Slight Knock

SteveZ82

Active Member
In the times of quarantine, I get to work on my TR more than ever now. Finally got the scanmaster permanently installed along with the original radio. You need tunes man. Speaking of tunes. I am getting some small knock in about 16-17 psi of boost (no higher than 3). My AFR wideband shows good numbers (11-12) so curious if it's real knock or not. I've been in and out of KR posts here but a lot of heavily modified engines. My setup:

42lb injectors
Fuel Pump hotwire kit (previous owner did it and forgot which one it was, Racetronix?)
Stock turbo with 3in downpipe
16-17 psi
Turbo Tweak chip (5.6, 42# STREET 93 - 20/18 degrees - 16-18 psi)
Applied Tech cold air kit

I run 93 in her, just fixed the DS header and new crossover. I get a very small exhaust leak at the flange but it goes away once it warms up. The down pipe leaks a bit of water when I first start it up near the turbo which to me doesn't seem right. Looks to be coming out of the flange (gasket?). New PCV valve.

Just wondering what else to check? Everything I read about knock seems to indicate timing and fuel. I'm getting great pressure. I have some new NGK UR5 plugs to put in which are colder than the current ones, would that help? Does gap matter for KR? I did notice at the inlet pipe, at one point it looked to have rubbed up against the alternator fan blade and my heat shield rattles but only at idle.

Car runs great so want to keep it that way. I don't race it but like to open it up now and then. Don't want to blow it up just yet.
 

Turbo6inKY

Short Guy
If, as you say, your AFRs are good and your fuel pressure is good, and you don't have something flapping around causing a false knock signal (tires breaking loose?, bad motor mount?) then back off the boost and see if the knock goes away.

I ran a chip similar to yours back before I went nuts with the car, and I had similar issues. The 42# chip at 20/18 and 17psi was right on the limit of what the fuel sold around me could stand. A winter time blend of 93 (non-RFG) would work, but in the summer it'd ping. A quarter can of Boostane to each tank in the summer was usually enough to goose the fuel octane up enough to get it to stop.

Contrary to some of the long-standing advice, It's my opinion that any knock is too much. A single detonation at the wrong moment or location in the chamber can crack a piston or wipe out a rod bearing. So you are wise to hunt this down.
 

Ttype6

Well-Known Member
Mix 1 gallon of xylene to 3 gallons of 93 (100 octane) and add to an empty tank and see if the knock goes away. If it does,turn the boost up to 20 psi and have some fun. If knock goes away with the mixture,you will know that the knock is real. If you prove the knock to be real,turn the boost down to 16 when you run 93. If you still run the EGR,check the number 1 spark plug to see if that cylinder is very rich. The heat from the EGR messes with the wiring that goes to the number 1 injector causing it to spray too much fuel. The wideband sees the correct air fuel mixture from an average of one rich cylinder and 5 lean cylinders. You can only run as much boost as your leanest cylinder/cylinders. At your power level,you should be able to run leaner than you are.
 

SteveZ82

Active Member
Thank you both @Ttype6 and @Turbo6inKY. I'll try some octane booster. When I checked the plugs before, some had a little pink hue to them which could indicate additives were used before. Anyway, the previous owner did a really good job maintaining the car with all the right upgrades. He seemed to care more about the stereo I think and treated the car as a cruiser.
 

Turbo6inKY

Short Guy
Thank you both @Ttype6 and @Turbo6inKY. I'll try some octane booster. When I checked the plugs before, some had a little pink hue to them which could indicate additives were used before. Anyway, the previous owner did a really good job maintaining the car with all the right upgrades. He seemed to care more about the stereo I think and treated the car as a cruiser.

MMT (the additive in Boostane and a few other octane boosters that actually work) causes an orange deposit that fades to pink if you run without it for awhile, so that's a good indication the previous owner was using it to get some extra octane.
 

Ttype6

Well-Known Member
He seemed to care more about the stereo I think and treated the car as a cruiser.
I've never been able to enjoy my sound system while the car is running since I got rid of the catalytic converter. Do you still have the converter?
If you don't want to spend $20.00 on a gallon of xylene and would rather use an octane booster,Lucas is very effective as is any booster that contains MMT. It will coat the combustion chamber with a rust color which harms nothing.
 

SteveZ82

Active Member
I've never been able to enjoy my sound system while the car is running since I got rid of the catalytic converter. Do you still have the converter?
If you don't want to spend $20.00 on a gallon of xylene and would rather use an octane booster,Lucas is very effective as is any booster that contains MMT. It will coat the combustion chamber with a rust color which harms nothing.

