$_ _ <----- Help

[tjerica1201]

I've been reading through all the diffrent forums for a few weeks now trying to learn the trade. I havnt been able to find any threads explaining the diffrence between all the diffrent mask and how you are supposed to know what which one to use. I'm guessing that it will be based off of which ECU or PROM you are using??

[steveo]

you have an ecm (like a 7747)

that ecm has software written for it, identified as a 'mask' (like $8D). different masks are completely different programs, with tables and constants in different locations. some ECMs only have a single mask written for them, some have many available.

each mask has various factory calibrations, with a 4 letter code (like AMYB). that's basically 'the tune'...

[tjerica1201]

Anyway you can dumb it down a little more? I'm still in the early stages of learning everything. No detail is to small.

[1project2many]

steveo provided a great description of how ecm, mask, and calibration are related. If you provide some details about what you're working on or a specific question maybe we can provide specific information to help.

from steveo, in another thread:

i can make it simpler too, i did tech support for a while for people that couldn't find the 'on' button on their computer. you just have to tell me how simple to make it....
That's good stuff. Ever help a 12:00 flasher? You know, the guy who's digital clocks are always blinking 12:00? Dangerous people there, and likely to burn up an hour complaining about "newfangled contraptions."

[jim_in_dorris]

:laugh: Yep, Ever removed a PBJ from a CD drive?

[tjerica1201]

94 suburban. I put a high press fuel pump, tbi spacer, and injector spacer and now it's idles like crap when it first starts up. After about 15 seconds or so it finds it's sweet spot and runs great. Exhaust smells foul all the time now too. I don't know if tuning will help, but it's a great excuse to learn the trade.

i guess my question here would be "how do I know what mask to use?"

[fastacton]

Why did you go with the high pressure fuel pump? It sounds like you might have too much fuel pressure. I'd put a gauge on it and make sure that you don't have more pump than your return line can handle.

[buddrow]

94 suburban. I put a high press fuel pump, tbi spacer, and injector spacer and now it's idles like crap when it first starts up. After about 15 seconds or so it finds it's sweet spot and runs great. Exhaust smells foul all the time now too. I don't know if tuning will help, but it's a great excuse to learn the trade.

i guess my question here would be "how do I know what mask to use?"

For starters if the engine is stock you likely have more fuel pressure than your engine needs which explains the rich smell. After the ecm enters closed loop it tries to compensate for what it sees as too much fuel and "lines out" the fuel to the best of its ability giving you the "sweet spot" you speak of.

The mask required is based on the ecm you have in your 'burb. You're probably going to need the $OD mask for your truck as you are likely running a 7427 ecm. You are going to have to modify the .bin to compensate for the changes to the fuel system. Do you have any tuning equipment? Laptop, Tunerpro, aldl cable for viewing/logging data and a chip burner are all things you should have to tune.

Buddrow

[1project2many]

The mask required is based on the ecm you have in your 'burb. You're probably going to need the $OD mask for your truck as you are likely running a 7427 ecm.
Right. Get the ecm / pcm part number or the "scan id" with tunerpro and we can help you get on the right track. Trying to learn about all ecms and all tuning at once is much more challenging that just working on your truck.



Yep, Ever removed a PBJ from a CD drive?

:laugh:

No, but I have young children. The odds aren't in my favor.

[kevinvinv]

Is your 94 Suburban a 350 or a 454?

If you don't have the answers you wanted yet… maybe this will help.

Pull out the ECM (behind the glove box on top of the heater core- an aluminum box)
On the top of the ECM is a sticker that will have a couple numbers on it… one number will be like16196395 which is the P/N of the ECM itself. This is the one I have in my 94 Blazer.
There will also be a 4 digit code called a broadcast code. Mine is BHMZ which is what they stuck in California trucks.

Both of these numbers are important.

If you can get the BCC you then can find a bin file online somewhere for that BCC. If it is BHMZ, I can send you mine. If not, then just search this forum or general google for that string of letters.

If you can find a bin file (which is an image of the ROM (calibration) inside your aluminum box) - then download it and load it into a hex editor. Find byte number (hex) 4008 and that is the "mask_id"

I am betting if you have the 350 then it is 0D and if you have the 454 it is 0E

I am a beginner too and these are the things that I have learned in the last few weeks on this forum.

A couple other things … did you replace your injectors or are you using the stock ones? I first wanted NEW injectors and got some from NAPA. I can tell you this, the NAPA injectors for a 94 454 are NOT THE RIGHT injectors. Same with the ones from Advance Auto. These trucks came with a high pressure fuel system and I don't think some of the aftermarket companies know about that… I only had luck when I bought refurrbed GM injectors.

