Bumping fuel pressure, how does it affect injector size?

[a73_4g67]

Hi Guys,

I have a set of 560cc Evo 6 Tomi Makinen Injectors. This is the same as the Evo 9 injectors. I believe it flows above 560cc, around 600cc on what I've read. The stock pressure for a 1G is 37psi. If I'll bump the fuel pressure to 47psi, will my injectors flow like 660cc or more? I'm asking this because of a turbo upgrade.

No worry on the ECU end, I can compensate for any injector size without using SAFC. Oh and I have a 255LPH pump with AFPR.

Thanks in advance.

 

[steve]

http://www.rceng.com/technical.htm

Don't guess, send your injectors out and have them flow tested so you know where your starting from.

Steve

 

[timloomis]

Use the formula that rc has on that site shown above.I used the n/t fpr,which raises the base pressure up to 47,and it turned my 450's into 505's.

 

[LessIsMore]

I'm using the n/t fpr also and it bumped my base fuel pressure to 54psi. Seems like I'm over running the n/t fpr with my rewired 180lph denso pump. With the stock fpr I was seeing about 38 psi base fuel pressure using the same pump.

I've also heard the stock evo8/9 injectors flow more like 600cc. I plan on picking up a set.

Assuming the injectors are [email protected], new flow rate at 47psi will be 582cc

Assuming the injectors are [email protected], new flow rate at 47 psi will be 624cc

 

[a73_4g67]

I've set the base fuel pressure at 40psi w/o vac. I'm using a 1G JDM ECU. I've set 560cc for the compensation code in the EPROM. It runs good. Now I'm worried, what pressure does it become 560cc?

Now I'm confused on what pressure to use. 37 or 43.5psi. Are evo 9s using 43.5 psi?

Thats nice info LessisMore. I'll have that in mind. Thanks timloomis, steve for posting the link.

I'm using the n/t fpr also and it bumped my base fuel pressure to 54psi. Seems like I'm over running the n/t fpr with my rewired 180lph denso pump. With the stock fpr I was seeing about 38 psi base fuel pressure using the same pump.

I've also heard the stock evo8/9 injectors flow more like 600cc. I plan on picking up a set.

Assuming the injectors are [email protected], new flow rate at 47psi will be 582cc

Assuming the injectors are [email protected], new flow rate at 47 psi will be 624cc

 

[steve]

I'm using a 1G JDM ECU. I've set 560cc for the compensation code in the EPROM. It runs good. Now I'm worried, what pressure does it become 560cc?

What ECU code are you using? One of the JDM versions or E931?

Steve

 

[a73_4g67]

What ECU code are you using? One of the JDM versions or E931?

Steve

steve,

I'm using an E952 program that came from the JDM GVR4 RS (240ps). I edited the injector size value from 510cc(41 Hex) to 560cc(3B Hex) in the EPROM. I also edited the injector deadtime map for that injector. Im using a JDM GVR4 Engine.

Now, Im not sure what base fuel pressure to use.

 

[steve]

Whatever the base pressure was for that JDM car. Since those numbers match the E931 globals I'd guess it was set up for the same 36.3 psi base fuel pressure.

Steve

 

[a73_4g67]

Whatever the base pressure was for that JDM car. Since those numbers match the E931 globals I'd guess it was set up for the same 36.3 psi base fuel pressure.

Steve

Oh I see. I just want to clear some things in my mind. Here are some scenarios, please comment.

The 1G uses 450cc injectors and base fuel pressure is set at 36.3 psi. The E931 compensation code for 450cc is 4A hex.

The Evo 3 uses 510cc injectors. I don’t know what its base fuel pressure. The Evo 3 ECU compensation code for 510cc is 3E hex. 3E hex is actually for 530cc. But why did it use a comp code 3E hex/530cc for 510 injectors? Is it because it uses a higher base fuel pressure? Does this mean base fuel pressure is at 40psi?

The 2G DSM usees 450cc injectors and base fuel pressure is at 42psi. I haven’t seen the 2G ECU code. But I assume it is for 479cc or 45 hex.

Is the reason for Mitsubishi bumping the fuel pressure from 36.3psi to 40- 42psi on later models is to make the injectors bigger?

Alvin

 

[steve]

You can't directly compare fuel the globals from one version of the software to another without first correcting for fuel pressure and making sure that both software use the same fuel calculations.

450cc injectors deliver 450cc @ 43.5 psi at 36.3 psi they work like 411cc injectors.

