins, it was a long time ago I drove it so I'm not sure the exact #.


The 5.9 Cummins had a 4.72" stroke which equates to a piston speed of 2360 fpm at 3000 rpm. Certainly not a very high piston speed and the engine would be capable of more if the rest of the engine was designed for it.

Large diesel engines are built for torque and therefore have extremely long strokes. If you look at the strokes on the engines that people are quoting as having even lower redlines you will see that they have very long strokes. The engines in large ships that have redlines of 200 rpm have extremely long strokes. The same principal applies.

A Formula 1 engine can spin safely to 18,000 rpm. It can do this because it only has a 1.7" stroke. Engine designers have known for years that the maximum rpm an engine can turn us limited by piston speed and the strength of the reciprocating components. It's not rocket science.
 
It's definitely true that piston speed and stroke have a direct relationship. The longer the stroke, the higher the piston speed at a given engine speed. This is necessarily the case because the piston in a longer-stroke engine has to travel a greater distance than the piston in a shorter-stroke engine in the same period of time.

The 1.4L in the Cruze actually has a relatively short stroke. The 1.8L engine has a stroke of 3.47", but the 1.4L engine has a stroke of only 3.3", or 82.6mm. At 6,500 rpm, a piston in that 1.4L is only traveling at a speed of 3,522 ft/min. That's not very high, in either engine.

Piston speeds of 5,000 ft/min seem to be as high as it generally gets, at least for mass-produced street engines.
 
Originally Posted By: Hokiefyd
It's definitely true that piston speed and stroke have a direct relationship. The longer the stroke, the higher the piston speed at a given engine speed. This is necessarily the case because the piston in a longer-stroke engine has to travel a greater distance than the piston in a shorter-stroke engine in the same period of time.

The 1.4L in the Cruze actually has a relatively short stroke. The 1.8L engine has a stroke of 3.47", but the 1.4L engine has a stroke of only 3.3", or 82.6mm. At 6,500 rpm, a piston in that 1.4L is only traveling at a speed of 3,522 ft/min. That's not very high, in either engine.

Piston speeds of 5,000 ft/min seem to be as high as it generally gets, at least for mass-produced street engines.


Well I meant long in relation to bore-stroke. The cruze 1.4 is actually undersquare, which I think was probably done to help with low end torque, which his the whole point of this engine.
 
Originally Posted By: Nick R
Well I meant long in relation to bore-stroke. The cruze 1.4 is actually undersquare, which I think was probably done to help with low end torque, which his the whole point of this engine.


Yes, it is under-square. And yes, strokes longer than bores do tend to maximize lower-end torque vs. higher-end power. It's not a long stroke in the absolute sense (which IS what piston speed and resulting redline correlate to), but it does have a stroke that is longer than its bore is wide.

You could spin that engine to over 9,000 rpm, and it'd still have a maximum piston speed of under 5,000 ft/min. The piston speed of a K24 at 7,000 rpm is 4,550 ft/min. You could spin the 1.4L to almost 8,500 rpm and have the same piston speed.

Cool!
 
Exactly, long stroke engines are built to be biased towards torque. Short stroke engines are built to be biased towards horsepower. The Cruze's engine uses a long stroke in combination with turbocharging to produce a torquey engine out of a small displacement. I really think this is the future of cars. Just look at what BMW is doing. They have replaced their awesome naturally aspirated I6 with a 2.0l turbocharged 4 and have more power and better acceleration combined with better fuel mileage.

The K24 engine has one of the highest piston speeds of any stock engine out there. I think this is because of advances in materials technology. Thank you Honda.
 
Originally Posted By: Scott_Tucker
Exactly, long stroke engines are built to be biased towards torque. Short stroke engines are built to be biased towards horsepower. The Cruze's engine uses a long stroke in combination with turbocharging to produce a torquey engine out of a small displacement. I really think this is the future of cars. Just look at what BMW is doing. They have replaced their awesome naturally aspirated I6 with a 2.0l turbocharged 4 and have more power and better acceleration combined with better fuel mileage.

The K24 engine has one of the highest piston speeds of any stock engine out there. I think this is because of advances in materials technology. Thank you Honda.

I think the F20C in the 2000-2003 Honda S2000 has the highest piston speed of any production car at 4960 ft/m at 9000 RPM. The F22C in the 2004-2008 S2000 has longer stroke but redline had been reduced to 8000 so the piston speed was only 4760 ft/m.
 
Max rpm for my tractor is 2800rpm, 2.0L 4 cyl. diesel, normally I run it at 2000. My Dads 5.4L F150 doesn't have a redline on the tach but I think the tach only goes to 5000, and you really have to use a lot of pedal to get much above 3000 rpm.
Highest rpms in a car I've been in is around 9k in the 160hp 1.6L Civic. The vtack was pretty neat in that car.
 
Diesels don't really have a red line, the governor kicks in at it's max revs. I used to drive an old Leyland Super Comet that had the governor set at 1,500rpm - that was really annoying because I had driven trucks with the same engine (and same cab, Albion and Dodge) and knew they went to about 2,500rpm. It was only a 5 speed box and no 2 speed diff, so it was short shifting to the extreme. Diesels don't often get over 4,500rpm because of combustion issues, so modern high speed diesels don't really hit a governor, they just run out of breath over 4,500rpm.
 
Late 80s and early 90s 350 and 454 equipped GMC trucks had a redline at 4,000 RPM with a yellow zone between 3600 and 4000 RPM.

There are a few things to keep in mind:
1. Engines with smaller displacement of individual cylinders usually rev higher than engines of larger displacement.
2. Some engines can rev past the redline without danger, however, small ports and small cams mean that it is pointless to rev higher.
3. Diesels usually have a lower redline than gas engines.
 
Originally Posted By: SLCraig
I think I remember seeing 4500 on a Fox Body Mustang. (302)


That was the "yellow" line. Redline on the tach was just short of 6000....about 5750-ish.

4500 would have been an appropriate redline. The CFI H.O. 5.0 in 1985 made 180 peak horsepower at 4200 rpm. There was nothing useable above 5000 rpm. Unfortunately, the AOD did not upshift until 5500 rpm.

My LX 5.0 was much quicker when I would lift off the pedal at about 4750-5000 rpm and then slam it back down when it upshifted keeping the revs out of the 5000-5500 rpm "no-power" zone. Kept those carbureted 305 Camaro-birds behind me.
 
Originally Posted By: Scott_Tucker
Your Cruze has a stroke of 3.47" (correct me if I'm wrong) which equates to a piston speed of 3759 fpm at 6500 rpm - hardy anything spectacular (not bad, but not spectacular). The fact that it is undersquare and 1.4 liter has nothing to do with piston speed or your redline.

To those who say redline has nothing to do with stroke length or piston speed, you are wrong. The longer the stroke, the higher the piston speed. The higher the piston speed, the more G forces the reciprocating mass is subject to and the more likely it is to fail.


An overly simplistic viewpoint.

2013 GT500 - 4.165" stroke, 7000 rpm - 4859 fpm

We just installed a n/a 4.6 4V in a 2003 Mach 1, it made 550 HP on Roush's dyno. The engine made peak HP at 7700 but basically holds on to the power to over 8500 rpm. The "everyday" redline on this engine is 8500 rpm, but it will and has withstood 9500 rpm.

The engine retains the 4.6's stock stroke, which puts piston speeds at 5018 fpm.

The Boss 302 engine has seen and proven reliable at 8400 rpm, this is with a 3.649" stroke and piston speeds of 5109 fpm. This isn't even a drag race engine, but a Grand Am cup road racer that typically lasts a full season.

Al Papitto spun a stock stroke 5.4 to 8500 rpm for years while retaining a steel connecting rod, without failure for something like 3-4 years.

4.165" stroke - 8500 rpm - 5900 fpm

I know of some Honda drag engines that see piston speeds close to 6500 fpm.
 
Bentley Arnage, somewhere a bit over 4k, but its rude to hustle such a car.

Most big diesels are done at 2k though.

In a lot of the big pre war cars like the Hispano's and WO Bentley's 3k is the end of the world.
 
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Here are a couple I've seen recently

img3366kq.jpg


mackq.jpg
 
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