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SmartieParts

451 redline... someone with a tach please answer.

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This is something I should already know, but my 2008 451 doesn't have a tach :(I need to know where the redline is. I don't mean Mike's idea of what a redline is... I mean the actual red line printed on the tach face. This is a picture, but its a Euro car with turbo (speedo goes to 200) so I wasn't sure if it was the same here. And without a tach, obviously I can't walk out and check.Much appreciated.post-8-1216428144_thumb.jpg - Steven

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Plug in the ScanGauge, set it to RPM, put it in auto mode and floor it through the gears, stop and then check the highest RPM on the drive ;)I wonder if the engine computer actually lets it go beyond the nominal redline as marked on the tach......just like the cdi, whose actual redline is ~4500, using the technique above.heh heh

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Here's a pic of the tach. Looks like 6,000 rpm redline.post-629-1216435658_thumb.jpg

Yeah but I've seen mine go to over 6,400 or 6,500 when floored in auto-mode.

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Redline does not mean some hard limit guys. Its the line you shouldn't be crossing in normal operation of your car... past there you have the potential to damage your engine in prolonged use. Redline doesn't mean a maximum that the engine will go. So the redline on the cdi (or any car) is exactly where the little red line is painted on the dial. A scangauge can't tell you your redline.Its also certainly not the point of shifting, so putting it in auto and pulling off the highest RPM point is not getting you your redline either.Tom P got it for me... photo says it all. Thanks. - Steven

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Redline in a car that has an electronic rev limiter = maximum possible engine RPM. Redline on a tach was only meaningful before cars had electronic rev limiters.

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Sure, whatever. That's your opinion of what "redline" means and you're entitled to it. Contrary to most credible sources though. In any event, I asked specifically for the stated redline and it was provided.

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Using your definition, a car without a tachometer has no redline, :lol:

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K, I don't mean to stir the pot, but. In my work truck, an 08 GMC Sierra 1500, with 5.3L V8 and 4 spd auto, there is no mark on the tach for redline. It goes up to 6K rpm. It only has 3500kms on it so I have "tested" it to see how far the needle on tach will go. Where would you define "redline" for that?

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Exactly how a redline is defined:

Redline refers to the maximum engine speed at which an internal combustion engine or traction motor and its components are designed to operate without causing damage to the components themselves or other parts of the engine.

In most cases, that's where they paint the little red line. If GM ran out of red paint for your truck, then its whatever the redline is stated to be in your manual. Anyway... yours is a moot point because its an auto. They don't need to tell you the redline because your tranny knows what's what.

This wasn't really that complicated of a question. Thanks again to Tom P for keeping it real.

- Steven

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I know that the tach is for info only on an auto. But usually they still have a red line. If you wouldn't use D, but 3, 2, or 1, I could probably get it to go past redline. Unless it has a protection system like the smart and will shift anyway.K, I don't need an answer. I was just saying there are other configurations out there that make the redline a blurry one.

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The LY5 Gen IV 5.3 in your truck does not technically have a "redline" (unless it's an aluminum block, then it's an LH6 but for the purposes of this discussion it doesn't make a difference)

linky

Instead, GM decides to list a "fuel shutoff" rpm of 6000, which would essentially be the smae as above posters are describing as the "redline". There is a difference between a fuel shutoff and a redline. My Mom's old Integra's redline was at 6800 rpm (as indicated on the tach) but the fuel shut off was at 7500 rpm. This basically means that turning your engine faster than 6800 was detrimental to the health of your engine, but you could do it if you wanted to. I have also heard these being described as a "soft" and a "hard" redline... the soft one being the redline on the tach, and the hard redline being the fuel cut.

For this example, the LY5 peak HP is 315 at 5200 rpm, and the fuel cut is at 6000 rpm. I have talked to my foreman and he agrees that the fuel shutoff is the same as the redline for the engine because there is no need to be able to rev the engine higher than that. This means your tach has a maximum reading of 6000 rpm, so no need for a "soft" or indicated redline.

Now, if only they did the same for speedometers... they should go up to 120 kph in Canada... no higher. This would stop a lot of tom-foolery by young'uns when they see their Mom's RSX's speedo goes to 240 kph and... I digress, but you get the point ;)

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There you go, 6400, not 6000.

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And to stir the pot a little more, factory tachs are notoriously innacurate (along with factory speedo's) This is why racers never use a factory tach, but a quality aftermarket unit. In my racecar, the factory tach can be as much as 1000RPM behind my Autometer tach.

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I mean the actual red line printed on the tach face

Lordie... the redline is 6000. Question asked and answered by Tom P a long time ago.:)Everything... no matter how simple... always has to end up in an in-depth discussion and argument lolCheers all. - Steven

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Everything... no matter how simple... always has to end up in an in-depth discussion and argument lolI wouldn't really say they are arguments as much as difference of opinions and discussions, which I think is what this site is all about...just my opinion.

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They paint the red line on the tach at a lower rpm than the real "redline" of the engine so that when people floor it they think "oh man I'm going so fast, I'm past the redline, my car is so fast and cool, I will tell everyone how cool my car is and get them to buy one too!"

Seriously, take the sarcasm out of that and you have the real reason. Painting the tach like that is a psychological thing. Redline on an engine is where the ignition (or fuel) cut occurs. That's the maximum design speed of the engine for the intended operating life of said engine.

Saying the "redline" is where they painted the red line on the tach is like saying that a car with a speedo that indicates 240km/h can actually do 240 km/h, which in most cases, it can't. My old truck had a 240 km/h speedo but was electronically limited to 160km/h, and it, too, had a red-line-less tach, with only white lines up until 6000rpm which coincides with the ignition cut.

Just for shoots and giggles, my race bike red-lines at 16 500rpm.

Edited by booneylander

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