[tjerica1201]

I went with a high pressure fuel pump because mine went out and since Im a guy, had to go with the bigger pump. I know I know, "its a stock motor, why would you do that". Well I'm afraid I'm at a loss of a better explanation than "why not". I had worries about the pump being too big and dumping too much fuel as well. So I put the gauge and manual press regulator from cfm tech. I'm showing a consistent 14, which may be a little high, what do you guys think?

As as far as my ecu goes, i had it out during the fuel pump fiasco but do not recall which one it was exactly. 7427 does stand out tho. Don't know about the other four letters tho. I have downloaded turner pro and have downloaded some different bins and played around with them a little bit. That's as far as I've gotten.

It is indeed a 350. I am using stock injectors. I took them to a guy and had them bench tested and rebuilt. I was going to go with new ones but heard some bad things about them and didn't want to take the risk.

I will pull the ecu and get the the numbers and such off it and let you guys know.

[tjerica1201]

It's a 7427 BJLH.

[1project2many]

i guess my question here would be "how do I know what mask to use?"
I just realized I might have misinterpreted this question. In some cases guys are mixing and matching mask and ecm, or they're talking about using a different mask. If you're asking about why this is happening, it's usually about getting specific features or improved performance over the original ecm / code. In the case of the 7427, that's a fairly good pcm with a plenty of capability for a stock or mild engine so you really don't need to change code masks from what you currently have.


I'm showing a consistent 14, which may be a little high, what do you guys think?
Stock fuel pressure range for these vehicles is 9-13 psi. Usually they were on the low side... 10-ish from the factory. A little more pressure is a good thing if you have the means to adjust the calibration but right now it's causing your truck to run rich. With a laptop and a chip burner you could adjust the fuel injector size in the chip to a *slightly* smaller value to return the truck to stock performance. The alternative is to adjust the fuel pressure back down to the 10-11 psi range. You might be able to modify the stock regulator, or you might want to buy an adjustable regulator, but either way you'll likely end up pulling the throttle body off to do the job.

IMO getting the tools and knowledge to do tuning can produce the best gains long term, but it's a bunch of work and money if all you want is for the truck to run like stock again. Your calibration is $0D mask and this thread has the tools to work with it.
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?303-16197427-PCM-Information-0D

HTH

[kevinvinv]

I had to edit this post… b/c actually I have a question myself on this. Why do we think a higher pressure pump would really hurt anyway? It is all about the regulator is it not? I've actually put in high pressure pumps (maybe not as high as yours) into TBI systems and had no problems… since the regulator reduces the pressure anyway. So my opinion is to just measure the pressure and dial down your regulator back to stock pressure and see how it is.

I have had problems TWICE now with rebuilt injectors… it is very frustrating. Next time I will rebuild them myself so at least I know what I am getting. Once you get your pressure back to normal - if it still doesn't run right- I suggest not assuming your injectors are solid… hopefully they are fine but if things still don't run right… keep that it in the back of your mind.

Out of curiosity, is the adjustable regulator you got one from a Marine application? That is what I got (possibly from the same place)… he offered a great price and it is cool to be stock GM still. Just a bit of a pain to adjust...

[1project2many]

Why do we think a higher pressure pump would really hurt anyway?

Well, all theory aside, there is this:
1) truck runs fine
2) replace fuel pump with non stock variety
3) truck does not run fine.

Practically speaking a "high pressure pump" in this case is a different design pump capable of producing substantially more pressure. If the replacement pump also moves a higher volume of fuel than the original pump the stock pressure regulator adjustment might actually create higher pressure. As pressure increases to 14 psi, the original pump efficiency drops quickly and the volume of fuel moved also drops. This doesn't happen with the "high pressure" pump and sometimes the pressure adjustment might need changing. I didn't catch the OP mentioning the "manual regulator" but if it's a second, add on regulator then it is not appropriate to run with the factory part still installed. 14 psi is fine if the OP decides to adjust the calibration.

[fastacton]

Why do we think a higher pressure pump would really hurt anyway? It is all about the regulator is it not?

It's not just the regulator, but also the entire return side of the fuel system. I've found that I can get away with using a high volume/pressure pump as long as I have at least a 5/16" return line with no restrictions. If it's a 1/4" return line (like on an early Mustang tank with an EFI sending unit), then the restriction is too much for a low pressure TBI fuel system, yet is fine with a higher pressure multiport system.

[jim_in_dorris]

If it really is set at 14psi (not all pressure gauges are accurate) then something else is wrong, however like 1 project said, the only thing changed was the fuel pump ( mine is a 38psi tpi pump that delivers a solid 13 at the throttle body). I would start to data log to look at what the computer thinks your fueling looks like. Guessing doesn't work. 14 psi versus a stock delivery of about 11 psi is a 27 % increase in fuel. Your fuel maps would be way off. Over time it will lean out, however I would turn down your fuel pressure to about 12 and see how that responds.

