Another tuning question

[subie22]

Ok well been doing research on tuning with a logger and a safc, from doing research i noticed that when you install a 2g maf, and 550 injectors you can put the setting to 0 on a SAFC. But since i am running 650cc injectors. I noticed that theres not many people running those particular injectors. But anyway am i gonna have to do some crazy tuning with 650cc, since they are only about 100cc's more, where should i put the low throttle point settings on my safc for ex: 0 across the board on the safc. I am running a aeromotive fuel pressure regulator at about stock 1g fuel pressure. But i have boost leaks, but since its an idle test i am trying to do right now, i dont think that would matter until i hit mid to higher rpms. Any help would help thanks.

 

[turboglenn]

Each car will be different as to where the settings need to be. Use the method outlined on RRE's page to get your base settings dialed in, then get use of a wide band for the final tune.

 

[JayRolla]

Just set up the lo throttle trims on the logger and make sure they are at around 100%. Start at zero and pull fuel till they get around 100%. Then as stated above make sure you get a wbo2 for wot and cruising.

 

[FFTec - jerry]

Hello,

Here's a bit of information about the AFC that you should know before you start tuning and logging away.

Full Function: Facts about Tuning

Jerry

 

[dsm-onster]

Ok well been doing research on tuning with a logger and a safc, from doing research i noticed that when you install a 2g maf, and 550 injectors you can put the setting to 0 on a SAFC.

What posts were these?

This thread may be of interest: 2g mass air sensor in a stock 1g.

Though the sensor at certain airflow levels may demonstrate appropriate offset for 550cc injector flow, I suspect the actual curve of the tranfer funtion is not the same. Thus at other airflow levels, you could see significant knock due to improper airflow metering.

You'll need 43.5 psi base fuel pressure to to get 550s to be dialed in at the 1000 hertz flow point according to my post in that thread. Before and after is determined by the curve. . . and who knows that?. . . Tell us if you do!

But since i am running 650cc injectors. I noticed that theres not many people running those particular injectors. But anyway am i gonna have to do some crazy tuning with 650cc, since they are only about 100cc's more, where should i put the low throttle point settings on my safc for ex: 0 across the board on the safc. I am running a aeromotive fuel pressure regulator at about stock 1g fuel pressure. But i have boost leaks, but since its an idle test i am trying to do right now, i dont think that would matter until i hit mid to higher rpms. Any help would help thanks.

Suggestion? just get a logger and set your safc for the difference of 550s vs. 650s. 100cc difference in fuel flow is huge. Enough for 'crazy tuning'.

 

[JayRolla]

What posts were these?

This thread may be of interest: 2g mass air sensor in a stock 1g.

Though the sensor at certain airflow levels may demonstrate appropriate offset for 550cc injector flow, I suspect the actual curve of the tranfer funtion is not the same. Thus at other airflow levels, you could see significant knock due to improper airflow metering.

You'll need 43.5 psi base fuel pressure to to get 550s to be dialed in at the 1000 hertz flow point according to my post in that thread. Before and after is determined by the curve. . . and who knows that?. . . Tell us if you do!


Suggestion? just get a logger and set your safc for the difference of 550s vs. 650s. 100cc difference in fuel flow is huge. Enough for 'crazy tuning'.

Yes he is correct, I have to add about 4-5% fuel to get a good 11.1 afr. The motor runs a little lean at wot running a 2g maf and 550% on a 1g.

 

[spyderturbo007]

The 2g MAS pretty much compensates for the 550cc injectors, but it's not always exact. Assuming it was, mathematical correction for the 2g MAS and 650cc injectors would be -15% to hit the stock AFR of 9.5:1.

 

[dsm-onster]

Nathan, you're probably the one to ask here. Does the 2g maf transfer function have the same curve as the 1g maf, but 25% or so lower? In other words, do you see a stock air/fuel curve of you run 550s w/ the 2g maf?

 

[spyderturbo007]

Nathan, you're probably the one to ask here. Does the 2g maf transfer function have the same curve as the 1g maf, but 25% or so lower? In other words, do you see a stock air/fuel curve of you run 550s w/ the 2g maf?

Sorry, I've been away for awhile with the Holidays and everything.

Yep, you're correct Matt. The 2g MAS just bypasses more airflow around the sensor than the 1g MAS does, so the ECU will have no clue of the additional airflow. So although you're injecting more fuel with the 550's the 2g MAS will compensate with the bypassed airflow.

There will be some variation because of differences in injector flow rates but it won't be much.

 

[dsm-onster]

There will be some variation because of differences in injector flow rates but it won't be much.

So the transfer function, or curve of the 1g maf airflow vs. hertz graph would be the same shape but occurring at a different level on the graph. Here's what I'm saying: