Looking for some understanding on Vac wastegate...

[great white]

I've noticed everyone "in the know" on this board seems to recommend removing the vacuum pump and installing a "turbo master".

I guess the big question is "why"?

Why not just replace the Vac pump and get another couple hundred thou KM's out of it?

I understand the elimination of another rotating/wearing component (pump) and I understand the need for a shorter belt, but I have some specific questions:

1. My truck is a 98 L65. My understanding is the PCM controls/monitors the boost and when it comes on and off. Obviously, this function will be lost with a TM. Is this and issue for the PCM?

2.What about fuel MPG? what effects are there? (less, more, same, etc)

3. Will it effect engine life? (ie: overboost, never backs off boost, etc)

4. Engine performance effect?

5. What is the advantage of a TM over the stock system?

6. How does a TM operate? It seems to be a fixed rod, so does it deliver the same boost all the time or is is dependant on gas exhaust speed for increasing boost? If so, are boost levels linear?

7. Do you absolutely need a boost gauge with a TM? I only ask because I haven't installed a boost gauge yet (funds are tight right now, egt will most likely come first).


I'm just looking to formulate a plan for moving forward on this old girl. Yet to be explored is supplemental oil filtration (FS-2500/centrifuge/etc), supplemental fuel filtration/water separation/fuel heater, gauges, cooling system filtration, etc etc etc.......

Obviously, a lot to be done that will takes years to complete. just doing the research right now to have it all in place when my 404 000 km engine "gives up the ghost"....hopefully, not for several years yet!

 

[ak diesel driver]

1. the pcm does control the boost only an issue if you set it too high

2. Depending on how you drive you mileage can go up or down. Mine went up. the mpg change is small up or down.

3. the turbo master whether factory made or homemade is adjustable and uses a spring to control amount of boost. as long as your not over boosting shouldn't affect engine life.

4.will improve engine performance but most gains will be had with a chip then it will really shine. It will also lower egts (more air thru engine)

5.if you put a gauge on your truck you will notice the factory programming really sucks. the TM will give you a more "normal" boost.

6. See #3

7. if you by a factory made one from Heath it will give you a a spring length to set it to and still be safe. Gauges are always recommended.

If your planning on any hp improvements the TM reallys helps. And a factory made TM is about the same $ as a vac pump.

 

[JiFaire]

Nice summary, AK! Can't add much to that!

 

[JMJNet]

Great summary from AK.

In addition, the vac system have too many variables that can go wrong:
1. vac pump
2. vac lines
3. turbo solenoid
4. the diaphragm inside the turbo wastegate

With the aging truck, all those stuff are starting to go bad. My vac lines was so brittle that when I was working replacing my coolant quick connect just break by touching it at one place. Then when I tried to put some looms on my AC electrical cables, break on another spot. Good thing I have the TM already so I would not worry of patching them up.

I also like the performance improvement of the TM.

 

[Turbine Doc]

Agree with all the above, another detractor, with stock program it has a tendency to create what I like to call "boost shuffle or boost dance" especially when in cruise control, tow with a stock vac system stock programming you are into boost out of boost just as you need or don't need it, climb a hill in OD and it kicks down to 3rd to keep the energy up to make the boost stay up, just as you crest the hill the boost kicks out.

You run down the bottom side of the hill back in od @ low boost, start climbing again truck starts slowing down PCM sees this adds fuel, then kicks down trans engine revs hard, and at or just before the crest it all kicks out again which IMO adds a lot of undue-uneven loading of engine and premature cyclic failure of engine components, emphasis on the O of IMO.

With a TM or a non waste gated turbo I run with cruise control locked in and OD locked in and not have to "dance", a boost fooler is an electronic device that is sold by some vendors, or some home brew them, that add a resistor into the output of the MAP sensor so PCM does not know how much boost is produced, and this also works but relies on the vac system being fully functional.

After almost being stranded with 18K of load on my trailer and vac system crapping out on me I don't like vac systems, I had just gotten a TM and had it with me fortunately, after things had cooled off i installed it and got to my destination. For me KISS is the way to go, TM is mechanical spring over exhaust gas & very simple.

GM vac system is pump, lines, solenoids, (yes plural with S trucks) diaphragms, and a crappy algorithm from GM to contend with, so TM or now wastegated turbo is what works best for me.

Anther thought to ? #7 are gauges required, no, but when making changes to boost and fuel delivery HIGHLY RECOMMENDED to point of yes required,
even on stock vehicles I like to see them as they are a great diagnostic aid if you start having problems, over time you'll learn to drive by boost-egt-rpm for max efficiency

 

[buddy]

I prefer the vacuum system to TM. Factory program sucks and aftermarket programmers dont seem to understand where to apply the boost and where you do not want boost. They just put it high all the time, and fuel rate will essentially control it. A good custom boost curve will control your boost marvelously for best performane and economy. Lack of programing creativity has given the vac system a bad name, and effectively marketed another product. That and some people have bad experience with vac pumps. Buying vacuum hose is cheap, and the solenoid is pretty cheap too. My vac pump was still original from 94 with 100K miles on it, before I took it off for the ATT. Mechanical simplicity and reliability is a pro for the TM, it is less likely to fail. Vac system is simple to diagnose and repair though. If vac pumps were just less expensive it would be less of an issue.