[steveo]

14 psi versus a stock delivery of about 11 psi is a 27 % increase in fuel.

no, it's not. the change in injector flow due to pressure change is not a percentage change. 1% more pressure is NOT 1% more injector flow, it uses square root. going from 40lb of flow @ 11psi and moving to 14psi bumps you to 45lb of flow. that's more like 12%, not 27%.

[jim_in_dorris]

I realized that later steveo, but 12% more fuel will also drive it rich. 128 BLM + 12% more fuel should drive you to 113 BLM, that is fairly rich. It will correct itself over time, but just turn down the pressuire and solve it quickly. (TBI 350- injectors are 61 # injectors not 40, but the difference isn't much 12.7% as opposed to 12%). Still I would just turn down the pressure, it would be the easiest fix. Then again, I would data log instead of guessing.

[tjerica1201]

Kevin, while doing the research on the pressure manual adjustment screw conversion, I do remember coming across a company making the same thing on a marine application. I got my whole setup through rv machine (that's not recreational vehicle, guys name is Roy something). He gets the kits (I later found out) though cfm tech. Stuff seems to be pretty well made, I'd reccomend them.

As far as the rough start idle, I have resolved the issue. You guys all had me convinced that 14 psi was just too high. So I went out there to adjust it and noticed that SOMEONE (or something...) must have disconnected the vacuum line coming out the back of the throttle body. I know I wouldn't make such a rookie mistake as to not reconnect it in the first place....

Anywho, problem is solved and it runs fine on 14 psi. Thanks for all the help. My original question was answered. I will keep focused on MY stuff and worry about learning about all the other things until the situations present themselves.

TJ

[tjerica1201]

In some cases guys are mixing and matching mask and ecm, or they're talking about using a different mask. If you're asking about why this is happening, it's usually about getting specific features or improved performance over the original ecm

HTH

I still don't understand what a mask is exactly. I think 1projects comment here is leading to helping me understand this. What kind of specific features or performance are you referring to? Do diffrent masks provide you with a bunch of diffrent tables you can make adjustments too?

[kevinvinv]

Kevin, while doing the research on the pressure manual adjustment screw conversion, I do remember coming across a company making the same thing on a marine application. I got my whole setup through rv machine (that's not recreational vehicle, guys name is Roy something). He gets the kits (I later found out) though cfm tech. Stuff seems to be pretty well made, I'd reccomend them.

As far as the rough start idle, I have resolved the issue. You guys all had me convinced that 14 psi was just too high. So I went out there to adjust it and noticed that SOMEONE (or something...) must have disconnected the vacuum line coming out the back of the throttle body. I know I wouldn't make such a rookie mistake as to not reconnect it in the first place....

Anywho, problem is solved and it runs fine on 14 psi. Thanks for all the help. My original question was answered. I will keep focused on MY stuff and worry about learning about all the other things until the situations present themselves.

TJ


Glad you found a simple fix!!! The adjustable fuel pressure regulator I got is actually STOCK GM. No modifications and no special anything- it is just a stock adjustable FPR from a GM Marine application. It even has a little spout on it to dump fuel into the TBI instead of on the ground if the regulator diaphragm leaks. These things are a little rare I guess but still way cheaper than any custom AFPR's I've seen AND… they are factory GM :) Of course YMMV. :)

[tjerica1201]

Hum...that's pretty cool. Wish I'd know about this thing. Sounds pretty cool. I'm all about keeping original equipment...unless it's a performance of course. It makes sense that it dumps leaked fuel into the tbi for marine applications. Beats dumping it into the boat, or the water for that matter.

[steveo]

marine mechanical pumps do that too, vac line from the fuel pump diaphram to suck leaked fuel into the intake.


I still don't understand what a mask is exactly. I think 1projects comment here is leading to helping me understand this. What kind of specific features or performance are you referring to? Do diffrent masks provide you with a bunch of diffrent tables you can make adjustments too?

in terms of tunerpro, you can think of a 'mask' as a specification of where the various tables/constants/switches in your bin file (the calibration that runs your ECM) are located, and how they work.

so yes. different masks provide different tables.

the mask tunerpro is editing must match the mask that your ECM's software is using, or horrible things may happen (like you'll edit a chunk of code when you think you're editing your idle speed target)

does that make more sense?

[1project2many]

When I was young, we used to take standardized tests. Maybe you've done the same thing. You read a question and several answers then on a separate page you fill in a circle that represents your chosen answer. Back then the teacher would grade the test by placing a special master sheet over your answer page. The teacher's sheet had holes for all the right answers. If your answer didn't have the circle filled in where the master sheet had a hole, it was wrong.

http://wpadmin.prowesstestprep.com/wp-content/uploads/2013/06/iStock_000012277417XSmall.jpg


The "mask" is a code to identify where the variables are laid out in the calibration. You can think of it like the test master sheet. The calibration is like an answer sheet. If you pick the wrong mask for the calibration, nothing lines up and everything is wrong. The mask doesn't mean anything performance wise. It's just a way to identify a master sheet and the calibrations that match it. Tuning software definition files are written to match a particular mask. Definition files for a one mask will not give desired results with a different mask. The tuning software will allow you to change the variables, but the variable's function will not match what is in the definition. The software might say you're changing cylinder displacement, but really you're changing spark advance reference angle.

