Problems with scaling P2s
12-30-2010, 03:35 PM
#1
Problems with scaling P2s
I'm currently remote tuning an NA engine in preparation for FI . The owner has fitted yellow uncapped injectors in the P2 position . These should flow around 750ccs according to the data from the shop that flow tested them.
However if you look at what happened when I scaled the injectors to accomodate 750cc you can see that it went very lean .
To get back to where the stock injectors were I had to scale them by only 12% .
Only reason I can think of for the low flow is that one of the injectors is not working at all . If this were the case how would we go about testing this ?
Can anyone else see any other possibilities ?
Ignore the 8000rpm result - that is another issue to be resolved .
However if you look at what happened when I scaled the injectors to accomodate 750cc you can see that it went very lean .
To get back to where the stock injectors were I had to scale them by only 12% .
Only reason I can think of for the low flow is that one of the injectors is not working at all . If this were the case how would we go about testing this ?
Can anyone else see any other possibilities ?
Ignore the 8000rpm result - that is another issue to be resolved .
Last edited by Brettus; 12-30-2010 at 04:34 PM.
12-30-2010, 03:57 PM
#2
Something else is going on with this......you can see where the P2 are effecting the Lamba # in the bottom 3 plots......In the 7000 and above area.
Adjusting the scaling effected the whole thing with the 97% scale...so something else did that
Maybe force it into open loop and try the logs again...cause something is very strange
Adjusting the scaling effected the whole thing with the 97% scale...so something else did that
Maybe force it into open loop and try the logs again...cause something is very strange
12-30-2010, 04:22 PM
#5
It only went very slightly rich after the p2s were changed . I would have expected it to go VERY rich . Then when I scaled to 97% it went VERY lean when I would have expected it to be close to what it ran before the swap .
so for that suggestion you get 
12-30-2010, 05:01 PM
#10
But we can't log without the o2 sensor ?
OOPS...forgot everyone doesn't have WBO2 extras
It only went very slightly rich after the p2s were changed . I would have expected it to go VERY rich . Then when I scaled to 97% it went VERY lean when I would have expected it to be close to what it ran before the swap .
OOPS...forgot everyone doesn't have WBO2 extras
It only went very slightly rich after the p2s were changed . I would have expected it to go VERY rich . Then when I scaled to 97% it went VERY lean when I would have expected it to be close to what it ran before the swap .
Well....you really don't have a lot of options...you either believe one thing is valid or the other
If you don't know that the injectors are working I guess that's a good place to confirm before you go much further
Not a common failure though.....loose plug would be more likely...or the wire got pulled out when the injector was removed and there is poor contact
What does it run like? You would think that it would run like crap with one rotor very lean...and the other really rich????
Last edited by dannobre; 12-30-2010 at 05:03 PM.
12-30-2010, 05:31 PM
#11
Well....you really don't have a lot of options...you either believe one thing is valid or the other
If you don't know that the injectors are working I guess that's a good place to confirm before you go much further
Not a common failure though.....loose plug would be more likely...or the wire got pulled out when the injector was removed and there is poor contact
What does it run like? You would think that it would run like crap with one rotor very lean...and the other really rich????
If you don't know that the injectors are working I guess that's a good place to confirm before you go much further
Not a common failure though.....loose plug would be more likely...or the wire got pulled out when the injector was removed and there is poor contact
What does it run like? You would think that it would run like crap with one rotor very lean...and the other really rich????
12-30-2010, 09:51 PM
#16
perhaps I need to explain a little better
log 1 : stock P2s - all good but slightly lean of target .
Log 2 : P2s changed out for 750cc uncapped yellows : AFRs go slightly richer . Nowhere near as rich as expected .
Log 3 : P2s Scaled up by 97% . AFRs go horribly lean
Log4 : P2s rescaled to 12% more than stock . Afrs go back close to what they were with stock yellow P2s .
Some math ......
