Boost PSI

[Blueox01]

Any opinions on have much boost i can safely run with a stock fuel system?

[AH64ID]

Are you still running the stock LP?You really need a fuel psi gauge to accurately answer that question on fuel data alone, but for the turbo's sake I would keep it to about 30.

[Blueox01]

Yes, i have the stock LP and a fuel press gauge.

[AH64ID]

Then slowly turn the boost up until you drop below 10psi, or hit 30 psi of boost..

This is mopar1973man's, and is the best case scenario, but staying above 10 is crucial!

[ISX]

I think he means turbo pressure. The HX35 is good up to 35psi, and so is your engine. Past that it becomes a heat generator and the turbo can't handle much more than 35 before it grenades. Getting your engine to 35psi is the part you need a lot of fuel for. You must have a chip because it will not get very far stock. The wastegate opens around 18-23psi which keeps you from going any higher. If you have enough fuel, you can outflow the wastegate, but most people just get boost elbows.

[AH64ID]

Correct, but the original question was how much boost can the stock fuel system handle... So turn up the boost, which takes fuel, until the fuel pressure drops.

[ISX]

Ah yes. So the only limit is fuel pressure or getting too much boost that the turbo can't handle. When you step on it and are getting up there in boost, eventually the stock lift pump will not be able to hold 10psi, that is when you know you have hit your limit. Keep an eye on EGT's too.Now I can reread my post and understand you 24v'ers Thanks AH64

[AH64ID]

Ah yes. So the only limit is fuel pressure or getting too much boost that the turbo can't handle. When you step on it and are getting up there in boost, eventually the stock lift pump will not be able to hold 10psi, that is when you know you have hit your limit. Keep an eye on EGT's too.

Yep, play with fuel and boost until you hit the boost, fuel, or EGT limit. In a perfect world you would hit your boost goal with good fuel psi and good EGT's.

[Mopar1973Man]

You can only cram so much air into the engine and then got to get it back out the exhaust. Eventually you get to what know as a choke point where the drive pressure (exhaust) rises faster than the boost pressure (Intake). From what I know the HX35 has a max of 35 PSI and the HY35 is a max of about 30 PSI

[JOHNFAK]

turn up the boost ?? How is that done - I thought it was just done through more fuel - so a chip ?? I still need to get a j-hook on my turbo. Side -q - related - the edge is how I monitor my boost - but assuming thats just getting the computer reading from the ecm/pcm or whatever right - as I don't actually have a dedicated boost gauge anywhere - unless there is a built in sensor it reads from factory ?? I think when you install a dedicated boost gauge you 'tap' the intake horn or use that 'boost bolt' - so how does edge measure ?

[Mopar1973Man]

turn up the boost ?? How is that done - I thought it was just done through more fuel - so a chip ??

Correct you need more fuel to drive the turbo more... As for the j-hook yes you going to need that to exceed the stock limts on the wastegate.

Side -q - related - the edge is how I monitor my boost - but assuming thats just getting the computer reading from the ecm/pcm or whatever right - as I don't actually have a dedicated boost gauge anywhere - unless there is a built in sensor it reads from factory ??

As for the Edge modules... Edge Juice gets its reading from the stock MAP sensor.

I think when you install a dedicated boost gauge you 'tap' the intake horn or use that 'boost bolt' - so how does edge measure ?

When you hook up the MAP sensor connectors its got connection at that point for boost fooling, MAP sensor reading etc. As for a mechanical gauge there is a 3/4" pipe plug just forward from the MAP sensor to tap for boost pressure...

[KOYOTE]

turn up the boost ?? How is that done - I thought it was just done through more fuel - so a chip ?? I still need to get a j-hook on my turbo. Side -q - related - the edge is how I monitor my boost - but assuming thats just getting the computer reading from the ecm/pcm or whatever right - as I don't actually have a dedicated boost gauge anywhere - unless there is a built in sensor it reads from factory ?? I think when you install a dedicated boost gauge you 'tap' the intake horn or use that 'boost bolt' - so how does edge measure ?

extra boost is created from more fuel, higher exhaust temp and faster exhaust expansion speed, but then you hit the waste gate so that has to be modified to hold more pressure. yes a 24v ecm measures boost through the manifold pressure sensor or boost sensor. this signal is stolen from the ecm and parameters are changed to fool the ecm into seeing less boost and as a result more fuel is added. i hit the hight exhaust temps. before anything else so a limiting factor will always present itself.

