Juding by the chart from AMS the Evo 8 pump is not that good. On an Evo 8 it is imperative to replace the pump even with a TBE. Another alternative is to get an Evo 9 pump from someone who installed a winbro on their 9. Most shops throw the Evo 9 pumps away. Contact a tuner shop that has them and see if they will give it to you.

 

dumb question how does fuel pressure get factored in?

ie the pounds of fuel per min drops off as the pressure rises...

is that pressure the output pressure of the pump?

 

Hrmm I think its just that 100% doesn't necessarily mean you are hitting 100% of the capacity of the injector...

ie with a smaller scaling on the same injector your IDC's will be higher right!

ie using 560cc injectors

injector scaling of 542cc
IDC of 80% required for a given load/rpm

injector scaling of 513cc
IDC of 95% required for the same load/rpm

now I guess part of the answer will be why we dial in 513cc scaling for 560cc injectors - why is the scaling always less than the real injector size?

edit: so I guess the real IDC calculation would be (IPW*RPM/1200) * (Injector Scaling/Injector Capacity)

 

My stock injector are scaled to 472 nd not to 513. I have noticed that on several modded Evo 9s a 513 scaling will make the fuel trims go to 10 or max out at 12.5. This makes the car very rich during WOT operation. I am seeing a trend here the more Evo 9s I log.

I used Tephra's method to get my IDC and here are the results of the regular IDC method:



And here are the results using the new method outlined by Tephra:



The IDC is 15% lower with Tephra's method than with the usual method. This makes sense to me becuase even when my IDCs were hitting 100% with the other method, I was still able to adjust the AFR. A 0.2 target AFR change produced an actual AFR change. If my injectors were maxed out @ 100%, then that should not happen. That is why I am leaning towards Tephra's method as the accurate method.

 

now redo it with 2byte RPM lol you will be hitting 105% IDC

 

The pressure is the fuel pressure, which is base fuel pressure (should be 43.5 on our cars) plus boost pressure.

So, for example, 25 psi of boost is 43.5+25=68.5 psi fuel pressure.


Eric

 

ahh makes perfect sense now cheers eric!

ahh ok so the 9 pump should be able to handle upto 30psi (assuming the stock injectors could)

 

has anyone tried the 542 injector scaling with the corresponding injector latency and MAF smoothing tables?

 

So using the 2byte rpm with the original IDC calculation will make the IDC go through the roof

 

That makes a little more sense now. Figures, right after I gave away my un-used Walbro from my civic.

 

fitting a walbro 255 instead of yr evo 8 stock pump, will this increase fuel pressure, keeping everything else constant?? or will the fpr still limit pressure to 3 bar base + boost pressure??

 

@l2r99gst: u made yr calculations based on a 560cc / min injector capacity.
As far as i know 560 is rated at 3 bar, but when your turbo is maxed out, say 1.5~1.6 bar at 7000~7500 rpm, your fuel pressure is 4.5 bar. Provided yr fuel pump won't die, this will lead to a higher injector capacity, right???

 

No, the effective pressure the injectors are seeing are still your base fuel pressure, since your fuel pressure regulator raises fuel pressure 1:1 with boost.

So, even if you were running 50psi of boost, then your fuel pressure would be 43.5 psi over that, or 93.5 psi. So, your injectors are still effectively flowing at their rated 43.5 psi, no matter what boost pressure you are running.

Hope that makes sense,
Eric

 

oh you mean the extra fuel pressure applied from one side are cancelled out by the air pressure in the combustion chamber right??
yeah got it, i somehow missed that

another question: fitting a walbro 255 while helding everything else constant,
will it increase your base pressure?? or will the fpr hold it at 3 bar base + 1:1???

thx

 

Right.

Well, since I don't personally have a 255 on my Evo, I will have to let someone else answer that question. I have seen threads both ways, but most people on here don't log or measure their fuel pressure, so their are more opinions floating around rather that hard fact.

There is a chance that the Walbro will raise fuel pressure at idle, but with the dual fuel pump circuit in the Evo, I would imagine that it wouldn't be so much that the fuel trims couldn't make up for it.


Eric