The vacuum system anticipates changes in fuel rates, not react. It also will hold the wastegate shut when spring will give, so none of that boost bleed down as RPMs rise. And it can open the wastegate at any time you dont want boost that a spring will pull it closed. So you can cruise with 2psi for less exhaust restriction, than 4-5psi with TM making the engine work more than it needs to. You dont need 5psi with 20mm3 fuel rate not towing. How does N/A truck get so efficient, no backpressure from turbo and retarded timing during cruise compared to boost program. But vac system will still allow boost to 20psi no problem if its programmed to. you need calibrated spring to get 20psi on acceleration and 2 psi criusing 70mph, but likely to not hold boost as well through acceleration.

 

[great white]

I prefer the vacuum system to TM. Factory program sucks and aftermarket programmers dont seem to understand where to apply the boost and where you do not want boost. They just put it high all the time, and fuel rate will essentially control it. A good custom boost curve will control your boost marvelously for best performane and economy. Lack of programing creativity has given the vac system a bad name, and effectively marketed another product. That and some people have bad experience with vac pumps. Buying vacuum hose is cheap, and the solenoid is pretty cheap too. My vac pump was still original from 94 with 100K miles on it, before I took it off for the ATT. Mechanical simplicity and reliability is a pro for the TM, it is less likely to fail. Vac system is simple to diagnose and repair though. If vac pumps were just less expensive it would be less of an issue.

The vacuum system anticipates changes in fuel rates, not react. It also will hold the wastegate shut when spring will give, so none of that boost bleed down as RPMs rise. And it can open the wastegate at any time you dont want boost that a spring will pull it closed. So you can cruise with 2psi for less exhaust restriction, than 4-5psi with TM making the engine work more than it needs to. You dont need 5psi with 20mm3 fuel rate not towing. How does N/A truck get so efficient, no backpressure from turbo and retarded timing during cruise compared to boost program. But vac system will still allow boost to 20psi no problem if its programmed to. you need calibrated spring to get 20psi on acceleration and 2 psi criusing 70mph, but likely to not hold boost as well through acceleration.

tell me more:

Where would one find someone capable of tuning the "boost curve" or find the software to allow user tuned boost?

I've tuned OBDI on gassers before, not that hard except for chip burning (more a PITA than anything else).

The issue I'm finding with this truck is something that will allow user programming.....

 

[Turbine Doc]

For a program, the one many of us here like is one sold by www.heathdiesel.com Bill can set it up to work with the vac system, or my preference was the one he matched up to use with the TM. Buddy makes some good points, but properly set up a TM can be more effective than the vac system.

 

[Turbine Doc]

tell me more:


The issue I'm finding with this truck is something that will allow user programming.....

Yup OBD-II requires that the PCM has to go to the programmer to be set, there was once an offering selling a tuner device, it was quite spendy, and kind of risky unless you knew what tuning tables were doing so I think it was pulled from the marketplace.

I've been running the Heath tune in several variations/improvements since the 1st came out. As well as several other vendors which did not match what Heath's does.

 

[buddy]

For yours I would talk to Walking J Designs for a custom Kojo tune, providing the desired timing/fuel/boost profiles. Here are pics of one Ive done for my truck and the stock. If you dont want to maintain boost it can be cut as RPM increases just like the stock program. Or you can make it go higher or lower anywhere you want that makes sense and there is fuel and rpm to make the boost. the aftermarket I have seen will set it all to 10 or 12 or 15 or have some sort of stack, just not thinking about when you dont want boost. When you are sitting at 2400rpm and only consiming 20mm3, then you are not under load going 75mph you dont need boost so it would be about 2psi, but as soon as you are at 2400rpm and 40mm3, like towing at 60mph it would have 8psi boost. As RPMs go up the less fuel you have the less it must be under load. but high fuel at low rpm means high load. So the curve can be adjusted for different load scenarios.

 

[great white]

hold on a tick, looks like Westers has something on their web site for OBDII.

Pricey though....

Edit: Rats, seems you have to be a dealer or a shop before they'll even sell it to you....

 

[buddy]

Yes, the definition files at Westers are expensive. It makes more sense to let someone else customize it for you unless you are a racer that needs to tweak and test over and over, add another upgrade and retweak etc...

Those pics are the trucks PCM mapping, how it would attempt to contol the boost via the vacuum controlled wastegate actuator. The maps mean nothing when you take the vac system away. Other than it has to be able to tolerate the boost difference. Aftermaket tunes typically increase the tolerance of error from the table from 2psi to 4psi. And it takes 10seconds of that much error to set the DTC, so then it becomes very tolerable to a TM. Sometimes with aftermarket programs set all the way flat to 10psi or so people will code a boost DTC for too low boost with ATT, running 3psi when PCM wants 10, cruising down interstate empty. Also they could just disable to boost code all together.

