Tuning for zero knock retard - how to?

T

Timbuick

Member
Joined
Oct 5, 2009
Guys, I know that this is almost the 'Holy Grail' of turbo Buick questions, but despite searches and much reading, I can't find a step by step guide.
Is there a sticky on this somewhere?
With my new TT5.6 chip i'm getting kr when downshifting at open throttle. No problems when building boost gradually in third gear.
In the meantime, i'm keeping my foot out of it whilst I try to learn more!:confused:
 
try this site

www.vortexbuicks-etc.com

read it theres a good tuning section

knock on a downshift is usually driveline related false kr but without looking at logs of what the o2s and the KR look like i cant say for sure that its not the tune or engine mechanical related
 
Timbuick said:
Guys, I know that this is almost the 'Holy Grail' of turbo Buick questions, but despite searches and much reading, I can't find a step by step guide.
Is there a sticky on this somewhere?
With my new TT5.6 chip i'm getting kr when downshifting at open throttle. No problems when building boost gradually in third gear.
In the meantime, i'm keeping my foot out of it whilst I try to learn more!:confused:
Click to expand...

KR on the downshift happens on a lot of cars, but it is false. You can get a patch that ignores knock when it senses the 3rd gear selector goes off.. the extender chips have this feature, and Eric can burn this feature on the chip as well.

To tune for zero knock, you need to start at a boost level that the engine should support based on available octane and timing in the chip.

Lets say 14 PSI. So you run the engine at WOT at 14 PSI and make sure there is no KR. Then turn up the boost to 15.. repeat.. then 16, then 17, etc. When you start seeing a little KR..like 1-2 degree's then is when the tuning starts. At that point your options are three.. add fuel, drop timing, increase octane...
 
I wondered about false knock, but couldn't afford to ignore any kr that was showing. There are no audable knocks from the drive line, but i see what is being suggested. I have a shift kit in the trans that gives very firm shifts, but the kr starts to show after the downshift as i accelerate hard.

I understand that without full scan figures Its hard to tell. I wondered about adding more fuel via the chip at WOT settings?
 
You can add all the fuel you want, but the "bang" sound the tranny makes when it applies the 2nd gear band on the drum.. cuases the knock to go off.. nothing you can do on that one. Unless changes are made to the trans to soften that hit when it happens. And fuel wont stop that knock.

One thing you can do is down shift the car into 2nd(2), then romp into it.. then shift into 3rd(D).. you wont get any knock that way.
 
Hmm, so if I manually shift I can avoid detonation (or percieved deonation)?
That does appear to be the case currently.
If that is so, are we suggesting that the downshift from O/3D to 3 is false knock?I presumed that under WOT the fuel requirements were going lean as the car shifted from O/D to 3rd?
 
Razor said:
KR on the downshift happens on a lot of cars, but it is false. You can get a patch that ignores knock when it senses the 3rd gear selector goes off.. the extender chips have this feature, and Eric can burn this feature on the chip as well.

To tune for zero knock, you need to start at a boost level that the engine should support based on available octane and timing in the chip.

Lets say 14 PSI. So you run the engine at WOT at 14 PSI and make sure there is no KR. Then turn up the boost to 15.. repeat.. then 16, then 17, etc. When you start seeing a little KR..like 1-2 degree's then is when the tuning starts. At that point your options are three.. add fuel, drop timing, increase octane...
Click to expand...

This is exactly how i do it. Could'nt have explained any better myself. Could the car be boost spiking on the downshift causing knock?
 
V8Killer said:
This is exactly how i do it. Could'nt have explained any better myself. Could the car be boost spiking on the downshift causing knock?
Click to expand...

Possible. But you need to look at your boost guage and O2's to see what the deal is. If O2's are high, and boost is stable.. you sir have false knock.

Another way, drop 20 bucks of race gas in the tank and go for a ride.. see if the problem goes away. If it doesnt there you have your answer.. cost you 20 bucks.
 
Razor said:
.............. When you start seeing a little KR..like 1-2 degree's then is when the tuning starts. At that point your options are three.. add fuel, drop timing, increase octane...
Click to expand...

