Woodnthings - Since I started this thread, I've been scrutinizing my boost to and from work. The 45-mile drive involves a two-lane road with steep grades up and down, flat runs, high and low speed, and passing under all conditions. It's a veritable testbed and I get to experiment twice a day. My boost shoots to 20 and climbs the rest of the way to 27, but I don't notice anything like defueling in 60eM or 80e. As an experiment, I hooked the red line back up - stock did OK with the boost slowly creeping up to 17-18. Redline disconnected - peak at 20 PSI. The 60eM tune was pretty smoky and I wouldn't run it like that - but the 80e? In answer to that, I could always mount a valve in the cab that would feed the wastegate if I really really want to telegraph a message to the driver near my tailpipe. Nuthin' sez "up yers" quat lak uh lode-o-cole in yer winduh.

Shake-N-Bake - I so get the concept of tuned exhaust and it never crossed my mind that the boys at Ford would utilize this. I know a tuned exaust can also reduce/eliminate noise without a muffler, but I don't know if it can serve both functions simultaneously. Readers - take a look at a Stirling Engine on YouTube or one of the pedias... fascinating stuff that is a cousin to tuned exhaust. Now I'm not so sure I want to risk the 4" just yet - I need to do more research. If I had a problem to solve, that would be another matter. As for the 19.5 MPG - my red line has been disconnected since I tuned and I've achieved that economy several times, but always at lower altitude and/or warmer than 50-60 degrees. I have never had less than 16 MPG average (not towing), even in the worst of scenarios.

PaysonPSD - I'm with A/Ox4 on this... I wonder if the DP ignores this feedback. That's good info for me to consider and do some homework on. I don't see a tuner in your sig, do you have one?

kawcrasher - When you did your experiments with the red line, did you check the tailpipe while stomping on it? I see you have a tuner and 4" exhaust - were they installed in a sequence where you saw a difference in economy from the stock to the 4"?

 

Not if you get tunes to specifically ignore overboost and not set the CEL.

I have a DP Tuner. Live tuned in June 2010 and do not think an overboost tune was available at the time. It wasn't brought up anyway. OCR was installed three months prior so no defueling during live tuning and the subject didn't come up.

EDIT:

You MPG averages closely match mine when stock. I was closer to 19.9 MPG. Sometimes above 20 and sometimes around 17 depending on MPH and conditions. After new single shot hybrid sticks, 38R turbo, DP live tuning, in Aug 2010 I dynoed at 486/885 (inertia dyno) and my highway cruising MPG is slightly better then when it was totally stock. Have gotten slightly over 21 MPG at times. More HP, up to a point, does not decrease highway MPG. I have a 4" turbo back exhaust with muffler and an AIS intake.

Edit : More info on mods for the curious. Sticks are FFD (Casserly) 200/80 Hybrids (non-hybrids would have been just as good, maybe better), Walbro GLS 392 fuel pump, OCR, HPX, CCK (a type of fuel return) stock FPR housing with shimmed spring when dynoed but now have Guzzle's billet FPR housing with black spring (70+ PSI fuel pressure at idle, 60+ at WOT), and I still have the stock fuel bowl. I was running an Adenaline HPOP when dynoed. Run a TE T500 now. Tranny has a JW VB. No custom valve springs or head studs. Boost, tranny temp, EGT, HPOP pressure, fuel pressure and coolant temp ISSpro performax gauges.

 

BTW, I welcome cleatus12r's input here. I sent out an invite to the thread where all the carnage took place. I hope he's monitoring this or finds the invite - I can't PM him.

 

I think your result is no accident. In my opinion, the modifications that you have done to your truck highlight the concept of a well balanced package where modifications are carefully chosen to compliment each other. I also think that live tuning is a key ingredient when major modifications are present.

Sometimes the whole is greater than the sum of it's parts.

 

What a great thread!

