Tuning from scratch

[Jim Blackwood]

Now that I have the 340 Buick running under '411 control, it's time to make it run well. A bit more complicated than adapting a Camaro tune, redline is set to 7500rpm and MAP to 170. All the usual, fan controls and such are done. The car is fitted with a wideband and EGT gage but neither of those are connected to the controller. The injector flow is set to 4.4gm/sec for 35lb injectors. I have run my first datalog using OBDwiz but am not impressed with the available choices for PIDs. I have run datalogs before on MS/TunerStudio and am comfortable with that type of graph display. Can anyone suggest better datalogging software?

As it stands right now, after starting the engine leans out badly and wants to die (14-15:1) and then eventually goes very rich and settles down to a nice idle (11:1). My datalog may indicate it is still in open loop, or I may not have the right PID included. Is this determined by engine temp, O2 sensor temp, or a time constant?

For initial set-up I've made use of the squirt bottle technique to verify rich or lean conditions and adjusted prime pulse and cold enrichment (B3632) as well as wholesale adjustment of the main VE table and the OL table (B3605)

First off, it seems counterintuitive that if it runs rich in OL after all the enrichments have timed out, that the enrichments could have caused any sort of a lean condition. Something else must be going on here but I don't know what. This, I think is the most important issue for getting on with the tuning.

What I'm missing here is a thorough understanding of which enrichments do what and how to tune them. For instance, I can easily accept that I may be missing a critical table, or that I'm adjusting the wrong thing. The B3632 table for instance. If it decays based on B3650 then how can it suitably compensate for coolant temp? And if it doesn't then why does my mixture go lean soon after starting? I richened it up quite a bit.

If anyone would care to have a look at this, my Bin and datalog are on the laptop but I can attach them. I just have to post this first then move over there.

Jim

Got the bin attached but it said the log was invalid. Not sure what to do about that, it was only 15kb.

[brian617]

First off, it seems counterintuitive that if it runs rich in OL after all the enrichments have timed out, that the enrichments could have caused any sort of a lean condition. Something else must be going on here but I don't know what. This, I think is the most important issue for getting on with the tuning.

Time to work on the VE table. Your Idle speed and MAP are changing via cells in the VE Table. Don't change enrichments until the VE is correct.

[DavidBraley]

Jim,

Because you are using the 0411, maybe something like this might help. I could be wrong, but I think it's part of, or an off-shoot of PCM Hammer:

https://pcmhacking.net/forums/viewtopic.php?f=42&t=6575

[Jim Blackwood]

One thing that I think might be worth trying: Tuner Studio has a graphical log viewing screen which is really quite good and I seem to recall that it can make use of .csv files so there could just be some slight chance of importing log files from other logging software into it. No idea if the labels would be anything close to right but it seems like something worth the effort.

Jim

[kur4o]

You need to start with the basic. Spark, ve tables and maf. Than work on other stuff.

Also find a bin with l31 engine and use some of the tables as template for spark. I guess will be the closest match for the buick.

Is this engine ever been run by a pcm. Ripping some stock tables and interpolate them from there will also give good results.

[Jim Blackwood]

As much as I appreciate the basic tuning advice I'm a little beyond that. The biggest problem with starting by tuning the VE table is that you first have to start the engine and then run it long enough to warm up, hopefully without washing the cylinders down in the process. Then you need numerous restarts in order to make changes to the table. The engine is a well broken in fresh build but with all this rich idling I'm starting to see blue smoke. I have to do something about that over-rich idle during warm up.

Yes, I understand that changes to the VE table will affect literally everything. Yet first it is necessary to get there. Now my ignition tables are just about right, certainly close enough for a Small Block Buick. I could build one of those in my sleep. After fueling is done I can fine tune that map. I've studied the instructions for using STFT and LTFT. My first datalog does not show the engine getting warm enough for closed loop but it wasn't running very long. I was hoping to lean out the idle before doing that. Up to this point my efforts have been perhaps not the best and that's why I'm asking for advice.

