BOOST Tuning 101

[JSM]

Hopefully you have read FUEL Tuning 101. If not you should have.

One of the most complained about problems with SyTy's is boost control. I couldn't count how many people don't have good boost control and will go buy a $30 manual valve, etc. to correct it.

I am very ANTI manual valve for a couple reason's.

#1 They are an open loop control system. It works by bleeding air away from the actuator. It has no clue what boost you are at, it just says ok I bleed X amount of air.

#2 What happens if the boost is not enough? You turn the valve. "OK, thats better". Then you go test and oops, your buddy helping also turned the valve, or the neighbor kid was messing with things while you were not looking. Stuff happens. Now you don't know what boost you will get until you TRY it.

#3 Weather changes can cause boost changes. Almost anybody I have heard use one mentions this. Start asking around.

#4 Why RISK your engine, truck with a replacement cost of $4k or more (depending on build) over a $30 valve? Want to go parachuting with me, I have an extra chute I made with some string and a sheet it SHOULD be ok.

The alternatives are an aftermarket controller with feedback. (some better than others, some are great actually)

Or if still using stock computer the stock built in control.

Again if you use tunerpro with the def. files on nwstp I have layed them out so all the wastegate tables are in 1 location. There are some constants also above. You may even find notes on each table in tunerpro highlighting a table or constant and hitting F2.

So the boost tables include:

Desired Boost Pressure VS NTRPMX AND NTPSLD (F70)

This is the table that specifies your desired boost pressure based on TPS. Not sure why GM used tps, as typically under 100% throttle you won't get full boost anyways. As setup it does allow for different boost levels based on TPS though.

Wastegate Duty Cycle -vs- Delta TPS (F71)

This table is the starting point of the wastegate. 100% is fully closed actuator. 0% is fully open. If you find during a run your truck doesn't get to full boost at first but slowly climbs to desired level than you would increase the Initial WG Duty Cycle here. On the flip side if it overshoots then comes back you need to decrease the duty cycle.

One important change for us is Dig's hack for changing this to be -vs- MPH instead of TPS. The most recent promgrammer has the capability to perform the hack for you and I have listed the 2 different versions in the tunerpro definition. Some searching will probably find you more. (20-60mph, or 0-256mph).

This hack helps greatly with spikes as you can predict a gear change at a certain mile per hour and command a new starting WGDC. For example on 1 truck I have tuned, when it hit overdrive boost would jump up. So right before the shift I changed the WGDC to be much lower, controlling that jump.

Those are the main tables I use. There are some constants to be aware of though which include:

MAP High THRESHOLD ENABLING FUEL SHUTOFF

At what level does the computer turn off fuel do to an overboost condition. Manual valve cant do this now can it? In kPa.

MAP Low Thresh Disabling Fuel Shutoff

At what level does it turn the fuel back on after reaching the above condition. Normaly this is set smaller by about 10 kPa from above #.

POSITIVE/NEGATIVE STEP ADJUSTMENT TO WASTEGATE

If the desired boost is not obtained, how big of a change in WGDC does the ecm make to adjust. Large changes will get to desired boost faster but may jump around.

BOOST ERROR DEADBAND

How big of a window does the computer ignore boost before it makes correction. The computer will not make adjustments to WGDC if boost is within this window.

WasteGate Update Rate (Positive) and (Negative)

This is time based setting. This is how fast and often the computer adjusts boost.

There are more constants but those are the main ones to look at.


Part 2 added 8/12/08

 

[Robert Lone]

Re: BOOST Tuning 101

I'm going to put you in for a raise!!!

Thank God for too much free time!

 

[VermontTy]

Re: BOOST Tuning 101

Who's the babe licking the turbo? :boink:

 

[SEL777]

Re: BOOST Tuning 101

Both 101 posts are GREAT info. I really need to get my DM hard wire installed to see what is going on.

