Knock-Knock, Diacom!
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,629
Likes: 9
From: Drag racing junkie Va.
Knock-Knock, Diacom!
Phase 2 of my knock problem, checked everything from the previous "Diacom users" post, thanks for the hints guys. Went thru the service manual checks today, thats ok, found a loose shield, tightened it, made 2 short blasts, still seeing 8 degrees of retard at 5400! I saw the same thing at the track this weekend before the laptop battery died. :( Does anyone have files on their runs they could send me for a stare & compare? I would love files for a 92-93, but could use any LT1, Thanks Dave :confused:
Instructor
Joined: May 2000
Posts: 104
Likes: 0
From: Portage Indiana
Re: Knock-Knock, Diacom! (new92racer)
Send me your e-mail address and tell me how to copy them from the "stored" data I have on the 3.5 Diacom disk and I'll send them. They're from a 93 auto with 3:73
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,629
Likes: 9
From: Drag racing junkie Va.
Re: Knock-Knock, Diacom! (Vince Ivanc)
Steve, I set you email.
Vince, thats not what I wanted to hear, but thanks for the info.
I ran my first 12s yesterday, but the Diacom still shows knock & 8 degrees retard!
Vince, thats not what I wanted to hear, but thanks for the info.
I ran my first 12s yesterday, but the Diacom still shows knock & 8 degrees retard!
Burning Brakes
Joined: Aug 2000
Posts: 984
Likes: 1
From: Cincinnati OH
Re: Knock-Knock, Diacom! (new92racer)
Dave,
If you know for sure that it's a false knock (obviously if it's real knock, then the ESC is doing it's job saving your motor's butt
), you can still desensitize the knock sensors, but it requires some electrical work. Check out this link http://www.charm.net/~mchaney/f-tech.htm , there's info on how to do it. Haven't done it myself, but ran across this page a while ago. I don't seem to have a knock retard problem on mine with roller rockers etc. so I never bothered, but it was interesting nonetheless.
Vince
If you know for sure that it's a false knock (obviously if it's real knock, then the ESC is doing it's job saving your motor's butt
), you can still desensitize the knock sensors, but it requires some electrical work. Check out this link http://www.charm.net/~mchaney/f-tech.htm , there's info on how to do it. Haven't done it myself, but ran across this page a while ago. I don't seem to have a knock retard problem on mine with roller rockers etc. so I never bothered, but it was interesting nonetheless.Vince
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,629
Likes: 9
From: Drag racing junkie Va.
Re: Knock-Knock, Diacom! (Vince Ivanc)
Steve,
I just got back in town last night from a trip, opened the files fine. They showed that you also had a 5-8 degree retard
"at times"! Even on the runs that didn't have a retard event, the timing backed up, maybe its normal?
Vince,
Thanks for the site, I think tonite I'll try it!
I'd still be interested in seeing more Diacom files from strip passes if anyone can send them,
hope to see everyone at Cecil County this weekend, thanks Dave :yesnod:
I just got back in town last night from a trip, opened the files fine. They showed that you also had a 5-8 degree retard
"at times"! Even on the runs that didn't have a retard event, the timing backed up, maybe its normal?
Vince,
Thanks for the site, I think tonite I'll try it!
I'd still be interested in seeing more Diacom files from strip passes if anyone can send them,
hope to see everyone at Cecil County this weekend, thanks Dave :yesnod:
Intermediate
Joined: Apr 2001
Posts: 42
Likes: 0
From: Ft. Wayne, IN, USA
Re: Knock-Knock, Diacom! (new92racer)
I just spoke with ed wright at Fastchip...I am having same trouble with false knock on 383 L98 based engine. I get 9 degrees retard under full throttle, and allready tried to install a new knock sensor very loose with lots of teflon tape. Ed said he can desensitize the knock sensor with the chip (re-burn it). I am sending it off this week to get done. Also, what is you Block Learn Multiplier numbers under full throttle? if they are more than 128-130, you could have the same problem I had, which is running to lean (then the computer adds fuel via BLM numbers increasing to 140-150-160, and this could be connected to ignition retard). Also, Ed said to clean all electrical connections with specific cleaner (sometimes if dirty, they can have more resistance).