And yes, the engine was running under MS-II and running well. However I've not found MS to be particularly reliable. (over a period of nearly 2 decades)

So here's the sequence. Cranking may or may not produce immediate fire off. If it doesn't, a second turn of the key does. Then the engine settles down to a fast idle on the whatchacallit, PWM idle air thingamajiggit. (I know what it's called, give me a minute) Then it leans out and slows down to the point where it pops and crackles, begins surging and tries to die. If I nurse it past that using the squirt bottle the idle goes rich and it smooths out to a nice idle but it's puffing black smoke out the tailpipes, and I expect it'll run like that until it reaches operating temperature and maybe beyond. That's just not good for the engine.

What I want to do is lean that out. I'm GUESSING there are 2 ways to do that, with the main VE table and with B3605-commanded fuel in open loop. If that's correct, which one would you guys suggest? In MS I'd know what to do but this is quite a bit different.

I'm also not sure it is entering closed loop. I have a TPS error and a new one on order. Also a CKP error that I think I've corrected. But before testing again I want to lean out that rich idle. Yes I realize I will have to come back and re-tune it after the VE table is right. I'm less worried about that than I am about wiping out my rings.

Jim

[kur4o]

Fueling is derived by 2 tables maf and ve. You didn`t mentioned about the maf. Is it present at all. If it idles rich cut the ve tables in that region. If the startup adders are adding more than what is set, than air entering engine is not calculated correctly.

Bad tps can also throw a lot of troubles and if maf is not disabled correctly expect big headaches. If you have laying a maf plug it temporarily. You can dial it pretty fast compared to ve.

You must be sure that the inj data is spot on. If not switch back to stock inj for initial tuning.

Changing too many constants is not a good thing, you will never find the problem.

[Jim Blackwood]

Again, all good advice but...
First off there is no MAF, this is and can only be a speed/density tune. See photo. No place to put a MAF. My advance map is fine for this stage of the tune and I will fine tune it after fueling is set. It is very close, I'm quite familiar with what this engine needs and have been tuning small block Buicks for decades now, with EFI. I believe the changes for S/D are correct as I spent 3 weeks on the tune before ever turning the key the first time. The injectors flow rate is set to 4.4gm/min but again, I can double check anything y'all think I should look at. We've done this drill before. If a fault at the TPS will keep it out of closed loop I'd like to know. I suspect it could. At any rate all we are doing here is tuning fuel delivery or injector pulse width. The engine could care less how we get there, long as it gets what it wants, and it's a pretty simple device.

It would be nice to have the fueling algorithm to know what goes in and how. Mostly adders no doubt but for instance, when in open loop does the algorithm still use the VE table or does it substitute the open loop fueling table? And even is it uses both tables (which makes sense because the OL table has a temp axis) doesn't it make sense to adjust warmup in the OL table so the VE table stays flatter for initial tuning?

Based on my experience with tuning EFI systems I suggest the following initial process: Provided the advance map is reasonably close,
1) Enrich prime until the engine fires off
2) Enrich after-start for about a 1-2 second run
3) Add cold enrichment to get a smooth idle. With the '411 I would say this involves the open loop table and also the MAP based after-start enrichment. The question is, which one first? That may depend of whether or not the engine will continue to run. It might be advisable to zero out the after-start until later if the engine doesn't die. Then look at the AFRs and adjust accordingly.
4) After all of that, warm up the engine, adjusting the OL values incrementally, which will require several re-starts.
5) Finally, after the engine is warm and all the enrichments have dropped out, adjust the VE map for idle. Smooth the map into the surrounding areas using appropriate slope values. (Mostly a visual thing at this point)
6) Tune adjacent areas based on throttle response and AFR gage and blend map.
7) Either after cool down readjust fuel adders, or continue with STFT and LTFT and driveability tuning.

Now I've been stuck at step 3 due to confusion about the cold enrichments but I think I'm starting to make sense of them now. For me at this point it is more important to protect the rings than to be concerned about having to go back and balance the tables several times. In the end we are only supplying fuel. The right amount, too much, or too little. I fully understand the VE table being the foundation of that fuel delivery, but in the end each engine condition has a single fuel requirement and the engine cares not how you get there so long as you satisfy it's appetite. The balance can be off a bit and still work acceptably well.