280x2+380x2+380x2 = 2080cc Total
280x2+380x2+750x2 = 2820cc Total
total fueling has increased by 35%
So fitting the 750cc injectors should have produced Lambda of 0.64ish - instead we got 0.85ish
280x2+380x2+750x1 = 2070cc Total
If only one 750 injector was working the total fueling figure is much the same as before the swap was made . So Lambda would be similar Which is close to what actuually happened .
So my best guess is that only one injector is working and flowing a little more than 750cc s.
log 1 : stock P2s - all good but slightly lean of target .
Log 2 : P2s changed out for 750cc uncapped yellows : AFRs go slightly richer . Nowhere near as rich as expected .
Log 3 : P2s Scaled up by 97% . AFRs go horribly lean
Log4 : P2s rescaled to 12% more than stock . Afrs go back close to what they were with stock yellow P2s .
Some math ......
280x2+380x2+380x2 = 2080cc Total
280x2+380x2+750x2 = 2820cc Total
total fueling has increased by 35%
So fitting the 750cc injectors should have produced Lambda of 0.64ish - instead we got 0.85ish
280x2+380x2+750x1 = 2070cc Total
If only one 750 injector was working the total fueling figure is much the same as before the swap was made . So Lambda would be similar Which is close to what actuually happened .
So my best guess is that only one injector is working and flowing a little more than 750cc s.
Last edited by Brettus; 12-30-2010 at 10:12 PM.
01-02-2011, 08:42 AM
#21
i didnt explain myself well--i need more lessons from Swoope
The fuel pump does go to the high out put mode at a certain tps %/load, like you were referring too--ifs there is a sudden change in pressure wouldnt bigger injectors respond in a stronger manner? I know the fp regulator comes into play here but if its low to begin with.....?
Really just guessing--but dont you need to know for a fact the fp pressures you are dealing with before any scaling is done? Or does that matter?
OD
The fuel pump does go to the high out put mode at a certain tps %/load, like you were referring too--ifs there is a sudden change in pressure wouldnt bigger injectors respond in a stronger manner? I know the fp regulator comes into play here but if its low to begin with.....?
Really just guessing--but dont you need to know for a fact the fp pressures you are dealing with before any scaling is done? Or does that matter?
OD
01-02-2011, 09:32 AM
#22
Fuel Pressure does matter.
However, it is an expensive mod to an NA vehicle, so I could see where you wouldn't want to do it.
In that graph, add in duty cycle....if your in transition, funky things can happen if your scaling or latency is off. Or hell, for that matter, the Fuel VE% map can mess with it too.
However, it is an expensive mod to an NA vehicle, so I could see where you wouldn't want to do it.
In that graph, add in duty cycle....if your in transition, funky things can happen if your scaling or latency is off. Or hell, for that matter, the Fuel VE% map can mess with it too.
01-02-2011, 09:52 AM
#23
Without further information I fail to see the problem here. You figured out a scaling that worked. It wasn't what a simple calculation said it should be, but so what? It sounds like there are no other signs of anything else being wrong.
Here's an example. I was scaling some 740cc injectors on a 2005 STi not too long ago (stock size is 550) with Cobb AP. It was a matched set from Deatchwerks. I had flow test and latency data from the manufacturer and another set of numbers to try from Cobb. I put the data into the AP. With both set of numbers it ran like ****--stupid rich. I ended up taking the stock scaling and made an across-the-board correction to the latency and all the trims fell in line.
Even though they didn't behave as I expected, there was nothing wrong with the injectors. The turbo was upgraded and the boost increased. The car runs fine and the trims are all within an acceptable range.
Here's an example. I was scaling some 740cc injectors on a 2005 STi not too long ago (stock size is 550) with Cobb AP. It was a matched set from Deatchwerks. I had flow test and latency data from the manufacturer and another set of numbers to try from Cobb. I put the data into the AP. With both set of numbers it ran like ****--stupid rich. I ended up taking the stock scaling and made an across-the-board correction to the latency and all the trims fell in line.
Even though they didn't behave as I expected, there was nothing wrong with the injectors. The turbo was upgraded and the boost increased. The car runs fine and the trims are all within an acceptable range.