 

[great white]

Yes, the definition files at Westers are expensive. It makes more sense to let someone else customize it for you unless you are a racer that needs to tweak and test over and over, add another upgrade and retweak etc...

Those pics are the trucks PCM mapping, how it would attempt to contol the boost via the vacuum controlled wastegate actuator. The maps mean nothing when you take the vac system away. Other than it has to be able to tolerate the boost difference. Aftermaket tunes typically increase the tolerance of error from the table from 2psi to 4psi. And it takes 10seconds of that much error to set the DTC, so then it becomes very tolerable to a TM. Sometimes with aftermarket programs set all the way flat to 10psi or so people will code a boost DTC for too low boost with ATT, running 3psi when PCM wants 10, cruising down interstate empty. Also they could just disable to boost code all together.

I'm not a "racer", but I am a clinically terminal tweaker....):h

for good software/hardware that is capable, I don't mind saving up the bucks to buy. Seems like Wester's is the only game in town, and even then I probably won't be able to buy it from them.

Yup, familiar with the mapping charts you posted. well, not the specific variables you posted, but I've worked with them before when tuning gassers.

I swapped my previous 350 over to TPI and had to get into tuning the fueling (ve, blm's, etc), spark curve/advance, etc. I've also messed with efi live on a 411 PCM equipped Vortec (actually, that PCM is sitting on the shelf in the garage right now).

Nice software...wish the 6.5 TD had some support.

That seems to be my particular forte though:

Buying and wanting to work on the "oddball" pieces......yeesh.

 

[buddy]

You would have to buy an emulator to get something that tunes on the fly like some of those new engine controller things. I just use offline programs to view and modify, burn, test in truck. Go back and modify, burn, test in truck, and so on and so... its a lot of time. Emulators are available though, but you still need the definition files. The 6.5 diesel files were kept tight for some reason. Whereas most every other EFI engine has the files on the web at multiple sites.

Those are snapshots from tunerpro, where I defined what the tables were and how the grid was layed out, and I can spin it 3D for any view of the curve.

 

[great white]

You would have to buy an emulator to get something that tunes on the fly like some of those new engine controller things. I just use offline programs to view and modify, burn, test in truck. Go back and modify, burn, test in truck, and so on and so... its a lot of time. Emulators are available though, but you still need the definition files. The 6.5 diesel files were kept tight for some reason. Whereas most every other EFI engine has the files on the web at multiple sites.

Those are snapshots from tunerpro, where I defined what the tables were and how the grid was layed out, and I can spin it 3D for any view of the curve.

I'm OBDII, which is a similar yet slightly different animal.

Are you refering to the mask for OBDI?

I believe I saw the mask numbers on the wester's site.

getting the definitions is a different story though. May be something in the Moates library...

 

[buddy]

mask or definition file I call it, a .XDF extension file for tunerpro are the ones not available, defines the table, constant and flag addresses and how the tables are layed out. The PCM programs are .BIN extension files. I have several BIN files from different trucks. And GMTDScanTech scanner software for OBDI can do a memory dump BIN file that can be emailed and I can load and view these curves and snap pictures

 

[great white]

From the Wester's garage site:

Mask......Pcm #............................................................................................EProm
$EC....16212488....94-95 C/K Truck, with 6.5L Turbo VIN "S" and VIN "F"..............27C512
$ECA...16212488....94-95 C/K Truck, with 6.5L Turbo VIN "S" and VIN "F" Variant....27C512
$ECB...16212488....94-95 C/K Truck, with 6.5L Turbo VIN "S" and VIN "F" Variant....27C512
$ECS...16212488....94-95 C/K Truck, with 6.5L Non-Turbo VIN "S" 4L60E...............27C512
$FD.....16212488....94-95 C/K Truck, with 6.5L Turbo Manual Trans......................27C512

The .xdf is the hacked definition files IIRC. It puts headers on the data tables so we an read them. Unfortunately, the 6.5 is (apparently) a bit of an orphan and not a lot of people have interest in hacking the programing.

a quick skim through the Moates site reveals nothing either

 

[great white]

Oops, maybe spoke too soon.

Drill down the list and the XDF files are apparently available here: http://www.3500z.com/60degree/Tuning Stuff/

Doesn't help me much, but maybe Buddy can use them....

 

[buddy]

I have seen those before, I had defined almost all of what I have before that though, disassembling the code with some help. Some of the things in those files are not correct, or even when it is the correct table the tables are not defined correctly. Its a good start for sure, but not to be trusted fully, and you really have to understand what youre doing.

 

[great white]

I have seen those before, I had defined almost all of what I have before that though, disassembling the code with some help. Some of the things in those files are not correct, or even when it is the correct table the tables are not defined correctly. Its a good start for sure, but not to be trusted fully, and you really have to understand what youre doing.

Very true...