ECMlink 1G Should I increase fuel pressure or do I need bigger injectors?

[Vegas Smith]

Is your fuel pressure really set to 37psi................................................................

 

[AWD-Tony]

No. 43.5 Why do you think its at 37?

 

[AWD-Tony]

Are you trolling me vegas?

 

[Vegas Smith]

I've explained this to you 5 times.

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[AWD-Tony]

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[AWD-Tony]

That's so weird??

 

[Vegas Smith]

Yeah not sure what's going on here.

 

[AWD-Tony]

Has to be glitch in the matrix

 

[steve]

Yeah not sure what's going on here.

I just downloaded the Log and see the same thing as you but as pointed out it's the same correction as 550cc @ 43.5 psi

DSMLink only uses the correction % but the calculator knows that a 1G factory base fuel pressure is 37 psi and the stock injectors are 450cc so it's calculating the injector size using those constants.

 

[AWD-Tony]

Strange!! Guess we can't go by what we see in logs as far as fuel injector calculations go.

 

[kmetiuk]

Strange!! Guess we can't go by what we see in logs as far as fuel injector calculations go.

As we are measuring both fuel and air we can check the fuel flow from the air side instead of by the injector width which DSMLink is using for the IDC calc i believe.

So, I did the calc going from the AFRest of 11:1 and used the the linwideband of 10.8:1 that matched close enough and using the airflow of 37.8 I get:

38.7 (lb/min of Air)
/ 10.9:1 (Air/fuel)
= 3.5504 (lb/min fuel)
/ 2.2 (lbs/kg)
= 1.613 (kg/min of fuel)
/ 0.745 (kg/L - density of gasoline-ish)
= 2.166 (L/min of fuel)

Orrrr rather 2166 cc/min of fuel flow based on the math and your linear wideband data from the log. So from that you are at 98.4% IDC's vs Links 93.4%.

That's all assuming that your O2 is calibrated and that the density of your fuel is 0.745kg/L but if its got XX% ethanol then that changes things a bit. By using the point where 10.9 crosses the AFRest of 11:1 it should make the airflow of 38.7lb/min pretty damn close so I'd say your on the edge of the injectors.




So I'm confused in the end....whats the issue with running more pressure on the 550's? Whats wrong with running a few more fuel psi to eek out the last bits of power on his setup?

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[AWD-Tony]

That's a lot of math there and you definitely know more than me. When I posted this, there were times when IDC would reach high 90% and I wasn't sure what numbers were safe for bfp and IDC. Once I bumped the pressure to 43.5 and started dialing in MAF, it's more in the 80s now. I'm guessing I can bump the fuel pressure to 50bfp (max???), if I need to. Will probably need injectors if I decide to increase boost. Car is still running rich though. Log is from today with a little knock up top. Would you say next thing I need to dial in injector slider?

 

[AWD-Tony]

Do you know how accurate HP and torque numbers are in link? And that's estimated at the crank correct?

 

[AWD-Tony]

I just downloaded the Log and see the same thing as you but as pointed out it's the same correction as 550cc @ 43.5 psi

DSMLink only uses the correction % but the calculator knows that a 1G factory base fuel pressure is 37 psi and the stock injectors are 450cc so it's calculating the injector size using those constants.

Correction percentage??? Is that what global is?

 

[kmetiuk]

Once I bumped the pressure to 43.5 and started dialing in MAF, it's more in the 80s now. I'm guessing I can bump the fuel pressure to 50bfp (max???)

Here's how I understand it ....you can bump up base pressure to whatever you want (within reason of course) as long as:
- the pump can support it
- and you are still getting a decent spray at low flows (such as idle and cruise)

The issue with lowering your fuel pressure for big injectors is that you start to mess with the spray pattern...it just doesn't have enough ompf to amtomize the fuel. But with jacking the pressure up you are really only limited by what your pump can deliver. You can start to run into an issue where the pulse width gets so low at idle/crusie that you have the same issues the big injector guys have where its just to short of a pulse width to disperse properly.

With respect to IDC's and base pressure....IDC's are purely electrical. I mean they're not, there is a lot going on clearly, but I mean we really only care about the IDC's electrically. When you start to send 90, 95, 100% electrical signals to anything it starts to get hot. If you jack the base pressure up, the ECU will just shorten the electrical signal to the injector, lowering the IDC's, and also lowering the heat its generating.

Basically, the injector doesn't care pressure wise....it can take a lot. BUT it can get messed up if you push 100% electricity though it for 4-5 minutes at a time and it doesn't like to run at 0.001% IDC's at idle.

Guys run 40-45 lbs of boost on a base of 40 or 45 psi.....so say 90 psi....and u run 25psi (ish) so you could likely run a base pressure of 65 psi and the injectors will be fine....BUT can your pump support that? You'll need to check your pump curve.

What you really want is the lowest base pressure you can run, while maintaining a good idle pulse width and low IDC's. If you can get 80% IDC on 45 BFP I would say that's totally reasonable and I'd personally rock that. Can you run 50? Prolly. Can you run 60? Maybe but I'd start to wonder about the low end.

Do you know how accurate HP and torque numbers are in link? And that's estimated at the crank correct?

Couldn't say. I have heard it is close if you dial in the weight and gearing for your wheel size, but I have always found it to lag behind where the boost is hitting so I think there is some kinda lag there or something due to the calculation its doing? I dunno, but it is good for saying a change timing at cell XX to 17* netted an increase in TQ and that's about it. It will tell you "yes, you made more power" but wont say "you are making exatcly XX more hp".

Basically confirms if the change u just made is actually making more power/tq but not how much more/less.

Would you say next thing I need to dial in injector slider?

Nah man, I never use the slider ever. Use the MAF comp tab only. Also if you have the deadtimes input that in the direct access in the INJBATTERYADJ tab that would be make it alot smoother AFR's during cruising/idle.

You AFR vs AFREst doesn't look bad at all. Could use a lil work at the 0-50HZ and maybe the 100 HZ slider but the WOT looks pretty damn good.

 

[steve]

Correction percentage??? Is that what global is?

Yes. That's what the calculator does, figure the difference between the stock fueling and your setup. So your 550's @ 43.5 psi are 24.6% larger than the factory 450's @ 37 psi in flow rate. If this was a 2G ECU the global would be different for the same injectors because of the higher factory base fuel pressure.