well I have a scanmaster and a knock gauge(which usually does nothing),I had all but tuned all my knock in thrd out then the weather cooled off and I put my 265/50's on the back,Now I start getting knock in third gear after I have been driving it around a bit.did not know if it was cooler air,tire size...?My blm's are always around 138-146 atWOT,also my o2 with the knock are usually 790-820,According to the scanmaster numbers it is not running lean and my fuel pressure is around 45psi.My boost has been turned down to around 15,usaully I am not getting max boost when the knock starts,only 10psi last night.I just don't know if the intercooler heats up or maybe my coolant temps are too low(usually around 165-175)
scanmaster knock numbers
- Thread starter gnturbo
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charlloots
SMO-CUM
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- Aug 1, 2002
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you might have some bad gas
try a can of 104 octane boost
just a thought
try a can of 104 octane boostjust a thought
well I have no clue what is up.I have fresh 36lb injectors,good 93 octane fuel(808/no knock)but my blms are still 138-152 at WOT.I have fuel pressure set at 44psi if it were not for the int/blm numbers I would not even give it a thought.Car is running real well
To add a little to TurboDave's answer.
It sounds perfectly normal. The colder air will make the car run leaner...more oxygen. This always happens when the air turns cold. Your car may "learn in" to it. The high BLM's at WOT are not really telling you much...you have to watch the O2 millivolts since at WOT no fueling changes are being made (open loop). The WOT BLM values are actually taken from another "learned" cell.
You might notice that your INT's are high too. The high INT's will eventually pull down your BLM's, but the range your in is just fine. 128 is the target, but as long as the BLM is not bottomed or topped out the computer is still controlling the mixture.
Note that some chips DO lock the BLM numbers at 128 for WOT. This is to help you at the track so when you make a change in Fuel Pressure the computer won't compensate and learn in a new cruise BLM that negates the FP change. Not all chips do this.
You'll probably have to just turn down the boost a bit or watch the knock retard real careful when you're at WOT. At the track most guys will tune for zero KR and try to keep the o2's around .780. For street tune I would go with 02's closer to .800-.820 just to be safe....no use running it on the ragged edge all the time.
Good Luck,
John
It sounds perfectly normal. The colder air will make the car run leaner...more oxygen. This always happens when the air turns cold. Your car may "learn in" to it. The high BLM's at WOT are not really telling you much...you have to watch the O2 millivolts since at WOT no fueling changes are being made (open loop). The WOT BLM values are actually taken from another "learned" cell.
You might notice that your INT's are high too. The high INT's will eventually pull down your BLM's, but the range your in is just fine. 128 is the target, but as long as the BLM is not bottomed or topped out the computer is still controlling the mixture.
Note that some chips DO lock the BLM numbers at 128 for WOT. This is to help you at the track so when you make a change in Fuel Pressure the computer won't compensate and learn in a new cruise BLM that negates the FP change. Not all chips do this.
You'll probably have to just turn down the boost a bit or watch the knock retard real careful when you're at WOT. At the track most guys will tune for zero KR and try to keep the o2's around .780. For street tune I would go with 02's closer to .800-.820 just to be safe....no use running it on the ragged edge all the time.
Good Luck,
John
OK...so then TR's do go into open loop at WOT?
They don't use a form of closed loop called PE, or primary enrichment like an LT1? I figured GM has been doing this the same way since way back when...maybe not.
So then I guess blm's really don't mean a thing at WOT.
They don't use a form of closed loop called PE, or primary enrichment like an LT1? I figured GM has been doing this the same way since way back when...maybe not.
So then I guess blm's really don't mean a thing at WOT.
Well, no, not exactly. They don't go into open loop at WOT. It's just that BLM "learning" is disabled so they cant change during a WOT run, and yes, we do us PE (power enrichment). There are several PE tables that are accessed when WOT conditions are met.
You have to remember the WOT BLM numbers are accessed from cell 15, and it doesn't take anywhere near WOT for cell 15 to be accessed. As a matter of fact, if you had Direct Scan, you'd see that just pulling away from a stop sign or stop light with normal traffic will get you into that cell.
TurboDave - Does the GN ECM have cell 18 available as an alternate WOT cell if certain conditions aren't met that would force it to use 15? If the car is seeing a constantly rich or lean condition, it could go to cell 18 and the blm's could cause the car to go rich or lean. Rich would be fine...lean would be bad.
I don't have directscan....so I can't monitor things like that.
If the car can go into cell 18, at least on an LT1, it could take the last blm and apply that and since the computer isn't using O2 signal as a way to adjust fueling...then those lean blm's @ WOT in cell 18 could be very bad. This possible?
I just want to know that gnturbo (or anyone else) couldn't potentially have that same problem w/ his blm's showing lean (although the computer is/should be correcting for it).
Also, inside the computer....can you change the rpm and map that each cell would be called for? That way you'd be using more of the cells and not hitting 15 so easily? Or do these cars really not have a high rpm/high map cell since they're turbocharged?
Thanks a bunch!
I don't have directscan....so I can't monitor things like that.
If the car can go into cell 18, at least on an LT1, it could take the last blm and apply that and since the computer isn't using O2 signal as a way to adjust fueling...then those lean blm's @ WOT in cell 18 could be very bad. This possible?
I just want to know that gnturbo (or anyone else) couldn't potentially have that same problem w/ his blm's showing lean (although the computer is/should be correcting for it).
Also, inside the computer....can you change the rpm and map that each cell would be called for? That way you'd be using more of the cells and not hitting 15 so easily? Or do these cars really not have a high rpm/high map cell since they're turbocharged?
Thanks a bunch!
