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So as some of u know, I ended up discovering a few issues with my motor including oil seepage into cylinders and defective injectors. With the better weather, I have been able to get back out there to now datalog th car w the changes and fixes I did including new FIC injectors, so its back to tuning. However, I am still recording knock altho its not exactly like previous. Before I would seem to get knock almost on a random basis and at a steady cruise
and with little to no change in operating parameters. I now believe that was due to oil seepage causing the detonation. Contributing to that was one particular injector whose aerator had deteriorated and was basically
streaming fuel into the cylinder. That kind of knock seems to have been eliminated.
I have attached some snippets of my logs where the knock continues to occur but inspecting the plugs doesn't show sign of any detonation (I have attached some pics of two plugs, one from each bank). Once I started to log, it was clear that the previous tune had been very rich contributing to why the right bank plugs were black. Oil also contributed to this. I believe what had been occurring is that the left side was signaling LEAN and so it was forcing the right side to make up for it by richening the overall mixture. With the injectors now replaced I could go ahead and re-balance the VE table. I took out quite a bit of fuel. Of course since all other fueling is dependent or based on the VE, I suspect that now the AE needs to be tweaked and that may be the cause of the knock. I can induce knock by simply punching the throttle and I have a couple of examples of that. Also show a screenshot form TPRT w a before and after comparison w current bin v starting point and the amount of fuel removed. In fact, as I look at it, the area I am recording knock appears to be the same region of the VE where the most fuel was removed.
An added piece of information. lLatter C4 Corvettes w ZF6 trans came w dual mass FW due to the square cut of the trans gears and heavy duty nature of the trans, especially Black label ZFs. A popular mod is to replace w a SM Fidanza. At idle the trans rattles depending on state of tune.
Last edited by Dominic Sorresso; 04-27-2019 at 11:50 AM.
Putting this extra image due to lack of space up above, but this shows that the most fuel reduced from the initial bin appears to be in the same region of the VE table as where the knock occurs. That leads me to suspect AE even more.
No motor is not stock. Ported top end and heads. Stage 2 Intake and Exhaust cams, headers. ~ 454 to the wheels.
I am sort of talking out of both sides of my mouth. In one instance, at least a part of the evidence suggests I am dealing w false knock. On the other hand I am discussing adding AE fuel because of real knock.
Last edited by Dominic Sorresso; 04-28-2019 at 01:30 PM.
The data doesn't seem to suggest that AE is the problem. I'm seeing knock counts and retard occuring without any changes in TPS%.
It seems to be real knock... low rpm, moderate to high load, with the amount of retard increasing with load.
Aside from ensuring the EGR system (if you have it) is working, probably want to decrease the timing and see if the problem goes away. This would verify the knocking condition is real.
If it's in fact real, then the question becomes what to do about it...
My 8D background.... we have both delta-TPS and delta-MAP AE...
Well, even in the data excerpt that's highlighted yellow, the knock is occuring while you appear to be letting off the throttle... and as the load decreases, the knocking does as well.
Also I still see areas where you seem to have constant MAP but still getting knock...
I'm attaching the whole datalog. Sheet 1 is just of the relevant parameters.I know I can induce knock by jabbing the accelerator. The latter examples of knock are in fact where I purposely did that.
I can see that at lines 20048 and 27777, where you stab the throttle....you immediately induce some knock.
In other instances it seems to occur at steady state... at moderate to high MAP.
Do you have a WB O2 on the car?
I do have a WB. I have compared the current bin w the stock tables, and I can see that there is significantly more advance in the current tables. Going to go back to those tables or significantly reduce the current ones particularly in that area of the SA table. We'll see if its ral knock or if may be what RBob suspects.
Have reviewed the posted log in some detail and have some general comments. But before that, is there possibly a more detailed log that could be posted showing everything logged, such as spark, MPH, coolant temp, etc.? This would help in correlating events.
In summary, I agree with ULTM8Z that most of the knock occurrences reported appear to be at a steady state. Very few appear to be under any significant load, which is when one would expect true knocks to occur.
