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??
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'...
Anyway you can dumb it down a little more? I'm still in the early stages of learning everything. No detail is to small.
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:
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."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....
Yep, Ever removed a PBJ from a CD drive?
Square body stepsides forever!!!
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?"
Last edited by tjerica1201; 08-03-2014 at 06:04 PM.
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.
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.Originally Posted by tjerica1201
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
If it don't fit force it, if it don't force fit f&%@ it!
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.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.
Yep, Ever removed a PBJ from a CD drive?
No, but I have young children. The odds aren't in my favor.
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.
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.
It's a 7427 BJLH.
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 guess my question here would be "how do I know what mask to use?"
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.I'm showing a consistent 14, which may be a little high, what do you guys think?
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-Inj...Information-0D
HTH
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...
Last edited by kevinvinv; 08-04-2014 at 04:08 PM. Reason: had un-thought-out comments about the fuel pump...
Well, all theory aside, there is this:Why do we think a higher pressure pump would really hurt anyway?
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.
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