well ive been running the 2.8 pulley for a a few weeks....i have 1 step colder plugs gapped to 0.30...cai....and cat back exhaust....i know i need fuel that is not a ? BUT so i ordered the 3.0 pulley till i want to spend the $450 on injectors and maf trans....well i was getting 5.8 degrees of knock retard with the 2.8 pulley and i swapped to the 3.0 pulley and left the 1 step colder plugs in and im STILL getting knock....2nd gear at about 4500 rpms i got about 4.5 degrees of knock...damn this....i only have ever run 93 oct gas so im not running crappy gas....so are you guys running the 3.0 pulley get knock too? or not...i have no choice to just buy the injectors and maf tran next week because if im getting knock with the 3.0 i might as well put the 2.8 back on...so ill run the 3.0 till next week when i call rob and order the inj and maf....so shoot me any info you guys might have on what could be wrong....its a 06 by the way too...also have any of you guys used a auto meter a/f gauge?i have one just sitting here and not sure if it will work....like on the srt-4s you have to run a wideband a/f just a regular a/f wont work...so if it will ill put it on this week and see how lean i am....thanks ahead of time for the info

 

What are you running for fuel?

 

I had no KR with the 3.0 but i was real lean above 5K. It is cold here so that helps the heatexchanger to work better. You need bigger injectors period plus better octane/fuel.

I run 93 here i Indy.

 

well i run 93 oct...and it was 50 degrees out today when i was testing...i only got knock that bad 1 time the most i got most of the time was 1.5 degrees or i think 2.3 degrees all the rest ofd the time...could i have the wrong plugs in??? i have bkr7e ngk plugs gapped to 0.30...mabye that is it???did you have stock plugs in with the 3.0 pulley???

 

I run autolites gapped at .045. Try changing your plug gap, check your coolant flow in the IC, also check for trash in between condensor and heat exchanger.

 

Why don't you try some 2 steps colder plugs, since 15-18 PSI of boost is high ! ZZPerformance suggest them for the 2.8" or smaller pulley.

http://www.zzperformance.com/cobalt_...ts1.php?id=490

I will myself try some 3 steps colder plugs (Denso Iridium Power #IK27 Plugs) with the 2.6" pulley, since each heat range removes roughly 70 to 100 farenheit degrees in the combustion chamber.

Knock occurs when the air fuel mixture gets too hot and ignite before the plug fire !

Someone runs NGK Iridium BKR9EIX (3 steps colder plugs) with a twincharged setup and they run fine with merely no knock at all.

 

Knock is not only a fuel type consideration.

Intake Temp
Compression Ratio
Boost Pressure
Stoych

These are all things along with some other that you have to address. Knock is definately and Piston Ring and Rod killer. Good luck with that...

 

i havent done my 3.0 pully swap yet, but with the fujita, we ran the tec 2 at the garage and i have no knock, and a 14.7-1 a/f ratio..... i dont know if that is high or not, what is everyone else getting?
I have run 93 octane since i got the car as well

 

IMO 14.7 is not dangerous but I personally like to see it below 14.5 rather than above it..

It will make better power there but is a bit more dangerous...

How did it compare to other runs...

 

I have a feeling i've ben getting knock on my car. and when i pulled my plugs yesterday to put in the range colder plug my stockers looked like one more wot pull and they would have granaded. They were more black than brown. I orderd a 3.0 pully ut just for the reason that i get 16-18 psi im figuring they sent me 2.8. So 93 octane wasn't cutting it so i started running 94 which helps alot.

 

14.7 is stoych and what you want at idle/cruise. At WOT intercooled you want to be around 11.0-12.0:1. Also the Tech II will only show you COMMANDED A/F not your ACTUAL A/F (you will need a wideband for that).