General Observations:
No knock occurred during samples on lines 1-9853. Assuming 15 samples per second (don't know exactly because time not available), the first knock would have occurred at after approximately 11 minutes of driving. During that time, TPS%, RPM and MAP maximums were respectively: 20.3, 4300, 83.4. Certainly an opportunity for a knock if true load occurred. Then on line 9854, with a drop in TPS%, RPM and MAP (note "drop"), a knock is reported. That by itself would say your knocks are from something other than load on the engine.
The next knock is reported 3,000 lines later, or a little over 3 minutes later, and then frequently thereafter. This would point to the engine possibly being hotter, assuming no change in driving pattern (unknown), and not spark since the same spark table was used during the first 11 minutes.
Also, assuming your mask ($d0, $D0A???) is similar to other GM masks, fast knocks are accumulating, waiting until 255 fast knocks occur whereupon a slow knock is reported. This is seen several places in the log all the while knocks remain reported at '2' (lines: 9866-9873, 10142-10446, 10976-10978). We also know from this reporting that knock retard is based on fast knocks and not slow because there is retard at the lines above without a reported knock.
If you could post a more detailed log (everything logged), perhaps more could be gleaned.
Also, assuming again you mask is similar to other GMs, you could hopefully determine from your ADX the byte used to report knock count (or perhaps RBob might know). Then change that address to current value + 1(hex). Using $8d as an example, Slow knocks are reported in 0xC1. Fast knocks are accumulated in 0xC2. So fast knocks would be reported 1 hex byte higher than the address of the currently reported slow knocks (0xC1[slow] + 1 = 0xC2[fast]). Reporting fast knocks may shed more light on what's going on when they occur.
OK. Well finally got a chance to try out new cal w SA table much closer to stock than previous. Made no change to AE. I have attached a .csv file of the entire run which is consistent in length w other logs. And I have highlighted areas of knock retard so u wouldn't need to hunt the whole log but it does include all of the ALDL params. Steady cruise showed no sign of knock retard. The nock u will see is basically induced from my jabbing the accelerator.
Frankly the car seemed to run and idle smoother overall. The motor was quieter and had a purr to it. Still some areas where fuel needs to be adjusted.
So how much knock is it OK to "tolerate"?
Last edited by Dominic Sorresso; 05-06-2019 at 04:59 PM.
IF you're getting knock on sudden throttle transitions, have you tried richening the AE fueling?
I just datalogged another cal where I bumped up AE. Still getting some KC even at “steady” cruise but the burst knock happens with jabbing the throttle. Again,however, the amount of knock is radically less w the reduction in SA. I’m also looking into whether the PE may also need some tweaking. Incredibly, most of the knock happens right at around 1900rpm.
I’ll post the log shortly.
Here's the latest log. As u will see almost all knock is in the 1900-2000 rpm range and at 55-70kPa. There is a burst of knock at basically WOT but again right around 2000rpm. And the SA for those cells is stock.
I have reduced the SA for the next cal by another degree in this area of the SA table, but left the SA at 90-100kPa as it is for stock. However, I did raise AE by 10% as test.
I have attached a distilled log of just the relevant parameters, and then another reduced further to show just the cells involved w knock.
So took car out again today w cal that bumped AE by 10% along w small changes to SA in affected areas. Pretty much eliminated steady cruise KC. And frankly, I think the motor likes the additional pumpshot. Throttle response appears better by SOTP. I will probably bump AE again particularly where I could still induce some burst knock altho it was more difficult to do so than before.
Would love to get this thing on the dyno finally for some WOT tuning.
I don't know if it's just the Miniram, but yeah I've found that the engine really likes more delta-TPS AE than delta-MAP AE. I started with the LT1/LT4 AE tables and ended up a little richer (probably about 10%) on the delta-TPS, but about 10-12% leaner on the delta-MAP. The opposite didn't work and actually felt more sluggish.
I'm not sure why that is, but after A LOT of testing, that seems to have gotten the best result.
