The car was originally TPI. But I think it was just a bad motor, I checked the a/c blower motor voltage when it was turned on and it was 12.5 V so I was getting voltage. But here is where it gets even more confusing. I bought a new motor plugged it in outside the housing and the motor turned on when I turned it on, but when I put it in the housing and plugged it in again it would come on and I checked the voltage and its still 12.5 V. So I thought that maybe it was somehow binding up, but there is a hole is the motor where a vent tube comes in, and I spun it through the hole and it spins freely. I guess I'm going to have to pull the motor out and try another one maybe.

Another bigger problem I have been having with the car is losing fuel pump voltage. Sometimes when I am driving the fuel pump voltages just drops to zero. I guess it must be grounding out or something. It's completely unpredictable, sometimes I can drive the car fine and it maintains voltage, other times I will be driving for 5 minutes or 30 minutes and I just shuts off. When it happens I just leave the ignition on and after 10-15 minutes sometimes less the fuel pump kicks back on and I have fuel pressure again. I replaced the relay but I still did it, any ideas on where to start looking to fix it?

 

What´s the significance of the Option Word 4-Bit 7-EGR in tunerpro ? Is this to enable or disable the complete egr-system or what does it means ? Should I do some changes on the egr-system after ve-learn or should i
leave it stock ?

Thanks a lot !

 

so this is a bit out of the norm of questions here (I'm a 4x4 guy running the ebl) but any idea or reason why I couldnt use the a/c circuit (not running a/c in my rig) to kick up my idle while I'm winching or running my york air compressor which is in place of the a/c unit?

 

Option Word 4-Bit 7-EGR is important. The reason is that the EGR output pin on the ECM has a dual purpose. It can control a wet N2O system, or an EGR valve. But not both.

With the bit un-checked the EGR output is for N2O control. Checking that bit sets the EGR output for EGR control.

Also note that Option Word 4-Bit 6-EgrNC sets the EGR solenoid as normally open or normally closed.

If using an EGR system, once the VE table is good, enable the EGR and do VE learns. Do not use the resulting BIN. Look at the learns (via BLMs) and adjust the "EGR - BPC Multiplier vs VAC" for a minimal change of BLM value.

RBob.

 

The A/C request input can be used. It has an idle RPM adder that will increase the idle speed with a +12 volt input on that pin (B8). Need to be careful if an auto tranny is left in drive. A secondary affect is that if the ECM is controlling an electric fan, that will be turned on. Which may be a good thing.

There is another method. Pin B9 is dedicated to command a high idle. With pin B9 grounded and an automatic trans is in park/neutral, the engine RPM will be commanded to this value:

IAC - B9in Idle Speed

A stick tranny in the calibration isn't checked for park/neutral, just the auto (for obvious reasons).

RBob.

 

very cool.. thanks for the reply.

 

Ok, thank you. I understand. So, i should set enable option word 4-bit 7 to use my egr. I was wondering because this option in the lo3 federal stock bin isn´t set, too.

I´ve got other questions, too. What´s the difference between "Zeitronix" and "Zeitronix lnr". What should i normaly choose to use my ZT-2 ?
I don´t understand the "Learn LED" in the WUD. It shines although i don´t drive VE-learns. Is this normaly ?

 

The orignal Zeitronix is a non-linear output. There is a lookup table in the WUD for it. Then along the way Zeitronix showed, or changed their firmware, so that a linear output could be used. IIRC it uses the simulated NB output for the linear version.

This is what the Zeitronix LNR is for in the WUD. The linear output model that they document.


The indicator lights in the WUD are from the ECM. The learn indicator is when the ECM is in BLM learn mode. Note that the ECM may be in closed loop, but not learn. In closed loop the INT will move and the prop gains are active. However, the BLM will not move.

With just the right qualifiers it is possible to go into BLM learn mode without being in closed loop. This accomplishes nothing. If the INT won't move, neither will the BLM(s).

Also note that closed loop may still show active when in PE mode. Although it isn't really active. This is because PE mode is a special short term mode to drop out of stoich and command a lower AFR. Then go right back to closed loop skipping the qualifiers.

RBob.

 

I want to ask, how i know, is my egr normaly open or closed ? Should i enable or disable the option word 4-bit 6 ?

What´s an asynch mode ? How works it ? What makes it ?

Thanks.

 

https://www.thirdgen.org/forums/diy-...nc-thresh.html

That thread explains synch asynch fueling.....

