sbrown99TA

Okay, so my friend with an 01TA with a HUGE nitrous shot on it wants to be able to run leaded fuel. The stock 02's take a crap almost every time he runs a tank of 116 octane, which is getting damn expensive. I know there are ways around it, uninstall the 02's just for the strip etc, but can't we actually just tune them out completely so the car does not even need them? I helped my buddy tune his F.A.S.T. and the speed density system works great, even with the huge cam. So, my thinking is that I can map the VE table using EFI live, monitor the wideband the whole time, plug the results of the log into LS1 Edit, and use the VE table for the part throttle stuff. Does this sound logical? Also, would the MAF have to be eliminated if we did this, or can it be used as a tool to calculate the speed density more accurately?

Sorry for the long post, but this is new territory for me and I just don't want to head off in the wrong direction. Once I get some direction on how to do this, I'm sure I can figure it out. Thanks a ton for any input.

Bink

Here you go read this :
Fuel Trim and VE Says it all. Good Luck, Let us know how it goes.

ChrisB

VE/MAF and Open/Closed loop (non-O2 vs. O2 feedback) are two entirely different questions.

You can just set the temp to enable learning/closed loop to a higher temp than you ever see and the car will never work of closed. The the fuel/air multiplier table will simply define your target a/f ratio.

So whatever scheme you use to determine air massflow (be it maf or speed density) will try and achieve the target a/f ratio as outlined by the f/a multiplier table.

sbrown99TA

Thanks Chris and Joel. I think I'm on the right path, but just want my hand held at the beginning to avoid small problems that add up to one huge one down the road.

This is where I'm semi-confused. So, if I disable the closed loop stuff altogether, the MAF readings vs. LTFT's need to be damn close to 0 at ALL points before doing so to make sure that the car is not having to adjust via the feedback system. Once all LTFT's are at or near zero, we know that what the f/a modifier table is telling the PCM to do based on the MAF readings is correct, and can make small changes to the table as needed based on wideband readings. Yes? The only part that's really throwing me off is that the car we're doing this on has never been able to have a nice MAF table curve AND have the LTFT's near zero in all cells. It has a custom intake thing and my thinking is that because of the shape of the tube and it's curve, the air hangs to the outside of the turn at very low throttle and makes the car run lean, but at anything over 30ish gms/sec it goes rich as the air is moving with enough volume to completely fill the MAF. So the curve to get the LTFT's all near zero is totally goofy.

So, would the MAF table really be the best thing to use on this car since the LTFT's swing so much, like from -12 to +3? Or would it be best to change the f/a table? Or VE table? If it was a bone stock car, I think I would just disable closed loop altogether and go from there, but this car has a big nitrous cam in it (242/246), is 388 cubic inches, etc. Many, many variables, so it makes it a little more confusing for me.

Thanks for any input you guys have, you have no idea how much us beginners appreciate the time you put in to help us. Thanks again, and merry Christmas.

parish8

iTrader: (6)

let me see if i understand this. i will have no cats, if i want to run some leaded fuel i can just tune them out by giving it a temp so high it will never go into closed loop. i can then pull the 02's out and plug the holes and keep the maf. with no 02's or closed loop the ltrims will be at 0 wich wont be perfect but the WOT tuning should still be the same as before.

the knock sensors would still work right, at that point just tune from the dyno wideband and watch for KR?

what is up with the widebands at the dyno shops? why do they seem to be able to take the leaded fuel? what about these incar widebands, will they take some leaded fuel or do they die quickly too?

ChrisB

sbrown99TA: Pretty much. You don't need to worry as much about ltft's if you are staying open loop - as they won't effect your WOT tuning. How close you get them to zero may have an effect on your mileage, but with a big nitrous cam and leaded gas that probably isn't an issue anyway.

Really the best thing to do would be to buy a lm-1 wideband and use that to verify what you are running. New sensors are only 35 bucks or so anyway . Basically as long as the tune was close go ahead and throw it in open loop. You can still do the normal VE tuning previously discussed (based on maf/map calculations) - that might help a big with your issues. Use the wideband as feedback to see how close the transfer funciton is mapping commanded vs. actual a/f ratio. Ideally you would use the VE table to correct for any inconsistencies, and in a perfect world once it was setup you could just type in the a/f ratio you want at each point and let it go. Realistically go for that then use the wideband as feedback.

