i just did a 305 to 350 swap in my p/u truck. hopefully i can get some help with some tuning questions. new engine has a 210/214 @.05, 114 sep, .510 .472 lift. and a 2" bore tbi. world s/r torquer heads, edelbrock 3704 intake, 65lbs injectors at 15lbs fuel pressure. i will probably need more pressure but not really getting in it hard yet because of tranny issues. my tune is close enough too get me back and forth to work and do some dataloging but it has a real bad surging between 1700-2200 rpm at light throttle. i was reading on here that sync to async at low pw can cause this. its a 95 truck so i have
a $0D code and im not sure what values to change to shut off async all together for testing this out. this might not be it at all but im new to this stuff. here is my last datalog and bin. also, what is the easiest way to use excell to sort and group blm numbers together for making fuel adjustments? thanks.

 

Its NOT ASYNC from what I can tell. At about 4.5 % DC and 1.4 ms pulse width it should still be in Sync mode. This is during your 50 mph cruise in 3rd @ 2,000 rpm and about 10% TPS. The O2 PID needs some work however because your Integrator is hunting in an attempt to correct the A/F ratio instead of the PID loop doing that function.

If you are able to burn your own Chips, try a chip with Semi-open loop fueling. This will disable the BLM learn and leave the Integrator there as well as command the A/F ratio in the Open Loop Air/Fuel ratio vs. Temp vs. VAC (or MAP can't remember which) table.

It is the Option byte is at L400D, Bit 0

Your timing seems way advanced in the lower RPM, lower load cells. This will cause a terrible bucking sensation as you cruise along at light throttle. 38* @ 45 map and 2,000 rpm is too much advance.

Try the attached spark map for starters and see where it gets you. Add 2-4* PE spark with this and it should do well.

 

thanks. ill try that timing table tonight. im very new to tuning so im learning, but let me ask you this. i found in the $0D hack that L400D is afr mode word 3 bit 0 like you said, and i see i can turn it on and off in tunerprort. but i dont see the table it uses to set the afr? is my xdf not set up with this table? also the hack says ( IF COOL L.T. THRESH USE TBL L4BB0 DURING CLS LP IF b0 SET, L400D). this threshhold is 150c so that is pretty much always when in closed loop right? soo does this mean my blm will always say 128 so i cant use them for tuning? i dont have a wideband. also what should i set my afr to if i can find these tables. thanks.

 

ok. i made sthe changes you said fast 355, tried your timing table, and i think i swithced the right thing to enable open loop. seemed to work because the blms stayed at 128 all the time. i found the table for afr but didnt change anything there. the surging didnt go away. and the power seemed down. so do you just use o2 volts to set the fuel in open loop? it seems like the volts ranged from over 1.0 to down below .15. my main problem is the surging at cruise speed. i really dont understand it.

 

OK, time to try something a little different.

I am modifying your latest .BIN in hopes to get rid of the surge.

1.) Your VE tables seem too be OK because the integrator is holding within about 5-10 counts from 128. (You can see this in TTS Datamaster by opening the playback file, selecting the Histogram option under the "VIEW" tab, then look at STerm vs. MAP as the file is played back it will populate the INT vs. MAP vs. RPM table. You can then use the average BLM numbers to recalculate your VE tables.

2.) You O2 sensor is cross-counting, but it is over correcting to the extremes. It goes WAY TOO rich then comes back WAY TOO lean. Less than 100 mV then up to over 1,000 mV. I can see the MAP fluctuate when this happens and the RPM fluctuates about 50 or so. I am thinking this is the surge you are seeing.

3.) The timing seems OK, but might need a slightly faster curve with less vacuum advance. This could add a touch of power, but not much. My engine is nearly 10:1 compression, pulling a 3.08 geared 5,500 lbs Van into the wind. I honestly completely missed that you were running the SR Torquers in place of the swirl ports and that will change things up a little.

4.) I am leaving the system in Semi-Open loop. With that I am setting the lower load section of the Open Loop AFR vs MAP vs Coolant table at 14.7:1 instead of 16:1. This will richen things up and let us use the Integrator to fine tune the fuel tables.

5.) I turned the EGR off at low loads. The EGR at low engine speeds and loads is unecessary due to your larger than stock cam. The GM LT4 did not even have a valve and the cam in it was smaller than yours. Having the EGR on down low can exagerate the surge. I left the higher load, higher RPM EGR enabled to keep the cylinder temps down when under continuous load.

6.) I have modified the Proportional Gains and O2 target voltages to what I believe will more closely match your combo. They work well with my ZZ4 cammed 350 with headers.

7.) I brought the idle speed more in check with what I believe this combo would want.

8.) The shift tables are still stock and the 4,800 rpm rev limiter is in place. You have a cam. Just curious if you plan to move the rev limiter, shift points, etc.

