parish8

iTrader: (6)

i am maxing my maf by 4900rpm, probably up into the 70lb/min range. recently there have been a couple of posts about a resistor mod for the maf to increase the range. here is one >> https://ls1tech.com/forums/showthrea...t=resistor+maf

i decided to try this route. so far i have found a good resistance value. i wired up to the maf bridge like in the pic's in the above posts and ran the wires in the truck. i hooked up a 10k pot and a switch to turn it on and off. i also added a bunch of fuel with the IFR just to make sure i didn't run lean while testing.

first value was 1700ohm's, that made a nice diference but it didn't look like it was going to be enugh. from my calculations it would have maxed the maf at 74lb's instead of the stock 60lb's. i then switched to 1200ohms and am seeing some numbers that look promising.

at idle stock was 1.6lb vs 1.1lb with the resistor, that means i am geting 45% more flow than reported.

then i tried other throttle positions. with other flows.

20 droped to 14, 42%
25 droped to 18, 38%
36 droped to 26, 38%
50 droped to 35, 42%

prety consistant changes if you ask me, i kind of expected some wacky numbers on one end of the scale. from what i am seeing if i go with a 1200ohm resistor 60lb's of reported air will really be about 40% higher or 84lb's actual. the t76 is supose to max a little higher than that so i might go a little lower. shoot for a 90lb/min max

i dont know how much programing will be required to make this run right. i have a vacume modulated tranny presures so nothing to sweat there. the IFR will ned adjusted and the timing tables will need adjusted since the reported load will be way higher than reported. not sure how much other tuning will be required. i will post up on how this works and what all i have to change in the programing.

smokinHawk

iTrader: (48)

hey thats awsome. good testing there.
hopefully this will work as a cheap fix

S_J_H

Sounds good. It works for sure. I have been doing this for the last several years now with no issues. I'm using some where around 900ohms with a 85mm maf.
Steve

smokinHawk

iTrader: (48)

how many lbs/min of air are you seeing then?

S_J_H

I have it setup to read 67.5 lbs/min at the peak Htz which is lower on the 98's(11250) which is only 46lbs/min with the stock calibration and table for the 85mm MAF's. So I reduced it by about 30% with the resistor.
I'm hitting 67.5lbs at 5400-5500 RPM right now and then it flatlines. So I have no idea how high it really is at redline. I could recal the maf again but I'm just using the pe table right now because I'm to lazy to mess with the MAF tune again. I'm out of injector so it really does not matter anyhow.
Steve

parish8

iTrader: (6)

i am hoping to have some kind of corection factor when i get done so i can calcualte how much air i am actualy flowing. i am also hoping the maf does not max out on me somehow. i dont really know what or how this resistor is working. if i get a 50% corection factor and it could read 60lb's before does that mean it will read 90lb's now or is there some point that the maf itself will flatline? i know before the maf was still going up in hertz but the table in the pcm will only goto 60lb.

parish8

iTrader: (6)

today i wired in a 1000ohm resistor and programed in more fuel. i think the 1000ohm will put me right at a +50% corection on the maf so i added that much fuel and went for a spin.

first problem was i got a block from the house and the maf was unhappy, set a p0101 code and switched over to speed density. my ve tables were uncorected so when this happend it went WAY rich and woundn't even run. i limped it home and shut of p0101 code and tried again. with the code shut off it started and drove but the initial warm up period was not good. way rich and way lumpy. i relearned the ve table and put all of those numbers in and went for another spin and right now i think i am back where i was before. my fueling looks exactly like before with the unmodified maf. i wont know till tomorrow if the cold start is still a problem or not but i did drive it for awhile and it ran great.

i am programed way rich with PE vs rpm and running low boost right now. i wanted to do a on off test of the maf resistor but when i was at WOT and turned off the resistor it went so rich it started missing. i need to dial in my fueling closer before i can try that i think. it would be cool to have a somewhat acurate corection factor so i know how much air i am flowing.

my part throttle fueling is and was before lean at part throttle and rich at moderate throttle. i think the only way to adjust this is with the maf table. before i attemt to get this perfect i think i will try and get my wideband to read thru efilive so it is all on one screen. then it will be easy to look at the maf freq and adjust with edit.

QuickSilver2002

This is great info and you are making me want to try this.

I have a few questions for you.

What do you mean by relearned the ve table? Did you scale the numbers in it just like you did in the injector flow table (* .50)?

