I think I will buy a cheap fuel pressure guage and see how the fuel pressure is.

I am also buying a new wideband guage to check and make sure that my AFR is really what my guage says.

Is it normal for a bolt on evo IX to max out the injectors with a walbro and about 22 psi of boost or so.

My load is hitting almost 300 in some places.

 

Its actually pretty unusual to max out your injectors, even if your hitting 300, even moreso with an upgraded fuel pump.

You could have a clogged fuel filter, or an issue with fuel pressure, or the pump was installed improperly meaning the fuel isn't being drawn into the pump properly. (resulting in lower than normal fuel pressure.

 

If I install a fuel pressure guage, what exactly should I be looking for?

I did the fuel pump install myself and I think I did everything correctly. Are there any common mistakes with fuel pump installs?

 

You are looking for a 1:1 fuel pressure rise with boost and you want to make sure that this is kept all the way to redline.

For example, I think the base fuel pressure on the Evo is 43.5 psi (check that though, not sure off the top of my head). So, if you were running 25 psi of boost, your fuel pressure should be 68.5 psi and shouldn't fall from there, as long as your boost isn't falling. Your fuel pressure should always be base pressure+boost pressure.


Eric

 

yea that is what I figured, and you are correct about the 43.5 psi
Although some say that with a walbro, your base pressure may rise becuase the FPR can not flow enough at idle.

I will install the guage and watch for 1:1 rise in fuel pressure.

 

On my current maps (FQ360 maps on an FQ320) with a walbor and de-cat, using stock BC (dual-solenoid) with WGD at 100 except a little lower at peak with pills still in, in 4th, I see:

3000rpm, 12.1afr, 19.4psi, 43idc
3200rpm, 12.0aft, 23.0psi, 50idc
4000rpm, 11.8aft, 22.1psi, 61idc
5000rpm, 11.3afr, 22.3psi, 75idc
6000rpm, 11.5afr, 21.1psi, 87idc
7000rpm, 11.1afr, 19.7psi, 94idc

Hitting 270 load at 3500 (calculated from AFRMAP)

On a slightly different map, around 7500rpm, I have seen IDCs at about 107 but that was with Lean Spool Disable at 7000rpm, afr would probably be mid to high 10s.

M

 

I'm seeing the same thing. I don't believe the numbers are accurate.

 

are JDM injectors, and FPR the same?

 

I dont think the numbers are entirely accurate either, although either way if I have max fuel in my fuel tables and I am still at lean AFR, it would indicate that my injectors are maxed out.

 

It means that some part of your fuel system is maxed out, not necessarily your injectors. Your Walbro could also be flaking out. It is a very inexpensive fuel pump, so every now and then there's a bad one. With stock injectors and the mods in my sig (other than injectors) I was still able to get to 11:1 at 7000 RPM and 20.5 psi so it seems unlikely that you could be flowing that much more air, although I suppose anything is possible.

-Paul

 

I was having the same problem before I installed my walbro, but that was on a stock pump, so it makes sense that it was getting maxed out. I wont be able to check my fuel pressure for a couple weeks as I am up at school now and dont have access to my tools. Although I suppose a fuel guage install will probably be very easy.

I am about to order a fuel pressure guage and an adapter to install it. Does anyone know the I/D of our fuel lines at the place where I would be installing the guage.

This is what I am going to buy, any one object.
http://store.summitracing.com/partde...=16383&N=700+0

plus this (assuming the I/D is correct)

http://store.summitracing.com/partde...part=SUM-G1710

 

hmmm. If you search you might find a thread from JeffR a little while back...where he was seeing issues where he was setting his AFRs as rich as possible but the wideband was reading lean. Turned out the culprit was indeed the walbro....makes me wonder if I should sell mine before I put it in........

Edit. Found it:

https://www.evolutionm.net/forums/sh...d.php?t=228352

 

The thing is that 100% duty cycle means the injectors are no longer closing. They are open during the entire 4-stroke cycle. So there's no way to physically go beyond 100% duty cycle in real life. But if you are correct about the IPW scaling formula being correct, then the ECU must not know/care about the 100% limit. It just throws a pulse at the injector, and if the pulses overlap, no big deal.

But that would also mean that the IDC value he's seeing means that his injectors are definitely going static. Even 10% error in both IPW and rpm wouldn't wouldn't account for the difference in his 130% value and the phyical limitation of 100% duty cycle. That would mean that quite a few mildly modified Evos with no fuel flow mods are running their injectors right up to the limit.

 

That was also my impression.. I do think there is a calculated limitation that it seems to occasionally go outside of..

Injector Voltage Latency, and other dead time settings could be a contributor as it does alter things a bit..

 

MPI (multiport injection) is a sequential fire system, so your right about it not overlaping.. Once your 100% duty, it really doesn't matter what value it reads..

I have to look at the IDC formula again.. although I am under the impression its per crank rotation (I'm recalling my 4 stroke engine theory, and isn't it 2 crank rotations per cycle?) (Intake/Compression and Combustion/Exhaust)

This brings up other thoughts, assuming there really is an injection window based on intake stroke only, this could also play into cam profile, so it makes no sense to me that it would work this way.