 

[gjp]

Re: BOOST Tuning 101

Is the DM the most accurate way to guage boost????? My greddy guage is at 1 bar but my DM is at 10lbs.???? HELP!!!!

 

[Bill Z]

Re: BOOST Tuning 101

Desired Boost Pressure VS NTRPMX AND NTPSLD (F70)

Wastegate Duty Cycle -vs- Delta TPS (F71)

MAP High THRESHOLD ENABLING FUEL SHUTOFF

MAP Low Thresh Disabling Fuel Shutoff

POSITIVE/NEGATIVE STEP ADJUSTMENT TO WASTEGATE

BOOST ERROR DEADBAND

WasteGate Update Rate (Positive) and (Negative)

.

I'm not sure but I think that DM doesn't display any of these values. How is one to know without the TunerPro hardware and programs?

 

[JSM]

Re: BOOST Tuning 101

I'm not sure but I think that DM doesn't display any of these values. How is one to know without the TunerPro hardware and programs?

That list is not information sent out through ALDL data but information/tables feed into the computer which gives final boost control.

ALDL is after the fact. Tuning and information in the chip itself is what starts the chain reaction.

Datamaster is purely a history book, nothing else.

 

[TYTILIDIE]

Re: BOOST Tuning 101

Just out of curiosity (even though Ill be finding out in the next few days) how solid can you get boost control with the stock set up? With my Profec, I can pretty much get just a solid straight line from start to finish. Can the stock set up get close? or even just as good?

 

[JSM]

Re: BOOST Tuning 101

If you adjust things, think about what is going on I have not had much problem getting the stock stuff to be fairly good. +/-2 psi. And I know I have only touched on all the settings and getting them right.

 

[turbodig]

Re: BOOST Tuning 101

Just out of curiosity (even though Ill be finding out in the next few days) how solid can you get boost control with the stock set up? With my Profec, I can pretty much get just a solid straight line from start to finish. Can the stock set up get close? or even just as good?

Best I've seen is +/- .5-.7 psi. Including gear changes and a TCC lock.

 

[WyoSyclone]

Re: BOOST Tuning 101

I haven't been able to find "Section 10 - Wastegate" of the P4 document anywhere... does anyone have it, or did it never exist??
Thanks,
Rob

 

[JSM]

Re: BOOST Tuning 101

PART 2 (added 8/12/08)

Boost Hardware

Good news is I think a lot of people are now learning and understanding how to adjust fuel and get that dialed in. I still get a lot of questions about boost control though, maybe for lack of easy information to be found on the subject.

So to add to this sticky here is part 2 which deals with how the hardware/solenoid works.

Internal or external waste gate doesn't really matter, they both work the same way. It was very common thinking at one time if you went external you couldn't use the stock control logic. That is not true. You will need to tune and adjust it sure, but it can and has been made to work and can work fairly well.

There are 3 major components, ECM (electrical signal, or aftermarket controller), electric solenoid, and the waste gate actuator.

The ECM will be sending out a 12v on/off signal to open/close the electric solenoid which in turns directs boost to the actuator (more on this later.). How long the solenoid stays open -vs- closed will change how much "boost" is directed through the lines to the actuator. If the solenoid is open 1 second, closed 1second, open 1 second, etc… we would say it has a 50% duty cycle. (Open half the time, and closed half the time). In true operation this valve will open MANY times per second.

For a very simple example if I had 10psi on a line going into a solenoid, and 50% duty cycle (D.C.) I would expect to see 5psi out of the output of the solenoid. (10psi * 50%). 80% duty cycle obviously would give us 8psi.

Depending on how the lines are hooked up to the solenoid (normally open or normally closed) will invert the readings. Normally open with 80% on time would be 8psi, if lines are on a normally closed side, 80% would be 2psi. The main idea here though is on our ECM 100% DC is MAX boost, 0% will be minimum boost.

2 versions of wastegates exist. Single port and dual port, It doesn't matter internal or external the canister is a diaphragm inside with a "helper" spring that somehow acts on a valve to redirect exhaust away from the turbine wheel to "slow" the turbo down controlling boost.

