Im fighting knocks during hard downshifts. I heard about a "burst knock retard" setting? Do I have that on my 730 8D?
Cant find it.

Thanks

 

I couldn't find it in there, either.

Are you sure it's not a mechanical noise, triggering it?. Are you using a WB?, and does it show a leanness, or excesive richness?.

 

Im pretty sure its mechanical noise. When I downshift hard, I always get knock counts. Even if I downshift without touching the throttel ( tps 0 % ). WB shows no lean spikes.
If I downshift soft ( slip on the clutch ) then hammer it, no knock counts. Plugs shows no signs of detonation.
I increased the knock recovery rate to 110% that helped alot. But still those annoying spark retards where you really dont whant it.

Thanks

 

You might try putting a 45d elbow between the Knock Sensor, and the block. ie one that has both a male and female end to it.

The Mercury division has done done that for years (marine division engines).

Just be careful to continually check for detonation on the plugs thou.

 

ok grumpy. where can I get those elbows? or must I get a custom build one?

 

Just get a brass elbow from your local parts supplier.
It will have 1/4" NPT female on one end and male on the other. Assuming you can get that over there.

Make sure your RH motor mount is good too.
Exhaust not hitting anywhere.

 

Doubel cheked that. But its hard to see if anything is touching anything when the engines is not under load ( on jackstands ). But with no load the exhaust is free and the engine mounts is ok.
My guess is that this car ( my manual vette ) even got this behaviour stock. I never used my scanner software when the car whas stock.
Its a pretty big force "shock" when downshifting a manual car hard ( release the clutch at once ) from 2000rpm to 4500rpm and at the same time press the pedal to the metal. So the knock censor could pick up false readings.Correct me if im wrong but wount auto cars torque converter take up some of the "shock" and make the transition a bit smoother then a manual car?

thanks

 

AT will absorb most of it true. Depends on how high ther RPM is.

Put a jack under the RH pan rail and lift that side about 1/4"
or till it hits the stop tab or whatever your mount uses to limit travel. More than likely that is the source of the noise.
The interanal stop of the mount that is. It's close to the KS.

 

Ok so The interanal stop of the mount could couse this?
Must I get harder mounts? Perhaps the stock mounts are to "soft" for my new engine combo?

thanks

 

I couldn't say w/o seeing the mount.
And I doubt that if that is the source, that you can eliminate it. A different style of mount might help. But that can turn into a nightmare to test and be expensive too especially with your location. The elbow seems a better choice.

 

sounds wise.

Thanks for the tpis. I should look in to that.

 

I guess you could use brass, and maybe get some more dampening, but the GM one, was cast iron. Most any hardware store that sells gas fittings for appliances has them.

 

Do you still have the stock-style dual mass flywheel?

It is possible that you are "clanking" the two peices together on a hard shift whereas a softer shift can be absorbed by the internal springs in the flywheel. Stock DM clutches do not have sprung hubs - the flywheel performs this function. That metallic "clank" could be read as a knock. The same could also be said of the ZF - the HUGE spacing between the main and counter-shafts can make for some interesting noises.

 

Thats a whery interesting point. I thougt about that to.
I still use the DM flywheel, and its not brand new either.
And the ZF is sturdy but noisy.
The internal springs in the flywheel could be on its way out, making it more sensitve to hard downshifts.
It takes out around 3 degrees at hard downshifts, then it ramp the timing fast up and keeps pulling like mad ( knock recovery rate is set to 110% in the chip ).