 

Newest tune...emissions. I'm not passing them so far. I found that my cat is trash after 4K miles, so evidently that happened while I was learning to tune. It never really ran lean or too rich, so I'm assuming it was it's because it's a cheap cat and I beat the truck every time I drive it, so I guess it is "rich".

Anyway, put a new cat in and luckily I have access to a 4-gas analyzer. I installed my NBO2 and evidently there is something wrong with it because it reads lean when in fact, it is rich. This could be a prop gain adjustment I guess, but the sensor is a Bosch sensor out of a Kia and I'm not sure if that in itself is a problem. After I noticed what was going on, I put the bin back into open loop.

At first, I'm passing idle emissions with flying colors, but failing cruise by a lot. I try leaning it out to the point that it surges, and then added some fuel back. When I hold it at 2500 rpm, sometimes it coughs and dips below 2000 when the pedal position hasn't changed. Also, after removing fuel from the VE - high table only, now I fail idle due to too much fuel. Why? I don't understand why adjusting only the high table would affect the idle while running open loop.

After the batteries in my laptop died, I started looking at other things. At idle, the fuel pressure on my VAFPR was only at 6psi. I'm not sure why, but when I set it initially it was at 11. When I rev the engine up, the pressure goes up to about 15, then back down to 11. I know the pressure isn't linear on these things, but that doesn't sound right. Possibly the reading is skewed because the engine is free-reving??? If I disconnect the vacuum line, the pressure goes up to 18 as it should. The pump and aeromotive regulator are new within 4K miles. The vacuum reference for the regulator is tee'd into the same line as the MAP sensor since I believe that is the only manifold port off of my Holley TB (injectors are GM 74# injectors).

Any ideas or things to try?

 

As you may be aware T to MAP sensor is a big no-no. Locate the R angle fitting at manifold to brake booster. Drill and tap a nipple.

My Aero shows 20 disconnected and this morning was 10.5 connected. I idle today at 39kpa at 775 rpms with manual trans.

02 sensors are cheap I would replace with GM Delco.

 

I've heard arguements both ways regarding where to connect the vacuum source. In the end, I've always felt that vacuum was vacuum and it shouldn't matter where I connect it. I'll probably still change it since it's definitely not going to hurt.

What does your fuel pressure do when you free-rev it in park? Obviously not under WOT conditions, but maybe up to 3K.

The only reason I used this particular Bosch sensor was because I also had a water-tight plug to go with it. The old sensor was unheated, so the connector only held one wire.

I read on the last page that it's difficult to pass emissions in OL mode. Why if the fuel is correct?

 

I have no clue what is going on. My Dad, the old-school drag racer, says I need to dump the TBI and switch to carb. Each day that passes, I find more stuff that isn't working right and I'm starting to think he's right.

Used the gas analyzer today and noticed some more things. It's still rich. If I multiply the high-VE table (since I'm trying to tune at 2500) by .9 (removing 10% fuel), it surges. I don't understand why, but I did a datalog and saw something else I don't understand. When it surges, the sync PW drops to 0, and one time frame later, async squirts some fuel (1.7 ish). The VE is 30, MAP is 29-30, RPM is 2400. Sync PW before this happens is 1.25, but the constants for async tell me that there shouldn't be any async at all. I haven't touched the tables from the original EBL bin, but here they are:
async transition lo:503
async transition hi:701
async high rpm: 6375
async low rpm: 6375
async high map: 99.69
async low map: 99.69

What the hell is causing this?

Another thing I noticed. When I'm failing emissions miserably (5-6%) and it's not surging, the sync PW is only 1.3. How is there that much fuel if the PW is only 1.3? I'm thinking too much fuel pressure or my BBC injectors are just too large for my fuel requirements. They are only 74#, which is only 6 lbs more than the original injectors.

I haven't moved the vacuum reference yet, in case anyone is wondering.

 

It is difficult to pass emissions in O/L as the cat-con isn't happy. This is why when in closed loop the AFR oscillates around stoich (or close to it). The cat requires the constant rich/lean change to operate. This oscillation is part of the fueling algo, it is done on purpose.

For drag racing only a carb would be fine. But I don't think it will come anywhere close to passes emissions. Unless an electronic Q-Jet is used. But that brings other issues to the table.

For figuring out emissions, you need to look at all of the gases: HC, CO, Co2, and NOX to see what is really going on.

High HC can be from either too lean or too much spark timing or both. High NOX is from no EGR and/or too much timing. High CO is from incomplete burn.

