tune to run more boost or leaner afr?

[sciondan]

Ok, so I'm fine tuning my set up and have a question. Should I tune for 11.0 afr and adjust boost to were I just start seeing a couple counts of knock, or should I set a Target boost level and adjust afr to get rid of knock? What would net better performance, leaner afr with lower boost, or higher boost with a richer afr? Basically right now at 17lbs I get around 10 counts of knock at 11.0 afr. Too tune out knock I have to go as rich as 10.0 to 10.5 afr.

 

[Ppayer38]

You have issues if you get that much knock already on that low of boost. There is no 1 way to tune a car whether it be a Subaru, DSM, Evo, etc...

It is all a combination of things and I'm saying you have to much timing. Also a EGT gauge helps understand what the motor is doing a little better then just having a WB.

 

[snowborder714]

Actually, neither.

1. Set boost to what you want to run. If something ridiculously high like 35+ psi, set to lower level to get airflow roughly dialed in. If reasonable boost level, set it and move on.
2. Get your airflow dialed in.
3. Adjust fuel if need be to hit your target AFR.
4. Adjust timing if need be to control knock. If you see knock, reduce timing by how much knock is seen. If no knock is seen, then you can increase timing little by little until you see knock, and then back it off.

 

[BoostedBeaver]

4. Adjust timing if need be to control knock. If you see knock, reduce timing by how much knock is seen. If no knock is seen, then you can increase timing little by little until you see knock, and then back it off.

Follow this ^ to control your knock.

Since you are onlly using a pocket logger, you are on the stock 1g timming map which is really aggressive. Back the timming off a few degrees in the area where you are seeing knock and then continue your adventure.

Robert

 

[sciondan]

Using safc to tune so cannot adjust timing. Timing under boost is around 20 to 22 degrees.

 

[snowborder714]

Well, that's a problem

I would say meet somewhere in between. Leaning out to 11:1 at 14psi probably won't be as nice to drive as 21 psi but running 9.8:1 AFR. I'd shoot then for a mid-10 AFR and whatever boost matches.

Then I'd get a tuning solution that can control timing so you can eliminate this situation.

 

[BoostedBeaver]

That is the issue!!!

I run this amount of timming on E85 but would have never gotten away with it on pump gas.

You really need to be able to reduce the timming or run a chip with a less aggressive map. The recommended solution is going to be link but it is not in everyones budget. You have to pay to play, so my recomendation is to hold off on tuning the car, turn the boost down a bit, get rid of the knock and save your pennies for link.

On another note, richening up the mixture to far can also cause knock so that is only good to a small extent and is not the correct solution in most cases. I would shoot for 10.5 or so AFR's and go from there.

Robert

EDIT: Man Brain your fast.... we will meet again!!!!!

 

[tkelly27]

Adjust your cam angle sensor to keep you from knocking and save your pennies for an ostrich so you can tune spark. You can save your pennies for dsmlink too, but you'll need 10,000-30,000 more pennies. That is a lot of pennies.

 

[sciondan]

Thanks guys....

Adjust your cam angle sensor to keep you from knocking and save your pennies for an ostrich so you can tune spark. You can save your pennies for dsmlink too, but you'll need 10,000-30,000 more pennies. That is a lot of pennies.

Your saying I can adjust base timing to lower overall advance? Will that change driveability?

 

[BoostedBeaver]

but you'll need 10,000-30,000 more pennies.

That would be a lot of pennies well spent..... of course this is my opinion.

The ECU is set to think that you are running 5*BTDC as your base timming. If you retard the base timming further say 3* BTDC it will effectivley pull 2* from your entire MAP but without acutally pulling it. You will still have the same map but you will be tricking the computer. This can effect driveability and idle but I have not had first hand experience with this particular method. I would conserve the tune until I had something to properly change and alter the values no matter which system you decide to use.

The Ostrich may be a viable solution but I have never used one so it was not part of my recomendation.

Robert

 

[sciondan]

That would be a lot of pennies well spent..... of course this is my opinion.

The ECU is set to think that you are running 5*BTDC as your base timming. If you retard the base timming further say 3* BTDC it will effectivley pull 2* from your entire MAP but without acutally pulling it. You will still have the same map but you will be tricking the computer. This can effect driveability and idle but I have not had first hand experience with this particular method. I would conserve the tune until I had something to properly change and alter the values no matter which system you decide to use.

The Ostrich may be a viable solution but I have never used one so it was not part of my recomendation.

Robert

I set my base timing to 3* BTDC with no negative effects. I do have a question thoe. I log my timing through a data logger, should I see the change in the logs? Or will the computer still report the same timing numbers since the computer still assumes Im at 5*?

 

[BoostedBeaver]

The computer assumes that you are running the CORRECT base timing, so you will not see the changes in a logger. The only time you will be able to see the difference is when you ground the timing connector and check your base timing with a timing light.

I would still suggest getting a tuning solution that offers control over the entire system.

Robert