I also made a few other changes that make the engine respond faster, such as changed the PE Delay from 15 seconds to 3 and dropping the bypass PE delay RPM from 4,500 down to 2,500. This will make it jump quicker when you put the pedal down. It will use a little more fuel, IF you are an aggressive driver, but otherwise it won't change a thing.

 

thanks alot. ill burn that bin today and try it out. i do plan on changing the shift points and stuff but my 191,500 mile transmission is on its last leg, and i need to get trough the holidays before i can have it rebuilt and get the higher stall that i probably need. after that ill try and turn things up. also, what does the proportional gain do? i really want to understand what all this stuff does. thanks again.

 

well i tried your bin and its tons better. almost no surge at cruise speed. there is slight surging on accelleration now, but overall its way better. so help me understand what made it better. also why are my blms sometimes going away from 128 this time. i thought that would lock since in open loop. it must be going out of open loop sometimes? is this semi-open loop something i can leave on for good? do most people use this mode? so do you tune fuel with the afr in this mode and not the ve cells? and base adjustments on the o2 and int numbers. thanks. attached is latest datalog.

 

Okay I looked over your Datalog this morning. I thought that the BLM's locked too. I pulled out my Prom Burner and my scan tool this afternoon. I tried my hardest to make the BLMs shift from 128 with my setup. They stayed fixated at 128. I then looked over a couple of threads where HaulinA$$, Dimented24x7, and I were talking about this. I compared both my current .BIN and yours. Finally it dawned on me that yours is set to target 14.7:1, mine is elsewhere. I set my open loop a/f ratio table to match yours and my BLMs started shifting. Seems I was wrong about that. It locks the BLMs if you target a different A/F ratio than 14.7:1, not just by checking the box. You have to target 14.7:1 for the BLMs to update.

You can leave the open loop in place, it was used on alot of the 4.3s.

Your injector constant was set way wrong for 65# injectors at 15 psi. The stock fuel pressure is 11 psi and you moved it to 15 psi. That gives you 9.56 gms/sec rather than the 8.19 you had in there before. Your BLMs were also indicating that you are pretty lean in the higher MAP, higher RPM region (acceleration) probably giving you the surge. I added 15% (just enough to combat the injector constant change) fuel in these areas for you to try. Until we get a log with the new injector constant it will be tough to tell what is going on. I can tell you that right now it looks like you will be running short on fuel with this injector/pressure combination though.

One other thing that I overlooked was the 2" TBI. Looking at the logs I noticed that the MAP rose very quickly compared to the throttle position. So much so that you were hitting very high MAP readings before recieving PE and your AE was lean.

Try this one and get back with me.

 

thanks alot ill try that today and get back to you. i did figure i would need more pressure. probably enough to get to a 90 lb/hr injector. i have a walbro 190 pump so i can do that. should i just do that now so im not having to re tune it all over again with the new fuel pressure? or will it stay very close by just changing the flow to match? thanks

 

The later PCMs seem to stay pretty close, but if you want, bump the pressure and I will recalibrate the injector flow rating in the chip to match the new pressure. Let me know what you bump it to. Can you hit 18-20 PSI? At 18 psi you will flow enough for about 315 Flywheel HP which I feel you can hit. At 20 psi you have enough fuel for 330 Flywheel HP (FWHP) You can run 30 psi of fuel pressure on the TBI style injectors if need be. That would eliminate the need to go with the 90# injectors on all but the craziest setups. The smaller injectors at higher pressures atomize the fuel better as well.

 

tried the latest bin. runs pretty good. still some dead spots but pretty good overall. i cant wait to get my tranny rebuilt and get a higher stall convertor. i think ill be happier with it then. can you help me understand what im looking for in the datalogs to help me with adjustments? with it set in open loop am i supposed to use the int to adjust fuel cells. i just dont see a patern in the log to adjust somewhere. the int numbers seem fairly close. this is good right? i think i will wait to adjust my fuel pressure till this weekend. ill up it to 21lbs. that should put it at equivalent of 90lbs right. i have 65lb injectors. is this the right way to go with my combo? also i have a tbi spacer with a slot between the 2 bores. is this good or bad? also what can i do to help fuel mileage? what is this highway mode ive read about? is that not in the 0d bins? thanks

 

