The shaft is capable of withstanding the torsional forces required to compress air at 40 PSI with a drive pressure exceeding 55-60 PSI in most instances along with having a thrust washer capable of withstanding the axial forces imparted on the shaft at that pressure delta. It doesn't mean that it's going to create 40 PSI. Heck, one of PHP's test trucks (thanks to an accommodating customer) is running 250/200% injectors (at 550+ HP) and the boost is only 34 PSI with a stock 38R.

 

Awww c'mon.... You've always been so helpful and assertive about performance mods ruining a truck... and you're going from big sticks to really big sticks? Watching a pointless needle... when it is one of primary three add-on gauges? It's not pointless when you're looking for exhaust or boost leaks and you want to know what mark to look for when it's fixed. Oh... and how do you know your boost is 22 and not 21 or 23? Isn't that boost level about where the chip tells the PCM a lie to keep the PCM from defueling? I only ask because since boost gauges are pointless, I assume you're using the OBDII port to get your boost numbers.

It sucks when spoken to in a disrespectful way.

This is correct, I was not as precise when I said the 38R is capable of 40 PSI. That doesn't necessarily mean it's easily attainable. I still like the fact that I have a safety margine on my current turbo. I maxed my original turbo out on a whim.

 

I guess it did come across that way. It was not intentional and I apologize. My incessant frustration with the typical list of necessary items that people are forced into thinking they need to buy when trying to increase power finally came to a head and I am sorry that I took it out on you.

As a matter of fact, I have the same gauges you do. I rely on the OBD2 port for very little information because what I want to see isn't available; everything else is useless if the truck runs ok. Heck, the last time I used any scan tool for 7.3L diagnostics was a few weeks ago; after over six months of not touching one. My belief (and it's certainly not for everyone) is the feeling regarding the necessity of a boost pressure gauge because all it does is move around without giving any real data; but it's data on which people base performance capability. Truth be told, I have owned more than a couple stock 7.3L trucks and I have NEVER, EVER attained more than 15 PSI of boost in a stock state yet everyone and their mother claims that 17-18 PSI is the "norm". Does that mean that there was something wrong with these trucks? No. I would have chased my tail for months trying to figure out where in the world those pesky, elusive 2-3 PSI were hiding (and the HUGE power I was missing out on ) if I didn't know better. It seems like the "acceptable" numbers creep up over the years and then someone comes along and knocks them down. The bar then slowly keeps getting raised again until someone calls it out. Rinse, repeat.

I have an EV2 boost gauge (one in both of my personal trucks). There is no defueling going on anywhere. 50 PSI of drive pressure and 22 PSI of boost is right where my particular truck likes to run with the particular parts it has. It will run a higher boost level than that, but I can't see two counter-productive anomalies helping anything out; increased heat from a higher level of compressed air and increased drive pressure that does nothing but make the engine work harder for what it gets in return. Also, with valve springs having 256K miles on them, I don't want to "overpower" them with drive pressure trying to creep back into the cylinder. Airflow is paramount. The deciding factor on the absolute mass airflow through the engine is dictated by the area between the exhaust port beginning at the back of the valve and the turbine outlet; wastegate not withstanding.

As seen by just about everyone here, the compressor on a stock OR drop-in aftermarket turbocharger is capable of moving more air than the base engine can efficiently flow, otherwise we'd run at ambient manifold pressure (zero boost). However, the big restriction that causes the back-up (constipation) in the system is the region outlined in the previous paragraph. If you can't get the spent exhaust gasses out, you will not get any more air flowing through the engine. It's an absolute. Any air density (seen as boost) above what the exhaust side is able to accommodate just results in more boost with no additional gain in performance. Pressure above ambient creates a higher air density (read: more oxygen molecules in a given space) than ambient. This higher number of oxygen molecules gives us our power when "spooled" because we can effectively burn more fuel. The more fuel we can burn efficiently, the more power we can make.

However, air density is not equal to, nor is it related to actual airflow. This is where my big argument comes from. People with stock (or stock replacement) turbochargers that are hung up on making "big" boost numbers. At that point, boost becomes a number and a fun gauge needle to watch.....and that's it. Bigger is better, right? Think of it this way: If you have no exhaust restriction for driving the turbine, but you have a compressor that is moving a TON of air, what would the boost pressure be versus having a restrictive turbine that doesn't flow as much? In the first case, you'd have a TON of airflow but little "boost". In the second scenario, it would be just the opposite. If I could get the turbo response of the first setup (it would suck on the street), I'd take it in a heartbeat even though I could pretty much use a mechanical fuel pump pressure gauge (0-7 PSI) to monitor my boost at that point.


There is an instance where higher boost levels do help. However, running a small single turbocharger is not that instance. There is a reason people who make the BIG power on big single (with positive boost/drive pressure ratios) and compound setups with accurately set up wastegate systems can make HUGE boost numbers and still make power. It's called "airflow".


As we can see, there is a magnificent trade-off with turbochargers. Either flow a lot of air and hope that the truck moves out of it's own way before building enough heat and pressure to run the turbine, or use a turbine that chokes us on the high end but gets our cylinder air density higher, quicker.



Again, Rich, sorry about the earlier diatribe.

 

I guess that I could be more concise in my wording there, too.

