Could it be as simple as the boost sensor not being accurate at higher numbers?

 

The mystery is solved, I'm waiting for the reaction from those who spot the root cause.

 

The red line not connected.....soot around the sensor.....or the location of the sensor.

 

The soot came from a tiny exhaust leak I found a few weeks back and immediately fixed, and it's normal to get rid of the red line - but the red line alone can't get the boost that high.

 

I wouldn't think there is much difference in hot side of the spider versus colder denser air.

 

The sensor is getting straight air out of the turbo, before the friction of the spider in/out, the boots, the plumbing to/from the intercooler, and the intercooler. I also need to work out what effect cooling the air has on a pressure reading. There will be a pressure differential at the higher boost numbers, but it won't be too much - just enough to not match what others are reading on their gauges with the same tunes. The MAP maxes out long before 30 PSI of boost, but I would guess the pressure differential could be anywhere from zero PSI at low boost to as much as 4 PSI at extereme boost. I might be getting 20 PSI stock and 26-28 PSI in 80e, but I need to really test this to nail down the differences.

My runs showed a difference, but I have not yet had a chance to measure it precisely. I need to have my video cam aimed at the boost gauge while I do a run with the MAP sensor recording.

Look at the second section of this article (nice picture, too) [LINK]

 

THUP! Whoosh! THUP! Whoosh! I split the rounds up. Casserly will send my injectors in a brown truck and my turbo will be adorned with yellow tape. I got the glow plugs while I was at it. Now... the fuel pump. Mine is old and has sucked more air than a Hoover, so I want to do just the slightest of upgrades. Full Force Diesel has a nice one for $150, does anybody have thoughts on this?

 

Surely you have (or can aquire) an analog boost gauge, hook it up and see what it reads. It also would be super cheap to relocate your existing sensor to the AIH port and see if the reading changes. A BMW crankcase drain plug is the perfect size to fit the AIH port. The nice thing about the BMW plug is that it is hollow and will drill and tap very easy.

 

Same with the Cummins drain plug. It to has the square for install. I drilled/tapped it for my boost port.

Tug, if at all, is one to worry about headstuds in regards to boost readings?

 

From everything I've learned, the head studs are not the issue with the 7.3L... at least not at this power level. PMRs are a problem, but I believe I have forged rods - that's my next homework assignment. I have time to get those on the way (if needed) while I wait for a brown truck to traverse thousands of miles of our interstate system to the Pacific Northwest.

My master plan is to stay with the mellower tunes and not go all-out. I'm more of a tortoise and I have no hair.

 

Tugly, I remember your first posts. I don't want to add HP just make it reliable etc.. You have came a long way. In last months Diesel power magazine they claim the Walbro lift pump for the 7.3L is best. It fits in the same place, hooks up to the 3/8" lines. Parts number GSL392. It say its a direct bolt-in replacement for factory 99-03 and can easily support 500HP. I think I read also if set at 65psi , it also holds that pressure at 65psi WOT. Just a thought. Can't wait to here more on this. Driving and power etc.. Been alot of guys on here doing your exact thing, but it is always nice to here more talk. Also report back at 500 miles and above to keep us updated on how happy and or if not.
Just looked up the pump, $113.oo at summit racing. I'm sure others sell it also.

Chet

 

Tugly,

Here on my thoughts on the boost difference. Warm air is thinner than cold air. Therefore, what might be 30 PSI on the hot side, could potentially condense when it cools. Lets go back to HS physics. Heat is excitement of atoms. Excitement of atoms means there is more space between them. Put air under pressure, you create heat because of the pressure. Hot air fills space X creating pressure Y. Cool down said air, and it fills less space, resulting in the same amount of air, at a lower pressure.

Hope that makes sense. Kind of a hard thing to write down, but I'm pretty sure that is whats happening to you. Not positive on the math, but with enough digging I'm sure you could find a conversion factor for it, and get an exact answer. It would also explain why it only happens at higher boost. Higher pressure, higher heat, more heat to be taken away when passed through intercooler, resulting in more drastic difference between hot side pressure and cold side pressure.

As for your fuel pump question. I run the walbro and it doesnt loose pressure with my firehoses as you call them. At WOT it will momentarily drop maybe 10PSI but will come right back up. As far as your system goes, I would think about putting on a filter water separator and pump set up on your frame rail. I know it may seem like a hassle, but I love mine. Better filtration than the fuel bowl, fuel bowl is eliminated, and to change fuel filter I simply unscrew a filter, prime the new one, and screw it on. Really easy. If you do it right, you also can eliminate the entire stock fuel system, which as you know is prone to letting air in. I know you just did a bunch of work on it, but it might be something to think about. You could grab the walbro, put it in place of the stocker for now, and then later down the road have the option.

Headstuds are never a bad thing to throw in, its good added security and peace of mind. However, with your power levels I would not say they are necessary.

Holy cow, your EGT's are very well checked...I'm impressed. Really makes me realize just how lacking my tuning is right now...

 

Quick disconnects - gone. Hutch mod - done. Fuel separator -



My 80e runs a little hot, but the 60e is all good.

80e 0 80 - YouTube


Walbro, eh? I am so freaking glad I asked! I'm on that like hair is on my back (the effects of gravity).

 

Walbro GSL392 - Walbro High Pressure Inline Fuel Pumps - Overview - SummitRacing.com

Does that mean, we can remove the FPR and install a plate, in its place? If thats the case, i wonder if we can get SNOWSEEKER to lathe up the o-ring plate..

 

I just had this conversation with my wife. Yes... she did ask about power because she likes it (gotta love a woman that shares your interests). Oddly enough, the power will be a byproduct of my goal: Tuning for power stretches the injector pulse width out to get more fuel in. The longer the pulse width, the later the fuel is added in the power cycle of the pistons - this is where the heat and smoke is generated.

Put a bigger nozzle on an injector and remove that split-shot hiccup, then you can dump the same quantity of fuel right up front in the power cycle and you get lower heat/smoke with an increase in power and economy. There may be a trade-off: I could lose some atomization with the bigger nozzles (heat and smoke right back at me), but everything tells me the T500 HPOP won't let this happen. All this lowers EGTs - bearing in mind the EGT guage also works as an inverse economy gauge.