To disable the async injection mode zero these two:

async transition lo: 503
async transition hi: 701

The reason the sync PW seems to be too large to go into async mode is: the WUD reports the total PW, after all compensations have been made. This is the PW as programmed to the injectors. The async transition parameters operate only on the fuel portion of the PW. That is the PW from the fueling calc, before the compensations are made.

RBob.

 

So how does that cat work on a carbed vehicle? Different guts?

My Dad is certified in emissions and he only said it was way too rich, so I guess the other numbers are in line. He said it's showing that it's way too rich, but said the PW didn't make sense because it's not dumping that much fuel in. If what WUD is showing is different than what the injectors are firing, then that could explain it.

I'll try disabling the async to see if that helps, but do you think there is an area of the PW formula that is off just enough that when I try to lean it out it turns the injectors off?

 

Carb'd vehicles have different emissions requirement levels. The factory jumped through hoops to get things to sorta' work. The biggest gain was with greatly (!!!) reduced timing. Then came the 'E' carb's with the MCS's and all kinds of thermo-vac switches. Remember those cars? No spark advance, no compression, no power and no fuel mileage.

And yes, the guts in the cat's have changed over the years.

The WUD shows exactly what the injector PW is, at the injector.

I would suggest that all gas PPM's be posted. You can't look at just one.

Maybe there is a lean misfire, which will drive the HC through the ceiling. Too much spark advance will do the same, drive the HC through the ceiling..

Disabling async will get rid of the surge.

There is nothing wrong with the injector PW calculations in the ECM.

Although the injectors themselves won't open if the PW isn't large enough. And no, I don't know what this PW is for every injector, voltage range, and fuel pressure.

First get rid of the async injection mode. That will stop the surging. This is a known. Then go to closed loop and get the AFR oscillating, that too is required. Then get the gas analyzer results and look at all of the gas PPM's.

If the CO is high then the burn is incomplete. Reduce the timing and richen the mix a little (via the O2 window tables). Then check again.

RBob.

 

I didn't mean the calculations in the ECM were wrong, but the information they use to get the total sPW could be off from something I did. For instance, I don't use an IAT, so my IAT vs Coolant table is heavy on the coolant. I was just thinking that something like that could be my problem. You're saying the sPW is too low, so perhaps the way I have things set up, 1.25 is too low?

I'll have to post the gas readings when I give it another try because I'm not sure what they were. It could be a week or so since I have to work nights next week.

I'm going to disable async per your instructions, but with the tables the way they are set up, I still don't understand why it is going into async anyway. I mean with the high and low RPM set the same as well as the MAP, shouldn't that disable it right there? Does async kick in under any other circumstances?

Thanks for the help, as always.

 

Async mode can also kick in once the PW gets too small. That is what the transistion PW's are for/ By making them both 0 the ECM will remain in sync mode.

The async mode for short PW's does not provide the same exact volume of fuel and the fuel distribution leaves something to be desired. Which is why it surges. The math is correct to covert from a sync PW to an async PW, but comes up short when the compensations are factored in.

So once the injector flow rate is increased it is best to just disabe async mode.

RBob.

 

Rbob. quick EBL question, not sure if this is the best place but anyways... incase you haven't seem the northstar coil pack thread. me and a friend got his 93lt1 running on northstar coil packs and a repinned 727 ecm. since we wernt sure about it working, we just used my tuning stuff, prominator, adld cables and things. so I tossed out the idea of maybe going with EBL since the price is close to him buying all the cables, autoprom and stuff. I'm guessing with the port mob and you doing some timing code changes it would work? any thoughts on the idea? it is an under hood app and moving the ecm seems to be a lot of work. anyways to seal up the case or maybe stick the guts in a underhood case?

 

The EBL Flash ECM will run a DIS set up. Just need to change a few calibration parameters to suit. As you mention I wouldn't put this ECM underhood unless it was protected from the weather. Sealing the stock case could be done, but it isn't really practical. Just due to the case design and the connectors. If you have a '7730 around it is similar to it.

The PCB may fit inside of a '7727 case. Would then need to figure out the harness connectors.

If someone were doing a LT1 w/N* coils into another vehicle where the ECM was in the interior, I wouldn't hesitate to use an EBL Flash ECM to run it.

I'll post on the N* thread about the calibration parameters. The same changes will be required on $8D.

RBob.

 

Has anyone used an EBL for port fuel injection without using PortMod? I'm fuzzy on the benefits before I buy. It seems to me on a batch fire setup, the fuel injector fires at the ideal time only for one cylinder, it will be 90 or 180 degrees out of phase for the other three.

