Will SAFC II help knock on stock car?

[turbo2086]

Okay guys just out of the blue my car is getting readings of knock. I used to boost 15psi at 0 knock in a third gear pull on a stock fuel system in 80 degree weather on 92 ocatane. I added a hard intake pipe, and took out the vacuum hoses and capped them off on the throttle body. Now the weather is like 65ish, and I have 93 octane, and boosting 13 psi, and I'm getting like 6 counts of knock. I'm going to redo my base timing, but I do not think it can change on its own without the CAS moving. And cant imagine the hard intake piping causing this...

My o2 readings are at .89. and injector duty at 95.8%. I do not think it is phantom knock, cause I did replace the lifters when I got it. The knock hasn't gotten bad where I notice timing being pulled, but I'm just dumbfounded on why i'm getting it now, and not when I was boost higher in higher degree weather Any ideas guys? thanks

 

[larsenracing]

An afcII will help because you can add fuel and get it tuned right. good luck buddy

 

[Brians2gDSM]

are you getting knock once the car is fully warmed up? Or after you have been driving it around for a little bit? When I replaced my intake elbow on my trans am to a hard one I started getting knock readings. (almost the same thing as the hard intake pipe) I attributed that to the fact that the metal intake held heat longer than the rubber piece did. Heat soak, a hotter intake charge, PLUS going through the turbo maybe your getting warmer air than you'd want? Try putting your stock intake back on and see if you still get knock. If so, you may have found your culprit. If thats what you end up doing, pm me if you solve your knock problem. I have been debating putting a hard pipe on, but if it has a tendency to heat soak then I may not be so interested. Good luck, keep us updated!


~Brian

 

[Quasimondo]

An afcII will help because you can add fuel and get it tuned right. good luck buddy

Yes, and no. An AFC will help because you can richen up the air/fuel mixture, but if you richen it too much to compensate, you'll end up with fuel cut. With your injectors at a 95% duty cycle, you really can't richen it out any more than you already have (plus it's not good for the life of your injectors to have them run any higher than an 85% cycle). At this point you'll need to look at other alternatives before you commit to an AFC, such as re-wiring the fuel pump or replacing it with a 190 lph fuel pump. You're going to need more fuel, but I don't think at this point installing an AFC is the way to do it.

 

[turbo2086]

That makes sense about the heat soaking intake pipe. I would hate to put the rubber one back cause I bought it... Maybe I'll try some thermal wrap like they use on exhaust headers?

I did rewire my fuel pump. I would like to get the 190 now, but I know I will keep building her up, so I will need a 255, then fpr. So I'm just saving up tell I can get all of that at once.

 

[Brians2gDSM]

if heat soak is whats causing your knock then a wrap should help out a bit. I am curious though, aside from looks what is the benifit from running a solid intake pipe VS the stock rubber one. I won't belive turbulance because once the air goes through the turbo and straight air is going to be turbulent coming out of the turbo. They look cool, thats for sure however!

~Brian

 

[Quasimondo]

Stock piping is restrictive, especialy around the BOV flange where the inside diameter is reduced to 1.5"

 

[Brians2gDSM]

we aren't talking about the upper intercooler pipe, we were talking about the stock rubber intake tube, I believe.


~Brian

 

[milz]

The stock intake is very restrictive.. Have you ever pulled off the intake and looked at the size of the inlet to the turbo? The smoother you can flow air to the turbo the more effective your turbo can be.

 

[Brians2gDSM]

I'd love to see a side by side comparison from the stock intake boot to an aftermarket solid piece. It seems like a bunch of marketing hype to me. Id love to see the dyno numbers if there is an actual difference. Aside from the BOV return silencer I don't see how much more restrictive the stock boot is compared to the aftermarket solid piece.