If the actuator has 2 ports you will find 1 port on each side of the diaphragm. If you put pressure on 1 side it will force the diaphragm to move 1 direction, put pressure on the other side it will obviously go the other direction.

Our stock actuator is a single port, with the 1 port. If you put pressure into that port it will move the actuator in a direction to OPEN the wastegate and give you LESS boost.

(edit thanks dig) Also, Base (or 'Canister) boost refers to how much boost you'll see with a hose connected from the canister directly to the boost supply. Or, that's how I define it, at least.

Removing the hose will get you the maximum boost achievable by a given spring/canister combo. The spring acts as a pop-off valve- when the turbine backpressure becomes great enough, it'll overcome the spring pressure, and open the valve slightly. This is normally a very large amount of backpressure, which results in a *lot* of boost pressure. The amount of backpressure needed to make this happen depends on the spring size (rate), and how much backpressure is on the back side of the WG valve in the housing.

Very similar thing goes on with 2 ports (most typically external waste gates). The port opposite side of the valve will increase boost as pressure is added. The port on the side closest to the valve is exactly the opposite and pressure added here will reduce boost. Word of caution. If you take an external WG, lets say you put in a 10psi spring no lines hooked up it will not give you 10psi or even close. They are designed to have what I call "helper" air to help open the valve. So to find base boost, you must run a pressure line to the bottom port, leave the top port unhooked. Don't expect a 10psi spring to give you exactly 10psi either. I currently have my typhoon with 4psi springs in them, hooked up for base boost (twin TIAL wg's.) At base I get between 5-7 psi of boost. With my setup and the springs I have this will be the bare minimum boost I can run.

There are 2 ways now to up the boost on a 2 port actuator. We can either add pressure to the top, helping keep it closed, or remove pressure from the bottom (which is trying to open the valve). Or you can do both.

Get you confused yet, if your still reading you must either be really bored, working on tuning boost, or just generally think I have wasted a lot of time.

Using my truck as an example, I am getting ready to "turn up the boost". Obviously gm never intended or thought the stock ECM would be controlling twin external WG's on a twin turbo v8. But there is no reason it can't and won't work.

So I personally have 2 options, add pressure to the top port, or remove pressure from bottom port. As luck would have it if I put a fitting on the top of the WG on the drivers side it hits the hood of my truck. Making the decision for me to remove boost from the bottom port easy.

So what I have is an electric solenoid (just like stock, but with threaded fittings instead of press on bungs) hooked up to the stock ECM. The computer will send a signal out 0% will be base boost (5-7psi in my case) 100% will be max boost (I have no idea what this could be, nor do I plan to find out either). What I am doing is t'ing off the pressure line that goes to the bottom port, and running it into the normally closed side of the solenoid. Normally closed (0% DC) the turbo will act just like I had not done anything, and be at base boost. As the solenoid opens up, pressure will be bleed of the line, reducing the amount of pressure into the WG actuator and the boost will increase. My desired boost now is 10psi, so to stay safe I am going to start at a DC of 10%. Might not be enough, might be too much. Small steps though.

Same thing would happen if I had a stock turbo/actuator. 10% would be a small increase over base boost.

So even though I hate them with a passion someone will want to know how a manual boost controller works. Very simple, you T off the pressure line and the valve you adjust is an orifice that is bleeding off pressure. The more you bleed off the higher the boost will go. (if using external). For a stock it would be opposite the less you bleed off the more boost.

If you search around and I know we have posted on www.code59.org several different ways to hook up the vacuum lines.

So now we hopefully understand mechanically how things work, lets go back into the ECM and in particular the tables referred to in part 1.

(NOTE: stock gm code for boost was based on Throttle Position. This doesn't make much sense so a common hack and one found built into code59 is to change it based on MPH. You will see me reference both TPS and MPH. I suggest everybody run the hack or just go to code59 based to take advantage of this change.)

