Still waiting for an correct answer...

What is the limiting mechanical factor necessitating the 5900rpm redline of the 5.7l iFarce engine?

I think it's the non-captive cam followers. Change my mind. Do so concisely and accurately, plz.

 

Me too.

 

Hey @ViktorG figured you'd probably be one of the few on here who would know.

 

Mechanically? not sure. Programmatically? it is the tune. My redline is at about 6400 rpm with the DAP tune. I have had the tune for 5 years now with no issues. Although, I rarely drive at redline.... but I do occasionally. I am not sure what damage might be done if I was always driving the truck at redline, but so far, so good.

 

I think it has to do with how quickly the valves can open and close (relating to springs?). At some point you have problems with pistons getting out of sync with valves which is a bad thing (tm).

 

Usually it would be valve float due to the lifters leaving the cam at high rpm's and not enough spring pressure BUT this is an overhead cam so highly unlikely spring pressures would be the limiting factor. My guess is performance degradation the further past max torque is what limited max RPM's.

 

Now days everything is limited by programming. Turn up programming get more rpm's. Not necessarily more horsepower just rpms. Which comes back to cam design and head flow which need to work in sync with each other.

 

Sorry, research has been inconclusive to date. Will continue testing with 6250rpm WOT shifts and report any findings.

 

@nobodyintexas might know also.

 

HellifIknow....I only hit 5k on a blue moon.

I'm tuned to 6k tho. My MAF was hitting 5volts. 8 psi blower....

I'm all stock intake.

so maybe the limiting factor is the 3.5 inlet?

 

If anything it is the connecting rods. Connecting rods fail when you bring it up to redline and then remove the air (close the throttle). Now instead of the piston nearly always pushing down on the rod because your are compressing air or burning fuel you are flinging the piston up and down.
Valve float is rarely a problem on a OHC with direct acting valves. It is is a problem on a pushrod engine with hydro lifters and rockers.
My bet would be that this engine is capable of a lot more than 5,900 RPM but the engine really does not make any more power beyond that so they set the limit and let it be.
Just my two cents.

 

My exact thought.

 

Its not a boat engine, and not a race car, so why exactly is this important?

 

I will respectfully disagree with you here. It is the 0 weight oil that is only good for gas mileage. If they used proper oil, it would redline at least 2,000 higher
Sorry, just had to do it.......

 

Remove those tow hooks and you gain a least 1,000 RPM. Oh and wind noise, rear wheels that part company, beds that hit cabs........

 

Higher probability of cam tower leak at higher RPMs due to increased vibration of the inferior, robot-installed grey gasketing material.

 

I was going to say that but then it implies they knew in 2007 that they would eventually delete it, which makes me sad.

 

I think redline issue was trying to be corrected when Toyota switched from 0w20 to 0w16, desired results were not achieved unfortunately. Rumor has it that a 0W-29 weight is being tested with a 36,599 redline.

 

is redline same in landcruiser?

 

I'm certain it's the AIP limiter....

 

I'd like to buy a vowel.

 

I believe the 5900 RPM limit from factory is due to the engine starting to lose power past that.
I don't know what the actual mechanical limit is since I have not blown up a 3UR from over-speeding it (yet), but we have revved the bone stock engine to 7000 RPM on the dyno multiple times without failure.
I personally do not suggest going much past 6500 RPM on the stock setup for longevity/safety reasons.
On my race truck with a forged bottom end, high lift cams, titanium valves, retainers and upgraded springs I have hit 7300 RPM a few times with no issues, still using the stock hydraulic lash adjusters and stock rockers.