Rattling Downpipe - false knock gone.

[b4black]

I alwasy suspected that my downpipe could be hitting somethng abd causing false knock (a common problem on 86/87 cars). When I installed my Casper's knock gauge, it became even more clear, because I could see the LED's light up exactly when it shifted. I was changing my plugs the other day and I found that the stock downpipe was resting against the header/crossover flange. If I shook the DP at the bottom where it meets the converter, it would bang. There is VERY LITTLE room between the DP and the header/crossover.

I bought a 7½" turnbuckle with a hook and an eye (loop). I bolted th eye to the DP/converter lange and hooked it to the frame. I was able to pull the DP away from the header flange. It has cured almost all of the shift knock.

I have a polyurethane motor mount to install which should keep the motor from flopping around. That should take care of it all.


I would suspect that with the little amount of room for the DP and ~20 years, that most cars will have some problem with this.

 

[fc227]

That will do it. Do you have Poly mounts on the tranny also ?

 

[Ttype83]

My down pipe touchs my up pipe....I guess I will have to fix it...darn...Well I need to work on the exhuast anyhow.
I love the ploy mounts, but now with the cam I get a viberation while at a stop.
I also need to tie down the emission pipe that went to the cat...I'm thinking of turning it to toward the turbo to help cool it.
Do you think it will help??
Jim

 

[fc227]

The air pump outlet?

 

[Ttype83]

Originally posted by fc227
The air pump outlet?

Fred,
Yes the air pump outlet. It connected to a one way valve on the back of the intake before going down to the cat. I need to remove the pipe going down to remove the rattle. And thought the I could turn the pipe were it conected to it.
Jim

 

[fc227]

If there air pump is not really be used , why not take the pump off altogether ? or is it still pumping into the intakes crossover ?

 

[b4black]

I don't have a poly trans mount, just the DS motor mount.


I don't need my AIR tube to my cat anymore, but I kinda don't want to remove it. I could be a pain to put it back later.

Without needing the AIR pump for the cat, the rest becomes (almost) un-needed as well. The only time the AIR pump goes to the back of the intake is cold start/open loop. Altough I'm not big on removing emmisions, the pump, valves, and all that plumbing could be done away with.

I'm pretty sure that aftermarket cats don't use the AIR tube. If that's the case, then the AIR pump could be removed and the car will still pass emissions testing. (It might be good to leave the pump itself in place as an idler pulley for the alternator belt.)


As for cooling the turbo, the air pump effluent may be fairly warm. I have tought about running dryer duct to the turbo the way most people run it to the air filter. Just pull it from the other side of the engine compartment.

 

[Ttype83]

I'm with Rich on this....If I remove it I have to redo the belts and If I need it later I would have to put it back on and it's a fairly new pump. hummm pumps warm air, bummer.
I thought about the duct on that side too, but for it to work the best the hot air would have to flow out. So with that reasoning, You would need a shield to cover the turbo and connect a front and back duct to. Secound problem would be were to put the back duct...there's not a lot of room back there. Third problem would be sitting with a shield on a hot turbo, you would need air pushed though at idle.

OK here's another idea..don't laugh..

We need cold air..what about intalling a A/C condser in front of the air box. It would suck in the cold air and cool the charge. This of course could not be run all the time only at WOT at the track and only if it's already warm outside. Cooler fall weather it would be of no use....Unless you installed it to work with the duct work on the turbo.....uhm
OK I'm done rattling on...

 

[fc227]

Thats not a silly Idea, But would the compressor may draw more power than you gain with the cold air?

 

[b4black]

I think it would be worthwhile to install a thermocouple (or maybe even a MAT sensor from another car) and get actual readings of the incoming temps. Then you can find out which things are the most effective. There is some point where it could be too cold.


With the dual channel thermometer you couple read EGT and incoming air temps. Or better yet, put the thermocouple in the intake so you could read the temps after the turbo heats it up. That's the temp your really interested in.

The 82/83 compressor has a boss that could be drilled/tapped in the compressor foot. You could read temps here. (Good place for water injection too.)