Transitional knock is driving me insane.

[Pablo]

I have brought down the timing from 25 to 22 degrees and I have increased the BKR (burst knock)to .8 seconds and 17 degrees of retard. I made some headway by bringing the main timing back and the bkr to .5 , i can actually floor it now and not get knock a good portion of the time.

but surprise surprise i STILL get transitional knock a good portion of the time, and its not pretty, 6 degrees of retard today on a kick down from like 35, and like 4 degrees kicking down from 2nd to first punching it from a slow roll.

This is the most annoying thing on earth. Its the singular issue that makes driving my car feel like I am playing russian roullette.

Ive allready got WAY more BKR retard than the factory code, and rather conservative main table timing for alky. Im sure if i retard the main table more I would get rid of it but it seems pointless apply a long term fix to a temporary problem at WOT. It does not knock even with 25 degrees of timing after the initial hit. Wide band O2 shows good transitional AFR too.

This is with alky injection btw and its clear that its not reacting in time, it cant, since it relies on boost and once thats there, the stage for transitional knock is allready set.

Since a good number of you seem to have no problem with transitional knock, I would like to know what you did to eliminate it.

This car is mostly driven hard on the street, from a roll or a stop... so maybe this is why I see this problem alot more often than alot of other people.

I dont know what to do chip wise next. I was planning on adding a WOT microswitch to activate my "test" button since pressing the test button while going WOT eliminates the problem.

any ideas for the chip instead?

 

[Steve Y]

Alcohol needs heat energy to vaporize, thus causing it to pull heat out of the chamber.
In the first little bit after you nail it, I suspect the alcohol may be in bigger droplets which tend to exit the chamber without doing what it is supposed to do. Non intercooled cars seem to work better with alcohol injection because they heat up faster.
After the cylinder heats up things tend to work according to plan.
I see many cars with cams that make less cylinder pressure at a lower rpm do rather well in the transitional knock dept.
I run a stock cam (more cyl pressure at a lower rpm) and a TA63 turbo and expirience the same symptoms you do at times.
I have often thought of running the alcohol through a copper line along the bottom of the upper radiator hose to induce some heat into it thus possibly compensating for the lack of heat energy in the first second or 2 after you nail it.
After the alcohol gets going it will start to cool down as it passes through the line at a higher rate of speed.
I use radial tires and it helps my application to bring the boost up slower and reduce the initial spark.
I come off the line with 16 degrees then kick it up to 18 or, at times 20 after it gets going.
Doing this without heating the alcohol seems to have eliminated most, but not all of the transitional knock. I would say I get a ping 1 time out of 3 launches now.

Going from a roll is more of a problem if the rpms fly up fast.

Steve

 

[WSLN 6]

Just goes to show every car is a little different. I am running 26 degrees in first with a 17psi turn on point, and never get transitional knock. Weirdness.
Are you sure it is real? Have you tried adding octane to see if the knock goes away?
Maybe the downpipe is hitting the frame or a bad tranny mount...

 

[Pablo]

Im positive its real, I can hear it, How much boost and what type of gas are you running wsln? 91 octane is the highest available here.

SteveY,
Its pretty good now in that from a launch, 9 times out of 10 it wont do it. But like I said, I like to be able to get on it at any time.

Im pretty sure alcohol is going to vaporize atleast by the chamber no matter what, the temps in there are insanely high. The pump itself cannot react fast enough, the pump can only react to what its being told to do, since the alky system relies on map, it can only know of boost after it has allready occurred, add in the extra amount of time for the pump to overcome its internal friction and inertia, and get that column of alky moving it will be too late.
If there was a system that was allways pressurized and had an actual injector in the up pipe with an ecm driving the pw's using tps and map I think these transitional problems would be eliminated.

 

[Eric Stage I]

Are you sure BKR is coming on? Do you have Directscan?


Eric

 

[Pablo]

No, I'm not sure.. I wouldnt be surprised if it wasn't as it doesnt feel like I would imagine it would feel like with the amount of retard I have programmed in.
Yes i have direct scan, I read that BKR would not be displayed in direct scan, is this true?

Since I read that I didnt really bother looking for it, and I dont recall seeing it in my logs. I will check for it when I get home.

Would there be any reason for it not to come on?

 

[suicide six]

May be converter causing your woes,Some have experienced transition knock due to converter lock.From a dead start w/ brake applied before hand, change your readings?

 

[suicide six]

Get yourself an alky chip,Try adjusting base readings to translator if using this setup.does lowering alky start point from say 10 to a lower number help?Xylene to fuel tank may help transitional knock but is only a bandaid and may waste your O2 sensor if too much is used. What are your BLM numbers?

