detonation spikes

[echostatic]

ive noticed that my boost knock gauge will spike occasionally if i go full throttle. when this happens, i will let off the gas real quick, then if i punch it again i wont see any knock. has anyone else experienced something similar?

 

[WS6]

I assume you mean just "knock gauge" as in a casper's unit. So, could be a few things; 1, plain old (and bad!) detonation.2, Burst knock, or that fractional second when fuel pressure lags and the engine goes lean momentarily under sudden acceleration.3,Transitional knock on the 1-2 or 2-3 upshift.4, False knock when the engine or accesories are physically banging on the chassis somewhere and setting off the knock sensor on the block.

I guess we need more specific symptoms as to when and where this happens and under what conditions it happens.

...

 

[echostatic]

hmm, yes i accidentally wrote boost gauge, then corrected myself and seemed to have forgotten about removing the first word. sorry, i was really distracted writing that. yes i mean caspers knock gauge. let me be a little more specific.

it happens sometimes when suddenly going WOT at low speeds (~20mph) when i go WOT and see the knock gauge suddenly jump to red, i instincively let off the gas. after i do that, i can immediately jump right back on it and not see any more knock. how can you tell if its regular knock or burst knock, because that casper gauge stays illuminated at the highest level the knock hits for a few seconds before showing the current amount of knock.

ive kind of simply shrugged it off until i obliterated that head gasket last week. the night i did that though i could hear it knocking under the hood just before it blew. i havent heard any knock in this situation in the past, though. how can you determine what kind of knock you are getting?

 

[WS6]

I'm not sure what you have to monitor knock outside your knock gauge, but If you have a scanmaster installed I'd be looking at what the KR (knock retard) the ECM is showing. Let's say you do and when the knock gauge goes full red and the scanmaster shows an instant 17 KR number then I'd say it was transitional knock from the tranny shifting down. Now if the scanmaster shows a 5.6 then 8.0 then 14 I'd say you have true detonation. See? Real knock is generally an escalating event. Whereas false knock is usually an instant high number that goes away when the tranny shift, fuel pressure or external rattling is no longer present.

Burst knock is something I read about from one of John Spina's posts, and I'm paraphrasing his post, but when the peddle is mashed the fuel pressure lags momentarilly and causes the A/F ratio to go lean till pressure catches up. Yes, lean is mean, but lean is also where detonation lives.

Myself, I ignore knock under dead stop launch and even under the condition you describe. But when I look for it is when I'm rolling in 3rd gear at 45 MPH and I mash it. If I see ascending KR numbers then I lift and go back to tuning the fuel and or timing.

But I must add, every engine/car is different, some tolerate burst knock and some don't experience shift point knock. Bottom line is, you need to have all the tools to combat knock( in all forms) that you can afford. Like a scanmaster, methanol injection, a means to control boost and a chip that you can tune. You also have to spend time going over the sources of false knock like banging downpipes, sacked out motor mounts,tranny mounts. Whatever can bang around to trigger the knock sensor.

TB has hours and hours of reading about false knock and there are some smart minds that post about it. Read the threads and grasp the concepts. Razor has some fascinating insight on false knock and tuning for it. But in the end you'll need to address it. Even if your confident it's a false knock issue, the ECM does not know that and it is pulling tons of timing to address it, and that means power being left on the table.

 

[roadkill73]

I'm not sure what you have to monitor knock outside your knock gauge, but If you have a scanmaster installed I'd be looking at what the KR (knock retard) the ECM is showing. Let's say you do and when the knock gauge goes full red and the scanmaster shows an instant 17 KR number then I'd say it was transitional knock from the tranny shifting down. Now if the scanmaster shows a 5.6 then 8.0 then 14 I'd say you have true detonation. See? Real knock is generally an escalating event. Whereas false knock is usually an instant high number that goes away when the tranny shift, fuel pressure or external rattling is no longer present.

Burst knock is something I read about from one of John Spina's posts, and I'm paraphrasing his post, but when the peddle is mashed the fuel pressure lags momentarilly and causes the A/F ratio to go lean till pressure catches up. Yes, lean is mean, but lean is also where detonation lives.

Myself, I ignore knock under dead stop launch and even under the condition you describe. But when I look for it is when I'm rolling in 3rd gear at 45 MPH and I mash it. If I see ascending KR numbers then I lift and go back to tuning the fuel and or timing.

But I must add, every engine/car is different, some tolerate burst knock and some don't experience shift point knock. Bottom line is, you need to have all the tools to combat knock( in all forms) that you can afford. Like a scanmaster, methanol injection, a means to control boost and a chip that you can tune. You also have to spend time going over the sources of false knock like banging downpipes, sacked out motor mounts,tranny mounts. Whatever can bang around to trigger the knock sensor.

TB has hours and hours of reading about false knock and there are some smart minds that post about it. Read the threads and grasp the concepts. Razor has some fascinating insight on false knock and tuning for it. But in the end you'll need to address it. Even if your confident it's a false knock issue, the ECM does not know that and it is pulling tons of timing to address it, and that means power being left on the table.

I too would sometimes get a reading when I go WOT. The scanmaster would go from nothing to 4.2. No escalating numbers, just jumps from nothing to a number like 4.2 or sometimes 5.0
My thought was knock on the shift. I spoke to Razor since I am running one of his kits.
He said it may be knock from shift, but to rule it out he suggested put the car in D3, rolling at around 50mph which would put me in third gear and it wont shift, go WOT and if no knock then it is false.
I did that and everytime I got 0 knock. I tried from a rolling 10mph and let it shift and I would get readings on the scanmaster.

 

[echostatic]

if i can find the cable i can hook up turbolink and watch the knock #s there. i know its around here somewhere...

roadkill73, i tried your highway test today. i wouldnt see knock putting it in d3 and keeping it from shifting, but the knock gauge would light up like a christmas tree if it did downshift.

maybe i should look into getting a scanmaster so i dont have to worry about keeping a laptop hooked up.