High RPM to reduce knocking

I have noticed that even with high compression ratios engines like the LS1 and LS7 can be fitted with superchargers as long as they do not make alot of boost at low RPMs, my question is if they can use 8psi at 3000RPM without knocking how much boost could they use at 5-6k RPM. Would a boost controler that allows more boost at higher RPMs be a good Idea or is it just too dangerous, and how much more boost could they take?

uhhh the higher the RPMS the more likely the chance of detonation. Im not sure where your getting your information from, but id look elsewhere.

Knock is usually caused because there is to much pressure and heat inside the cylinder, the gas and air explode before the spark. With any engine, the higher the RPMS, the more volatile the gas/air mixture is going to be. Theres going to be more and more gas, creating more heat and more power. With a supercharger that just adds even more heat and air, which means more fuel.

So your not making any sense and your looking at knock or detonation all wrong.

If you have an engine setup that knocks with 8 PSI at 3,000 RPMS you have a very very poorly setup engine. You need to do some major tuning to fix that.

uhhh the higher the RPMS the more likely the chance of detonation. Im not sure where your getting your information from, but id look elsewhere.

Knock is usually caused because there is to much pressure and heat inside the cylinder, the gas and air explode before the spark. With any engine, the higher the RPMS, the more volatile the gas/air mixture is going to be. Theres going to be more and more gas, creating more heat and more power. With a supercharger that just adds even more heat and air, which means more fuel.

So your not making any sense and your looking at knock or detonation all wrong.

If you have an engine setup that knocks with 8 PSI at 3,000 RPMS you have a very very poorly setup engine. You need to do some major tuning to fix that.


WTF are you talking about here is an intresting tid-bit of info for you


7.7 What is the effect of engine speed?.

Faster engine speed means there is less time for the pre-flame reactions
in the end gases to occur, thus reducing the tendency to knock. On engines
with management systems, the ignition timing may be advanced with engine
speed and load, to obtain optimum efficiency at incipient knock. In such
cases, both high and low engines speeds may be critical.


that is from http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html BTW I did not asy that I have an engine that knocks, nor did the engine that I mention knock what are you talking about? Where do you get your info from? Did you actualy read the post? Try it some time reserch the facts and then anwser. OK

at higher rpm's the pistons are traveling faster, this sucks in air at a faster rate, when the piston hits the bottom, the air has momentum and keeps moving and gets compressed a bit, this is because the valve doesn't close right when it hits the bottom. at higher rpms, more air gets stuffed into the cylender so there's more cylender pressure and thus more tendency to knock.

this is why tuning and higher octane fuels were developed....

the reason it would knock is because the charge of air is soo hot when it enters the cylinder that it ignites before the spark plug ignites it. That is why intercoolers and high octane fuels were developed......

You need to read into it a bit more.....

So are you trying to tell me that the tech article is wrong? Could you show me some kind of reliable source that shows me that this is not the case? I thought that less time to pre-detonate ment less chance of detonation? Could someone prove this wrong please? Did anyone actualy read the artical that I posted if so how is it wrong?

I'm just repeating what i heard, and it seems to make sense to me. i think that the extra air that gets injested into the engine outweighs the shorter ammount of time to react.

the detonation im familiar w/ is forced induction....the turbo becomes inefficient or the IC doesn't cool as well as it should and the intake charge is too hot.....detonation.......

uhh i can tell you right now, that tech article is so far off it looks like a 10 year old.

Compression Octane Number Brake Thermal Efficiency
Ratio Requirement ( Full Throttle )
5:1 72 -
6:1 81 25 %
7:1 87 28 %
8:1 92 30 %
9:1 96 32 %
10:1 100 33 %
11:1 104 34 %
12:1 108 35 %


oh yeah that chart is right, according to this chart, pretty much every car on the road should be running 96-100 octane in there car. . .

listen the faster an engine is going the higher the chance of a knock, that article is all wrong.

Here is this article wrong too?

When you add too much timing, you'll hear a sharper "crack" for each firing. When you tip into the throttle, it will try to respond quickly but misfire because the VE of the motor cannot keep up with the spark, in layman's terms. You want timing to slowly ramp up until the engine "clears its throat". There, you want to carry maximum timing until your start building significant boost, where you'
ll be forced to start backing off timing. Where you get maximum boost and torque lowest in the RPM band, you'll want to be most conservative with timing. As torque starts to drop off and cylinder pressures die down due to pumping losses at high RPM (read: restriction), you can usually add more timing. If you have you're a/f set pretty conservative and you are getting high EGT's, your first step will be to drop the boost until EGT's come down to a reasonably level. Now, at that same boost level, advance the timing while watching knock carefully, and ensure that you have not altered the a/f ratio by changing the boost. Watch carefully; if there is a reduction in EGT temps by adding timing, then you had taken out too much timing. http://www.turbosaturns.net/articles/tuning%20your%20turbo%20saturn_2.htm

Gee you can advence your timing at higher RPMs under boost why is that because you have less tendency to knock....wow but I guess they must be wrong too let me go to the SAE website and see if they have their facts screwd up as well.

do you have a link to this article, it's good to have links so we know you aren't pulling falsities out of your ass and calling them facts.

do you have a link to this article, it's good to have links so we know you aren't pulling falsities out of your ass and calling them facts.

Uh yea the link is on there

oops, i didn't see that, sorry.

uhh i can tell you right now, that tech article is so far off it looks like a 10 year old.

Compression Octane Number Brake Thermal Efficiency
Ratio Requirement ( Full Throttle )
5:1 72 -
6:1 81 25 %
7:1 87 28 %
8:1 92 30 %
9:1 96 32 %
10:1 100 33 %
11:1 104 34 %
12:1 108 35 %


oh yeah that chart is right, according to this chart, pretty much every car on the road should be running 96-100 octane in there car. . .

listen the faster an engine is going the higher the chance of a knock, that article is all wrong.

Granted there has been alot of advencments in engine cooling and head design, but the hard facts remain, granted if you are runing alot of boost with no intercooler you will have problems with knocking as you turbo forces hoter and hoter air into your engine, but with proper cooling that should not be a problem. Could you show me any evedence that higher RPMs with the same intake temp increase knocking, and I am not talking about one guy that did not have his fuel map setup properly I am talking about hard facts here.

oops, i didn't see that, sorry.

Not a prob, just read the whole post before you jump to conclusions about what I am saying :-)

i did, i just kinda jumped that one line lol.