I'm assuming you have done the following so far:
- Wired in the resistor (and have seen about a 50% reduction in frequency output)
- Cut the injector flow rate in half
- Cut the main VE table in half
- Moved all the rows in your timing table up (1.0 row moves to .50 row, .80 moves to .40 ...)
- left the MAF table alone (for now)

Anything I am missing?

Do you have logs of the MAF raw frequency from before? It would be nice to try a similar load situation and see how close to 50% you are.

Is this the 85mm MAF you are running? Can you post what your stock MAF table looks like? From what you said earlier (60lb max it should be going to about 453 g/sec).

This just seems too easy!

slow

iTrader: (7)

what changes did you make to the VE table, why not just cut engine displacement in 1/2 to compensate for that?

Ryan

parish8

iTrader: (6)

i am really figuring this out as i go. not following any preset list. the 1000ohm resistor gives close to a 30%drop in maf reading. 60lb before is now 40lb. 60lb now is really 90lb's. 90lb's is about all i can see with this turbo so that is all i really need to have avaliable. i think the more i reduce it the more course the fueling will be.

seth the guy that help me with my turbo tune showed me how to learn the VE table using efilive v5. it is a complicated deal and i doubt i could even talk someone thru it. he helped me program in a few things on my lap top so it would work. if you do a search on it here and at some ls1edit or efilive sites you will find more info on it. i relearned that table only because he said i should if i do any maf messing. he also told me he has tried messing with the maf output and didn't get good results.

i have the resistor on a switch so i can turn it off. right now my fueling is on the rich side and when i shut off the resistor it goes so rich that it starts missing, with the miss it is imposiable to do any on/off tests. i hope when my fueling is closer i can go run a test at diferent airflows and turn it on and off a few times to get a corection factor. then on efilive i will use a calc pid to show me the calculated auctual flow of the maf.

i am running open loop, no 02's and leaded fuel. i have no ltrims to adjust my fueling. before the resistor mod my idle a/f ratio was lean, like 16-1 and my moderate fueling was rich. now i have the same thing but it is exagurated some. more like 17-1 at idle and 11.5-1 at moderate throttle. wot is easy with PE. the only way i can think of adjusting the part throttle fueling is with the maf table. i am going to lean it out with the IFR first so the top of the scale is where i want it and then adjust the bottom portion to get the fueling where i want it.

the whole idea here is get the pcm so it can fuel corectly at 55lb's of air and 85lb's of air and at diferent temps too. i think this will work. right now i run a mix of leaded fuel and 17psi and then switch to pump and 10psi and my fueling is adjusted with the PE based on rpm only since my maf is maxed. at 10psi i am retardedly rich and at 17psi i have to worry about some cold dense air causing me to go lean one night.

so far i have put in the resistor
adjusted the IFR down 33%
learned the ve table and put in the new numbers
turned off test p0101(i think thats the number)
reduced most of the timing table by 10deg(for now, need to work on that)
left the maf table alone but am about to play with that.

i also wired in my wideband to the front 02 input so i can log it on efilive, it kind of works but isn't ideal at all. the wideband has a 0-5volt out and the stock o2 only wants to see 0-1.1volt. i used a resistor to drop the voltage but it seems to not be working well. i need to find a 0-5volt input that i can hack the wideband into. right now i have my boost and fuel presure going thru efilive and it works well.

Jammer

iTrader: (1)

Sweet sharing! Keep it up.

QuickSilver2002

Ok, tell me if I am close on this VE learn thing.

You use efi-live to log a bunch of driving conditions and include MAF, MAP, IAT, RPM.

You then export this data and load it into a spreadsheet. It averages the MAF readings for the MAP/RPM VE matrix and then applies a formula to generate a ls1-edit style VE table for you.

Curious, were the values about 30% of what they were before?

Here are a few thoughts on figuring out the resultant % change.

Turn off the resistor and put the tune back to where it was. Log MAF raw frequency, MAP, RPM, boost (if you have it). Create a pivot table in excel to avg the values.

Turn the resistor back on and put the modified tune in. Log the same values again. Create another table based on that data and then look at the variance. This should help clarify if the resistor is giving you a linear reduction or not.

I can help you crunch #s if you need that kind of help.