So without PortMod, you get half the fuel twice per revolution instead of all the fuel once per revolution. Wouldn't that even things out more and you'd me more likely to have fuel spraying when the injector is open?

If we were using a sequential fuel injection system, this would be more of a benefit, but I don't see how it's advantageous to a batch fire.

Please explain?

 

The f and y body TPI system are batch fire. They fire the injectors once per revolution. All at the same time.

Using the TBI firing scheme and firing the injectors at a rate of twice per revolution does work. However, a lot of time is spent waiting for the injectors to open. So the engine can easily become injector duty cycle limited.

This would also be a bank fire scheme where they alternate. But each bank will still be firing twice per revolution, offset from each other by 90* of crank rotation (8-cylinder).

A TBI injector opens as quicky as 0.6 milli-seconds. A port injector typically takes twice that at 1.2 millli-seconds. So a lot of duty cycle is lost using the TBI firing rate on a port injected engine.

If used on a low RPM truck engine, it will work. The Edelbrock MPFI conversion systems prove that. However, once the RPM range of the engine is increased you just can't get enough fuel in it. The injectors quickly become duty cycle limited.

This is where the Port Mod is used. It changes the rate to once per revolution and fires all injectors at the same time. A batch fire just like the stock TPI set ups use.

RBob.

 

Homer, I have a Ramjet 350 and I use the EBL with the port mod. It works very well. Runs very good and gets 22-23 MPG on the hiway, and I know my tune is not dead on yet, but still very good. Dean

 

That's impressive mileage. Do you lean it out for highway speed?

 

Does EBL work with the 7730 ECM?

I'm curious as it is not listed on their site.

 

Hi Homer, yes, EBL has lean cruise mode. Dean.

 

Ok so I'm new to this, I just puchased my Dynamic EFi computer the other day. How do I edit a BIN I cant seem to acsess the files.

 

Create a new folder on your laptop and copy all of the files from the CD into it (drag & drop). Although you can skip copying the self-install folder from the CD.

Download TunerPro from Mark's site: http://tunerpro.markmansur.com/

And install that.

Select a starter BIN from the EBL BINs folder. There is a text file that describes each BIN.

The XDF file is also supplied along with the calibration entries in a html file.

Head over to the Introduction to Tuning page: http://www.dynamicefi.com/Tune_Intro.php

And a lot more is discussed. You can follow it through on your laptop. Can also save the entire page to your laptop for use when at the car.

RBob.

 

Ok so I have looked a little at the thred but I cant find my question answered. Today I added 65Lb injectors and a 50MM/2" TBI and Intake to replace my 55Lb and stock TBI/intake. Now my car idles at 1300 RPMs. It used to idle at a nice sedate 600 RPMs. I changed the BPC tables but nothing seemed to happen.
How do I get my Idle back to normal?

-Rob

 

You may need to close the throttle blades with the idle stop screw. It may also be a vacuum leak causing the high idle. First check the IAC steps at a warm idle and no load. If it is at zero the ECM can't close it any further to bring the idle down.

Then turn the idle stop screw out to close the blades. As you do this the idle should lower. As it approaches the desired idle speed watch the IAC steps on the WUD. Adjust the screw to get between 5 & 10 IAC steps at idle (no loads such as A/C, fan and so on).

If you can't bring the idle down then I'd start looking for a vacuum leak.

RBob.

 

Especially since it sounds like you've installed larger throttle bodies. More air coming in even at same throttle setting.

 

So funny story. Turns out my high idle was all mechanical. My air intake sits very low on the throttle body because it barely clears the hood otherwise. It sits so low as to touch the cruse control throttle cable actually. Apparently it was actually pulling the cruse control throttle cable and thus giving me what seemed to be a high idle. Go figure.

 

Hi All,
I am starting to setup up knock sensing and computer controlled distributor. I got the knock sensor wired up and working so I took it for a run. I found that the knock counts on the WUD went to 1024 then stopped. I expected it to reset and start counting again but it does not. The counts did reset and start counting again when I did not have the knock sensor module connected. At that time the counts would have been just noise I'm guessing.

I have the malfunction bits turned off, but I dont think that is the problem as it used to reset when there was no input.

Any ideas?

thanks

 

What vehicle? What engine? Stock or modified? Regular timing chain? Roller rockers?
What RPM/MAP do you see KC? What is you SA table at that area?
When KC occurs are you into pedal somewhat heavy or just regular driving?