Setting L400D, bit 0 is not semi open loop mode but rather lean cruise mode in closed loop. What setting that bit does is allow the PCM to use the "Open loop AFR vs Coolant vs Vac" table in closed loop when the enable temp is reached. With the bit not set, the code will target the Stoich value set at L48DD when in closed loop and BLM's will remain fairly constant only bieng affected by things such as EGR and CCP. BLM's are not locked by setting the bit. To lock the BLM's you must do it manually but when the bit is set, this causes surges and the proportional gains to get out of whack. In open loop, the "Open loop AFR vs Coolant vs Vac" table is always used. When The bit is set, the code will target whatever AFR is in the approapriate cell in the Open loop AFR table and BLM's will adjust accordingly. Whenever you are tuning fueling, the bit should always be off as well as turning off CCP and EGR (and blocking it off). This will prevent BLM's from shifting due to desired AFR modofiers. A handy to verify what is happening is to datalog desired AFR in the datastream by substituting it for IGN Volts. This will also tell you the desired AFR when entering PE. If you are datalogging WBO2 AFR, You can verify that the two match up. HTH

 

soo do you think i should be leaving that l400d set and running the engine this way? fast has been helping me out alot and he had it set that way. when i uncheck that my engine runs worse and blm are off. did you look at my latest bin and log. what do you think i should be doing next. thanks.

 

The reason the engine runs worse and BLM's are off when the bit is unchecked is because the VE tables are off and maybe the Prop gains. By tuning with the bit set, you are compensating for BLM changes due to changes in desired closed loop AFR by adjusting the VE tables. Now when you turn the bit off and only command the stoich AFR in closed loop, the VE tables are no longer accurate and BLM's will shift. Go back to the stock prop gains and turn the bit off as well as CCP and EGR and then retune VE. This will ensure that the VE tables are accurate and BLM's will be steady, not 128 all the time, but steady at 128 +/- 3. When you then reset the bit, the closed loop desired AFR will then come from the Open loop AFR table. This will cause the BLM's to adjust for the change in desired AFR but that is o.k. because that is what you want in order to save fuel. I hope this explains it clearly.

I did not look at your .bin or logs but I can tell from what you and Fast305 have been going through that this is your issue. If I get some time I will check 'em out and post back. HTH

 

Ive been using datamaster to datalog, so what do i change to t output afr? i can also use tunerprort if that is better. i just need to know what settings to change to output afr. so i should go away from what fast355 is having me do and have that bit not set and tune with the blms? help me understand prop gains. i read on a post from rbob on here that you basically cut the prop gain in half if you double injector size. but it looked like fast355 is raising my prop gain from stock. am i not seeing this right. the strange thing is it runs pretty good the way it is. im sure it can get better with more tuning. i just want to understand what is the best way to go about this. i don't have a wide band as of yet but maybe in the future. thanks

 

The whole point is to have it run good with the bit checked or unchecked. When done right, it should work this way. I'm not going to tell you what to do with your ride. I'm only explaining how it works. If you wish to continue on your current path that is up to you. If it were me, I would uncheck the bit, disable EGR, CCP, and DE and retune the VE tables for consistent BLM's. If you do it this way, you will be assured that the VE tables are correct and not some fudged value to compensate for shifting BLM's due to changes in desired AFR in closed loop.

If you wish to understand proportional gains, RBob has a great write up on the GMECM page of Diy-EFI.org.

Lastly, to be able to change what is output via the ALDL datastream, you must know how to read the hack and I don't know whether you can or not. Basically, you just change the address of the proper data word to output desired AFR instead on IGN volts. HTH

 

I am currently building a 700r4 in my spare time, and have been staying pretty busy. I have not had a chance to look the logs over or make changes to the .BIN. I am working on them now.

The BLMs correction WILL still work with the L400D flag checked. The only criteria is that the Command Air/Fuel Ratio has to be 14.7:1. I verified this myself with my PCM. That is why your BLMs were correcting at times and other times they were not. When the A/F ratio was set at 14.7:1 in the open loop vs map vs coolant table it IS correcting the BLMs.

EGR is disabled at part throttle cruise currently. It is only active near wide open throttle and over 1,200 rpm.

I changed the proportional gains to better match your combo. It happens to be what I am playing with on my very similarly cammed 350. Injector sizing, camshaft profile, intake manifold (I also have a 3704), and O2 sensor location have a big effect on it.

I will put the Command Air/Fuel ratio in the battery voltage field.

Did you ever bump the fuel pressure?

I was waiting for a log from this weekend with more pressure, but will just do the BLM corrections on what you have and send them back.

I forgot to disable the CCP. I will disable the EGR completely for heavier throttle tuning.

I do not disable DE because it might cause the engine to stall on Decel. I have tried that route before and the engine loads up bad and stalls, possibly at a terrible point in time. Like about to pull out onto the highway, getting off the gas and back onto it at the top of the on-ramp.

 

That is what I was saying. Bit checked or unchecked, it is still closed loop and BLM's are active only the commanded AFR changes. When the desired AFR changes, BLM's get away from 128 (assuming correct VE) and the new AFR is maintained. This can be verified by the "BLM Enabled" flag. I have verified this with countless hours of datalogging.

