funstick

hi guys i am new here and i keep reading about maf issues.
i am no suave programmer in fact i just started prom tunning myself and will admit its a steep curve.

in the late 80's GM came up with a brilliant update called the speed density update for all of the MAF cars. its pretty simple hardware wise to do. you only need add a 5 volt refernce to a map sensor and move the input for the maf to the output of the map and add a ground. delete the MAF put it in the garbage whatever makes you happy!! lol. anyways the only other big change was geuss what THE SOFTWARE. yeah they came out with a prom and map kit that does away with the maf.


you best bet to find one of these wonder bread jobs is to walk the boneyards looking for you car until you find one without a MAF. now the only real thing is gonna be modding it with the tunercat becuase i doubt theres a mask id program for it. but who knows.

as for tunnign MAF cars there is a sort of easy way to do this. start before you modify alter tune or other wise alter yr vehicle by recording yr actuall running MAF frequncys in MHZ across the entire operating range everything form idle to WOT(i have an inexspensive craftsman multi meter that can do this most decent meters can).a scanner can be helpful but also full of s@#t. also record yr tps voltages and yr o2 sensor readings. this is how you establish your baselines for any furture tunning. sure the ecm can calculate away( and give detailed info) but without knowing what its calculating your sort of flying blind. now perform your mods and take another set of baselines. now compare these to the originals and you will have a more complete picture of whats going on. an o2 sensor reading of 0.78 volts with a with a low MAf frequncy indicates the engine is running rich. but why ???

well first start by checking fuel pressure if the fpr is vacum referenced the low signal form a large cam will drive idle and part throttle feul pressure up. check basics first. get good baselines then form all of yr gathered informantion your maf tunning will be much simpler becuase you will understand what the engine needs in terms of Fuel Spark and A/R

also things to keep in mind

most high perf engines make max power at a good 12.7-12.5:1 A/F ratio. but they also like to lean out up top to 15:1 becuase it takes less time to brun a lean mix.

these are examples. going for a stiometric Airfuel ratio will make you go bonkers !!!

i am not going to proceed to tell this group how to tune but feul metering is feul metering. i ve been tuning carbs for yrs and these are the same step i would take with a carb before grabbing the jets the advance springs and a timing light.

other things to watch for maybe erratic engine vacum it can cause havic on a efi car by constantly driving values up and down very quickly.

anyways i am open to advice i will ask questions and i will offer up my life lessons to you. !!!

good to meet you all i hope we can share some info !

tpi_roc

CustomX

people have been dropping speed density setups (730) on maf cars for a while now, its nothing new............

tpi_roc

Im interested in hearing his explanation for lean burning easier and high performance vehciles running at or beyond stoich.

Grim Reaper

No, this sounds more like what Tomcat has been suggesting with wiring in a MAP sensor onto the 165 ECM and running the Aussie 808 Bin ($5E if I recall).

Funstick, can you elaborate a little more? You might have a "third" alternative.

funstick

sorry for the poor pharsing it was late and i was tired


ok on the hardware end of the maf to map swap out.

remove maf take brown wire with white strip and dedicate that to the map output. should be brown with a white stripe. may vary by model??

now discard cap or remove the orange maf feed wire. its the 12 volts feed used for the maf. the computer does not power the maf in most older maf cars.

now tap the gray 5v feed to the tps and again route it to the gray map feed wire.

then add a ground for the map should be black with a white stripe.


now as for software gm made this update and the prom should still be available for sale through yr gm dealer. not all cars had problems but for the ones that did this is a good upgrade to settle the motor down.

as for the definition files ???? may have to be decompiled and recompiled to make any sense of them. your going to have to play with the source code.


i know nothing else on this subject.

as for maf car tuning take yr time be patient and make small change everywhere in the maf table and the lv8. also play with yr tps it will have a great affect on everything else.

ps most maff cars like tps at closed throttle to be .55 seems to work well.

good luck.

funstick

sorry that i didn't elaborate on the a/f ratio thing. yet again idiot was tired.

it very true that the best air fuel ratio is not stioch.

heres how it works or rules of thumb to help you out. these are just generalazations every engine will be different.

idle likes to be rich 13.5-13.7:1 will really smooth it out. this will also help with throttle response.

low end may like to see stioch but at wot it would preffer to be rich to say the low 13:1 range

now at yr peak torque plus to minus 500rpm the engine will like to be stioch period wot and part throttle.

typically most engines will pick up power by running a little leaner uptop. ive seen big block chevys scream at 15.1:1 and ive seen them fall on there face to. but its all just rule of thumb.

most of the time though going past 14.7:1 to something higher puts additional strees on the exhuast valve by driving up EGT's

tinkinering is really the best policy.

stioch isn;t always the best fro max power but it be pretty damn good to start from.

hectorsn

The only engine I know that GM did this to was the 2.8L V6 in Corsica, Beretta, Celebrity, etc. models. Not on the V8 F cars to my knowledge. And not that it makes a difference but it could be more than coincidental, the ecm was a 730. And I'm not sure about the TPS stuff. Most of the code I've seen for engine operation uses diff. tps comparision or percentage. The only things I see that tend to use TPS voltage directly are the accessories and the code checks.

grumpygreaseape

the add of a map was a butt coverin last ditch by gm to take care of some fairly large quality control ,for lack of a better term, shortfalls-bad parts and bad driveability somethin had to give. mostly affecting vin "w" 2.8.

Grumpy

Dunno where you got this tidbit but it's very wrong other then for some 4 valve high RPM motorcycle applications where they can run insane BMFC numbers of like .35.

AT max HP you need some additional in cylinder cooling to keep the engine out of detonation. Quench area design and volume pretty much goven how extremely rich you'll need to run.

IT'S MUCH SAFER to START RICH and then lean things down. After all plugs are cheaper then exhaust valves..

funstick

grumpy i wasn;t saying that lean up top is always better. i ve had engines that had either a poor cumbustion chamber desing or low compresion that responded to lean jettings uptop. the best thing to do is experiment. ive had a few turbo chryslers that liked stioch with a stock cam but liked rich up top with a super60 cam.
just passing the buck these guys seem to tune for stioch. yr very grumpy grumpy.