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,629
Likes: 9
From: Drag racing junkie Va.
Re: Knock-Knock, Diacom! (SDBOJRAB)
SDBOJRAB,
I went back and checked my files, my L&R BLM were consistantly right at 128.
I pulled up the above desensitizing website, and tried this as a test. After measuring the knock sensors 3900 ohm resistance, I pulled the wire off the sensor, installed a 3900 ohm resistor to ground and connected it to the lead back to the ECM. I then made a 1&2 blast with the DIACOM hooked up, EUREKA! No Knock event & no codes! :cool: I know this isn't the real fix, I'll rewire with the whole network soon. But the engine feels great, improved response, timing still moves around a little under control of the ECM, but the advance is higher. This test only fooled the ECM into thinking everything is normal and I won't drive it this way on the street. I have heard rumors that some of the chip burners do turn off the knock sensors all together in their chips for more performance. It would be interesting to hear what Ed thinks of this practice since I have one of his Phase II chips and lean towards a custom chip in the future. If anyone has used this desensitizing proceedure I'd like to hear about your results. Thanks Dave :chevy
I went back and checked my files, my L&R BLM were consistantly right at 128.
I pulled up the above desensitizing website, and tried this as a test. After measuring the knock sensors 3900 ohm resistance, I pulled the wire off the sensor, installed a 3900 ohm resistor to ground and connected it to the lead back to the ECM. I then made a 1&2 blast with the DIACOM hooked up, EUREKA! No Knock event & no codes! :cool: I know this isn't the real fix, I'll rewire with the whole network soon. But the engine feels great, improved response, timing still moves around a little under control of the ECM, but the advance is higher. This test only fooled the ECM into thinking everything is normal and I won't drive it this way on the street. I have heard rumors that some of the chip burners do turn off the knock sensors all together in their chips for more performance. It would be interesting to hear what Ed thinks of this practice since I have one of his Phase II chips and lean towards a custom chip in the future. If anyone has used this desensitizing proceedure I'd like to hear about your results. Thanks Dave :chevy
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,629
Likes: 9
From: Drag racing junkie Va.
Re: Knock-Knock, Diacom! (new92racer)
I pulled up the Zip file and calculated for a 50% knock reduction the R1=1948 ohms, R2=11683 ohms.
Once I find these4 resistors I'll wire it up and give you guys feedback.
dave :cool:
Once I find these4 resistors I'll wire it up and give you guys feedback.
dave :cool:
Melting Slicks
Joined: Apr 2001
Posts: 2,117
Likes: 222
From: Ca.
Re: Knock-Knock, Diacom! (SDBOJRAB)
I just spoke with ed wright at Fastchip...I am having same trouble with false knock on 383 L98 based engine. I get 9 degrees retard under full throttle, and allready tried to install a new knock sensor very loose with lots of teflon tape. Ed said he can desensitize the knock sensor with the chip (re-burn it). I am sending it off this week to get done. Also, what is you Block Learn Multiplier numbers under full throttle? if they are more than 128-130, you could have the same problem I had, which is running to lean (then the computer adds fuel via BLM numbers increasing to 140-150-160, and this could be connected to ignition retard). Also, Ed said to clean all electrical connections with specific cleaner (sometimes if dirty, they can have more resistance).
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,629
Likes: 9
From: Drag racing junkie Va.
Re: Knock-Knock, Diacom! (drive it)
drive it,
Thanks for the insight!
Like I said, I want to desensitize the false knock but keep the protection of the retard,
just need some guide line help on how far to go down (what % reduction). I've also been thinking about the wideband O2 and/or
an EGT sensor for this problem and for tuning the A/F ratio.
Has anyone else been looking into where to get them and how much these units cost?
Are the wide bands compatable with a Diacom? I think the factory unheated O2s are a little slow to use as a tuning tool,
correct me if I'm wrong please.
Thanks Dave :seeya
Thanks for the insight!
Like I said, I want to desensitize the false knock but keep the protection of the retard,
just need some guide line help on how far to go down (what % reduction). I've also been thinking about the wideband O2 and/or
an EGT sensor for this problem and for tuning the A/F ratio.
