Detonation when shifting at high RPM.

[Innovator]

My Z detonates breifly but loudly when shifting at high RPMS.

When I hit the hext higher gear and mash the gas, I get a pretty lound but quick detonation that is very audible. It goes away in under a second or less, even when I stay on the gas.

I am using 93 octane fuel, that has 10% methanol from the refinery( Gulf) . It does it with other gas without alky in it too.

Does anyone else have this issue? Detonation that loud is bad news, as you all know....

[IT L GO]

How many miles on your car? You might be a candidate for a De-carbonization Procedure

http://www.corvetteforum.com/techtip...=212&TopicID=1

[Innovator]

Originally Posted by IT L GO

How many miles on your car? You might be a candidate for a De-carbonization Procedure

http://www.corvetteforum.com/techtip...=212&TopicID=1

Thank you for the tip. I now have 5500 miles on it, but it did it at 2200 when I got it.

I'm not sure if it's the gas, but since I've used a few types, I'm leaning against the gas. Vararam? Maybe. Although, I've never seen an air cleaner make so much of a difference, as to lean out the engine.

BTW, a product called Sea Foam is the best decarbonizer I've used to date. We use it at my shop on cars that run 87 octane that have a detonation problem, and it makes a huge difference after the treatment.

We suck it through the PCV hose slowly at first, and then towards the end of the bottle, we let it go through at full blast until the engine stalls. Then we let it sit for as long as possible (overnight if possible). Then we give it a (Polish Tune-up), which involves some WOT in a few gears

[JDBgn]

Sounds like you are hitting the rev limiter which cuts off the engine at 6500 RPM.
Shift just below that and you will get the best performance as far as speed goes.
You should not have carbon build up, that was with leaded fuel and before fuel injectors.
MHO

[Innovator]

Not the rev limiter. It's detonation for sure.

[C5 CU]

any mods or tuning done to your car....possibly need to back off a bit on timing?

[Innovator]

Originally Posted by C5 CU

any mods or tuning done to your car....possibly need to back off a bit on timing?

Basanni H pipe and Vararam 2B.

[niphilli]

Could be throttle tip-in (part throttle tuning). Most tuners only mess with WOT tuning but tip in has to be adjusted sometimes. I can imagine having these issues with a car lightly modded like yours though. Is the car under warrenty? If so take off the Vararam and take her in. Actually take off the vara ram first and see if it goes away.

[OhOneZOhSiXXX]

Originally Posted by Innovator

My Z detonates breifly but loudly when shifting at high RPMS.

When I hit the hext higher gear and mash the gas, I get a pretty lound but quick detonation that is very audible. It goes away in under a second or less, even when I stay on the gas.

I am using 93 octane fuel, that has 10% methanol from the refinery( Gulf) . It does it with other gas without alky in it too.

Does anyone else have this issue? Detonation that loud is bad news, as you all know....

Experienced same thing on dyno...
We changed the plugs and wires and it went away.

Good luck

[Innovator]

Originally Posted by OhOneZOhSiXXX

Experienced same thing on dyno...
We changed the plugs and wires and it went away.

Good luck

I have the new AC Iridium plugs installed. The wires though? With 5500 on the odo? What would that do?

[OhOneZOhSiXXX]

Originally Posted by Innovator

I have the new AC Iridium plugs installed. The wires though? With 5500 on the odo? What would that do?

mine had less than 4k...both plugs and wires...granted they were not iridium (which is what we switched to) but detonated nevertheless.

maybe changing the wires will have no effect...i dont know...we changed both simultaneously.

its a cheap suggestion. thats all.

worst case: it doesnt work, and you have a spare set of plugs and wires (which you will probably need anyway, especially if you have/are considering getting headers)

good luck