Which Knock Sensor & Memcal??

[IsaacHayes]

Ok, running a 3400 on (tuned) $DF DOHC 3.4L code.

I understand you must match the knock sensor with the same MEMCAL so it has the knock filter for that sensor. I also heard the knock sensors are different for different displacements. So........

Which would be best setup to run on the above combo?

1) 3.1 MPFI KS and MEMCAL
2) 3.4 DOHC KS and MEMCAL


I have a 3.4DOHC MEMCAL and a 3.1mpfi KS currently. I also have a 3100 KS... Trying to decide what parts to buy to match up........

[bszopi]

I would go with the DOHC KS.

[robertisaar]

I would go with the DOHC KS.

i'm finding my 3100 KS and 3.4 KF to be working fine....

it picks up knock where it should(intentionally high spark advance to test a knock sensor probably isn't the best way to do it, but it will work)

[IsaacHayes]

Brad, I'm leaning with you. I looked up on a parts site and a 3.4L RWD has the same KS as the DOHC. 3100 and 3.1mpfi have same part number.

Then I looked up a 91 DOHC and it listed both ones?!?! LOL

Robert, It might pick excessive up, but I want something that won't miss ping either.. Loud exhaust makes it hard to hear.

[robertisaar]

Robert, It might pick excessive up, but I want something that won't miss ping either.. Loud exhaust makes it hard to hear.

mine isn't exactly quiet either...

but its working so far as i am concerned...

[Superdave]

i'm using a OBD1 3100 memcal with a 91 3.1 KS.. no problems.


i have a 91 memcal and a OBD2 3400 KS on my test bench, the counts go up with i smack it with a screwdriver. haha

[robertisaar]

i have a 91 memcal and a OBD2 3400 KS on my test bench, the counts go up with i smack it with a screwdriver. haha

awesome stuff right there...

i would pull an A-body 3100 memcal, but they aren't that common around here, let alone being in the yards...

[IsaacHayes]

From what I've seen the KS and knock filter are more or less the same between the same size engines.

AC delco P/N for 91-95 DOHC 3.4 is same as 93-95 ironhead RWD f-body motor.

OBD2 knock sensor for 3400 though even crosses over to 3100 stuff....

I've heard some guys with 305's swapping to 350's and not matching up the KS and filter and having mad KR counts....

but looks like the V6's are more forgiving. Matching up the filter and sensor at least should be the best...

But then also you have to wonder what would be the best memcal for limp home mode.... With a highly modified engine it may not matter as it might not run at all either...


What kind of timing does LHM use?

[Superdave]

six shooter was looking into a way to tune limp home mode a while back IIRC..


probably 0 advance, i'd guess the ICM would just control that side of things.

I haven't tried to run mine in limp home mode, but i doubt it would even stay running.

[IsaacHayes]

Yeah that's the thing with an engine swap and/or larger injectors it even running would be an issue. But if it goes to 0 advance at least you don't have to worry about it going back to stock timing tables and knocking like crazy if the tables were higher than what the motor can safely run on.

[robertisaar]

i pulled the EEPROM from the GP once while it was running, wow.

goes rich as hell and has some serious timing pulled...

so its entirely safe, just a LOT less power...

[robertisaar]

thought:

it seems like the knock sensor is chosen to listen to a specific noise that is dependant on bore size and that the filter is used to remove the unique noises from the different valvetrain arrangements....

assuming that, i'd say its necessary/adviseable to use the knock sensor intended for your engine size and somewhat less important that you use the correct filter...

correct me if i'm wrong in this thought process...

[IsaacHayes]

If that is the case, a 3.4 DOHC/3.4iron head KS is needed, and then a 3.1mfpi memcal.... Opposite of what we have... LOL.

Are the knock filters different between a 3.1 iron head and 3.1 alum? etc? If so then your idea might be right... I'll have to refer to your chart you measured out.

[ForcedFirebird]

The memcal/ks issue has been discussed a lot of times at TGO. You want the KS that matches your cylinder bore (or as close as possible).

[IsaacHayes]

And what about the filter?