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Question: My engine is LO3 TBI (peanut cam) converted to SD TPI. We’ve been using the 90-92 LB9 BIN (AXXB) as a starting point. If the info I have seen is right, the 90-92 LB9 (both auto and 5-speed) used a significantly different cam (L98) than the LO3. The 89 LO3 and LB9 with auto trans apparently used the same cam (also same as the 90 LO3); only manual cars got the L98 cam. I realize that the 89 used MAF so it may not be apples to apples, but it might provide some insight into why I’m having trouble with knock retard. GM never (AFAIK) built a SD peanut cam 305, so there really isn't a factory BIN to work from.
I've been fighting knock retard (gone through more than half-dozen tunes so far) and I got to thinking perhaps this is the problem. Unfortunately, my tuning skills aren't up to this task (not even close). I'm hoping someone here can provide some experience and/or suggestions.
Maybe I’m way off here, but I look for variables and this appears to be a significant one.
FYI: 1990 Firebird Formula, 18,000 miles, LO3 converted to 7730 ECM speed density TPI, heads/cam stock LO3, Hooker shorty headers/y-pipe, cat delete, AIR delete, auto, 3.23 posi.
The 89 LO3 and LB9 with auto trans apparently used the same cam (also same as the 90 LO3); only manual cars got the L98 cam.
No, that is out-dated information. All 90-92 TPI cars used the same better cam, both 305 and 350, both 5-speed and automatic.
My dad and I converted a 92 RS 5-speed from TBI to TPI keeping the same cam and heads. It went from 150 RWHP and 220 RWTQ, to 167 RWHP and 290 RWTQ. I don't remember any significant knocking issues though, even with 200k on the odometer. Perhaps your combustion chambers are just dirty from overall use and creating hot spots that lead to knocking? Or it could be something else.
Thanks guys. Long block is totally stock, 18,000 original miles, never molested, as far as I know (I have all service records for the car dating back to new). When I pulled the valve covers and intake to do the swap, it was amazingly clean. I don't think it ever went more than a few thousand miles between oil changes. I checked the knock sensor (new ACDelco) and got 3.9K of resistance. I even pulled it and re-torqued to 14 ft/lbs to make sure. EGR is hooked up and appears to be functioning (new ACDelco EGR valve and solenoid, just to make sure).
No, that is out-dated information. All 90-92 TPI cars used the same better cam, both 305 and 350, both 5-speed and automatic.
My dad and I converted a 92 RS 5-speed from TBI to TPI keeping the same cam and heads. It went from 150 RWHP and 220 RWTQ, to 167 RWHP and 290 RWTQ. I don't remember any significant knocking issues though, even with 200k on the odometer. Perhaps your combustion chambers are just dirty from overall use and creating hot spots that lead to knocking? Or it could be something else.
Thanks for the reply. Do you know what he did tune-wise? Did he do any data logging on this setup? I'm not actually hearing any knock, but the ECM is pulling timing with any significant throttle application. Maybe this is just the way it's gonna be, but it just seems to me that the LO3 cam specs are so different from the L98 cam specs that one tune aint gonna fit all. I would very much appreciate any details you can share, since this is right in line with what I'm working with.
From the data, it appears to be real knock being detected by the ECM. It's occurring between 1500 and 2500 rpm and map values generally above 50 kPa. The knock retard gets more severe with higher map as well.
What octane fuel are you putting in the tank? Don't the TPI cars need the premium fuel?
Also, your fuel trims could use a little work. The BLMs are not terrible, but they're getting on the low side (ideal is 128)
Base timing for TPI was 6 degrees advanced. Interested in your and Brian's results as I did this same swap some years ago and he also did some chip work for mine as well.
Base timing for TPI was 6 degrees advanced. Interested in your and Brian's results as I did this same swap some years ago and he also did some chip work for mine as well.
Sounds like our cars have a lot in common. I would be curious to know what you ultimately came up with, tune-wise. What injectors are you running?