But, if I continue to wash out the rings I can easily convert this brand new engine into a hopeless oil burner. I must prevent that above all else.

Jim

[kur4o]

Good that you post the bin. I managed to look at it and was mildly shocked with the ve and ol table settings.

I attache a bin with stock engine cal segment so you can use for comparison.

The ve is increased roughly 3 times and the target afr is 1.3-1.8 across the board.

A note how to use the OL table to get afr use 14.7 / value of table.

so value of 8 will give you 14.7/8= 1.83 AFR

14.7/1.065= 13.8 AFR

First fix those 2 tables and than we can continue the discussion.

[Jim Blackwood]

Ah, thank you. The multiplier was what I was missing. That I can work with. So in essence for both those tables (at least) the entered value is a multiplier, and acts on the requested AFR? I don't remember the name of the AFR table but I remember seeing a reference. Don't recall it being a full table though and maybe just a value. Something else to look into. Anyway this information will demand a whole new look at fueling but I'll try to run a test sometime tomorrow. Very helpful. It'll be real interesting to see how it all shakes out.

So if I understand correctly, during OL the afr is multiplied by the VE and then multiplied by the OL table value? I can see that resulting in some seriously high numbers very quickly. No wonder it was rich.

Jim

[tayto]

As much as I appreciate the basic tuning advice I'm a little beyond that. The biggest problem with starting by tuning the VE table is that you first have to start the engine and then run it long enough to warm up, hopefully without washing the cylinders down in the process. Then you need numerous restarts in order to make changes to the table. The engine is a well broken in fresh build but with all this rich idling I'm starting to see blue smoke. I have to do something about that over-rich idle during warm up.

Yes, I understand that changes to the VE table will affect literally everything. Yet first it is necessary to get there. Now my ignition tables are just about right, certainly close enough for a Small Block Buick. I could build one of those in my sleep. After fueling is done I can fine tune that map. I've studied the instructions for using STFT and LTFT. My first datalog does not show the engine getting warm enough for closed loop but it wasn't running very long. I was hoping to lean out the idle before doing that. Up to this point my efforts have been perhaps not the best and that's why I'm asking for advice.

And yes, the engine was running under MS-II and running well. However I've not found MS to be particularly reliable. (over a period of nearly 2 decades)

So here's the sequence. Cranking may or may not produce immediate fire off. If it doesn't, a second turn of the key does. Then the engine settles down to a fast idle on the whatchacallit, PWM idle air thingamajiggit. (I know what it's called, give me a minute) Then it leans out and slows down to the point where it pops and crackles, begins surging and tries to die. If I nurse it past that using the squirt bottle the idle goes rich and it smooths out to a nice idle but it's puffing black smoke out the tailpipes, and I expect it'll run like that until it reaches operating temperature and maybe beyond. That's just not good for the engine.

What I want to do is lean that out. I'm GUESSING there are 2 ways to do that, with the main VE table and with B3605-commanded fuel in open loop. If that's correct, which one would you guys suggest? In MS I'd know what to do but this is quite a bit different.

I'm also not sure it is entering closed loop. I have a TPS error and a new one on order. Also a CKP error that I think I've corrected. But before testing again I want to lean out that rich idle. Yes I realize I will have to come back and re-tune it after the VE table is right. I'm less worried about that than I am about wiping out my rings.

Jim

you'd have to have an injector stuck open to wash the walls down. i took a tuning seminar many years ago, if anything you'd want rich from starting out. i'd rather change plugs vs bearings or pistons.

[Jim Blackwood]

Been losing posts lately but oh well. Just went to check on something and now I get to practice my recall. So anyway, thanks for those two maps, they worked and look like a reasonable place to start over. I'm now on the other side of Stoich which is a better place to be. For now. As a point of interest, this controller uses a different algorithm because it takes the commanded AFR into account. Others use AFR numbers only in the optional autotune function. It means one is an adder where the other is a multiplier and that can result in one or two orders of magnitude difference by the end of the formula. Can't use the same numbers or the same range in other words. Worth remembering. Here you stay close to 1 which is unity. There you might be at 16 or higher with no decimal point.