Make sure your initial timing in .bin matches your physical at distributor with the ESC connector disconnected. That removes ECU control of timing.

 

I have not hooked the computer controlled distributor up yet, I was just making sure the knock sensor and module worked as I picked up the module at the men's mall.

The EBL is in a 76 GMC motorhome with an old's 455 engine, pretty much stock except for the EBL controlling a holley TBI.

I am still using the HEI Dist on it. I just advanced the timing to get some knock to be sure that was all working before I wire up the CCD.

 

Given enough time the KNK gauge would roll over to 0 again. The difference is that when no ESC module is connected it takes about a second to count up and go back to zero. So it is happening quickly.

Since it should also quickly roll back to zero with forcing some knock I took a look at the WUD code. I found that the code is not correct, it was changed from when it was correct.

What is done for the KNK gauge is that the actual ECM reported knock counts are divided by 63 and displayed. This was changed to a divide by 5.6689 (or some such odd ball value) and then displayed.

This means that the gauge quickly hits 1024 and peaks. The counter keeps counting up with no change in the gauge value. Until the actual counter rolls overs back to 0 and the gauge resets.

Having the KNK gauge match the knock counts on the Spark Retard display was done way back in version 1.5 of the WUD. Having it not match with the odd divide value I'll find out when that was done. Note that this has been corrected for the next release.

The next release will also have far more COM ports available (COM1 through COM25) to support USB to serial adapters.

RBob.

 

RBob,
Good to hear it is simply a bug, I was ready to get out the O'scope and check to see if my module or sensor had gone faulty. Now I can go ahead with my distributor install this weekend.

I'm an electronics tech...I'm into gadgets... so I've been looking for a small touch screen that I could make permanent to run the WUD etc. Also Ontario has just passed the handsfree law that covers any type of electronic device not attached to and part of the vehicle, so PC's are a no-no now.

Any suggestions?

thanks

 

In TunerPro, when I view a 3D table graph, the surface appears sideways.

I think I just need the kPa numbers to go in the opposite direction, does anyone know how to get the axis to do this?

Is there a different version of TunerPro I should be using? I'm on Windows 98 using TunerPro version 4.14


One other thing - if you feel like suggesting a couple angles I should consider in smoothing these VE tables out, feel free to chime in.

 

I lately used .90 for TP. .80 will smooth to greater degree.

I find the .90 or .80 does not make much of a change in surrounding cells which may ge a good thing.

 

You can rotate the graph by holding the Ctrl key down, then left clicking and dragging.

As for additional smoothing. Use the WUD and start a VE learn. Set the smoothing factor as required. Then just stop the learn. Basically, start a learn then just stop it. The smoothing will be applied to the current VE tables.

Note that in the Low Speed VE table the triangular area of low MAP and low RPM can be flattened by hand. No learning takes place there so it is best to reduce that area until even with the surrounding areas that did learn in.

RBob.

 

Much appreciated. I've now found the graph rotate directions in the help file as well. The shift and zoom functions are working, but the graph rotation is not. I tried by clicking with the left mouse button while holding ctrl, and I tried using control and the arrow buttons. Same thing - worked for shift and zoom, not rotate. Anyone else have this problem?
I tried using an older version, was able to find TunerPro 4.12, still can't rotate. Anyone have version 4.0 or something similar?

 

Whats a good wide band O2 to get?

 

http://www.dynamicefi.com/EBL_TT-1.php

 

Tuning with EBL

After a bit of hiatus I got back to tuning my first conversion project – aka Beast (1975 C20). Carburetor to TBI conversion was completed in the summer of 07 and EBL conversion was installed in Oct of 07. After a quick tune (about 8 drive tests) I was able to get truck to running very well. Due to other projects I was never able to finish dialing in the last ounce of performance to where it should be. Recently, have re-visited the old truck to find that it was plagued by false knock.
In my conversion I used GM 10456288 Knock Sensor which I found to be very sensitive. The exhaust system proved to be too loud for this sensor – header 5/8” to 3” collector, No cats, H cross over to dual Delta 40’s were causing exhaust system resonances that KS was picking up. At first I tried to retard SA tables with no measurable success. It got so bad at times that engine would lose power when trying to climb a small hill! Yaks! With EBL I was able to temporarily disable KS retard and verify by ear that I did not have engine pinging under load. Engine was not pinging until pushed very hard!
I went through several recommended steps trying to solve KS sensitivity (false knock). Based on information from another TGO thread I sourced ESC module from earlier CCC equipped car – these modules suppose to have better selectivity 4-pole filters vs. 3-pole used in TBI. Reduction in false knock was noticeable, but not substantial. Final solution to false knock was a combination of CCC ESC and 90 degree elbow – see photo below.



