question regarding knock - for tuners

birk1 · 01-02-2010, 02:59 PM

okay...question about knock vs false knock

I just added about 3.5 lbs of boost = total of 9.8-10lbs of boost at WOT

the specs for my car are: LS3, 1 3/4 headers, catless, cam (223/240 .610 112 LSA) PISC with a 4 inch pulley, dallas big mouth intake

Running on 91 octane fuel with no meth

before I pullied down I had a peak RWHP 618 with no knock and really no issues with 6.5 lbs of boost.... So I decided to add some boost and now I could only get an extra 30 HP (645 total) from over 3 lbs of added boost - and in the process I am now seeing knock and my timing is getting pulled. I expected better numbers - but the engine is cooperating.

how can I spot false knock from extra noise due to the added boost vs the real thing?

experience needed

Ryan

Slvr08Z51 · 01-02-2010, 03:23 PM

Dude.. that isn't opportunity knocking.. Knock is BAD! Most likely it's not false knock.. Get it tuned properly and keep it alive!!

Taylor@DallasPerformance · 01-02-2010, 04:55 PM

Hey Ryan, are you doing the tuning yourself or working with a shop experienced with boosted LS engines?

user_name · 01-02-2010, 05:02 PM

With those specs I doubt it's false. You need more octane or less timing/boost.

zeshawn · 01-02-2010, 05:58 PM

again, its not false knock.

3.5lbs is not little, and it seems the car wasnt tuned after the pulley swap - at least you made it sound that way. Check ur AFR for starters make sure its in the low 11's, and work out the timing until you stop seeing any knock. Knock pulls a good deal of timing and can lower you're max power. Lower timing and NO knock retard will likely result in higher HP.

But again, 91 octane and 10psi of boost? people usually run meth with that kind of boost/cr/fuel, the LEAST thing you can do is switch to 93, and tune it for 93.

Or back off boost.

carlrx7 · 01-02-2010, 06:11 PM

more boost = less timing
more boost = more heat
more heat = less timing
more boost = more heat = less timing x2

put that meth kit on you have been staring at in the garage.

p.s. the false knock would of been there before pulling down the supercharger.

usually caused by noisy valve trains and sloppy exhaust installations

birk1 · 01-02-2010, 06:23 PM

thanks guys for the response

the car was dyno tuned after the pulley down

-91 octane is the best we have in Oklahoma

-afr is 11.8

-the meth kit might be an option, I just wanted to make it a daily driver and not worry about an additional system

-I was wondering about false knock because it wasnt seen before the addition of boost...but as stated the added boost added heat, so that might be the issue

-the shop has some limited experience with boosted LS engines...but not much...thats why I am asking questions to learn

---> final question - I had a procharger big red valve installed on my intake pipe right before the MAF...could that be causing any problems?

zeshawn · 01-02-2010, 06:30 PM

Quote:

Originally Posted by birk1

thanks guys for the response

the car was dyno tuned after the pulley down

-91 octane is the best we have in Oklahoma

-afr is 11.8

-the meth kit might be an option, I just wanted to make it a daily driver and not worry about an additional system

-I was wondering about false knock because it wasnt seen before the addition of boost...but as stated the added boost added heat, so that might be the issue

-the shop has some limited experience with boosted LS engines...but not much...thats why I am asking questions to learn

---> final question - I had a procharger big red valve installed on my intake pipe right before the MAF...could that be causing any problems?

before the MAF is fine, anything between the MAF and throttle body will cause an issue.

Again, its not simply a heat issue, the more boost you run the less timing you can run. with a high comp ratio engine, and that much of boost on 91 octane, how much timing are you running? Ill bet its VERY low.

youd probably gain 50+ rwhp with the meth kit and ur current boost, set it to kick in at 6.5psi whihc should be at around `4500rpms?

birk1 · 01-02-2010, 06:35 PM

Quote:

Originally Posted by zeshawn

before the MAF is fine, anything between the MAF and throttle body will cause an issue.

Again, its not simply a heat issue, the more boost you run the less timing you can run. with a high comp ratio engine, and that much of boost on 91 octane, how much timing are you running? Ill bet its VERY low.

youd probably gain 50+ rwhp with the meth kit and ur current boost, set it to kick in at 6.5psi whihc should be at around `4500rpms?

thanks for the info!

I believe am at 11degrees of timing...does that sound right?

I might just move over to meth kit...thinking about it

Taylor@DallasPerformance · 01-02-2010, 06:53 PM

Quote:

Originally Posted by birk1

thanks for the info!

I believe am at 11degrees of timing...does that sound right?

I might just move over to meth kit...thinking about it

Sounds a little high for 91 octane and 10 psi.

Do you have HPTuners? If so I can walk you through taking a log and I will take a look...

We have the methanol down to a science. Make sure you do a Alky Control kit and don't look back. It is very low maintenance if it is done right...

bullitt4110 · 01-02-2010, 11:28 PM

If you use the washer tank (whihc is rather large on the C6) and leave the low fluid sensor plugged in you should not run into any problems running the meth, remember its only spraying a small amount when you are above the preset level therefore lasting quite awhile.

Taylor@DallasPerformance · 01-02-2010, 11:32 PM

Quote:

Originally Posted by bullitt4110

If you use the washer tank (whihc is rather large on the C6) and leave the low fluid sensor plugged in you should not run into any problems running the meth, remember its only spraying a small amount when you are above the preset level therefore lasting quite awhile.

There is a bit more to it than that, but that's a good start!

bullitt4110 · 01-02-2010, 11:37 PM

Ya I know, I think most people think they are going to go through it like they go through gas and have to fill it up all the time which kind of scares them away from it, which isnt the case.

user_name · 01-02-2010, 11:47 PM

Quote:

Originally Posted by bullitt4110

Ya I know, I think most people think they are going to go through it like they go through gas and have to fill it up all the time which kind of scares them away from it, which isnt the case.

Some of us use enough that it is like that.

Slvr08Z51 · 01-02-2010, 11:55 PM

Quote:

Originally Posted by user_name

Some of us use enough that it is like that.

Been through 7 gallons in 2 mos!!

My daily went down so I've been beating the hell out of the Vette!! Actually made 4 180+ pulls today!! Had to show a HPF Stage 3 M3 whats up!

bullitt4110 · 01-03-2010, 12:11 AM

Quote:

Originally Posted by user_name

Some of us use enough that it is like that.

Quote:

Originally Posted by Slvr08Z51

Been through 7 gallons in 2 mos!!

My daily went down so I've been beating the hell out of the Vette!! Actually made 4 180+ pulls today!! Had to show a HPF Stage 3 M3 whats up!

The majority dont but there a few that do...

Taylor@DallasPerformance · 01-03-2010, 12:29 AM

Quote:

Originally Posted by Slvr08Z51

Been through 7 gallons in 2 mos!!

My daily went down so I've been beating the hell out of the Vette!! Actually made 4 180+ pulls today!! Had to show a HPF Stage 3 M3 whats up!

You were running out of airstrip quick at 180+

Slvr08Z51 · 01-03-2010, 12:55 AM

Quote:

Originally Posted by Taylor@DallasPerformance

You were running out of airstrip quick at 180+

Lol! So you did see the video!