Probably because the injector scaling value is not linear like it appears to be.

 

Guys--sorry to butt in here, but I am dialing back boost to around 7-8 lbs. I get around 310 grams per sec at 7.5K at that level in the weather here in Ga.
Before i was running the stock injector set up with it and really didnt have a problem, BUT I was feeling I was about on the edge. I have the 09 fuel pump in. No issues.
Would the reds, blues in P2 and the yellows in the secondary be a better choice?
Since I now have the Cobb-- i will be looking (with Steve Kan) at all this also, just want to get started right.
thanks
OD

 

Yellow, Blue, Blue is the best choice, all things being equal.

 

Does latency change or stay the same for uncapped vs stock injectors?

 

Was looking at the pdf doc for these injectors the other day.
Your injectors where flowed at 2.5 bar around (1 bar is 14.508 psi, I think) or 36.27 psi
I guess ideally they should have been tested at 60 psi ....

Understanding that the scaling is not linear (as mentioned already) I would not expect the scale to move down ...

Am I seeing this wrong?

Would the injectors not be flowing more fuel at 60 psi than 36 psi? Therefore the injectors should be at least scaled up .... to some magnitude?

I can attach the pdf if requested.

 

That is exactly the thinking that had me hung up for a while. I thought for sure having Flowtested injectors would mean one parameter i didnt have to guess at and if anything our fuel rails higher than tested pressure would mean MORE fuel. But it didnt work out that way. I tried to make them work as "900cc" but they just dont put out that much fuel. A 900cc injector calls for a setting in the AP software of ~1100. But they didnt hit target AFRs until I lowered the setting considerably. I just checked my last few versions of my tune. I was running them with a value of 850 in the Racetuner software(which is approximately the setting for a 700cc injector).

 

Thanks Kane--when are you going to be home?
So yellows--P1
blues on bottom rail?
Is that right?

Od out until he can contribute something--which may be a WHILE!

 

OD - yeah, yellow on one rail, blues (qty 4) on the other rail.

 

OD - if you are dialing back the power to well below 300 you would be better served by leaving well enough alone and sticking with stock injectors .

 

The man has a point.

Though I thought part of the allure was the better atomization of the blue injectors....

 

Thanks for the info .
The (NA now but later going FI) car i'm tuning at the moment has uncapped yellow P2s and to get the AFRs to be the same as when the stock injectors were in there I had to set them to 533 . Figure that one out ......

 

Nothing is linear..... makes the game fun I guess.

The problem is that pressure as a derivative is not particularly consistent. I mean one look at the MAF scale, IAT etc should clue you in on that.

Best thing to do would be flow test them at 60PSI, barring that, scale them the same way you scale the stock ones.

 

So... uncapping injectors has unpredictable flow rates and consequences???



Nooo .... that means I will have to scale my injectors regardless .... exactly what I was trying to avoid :/


New plan:
1) Get injectors scaled while NA, keep them stock for my power goal of 250whp, screw trying to get under the UIM until I HAVE to...
2) Install Turbo

translation for ppl watching this thread: moar actual tuning rather than discussion to come...

dannobre, can you still send me the blue latency table? thanks!

 

No more so than stock (unless you mess them up physically).

What I am saying is that a 200cc/min injector at 10PSI will not be a 400cc/min injector at 20PSI...unfortunately.

 

poop ... if that was the case we could simply increase the fuel pressure to increase fueling, BUT from high school physics we know that liquids are not compressible .... therefore we cannot increase flow with pressure as we can with Air (a gas)

Am I right?

Also, would it be safe to assume that my injectors now flow LESS rather than MORE than my ECU thinks they do?

 

Increasing pressure does increase fueling to a point, (think old school turbo tuning) it is just not linear really.

I don't know what you scaled the injectors too, my net is too slow to go looking. But scaling them NA before going FI is always a good idea.

 

I thought I gave pretty good instructions on how to factor out the anomalous injector scaling values in the seminar.

That said, here is my FUELING CALCULATOR

 

^^^ Thanks for that Jeff

 

Started a new thread specific to an issue I'm having with P2 scaling - any help would be appreciated .

https://www.rx8club.com/series-i-engine-tuning-forum-63/problems-scaling-p2s-209721/

 

well I just ordered 4 blues (reconditioned --but flow tested etc ) for $160 for all 4. Nice price.
I am dialing back, but I still feel I need a little more than what stock will give me and stay in the 80% duty cycle.
Stock is around total at aprox 2080 cc--right? If my calculations are right I need around 2000cc total flow. So with the oem set up that would be very close to 100% duty cycle.
The yellow and blue set would be 2680cc or which may be a bit much unless later I decide to use the power level?
Now if I went with reds in P1, blues in P2 and yellow in secondary then that would be 2280cc. That may be about right and still keep my idle and low in ok?
Blues to atomize more--heck the 09's do a better job than all of them.
I will probably start out with the reds/blues and yellows. Then see.
I think I will be over 300 gram/sec--prob between 310-320 is where I expect to be.
Wish I could put the 09 set up on.
OD

 

Yeah - that is right at the high point of the OE fuel injection system with no changes (2100cc).
That should equate to about 220 wheel horsepower on a 7 PSI supercharged car.

 

Wouldn't you be better to use the 4 blues.....the latency tables would be correct that way for all 4.......otherwise you have an error right off the bat for that

So yellow/Blue/blue??????

 

Well, I think that is what OD is doing now ... I am going to probably do that too ... I need to acquire the injectors first.

For now, I am going to practice with scaling for NA .... once I got my lazy *** out of my warm house and into the cold outside to do some logs....

but yellow/blue/blue is the idea for the future ... big thanks for the latency table btw

 

before I was getting around 275 rwp
I think i got my numbers wrong--recalculating for approx 325 crank HP(approx 275 at the wheels?) and max of 80% duty cycle and 55 psi fuel pressure I would need 2280 cc total flow.
The yellow/blue/ blue should be is right on?
Then no scaling issues like Dan mentioned?
I will see how that runs by next w/e--motor going in now but taking my time--lots of little stuff to do.

 

Less latency issues....scaling will still be off by whatever they could be off stock