I'm,using the Bosch 3 injectors as well from Fuel injection Connection, went with them after it was discovered the car was running on 5 of it's 8 injectors. I'm running the latest GM PROM with a few changes from Brian to sort out a few bugs (disabled AIR, AC request and EGR code 32). I've never datalogged the car, guess I need to get that done. I may contact Brian directly to see what he can do in my situation. If I can be of any assistance let me know.
That is correct for the LB9 and L98 engines. Not correct for the L03 engines. Recall the L03 has swirl port heads that do not require much spark advance. Which is actually why this thread was started.
I can tell you from my own experience with mine that when the base timing was initially set when we first started the car it was at 0 and the car would barely run. Injector issues aside the car did better when the base was set to 6 advanced. Even after the injector swap the timing was revisited and the car performed better at 6. A scan tool was hooked up while driving and no signs of knock were seen. Not disputing your input, just stating what happened with mine.
The initial/base timing in the BIN was likely at 6° BTDC. So with the actual base at 0° BTDC the timing was 6° less then what it was supposed to be. The code subtracts the base timing out, with the position of the distributor adding it back in.
Other then that, the base is only used during cranking.
The initial/base timing in the BIN was likely at 6° BTDC. So with the actual base at 0° BTDC the timing was 6° less then what it was supposed to be. The code subtracts the base timing out, with the position of the distributor adding it back in.
Other then that, the base is only used during cranking.
Note my remark in post 21.
RBob.
Is there any advantage/difference to just leave the BIN at 6, leave the base at 6, and adjust the SA table? I say this because it's pretty obvious that the AXKT was written with 87 octane gas in mind. Or, instead if one were to run, say, 6 degrees of base timing, set the BIN timing to 0, and use the AXKT SA table, the resulting timing would be AXKT table plus 6 degrees across the board?
Is there any advantage/difference to just leave the BIN at 6, leave the base at 6, and adjust the SA table? I say this because it's pretty obvious that the AXKT was written with 87 octane gas in mind. Or, instead if one were to run, say, 6 degrees of base timing, set the BIN timing to 0, and use the AXKT SA table, the resulting timing would be AXKT table plus 6 degrees across the board?
Like Bob is saying, base timing is meaningless, it's just a reference. He is more concerned with how the engine will start when hot, which is why he stated you can increase your base timing no more than 2 to 4* during cranking, otherwise it defeats the purpose to hone in on it as if it were anything else. Advancing the timing is mainly to get past ignition delay. The best way to do this is through dialing in the Initial Advance and controlled advance, not the Base/Initial. But again, doing this with an under powered and low flowing engine will be detrimental.
Like Bob is saying, base timing is meaningless, it's just a reference. He is more concerned with how the engine will start when hot, which is why he stated you can increase your base timing no more than 2 to 4* during cranking, otherwise it defeats the purpose to hone in on it as if it were anything else. Advancing the timing is mainly to get past ignition delay. The best way to do this is through dialing in the Initial Advance and controlled advance, not the Base/Initial. But again, doing this with an under powered and low flowing engine will be detrimental.
- Rob
Thanks, I'm just concerned about leaving a lot of performance off the table by running a low octance SA table. I guess you start conservative and work your way up, not the other way 'round. I will only be running premium, so hopefully I can work my way back up to a bit more advance. I'm only getting significant knock retard above 70kPa, and that's with SA that's allowing 40+ degrees. This new table reduces that by 15-20 degrees.
Thanks, I'm just concerned about leaving a lot of performance off the table by running a low octance SA table. I guess you start conservative and work your way up, not the other way 'round. I will only be running premium, so hopefully I can work my way back up to a bit more advance. I'm only getting significant knock retard above 70kPa, and that's with SA that's allowing 40+ degrees. This new table reduces that by 15-20 degrees.