So, back on track. Next, it would make a lot of sense to connect the output of the wideband to the PCM so it can be datalogged. Is there a preferred way you guys have found to do that?

Also, what is your favorite datalogger and why? The one I've used is purely a random choice.

And finally, what I went to check on and something I think can benefit you guys. The TunerStudio log viewing app is called MegaLogViewer and it is a pretty darned good graphical interface from EFI Analytics. You might have to register but it's free. It will open CSV files as well as a bunch of other formats and IIRC lets you select up to 16 color coded traces on up to 4 screens, and you can scroll through the datalog, resize, etc. so it makes it easy to compare blips and dips. Pretty feature rich, I'm still not familiar enough with it to know what all it will do. There ya' go, my effort to give back to the community.

Jim
(don't forget my 2 questions above)

[kur4o]

Here is a map of the pcm algorithm, so you get a better understanding how to tune.

The value from ve table is converted with charge temp, cyl volume and rpm to a mass of air entering engine in g/s. Now this your base scalar[mass air in g/s] for all fuel calculations.

The mass air is divided with the AFR target to get fuel mass needed for each cylinder. Than fuel mass is converted to inj PW by some calc involving rpm and fuel flow of inj.

So you need to set the Open loop afr table once with the preferred target and forget about it.

The best tuning is done in open loop by comparing the commanded AFR and actual AFR by adjusting ve table. How do you plan to tune boost with stock pcm, do you have 2 bar map or some external enrichment will be done.

Do you have a copy of the xdf.

For logging, tunerpro can be used but the built in obd plugin have some bugs. I still need to test the latest version. If all is good you can log any pid you need that the pcm support. Some custom patch can be done to support more than you need, like wideband on egr or ac input.

[Jim Blackwood]

Made some progress, it seems like the issue I had with the OBDLinkLX was very likely a Bluetooth interference problem although I can't be certain because in the process I upgraded a bunch of drivers and did a few other things that could have affected it. Still, the breakthrough came after I had turned off or deleted all the bluetooth in the area and then reconfigured just the one. So the bottom line is that my tuning laptop with PCMLogger now works. I have connected my WB-O2 output to C1-pin 55 and turned on the flag for B1301-EGR System Enable so I THINK the last thing to do is to include the EGR in the Log Profile for PCML. Anyone know how that should be done? I've heard it is a fairly common method for logging the WB. Once I get that I will run a log. I can post my xdf but not from this computer. I'll get that done though.

Jim

[Jim Blackwood]

kur4o I wanted to run something past you before I get too deep into the VE table. I'm working on the area between 30 and 40 kPa and 400-2400rpm trying to get a stable idle for warmup. I took the approach of richening the VE table and leaving the open loop table alone. At this point the mixture is still just a little too lean to support a steady idle but I have increased the values in those cells to 2.8000 which your comments should lead me to believe would be way too rich. This points to there being another problem somewhere, the question is, where?

I have checked and double checked the injector flow rate. I flow tested the injectors myself on my own flow bench and they range in a tight cluster around 35 lbs at 40psi. I used an online calculator to convert that to 4.4 gm/sec and entered that value.

Can you think of any other thing that could possibly cause this discrepancy? I'd sure appreciate any leads you can give me.

Jim

[brian617]

Cylinder Volume.
Injector offsets.
Returnless VS Vacuum Ref. (Flow rate vs KPA)

[Jim Blackwood]

Please see if these figures look like they are within reason. I only changed the cylinder volume.

Cylinder volume is 712cc
EOIT Boundary: 585
EOIT: 230-500
Inj PW voltage adj: .06-9.68
Inj voltage correction: 1
Min PW: 1.277
small pulse threshold: 3.997

Couldn't find the returnless/vac reference but my fuel system uses a return and is referenced to MAP.