What's also interesting is that the effect seems to carry through to long after the AE is duration is over... the car seems to actually pull harder long after the throttle transition is completed. I don't know if it's my imagination or not, but it's again it's a seat of the pants feel.
What I found in tuning WOT is that proper AE sets up the rest of the run. If the AE gets the AFR to a point u need as PE takes over, then the ECM intervention is minimal. You get a nice steady AFR close to what ur looking for w the motor.
The LT5 REALLY breathes. It will suck the vinyl covering off a 3 ring binder if u try using that to block the TB for a vacuum leak test. And that’s just at idle. Ask me how I know. ��
Of course the other thing is that w the reduction of VE, I have now needed to adjust the AE pumpshot to compensate.
What I found in tuning WOT is that proper AE sets up the rest of the run. If the AE gets the AFR to a point u need as PE takes over, then the ECM intervention is minimal. You get a nice steady AFR close to what ur looking for w the motor.
Agreed... from my experience.... Even though the 8D (in my case) is effectively "open loop" during PE, yeah the AE seems to "set the tone" for how well PE behaves...
FWIW, here's my take having looked at the zipped log in Post #13 (2019-05-06_15.23.43.xlsx). The knock retard is not 100% produced by increased load due to throttle taps/TPS & MAP increases. Rather, it appears there is something mechanical causing a rattle the knock sensor is reporting. This is borne out by looking at retard activity beginning at rows 14566 and 15919.
At row 14566 it appears you are cruising at 83 MPH with constant:
TPS%: 14%
RPM: 2050
MAP: 63
REF SPARK: 18.6-19*
Ditto at 15919 cruising at 55 MPH with constant:
TPS%: 17.5%
RPM: 2050
MAP: 70-71
REF SPARK: 17.5-18.5*
The same thing as above is noticed in the first 2 retard occurrences of the later 2019-05-07_14.03 Knock 1.csv log.
IMO, there is just no way load induced knock caused the retard recorded at those times. Has to be some other vibration, and as you stated in the 1900-2100 RPM range. Granted there would appear to be load induced knock at all the other places retard is reported, but I believe that is also vibration related because during all knock retard incidents, spark only averaged about 17.5*.
Having said all that, if the cruising incidents above are in fact load related knock, then spark is indeed too high across the board.
PS ---
Left BLMs are consistently lean, and especially lean at closed throttle.
Thanks for having a look Elky. Mechanical noise has been my suspicion. The ZF6 trans was used w a dual mass FW. One of the more common upgrades is to replace that 35#s of rotational mass w a single mass aluminum 13# Fidanza FW.
The ZF is a noisy trans being heavy duty. However, in subsequent datalog sessions, I have been able to basically eliminate the steady cruise knock ur seeing through a reduction of SA and by increasing MAP AE. What I noticed was that even slight change in MAP, 1-2kPa was enough to bring KC. Yesterday I did a datalog which had no KC at steady cruise speeds or when I would lightly accelerate. Even jabbing the accelerator produced just one knock incident.
As for the split BLMs, its pretty typical of the LT-5 especially at low rpms. Yes the left side is typically leaner than the right. My motor also has intake and exhaust cams. Higher rpms bring the BLMs closer into line w each other.
The combustion chamber on the LT-5 is of course much different than what we see on typical SBC. And we know that the better chamber design needs less SA ala the LSx architecture. Comparing my previous SA tables to stock, I did have too much advance. Not necessary. In fact, SOTP, the car feels noticeably more responsive now with lower SA and more AE.
If you get it down the final tuning stages and getting knock at or near WOT and not sure if its "Real" or not, simply increase the octane of fuel significantly and re-log your data run (octane booster or race fuels)
It may be hard to believe, but I actually think I have arrived at a final tune. Really running well. Very few changes needed for VE tables and of the changes needed we're looking at BLMs off by +- 1 from target for the most part.
Any KC came from me either lugging the motor in 3rd gear from a light, or jabbing the throttle to 100% TPS several times. Otherwise nada.
