What boost level shouod alky kick in.

[V8killR4U]

I know the answer kinda. (whenever you see knock) but
what type of boost levels do you guys see before the alky comes on. Are there any ill effects if it comes on at lower boost levels like 11-12 lbs. What type of boost level should i see before i get knock?

 

[lrover2]

You should not see knock under normal good conditions (Gas, Temp etc..) at any thing under 15 lbs. When I used alky I started spraying at 13lbs but it all depends on how fast you spool up too.
That’s probably a good starting point. If you’re not getting knock keep turning it up until you do get knock and then back it down a bit. Alky won’t stop transitional knock so you need to be able to define what is what. The effects to spraying too early would be poor performance (bogging). In fact hit your test button at idle. This is an extreme example of spraying too early. It wont hurt it but it will not like it.

 

[Bens87tr]

My car likes it to come on late, higher than 15 pounds. In fact, if I keep it at that boost level (part throttle) the car does that death pop i.e. the super loud bang. Too much too soon with the SMC dual nozzle. I'll be looking into Razor's progressive kit soon.

 

[Razor]

Your answer is depends.

There are somethings you juggle. One is how much alcohol you need to make the most power at the final boost you run. There is a big difference between the requirement of most cars at 20 vs 25 or even 30. Once you figure that your car needs "X" amount of alky at lets say 25 PSI, now comes the difficulty. I'll explain in simple terms.

When you mash the pedal and the boost shoots upwards, eventually you will get to a point whereas the motor will knock. Lets say 16 PSI for arguement purposes. Now telling your kit to spray at 16 PSI presents a problem. One is the time it takes to get the pump to spin and make pressure, fill lines, spray out the nozzle, go past the throttle body, past the intake valve and quench the octane thirst. This time is the reason most set thier kits to 10-12 PSI for turnon. The faster the spool, the longer the lines, the lower the turnon. If you set it to lets say 16 PSI, then by the time the process fully happens of the needle on the boost guage climbing.. the car sees knock retard until the cylinders get quenched...16 you tell it to spray as the boost is rising torwards 25.. if your system is really fast..maybe by 18-19 you can catch it. Problem is past 16 you see knock. I hope so far so good have'nt lost ya.

So you tell it to spray "x" amount of alky at 12 PSI, so you can head off the knock that will happen after 16. This is how its been done. Now comes the drivability problem... you go and pass someone on the highway at part throttle, the boost climbs to 12 PSI and the kit fires "X" alky into the motor, next thing the motor feels like its stumbling,surging, and black smoke out the tail pipes from being overly rich. So the fix is reduce alky amount, but then you dont have the alky needed to sustain the 25 PSI knock free you normally run.

If the car spools slow, and has a lot of aftermarket parts to make the airflow more efficient like bigger IC, Turbo, heads, cam, etc.. then higher turnon points with less alky demand at 25 PSI make a great compromise. If not, then its time to work on the system.

Knock if it comes from not enough octane is one thing.. a bad thing. Knock that comes from exhuast/mechanical issues is another. Careful not confuse one with the other.

Whats the fix, a multistage or progressive system. To get the pump early on going to head off the 16+ PSI knock.

Mine turns on a 3 PSI FWIW. Hope this post makes you think.