Remember, GM did not restrict the LO3's timing table, it gave it exactly what it needed with the heads and valvetrain it was running. Increasing the table by 6* across the board will only hinder wide open throttle, because the LO3 makes its' power in the mid kPa and low RPM range. Once you consider larger cams, better heads, and higher compression, this is when advancing the timing will benefit you the most. Remember, the intent in advancing the timing is to get past ignition delay, and as horsepower increases, so does that need.
That is correct for the LB9 and L98 engines. Not correct for the L03 engines. Recall the L03 has swirl port heads that do not require much spark advance. Which is actually why this thread was started.
RBob.
The TBI heads should start at 6* just fine. My old L05 I ran at 10* without issue. My L31 cranking timing is also set at 10* in my Express van. A copd emgine likes a good bit of timing to start.
The timing map changes that need to be made need to be made in the spark map anyway.
I would use 6* because that was stock for a TPI and if it ever had to go through smog check it would need to be 6* of the timing was checked. California requires the base timing be checked for example.
Before I was burning chips I played with a stock TBI 350 G20 van by mechanically altering fuel pressure and timing. 14 psi and 8* BTDC had the best power on the dyno and no spark retard on 91 octane. It made 191 rwhp and 278 rwtq through a 700r4 in 2nd gear.
You will find peak power at 28-30* of total timing at WOT with Swirl Port heads and the stock cam.
The stock TBI van had 16* timing in the timing map and 4* in PE with no spark adder at high RPM (7427 PCM) and ran best at 28* total timing.
You will also find that the TBI heads like their maximum advance fairly low in RPM, probably no more than 3,400 rpm. Once you get over the highest VE and cylinder pressure at peak torque at 2,400 rpm the cylinder pressure drops fast and it will want some timing.
Thanks for the reply. Do you know what he did tune-wise? Did he do any data logging on this setup? I'm not actually hearing any knock, but the ECM is pulling timing with any significant throttle application. Maybe this is just the way it's gonna be, but it just seems to me that the LO3 cam specs are so different from the L98 cam specs that one tune aint gonna fit all. I would very much appreciate any details you can share, since this is right in line with what I'm working with.
I do my data-logging and tuning so yes we did. But I'm sorry its been so long I dont remember what all I did.
Remember, GM did not restrict the LO3's timing table, it gave it exactly what it needed with the heads and valvetrain it was running. Increasing the table by 6* across the board will only hinder wide open throttle, because the LO3 makes its' power in the mid kPa and low RPM range. Once you consider larger cams, better heads, and higher compression, this is when advancing the timing will benefit you the most. Remember, the intent in advancing the timing is to get past ignition delay, and as horsepower increases, so does that need.
- Rob
So now I'm wondering: should I just run the LO3 timing and then run 87? With the SA that conservative, it might actually run better on regular as opposed to premium. The heads/cam were obviously designed for regular as opposed to premium volatility. Unfortunately I just filled with 91, so I'll have to wait a bit before testing that setup.
So now I'm wondering: should I just run the LO3 timing and then run 87? With the SA that conservative, it might actually run better on regular as opposed to premium. The heads/cam were obviously designed for regular as opposed to premium volatility. Unfortunately I just filled with 91, so I'll have to wait a bit before testing that setup.
Remember that there are other areas in the bin that compensate for more, or less timing. This is why we just don't add 6* across the board and hope for the best, because you might see more in certain areas, as well as during certain temperatures, than you really want to be seeing at that moment. Just run the LO3 timing map, get a nice long datalog, and watch your timing in the analysis during different temperatures as well as RPM levels. Tuning the idle state with the controlled SA map is how we get the engine to respond the way we want it to, and no better way to do that than with a good datalog to base the data from, especially with knock being evaluated. It's never ever as simple as loading someone else's map because it worked in someone else's application because every engine and condition(s) that it is in is different. As RBob would say, give your engine what it wants...