​

The main tables that will need tuned/tweaked/adjusted are:

Desired Boost -vs- TPS/MPH (code hack)

Very simple. How much boost do you want to run. This value is what the ecm will compare actual boost to and make decisions. Simple but it needs to be correct. This information is also output in the ALDL stream.

Initial WG DC basec on TPS (stock) or MPH (code hack built into code 59)

90% of your tuning work will be with this table. Good news is not a lot of values will need to be filled in. It will take a lot of trial and error though.

The ecm has to start somewhere with a DC. This is the 'starting' point. If at 0mph you tell the ecm to output 40% DC, then that is where it will start.

Now assume your truck to run a desired 15psi needs 50% dc at 0mph. In this table we have 70% initial DC. The turbo will over boost, the ECM will see this problem and start to "correct" for it. By the time the ECM corrects chances are you have changed MPH, or got all excited because the boost is too high, or worse yet you have rods laying in a puddle of oil. It isn't the ECM's fault, yet it will get blamed. You feed it a wrong starting point.

Same thing can happen the other way, we tell ECM to start at 20% DC, when it really needs 50% DC. Now your complaining the boost wont' get to desired. Must be the ECM fault right?

(aftermarket controllers, at least the good ones teach themselves or learn what your truck needs, stock ecm can only do what it is told, not learn (maybe someday with code59)).
​

Keep in mind the DC that the turbo needs to maintain desired boost will change with weather, mph, load on the engine, Air fuel ratio, Exhaust temps, etc. You manual boost controller has inputs for all these right?

To be fair the stock ECM doesn't have inputs for all of these either, but it does have the ability to somewhat quickly determine if the boost is near what you want or not and make corrections. If the boost is too low it can add DC to increase it, too high and it can take DC away. This is high tech 80's technology here, but it works and isn't far off if any from what is available now.

The bad reputation the stock control got is not because the logic inside the ECM is bad, but because it was never told of that new 3" exhaust you installed, or the fact you changed the turbo out for something else, or maybe Billy Bob had great boost control and you have his chip but you don't have the exact same truck, modifications, or weather.

This is by far just touching on boost control and tuning it. Hopefully it will clear up a few things, get you started when things are not working as planned you will understand how it works and can troubleshoot it a bit easier.

 

[JSM]

Re: BOOST Tuning 101

I haven't been able to find "Section 10 - Wastegate" of the P4 document anywhere... does anyone have it, or did it never exist??
Thanks,
Rob

I think that section has always been missing, at least from the public.

I believe the doc was leaked out way back in the day. I have never seen that section either.

 

[turbodig]

Re: BOOST Tuning 101

Our stock actuator is a single port, with the 1 port. If you put pressure into that port it will move the actuator in a direction to CLOSE the wastegate and give you MORE boost. If you were to run no lines/pressure at all to the waste gate then only the spring would keep it closed, this is what is referred to as BASE BOOST. This will be the bare minimum boost you can run. If the base boost is higher than you want, or there is a mechanical binding no boost controller in the world will fix this problem.

I don't think you meant this.... if you put pressure to the port on the stock WG, it'll open the gate, creating less boost.

Also, Base (or 'Canister) boost refers to how much boost you'll see with a hose connected from the canister directly to the boost supply. Or, that's how I define it, at least.

Removing the hose will get you the maximum boost achievable by a given spring/canister combo. The spring acts as a pop-off valve- when the turbine backpressure becomes great enough, it'll overcome the spring pressure, and open the valve slightly. This is normally a very large amount of backpressure, which results in a *lot* of boost pressure. The amount of backpressure needed to make this happen depends on the spring size (rate), and how much backpressure is on the back side of the WG valve in the housing.

 

[JSM]

Re: BOOST Tuning 101

I don't think you meant this.... if you put pressure to the port on the stock WG, it'll open the gate, creating less boost.

