4.6 Rev limit

Buckeyes903 · #1 Tue, November 10th, 2009, 03:20 PM

What is the highest safe rev limit for the 4.6?

Buckeyes903 · #2 Tue, November 10th, 2009, 04:34 PM

well I just read another post in which they said the torque converter will balloon at 5400 RPM's so am I safe to guess that 5400 would be the highest to set the RPM?

***88Racing*** · #3 Tue, November 10th, 2009, 04:41 PM

If it starts to balloon at 5400 then why set it at 5400. I would set it at 5000-5200.
JMHO
Lars

***88Racing*** · #4 Tue, November 10th, 2009, 04:47 PM

You may want to read through this:
http://dygytalworld.ehost-services13...=9248#post9248
Its something Jack put together and it may help?
JMHO
Lars

Buckeyes903 · #5 Tue, November 10th, 2009, 04:48 PM

Is the stock setting 5250? But I thought I have heard other people say that it is safe to increase it, so does the torque converter really begin to balloon at 5400? I guess I am just trying to find out some information more so then anything.

***88Racing*** · #6 Tue, November 10th, 2009, 05:11 PM

Sorry I started to think about something about shift points then realized what you were really asking. The power curve starts to drop after 5000 rpms. Set the max RPM at 5500. I wouldn't go much higher than those due to HP and torque dropoff above 5000 and torque converter ballooning above 5400. The only way around this is to install an aftermarket heavy duty torque convertor. Then you might want upgrade the valve body of the tranny to take on the additional stress because its a weak link also.
A domino effect.
JMHO
Lars

***Longshot270*** · #7 Tue, November 10th, 2009, 05:53 PM

I've got the 4.6 with a custom tune and the truck shifts around 5500 at WOT. I wouldn't go that high though. The only reason I'm leaving it is because I dont get up there very often. 5500 is what I would set the rev limiter and make the shift 200 RPM lower or more if it shifts funny.

***Jackpine*** · #8 Tue, November 10th, 2009, 06:10 PM

I'm getting in on this a bit late, but the 5400 rpm limit I've been posting is one that was posted by Mike Troyer (Troyer Performance) a couple years ago. It's the ONLY reference to an RPM limit I've ever found. Clearly, it applies to a specific transmission too. But, it seems to be a limit that doesn't ruffle anyone's feathers.

I think Bill has put the rev limit at 5600 in some tunes. My thinking here is that you're not really going to spend much time at all at this RPM, and, he posted somewhere that in early testing of the Edge, they set the RPM limit at 6000 on the test truck without causing damage. I would not risk that number. So, setting the limit a bit above the start of ballooning should not be a problem.

It's obvious you don't want to spend a long time at high RPM, ever. In my driving, pulling a trailer up long 7-8% grades of 8-10 miles, I regularly see RPMs over 4000 for longish periods in 2nd gear. This causes the Transmission Fluid Temperature to go up to between 215-220 degrees rather quickly. You're going to get fairly rapid breakdown in the fluid at this temperature and that can lead to early transmission failure.

Hope this all makes sense! I DO wish we could get a "Ford specified design limit". I know it has to exist, I just can't find it!

- Jack

Buckeyes903 · #9 Tue, November 10th, 2009, 06:40 PM

Sorry forgot to mention I have the 4.6, but it sounds like the trans and torque converter are the weak spots for RPM's. I didn't know if the 4.6 liked to be wound up a little more then the 5.4's but no point in destroying a transmission for a few more RPM's

***88Racing*** · #10 Tue, November 10th, 2009, 10:39 PM

Quote:

Originally Posted by Buckeyes903

Sorry forgot to mention I have the 4.6, but it sounds like the trans and torque converter are the weak spots for RPM's. I didn't know if the 4.6 liked to be wound up a little more then the 5.4's but no point in destroying a transmission for a few more RPM's

Spendy weak spots!

Lars