In most cases the only reason to know your code mask is so your tuning software "fits" your calibration. But sometimes people have some specific requirements that will need features not offered in all calibrations. They will need to pick a specific mask that does what they want. For example, someone has a turbo and wants the ecm to have wastegate control and the ability to back off boost and add fuel if knock can't be stopped with spark reduction. They need code written just for this. The community has figured out that those features were available in factory code from the turbo Sunbird and Syclone, identified as $58, and in code from the turbo Grand Prix, identified as $8F. This would be a case where picking a mask is based on performance.

[tjerica1201]

Ok I'm finally starting to understand. So let's try a for instance. My ecu has a specific program written for it that reads the mask $OD. Let's say I build a 383 for it and the turbo it. Does that mean that I need to get a different ecu that can read the mask that has all the tables and such to run this setup? Or can you just reprogram them to read whatever mask you want to use. Or am I still completely lost??

[steveo]

lets describe it another way.

i write a program for your ECM that makes your car run.

keep in mind a particular ECM can run various different programs that are designed for that hardware.

the program has instructions like

- look up information in table x to squirt fuel.
- look up information in table y to adjust spark timing.
- check a bit z to see if.. i dunno.. your idle increases when cold.

the MASK defines the locations of where x y and z are located in the bin file, how they work, and how to view that data so it makes sense, so you can tune it.

a slightly different program that uses the exact same tables could use the same mask.

if a drastically different program uses different tables in different places, that'd be a different mask.

does that make more sense?

[1project2many]

Please don't get hung up on this. The importance of this value to a beginner is small. Match the ID of your chip to the tuning software, definition file, and ALDL definition and you're ready to start learning how to tune.


My ecu has a specific program written for it that reads the mask $OD. Let's say I build a 383 for it and the turbo it. Does that mean that I need to get a different ecu that can read the mask that has all the tables and such to run this setup? Or can you just reprogram them to read whatever mask you want to use. Or am I still completely lost??

That means you'll want to consider the tradeoffs between giving up a highly capable pcm which can control electronic transmissions but does not have a factory program for a turbocharger against the compromises you would make switching to an older ecm which cannot control the electronic transmission but has code written to work with the load generated boost of a turbocharger. You don't need to know anything about the mask, other than what the ID's are for the two most common versions of factory code designed for a turbo.

And to rephrase your question in a more accurate manner using the context generally applied to GM ECM's:
"My 16197427 PCM has a specific program written for it. The one currently in use is $0D. Let's say I build a 383 and then turbo it. Does that mean that I need to get a different ecm to use $58? Or can I run $58 on the 7427?"

Ans: $58 will not run correctly on the 7427 pcm. The program expects inputs and outputs to be at different addresses than that pcm uses. Additionally, $58 cannot control an electronic transmission so you will lose that feature. Your options are to use a piggyback ecm configuration, where the 7427 controls the trans and a different ecm running $58 controls the engine, or to use the 7427 code with a 2 BAR MAP & scaling MAP readings and doing your best to tune around the lack of turbo specific code, or to get really hard core and learn to write your own code for the 7427.

[kevinvinv]

Moates.net seems to call the mask "the operating system" -- from my understanding this is not the best term but it did help me understand what "mask_id" meant just a little bit.

I would say two things (based on my novice understanding)…
1) The EPROM contains a bunch of tables, the mask_id is a way of keeping track of which tables it contains and WHERE they are located in the EPROM
2) The EPROM ALSO contains actual microprocessor code (a program that uses the data in the tables). The code in different "mask_id's" is different.

So the mask_id is like a "model number" for the data in the EPROM… which is both code and tables.

[1project2many]

Moates.net seems to call the mask "the operating system" -- from my understanding this is not the best term but it did help me understand what "mask_id" meant just a little bit.

I would say two things (based on my novice understanding)…
1) The EPROM contains a bunch of tables, the mask_id is a way of keeping track of which tables it contains and WHERE they are located in the EPROM
Correct.


2) The EPROM ALSO contains actual microprocessor code (a program that uses the data in the tables). The code in different "mask_id's" is different.
Correct, although there is no requirement that the code be different. Custom code with different functions could also use the same tables and the same locations.



So the mask_id is like a "model number" for the data in the EPROM… which is both code and tables.
This is not an unreasonable association.