Warm(er) Air Intake for the 1999 LeSabre - 1st Attempt

[Christ]

Originally Posted by MadisonMPG

Does the 3800 really knock when it is cold?

Some do, some don't. The SC motors, that I know of, never did, but I believe they had lower compression, as well.

3.4's sometimes knock a bit as well on 87 octane, the fix is to spray warmed water from a spray bottle into the intake for about 5 minutes after it's warm. You'll see the carbon crap come out the exhaust.

[99LeCouch]

It shows up on my ScanGauge as timing pulled because of knock. I remember one 15*F night last winter blasting down the freeway and seeing a constant 2-2.5* of timing pulled because the computer was detecting knock.

I have the naturally aspirated 3800. The supercharged ones do knock as well. Battling knock is a constant struggle in the 3800 community.

My engine should be pretty clean. I've been running a dose of Marvel Mystery Oil in the gas for the past few thousand miles. I forgot it this tank, and the car's letting me know.

When I hooked my SG up to my brother's 3400 powered minivan, that thing knocked up a storm on 87 octane.

[IsaacCarlson]

But I don't have a Scanguage either. Want one though. I always run premium anyway, but even when I used to run regular, it never knocked.

[Christ]

You could try unplugging the knock sensor and see how performance/economy is affected. I don't know if the ECM requires the feedback or not. If it does, consider removing it and placing it somewhere other than the engine.

[moorecomp]

I recently thought about doing a very similar mod. I was thinking of taking the return line from the existing heater core, and cutting it. Then run one side of the return line to the intake of the air box heater core and the outlet to the other side of the return line. Basically put the new one in series with the return line from the existing heater core. To control the temp, I would use a flapper valve in the airbox, controlled by a push/pull cable. No need for a flow valve.

[99LeCouch]

Originally Posted by Christ

You could try unplugging the knock sensor and see how performance/economy is affected. I don't know if the ECM requires the feedback or not. If it does, consider removing it and placing it somewhere other than the engine.

I can feel the engine pull timing and spark advance at times. It's staying plugged in. I'd save a bit in fuel and be spending $500 for a new engine when it predetonated hard enough to cause damage.

This engine is fickle. I'll see what this airbox does.

[Christ]

Originally Posted by 99LeCouch

I can feel the engine pull timing and spark advance at times. It's staying plugged in. I'd save a bit in fuel and be spending $500 for a new engine when it predetonated hard enough to cause damage.

This engine is fickle. I'll see what this airbox does.

I respect your choice, but I will note that often, the knock sensor will pull timing "just for the hell of it". IOW - the engine runs a bit different than it did when it was new, and the new pattern of resonance just happens to fit what the knock sensor is looking for. It's happened. Alot.

But, there's nothing wrong with not wanting to risk it!

[99LeCouch]

Thanks for the info about the knock sensors! Your statement does explain some behavior of the car. Sometimes, like when going uphill, it definitely knocks. Other times, like taking off from a stop gradually, it'll pull 12-14* of timing randomly.

Driving around tonight, the air temperature stayed pretty constant at +40 over ambient. At least for in-town driving, it's a success. Highway will wait until Saturday.

[dwtaylorpdx]

I've gotten better behavior out of knock sensors by taking them off and cleaning the sensor and the mounting surface well. (The threads in the block if its a threaded in type.)

Also if your sensor is in the head, make sure you have no rocker noise, it will casue issues.

Dave

[99LeCouch]

Hmm, maybe some DynaMat around them is a good idea...