Uhhmmmmm . . . or turn up the PAC. :tongue: (adding fuel in a sense:wink:)
Sorry, couldn't resist the temptation . . .
 
Thanks guys, that helps me understand more, Here in the UK I have 97 octane fuel, but read somewhere that UK/USA octane rates aren't directly comparable.
Meantime i'll get some better data, especiallly 02 numbers and report back.


Funny thing, the previous owner thrashed this car quite happily with no scanmaster at all. so did I for the short time before I fitted the scantool.
Now I have numbers to read. Maybe ignorance is bliss......until it goes bang:eek:


Erm, whats a PAC? (thought they were used for channeling funds for election campaigns;)}
 
He's refering to the alcohol injection knob that dumps more fuel in when cranked up ;)

Best way to get rid of knock is get rid of the sensors :eek: Once you pay attention to them, you know whats really up.. and make those decisions. These motors are tough to hurt at stock boost levels.
 
Yes, it did occur to me that my motor is not far off stock and i really shouldn't be able to hurt it at the current level of tune and with decent fuel.


got the PAC bit now, may well look at alky for the new year.
 
When tuning for no knock, the first thing to do if knock is detected is to reduce timing to a very safe level. If optimum for our cars at boost is 22-24 degrees BTDC, then back it off to 16 -17 and keep it there until you have the fueling and the alky injection settings figured out. Then you can start bringing the timing back in little by little to your target MBT. Leave the timing for last.

After you've retarded the timing to a safe level, start looking at the a/f ratio. Expect to use an a/f ratio no leaner than 11.7:1. Depending on your engine, you may need to go as rich as high 9s, low 10s to one to eliminate knock, particularly if the aux alky injection isn't properly setup yet. It would be best, if you notice the a/f ratio is on the lean side, throw 10% more fuel at it at a time until the a/f ratio is safely on the rich side. That should be high 9s to one. Then start leaning 2 percent at a time until you start seeing knock on the meter. At that point, if you're still on the rich side (richer than 10.5:1) you will need to start working on the alky system to inject more alky.
Add alky until the engine starts to miss and then back off the level until the engine cleans up.
If the mixture is still on the rich side, start taking away fuel 2% at a time and see how close to the high 10s to one you can get without knock. If you start getting knock before that point, go back to the alky system to see if you can now add more alky without running into engine miss. As you close in on your target a/f ratio, make 1% changes to the fuel.
After the fueling has been done, now go back to the timing and add 2 degrees at a time, checking for knock each time. If the first 2 degrees of added timing causes knock, go back to the fueling and change your target a/f ratio or try adding more alky to the mix. If more alky just causes engine miss, you'll have to change your target a/f ratio to a richer number. After doing that you can go back to the timing and keep trying to bring it up to your target MBT. There will be a point in this back and forth between fueling and timing where power starts to drop off below exceptable. If you can only get away with 20 degrees, then that's it.
 
If you find that the power level is not much different between 20 degrees of timing and 22 degrees of timing and you have no knock at both settings, always choose the lower timing level. That will create a safety cushion for the engine. That will be your MBT. Minimum Best Timing setting.
 
Be careful with chips that richen only at WOT, AND above a certain boost level. There will undoubtedly be a transition point in the rpm and boost rise where the a/f mixture may be too lean and you will have the onset of knock before the WOT richening has had a chance to kick in. Hopefully more alky during that transition point will take care of that knock. Or maybe the chip could be sent back to richen the target a/f ratio at that particular engine operating point.
 
Those that have EGT meters should be studying the egt during all these changes to see what egt gives no knock compared to egts that do create knock. I'm in the middle of tuning a car now that will knock at 1520 F and will not knock at 1480 F. Just interesting information that might be useful as changes to the tuneup move forward.
 
Very important tip. Always tune rich to lean on a safe timing setting. Especially where alky injection is being used.
Never tune lean to rich with a lot of alky injection in the picture.

Again, ALWAYS TUNE RICH TO LEAN!

If you run out of range with your chip and can't get to a safe rich setting, send the chip back to have the range adjusted before you continue with your tuning.
 
As you start working up to your target a/f ratio, it would be a good idea to start checking the plugs. Start getting used to how the plug signs are changing as you move up on the tuneup.
 
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