As long as you export the data to excell and delete the records where DE is active, AE and PE for that matter as well, and then you adjust VE tables from the remaining data, leaving DE enabled is acceptable although I have never experienced stalling when disabling DE when the VE tables are correct. Also, when disabling CCP, the vacuum line going to the canister should be disconnected and routed to below the gas tank. If not, then the cannister can will fill with vapors which can then condense and fill the canister with fuel. HTH

 

His main problem is that he is OUT of FUEL that can be added with the VE table. It needs more fuel pressure to run properly.

After BLM correction, the VE table is maxed in some places as low as 70 KPA MAP.

I also noticed some knock counts at lower RPMs and slowed the advance rate. It is now running what basically amounts to the B-Body LT1 timing table.

As far as AE and DE. I disabled DE completely in this latest bin just to try it out. The VE tables are already dialed in alot better than some of the ones that I tried doing it, the ones that stalled. I never have tuned by tossing out the AE. In fact on the older 7747, I roll alot of AE into the main fuel tables. It makes for a smoother running engine in my experience. Guess that is a carry over from the 7747's Lack of Resolution, especially the AE.

 

thanks guys, i really appreciate all your help. i just upped the fuel pressure to 19lbs. but havnt driven it yet. i guess ill take the latest bin and up the constant. at 19 lb, my 65 lb injecters should be set to 85.43lbs if my calculations are right. ill do some datalogs tommorow or sunday. thanks again guys.

 

If they are truely 65# injectors, at 19 PSI based on a stock fuel pressure of 11 psi, you get 85.43 lbs/hr or 10.44 gms/sec.

Here is a XDF file for TunerPro that I downloaded and then added alot of features too. Far from done, but it is getting there.

 

i changed my injector constant to match my 19lbs pressure. but about 2 miles into my datalog something felt like it broke, like a switch. it feels like 1 or 2 dead cylinders. engine running extremely rough. almost dies at idle. i was able to get home but it felt like it was way out of balance, just shaking going down the road. in park it is rough up intil about 2000 rpm then it smooths out a little. i havent looked at it yet. but they way it happened so fast im thinking its valve train. like a broken pushrod or 2 maybe. but i guess it could be electrical. hopefully i can get this figured out this week.

 

pulled the driver side valve cover and found a broken rocker stud on the #5 intake cylinder. brand new world products heads, new comp pro magnum full roller rockers and locks, new comp magnum pushrods. is this just a fluke? ill pick up a new stud tommorow and hopefully get back up and running. ive got 1.6 ratio rockers on the intake side. and the pushrod clearance to the head is almost zero at fully closed, but you can spin the pushrod so i think its ok. it gets more clearance as the valve is opened. maybe this is an issue? a broken stud at 500 miles seems odd. especially since my spring pressure isnt extremely high. ill put it back together with the 1.6 rockers but if it happens again i think ill swap them for the 1.5's for peace of mind. thanks.

 

I know that feeling all too well.

How was it running up to the point of the rocker stud breaking?

 

it actually felt a little sluggish. like over rich. but i hadnt really even got it up to full temp yet. did you change something to make datamaster output afr in the volts box? i noticed the numbers to be around 13.8 while i was driving. what did you do to make that happen? ill post new logs when i get back up and running. thanks.

 

If the volts field stayed at 13.8 then the desired AFR is not bieng displayed in the field. It should display 14.7 for normal cruising if the "Use Open Loop AFR" bit is off. HTH

 

I never have put the AFR in the Battery Voltage field. I will though. Just haven't had too much time to mess with it.

 

after looking deeper into my broken stud, i think i overlooked what might be the problem. it doesnt seem like i have enough thread engagement with the polylock. the machine shop assymbled the heads with rocker studs that are 1.750" long from base of stud to top of stud. it seems that i only have about .300" of the stud going into the polylock. i found that arp makes a stud that is 1.895" long for roller rockers. these seem like the ones i should be using. this would give me close to .500" engagement which seems more appropriate. what do you guys think?

 

ok. replaced all the rocker studs that came on world torquer heads with the proper length arp studs. i should be ok with those, they look like quality pieces. anyway, i took adrive tonight with the latest bin. i changed the injector flow to the proper number with my 19lbs pressure on my 65's. performance is so-so. the surging is back on cruise and some on acceleration. zooming in on the graph in datamaster shows the timing going up and down while the surging is happening. so do you use the averge in the histogram for short term to make changes to the bin? what could be causing the timing to go up and down like this. maybe the proportional gain settings? thanks again guys.

 

sorry, here is the log and latest bin

 

Did we ever find a way to disable Async on the $OD mask? Im getting a little surge/jerk when the async flag flashes. I would like to disable Async and just run in sync and dumb it down a little for me. I always had an idle issue and using sync idle and its working great, but the transition to async is not.... and I would just rather disable than fix.

 

Try zeroing these two parameters (2-bytes each):

RBob.