bad knock sensors on dyno? (pics/vids)

[survyor2]

Did bad knock sensors/wiring do this to my dyno reading? I street tuned the car, 17psi, 93oct, 11.7afr. It pulled very hard and very fast. The day before I went to the dyno I could feel the power drop. I didn't know what it was on the dyno. No codes on dyno. AFR fell to 10.6 during the power drop. On the way home it threw codes 34, 51, 52. I seem to always have 51 from the a/c.

I definetly can't complain about 295ft-lb at only 3700rpm. Any ideas? Time for new knock sensors and wiring.

Dennis

 

[quake]

start with rewiring first, also i hope you have a big turbo using 17psi on 93 oct pump gas.

 

[dbsupra90]

wow ive never seen a 7m dyno graph that looked like a hammock.

51 means either you touched the gas pedal while in diag mode or your tps is off adjustment. 52 is knock sensor of course. that would explain the huge dip in power. it pulls the crap out of timing and power will fall way off. get that fixed and im pretty confident that will take care of your issues.

note: presence of knock will NOT set a code. only a bad knock sensor or wiring will. it has nothing to do with knock itself.

 

[jetjock]

Nice looking car. As db pointed out your code 51 has to do with the TPS. Either that or you're driving the car in diagnostic mode with the engine off and AC on. If that's the case let us in on the trick because it'd save a shitload of fuel

 

[IJ.]

LOL @ "Hammock"

 

[BoostedToys]

A little off topic but...Wow...thats a nice Supra! Love the lights!:thumbup:

 

[survyor2]

Thanks guys! Sounds like you guys agree on the knock sensors could be the cause of this. Thanks for the info on code 51 (tps). I'll fix that too.

P.S. yes, big turbo, fully built

Dennis

 

[vas85]

A little off topic but...Wow...thats a nice Supra! Love the lights!:thumbup:

I was thinking the same thing! It's nice to see another beautiful black Supra

Also if that turbo acts anything like mine judging by the graph you should be hitting 400-450hp after everythings in check. My car makes peak power @ 6300rpm.

 

[quake]

Thanks guys! Sounds like you guys agree on the knock sensors could be the cause of this. Thanks for the info on code 51 (tps). I'll fix that too.

P.S. yes, big turbo, fully built

Dennis

lol good the more of us on the road the better.

 

[survyor2]

Fixed! Damn knock sensors messing up my dyno graph.

412hp/402tq

 

[Rennat]

Thats beautiful right there.... what kind of turbo do you have?

 

[tekdeus]

So when the knock sensors are triggered, the ECU drops timing for how long? several seconds? or is it a real-time adjustment? Just wondering because my car is having slight surges and dips in power at 15-17psi.

 

[Supra_Villan]

not to be a thread jacker guys...but i am running an n'a block, which has only one spot for a knock sensor, and i'm only running an afc/afm for management, i guessing i'm gonna throw a 52 and suffer from it? or could i tap into the signal from the one i'll actually be using and run both wires off of that one sensor? i'm not apt to drilling my fully assembled block...:3d_frown:

 

[shaeff]

not to be a thread jacker guys...but i am running an n'a block, which has only one spot for a knock sensor, and i'm only running an afc/afm for management, i guessing i'm gonna throw a 52 and suffer from it? or could i tap into the signal from the one i'll actually be using and run both wires off of that one sensor? i'm not apt to drilling my fully assembled block...:3d_frown:

Pigtail the signal wire at the ECU end, basically jumping the input from one sensor to both inputs.

 

[jdub]

So when the knock sensors are triggered, the ECU drops timing for how long? several seconds? or is it a real-time adjustment? Just wondering because my car is having slight surges and dips in power at 15-17psi.

The info on this is a bit vague, but the amount of retard angle depends on if the sensors detect a weak, medium, or strong knock....the amount of retard increases from weak to strong. When knock stops, retard is stopped and timing is advanced by fixed angles a little at a time. Advance continues until knock occurs again and the cycle repeats. So in this sense, yes it is a real time adjustment.

 

[tekdeus]

The info on this is a bit vague, but the amount of retard angle depends on if the sensors detect a weak, medium, or strong knock....the amount of retard increases from weak to strong. When knock stops, retard is stopped and timing is advanced by fixed angles a little at a time. Advance continues until knock occurs again and the cycle repeats. So in this sense, yes it is a real time adjustment.

Is there a way to wire in something that would show whether or not knock is being detected?

 

[IJ.]

Buy a "knock link"

It has a series of LED's that light up to indicate the level of knock.

 

[tekdeus]

Buy a "knock link"

It has a series of LED's that light up to indicate the level of knock.

Cool unit, IJ. Is there a way to know if the ECU is pulling timing because of knock? Or is it obvious? i.e. huge drop in power, or check engine light? I'm unsure of why my car is having slight surges and dips in power at full boost.

 

[jdub]

When the ECU pulls timing due to knock, there is no CEL. You will see a loss of power...the curve will flatten or dip on the dyno graph, but not like the "hammock" in post #1 (unless you go straight to "strong"). A surge? I don't think that would be due to pulling advance from the knock sensors...the ECU doesn't add back advance enough to cause that.

 

[dumbo]

I've heard it also adds fuel when it senses knock, along with pulling time, so i'm assuming you would see a very rich condition?