Knock Retard

**4boostin** · 06-30-2015, 06:53 PM

I recently purchased a 2000 LS1 Formula (six speed and all stock) and installed an Aero Force gauge that I had in a super charged Regal GS. The gauge works great. Under full throttle going thru the gears I've noticed up to 3 or 4 degrees of KR when getting above 4000 RMP's. Is this normal for these cars, or is it something I need to be concerned about? I'm running the highest octane (91) available here in Utah. Having owned several forced induction cars (Turbo Buick Regals) it's been something I've always had to watch, especially when turning up the boost. I'm guessing a cooler thermostat and lower fan setting should help, but how tolerant to KR are these engines?

**pajeff02** · 07-01-2015, 02:51 AM

I always run a knock retard gauge on my panel display and have not seen it kick in at all. On a 15 year old car, carbon buildup in the cylinders isn't unexpected and that can have an impact. Not a bad idea to run the TC-W3 regiman of one (1) ounce of this type of two-stroke oil per every five (5) gallons of gas. The old school method for carbon removal is to fill a spray bottle with water and to mist it into the throttle body as the engine is running (no joke - it works!). You need to do this for a while but if you have ever seen a cylinder where a head gasket has failed and allowed coolant into the bore, the principal is the same and it cleans off all the carbon and deposits. Either method works and is much preferred over a harsh chemical cleaner such as Sea Foam.

**pajeff02** · 07-01-2015, 02:52 AM

BTW: Welcome to the site!

**4boostin** · 07-03-2015, 01:56 PM

Thanks for the info. How often do you run the outboard oil mixed with the gas as explained above? Is it a one time treatment?

**pajeff02** · 07-03-2015, 04:27 PM

I run it all the time in our cars.

Here is the thread: http://www.ls1.com/forums/f48/been-testing-oil-91206/

**2002ssslp** · 07-04-2015, 06:25 AM

I like to use Lucas Fuel System Treatment once or twice a month to keep everything nice and clean.

**pajeff02** · 07-04-2015, 10:23 AM

That works. I usually run Chevron Techron Fuel System Cleaner in our vehicles when we first acquire them.

**2002ssslp** · 07-05-2015, 08:29 AM

Originally Posted by pajeff02

That works. I usually run Chevron Techron Fuel System Cleaner in our vehicles when we first acquire them.

Techron is the best stuff on the market. I just wish it was not so expensive, that's why I buy the big bottle of Lucas. I wish Chevron would come back to the Northeast. How about free Techron with every fill up of supreme. Nice.

**4boostin** · 07-05-2015, 01:36 PM

Originally Posted by pajeff02

I run it all the time in our cars.

Here is the thread: http://www.ls1.com/forums/f48/been-testing-oil-91206/

Very interesting reading. Got some Super Tech TC-W3 at Walmart for $12 to give it a try. Thanks for the link.

**pajeff02** · 07-06-2015, 03:28 AM

Give it a tank or three and and let us know what you think.

**0rion** · 07-07-2015, 08:19 AM

are you sure it's all stock? How much timing are you seeing at WOT? What does your AFR look like? Few things could be causing knock. Some cars are just more prone to it than others but I would want to make sure someone didn't raise the timing via a handheld or something or has leaned the car out in some way before going any further. I have a 98 and fought KR quite a bit. I changed the sensors and harness over to the 99+ and reduced the sensitivity with no luck. I ran 100 octane through it to see if it was actual knock or false and determined it was false knock. Eventually I just turned the knock sensors off.

**4boostin** · 07-10-2015, 04:02 PM

Originally Posted by pajeff02

Give it a tank or three and and let us know what you think.

I notice the KR happening more often when the coolant temp is around 200 or above on the Aero Force gauge. I'll check the timing at WOT. I'm not sure how accurate the AFR is without a wide band O2, but I'll look at that too and report back.

**pajeff02** · 07-11-2015, 03:45 AM

Higher temps do equate to a greater tendency to knock. At light cruise our engine will run just over 40 degrees of advance, drop the hammer and the advance falls off, as it should. I have not paid attention to total advance at WOT once things stabilize.

**4boostin** · 07-11-2015, 07:04 AM

Originally Posted by 0rion

are you sure it's all stock? How much timing are you seeing at WOT? What does your AFR look like? Few things could be causing knock. Some cars are just more prone to it than others but I would want to make sure someone didn't raise the timing via a handheld or something or has leaned the car out in some way before going any further. I have a 98 and fought KR quite a bit. I changed the sensors and harness over to the 99+ and reduced the sensitivity with no luck. I ran 100 octane through it to see if it was actual knock or false and determined it was false knock. Eventually I just turned the knock sensors off.

Checked the WOT timing, and when I put the hammer down it was 32* and when the RPM's got above about 4500, it settled in at 27-28*. As for the AFR, the Aero Force gauge shows CMD / AF 13.6 and I'm not sure what that is or means. As for KR, I'm noticing it sometimes and especially when the coolant temp is 200 or above, and at the top of each gear. Premium gas here in Utah is 91 octane also, which doesn't help.