 

^^^ what he said is correct for the tech 2


i see knock with my cav all the time , only time i really dont see any is at the track when im using 101 octane , plus alky injection


seeing some knock retard is normal , and lets you know the pcm is doing its job properly

if you dont notice a lag in power then everything should be ok , and not hurting your performance

if you feel a big lag in power then your prob borber line , and need to address the fuel concerns

 

I agree, My comment was basically a warning without trying to be too hard. I am percieved as very blunt and sometimes I am misunderstood as being a H8TR, just trying to help and be positive as well.

 

DONT NOT LISTEN TO THIS!! any KR is BAD kr. period. 5* is not something you should have on your car long. Sure you can get away with 1-2* kr and be fine, but any amount of detenation is going to lessen the life of your engine.

People say oh im not getting actual detination because the PCM is pulling timing, however for the PCM to actually pull the timing, it has to sense the detination first THEN pull the timing.

 

i know it is bad..im trying to find out what the prob is.....this means eveyone with a 3.0 pulley that has not been data logging there runs is more likely getting knock retard!!! so everyone with a pulley check your cars before ragging them anymore......i even have 1 step colder plugs and i have been told tons of times that you can run the stock plugs with a 3.0 pulley.....it is only 50 degrees here during the day right now...so with 93 oct and that cold there should be no knock with only 2psi more boost....so somthing is not right here.....i need to get it resolved tho...next week will be inj and maf trans....if that dont work...i dont know.

 

You know what ? The coldest the air is, the denser it is ! The denser air entering the supercharger makes the boost gets even higher than in the summer, and too high of a boost tends to get the knock happens earlier !

Also, the coldest the air is, the PCM gets more timing advance, so it knocks !

Don't be mad with a couple of degrees of knock, maybe you should try 2 step colder plugs to see what happens ?

I will myself install my 3 steps colder plugs tomorrow ...

 

you just learned a valuable lesson....


every car is different

 

Winter changes everything. The MSP hit's fuel cut around this time of year...

 

well in the winter the heat exreacter works better...just like in my tuirbo cars....i would get knock and then it gets cold and no more knock ....my car is not runing any more boost than it did when it was 80 degrees out here 2 days ago....good ol texas 80 degrees one day and 50 the next....anyway....so you are saying our intercoolers work diff? i thought the point of a intercooler was to get ithe air as cold as possable not to get detionation?.....so in thoes term i should not get knock in colder weather.....all my turbo cars ran better in the cold this should not be any diffrent ...right?

 

It's funny.

Winter makes the Charge colder so there is less risk of detonation but it also puts more air Molecules into the same volume of air charge which can cause the car to run leaner easier...

 

Don't forget about "winter gas". Its pretty common knowledge that in the winter they mix in some sort of chemical to help the fuel stay stable. I don't think it lowers the octane rating, but I know it causes more knock. I've talked to many people who don't understand why they get more knock in the winter and I've read about this stuff before. I'll see if I can dig up a article.

 

As Rob said, you need fuel. Gm recommends fuel injectors and minor tuning before even going to a 3.1" pulley (gm stage 2 kit). You need to get fuel injectors and a maf translator and I believe it'll go away.

 

Straight from Chevron:

We have already discussed two related changes in gasoline composition which decrease fuel economy: adding oxygenate and adjusting the octane of oxygenated gasoline. Adjusting gasoline volatility for seasonal ambient temperatures also requires changes in gasoline composition. Summer gasoline is given a lower volatility to avoid vapor lock and minimize evaporative losses. Winter gasoline (both conventional and oxygenated) is given a higher volatility to facilitate starting and warmup. The compositional changes required for the shift from summer gasoline to winter gasoline decrease the gasoline's energy content. Depending on the magnitude of the volatility change, the fuel economy of winter gasoline will be 0.5% to 1.5% lower than of summer gasoline.

http://www.chevron.com/products/prod...realwrld.shtml

 

I installed the Denso Iridium IK27 (three range colder than stock), but there was a LOT of knock with them. As expected earlier, since the electrode is so small and take less voltage to spark, they seem to spark either stronger or sooner, giving some knock (the timing being not optimised). I went back to NGK V-Power BKR7E.