My big problem with "mods" comes when people do it to their daily driver or their only vehicle and then get really pissed off when the truck doesn't start or run right (or blows up) and they can't get to work or their wedding. The truck in question here (my 2000) is one of four vehicles I have. It's 2wd so it's useless in the winter (albeit REALLY fun until it doesn't move without a tow strap) and it was purchased for ONE reason and that is to play with. It's a toy. I LOVE driving it because it's comfortable and low-stress; I do drive it most every time I can, but I don't NEED it. Heck, I put more miles on it over the year than any of the others but if I break it, so be it. I have another mode of transportation in that case.

It's got 256K on it, it's all stock other than injectors and the muffler (which is also a genuine Ford part). It's nothing more than a cheap, fun, and relaxing toy to me. In addition, it gets really good fuel mileage when I drive it nice. It's wonderful to be able to drive 600+ miles between pee-stops when driving across the country.

The moral of the story:
If you truly rely on the vehicle for daily life, don't spend a ton of money on it making it unreliable or finicky.


The truck in question:

 

We're all friends here... I crashed back at you a little hard as well. I apologize for my gut reaction.

Great info! Much of what you said covers a number of things that have come to my attention with the new injectors. My mod to a bigger turbo was to prevent damaging the stocker because I was already maxed out. This new one breathes nice and has a whole different "note" to it, but I did see the engine get real whimpy when I had the red line adjusted to dump anything over 22 PSI (not to mention the contrail-O-coal that showed as a result). Adjusting the wastegate to 35 PSI really stepped up the power, but I am not inclined to go any higher.

I was talking with 2000ca 250 and he replaced his valve springs. He mentioned there was a huge difference in performance (he has really big sticks, dual HPOPs, and bigger air). I don't know where the threshold is for the springs feeding the exhaust back into the cylinder... it's going to be different for every truck. I can see where weak valve springs and too much boost would rocket the pyrometer, but the acceleration would dip with this scenario (in my way of thinking). My experience (to date, with both sets of sticks) gives me more acceleration with a higher boost number. I could tinker with backing off the go pedal to regulate the boost down to 30 and see if I can feel a difference, but it takes just a few seconds for these sticks to poke at blue strobe lights. I'd need to get somewhere secluded to conduct this test.

Amen. I've taken Stinky right to the edge on this concept. I have backup vehicles, but I still don't want him to spend a bunch of time on the blocks. Sure, I have sticks that can give me great gobs-o-go (for my taste), but the goal is reliability, safety, and good towing performance. Dialing these things back down with the tune has given me what I was seeking... but there's a little something special in the tune for getting around the pokies on a two-lane highway. I like how these nozzles allow a tuner (such as yourself) to dial things up and down and back and forth, to fit the need of the task. Economy? Higher ICP, shorter PW, and adjust SOI as needed. Quieter tune? Drop the ICP, extend the PW (there's more room to move in the combustion window), and maybe delay the SOI. Towing? Tune for more torque and lower EGTs with whatever combination works for that. I haven't towed with these sticks yet, so I don't know what the formula is. I tried my tow tune empty, and I know at least one change in the tune.

Just as the text near my avatar declares, I am a cautionary tale. Going bigger on one thing means everything before and after that one thing needs to feed it and let it out. I blew a plenum seal on the first romp with my new sticks and turbo. I'm looking at my next intake upgrade to feed "Garrett". As Cody suggests, I might approach the need to replace the valve springs. I want to learn what more I can do with tuning to increase Stinky's lifespan, yet keep that Crackerjack surprise inside for when I open 'er up. I'm already driving Stinky like grandpa most of the time to increase the life span and get better fuel economy, but once in a while....

 

By the way, your truck is beautifully understated... a real sleeper. I want those wheels.

 

I was just curious a friend of mine has a pickup identicle to mine same mods same chip turbo everything and I have seen him hit 38. I didnt know if there is something wrong with my pickup or what

 

Talk about a hijack... you're just looking for a number and "War and Peace" lands atop your question.

 

Lol yea I aint special I know all the cfm and all that im a diesel mechanic I just dont understand why two ide tical trucks are so diff

 

Thank you both (Tugly and Cleatus) for seeing your way through this and continuing the conversation. Although I understand a lot about volumetric efficiency from gassers, I have a lot to learn about turbo deisels. And I am more in Tugly's camp, wanting reliable power to tow with. I can see where people get hung up on what these things are capable of, but for me I can't afford everything I might want to do, so a dose of moderation goes a long way.

 

Getting back to your stuff... good question. Same tuning guy? Same locations for the boost sensors? Same age/miles on the trucks? Same transmission, tire size, and gears in the rear? Injector wear, compression differences, nuances in the tunes, sensor differences (like ICP or EBP), etc.... There is almost no such thing as identical trucks after all these years and miles.

 

Thanks. I like to NOT draw attention to it. The wheels were a craigslist find. I paid $200 for the set and there's barely a mark on them. Helluva score if I may say so. I found the 305/50-20 tires on eBay (but they were only an hour from me) with only a few thousand miles on them for $400. I have yet to install spacers on the wheels because good ones cost a lot of money and I've too much to do before worrying about another 3" of total track width and being able to turn full-lock (or even remotely close to it right now).

I drove it for the last time with 160/100% injectors today. Tomorrow, the injectors will be in a truck belonging to one of my brother's co-workers. I'll miss it until late spring.......

 

I FIGURED IT OUT!!!

Where's my prize?

 

 

What the.... I must have skipped over that.