Also, Base (or 'Canister) boost refers to how much boost you'll see with a hose connected from the canister directly to the boost supply. Or, that's how I define it, at least.

Removing the hose will get you the maximum boost achievable by a given spring/canister combo. The spring acts as a pop-off valve- when the turbine backpressure becomes great enough, it'll overcome the spring pressure, and open the valve slightly. This is normally a very large amount of backpressure, which results in a *lot* of boost pressure. The amount of backpressure needed to make this happen depends on the spring size (rate), and how much backpressure is on the back side of the WG valve in the housing.

Made a change, let me know if it should read a bit different.

Dig and Paul are working on really changing code59 website here in the near future with easier navigation and how to's. We will be adding a lot of things to that site soon. So anything I got wrong, need to clarify, rewrite let me know.

I even get confused sometimes, so good to see multiple eye balls on it.

 

[skwayb]

Re: BOOST Tuning 101

Original Post
http://www.syty.net/forums/showpost.php?p=891324&postcount=151

If you are using the ECM to control boost here are some tips for getting solid boost with the Stock ECM and Solenoid. By following these steps, I have rock solid boost on a PTE6776 (67 mm dual ball bearing turbo) on the stock ECM/Solenoid setup.


Boost/wastegate tuning Tips

• First Set the Desired Boost -vs- RPM and MPH (F70_MPH) to the PSI you are trying to hit across the board. (i.e. 16psi in every cell)
• Next turn any wastegate POSITIVE adjustments off
  • Positive Step Adjustment to Wastegate (KDCSTEP) set to 0
  • Closed Loop Wastegate Update - Positive Adjustment (KDCTIM8P) set to 0.0 seconds
  • LEAVE the NEGATIVE adjustments ALONE so if you overboost, it will back off the boost.
• Next set the F71 (Wastegate Duty Cycle -vs- MPH) to 0% and make a run. This will let you see what your base boost on the spring is going to be.
• Next set the F71 table to 10% across the board and make a run, then 20%, 30%,etc. This will let you see what % of wastegate will add x amount of boost. This will help you later when you want to run a different PSI, you will know how much Wastegate to add or subtract to hit your PSI goal.
• Do this until you get the wastegate dialed into hitting your target boost you set in the F70 table. Make notes of any spot where you overboost at a shift. You will want to adjust your wastegate down at these MPH spots in the F71 table where it occurs to stop the overboost from happening.

You want to get the F71 MPH (Wastegate Duty Cycle -vs- MPH) Wastegate % as close as possible to running the boost you want from the F70 MPH Desired Boost Table. Make sure there are no boost spikes at different MPHs when your shifts occur.

Once you have the base wastegate dialed in, you can turn this back on.
Positive Step Adjustment to Wastegate (KDCSTEP) set to 1.5-2% to start.
Closed Loop Wastegate Update - Positive Adjustment (KDCTIM8P) set to 0.5 - How often to update the wastegate if not reaching the target boost

This last settiing is one of the MOST IMPORTANT STEPS for getting SOLID Boost control. Slowing the change rate at which the wastegate is being updated to (Closed Loop Wastegate Update - Positive Adjustment (KDCTIM8P)) will let you creap up onto your boost if your initial wastegate F71 setting didn't hit your F70 boost PSI Target. Stock it is set to update 10 times a second (0.1). Change it to 0.5 so it only updates the wastegate twice a second. By doing this, it will stop your boost from fluctating all over the place.


For Overboost control I usually set these 2 items high.

• Negative Step Adjustment to Wastegate (KDCSTEN) set to 3-5% - Back the wastegate off alot
• Closed Loop Wastegate Update - Negative Adjustment (KDCTIM8N) - Set to 0.1 so it backs the wastegate off quickly. (10 times a second)

Those steps should get you solid boost. Like I said above, I have rock solid boost on a PTE67 turbo on a stock ECM/Solenoid control on a stock motor.

Now if you need to change your SPOOL UP behavior, that is another post..