On the WB thing, why not just drop your FP input for now and log the WB data the same way?

parish8

iTrader: (6)

it seems to be working. i adjusted my IFR to the point where my moderate throtte fueling was where i wanted it. at about 50%throttle and right before the boost comes on like -2in i got my fueling around 12.5-1 just by adjusting my IFR. it goes richer from there up and leaner from there down. at WOT with no PE it was down to 12.2-1. i am real happy with the top part of that scale and didn't change anything on the MAF table up there(7000hz up)

below that 50% throttle pos it got leaner, a lot leaner. all the way to the point where it was missing at idle. i used the maf table to adjust for this. i adjusted from 0-3000hz as a group and then 4000-5500, 5500-7000. then went for a cruze and watched to see where the fueling went at these points. it took about 5 reprograms but now i am around 14.7 at idle, 14.2 at a 75mph cruze, and progresivly richer up to the 50%throttle range. finialy i set my PE to 1.03% and that got me from 12.2 down to 11.8 or so at WOT.

only problem i see right now is at idle in park it goes a little too lean, like 16-1(almost missing). so far i am only testing at about 8psi. tomorrow i will go out and see if i can get an acurate corection value, use that to set up a pid that shows me actual airflow, then go out and do some low boost and then moderate boost and then high boost runs. if my fueling stays consistant then it was all a sucess.

before at 8psi i was maxing the maf at 6000rpm and at 17psi i was maxing the maf at 4900(flatlineing it). i have a pid set to show 150% of the maf reading or what i think is close to the actual maf flow. i did a short run and hit 63lb's at 6200rpm. i think that is prety close to correct but i want to get a corection value anyways.

parish8

iTrader: (6)

with efilivev5 you can set it up to fill in a VE table. that is the part seth helped me with. i dont know how i got it set up but it is set up. the new VE numbers were about 30% less then before so i might have been able to just reduce the numbers all a percentage.

if you look at my first post you can see where i was turning the resistor on and off and geting an actualy corection factor. it was prety close to linear. i tried to do that with the current resistor but i was soo rich when i disconected the resistor that it flooded out. can't get a good maf reading if it is missing. now that i have my a/f ratio up near 12-1 i should be able to run that test. i just get the maf steady and flip the switch off for a sec then on and write down the change. then get a higher flow and do it again. one at idle too.

my fuel pump sensor is tied into the rear o2 right now, it is the same input 0-1.1volts. i need to find a 0-5volt input that i can hack. not sure what i have avaliable.

parish8

iTrader: (6)

i just hooked up efi live and went thru the pid's. there is a fuel tank presure pid and it is 0-5volts , i clicked on it and fired it up and it showed 1.8volts, pulled off the gas cap and blew in some air and it droped to 0volts. that looks like a perfect input for my wideband. going to get that hooked up and working before i go out and do any more testing.

when i get done here i might just be loging boost, fuelpresure, wideband o2 and be able to control fueling acurately over 60lb's of air. this is going to be sweet!!

parish8

iTrader: (6)

got some logs, looks like the wideband thing works prety good. thats a good thing.

i will need more loging to be sure, some of the numbers below dont make a lot of sence like the maf freq not exactly matching the maf lb's but the rpms and conditions are changing prety fast so if the pids are gathered at a slighly diferent time then it might make sence. ignor the KR, part of that is too much part throttle timing and part is exhaust bumping.

from what i am seeing as i incresed the boost it got a little leaner. i need to put some better fuel in there so i can really crank it up and see but i will probably save that for the track. definately need more data before i form any oponions here. as long as the freq goes up a little as flow increases things will be ok. fine tuning of WOT fuel could be done with the maf table. if i turn it up to 17psi and still only see 11,000hz then this entire project was a waste. here are screen shots of my logs, this was all one log, just turned the **** up a little each run.

parish8

iTrader: (6)

these screens might tell a more acurate story. the last log i didn't carry it high enugh to get a good comparison but you can see it geting lean up there.

parish8

iTrader: (6)

after looking at the charts all stacked one thing worries me. the only real diference on the last run was my IAT's were much higher, i think i sat of the side of the road a little too long that time and things got warm. it all looks good prety good other than that run. hmm, need more data.

smokinHawk

iTrader: (48)

your getting some knock! ouch!

the MAF 1035....1117500 readings is that in Hz?

parish8

iTrader: (6)

my waste gate is pressed against the frame. i think that is some of it. i get a lot of KR at odd times. when i do a full 1/4 mile and preload the driveline on the starting pad i usualy see 0 knock the entire run. something new is the knock retard just as the boost comes on. that might be real. i think my timing tables are still too high at part throttle. need them to drop faster as the load comes on since the reported load is much less now.