Has anyone else been looking into where to get them and how much these units cost?
Are the wide bands compatable with a Diacom? I think the factory unheated O2s are a little slow to use as a tuning tool,
correct me if I'm wrong please.
Thanks Dave :seeya
Drifting
Joined: Mar 1999
Posts: 1,931
Likes: 1
From: Norcross GA
Re: Knock-Knock, Diacom! (new92racer)
You did notice that a desense of mor thatn 35% is not recommended,.... right?
Tuning w/ a factory O2 is not hte best approach. A "real" WB unit cost about $3K. Those rinky-dink rich/lean meters,.... save your $ and use the factory unit. It is basically the same narrow band (NB) unit w/ a display. A WB sensor cost $200 min. Then there is the circuit to run it and interpret it. You can't just drop in a WB in place of the NB factory unit.
There are other solutions, but I'd suggest you stick w/ what you've got. Most LT1 tuners shoot for O2=900mV (ballpark) @ WOT
Recheck your data. @ WOT you should not be @ 128. You are probably looking at the cell B/4 it goes to WOT. Closed Loop you want 128. WOT is Open Loop operation.
Tuning w/ a factory O2 is not hte best approach. A "real" WB unit cost about $3K. Those rinky-dink rich/lean meters,.... save your $ and use the factory unit. It is basically the same narrow band (NB) unit w/ a display. A WB sensor cost $200 min. Then there is the circuit to run it and interpret it. You can't just drop in a WB in place of the NB factory unit.
There are other solutions, but I'd suggest you stick w/ what you've got. Most LT1 tuners shoot for O2=900mV (ballpark) @ WOT
Recheck your data. @ WOT you should not be @ 128. You are probably looking at the cell B/4 it goes to WOT. Closed Loop you want 128. WOT is Open Loop operation.
Burning Brakes
Joined: Aug 2000
Posts: 984
Likes: 1
From: Cincinnati OH
Re: Knock-Knock, Diacom! (ZylaRace)
Recheck your data. @ WOT you should not be @ 128. You are probably looking at the cell B/4 it goes to WOT. Closed Loop you want 128. WOT is Open Loop operation.
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,629
Likes: 9
From: Drag racing junkie Va.
Re: Knock-Knock, Diacom! (Vince Ivanc)
ZylaRace,
Thanks for the info on the WB O2 :eek: I may have a friend that has that setup, but I don't know for sure. You mentioned an O2 reading of 900 mv. do you run this or a lower reading? I've heard to tune for numbers from 850-950 mv. from other forum members. Right now my O2 readings are in the 920-940 range @ WOT, which I think are rich. This was due to a dyno session where they convinced me that other LT1s had picked up from HP from increasing FP(we still don't race dynos tho!). From what I understand, 850 is leaner, which I'm trying to get at. Back in the carb days, I'd lean it out until it shot ducks in the traps, then richen it up a step for the night air. I figure this fancy-smancy ECM will do that for me once I get the FP adjusted in the ball park, correct me if I'm wrong. Thanks for the help, I'm going to back off the fuel pres. this weekend at the Cecil County meet and see if I pick-up MPH. Any other suggestions are welome, hope to see lots of you there, Dave :seeya
Thanks for the info on the WB O2 :eek: I may have a friend that has that setup, but I don't know for sure. You mentioned an O2 reading of 900 mv. do you run this or a lower reading? I've heard to tune for numbers from 850-950 mv. from other forum members. Right now my O2 readings are in the 920-940 range @ WOT, which I think are rich. This was due to a dyno session where they convinced me that other LT1s had picked up from HP from increasing FP(we still don't race dynos tho!). From what I understand, 850 is leaner, which I'm trying to get at. Back in the carb days, I'd lean it out until it shot ducks in the traps, then richen it up a step for the night air. I figure this fancy-smancy ECM will do that for me once I get the FP adjusted in the ball park, correct me if I'm wrong. Thanks for the help, I'm going to back off the fuel pres. this weekend at the Cecil County meet and see if I pick-up MPH. Any other suggestions are welome, hope to see lots of you there, Dave :seeya