As always, there will be something that pops up to conquer. Maybe I can take a break. Yeah sure!!!!
It may be hard to believe, but I actually think I have arrived at a final tune.
Glad you solved it. Would be interested in the final maximum spark advance you used, because previously REF max seemed to be around 33.5*. With minimal 6* base, that would be approx. 40* TDC.
Glad you solved it. Would be interested in the final maximum spark advance you used, because previously REF max seemed to be around 33.5*. With minimal 6* base, that would be approx. 40* TDC.
I really don’t get KC in the higher rpm area. It pretty much was in the area of 1800-2400rpm and 45-70kPa. Higher than that and no KC. The LT5 isn’t really prone to knock. However, when tuning WOT, You will run into Knock right around torque peak, which is ~ 5300rpm on my motor. Beyond that, I can run 30* + the Ref w no problem.
For the part throttle tuning I have been doing now, I have probably taken 4-6* out of the previous calibration. That combined w
a minimum of a 15% bump in AE seems to have resulted in a pretty responsive motor.
I did a couple of plug pulls. And where the right side was rich v left side lean, things have evened out much more so now.
The left is still leaner than the right, but its much more in the same coloring ballpark than previous.
Part of the coloring is going to be due to richer cal that I started w. I should really put in a new set of plugs just to see where things stand currently.
pictures 3 and 4 are not doing well. Are you using anti seize on threads? Any lubricant?
This is more what you want, these plugs are 'done' but the color is ideal for the mileage, wear and tear, clean operation.
Basically notice how white and tan the centers are. I get these tan spots on an otherwise chalky white center porcelain in the LS engines, Nissan/Toyota engines give plugs that look the same exact way minus the tan spots. The 'ring' is carbon'd up all black, but without any sleek oily slimy looking gloss. Its just a dull flat black ring of carbon.
Your pictures make me think oil is getting in there, or it ran really rich for a while and fouled up the plugs at some point.
This is why I typically do all my tuning on CHEAP COPPER plugs, then switch to the expensive iridiums once the tune is dialed in and dyno time.
I don’t disagree w u. It was running rich and I had put the iridiums in b4 really doing that. I’m thinking of cleaning a spare set of copper plugs just to see how things are actually going. My oil consumption is about 1qt/900-1k. Expected in this motor. Plus running anlittle hard accelerates oil consumption.
However, the motor feels very strong and datalog looks very good. Not sure what to make of it just yet.
There are 5-6L engines making 800rwhp that don't consume oil, whats wrong with the engine you are using needs to be fixed first.
If its oil on the plugs. That will cause knock. I'd say make sure you don't have oil in the combustion chamber, no excuses for that
I normally dont recommend taking apart engines and getting invasive, but honestly if I had a gross oil soaking cylinder motor I would
1. fix the issue or terminate the issue first
2. dismantle the head and thoroughly clean everything including pistons and ports of everything
My friend has a 5.3L with gapped as ufck piston rings, like 0.030 top or something. It smokes when fully warm.
but it does NOT consume oil at any appreciable rate. We run 22psi on pump fuels and its just happy smokin but no oil use.
You may have oil seeping through head studs or through the rocker studs or something like that. From above rather than rings.
Unless you know already its the rings.
Either way, gota be fixed then cleaned bro
DO you have the PCV hooked up properly? One side fresh air behind air filter, other side after pcv valve in valve cover to intake manifold. The suction of PCV system during cruise/idle helps the piston rings seal. It will reduce blow by.
1qt/1k miles is not unexpected in these motors. When I worked for BMW for example, the tech guys would look at complaints of oil usage after 6-750mi and declare it “normal”. The LT-5 really doesn’t use much oil unless u r flogging it. Not unusual to go to the track, do a number of runs and then be down a quart. During my datalogging, I am running the motor to 4k, then holding it there. I will do this usually in 1st, 2nd, and if possible(due to traffic) 3rd gears to get data in those cells.
However, I will be installing new plugs and then gage the status of things based off those readings.