He actually had this old Alpine in there, with 2 amps, the 2x12" woofers are still in there but not hooked up. I was bored yesterday so I fixed my saggy DS door and put in the radio from an 87 that I got from someone here. Removed the amps and used a little 9V to find out which speaker was which. I wasn't a fan of his wiring method so I cleaned that up. He ran his own wire. Don't ask me why. Anyway, I thought it sounded much better with the stock radio. I turned that down after a while because my SS magnaflows and that turbo whistle is music to my ears.

Yeah, I have the CAT still. Thanks again, I'll order up some boostane.
 

Pronto

You can't knock them up with spit.
I would run the gap at 28. Add octane. If you don't need the cat for inspections then either pull it and beat the guts out it or get a straight pipe.
 

Ttype6

Well-Known Member
Yeah, I have the CAT still. Thanks again, I'll order up some boostane.
I can't imagine that they give boostane away. You could get a gallon of xylene today at your local hardware store. It's very clean and smells good and is one of two aromatic hydrocarbons typically used to increase unleaded fuels octane by the refineries. The 93 octane fuel that you use probably has some toluene added to it to achieve the 93 octane. You can also buy toluene at your local hardware store. The reason I mentioned xylene is because it has a little higher octane rating of 117.

The problem with removing the catalytic converter,as it relates to the sound system,is that the drone cancels out the base notes in the music.
 

Turbo6inKY

Short Guy
I can't imagine that they give boostane away. You could get a gallon of xylene today at your local hardware store. It's very clean and smells good and is one of two aromatic hydrocarbons typically used to increase unleaded fuels octane by the refineries. The 93 octane fuel that you use probably has some toluene added to it to achieve the 93 octane. You can also buy toluene at your local hardware store. The reason I mentioned xylene is because it has a little higher octane rating of 117.

The problem with removing the catalytic converter,as it relates to the sound system,is that the drone cancels out the base notes in the music.

Xylene is dramatically more expensive.

A case of Boostane costs ~$120. That's six bottles. Half of each bottle raises a tank of gas from 93 to 100 octane. At 17 gallons per tank, that case of Boostane will raise 204 gallons from 93 to 100 octane. That's $0.58 per gallon premium over the price of the 93 octane. 93 is $2.50 here right now, so that cranks it to 3.08/gal for 100 octane.

Doing it with Xylene? The ratio for 100 octane from 93 octane gas is 3 parts Xylene to 7 parts gasoline. So to get 204 gallons of 100, you need 61 gallons of Xylene and 143 gallons of gas. Xylene's $20 a gallon around here. That puts you at $7.73/gal to do it with Xylene.

The Boostane is a much better deal.
 

Ttype6

Well-Known Member
if you have a Sunoco near by with 106 0r 110 ...put 5 gallons of it in with your normal 93 ...and it'll be right for the good fight
The first time I tried leaded fuel,The SES light came on before the day ended. Oxygen sensor was ruined. Then I bought a Denso sensor and it handled the leaded fuel for a year.
 

wb_7354

Active Member
Any Kr is bad. Never assume it’s false. Take 1-2* of timing out and see if the kr goes away. Check all the vacuum lines as a leak will result in a lean reading. Ideally you want the af ratio to be between 10.8-11.2 personally I like to run rich.


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Turbo6inKY

Short Guy
Right,but you can't get it today.

Ounce of prevention is worth a pound of cure. At this point, none of us should be daily driving these or otherwise depending on them for transportation. Parking it a week to save 50% on fuel seems like an easy thing to do.
 

SCOOBY DOO

I'M NOT A MONSTER, I'M JUST AHEAD OF THE CURVE!!!
17 PSI is pretty much the limit for 93. Post your BLM idle number from your SM with the engine warmed up...and find out if you have an exhaust or air vacuum leak. I assume you have your fuel pressure set at 43 PSI line off. I also assume your FP is rising 1 for one with boost. Any KR...is bad. And how old is the fuel pump?
 

SteveZ82

Active Member
17 PSI is pretty much the limit for 93. Post your BLM idle number from your SM with the engine warmed up...and find out if you have an exhaust or air vacuum leak. I assume you have your fuel pressure set at 43 PSI line off. I also assume your FP is rising 1 for one with boost. Any KR...is bad. And how old is the fuel pump?

FP is right around 43 with the line off. I need to get another FP gauge to monitor in boost. The pump, no clue, I'm guessing 10+ years old. My BLM at idle when warm was 126 yesterday. I do have a small exhaust leak that seals up when warmed up near the flange of the poston style header on the DS. I've checked and checked vacuum lines and they all look good.
 

Pronto

You can't knock them up with spit.
Be very careful with Boostane and xylene. Don't let a drop get on your skin. I got a little Boostane on my hands when I tried some trying to solve a knock issue. Big mistake. Within minutes I felt sick. Took all day to feel right. It's very toxic!
 
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