My 97 psd has a 4.10 rear end, at 55 its at about 2000 rpm, at 70 its at 2500rpm. what is the safest rpm range to operate it at so i dont blow my motor up or somthing.

 

Put in the pyro gauge. That should determine your maximum operation range based upon EGT's.

Other than that, change your gears out to 3.73 if you want better mileage, lower RPM's, EGT's, etc.

 

RPM wise you are G to G. It'll turn 3400 rpm all day every day.

 

Hi Guys. When my truck get to about 3300 the boost will drop to about 15 lbs and the engine just lays down want rev any higher. Is that the Map triping the defueling mode or is the PCM limited?
Boost is about 21 lbs right before it drops.
CH

 

When your MAP sensor sees high boost, (about 21psi I think), the pcm will start to defuel.

 

Can you raise the boost " limit" before it defuels?

 

Chip it.
I installed the Diablo chip and in the 78 hp mode the boost gets over 25 lbs.
I installed a pop off pressure valve that is calibrated to 24 lbs. in the MAP line so the SES light doesn't come on.
I read somewhere that overboosting 25 lbs + isn't good on the heads?

 

More than 25psi won't do the stock turbo any good, but the heads will be fine. The stock head gaskets will live to ~ 40 psi.


3400 is the factory rev limiter.

 

I've got the SCMT 80h and have seen 27psi pulling a 78' Bronco from OK. back to CO. Yes, my light came on...but I couldn't feel any power loss. The light goes out after 1-3min.

 

Install any of the devices that keep the light off and you will be able to tell the difference.

 

As cookie88 said, installing any of the devices that fool the MAP sensor will not change the amount of boost your truck produces, but it will reduce the amount your MAP sensor sees, so it won't defuel when you get to the 22psi level.

 

It is a very good question, what is the safe operating range. Crawling around in the woods how low is to low and how high can it be reved without hurting it while it tries to fing the bottom of a mud hole and theres no time to shift?

 

There shouldn't be a too low crawling around in low gear, unless it's so cold out the exhaust temps fall below 275 or so, but even then the chances of anything being damaged are pretty remote.


Like I said, the factory rev limiter is going to catch it at ~3400 rpm, and that is well below what it takes to hurt a PSD. It won't start floating valves until the 4000 rpm neighborhood.