 

Even on my 140 tune I a couple seconds of smoke until the boost catches up. Makes no difference if the WG line is hooked up or not. I get around 25 psi of boost with it hooked up.

The 4" exhaust is still in the box. The factory exhaust with the muffler deleted keeps my egts in check fine, so I haven't seen much of a reason to put it on.

 

I was told that the ocr wasn't needed with DP tunes. The only reason we still buy it is to get rid of the soft code do the cel doesn't come on. Also the icp lp or high code is delayed.

 

Most if not all tuners are turning off the overboost issue...

The only reason I have one installed now is to protect the MAP sensor from 40+ psi. It was never designed to see those boost levels.

I know at one point Matt was selling a different MAP sensor so he could fuel more linear up to the higher boost levels...

 

Good point Joe.

 

Good thinking.
I read something a while back about 3 Bar and 5 Bar MAP sensors but I haven't been able to figure out what that means exactly. Looks like the 5 Bar sensor can handle over 75 psi but is that the only difference? Are there other features available with 5 bar sensors? (such as baro calibrations etc...)

 

Yet another reason I consult here before I pull the trigger on anything with the truck. I will read some more on this... thank you for that!

Oooh! Oooh! I know this one - pick me! Pick me! 1 Bar = BARometric pressure at sea level as 1 unit (a little over 14 PSI or 33 feet depth underwater for the divers out there). 2 bar is twice the pressure of sea level... you get the idea. 5 bar is just under 75 PSI, so that would be max for the sensor.

I'm a little lost here, topping 40 PSI would exceed my boost gauge and the wastgate acts like a fuse at 27 PSI (as I understand it). I don't see how I would ever reach enough boost to damage a 3-bar sensor, but I haven't had time to think it all the way through yet.

I have one other concern that I forgot to ask last time: Does it hurt anything if I'm in the throttle hard and just let go? I watch the boost gauge slam from 27 to 0 so fast that I wonder about that.

Tuning the whole engine system from air/fuel-in to the exhaust pipe makes good sense to me and I want to keep my system balanced (no weak links). I'm still on the fence with the 4" exhaust because I've heard good and bad, but PaysonPSD's input about his system similar to mine is valuable input. Does anyone know anybody who lost MPG with the 4"? I'd like to know if they had some kind of imbalance in the system or if another factor was overlooked and the 4" just ended up in the crosshairs. Should I start a separate thread with that heading to get the info I'm looking for?

 

Short term. No its fine. Long term, it can wear on some seals and the shaft.

I asked about this on my truck because I thought I had turbo flutter. Actually what I was seeing is called turbo stall, when the boost demand is drastically lowered in a short time, such as WOT to No Throttle or some shifts.

Turbo Stall - F250 7.3 Powerstroke - YouTube

 

I watched your video and that looked pretty good to me, plus I notice you have a manual. With my automatic, I reverse the load from pushing to pulling in a flash and the needle on the boost gauge does nothing less than what I would term as a "crash" to 0. I'd better re-think how I use the throttle when I pass. I'm still not used to that kind of oomph in OD or a turbo and I'd better pay closer attention before my turbo visits my last transmission.

 

I think I'm leaning toward a 4" at this point, but I'll wait for two things to happen first:

1. I'm getting the AE as planned and I want to get to know the sensor readings as a "late baseline" for all future mods/repairs. It was not practical to do this before because the repairs/upgrades had high priority.
2. Tax return cometh. I have the green now, but I hate to drain when I have the option to maintain.

I'd almost bet that AE will suggest I get a HPOP and/or injectors... but that's more of a no-brainer. Low pressure at higher RPMS? Just buy the friggin' thing. Weak injectors? Get 'em rebuilt.

I see yellow tape in my future.

 

i have the same thing basically with the OBA "overboost annihalator purchased from Dennis at ITP Diesel. It tricks the map into never seeing anything above 21 boost to keep it from de-fueling. Never had a problem!