Slight Knock

Ttype6

Well-Known Member
Is it normal for the o2 mvs to bounce around a lot under normal driving?
Yes,this is closed loop operation. The oxygen sensor is sending information to the computer and the computer is constantly adjusting the air fuel ratio based on the information it receives. If you have a chip programmed for closed loop idle,you will see the same fluctuation at idle. When you have open loop idle there is no correction so you will see a constant high O2 number at idle. You will also see a constant higher number at WOT because that is open loop operation as well, no correction.
 

SteveZ82

Active Member
Yes,this is closed loop operation. The oxygen sensor is sending information to the computer and the computer is constantly adjusting the air fuel ratio based on the information it receives. If you have a chip programmed for closed loop idle,you will see the same fluctuation at idle. When you have open loop idle there is no correction so you will see a constant high O2 number at idle. You will also see a constant higher number at WOT because that is open loop operation as well, no correction.

Thanks. I’m new to the SM and TRs in general so I’m learning. These cars are different than ones I’m used to working on. Which were carbureted motors.


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Ttype6

Well-Known Member
Thanks. I’m new to the SM and TRs in general so I’m learning. These cars are different than ones I’m used to working on. Which were carbureted motors.


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Did you get a Power Plate? I recommend that you turn the boost down to 15 and the timing down to 17 and test the car with 93 only,no octane booster. Look at your narrow band and use the recall to see the lowest O2 value during a run. At 10.8 you are quite rich and should see an O2 reading of .820-.830 which is more evidence of how rich you are. Your O2 numbers should start in the .790-.800 range at the beginning of a run and drop to .770-.760 at the end of a full quarter mile dig. See how good you can get it to run this way and see how lean you can get before you see some retard,then add the plate and see if it helps. Get it to run as clean as you can with the plate,then add octane and turn the boost up then add some timing. You need to get the engine to run good first before the plate and octane booster.
 

SteveZ82

Active Member
Just changed the plugs (Ngk ur5 at .030) and man it runs good. I did a wot and got 3.8 KR at 838 o2mv but it came down to 0 at around 790 o2mv. So, I’m curious if it pings quickly at first punch then settles down?

Anyway. The car is running really good and I’ll tweak it when I can. I’m actually hitting about 17.5 psi boost so I’m going to turn it down per the recommendations. It’s turn counter clockwise one full turn = -1 psi, right?


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dynoman

Well-Known Member
I’m curious if it pings quickly at first punch then settles down?
Try rolling into the throttle ( in third gear ) to WOT . That could be false knock if it happens when the trans shifts , tires spin , or the motor torquing over on original motor mounts , just to name a few .
 

SteveZ82

Active Member
Try rolling into the throttle ( in third gear ) to WOT . That could be false knock if it happens when the trans shifts , tires spin , or the motor torquing over on original motor mounts , just to name a few .

Forgot to mention. I get like 1 degree knock when rolling in throttle in 3rd but it goes away.


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SteveZ82

Active Member
So I put the power plate on. My turbo takes forever to spool and I’m only getting like 3-4 psi now. Am I missing something?


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SteveZ82

Active Member
Never mind. Had forgotten I turned the psi down. It’s back up and running great. No knock at 16psi. But now my exhaust loosened up at the cat somehow. Always something.


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Ttype6

Well-Known Member
Never mind. Had forgotten I turned the psi down. It’s back up and running great. No knock at 16psi. But now my exhaust loosened up at the cat somehow. Always something.


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Do you use a copper gasket at that connection?
 

SteveZ82

Active Member
I don’t remember if it’s copper or just a regular gasket. Anyway, the bracket broke off the pipe so gonna weld it up this week. I put a metal strap on as a temp fix.

Fixed the major problem with knock. The exhaust weld and valve covers and I’m finally done. Until something else breaks.


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Ttype6

Well-Known Member
I don’t remember if it’s copper or just a regular gasket.
You shouldn't need a gasket there and the worst gasket,as it relates to loosening,is the copper gasket because it is too malleable. If you use a copper gasket anywhere,it will loosen up. The header to head,turbo to header,and cat to y pipe connections had no gasket from the factory.
 

SteveZ82

Active Member
We put one on because it was leaking there. Anyway, the bracket broke so I need to find out why.


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SteveZ82

Active Member
Welp. Think it’s my motor mount. I have a set and when we tried to replace the passenger side, we couldn’t get it to fit. Do you guys know any tricks? I ordered the Duralast ones.


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SteveZ82

Active Member
Think what is your motor mount?

I think the reason the exhaust bracket cracked is because of the MM. honestly, not going to guess on that until I have it on the rack. The KR is 0 at WOT after the octane booster and power plate. I call this matter closed.


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Ttype6

Well-Known Member
I think the reason the exhaust bracket cracked is because of the MM. honestly, not going to guess on that until I have it on the rack. The KR is 0 at WOT after the octane booster and power plate. I call this matter closed.


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Do you have anything stopping the engine from rotating counterclockwise under acceleration like a strap or the RJC rear engine brace?
 
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