My o4 f350 dually with mac air intake and predator set on 65hp setting sounds like it occaisionaly shoots air back out the intake. This usally happens when I give it hard throttle for a short time and then have to back out of it for one reason or another. Is this normal? any info would be helpful

 

I think that is normal- I experienced the same thing last winter when packing down a snowbank like a steamroller- needed lots of boost to get the truck rolling and climbing the bank, and when I let off, it chugged quite a bit, each time. That was before I did any mods. I have heard it a time or two since installing the Banks computer, in the same throttle on-then-off situation. I wouldn't worry about it, but could be wrong. I've put on 10,000 miles since first hearing the sound, and no problems.

 

When building a LOT of boost to accelerate and then chopping the throttle ...
all that boost has to go SOMEWHERE and since there is no wastegate, the backing up the intake is the least resistance, so it does !!!

 

Thanks for the feed back. I notice on some of the threads people are offering advice on launching the 6.0 at while drag racing. Since i am running DRW I dont seem to have a traction problem but I would like a little wheel spin to make a better launch. I still havnt turned the predator up to the hi-perf setting because the truck only has 600 miles on it. Any hints for when I turn it up?

 

believe it or not the 100 hp doesn't seem THAT much faster to me and the 65 gives better fuel economy (for an 8K lb shoe box !) so I've left it in the 65hp 99.99% of the time...

And even with the dually, if you brake stand and get the boost up I bet it will break the tires loose.... (but wait until it's brokern in )

 

hey, trust me, u powerbrake ur dually and u can leave 4 nice rubber stripes on the road, and thats in stock condition

 

Do you get 6 with 4WD? Or would that be 6WD?

 

Thanks guys I will try a little harder at the brake stand, But just a little for now, the truck still only has 800 miles on it.

 

I'd imagine that you will have no problems destroying your tires at any setting... at level 6 on my Banks 6-Gun (138HP), I have to be very careful about how much throttle I give it while merging- I've hit the rev limiter before when the wheels broke loose totally by accident. Although the guys I'm merging in front of seem to back off a bit when the see the black and blue somke of diesel and rubber...

 

OK... MAYBE it wasn't totally by accident...

 

My Stock '04 F350 SRW with about 1200 miles has apparently done what you describe two times.

Both times on a cold ehgine under light acceleration. It sounds like an old gasser with a burned intake valve. Like a very muffled spit- back into the carb/air cleaner on a gasser. But both times it was noticable to someone with a new truck. Like a single cylinder thing...just a "poof" like sound. It really doesn't even stumble..more of just a noticable noise thing.

(Maybe I'm just oversensitive?)

One other weird thing: I fueled up for the first time on a very hot day (about 95 degrees). Ran the truck down the highway about ten miles, pull in the driveway. When I put her in park, the engine would idle up and down a whole lot. Sitting there I thought it was going to cut off because the RPM's went so low. I finally figured that this was the AC compressor clutch cycling. Turn the AC off and it would stop misbehaving. The engine never shut off, but the idle would get so low you could feel it begin to stumble.

Shut her off, restarted, no problem. I am guessing something to do with cool fuel on a hot day? This has not occured again. (?????)

 

Interesting on the AC issue- may want to have your dealer check your idle speeds and the AC-idle interface. Not sure how they do it here on the PSD (computer maybe since it is fly-by-wire), but on older cars a solenoid physically picks the throttle up when the AC compressor kicks on. The throttle is advance at the same time the AC clutch is activated, so the engine revs a bit before the AC compressor loads it back down, creating the up and down like you describe.

I’m convinced the “puff-back” is 100% normal as you build boost in the intake and shut down its path into the cylinders as you cut the RPMs quickly.

 

This is "puffing" is called a turbo surge event.

Here's the scenario:
You lanch the truck.
To avoid smoke, the EGR is shut off.
RPMs climb rapidly.
You let off the accellerator and engine RPMs drop off fast.
Boost is still high because it lags.
Then EGR suddenly comes on displacing some of the fresh air that was flowing through the compressor side of the turbo.

The result is that boosted air (and EGR) back flows through the compressor side of the turbo causing a "puffing" sound. The sound is normally accompanied by a very short duration puff of black smoke from the exhaust because the sudden drop in boost starves the engine of air for just a split second.