Steve

 

[timloomis]

I may be having a problem with mine also.I have the 180lph 3kgtvr4 pump and when the car is cold,it bucks and jerks violently.Like I'll floor it,it takes a second,then spins the tires.Runs better once its warm,but you can feel it jerk with the cruise on at 65 mph.Sound like fpr overrun?

 

[steve]

I may be having a problem with mine also.I have the 180lph 3kgtvr4 pump and when the car is cold,it bucks and jerks violently.Like I'll floor it,it takes a second,then spins the tires.Runs better once its warm,but you can feel it jerk with the cruise on at 65 mph.Sound like fpr overrun?

WTH does that have to do with this thread?

Steve

 

[timloomis]

lessismore said something about bumping up his fuel pressure with the nt unit.I did the same but I dont have a fuel pressure gauge,so I dont know if Im getting 54 psi like he is.If thats the case,then bumping up fuel pressure with the nt fpr with an aftermarket pump overruns it just like the 255 on the stock turbo fpr.

 

[a73_4g67]

I see. Then its more efficient to bump the pressure and compensate by changing the global value. That if you have a 255 pump. I think the evo 3 code is pretty similar with the E952. Having a global value that is not exact for the injector size could mean its using a higher base pressure. Its just a thought, there could be another reason why its leaned out by the global value. The E952s orig injector size(510cc) is the same as the Evo 3, but they differ by 20cc from the global value. Even Jeff O wonders what base pressure is the EVo 3 using because of the 3E global value. Even the E952 deadtime map is almost identical to the evo . I'll ask the Evo boys at New Zealand, Australia for the base fuel pressure, so we can compare.

Steve, are you using 3B hex for your 560cc and set at 36.3 base fuel pressure?

You can't directly compare fuel the globals from one version of the software to another without first correcting for fuel pressure and making sure that both software use the same fuel calculations.

450cc injectors deliver 450cc @ 43.5 psi at 36.3 psi they work like 411cc injectors.

Steve

 

[steve]

Steve, are you using 3B hex for your 560cc and set at 36.3 base fuel pressure?

Yes, I'm running real EVO VIII four hole 560cc injectors using a global of 3B and -48uS deadtimes (2 subtracted from the stock map). The low fuel trim at 750 RPM still drops to about 96% but the mid and high are just over 100% but -72uS causes the car to run poorly at idle and any more deadtime cause the low trim to bottom out.

Steve

 

[a73_4g67]

Steve,

New discovery! I just backtracked the archives. The 2G injector Global is 45 hex. Just like what I assumed. 45 hex is 479cc.

The 1G is using 4A hex for 450cc. It means, 36.3 psi will flow 450cc base on the ECU code. By using the RCeng formula, old pressure is 37 and new pressure is 42psi, from 450cc, it will become 479cc or 45 hex for the global value. It all makes sense. Mistubishi bumped the pressure to make the injectors bigger. Now, if you're going to upgrade to 550cc injectors in a 2G, I just learned that one guy used 600cc compensation code or 38 Hex. Now if you'll going to apply RCEng formula again, 37psi to 42psi on 550s, you will have a new value of 585cc. 585 to 600cc, the global value is 38 hex. Now I wonder about the rumor of the 560cc flowing like 600cc is because its used at 42psi or for a 2G DSM. In case I will reach 80%+ duty cycle, I'm going to bump the pressure to 42psi and change the global value to 38 hex for 600cc.

This means, the global value is based on the fuel pressure and it doesnt matter on ECU versions.

Now its getting clear that the Evo 3 fuel pressure is around 40psi.

Alvin.

 

[a73_4g67]

Steve, thats the same deadtime map I'm using. -2 from the stock E931 deadtime map. The car runs and idles good. I cant check the fuel trims because the E952 has a different address for the fuel trims. The part number of my Evo 6 Tomi Makinen Injectors is the same as the Evo 8 or 9. I guess we have the same injectors.

Yes, I'm running real EVO VIII four hole 560cc injectors using a global of 3B and -48uS deadtimes (2 subtracted from the stock map). The low fuel trim at 750 RPM still drops to about 96% but the mid and high are just over 100% but -72uS causes the car to run poorly at idle and any more deadtime cause the low trim to bottom out.

Steve

 

[steve]

Most injectors are rated at 3bar (43.5 psi). So like I said before, the 450cc injectors work out to 411cc @ 36.3 psi. That's about what a global of 4A equals.

560cc injectors @ 36.3 act like 511/512cc and work out to a 3B global.

If you up the pressure to 43.5psi the 450s deliver 450cc and use a 44 or 45 global and the 560s a 36 global.

If you go look in the dsm-ecu archives you see where the settings came from so there's no surprise at to why what your using is the same as mine

Steve