Duty cycle

[SubiEj255]

I have a '12 wrx, where should the injector duty cycle be? On average modded or unmodded?

[Sinister]

under 90% is recommended

[SubiEj255]

Yea I figured that. I pulled logs my IDCs are 98%. This is with the Cobb stage 1 91 tune, while using 93 octane.

[mycologist]

How much boost are you hitting?

[Ruh Roh]

98% on a stage 1 tune! wow didnt think it'd be that much. And why arent u using the 93 octane tune if your using 93..?

[SubiEj255]

This is by 7k redline. Peak boost is 16.8 or something like that. I don't have the exact numbers in front of me right now. It wasn't higher than 16.8, I do know that. I'm using 91 tune b/c I wanted to use that extra octane as an buffer to "richen" the car up. I k ow these cars run lean, so I wanted to have a small window.

[Calvinball]

This is by 7k redline. Peak boost is 16.8 or something like that. I don't have the exact numbers in front of me right now. It wasn't higher than 16.8, I do know that. I'm using 91 tune b/c I wanted to use that extra octane as an buffer to "richen" the car up. I k ow these cars run lean, so I wanted to have a small window.

Someone with more experience in tuning can correct me if I'm wrong, but I'm fairly sure that octane rating is not going to affect your A/F ratio, or as you put it "richen the car up."

[mycologist]

Someone with more experience in tuning can correct me if I'm wrong, but I'm fairly sure that octane rating is not going to affect your A/F ratio, or as you put it "richen the car up."

Correct, the octane of the gas won't directly but the map will probably give a buffer against knock. I'm not sure how Cobb does it, but the 91 octane map probably uses less timing or a richer mixture to keep the 91 octane gas from knocking. I'd run the 93 map and see for yourself if there is a knock issue or not.

[Calvinball]

Correct, the octane of the gas won't directly but the map will probably give a buffer against knock. I'm not sure how Cobb does it, but the 91 octane map probably uses less timing or a richer mixture to keep the 91 octane gas from knocking. I'd run the 93 map and see for yourself if there is a knock issue or not.

Yeah, I just re-read that post and realized I may have interpreted what the OP wrote incorrectly. The 91 tune might possibly be richer for safety. However, I believe that using 93 gas on a 91 tune is not going to help with anything unless for some reason 91 gas was knocking on the 91 tune, correct?

[SubiEj255]

I pulled logs for both tunes. Knock isn't the issue in either tune. Ill post both with I get to my computer, but the question was the duty cycle of the injectors; why are they almost maxed out? Is this normal? What are the size of the stock injectors?

[mycologist]

It doesn't seem normal to me - it is too high.

Was the duty cycle lower with the 93 map? If it is a leaner map....

[Calvinball]

I pulled logs for both tunes. Knock isn't the issue in either tune. Ill post both with I get to my computer, but the question was the duty cycle of the injectors; why are they almost maxed out? Is this normal? What are the size of the stock injectors?

If there was no knock when running the 93 tune, and you use 93 gas, you should just run the 93 tune. If you are concerned that it might lean the car out too much, contact Cobb and ask them how the a/f ratios differ between the 91 and 93 tunes. Or save some money and just buy 91 gas for the 91 tune. Running 93 octane gives no additional benefit if you are on the 91 tune with no knock issues.

To your questions: All you have is a stage 1 tune, no other mods? If so, that seems not normal. Stock injector size is 565 I believe.

[mycologist]

16.8 psi seems high for a stage I tune, but I think that may be normal for the new maps.

The injectors should be <90 on a stage II map, so there is something funny going on for sure.

[zax]

Unfortunately, the new ATR won't allow me to view the 2012 maps, but classically, Cobb has traded very rich fueling for added timing.

[Donkey]

It doesn't seem normal to me - it is too high.

Was the duty cycle lower with the 93 map? If it is a leaner map....

This. Use the 93 map. The 91 is richer. Plus OTS maps will run rich. I would see about getting a custom tune. Also colder weather = higher duty cycles.