Thanks,

Jim

[kur4o]

The way you set the inj flow rate, requires constant 60psi fuel pressure.
Step 1 to fix this, remove the map reference to the fuel pressure regulator.
or Make inj flow rate constant across all ranges and leave the map reference.

I am not quite sure how the ve works in ls1 but it must have some max value that will be close to 100% ve. Looking at the values at the right bottom of the ve table will give you the max value the pcm can use. If you max the ve table the only way to tune will be increase the cylinder volume scalar and than rework the ve table.

Dont forget that all of this ve calculations are represented as airflow to pcm in g/s. Monitoring that value will give you a clue if you manage to change the values or they are capped.

Don`t tune warm up, there are some other adders for that purpose. Tuning ve table must be done on fully warmed engine with all the others turned off.

[brian617]

Couldn't find the returnless/vac reference but my fuel system uses a return and is referenced to MAP.

Thanks,

Jim

"Flow rate VS KPA" is how its listed in HP Tuners, not sure what it will be named in your XDF. Also VE table should be a whole number from 0-100 for instance the file I'm looking at ranges from 17-97

What injectors are you using?

[Jim Blackwood]

At the risk of sounding obtuse, how do you ever tune the ve table if you can't idle the engine? Seems to be a necessary first step for getting it up to operating temperature, I don't see an easy way around that. Any suggestions for initial cold enrichment settings and where to make them? I'm all ears, I'd love to hear your suggestions and will try them out straight away.

My injector flow rate/kPa chart only varies by .22 gm/s but I have changed it to 4.4 across all values. I can't see that making much difference, certainly not enough to fix my lean condition but that's done.

My FPR has a hose that connects to the intake plenum so that it maintains 40psi in reference to the intake regardless of vacuum or boost conditions. There is no other modifier to the fuel pressure. This is consistent with most return-type fueling systems and is completely independent of the engine controller.

The max entered value in my VE table is 2.3980 which is at 4800 rpm and 170 kPa. At 100 it is 2.3227@4400 rpm. I am also accustomed to using values from 1-100 but that doesn't appear to be used here so I'm trying to adapt. As a multiplier, 1 would equal unity in the formula, (does not change it) which also uses the injector flow rate and other factors. For my engine to require at least a 3x multiplier in order to idle suggests that there is an unbalance elsewhere in the formula. Not the VE table, not the injector flow rate. Some other factor has to be off by and be dividing the formula by approximately 3 or more. I need to find out and fix that.

Does anyone have the actual fuel calculation formula?

Jim

[brian617]

My injector flow rate/kPa chart only varies by .22 gm/s but I have changed it to 4.4 across all values. I can't see that making much difference, certainly not enough to fix my lean condition but that's done.

My FPR has a hose that connects to the intake plenum so that it maintains 40psi in reference to the intake regardless of vacuum or boost conditions. There is no other modifier to the fuel pressure. This is consistent with most return-type fueling systems and is completely independent of the engine controller.



Jim

With vacuum ref the "Flow rate vs KPA" should be a fixed number across the table which reflects the flow rate of your injector @ xx psi. I believe that's 45psi in the LS world? Some correct me if wrong.

Example, a 01 Silverado with a 5.3 engine has a value of 25.1 across the table.

[kur4o]

I suggest you run fixed fuel pressure at 60psi. It is also very likely that the fuel flow constant is higher than actual. The injectors might flow less than you thought.

Start lowering the values at the fuel flow table by 10% and see how it goes. When you remove the map reference the table should take that into account.

Your best bet is to start with some ls1 stock injectors with good stock data, and make initial tuning with them. That way a big unknown is removed from the equation.

The % of ve is derived by the ve table values and cylinder volume. If anyone knows the formula I can add it to the xdf. I will play with efi live to see if I can rip the conversion they used.


Ls1 intake is with equal length runners and there is no need for individual cyl corrections. It could be some of the cylinders running leaner than others.


The xdf tables looks weird with 170kpa tables. I wouldn`t trust them too much. You have 1 bar map that can`t read 170kpa or there is some scaling with 2 bar map used.

A complete write down of your setup might be needed with the origin of the xdf and bin.

