maft cutoff problem and knocking

[91-gsx]

o i get you. it sounds good so far. but after i lower the boost and get rid of fuel cut, what if i want to turn the boost up more and their is fuel cut, lets say i got bigger injectors like 660cc like you said and rewired a 190lph becuase i do not have the money for a 255lph and a fpr, 255 and 190 are same cost but with 255 you need fpr. how would i get rid of fuel cut if i want to up the boost. this is later ofcourse.

 

[sweet97]

Simple. The larger injectors would be more suited to the GM MAF which is flowing so much AIR that you cannot make the adjustments you need without either getting massive knock due to running lean which pulls timing or trying to richen the mix and hiting fuel cut. Since the 550/650cc inj's are not far from 450cc inj's you would set the base and then not need big adjustments from a "0" set MID or WOT. Maybe 1 or 2 clicks from "0" and you would have those larger inectors matched to the amount of air you are flowing. Really they are closely matched as is. You will fine tune for more power with the translator.
You won't have to lean those size inectors a lot to match the air flow so no massive timing icreases.You will not have to run them much richer so no fuel cut. You will be letting the ECU "see" an amount of air that it was designed to see yet you will have a good A/F mixture. A/F =air fuelmixture, not too lean or rich.
Now I have an EPROM ECU so I had a chip burned which compensated for the 650's so that they appear as 450cc inj's to the ECU making my tuning easier, even smaller adjustments to trick the ecu to how much air is coming in because it has been reprogrammed to think the 650's are really 450's. Like I said earlier you may have an EPROM ECU from the factory. My '91 parts car did.
Try setting your base on "0" and then see what happens with the MID and WOT on zero's. Do you have your base set for 450's which is a "2"? A base of "0" will make it richer across the board and may allow you to make smaller adjustments on WOT allowing you to run a bit more fuel without the timing or cut issues. Mark

 

[91-gsx]

hey thanks for all of the help, i will try that tommorow.
it just might work

 

[91-gsx]

so far i have changed the spark plugs and fuel filter and the car feels smoother. i have also set my base to 0 and the others are 0 too except for the idle. it seems to allow boost to kick in sooner the richer it runs. need to log what is going on though but the ecu has to get use to it first.

 

[91-gsx]

i went and tested the new settings that i have, and only got a few knocks but most counted was 2, that is so much better. takes a load off my chest, also tells me that i do not have a faulty knock sensor. only reason 2 knocks sounds good to me is that when i first got the maft setup and leaned it out i got 42, then zeroed the mid and wot out and got 25, not i have the AUX set to 0 and BASE set to 0. might try leaning it out and see if it will knock more, if it does then i will keep these settings until i get bigger injectors.
thanks for all your help guys, got some good ideas.

 

[sweet97]

Good deal. You will probably have to leave the mid and wot on Zero but at least you are taking advantage of the MAFT and don't have to pull it! congrats, Mark