**pajeff02** · 07-11-2015, 08:32 AM

CMD is "Command Air Fuel" which is essentially the target the PCM is shooting for. At WOT, our CMD is more akin to 12.8 or so and when you get out of it she'll revert back to 14.7. Technically, with the ethanol supplemented fuels 14.4 would be the better number.

**Firebirdjones** · 07-11-2015, 02:01 PM

I believe the 98-00 models had about 28 degrees total timing at WOT in the stock tunes, and in 01 that was dropped to about 24 (cylinder head and cam change that year)

However I've never found it possible to run 27-28 degrees in our 2000 even with a more aggressive camshaft. We also run 91 octane here. I have the tune at about 22 degrees timing in the high torque areas (around 3800 to 4500) and above 4500 I bumped it up to 24. I might get 1 or 2 degrees of knock on a really hot Arizona day (100 degrees or more) but I don't worry about it.

I also run a cooler 170 stat and have the fans come on at anything above 182 ( think they are set at 182 and 190). All these things helped tremendously battling detonation.

Also sounds like your AFR is a tad lean at 13.6 WOT to be safe. The stock tunes are extremely safe and all of them I've seen always have a target WOT AFR of 11.5.

I shoot for mid 12's anymore because the 10% ethanol stoich is 14:1, not the 14.7:1 we are typically used to with real gas. So anything approaching a 13:1 AFR at WOT could be borderline. I play it safe and run a few tenths richer, the HP difference would be minimal. When I see 12.5 or 12.6ish' on the wideband, I call it good.

Keep in mind these engines don't need a ton of ignition lead to make power. They have a very efficient combustion chamber design with good mixture, so alot of timing just isn't necessary. Most cases you'll see anywhere from 24-30 degrees MAX.

**4boostin** · 07-12-2015, 01:58 PM

Where did you get a 170 stat? I've only seem 160 and 180?

**Firebirdjones** · 07-12-2015, 02:15 PM

Well, they call them 160's but they really aren't. Because of the way the LS1 stats are designed they don't even begin to open until about 168, and they aren't fully open until 175-76. They just can't operate like a "real" 160 stat that you would normally see on a gen 1 engine. So technically they are 170's in my book.

That's testing on the stove with a probe, but in the car it proved to operate just as it tested. Logging the car, on a cold day, the engine temp would fluctuate between 174 and 178 as the thermostat cycled. They call it a 160, but it's not.

My other classic cars that I run 160 stats in, on the same cold days, will run between 158 and 165, so they work as advertised.

**0rion** · 07-12-2015, 06:09 PM

Originally Posted by Firebirdjones

I believe the 98-00 models had about 28 degrees total timing at WOT in the stock tunes, and in 01 that was dropped to about 24 (cylinder head and cam change that year)

However I've never found it possible to run 27-28 degrees in our 2000 even with a more aggressive camshaft. We also run 91 octane here. I have the tune at about 22 degrees timing in the high torque areas (around 3800 to 4500) and above 4500 I bumped it up to 24. I might get 1 or 2 degrees of knock on a really hot Arizona day (100 degrees or more) but I don't worry about it.

I also run a cooler 170 stat and have the fans come on at anything above 182 ( think they are set at 182 and 190). All these things helped tremendously battling detonation.

Also sounds like your AFR is a tad lean at 13.6 WOT to be safe. The stock tunes are extremely safe and all of them I've seen always have a target WOT AFR of 11.5.

I shoot for mid 12's anymore because the 10% ethanol stoich is 14:1, not the 14.7:1 we are typically used to with real gas. So anything approaching a 13:1 AFR at WOT could be borderline. I play it safe and run a few tenths richer, the HP difference would be minimal. When I see 12.5 or 12.6ish' on the wideband, I call it good.

Keep in mind these engines don't need a ton of ignition lead to make power. They have a very efficient combustion chamber design with good mixture, so alot of timing just isn't necessary. Most cases you'll see anywhere from 24-30 degrees MAX.

I agree with this.....AFR commanded at wot should be 11.7. It's hard to really diagnose much AFR related without a wideband. On stock manifolds you can log O2 mv's and get ball park but not much better than that. I don't know why you would be seeing 13.6 commanded but I'm not familiar with your gauge or where it's getting it's data. Does that 13.6 cmd ever change? The timing will drop and settle like you saw and that's what we typically talk about is that advance once you get into power enrichment.
I can tell you what I would do if I were in your shoes. You have a couple options. Personally I bought ls1edit then went to hptuners and learned to tune my car myself. It's time consuming but there's literally hours and hours worth of reading material out there that will help you learn to tune it yourself. It sounds like you have an understanding of it to begin with and not knowing what you do/don't know you can make that decision. Your other option is to put a 160 stat in and get a mail order tune from frost. It's a quick and cheap way to get a good tune in the car. If you do the stat you won't see the decreased temps until a tune is done to adjust the fan settings so you're looking at one of those options to get the most out of it. You can also tell frost what's going on and he can do a few things to help with the knock with the fueling and spark tables as well as have the knock decay really fast so if you do get tip in knock it will go away almost immediately.