Finally received my Burn2 so I could try my new BIN. Unfortunately, it seems to be hit and miss in terms of getting a good burn. First try I got brief start and die. Cranking just filled the air with gas fumes. Too rich to even start. Used a different chip and got it running pretty good, but most of my data log didn't record for some reason, so I only have a small sample. Kinda weird, I had put about 15 miles on it and, after turning a corner, I punched it and was greeted with stumble and it basically fell on it's face. It recovered after letting up on the gas and then ran okay. When I examined the .csv I recorded, it showed a spike in the timing of, get this, 23037.57 degrees. No that's not a typo. Obviously the advance then fell to near zero, which I'm assuming is why it fell on it's face. Had a few other instances of this happening during this 15 mile run. Could this be a problem with the chip burn? I've not ever seen this before today, and this is the first chip I've run that I burned myself. Happened once when I was doing a quick 0-60 run. Right when I throttled up from a stand-still, the timing did this weird thing. I have attached a screen shot showing the timing strangeness. I'm going to try and get a good data log tomorrow.
When I examined the .csv I recorded, it showed a spike in the timing of, get this, 23037.57 degrees. No that's not a typo. Obviously the advance then fell to near zero, which I'm
The SA went negative relative to TDC.It is the conversion of the ECMs SA value to something that we understand that is off.
The timing is based off axkt, If knock occurred during this snapshot the engine rpm was 1800 map kpa was 90.
Timing sa was 6.68 . Could the engine ping with this low amount of timing or could it be false knock ?
Question: Could a malfunctioning pickup coil or ICM cause this weird SA issue? I suspect my Burn2 is not working properly, as I burned a new chip this morning and I got lots of knock retard without much advance. But it cut out several times over a 10 mile drive, almost like you were cutting the ignition for an instant. I was able to get a short data log, which I have posted here.
Never mind. Just did a quick run with a known good memcal and it ran fine (other than some minor knock retard). No cutting out or hesitation. I think I got a bad Burn2. Probably why he was selling it on EBay.
Just did a quick run with a known good memcal and it ran fine (other than some minor knock retard). No cutting out or hesitation. I think I got a bad Burn2. Probably why he was selling it on EBay.
Meh, I enjoy playing with the old stuff every now and then. In fact, one of my co-workers, who is a game collector on the side, didn't believe me when I told him I had the original coins from Ultima 1, even the original warranty cards lol. Those games were awesome back then, still play Ultima 3 & 4 every now and then because it brings back so many memories, but they just can't compare to a faster processor, though. You know where I am going with this, just get an EBL-P4 and be done with it already...
Finally back to tuning after my finger has healed. Just FYI, don't get your finger pinched between frame and jack stand. Results in (at minimum) 5 stitches. Anyway, I have posted data log and SA tables for latest tune. Only about 10 miles on car prior to this data log, but it looks like I'm getting close. Just one real knock retard event when I jumped on it from a low RPM towards the end of the data log. Timing is still set to 6 degrees static (and 6 in the BIN). It seems to hot start fine, so I left it there.
Yeah, you're getting some retard going on (picture 1 below). My guess is you're into power enrichment at 95 kPa. But you're at 126 BLM (at 90 kPa) right before going into PE, so it suggests you're not lean when in PE... (picture 2 below)
How's your power enrichment spark advance? Is it stock AXXB?
PE SA is 0.00 across the board, so no, not stock AXXB. Major adjustment to the SA tables and new data log. Getting closer. Though I see that the "PE % change to fuel/air ratio vs rpm" is stock AXXB, and so commands -4.69 at 2000 rpm.
You're hardly getting any spark advance being commanded... Crazy... looks like you have less than 20 deg being commanded at WOT in the TPI power band, but you're still getting significant knock retard kicking in.
Though also at moderate load at ~3000 rpm. Are you sure you're not going lean? Could be getting lean knock.
BTW, if you delelted the Air pump, you need to zero out AIR O2 Rich/Lean offset... In Tunerpro, it's a Scalar entitled "AIR, O2 Rich/Lean Reduction Volts when AIR Divertered". The ECM uses the 100 mV factory value to offset the O2 rich lean threshold to account for the extra air being injected into the exhaust. If you're not running the AIR, you should zero this out.
04-08-2019, 11:58 AM
