Safe Rev Limiter Rpms On A Stock Motor? And 5.8 Vs 5.4?

[ShelbyGT5HUN]

What is considered a safe limit for the rev limiter on a 2010? My tuner shop made it 6600 rpms.

Why does the 5.8 come with a higher stock rev limit than the 5.4? What changes in design allowed this?

Thanks!

[Madlock]

I don't know anybody who'd want the responsibility of vouching for how high an engine can safely rev, but I'd sure presume the red line exists for a reason.

 

By evolving the iron 5.4 block into Aluminum and then to a bigger bore, I suspect a whole range of properties improved from heat dissipation and cooling to the PTWA process and lighter and stronger internals, all of which are likely contributors in part. I doubt the entire difference is attributable to any one change or improvement in particular.

 

One feature mentioned often is the CF propshaft whose reduced rotational mass and inertia make it possible to spin at much higher speeds and most importantly to spin safely at extreme revs which was a key contributor to the higher top speed in addition to the taller gearing.

 

With all the metallurgical advanced that have been made, I wouldn't even presume the iron block to be any better or stronger than the aluminum except perhaps in a very specific and arbitrary handful of ways - and then more different than better. Iron obviously wears better for cylinder walls which seems to be why that's the limit of how Ford now uses it.

 

On the other hand, exotics and F1 teams have been making iron V12s that rev to obscene levels for decades, which only convinces me more that it's as much about how the materials are used as the materials themselves. For obvious reasons most champion sprinters wouldn't necessarily make great fullbacks, and not many F1 motors would make great road car engines.

[twobjshelbys]

Doesn't the 5.8 ('13 and '14) allow the engine to go to 6600 for brief periods of time then cut back to 6000 max? I thought I remembered seeing this. I think you need to go with the manufacturer here. Unless you're changing the internals, the engine is spec'd to have a long life at that RPM. Anything above that and you'll have a risk of early failure not covered by warranty.

[2010KonaBlueGT]

, but I'd sure presume the red line exists for a reason.

 

 

Yes, it's called "Warranty".

 

 

Phill

[2010KonaBlueGT]

Doesn't the 5.8 ('13 and '14) allow the engine to go to 6600 for brief periods of time then cut back to 6000 max? I thought I remembered seeing this.

 

The redline is 7K for 4 seconds, then cuts back to 6250 until rpm goes under some threashold again.

 

Or something like that. I know it's 7000 and 6250, I just can't remember for sure the time allowed.

 

And it's not due the block, it's due to the internals.

 

 

Phill

[ShelbyGT5HUN]

So is 6600 too much? What do most people have it set at here? I got my tune from one of the top places you can order one.

[1 Alibi 2]

My 2011 is red lined @ 6800,( factory fuel shut-off was 6250 ), my tuner considers it a safe level.

( he used to work for Ford as a tuner )

.

I would expect my 14, which is in the shop currently, to keep it's factory red line.

Ford provides the below info for the 13/14 MY motors.

.

" For such occasions SVT has provided for up to 7,000-rpm over-rev bursts. As soon as 6,250 rpm is exceeded, a clock begins in Copperhead, and it allows up to eight seconds at 7,000 rpm as long as the rev limiter (fuel shut-off) is not reached. After eight seconds at 7,000 rpm, the PCM will drag rpm down to 6,250 and hold it there indefinitely. "