BTW, LT-5s are DOHC motors. No rocker studs, compression is in the 220+ for all cylinders, fuel pressure at the injector is ~ 48psi. The motor does not smoke altho I may get a puff when I jump on it.
I’ll take another check of PCV system. I am using a catch can in the PCV circuit.
Last edited by Dominic Sorresso; 05-18-2019 at 09:38 AM.
The bottom line is, if there is enough oil flow that it shows up on the plugs at all. Its too much. Need to figure out where its coming from and fix it.
I am not saying that some factory engines don't blow oil, but its definitely not "normal" in the sense that the factory intended it that way. More like they screwed up and decided to just ride it out and call it normal.
Its a common sense thing in the performance world that oil is going to completely F@#(*$ your power production, combustion quality, engine operation if it gets into the chambers.
I’ve taken some steps to try and eliminate some potential sources for oil entering the combustion chambers. One thing of note is that previous, the 2&4 cylinders were exhibiting this kind of plug marking. Now all cylinders w the exception of #7 seem to present w similar combustion markings.
Today I did some work on the crankcase venting system by re-doing my catch can w new baffling, and 2, I pulled both PCV valves for cleaning. I did note that they did not rattle freely. Gave them a few squirts of bake cleaner to free them up, and now they both sound quite a bit looser.
Take it out for a ride tomorrow and we’ll see if there’s any improvement otherwise next step is pulling the motor. Pretty much out of ideas.
Keep putting in cheap $2 copper plugs and cleaning up the pcv system, perform a pressure test, inspect all the lines and route. Make sure you have idle pcv action and that the fresh air tube has a proper restrictor installed if you've modified the pcv system. For example when installing a "catch can" type of system many people do not realize that it may negatively affect PCV action, either by disturbing the system with excess volume/container or by creating a stagnant location for crankcase byproduct to collect abnormally (condensation during cool-down periods for example) or merely removing the necessary components that cause PCV to work properly such as the meter-restrictor for pcv flow.
Make sure it looks something like this at least:
Forgot to mention that I did replace the Iridiums for now w just a new set of BKR5E gapped at .044”. Wanted to get a clean set of plugs to see what things look like for the next rounds of datalogs. I figure that if the 5Es show improved combustion after these changes, then I can swap the Iridiums back in knowing that combustion is good.
The fact that now it appears that just about all cylinders exhibit the same type marking has me thinking its an issue w the oiling system rather than one or a particular set of cylinders, ie right or left bank.
Took the car out and datalogged. Really running nicely altho need to back off on VE a couple of percentage points.
Getting no knock at cruise where I had before. However, still concerns about oil usage. Before this run, I added some steel wool as a collector for the catch can. Given now that practically all cylinders are presenting a similar burn pattern on the plugs, I beginning to suspect crankcase pressure as the cause of oil getting pushed into the cylinders. Besides the PCV, which I cleaned w brake cleaner before reinstalling, both cam covers also have vents to the airhorn. I may need to pull them to check on the filter material in them and whether that may be clogged.
thanks for updates, Ill try to make useful suggestions if I see something,
heres what I got so far,
1. make sure you are using the OEM pcv valve and only 1of them
2. might suggest you perform a pressure test to ensure proper PCV routing flow (use an air compressor to make sure "blow by" simulated by the air compressor, is all going the right places) i.e. you may have a leak
3. What the heck is a cam cover and what is an air horn lol
4. If you get a chance, take the new plugs out (or just 1 of them) and snap a picture of the 'worst' one so we can all determine how bad the oil situation is
It uses 2 PCV valves. The cam covers act as part of the cam support system. and they vent into the airhorn which is in front of the throttle body. There are vent tubes in each cam cover which lead to the air horn for open air breathing.