[Jim Blackwood]

The injector flow rate of the stock '01 Silverado is 3.18 gm/sec. I flowed my injectors at 35lb/hr (4.4gm/sec) @ 40psi. Actual was 37.7 and below saturation flow values were as expected. I could jack up the fuel pressure but that seems like an artificial solution, especially when it was running fine with that fuel pressure and comparable settings on the other controller. (MS2)

If anyone can find out the actual formula it should be possible to pinpoint the problem using that. Until then I guess I can fudge the thing by lowering the injector flow value to offset whatever is causing the problem. It's funny in a way, that was my first impulse. Going full circle here so maybe that's a sign.

About that MAP value, yes I am using a 2 bar sensor. I changed the multiplier to account for it and rescaled most of the tables that use MAP. May have missed one here or there but I don't see why that shouldn't work just fine.

Logic would seem to suggest that if the VE has to be tripled to get enough fuel, then the Injector flow number should be divided by 3 to achieve a comparable result. That seems like a lot but it won't hurt me to try it.

Jim

[brian617]

According to this page https://www.psiconversion.com/tech/ls_guide/fuel_injector.html LM7 injectors basic 5.3 injectors flow 24.8 lbs per hour @ 58 psi. That's why the "Flow rate vs KPA" table has a value of 25.1 across the board. Again we don't know what injector you are using but an LM7 injector flowing 24.8lbs/hr would be 3.12grams/sec. That table has to reflect the flow rate of your injector at 58psi.

So your injector 35lbs/hr @ 40psi would be 42lbs/hr @ 58psi and the table value should be 42

However if you aren't running 58psi with the vacuum hose off the reg, then your'e going to have a lot of injector data to fudge.

[kur4o]

That 2bar map and scaling complicates things further. There is tons of map referenced tables that are not defined in the xdf.

I am sure your inj flow tables is off the chart. Vacuum is derived from map and baro, so it is unclear what values are you getting. It is too bad that it might end with tail chasing tuning. The ve table also is capped well above 100%. Try increasing substantially cylinder volume constant and play with inj flow rate. You might find the sweet spot at the end.

With boost 40psi FP is well too low. I would run constant 60psi if the injectors can handle it.

[kur4o]

Someone good at math can figure the conversion of ve to % here are some raw values in hex converted to % according to efi program.

$a8e7 ve with $5b23 cyl volume constant equals to 343.54% ve
$7a67 ve with $5b23 cyl volume =266.24%

[Jim Blackwood]

Probably the biggest clue to what is going on here is that this is no small discrepancy. That was demonstrated by today's testing. Unlike possible or at least theoretical limitations in the VE table values that may have prevented efforts to find the range, there is no limitation in reducing the given injector flow rate. Of necessity the flow rate has to be a divisor. The larger the number, the shorter the resulting injector pulse. We know this Empirically because a larger injector will deliver the same volume of fuel with a shorter pulse. Therefore as the number approaches zero the pulse width approaches infinity.

To get to the point, there was one entire order of magnitude (x10) between the flow setting required to create an injector pulse long enough to run stoich at idle, and the beginning injector flow rate in grams per second. The ending test rate was 0.46 g/s and the starting point was 4.4 g/s.

What this means is that for some reason there is a 10x multiplier that has dropped out of the fuel formula. I'm honestly having a bit of difficulty figuring out what that could be. Not fuel pressure, I'd have to be running 400 psi to make that much difference. (Testable by checking the injector PW with a scope but just the magnitude says that isn't it, to say nothing of the fact that this engine ran fine on those injectors with that pressure before the controllers were changed.) Differences in MAP values would never be on that size of a scale either so pointing at the 2 bar MAP sensor isn't productive either. The "some here some there" theory MIGHT have some promise, but for 2 errors we'd have to see at the very least a threefold (x3) error IN EACH ONE to even have a chance to make that theory work. Fuel pressure x MAP still isn't anywhere close to enough. Adders? Nope, we have to have a multiplier here to explain it. There is no adder that brings in that much extra fuel. Not for a street driven engine.

