Question about injectors and turbos...

[clipsekid99]

Wow, thanks alot Kevin, you rule!

[steviek]

Hey kevin I understand the first calculation you did with the injector sizes/compensation but the second one about the leaning of the stoichometry you think you could elaborate on its the one with the 9.5/14 I didn't get where does that 14% come into play and is that a constant applied to any size injector?

[MexRocket]

I just want a simple anwser, 660's or low 700's, 255 pump, FPR, s-afc, evo3GT at around 14-20 PSI. Is that ok to run the car on? And not fuck anything up that I don't want it to? This is a budget racer, aka my personal roller coaster, and might not even see a track. Can the s-afc handle bigger injectors and the pump with the given range of injectors? Becuase I can't really afford dsmlink and TIT big injectors. I am so confused im going to stab my eye with a spork.

[crunchymilk55]

650s or above + SAFC2 = too much timing advance. It's simply lying to the computer too much. Keep saving your money and get dsmlink, or run 550's and see how much psi you can run without going lean on a dyno.

Kevin's post earlier described the timing advance issue thoroughly, so I'm not going to try and explain that anymore. Do it once, do it right.

[kjewer1]

Originally Posted by steviek

Hey kevin I understand the first calculation you did with the injector sizes/compensation but the second one about the leaning of the stoichometry you think you could elaborate on its the one with the 9.5/14 I didn't get where does that 14% come into play and is that a constant applied to any size injector?

At over 2.1 g/rev the ECU's target AFR is 9.5:1 at any meaningful rpm. These charts available to DSMlink users FYI. So a 14.x% change will bring AFR to 11:1. And in reality, that's exactly what it takes. It's not just math, it's the way it really works when everything is in proper working order. That applies to any size injector, since the injector is already compensated for. You can also apply the same calculation to any AFR you want to target. But please note that this is just what the ECU will be shooting for, and your actual AFR may be different is something is amiss, like fuel pressure, injectors not flowing what they are rated at, boost leak, airflow meteting inaccuracy, etc. This is why knowing the difference between the calculated target AFR (DSMlink provides this as "AFratio") and measured WBO2 AFR is so valuable. It can be used to diagnose all kinds of problems. Add calculated boost and measured boost from a MAP sensor and, well you get the point... Information is power (and safety)

[steviek]

Thank you thats what I needed to know
My only thought now is why would the ecu's target be 9.5 when 11 is a better mix?

[crunchymilk55]

Originally Posted by steviek

Thank you thats what I needed to know
My only thought now is why would the ecu's target be 9.5 when 11 is a better mix?

safety first

[steviek]

Heres a question that I think is answerable but I don't know.. Especially don't know how to do the math so Ill just let kevin do it ( IF it is at all possible).
Ok so To my understanding with the rewired 190 and the 550's it can support 39lbs/min on the 16g (2g). Now the 16g max's around 42... Now lets say our line comes off and were running the turbo to the max. But we also have our safc set to -50%. HOW LEAN will You be running {assuming all other factors are negligible (boost leak and what not)}?

[clipsekid99]

Ok, on my budget and wants from my car right now, I would do a rewired 190, 550s, and the evo3. I would like to run approx. 18-20 psi on it, but is that doable on that setup?

Also, how much boost would you have to be running to hit those airflow numbers you were talking about, Kevin?

[MexRocket]

hahah everything is the samething I just posted but just shorter, sorry kevin and crunchy =(

[LouieAWDTSi]

Originally Posted by clipsekid99

Ok, on my budget and wants from my car right now, I would do a rewired 190, 550s, and the evo3. I would like to run approx. 18-20 psi on it, but is that doable on that setup?

I think you'll be fine running 20 psi on that set up. I already run 17 psi(no front mount). Been running it for almost a half yr now with my current set up. You have a front mount so that fuel/turbo set up will benefit(sp) much more. I'm pretty sure the rewired 190 be fine too, but a 255 be safer most likely(fpr is your call).

[kjewer1]

Thank you thats what I needed to know
My only thought now is why would the ecu's target be 9.5 when 11 is a better mix?

Like crunchy said, it's a warranty deterant. Plus poeple do some crazy shit, and things go wrong with sensors and such, it allows for some error margin.

Heres a question that I think is answerable but I don't know.. Especially don't know how to do the math so Ill just let kevin do it ( IF it is at all possible).
Ok so To my understanding with the rewired 190 and the 550's it can support 39lbs/min on the 16g (2g). Now the 16g max's around 42... Now lets say our line comes off and were running the turbo to the max. But we also have our safc set to -50%. HOW LEAN will You be running {assuming all other factors are negligible (boost leak and what not)}?

One way to look it is what will AFR be with maxed out 550s and 42 lbs/min. By reverse engineering the math a bit I get 11.5:1 or so. On a properly set up car this won't lead to catastrophic failure, but if anything in the setup is marginal it could get ugly. For example, bad gas, or the low octane stuff poeple get stuck with in some areas.

550s would be set at -18%, with another ~14% for getting to 11:1, so about -32%. I'm not sure why you'd be at 50%. That would be shooting for nearly 14:1, which is much leaner than you would end up with targeting a more normal AFR but maxing out the 550s, as mentioned above.

Ok, on my budget and wants from my car right now, I would do a rewired 190, 550s, and the evo3. I would like to run approx. 18-20 psi on it, but is that doable on that setup?

Also, how much boost would you have to be running to hit those airflow numbers you were talking about, Kevin?

The boost figure is completely meaningless without knowing a few key points in the setup. Mainly anything that affects VE, or more specifically, displacement, and VE affecting mods like intake manifold, cams, etc. On a stock cammed car, 20 psi would be ok. It would take ~25 psi to get over 40 lbs/min on your "typical" street setup. With just the addition of cams however, you will reach 40 lbs/min at 20 psi. I get 42-43 lbs at 19-20 psi on the EVO depending on temperature. 19 psi in the cold, 20 psi with typical temps for this season, and sometimes 21 psi if it's real warm during the day. You get the idea.

Another interesting thing to note is that by pulling the line off my wastegate actuator and installing my BOV backwards (or run my Gus Modded 1g BOV that I just installed) I get 42 lbs/min across every single gear from start to finish. Boost will hit anything from 25 to 28 psi at the beginning of each gear, but will taper to the same 19-20 psi value at redline. The turbo maxes out based on airflow. The boost is an afterthought. Boost is left over airflow


The best way to keep it safe is to know the numbers, and log airflow. On a 2g any ODB2 logger reads airflow. My pocketlogger read in lbs/min. You can convert this to g/rev with a little work. Unfortunately you can not read airflow on a 1g logger, DSMlink is the only way. DSMlink provides airflow/rev, and airflow/time, in a variety of units.

[steviek]

So then if you say that by your calculations the 550's at -50% can still put the a/f at 11, with the evo16g flowing at max then technically can't the 550's support that turbo?
I do realize it leaves no margin for error

[crunchymilk55]

Originally Posted by steviek

So then if you say that by your calculations the 550's at -50% can still put the a/f at 11, with the evo16g flowing at max then technically can't the 550's support that turbo?
I do realize it leaves no margin for error

until you raise the boost past that calculation.

[steviek]

But the 16g won't be able to raise boost because it is at full boost