You can see one of the vent tubes from front of cam cover leading to the airhorn. The motor produces a lot of windage and crankcase pressure at 7000rpm. I’ll take pics of plugs from both banks in a few days. The ones I took out were a medium bronze color this time after about a 65mile run. The datalog did indicate n overall running somewhat rich mixture. However, the one thing that raised my suspicions is the dipstick was not completely inserted in the tube. That’s either a sign of pressure or my absentmindedness after checking oil prior. Regardless oil level did drop on dipstick after checking. I looked underneath and did not see any oil around the pan or towards th back of drivetrain.
something is missing, lets see if we can figure this out,
The PCV valve directs crankcase vapor into the intake manifold suction.
That means it would lead from the pcv valve, into the intake manifold, somewhere after the throttle body.
If you have any pcv valves feeding a pre-throttle body space, this is incorrect. For starters.
I see that hose in the picture, leading from the valve cover, to the pre-throttle body space. It likely does NOT contain any pcv valve, and if it does, we need to figure out why
something is missing, lets see if we can figure this out,
The PCV valve directs crankcase vapor into the intake manifold suction.
That means it would lead from the pcv valve, into the intake manifold, somewhere after the throttle body.
If you have any pcv valves feeding a pre-throttle body space, this is incorrect. For starters.
I see that hose in the picture, leading from the valve cover, to the pre-throttle body space. It likely does NOT contain any pcv valve, and if it does, we need to figure out why
The way I currently have the PCV system configured is as stock. As it came from GM aside from having added a catch can in the circuit. Crankcase venting runs thru the injector housings on either side which then feeds into the PCV valves onto the catch can then connected to a port in the airhorn ahead of the TB. The cam covers also have vents up front which feeds into the airhorn from both covers. I am now suspicious of those cam cover vents which coincidently(?) are adjacent to the cylinders presenting the burn pattern suggesting.
The attached pics show pairs of plugs comparing left v right banks ie 1-2, 3-4 etc.
oil during combustion.
I can't make heads or tails of your pcv situation. I can assure you all engines work the same way, please look at the picture and whether your engine is 4-cylinder or 8-cylinder that picture is accurate.
IF I was standing there. I would first use compressed air to investigate the existing of two pcv valves. Then check every orifice for where the passageway leads.
Then Initially for diagnostics, set all the pcv ports as fresh air vents with no pcv valves. Eliminate the pcv and intake manifold suction.
Now, run the engine and measure crankcase pressure using a gauge with accurate +/- 2" Water. The appearance of existing high pressure and smokey pcv tubes while running is an indication of piston ring or cylinder issues.
If the engine has good rings/sealing cylinder suction then there will be very little appearance of pressure in the crankcase while the engine is set to vent.
This test could be repeated at moderate output, for the appearance of oil and pressure rising beyond acceptable level.
The results of that test tell what to do next. If there is high pressure I use a next engine because this ones got bad rings/cylinders.
If there is no pressure, add one single pcv valve and a suction draw to the intake manifold and monitor that line for any oil.
If no oil appears in the intake manifold suction line, and there is adequate crankcase pressure, then there is only one other way for oil to get into the combustion chamber. Directly from the head, leaking down through a crack or valve seal or threaded studs. Because thats all 3 places: ring/piston damage, intake suction baffle, or direct from oil supply of the head.
Every engine. there is nothing 'special' about this engine that it doesn't follow these rules and setup, I think maybe the original engineers made it seem complicated for who knows what purposes. But its an engine with a piston, and that means one thing: you measure against the pressure the piston makes to determine cylinder seal.
yeah dude im totally confused. beffuzlles and what not. they did a good job obfuscating any hope of understanding which tube does what or goes where, made it all 'secret pcv flow'
I do that sometimes too. "my engine has special tanks and tubes" is a childish way to engineer something though. Elegance vs Extravagance. They could have achieved the same functional effects with far less superior ingredients, much less flash and still do the job. And then on top of that it looks like fate punished them and the system manages to become unreliable after all.
To me it is a circle of poetry, even if none of it was true
Apologies btw. The PCV line DOES connect to the plenum portion of the intake, behind the throttle body. However, the cam cover vent output to the airhorn. Sometimes you’ve worked on this thing so many times and think ur positive about details.