Parish8: Yep - everything will work the same except you will have 0 for your trims and no o2 feedback.

re: lead - the o2's can definitely take some, it's all a matter of degree. Leaded gas kills dyno sensors also - but you spend way less time actually exposing the dyno sensor to the fumes than an in car setup would. If you drive around on the street all the time with leaded gas you can probably afford a new 35 buck wideband every once and awhile anyway - heck, that's cheaper than a full tank of gas

Crazy C5 Cowboy

I'm new to the LS1 Edit, I am following you all here. I just put FLP LT's on my car with Hi-Flow cats, but am considering off roads for the increase in sound.... Would have to disable my O2's. So the best way would be to raise the temp for closed loop to something like 280 degrees or something? I also removed all my AIR/smog stuff and turned off the three ses codes, is there anything else I need to do? What are LTFT's and trim? Sorry for all the Newbie questions, I feel like an elementary school kid talking to professors at Yale or something

I am also ordering a wideband because I just did the intake/cam/heads/throttle body with my exhaust and want to tune it. Any of you would share your wisdom on how to use the wideband log for changing fuel tables and such with LS1Edit I would be SOOOooo greatful!! I am still lost on finding the table and what the #'s are, won't touch any of it until I know for sure what I'm doing.

TIA - Dan

sbrown99TA

For installing off road pipes, all you need to do is disable the DTC's that are set by the lack of rear 02's, we're talking about getting rid of the front 02's, which are used for fueling system calculations. All the rear 02's do is monitor catalytic converter operation, the fronts are a primary source for fueling info. Don't mess with the open/closed loop operation.

LTFT means Long Term Fuel Trim, it's how much the computer is having to adjust fuel delivery to hit the target air/fuel ratio.

parish8

iTrader: (6)

i really like what i am hearing here, seem to me if you have the fueling right at WOT up to the limit of unleaded you could use this method to run some good leaded and crank the boost WAY up. just have to watch the knock sensors to make sure nothing crazy is going on.

now for the big question, anyone figure out a way to get past the maf limit yet cause i think i can get the that limit with pump gas

ChrisB

On the MAF limit you need to overcome both the max frequency input limit and the max variable size in the pcm. I fyou need to extend it a bit you could get a maf translator and set it to max lean (-20% or whatever), then alter the maf transfer table in the pcm in the opposite direction (+20 if the maf translater is airflow based, if it's frequency based you will ahve to calculate the actual change). This will give you a greater maf measuring range, though you may still hit the 512 g/sec limit. To counteract that you need to scale the MAF flow rate table and the injector constant by the same value.

Crazy C5 Cowboy

Ya know.... I thought I was half-way intelligent, but after reading this I feel like heading straight to the special-education classroom!! What language is that

What #'s do I disable for rear O2's do ya know? I also have a couple questions maybe you guys could help me:

1- What is the purpose of Gear and Gear2 in speedo calibration on the Vette LS1 Edit??
2- When you guys refer to frequency, I am guessing this means the MAF sort of 'listens' to the air flowing by it's sensor and different flows make diff sound frequencies??
3- And finally, TCS (is this throttle or traction control system?) by changing values of these affect the spin control?

Thanks for assisting the handicapped

MNC5

Chris, I went the MAFT route with my set up but removed the MAFT because I was to easily confused while dialing in my LTFT's

My vehicle flat lines the MAF @ 5,000rpm to 6,500rpms. I tuned using the VE, PE and IFR. It runs great IMHO after flat lining the MAF. It leads me to wonder how much the PCM relies on the MAF readings @WOT?

97M6Formula

iTrader: (6)

Everyone has to learn somewhere and this is a great place to....first of all the frequency they are referring to is actually the the amount of mv(milivolts) that the maf puts out and then the pcm reads that to compensate fuel. The maf sensor feels how much air is coming through and then sends a voltage to the pcm which adjusts for it. And tcs is traction control system you can tune it to how much it cuts out throttle.

ChrisB

You can definitely do that also - how well it works depends on how soon you max it out. If you don't do that till 5000rpm then you can tune w/ pe for WOT pretty easily - as the only time you will see the 5000-6500range is probably WOT - and with a blower your boost level should be fixed vs. rpm. It still won't compensate properly for weather changes, but as long as you are close a little fluctuation will not matter.

On the other hand if you max out sooner (bigger motor/blower), or you have a turbo (can see diffferent boost levels at any given rpm level, or your boost is adjustable) you are going to have a much more difficult time tuning it when the maf maxes out.

97M6Formula - nope, the frequency is not a voltage output - our mafs output a frequency, from about 1khz to ~12khz or so (they go higher, put the pcm stops sampling), and the magnitude of that frequency is proportional to the airflow rate. The voltage is always a 0-5V square wave, 50% duty cycle.

Fetumpsh

Too right, now it's your turn to learn......
The MAF signal output is NOT in mV, it is a 0-5V square wave that varies in frequency depending on the flow rate measured. The PCM measures the Frequency of the sqaure wave (by measuring the time between pulses), it is not a voltage measurement like say the old L98 MAF's.

4thGENRETARD

You could buy an export PCM. My cars don't have any O2 sensors. All the necessary programming would already be there.