After that I have reviewed my SA and VE tables – these where determined to be too far out. In view of this I have restarted with EBL_F_TB by changing it from 305 to match my 350 engine, disabling EGR, disabling Highway mode and configuring for 64lb injectors. Interestingly my 350 likes 6 degree of initial SA. The 305 calibration proved to be a bit rich at first, but later after about 5 test drives (VE learns) an interesting VE pattern has developed. Unfortunately, my WBO went to the WBO heaven (needs new sensor) and at this time I am not to able to verify commanded vs. actual AFR.

Low Speed VE


High speed VE


Main SA Tables


Today's drive testing VE learn




By searching posts I have not see anything like this. Please see plots above. My idle fuel pressure is right about 14 PSI on a dedicated (un-calibrated) gauge, but I have a bad feeling that fuel pressure drops when I drive. To get to the bottom of this I’ve ordered Autometer 2239 0-30 PSI FUEL pressure sensor which will be installed near TB inlet port.

Question regarding this sensor (2239) and EBL. Is 2239 a 5 volt device and has 0 to 5 volt output? Can task ECM + 5 volt reference rail (ECM C14) be tapped to provide power to this sensor? Is it accurate enough? I have not seen data sheets for this sensor it would lead to believe that this device does not draw no more than 10-20 mAmp from 5 volt supply. Any further suggestions are welcome…

Specs
1975 C20, 6500lb (3/4) 4.10 rear 33” tires,
Engine 350 with mild RV cam, smog heads.
Trany – 700R4
Intake – Holley 300-49
TB – stock SBC TB with 64lb injectors, adjustable FPR
Dynomax headers 5/8-3”, 2-1/2 inch dual into delta 40’s

//RF

 

Today's Datalog (csv)

General observation - knock counts appear when BLM are >132 counts (lean)

//RF

 

I would say it is false knock. As far as timing it is close to mine . I run 92 octane. I see you are at 36d max SA from 20-50 kpa. then it trails off to 22d SA at 100 kpa at 4800 rpms. I cruise at 1900 rpms and around 28 d SA (close to you) and will pick up KC on a cold engine every time. Then it lessens considerably as engine develops heat. If I start datalog on a warmed engine no KC or very little. All my KC is lower RPMs and when I acceeerate to xway speed. Seldom on max accelleration. I agree it may be exhaust related. I also have no cats and real duals with crossover to hooker aerochambers that are very very loud.

I dont believe 132 is lean, just adding fuel to run at stoich. These cold morn here in WI I see 132 as the norm. I could not open your last log,

 

That is a +5V sensor. You can use the +5 V reference signal to the TPS/MAP sensors. Then wire the output to the EBL Flash board and select the AutoMeter 0-30 psi sensor in the preferences dialog.

RBob.

 

Thanks Ronny for taking a look. Did you use Firefox ( I was able to download it with Firefox)??? Yes, it was a cold Sunday morning in So-Cal (if you can call 48F cold! I run stinky 88 So-Cal gas in my 350 as it is not performance engine by any means (about 8.9:1 flat tops).

The data log captures a cold start and drive. Today, I went through the data log looking for area of knock. From a cursory look KS appears randomly along 1800-2000 RPM cruise conditions. This leads me to believe that I have an exhaust system resonance due to a back wave (reflection) building up and causing resonance vibrations which are picked up by KS. My exhaust system is a straight 2-1/2 pipes (with H crossover just aft transmission) from headers dumping into Flowmasters.

Rbob
Thanks for confirming sensor info. I'll try to post updated log next weekend.

//RF

 

Update

Well, I really would like to get to the bottom of this false knock and corresponding stumble (post acceleration event).
To get there I brought my ZT-2 from the dead - new WBO sensor and installed Autometer 2239 fuel pressure sensor. Got everything squared away Saturday afternoon, but could not get a test drive in.

First observations - ZT-2 display and EBL display do not match for approximately first 7-10 minutes - display about 1/2 AFR point lower (e.g. 13.5 on display and about 14.0 on WUD). There after ZT-2 and EBL WUD match. My guess is that there is a temp comp in the ZT-2 linear output. Did anyone observe the same behavior

Fuel pressure Min 13.1 (at start) max 15.2

Datalog
check AE event at 0:06:22 initial AE was ok, but post AE engine goes lean


//RF