ok i am new to this site i have had my 2000 f250 4wd SD for a week and i have been reading for the whole week about the pros and cons (compresser stalles boost spikes) what ia what and when when is what and how each thing would happen. now i worked on hondas with turbos and all that rices stuff i was young but i need to know. did a ford turbo system ever hhave a blowoff valve on it?? if not y?? the sound i get when the truck shifts sounds like a bov. i don't get the flutter but my friend does and now his turbo is junk(bully dog 200+ hp tune + turbo = bad) if i am wrong on the boost blowing off when you shift (i don't meen out the intake) also the wastegate will only let you build up so much boost (ie. wastegate set at 20 psi = after 20psi it opens and dumps the extra if it can) just somthing to start my brain thinking. and to see if a gass turbo system and diesel system is the same. if any of this is unclear just ask and that you for your time

 

The 7.3L DIT Diesel Engine uses an electronically controlled wastegated GTP38 turbocharger to control the intake manifold pressure. An intake manifold pressure sensor provides readings to the PCM, the PCM compares this reading with the vehicle speed and engine load then sends a signal to the solenoid control valve. The solenoid control valve alters the pressure applied to the wastegate actuator to provide the proper position for the wastegate valve providing the proper boost pressure.

There never was a BOV, the waistgate takes care of limiting boost (until we start "adjusting" it) And the PCM wil start to defuel around 25psi

The whoosh on shifting is excess boost bleeding back out through the intake as rpms drop, it doesn't have anywhere else to go.

 

ok now were talking. i know on a car turbo if you add a bov it should be about half way between the turbo and the intercooler. would this work for the diesel as well? this would keep the turbo from stalling out between shifts. yes or no?

 

The bleed off at shifts is not over boosting its just the boost that is no longer needed for the new lower rpm's (simplified example: 3rd gear at 18psi shift to 4th and need 12psi at the new rpm, the 6psi vents back out the intake) If a BOV was set to blow at that pressure it would blow under throttle and never let you build the boost you need.

 

yeah thats what i am getting at psi is set at 22 psi toy hit 22 psi and shift ther boost hast that .01 sec to build to 23 give or take a few the boost needs to go somewhere ie out the intake. but it you have bov inbetween there somewhere it will push the spring open at the set back press ie 23 psi. yet again this is how it works on a gas turbo system. it will keep it from pushing back on the turbo abd stalling it out. or the spike of 22 psi going the wrong way in a one way shoot. and building 20 psi when the turbo starts to spool again=42psi # just for ie (boost spike)

 

If you put a boost gauge in there you will see no spike only a sudden drop as you push in the clutch, which removes the load from the engine for a brief second. and then the boost will start building again from the lower pressure once the shift is completed.

 

i have a aod (4r100) tranny. the only reason i am digging so much is when i built my gas turbo engine i got a. air/fuel, boost, fuel press, egt, oil press and trans temp gauge. and all was well. just knowing what i know about cars the psd is just new to me and i want to know all that i cann i have even gone as far as to take online classes about the theory and construction on the diesel engine. pleas teach me i am willing to learn. (paint me i am a blank canvis(just kidding) )but i do want to know as much as i can.

Matthew

 

Check out the Common Mods and Maintenance link in my sig, we've databased many threads from here on alot of different subjects for the 7.3L

 

blacksiryder am I to assume (because you said you were a Honda man) that you drive a Black si, I have 1990 prelude si and haven't seen many Honda folks on the diesel forums

 

i had a 2003 blk si but i wanted a truck and a boat got them then just pushed a rod past it limits in the chevy got a 2000 f250 excab sb and just looking to know what i can i also had a 1986 prelude si. so yeah i'm a boost head my friend has a 2005 f350 that was pushing 60 psi ten the turbo turned into a gernade. i am just looking to know if a bov would do any good. i have a 5 inch turbo back exhaust 12 inch lift stage 2 hypertech program k&n filter. the turbonator (not mine came in the intake) i get 19 mpg on diesel 2

 

Diesels have no need for a blow off valve, as they do not have a throttle plate to restrict flow into the engine. When you let off the throttle most of the air still goes into the engine, however some does travel backwards out of the turbocharger. I have seen a few pulling trucks with blow off valves, only because they are running 5000+rpm's and pushing well over 100psi of boost at (im guessing) well over 2500cfm, and when they finish the pull they quickly return to idle when they cut the power and all that air cannot go out of the compressor!

Welcome to real turbocharging, sans sparkplugs.

 

yes keep it coming. i under stand. so by the time to shift and get back on it the air is pushing back the right way. no plate to close and reopen.

 

I can tell you are a gearhead that went astray with Hondas. The biggest point to walk away with is that when you make power with these trucks, you need way more than 22psi. The BOV is not used and a boost fooler is IOT get past the 25psi defuel setting the PCM uses when the MAP sends that signal.

Then, the wastegate tube is often disconnected for more boost. Now keep in mind that this is not the way to drive around, at least for me. I put the tube back on for normal driving but on the dyno and dragstrip, a totally different story.

 

Well, I'm usually the one to give the other side of the story, so here it is in a nutshell...

See my post# 11, 14, 16, 18, 21, and 24 here https://www.ford-trucks.com/forums/598058-whats-that-woshing-sound.html?highlight=bd+blow+off+valve Here's the link to the most popular blow-off valve used on Diesels... This valve is controlled by the computer, and is only activated when you let off the throttle and boost pressure tries to flow backward (and does) through the turbo which is not the best thing to let happen. The valve doesn't effect your normal boost when you're applying the throttle. With a diesel you can minimize the need for such a valve by slowly releasing the throttle, and not letting it snap back suddenly which cuts the fuel, and therefore the drive pressure to the turbine all at once, and is kind of like letting the throttle butterfly on a gasser slam shut, but not as bad a problem with a diesel as with a gasser.

http://www.strippermotorsports.com/bdd-1047220-s.html
"High-horsepower diesel trucks equipped with aftermarket turbochargers will typically display surge characteristics that can cause severe turbocharger failures. BD Diesel's Turbo Guards can prevent this surging. The Turbo Guards' blow-off valve protects your stock or aftermarket turbo from surging and the resulting compressor wheel explosions."

 

compressor wheel explosions.