Knocking after mods?

Reply Subscribe

Thread Tools

Search this Thread

Aug 5, 2003 | 11:09 PM

andy82

Thread Starter

Safety Car

Joined: May 1999

Posts: 4,693

Likes: 10

From: Carefree, Arizona

2017 C7 of Year Finalist

Knocking after mods?

Recently I did the folowing mods to my 2002 which seem to have improved HP and torque :D :

- induction grilles, Blackwing filter, power duct and coupler, shorty headers, X-pipe and Borla Stinger 4 tip

However, when I had my baby dyno'ed (330 HP/350 fp/torque, 4th gear WOT) we noticed knocking at around 4000 rpm, which I never heard before. The computer of course tried tried to correct by adjusting the ignition timing and screwed up the curve. :cuss

A friend of mine mentioned that knocking is a result of a lean air/fuel mixture and could be corrected by either programming the chip or buying a MAF translator. However, on the dyno diagram the air/fuel ratio drops at around 2500 from 15 to 13 and stays there until 5000 rpm, then it drops to 12.

Any ideas if this would be the way to go?

Save the Wave, :thumbs:
Andy

Aug 6, 2003 | 03:58 AM

pkmoose

Le Mans Master

Joined: Aug 2000

Posts: 6,447

Likes: 0

From: Scottsdale, AZ

Cruise-In III Veteran

Re: Knocking after mods? (andy82)

If you have some miles on it, it could be carbon buildup caused by excess oil being introduced into the combustion chamber. Also, are you sure there aren't any small animals in the intake, they usually get excited around 4000 rpm and start to bang on the drums with glee (or so I'm told).

Aug 6, 2003 | 06:22 PM

Bink

Safety Car

Joined: Mar 2002

Posts: 4,928

Likes: 1

Cruise-In V Veteran

St. Jude Donor '09

Re: Knocking after mods? (pkmoose)

Also, are you sure there aren't any small animals in the intake, they usually get excited around 4000 rpm and start to bang on the drums with glee (or so I'm told).

:lol: :lol: :lolg: :lolg: :lolg:

Aug 6, 2003 | 06:26 PM

TIKTGTR

Melting Slicks

Joined: Oct 2002

Posts: 2,151

Likes: 1

From: N.CHARLESTON SC

Re: Knocking after mods? (binksZ06)

Why did you go with shorties? Do you like them? I'm not sure which I'm gonna go with! :cheers:

Aug 6, 2003 | 07:12 PM

sebrock

Racer

Joined: Jul 2003

Posts: 421

Likes: 0

From: Bethesda MD

Re: Knocking after mods? (andy82)

I might be having a similar problem. Did you actually hear the knocking and after 4000RPM did your Dyno graph zig-zag in 50RWHP increments?

Aug 6, 2003 | 10:30 PM

NICEDRV

Burning Brakes

Joined: Apr 2001

Posts: 924

Likes: 36

From: Pinehurst, NC

Re: Knocking after mods? (sebrock)

After I had headers and exhaust installed I had a tapping sound. We found a crack at the weld of the headers to exhaust. Rewelded and sound went away.

Aug 7, 2003 | 12:15 PM

andy82

Thread Starter

Safety Car

Joined: May 1999

Posts: 4,693

Likes: 10

From: Carefree, Arizona

2017 C7 of Year Finalist

Re: Knocking after mods? (sebrock)

I have a zig-zag in the line above 4000 rpm, not to the extend of 50rhp but you can see it.

Aug 7, 2003 | 12:19 PM

andy82

Thread Starter

Safety Car

Joined: May 1999

Posts: 4,693

Likes: 10

From: Carefree, Arizona

2017 C7 of Year Finalist

Re: Knocking after mods? (TIKTGTR)

I like the short headers PLUS they are street legal. Not sure how much more torque/hp long tube headers would gain, but in my opinion its not worth the risk :blueangel:

Andy