controlling knock in mid rpm, when not on it.

[awdEAGLEtsi]

what can you use to control knock in the mid rpm ranges when you aren't driving it hard, while using a safc. i was reading and they said, that its good for idle and low rpms, and also upper rpms but when you are just cruising sometimes you can get really bad knock, because of the way it calculates everything. i would appreciate details or a link to where the answer is thanks.

 

[Gooberlog]

maybe set your low and hi throttle settings to a closer percent so that the average of the two is closer, this would work if your hi and low trims were similar, but if they differ it might give you a crazy mixture.

 

[kpt4321]

I don't know what you mean, or where you got that information.

The way it "calculates everything" doesn't make knock while crusing any more likely.

 

[awdEAGLEtsi]

this is where i read it, i think....

http://www.dsmtuners.com/forums/showthread.php?threadid=105569

i hope i just didn't miss understand it. its a loooooooooooong article, but please fill me in.

 

[kpt4321]

I wrote that, so I would know. I don't remember saying anything about the SAFC making you know, because it won't.

 

[awdEAGLEtsi]

here this is the part i have a question on...how can you fix that...the problem is in the last paragraph but the lead up is the first one:


"One of the main side effects of changing the airflow with a SAFC, is the profound effect it has on timing. The timing map in the ECU is set up as such: the ECU looks at the engine speed and the airflow (actually the airflow per rev, but we wont go there right now), and then finds the point on the timing map. The timing map is just set up like a spreadsheet, with the columns representing either engine speed or airflow, and the rows representing the other. The tendency of the timing map is that lower airflow (less load on the motor) gets more timing advance. This is for a couple reasons, but generally lower load means less heat and less cylinder pressure, which means you can use more timing advance to get the mixture to combust at the correct point. The effect this has is that if you reduce the amount of airflow that the ECU sees, it will move down on the timing map, and you will get more advance.

You need to be very careful with this. Not only do you get more advance at WOT, but you also get more advance at cruise and part throttle. In most cases, the WOT knock that can be caused by too much advance can be tuned out, but the knock caused at part throttle and when the turbo is spooling can’t always be."

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please clarify...or if i am retarded, explain to me why i am retarded, so i can fix my retardation problem. thanks

 

[kpt4321]

Ohhh! I understand what you are saying!

This is an issue with any device that lowers the airflow signal in order to compensate for larger injectors, not just the SAFC. VPC's, the MAFT, the GCC, the AFR...they will all do this.

You compensate for larger injectors by lowering the airflow signal; a lower airflow signal gives you more timing advance.

 

[white 2g awd]

more timing advance at such a low rpm would induce more knock correct kyle?, and also like awdeagletsi is asking, any way you can correct this, an eprom chip setup for your specific size injectors would help wouldn't it?? (such as a keydiver chip?) thanks.

Dustin

 

[kpt4321]

Yes, it can induce knock.

Yes, injector compensation gets rid of the extra timing (which may not be a good thing in all cases).

 

[awdEAGLEtsi]

so is there anything you can do to fix it? and if not, how bad is it really? it almost seems like it would be worse than knock at high rpm, since you spend most of hte time at part throttle. especially if you travel and use cruise a lot, it seems like it could be very bad. more ideas please. thank you for all the help. out of all the forums i have ever been in, this could be the most helpful one, and most non-a$$holish one. thanks

 

[kpt4321]

There isn't really a direct fix, it's just something you have to deal with if you choose to tune by changing the airflow.

Knock at part throttle is not as bad as knock under full boost; peak cylinder pressure is less at part throttle, so the knock will do less damage to the motor.

 

[awdEAGLEtsi]

so tuning by adjusting fuel would be better...or by fuel and airflow? and what piggy back systems would you recommend to do that...or possibly another cheaper way?

 

[yo2001]

I'm getting way too much timing in 5th gear 3500rpm and up to 20 knock sum under partial throttle also. I guess the ECU doesn't know the correct load.

 

[crankbender]

I never understood why they choose to do it this way. For the electronics guys out there (i consider myself one but want some back up here) wouldn't it be easier and more cost effective to intercept the signal to the injectors and reduce Duty cycle that way. I mean you wouldn't have to do any frequency modulation at all inside the piggy back just change the duration of the dc signal correct?

I should develope and patent this thing. hmmmmm i even know some people who could do the chip programming for me.....

Figure an afc without the timing changes for about 150 retail......

 

[awdEAGLEtsi]

hook me up, man, i will test it for ya if not i need another way to do this, with out getting knock. ideas, ideas.

 

[awdEAGLEtsi]

anyone? any ideas....is it anywhere else in this forum. i haven't seen any talk about this.

 

[kpt4321]

Keep in mind that if you tune post-ECU, then you lose half of the benefits of a SAFC. Sure, you no longer effect timing, but one of the reasons tuning with larger injectors gains you power is because of that timing.

Also, a SAFC allows you to reduce your airflow signal and thus to delay fuel cut from occuring.

If you want to run post-ECU corrections, you need to do timing AND fuel. In my experience, timing tuning is more important that fuel tuning anyway.

 

[awdEAGLEtsi]

ok and that means what? what would i need to by to do the total tuning and elimate knock...or have the ability too?

 

[crankbender]

if you are really going to go this far do it right and get a stand alone.

IMHO


KPT that is absolutely true. However I don't see a problem with it as you will want to tune the timing eventually. It just seems that you could just about use a standalone at this point.

 

[awdEAGLEtsi]

what stand alones do you recommend, and how much do they cost?

 

[awdEAGLEtsi]

lets get some more info on this, i haven't seen any, any where else. as for standalones they are way to expensive...is that the only way?!?!?

 

[kpt4321]

Is what the only way for what!?!?!?!?!

 

[awdEAGLEtsi]

........is a standalone the only way to totally control and eliminate excessive knock at all rpms and under all throttle positions?

 

[kpt4321]

If a SAFC made it so every always would have excessive knock at part throttle, do you think people would still use them?

I said it COULD cause excessive timing which CAN cause knock. That's all.

It might not do it at all, and if it does you just have to tune it out.

 

[Jasper16g]

If you have a 2nd gen I would suggest you look into a dsmlink. You can adjust fuel and timming seperatly with it.

Jason