transitional knock with alky

[Pablo]

Ive got the chip dialed in decently, about 22 deg of timing with about 26 lbs of boost. It runs great except from highway speed or anything near that if I just gun it. It will kick down and i will get instant knock.

Clearly, the alky is not reacting fast enough to the sudden jump in boost.

I thought of several ways of correcting this, but none of them are easy. Maybe a code patch that retards the timing relative to speed and change in throttle position that decays out, kinda like a pump shot

or maybe some sort of trigger for the alky using the same criteria

Any ideas?

ive adjusted the turn on point and initial to start very early (like 0 psi) and come on strong right off the bat but its still too slow to react

btw ive got it hovering around 11.5:1 afr on the wide band, and egts are extremely low (seems odd, but its been that way since i switched to methanol, even when I started tuning and it was way on the lean side due to the much richer stoich methanol has over isopropyl)

 

[turbot2496]

Well if you want to keep it simple and easy just install a button that starts the pump going and push it about a sec before you get on it. Works for me... what kit are you running? Sounds like Razors from the description but I thought he had that problem solved with his kit

 

[Pablo]

yes, but i dont want to hit a button every time I go WOT from a high speed roll. I find that to be incredibly annoying, I might as well run nitrous. You are also taking out the concept of progression when you use the button. My AFR will drop down super rich (as noted on a wide band) when I press the button

Despite being progressive its still never going to be as fast as injectors reacting to the difference in load. From a 65 mph roll if i gun it I go from vacuum, low rpm, to full boost, high rpm instantly. Does not seem to me like a pump can react fast enough.


I wish e85 were available here and I could just set the car up with that and forget it

 

[Pablo]

gotta love the archives


did some searching and found that burst knock retard is exactly what I was thinking of (and i thought that up all by myself, I should get a medal) im gonna play with that now

 

[turbot2496]

It runs great except from highway speed or anything near that if I just gun it. It will kick down and i will get instant knock.

Clearly, the alky is not reacting fast enough to the sudden jump in boost.

Are the lines primed when your doing your test? I have no experience with Razors kit but I thought preventing what your talking about was one of the main reasons to get this kit. Maybe you need to give him a call.

yes, but i dont want to hit a button every time I go WOT from a high speed roll. I find that to be incredibly annoying,

Agreed

You are also taking out the concept of progression when you use the button. My AFR will drop down super rich (as noted on a wide band) when I press the button

I see your point but if your cars like mine... when you floor it at highway speeds the boost comes on immediatly and up to your set point pretty fast. If the pump reacts slow and is behind then I don't believe you have a good progressive effect anyway. Perhaps something that comes off the tps sensor that when it hits 4v or so it sends a low voltage to the pump to get it going sooner ....

I would think the burst KR ideal is gonna make the car a dog off the throttle but I'm interested to see your results. Good Luck and I hope it works.

 

[Hammer231]

Yeah, I've been living with this same problem for 6 or more years with or without alchy. I've tried tuning it out but nothing so far has worked for me. It's so friggin' annoying. I've also got Razor's kit and have been blown away by how scary fast this thing is now even with an original high-mileage motor still purrring under the hood. Unfortunately, the knock still spikes up when I quickly go WOT then settles back to 0. The alchy seems to be doing it's job but the fuel delivery even with a hotwired XP pump and MSD 50s is not getting it done when the boost jumps quickly.
It's amazing how some cars struggle with this issue and some never have a problem.

 

[bruce]

Be sure that the line runs steadily downward to the pump, and then runs upward leaving it. You don't want to have any *bubbles* accumulate in the lines/ filter. Depending on how hot your engine compartment is, you can about boil the alky in the down line, if it's too close to the turbo. Close being a relative thing, depending on your normal underhood temps.. Post pump, heat really isn't much of an issue, since it's under so much pressure.

Given any air pre pump (speaking in generalities), once a pump has any cavitiation, it can take a while to purge the air out.

 

[bruce]

Yeah, I've been living with this same problem for 6 or more years with or without alchy.

Might look at the BKR settings, the lines, and the Accleration Enrichment settings, or injector size that your running.