So hopefully an important update on this. I have been tuning using an Ostrich2 and the G2 daughterboard. The other day a thought occurred to me about confirming that I am using a correct prom to be used w the daughterboard. The 91-96 proms have a knock sensor circuit on board the prom. However, the circuit for the L98/LTx motors has a different frequency sensitivity than the one for the LT5, for obvious reasons. I decided to try a different and known memcal for use w the daughterboard. I saw 1 knock count on my scanner during a 1hr drive. I made certain that I drove the motor in that specific rpm/map area where I was recording knock in previous logs. This time no knock. Only 1KC in the entire 1 hour drive and none in the hiway cruise where knock was occurring (1900-2400rpm/45-70kPa).
I am not certain that the Knock sensor circuit board on the prom I was using was incorrect because when I went to pull out the daughterboard from the ECM case, I also noted that the header pins on the daughterboard were ever so slightly pulled away from the bottom of the prom carrier.
My next step is to bump timing in that specific area and see if I register knock. That will tell me if I in fact have found 2 possible reasons for registering knock counts altho the plugs do not show evidence of it.
If I reinstall the memcal I had previously been using, that could help me eliminate or confirm whether it was the knock circuitry or simply memcal not properly installed on the daughterboard.
I am not certain that the Knock sensor circuit board on the prom I was using was incorrect because when I went to pull out the daughterboard from the ECM case, I also noted that the header pins on the daughterboard were ever so slightly pulled away from the bottom of the prom carrier.
.
Take a look at this. I know you don't have this setup, but similar occurrence. All of a sudden I began to see rolling knocks even at idle. Decided to pull the ECM because was certain there had to be a loose connection. Found the MEMCAL was barely plugged onto the G1 adapter. In fact if was about 50% plugged in on one side and almost totally unplugged on the other end. I must have pushed the MEMCAL away from the G1 when installing a chip in the ZIF socket (not shown). How it was even running I don’t know. Looked just about like this:
Snapped the MEMCAL firmly onto the G1 and all OK.
Proper connections to the ECM are absolutely necessary..
Mine not quite that bad but similar in that the end was pulled out further than the rest.
So I went ahead and bumped timing in that area of SA table. Got a total of 3KC pulling timing of 1* or less for 2-4 frames. This was for about a 1hr logging session.
I’ll need to put in previous memcal w suspect Knock circuit and current cal to rule anything in or out.
Took the ZR to datalog yesterday w same SA tables but using the prom w the suspect Knock circuitry. First of all, it looks like it wasn’t about how the prom was mounted on the G2 board. This time it was solidly in place. With the “known” memcal,
I got 2 KC for the same or longer datalog. Using the suspect memcal, I got 13 w almost all of those coming in the same
1900-2400/45-65kPa area. Definitely can induce it when I jab the accelerator in that area, but also when there is no change in TPS or MAP.
I’m going to try one additional test where I am now bumping the SA table by +2* in that same area. But I will be using the “known” memcal. With the “known” memcal, I got only 2KC, and not in the same area, using pretty much the stock SA. Now having increased by +2*, we’ll see if the motor will take the additional spark without appreciable increase in KC.
Just ran across this older thread and thought I would update for all. I believe 84Elky said he thought the knock was a mechanical noise not detonation. And he was correct, and it wasn’t the muffler hanger. Its a bit of a long winding road or read, but it turned out to be crank wobble. A couple of years before this event, I found a compression ring broken in 4 places. We replaced it and thought that was that. The cause of the cracked compression ring turned out to be an injector whose aerator had disintegrated, spewing a stream of fuel into the cylinder. This created a lean condition in that cylinder, causing detonation that I did not hear. Apparently, the detonation had been going on for a while. When we tore down the motor recently we found the front and rear main bearings worn but on opposite halves of the bearings, ie front upper, rear lower. IOW, the crank was wobbling vertically and at 1800-2400 rpm, it would produce a noise to which the KS is sensitive to. Ergo, knock and knock retard.
A newly rebuilt shortblock has now been installed.
04-27-2019, 11:41 AM