 

[WSLN 6]

I have been using 92-94 octane depending. I would get transitional kncok when I would lock the converter, but only then. I switched over to straight methanol with lube, and the knock magically dissapeared....

 

[suicide six]

If you have a chip burned for EGR function and Egr is plated you will also get the knock.Look for the obvious areas of something hitting,DP,mounts,trans mount etc. Some chips are burned with a delay in them I believe to hide knock reading.but this only erases a known problem.

 

[suicide six]

Try retorquing knock sensor or try a spare.

 

[Pablo]

I am doing my own chips, I have a pretty good grasp on chip tuning and I have a wideband. I am running an open loop with no narrow band sensor

I have no egr, i have made adjustments in my main table because of it, i have no more than 36 degrees anywhere the car runs in and timing drops off quickly as LV8 increases.

my low rpm timing advance table is at 18 and my main table is at 22, burst knock retard is at 17 degrees for .8 seconds

Transitional AFRs are good, from mid tens to mid 11s

This is definitely not false knock, I can hear it knocking with my ears, and i dont mean an alarm, i hear the actual knock

I have played with the alky kit settings, doesnt really make a difference because the knock is from instantaneous increases in boost and its just the nature of an electric motor that its not going to respond that quickly


I really would like a way to verify that BKR was functional because I really cant tell if it is or not. I dont feel a bit of difference in changing it even from .3 to .8 in duration

 

[ijames]

Easiest way to verify bkr is to go old school . Put a timing light on it and you can see the bkr when you snap the throttle open from an idle in park. Make the time as long as possible , and if you want to make it really obvious set every entry in the main and wot tables to something like 20 deg.

 

[Eric Stage I]

Make a DS.INI file using notepad.

Put in the file:

CB 1 D

Save the file in the same directory as DS.

Run DS by using the DS -U option. You will notice memory position CB is now displayed.

"CB" is the location of the BKR timer. It will always be at zero unless BKR has been activated. It will display the raw decimal value, not actual seconds, but you get the idea.


Eric

 

[Pablo]

You freaking rock.


I'll let you know how that goes.

So the ini file only needs that in it? nothing more?

I will have to look in the manual to see about DS -u option, im not familiar with it

 

[Pablo]

ok

it worked

im getting BKR, but not always, looking at my logs, it looks like I am only getting it if I punch off idle tps voltage.

I am going to play with the % delta tps to enable and lower it a good bit

I have also found that even .8 is not nearly enough time to cover when the car knocks, it takes longer than that to fully spool up judging by the maf numbers, like probably around 2.5 seconds (i know, a smaller turbo would be better for my combo)

unfortunately I believe I attempted to save too many runs to my floppy and it erased the first two saves which actually did have knock.

What I am noticing is that with the car cold and no wot operation, it is much more likely to knock on the transition, and knock heavily
After I got on it a few times the knock basically vanished.

Maybe there is something to what SteveY was saying

I also tested things by getting on it while holding the test button and it ran like a champion when I did that.

A funny thing is that I think I just may be better at hearing knock than the KS, as it started to go away the knock retard on my scanmaster vanished and nothing was recorded on direct scan but I could still hear it knock very lightly once or so as it transitioned. Hooker exhaust is pretty quiet when you get on it, weird huh?

So as it stands now, Im thinking about making my next chip with around 8 degrees of bkr retard for 2.5 seconds and reducing the delta tps to oh.. lets go with 4 from 7

does that sound completely outrageous?
Im also going to try the wot microswitch idea too, i have one on the way, just have to figure out how to mount it.

 

[Pablo]

I think ive gotten a handle on transitional knock

I would say the bulk of the problem is too much timing in the main table not ramping down fast enough. I removed a ton of timing while still maintaining my same 22 degrees at 255.

I also switched from isopropyl and experimenting with different percentages of water to just pure methanol.

Ive now determined that methanol is definately superior for our application.

The burst knock retard doesnt really work that well, it seems like the only time it will kick in is when you jump on it from 0 throttle even though ive reduced the TPS enable % difference to 4%

Something is up there because its definately moving more than 4%, and also, there is no time stated anywhere that I have seen, 4% in what amount of time?

One side benefit is that launching on the street with a long bkr setting (i have it at 2.5 seconds and 7 degrees of retard) really does a number on preventing wheel spin. The car just goes and when the 2.5 seconds is up you can feel it really just take off like a bat outta hell.

Theres no way for me to tell, but I think that the MAF is lagging behind in what the engine is actually doing. Since I am not logging boost I cant really tell other than when I initially get on it it is a little leaner than what Id like (I thought I was good but further analysis shows im not)

Id like to move the maf after the turbo somewhere but I dont want the alky to ruin it so im going to have to research that a little further.