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Transitional knock

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VIN7

Member
Joined
May 24, 2001
Messages
595
Transitional knock in this instance: When you first go WOT some detonation occurs but ramps down to zero once the alky starts flowing.

Does anyone experience transitional knock using 93 octane and alky? I have a JC kit and I am putting in a prime button to try and eliminate the knock. Those with the SMC kit...if you are getting transitonal knock, would hitting the test button to prime the system help any? How about those with the MaxEffort style recirc. alky systems...any transitional knock with those type?

Thanks,
Mike
 
Transitional knock is something that no one seem to have come up with a sure fire answer yet, and this has been worked on by many people, for many years.

Personally mine went away when I switched to de-natured, and ac-43 plugs, gapped at .032. (I was running '45s previously, with isoprophol) There is a trade off, as the de-natured does not cool as well.

My theory on what causes this knock deals with hot spots, and spark, and equal air distribution.

Theory 1.-Hot spots: They develop in, and around the middle cylinders (2&3). Could be the plug electrode, as well as valves. When the alchy hits them, it steams, and shorts the plug electrode out. when the electrode finially fires, (after the seteaming action stops) it does so with a richer charge in the chamber, producing knock.

Theory 2- Steam, and steam vapor. Actually the same thing as far as semantics go, but a fully dispersed alchy charge, from hitting too much heat at once, may cause transitional knock by releasing its energy early in the compression stroke. Same as gas, and pre-ignition. The steam vapos acts like a spring, sort of, pushing back on the piston as it rises to it's full height.

Theory 3- Air distribution. There is no way I can think of to get more of the alchy charge to the 2-3 cylinders to cool them more than the others. If this were possible, then the hot spot problem wouldn't exist. Instead we spray the alchy in, giving the 'cooler' cylinders a bit too much alchy, and the hot ones not enough. As you get into the run, the temperature difference between the 'hot' and 'cool' cylinders get even greater, I suspect. As a partial remedy to this, I installed a hemco plenum, in the hopes that the more even air flow (air that is carrying alchy) would help address the difference in cylinder temperatures.

Theory 4- Unless your car is running right, good spark, good fuel, etc., you should not be spraying. Bad pcv's, bad turbo seals, that are letting hot oil in will cause knock, as well as fuel pumps that can't keep up, and ignition systems, and plug wires that fail under load. Any of these things could be causing knock that could be mistaken as 'transitional' knock.

I honestly don't know if the Hemco helped, because I didn't have a scanmaster right after it's install, and when the alchy system on my car went down, I got the scanmaster, and changed plugs, changed gaps, and switched to the de-natured, all at once.

http://www.loveridgemachine.com/RJC_Buick_Products/rjc_buick_products.html

Here is a link to a company that makes a plenum spacer that evens out the airflow. It costs much less than a Hemco, and according to them, works a bit better. I would buy it. The Hemco reduced my boost pressure by 2 psi, and I was able to turn up the wick to the previous levels, without knock. The entire jury is still out, but I believe that the product works.

BTW my signature shows alum. heads, but I will not be running them until next week. I was using stock, cast heads when I made the changes stated above.

I'm hoping the alum. heads will help with shrouding the plug, and keeping the spark from going out, as well as keeping the hot spots down a little bit. I'll still be spraying, and I'll let you all know how this works out with pump gas.
 
Turbo_Tim, I've been all around on this issue for years and share many of your theories and ideas. The main problem I have is in replicating this phenomenon with any repeatability.
The only hints I can offer is that lower initial timing and/or a bit more fuel _seems_ (theres that confidence again) to help. But now you have to juggle fueling, boost and w-a ratios to keep the egts up. Arrgh!
For now I just accept the fact I'll usually get a few degrees of knock spike upon initial transition from low to high airflow.
You could always set the software to ignor this but that is a risk factor I don't think is worth taking.
After about a few years of beating this to death I've about given up. As long as the rest of the run is knock free then the couple degrees of knock spike I may get is no longer an issue with me.
 
To answer the question about regulated systems and transient knock, YES.

The problem seems to be with the alky not getting to the nozzles quick enough, maybe this is caused by the solenoids having trouble opening against boost, I don't know for sure.

I'm tinking around with a couple of ideas for controllers to open solenoids using other inputs, maybe it'll work, maybe not, I'll have to wait til spring to find out. :mad:

The problem with high boost systems (25PSI +) is that the knock will run away and not taper back off, so this can be very dangerous on the street. And it's way worse to blow a head gasket on the street than it is at the track. ;)

I'll let everyone know if my controls work, I'll probably start selling them in an effort to pay for college. (if they work that is)


Steve Hill - one more question, do you sell Flojet Pumps, when I called them they said that you were a contact for the alky injection pumps. If yes what is the price? I'm not about to pay Carrols $300 for one. Thanks
 
prsrizd_v6.... my system has the w-a already flowing from two of the four nozzles when going wot. This means the pump and lines are under full pressure, and this tends to discount the "not-in-time" theory.

If you are suffering 'runaway' knock you may be experiencing performance issues. I never run lesss than 25 lbs, usually 26.5, and see no knock at all (after the transitional thing) even into fourth where I recently ran up to 129 mph.
I'd suggest you review your current setup and system needs.

Regards the pumps that is something Flojet sales set up when I was doing field testing for them. I will check on it this week. I agree that Carrolls pricing for their pump (an excellent unit, btw) is waaay out of the ball park. I have discussed this with the owner via emal and his response was less than generous :-(
 
When do your first 2 nozzles turn on? With 1psi? Or via TPS signal? Or are the always flowing? I'm a little confused. Then your second 2 come on at WOT correct? via a TPS voltage trigger?