[JOHNFAK]

As for the Edge modules... Edge Juice gets its reading from the stock MAP sensor.

So - this isn't accurate so thats why people get dedicated Boost Sensors ?

[KOYOTE]

people get dedicated boost gauges for this reason but ive never installed a dedicated sensor for the edge, the box wires between the stock harness and sensor capturing the signal from sensor and reinterpeting to the ecm.

[Mopar1973Man]

Actually it good for 38-40 PSI according to Edge... Beyond that the MAP sensor is topped out and won't go any farther... So it up to you to supply a 0-60 PSI or a 0-100 PSI at that point... I'm currently using a 0-35 PSI Dipricol gauge. But I doubt you building for racing though... The other problem is digital displays update very slowly so as for seeing a sudden change of values a digital display is not going to do it. But a mechanical gauge will show turbo bark very clearly...

[JOHNFAK]

ok coolI was a bit confused if it was an actual 'boost' reading from a sensor ....... or just an 'interpreted' reading based on how much fuel/timing it was dumping etc. Sounds like its mainly a real reading based on MAP - but with fooling built in ? hope I interpreted correctly. Main reason kinda along with OP - is that I knew my HY should be maxed aroudn 30~35 ...... and thats why I am going to add my j-hook for towing etc - hopefully reduce EGT;'s a little when its really pulling .................. currently I see 21 - so figuring thats the wastegate - but wasn't sure if that was a 'real' pressure reading as obviously the wastegate will open at real pressure

[Mopar1973Man]

Yeap... The wastegate is opening early because of the HY35 design with a hard line. So yes your going to need a j-hook to hold it back a bit longer to build boost to keep the EGT's in check.

[Blueox01]

All of my gauges are direct readings nothing electric,where are you reading the fuel pressure before or after filte? When pulling 10k or better i'm pushing 20-22 psi w/7 psi fuel at 75 mph. a guy at diesel specialties here in omaha said as long as 7 psi is going to the injec pump i would be fine,but always looking for as much info as possible.

[ISX]

Yeah your well within boost pressure but your fuel pressure needs some work. There are 3 pages of information on this thread that should help you form an opinion on the pressure thing. http://forum.mopar1973man.com/showthread.php/1656-VP44-Write-Up-Minimum-pressure-suggested...

[Mopar1973Man]

All of my gauges are direct readings nothing electric,where are you reading the fuel pressure before or after filte? When pulling 10k or better i'm pushing 20-22 psi w/7 psi fuel at 75 mph. a guy at diesel specialties here in omaha said as long as 7 psi is going to the injec pump i would be fine,but always looking for as much info as possible.

(Shakin' Head) Here is the flawed thinking... Ok... First off the factory requirement from dodge/Cummins is 10 PSI in there factory service manual. http://mopar.mopar1973man.com/cummins/2ndgen24v/fuel-pressure/fuel-pressure.htm Second off if you run the revised volume test by Dodge/Cummins with 8 PSI you'll fall the test every time... Then my long story to make you think outside the box. You know the VP44 has 1 inlet for fuel and 2 outlets for return (overflow valve and the injectors). So let say you ar holding 10-12 PSI typically. Driving around there might be enough flow to keep the pump happy with lubing and cooling for the electronics. But now if you like myself that runs the forest road and climb high in the mountain to get firewood Then on the return trip down I'm coast the entire way back to the highway jakin'. So this mean there is nothing going to the injectors while coasting (outlet #1 closed!) and since the fuel pressure is below 14 PSI (outlet #2 is limited if any!) So now where is the fuel going? Nowhere it can do it job of cooling and lubing the pump if there is no flow. My suggested minimum pressure is 14-15 PSI this will insure in all cases the overflow valve remains open flowing fuel through the VP44 keeping lubed and cooled even under complete stress... Below 14 PSI the flow is dependant on the amount of throttle your giving to keep the flow moving. But even Bosch noted that "At least 70% of the fuel should be return to the tank and only 30% of the fuel burned. This is for cooling and lubing purposes!" I can go on about stock pump volumes and such but I'm sure you getting a picture now...