All I can think of that's left is cylinder volume, maybe I'll play with that tomorrow. But it seems like there has to be another factor somewhere that is missing. A small table that's zero'd out or something. That seems like the most probable cause.

Jim

[kur4o]

I am almost sure the issue is within the 2bar map and the scaling. There is too many variables that are not accounted for. Not a single small table.
Something must be capped in the equation and than a default built in value is used.
Anyway you will never get good enough fuel flow data since vacuum is converted by ??? and the result is used at the table lookup. I am not sure but there might be a switch what to use for the table lookup map or vacuum.

Start increasing the cylinder volume with correct inj data and see how it goes.

1000% in fuel flow equals to huge airflow error. You are missing 1 decimal point in the airflow. And that airflow is used everywhere for running the engine including spark.

[Jim Blackwood]

OK, I ordered a new 1 bar sensor. When it comes in I will try it like that. As long as I stay out of boost it should work just like if it wasn't supercharged. Then if I get that working right will be soon enough to worry about the 2 bar. Anyway at this point I really hope you are right. As likely to be that as anything else.

Jim

[Jim Blackwood]

You know, I might have an idea what it could be. There is a scalar for the MAP sensor. (C6301) When I modded the tune I changed the scalar. I doubled the value. But if I went the wrong way that could easily be a fourfold difference in the resulting value. It doesn't seem like enough, but it sure could be a big part of it. Then too, the Camaro tune I got from Scott had a value of 94 where the Silverado had 73 which seems like a significant difference. I used a value of 188. I think I'll set it to 35 and see what happens. I also changed the sensor offset from 10 to 5. I'm not sure what effect that will have but if doubling the two values is bad maybe halving them will be good.

Jim

[Jim Blackwood]

Well I do have some new information. A little about the MAP scaler but first, I've found the question raised again about the handling of boost. There is an opinion that the fueling algorithm will not handle values in the MAP axis of the VE table above 105 kPa, and this is the reason for the creation of boost tables in the custom OS's used on non-OEM boosted applications. This may well be, I don't know. If true it means my tables are essentially useless, also meaning I need to start shopping for a custom OS. So I guess that would be the next step and I should probably start a new thread and can likely wrap this one up. So back to the MAP.

The MAP scaler is set so that the ECM reads the correct values for MAP depending on the MAP sensor used. Basically, the scalar (B3601) sets the range and the offset (B3602) sets the position. A barometric pressure of around 30.2 is pretty generic and converts to 102 kPa. So, key on engine off, the MAP will read static baro and it should output about 102 on your datalog whether it is a 1, 2 or 3 bar sensor. Because the higher boost sensors have to measure a wider range they have to use a condensed scale. The same 0-5v output in every case. The scaler sets the range. Typical values are around 90 for 1 bar, around 190 for 2 bar, and I think about 280 for 3 bar but I'm not sure since that wasn't my focus. The scalar is adjusted so that let's say you have the ability to pull down to 30 and pressurize to 180 just as an example then you have a range of 150 kPa (probably requires a decent vacuum pump, compressor, and pressure regulator to do accurately) and you can verify that with your boost gage. Or you can run your engine and record the high and low numbers and compare that to your datalog. (probably the easiest) If your spread by gage is 150 and your spread by datalog is also 150, even if the numbers don't match then your scaler is right. If not, adjust it so they are.

Next adjust the offset so the numbers line up as close as possible at the bottom, top, and most importantly static baro point in the range. It won't be absolutely exact but should be very close at those three points. You now have a properly calibrated MAP sensor. The offset should be somewhere in the vicinity of 10 but might be more with the 3 bar. You are matching two curved lines. The one parameter you can't change is the radius of the curve but since both the sensors and the ECM are GM they have already matched that for you and it should be very close indeed.

In my case, I had values of 188 and 20 entered which was very close on the range but probably off by 10 on the position (offset). That should be close enough to run reasonably well. My problems are elsewhere and it makes a lot of sense at this point to start over with a COS. I've pretty much exhausted all other options. Hope I haven't exhausted you guys in the process.

Jim