I doubt that there are performance issues with the system because it doesn't occur when at the track leaving with light boost. It only happens when you are cruising and go WOT from there. That's why I'm led to believe the 'not in time' idea. Different Jets have been used also. And there's lotsa Nozzles pumping Methanol/Water (50/50).

The system I'm dealing with isn't mine but it's a very very proven system. That works excellent at the track, it's just that it has trouble when downshifting from cruising speeds and then spooling up. I think my plan for a differential, TPS triggered, controller will work.
 
I'll bet this has been tried, but...:)

Since I had 0 transitional knock (ran to 25psi), using de-natured only, why not have a seperate, 2 stage system that could kick in at, say 20 psi, and add a small amount of water to the spray?

Yeah I know 2 tanks, 2 pumps, etc.

But the denaturred worked great for me, it just wouldn't cool enough.

I believe that the denatured caused no knock, because I could turn it on early, before temps got too high.

Introducing different mixes, at different heat levels......

Thoughts? Experiences?
 
Got 2 nozzles at 4 psi and 2 at 15, 1 with KR. Currently running 50% water methanol. It helped a lot, don't get me wrong :D

Thanks
 
Turbo_Tim:
I think it has been found that the water component is more effective at detonation suppression? Some of the technical details were worked out a half century ago by people smarter than I.
Actually, I have used pure denatured at one time or another. I really didn't see much going on other than being pretty rich; I'd probably needed to remove another ~15% fuel from the ~15% I already do now.
But you have reminded me that this is something I need to revisit one of these days.

PRSRIZD_V6:
i use 75% tps for instant wot triggering, and a hobbs set at 12 or 14lbs (can't remember...defective brain cells) to trigger rest of system. I have tried most other combinations thereof yet seem to keep coming back to this. What can i tell ya :-)

As for your thoughts on "not-in-time" and "not with light boost", et al, well I hear ya loud and clear. Believe me, I've been around the block more than a couple times on this.
But it's not simple, there is much more going on than we, or at least, I tend to focus on.

As I mentioned earlier, so far the only way that I, personally, have been able to improve this so-called transitional knock thingy is to reduce timing and/or richen the gas (not the alcohol).
If you hit upon anything else please let me know asap!! :-)
I do have new chip software to try, courtesy of Steve Yaklin, which will vary timing as a function of spool-up. Steve is waiting for me to get off my butt...I was supposed to do it today but it's raining. Guess that's better than snow........
 
I've been kicking that idea around, just haven't tried it. I plan to try that or a processor that will look for a rate of change in TPS to trigger the first solenoid(s). gonna take some planning. I'll have to wait til spring, my cars already long gone for the winter. And I need a New Pump. FloJet time.

Thanks for the help Steve, I'll keep you posted if I find anything of interest. Or you'll hear it through the grapevine, either way it'll get to you pretty quick.;)

:cool:
 
Years ago I learned that using a regulated system and lower timing was the best answer so far on the transient knock problem.
Unfortunatly I have 1000 bucks in a regulated system with all methanol compatable pumps, solenoids, regulator and teflon lines.
Joe Tripodi makes a kit similar to what I run but nobody wants to pay for it. He doesnt make hardly any money on it.....its just that all those parts are expensive as all get out.
Nobody would consider using a deadhead gasoline fuel system so it stands to reason I wouldnt consider a deadhead alcohol system when you run more water/methanol than you do gas, like I do. Timing is 18 degrees at 4000 20 degrees at 4400 and 22 degrees at 4800 on up.
I bring my noz's on at 8psi and have very little trouble with transitional knock, but, I cant part throttle the car either....its normal driving or WOT, nothing inbetween.
The nozzles are close to the regulator which is set at 40psi and goes up with boost. I suspect it is harder for the NOS solenoids to open under higher pressures but am not sure.
Also cars with camshafts for higher rpm's seem to get away with murder cuz they make less cyl pressure at the lower rpm's where the transient knock seems to occure.
I run stock cam.
The car runs mid to hi 11's all day with a trunk load of tires , tools and on drag radials on pump gas. I dont leave with any boost, just mat it like leaving a stop sign and gets 1.7 60 ft all day with no suspension work except for a flat air bag I forgot about.
To do it right you gotta spend the bucks on the correct parts or turn the boost and timing down.......or put a differant cam in maybe.
Just my expiriences.....
Steve
 
Interesting this topic came up, I just got my alcohol kit and have been experiencing a little transition knock, Yet mine is under 5 percent, and disappears in the second or third frame on the scanmaster at WOT. I know any knock sucks, but is such low numbers something to be concerned about?? Im running 21-22 psi on 93 + alky(str8 denatured with a small squirt of wd-40 for lubricate).

Shoebox
 
Would a nitrous plate work to reduce transitional knock?? I know it would be a little more expense, but would it be worth the $$$??
 
I dunno if the alky would have enough time to evaporate if it were sprayed inside the intake. I know that's how the Jay Carter kit works... does anybody have experience with that kit?
 
Steve Y....so are you saying that guys with the bigger cams can get away with transient knock? how big a cam? i run a weber 206/206 roller. i got a bud here that runs a 206 flat tappet and he has no transient knock.
 
No, he said engines with larger cams have lower cylinder pressures at lower rpm and, therefore, may not suffer from transitional knock as much.
 
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