At what pressure will injectors still atomize fuel well?

[linksys42]

Originally Posted by Taboo;

Reset the ECU to start with (in order to get rid of your messed-up trims and load fresh timing maps), reset the ISC servo, pressure-test the intake, make sure the TB plate is all the way closed at idle and all the way open at WOT, adjust the TPS, and set the BISS 2.5 turns out. Set the S-AFC to 0 or slightly bellow across the entire board and use NOTHING but the AFPR to get within the ECU adjustment range (= do not touch the S-AFC AT ALL. Just pretend it's not even there). The trims do NOT have to be exactly 0%. Adjust the idle with the BISS. All there's to it. Use just and only the AFPR to establish the rough fuel curve and the S-AFC to supply the ECU with the correct airflow. Because of the hacked MAS (or different turbo response - in case of someone with an aftermarket turbo) the "correct" airflow the ECU expects to see is not going to form a straight line on the S-AFC and does not really mater where the curve on the S-AFC is located as long as the ECU is supplied with the "correct" airflow values. One can and will use the S-AFC to fine tune the fuel curve (once it's established with the AFPR), but there's going to be never ending compromise between manipulating the actual AFR and affecting the timing in the process by feeding the ECU by "incorrect" airflow values. There are just two simple things you have to do: 1) establish the correct airflow values with the S-AFC and 2) establish the fuel curve with the A-FPR while staying within the adjustment range of the ECU. If you do that, your car is roughly tuned and you can continue fine-tuning it with the AFPR and the S-AFC in order to improve the throttle response, get rid of knock caused by incorrect AFR or timing at particular RPM range and airflow, etc. Don't be obssessed with 0% trims and 0 knock. Lean the bitch out (with the AFPR) as much as you can at WOT 'til she starts dropping timing, then go a notch back up with the fuel pressure. However, you can do that only after the LTFT is established.

I was wondering if this approach to tuning would be fine with 650’s? Because to get the O2’s to cycle I would think you would be pretty low in the fuel pressure with the AFC zeroed out with the 650’s. What I am wondering is how low of fuel pressure is to low? At what pressure will injectors still atomize fuel well? Because at 30 psi of base fuel pressure you should be able to flow the 650’s at about 448cc. And at 37psi of base pressure I should be able to run the injectors at 552cc. Correct me if Im wrong. Just wondering how low of fuel pressure is safe when tuning with an AFPR. Thanks

[GVR4592]

What's the point? You're going to install 650cc injectors only to turn the fuel pressure down so they flow 450cc's. The ecu won't know the difference, but you won't be gaining any more fuel flow capacity.

[linksys42]

Originally Posted by GVR4592

What's the point? You're going to install 650cc injectors only to turn the fuel pressure down so they flow 450cc's. The ecu won't know the difference, but you won't be gaining any more fuel flow capacity.

The idea is to lower it down to get a base tune where the ecu is at its stock timing and fuel maps. Running stock boost to get a good base line then bump the boost up a psi or two than bump the fuel pressure and make minor adjustments with the safc to dial in the tune and keep repeating the process till you reach the boost pressure that you are shooting for. That way you are at the lowest map for the timing and fuel so you don’t have to take so much out with just the afc. I have been having problem with knock and I am guessing it is because of the high timing from the afc that’s why I am trying to get it closer to the stock maps. The thing is that I cannot lean the car out? With the 650’s in and the fuel pressure at 43.5 I am only able to pull out –22 to –23 without it knocking on my high throttle settings. And that is with my wide band pegged at below 10.0:1 that’s all my AEM uego will read on the gage. I have tried to lean it out more but the knock keeps going up and up. Any suggestions would be great. Also what could be the draw back to running the fuel pressure at a lower number, I know it wont atomize as well as if it were at 43.5psi the pressure rating that the injector was designed to run at. But will it hurt anything?

[2gGSX]

After a certain point, it will start to run into problems (esp. early into the pull, assuming you go crazy low). No one can say for sure when the atomization becomes an issue unless they experimented and found out.

In essence, you're running into the limitations of a SAFC setup is all. Read through this thread if you don't believe me-- New log with PTE 54 trim (3227e) - join the tuning!

The gist of it is that you'll have to somehow get enough airflow to keep yourself in the upper timing map, while at the same time trying not to pull too much airflow which would knock you back down to a lower timing map.

[linksys42]

Originally Posted by 2gGSX

After a certain point, it will start to run into problems (esp. early into the pull, assuming you go crazy low). No one can say for sure when the atomization becomes an issue unless they experimented and found out.

In essence, you're running into the limitations of a SAFC setup is all. Read through this thread if you don't believe me-- New log with PTE 54 trim (3227e) - join the tuning!

The gist of it is that you'll have to somehow get enough airflow to keep yourself in the upper timing map, while at the same time trying not to pull too much airflow which would knock you back down to a lower timing map.

Ya, I understand the timing tables from the airflow that the ecu sees. But what I don’t understand is why when I turn the boost up to 20psi or 1.7 g/rev that the ecu sees after the afc corrects it, I am on the timing table of a peak of 19-22 degrees. But I can only lean the afc to about –22 to –23 when others have been able to lean it out to at least –31 or farther?

[2gGSX]

Perhaps they have higher airflow than what you're getting. If they're pulling more airflow than you and staying on the same load table (or an even higher one), then they've got to be moving more air than you.

[turboglenn]

Originally Posted by linksys42

Ya, I understand the timing tables from the airflow that the ecu sees. But what I don’t understand is why when I turn the boost up to 20psi or 1.7 g/rev that the ecu sees after the afc corrects it, I am on the timing table of a peak of 19-22 degrees. But I can only lean the afc to about –22 to –23 when others have been able to lean it out to at least –31 or farther?

Hate to say it, but simply every car and motor setup will require slightly to marginally different maps/tuning even with all the same parts. Can't you just dial down teh LOW throttle areas at idle and then have the HI settings for WOT set safely still? I only ran 550's on my AFC, then i stepped up to stand alone fuel management because of teh ill effects of pulling too much air from what teh ECU could see. ( i did love the S-AFC though, it was fun for a year or 2 )

[linksys42]

Originally Posted by 2gGSX

Perhaps they have higher airflow than what you're getting. If they're pulling more airflow than you and staying on the same load table (or an even higher one), then they've got to be moving more air than you.

ya i wish that was it but they were runing only 17-19 psi and the exact same set up but pulling -30's out of the afc? i dont get it. the only explanation i can think of is like turboglen is saying that every set up is different. but i really dont think that it would be that much of a difference? I dont get it? Was also wondering what you think crazy low fuel pressure would be?

Originally Posted by turboglenn

Hate to say it, but simply every car and motor setup will require slightly to marginally different maps/tuning even with all the same parts. Can't you just dial down teh LOW throttle areas at idle and then have the HI settings for WOT set safely still? I only ran 550's on my AFC, then i stepped up to stand alone fuel management because of teh ill effects of pulling too much air from what teh ECU could see. ( i did love the S-AFC though, it was fun for a year or 2 )

Your right about all cars tunes being different, but I thought that I would be remotely close to being able to pull out enough fuel to get close to 11.1:1 a/f ratio at least? Thanks for all the help opinions guys.

[2gGSX]

The difference in airflow could be due to having a setup with greater VE, and thus more airflow at the same boost. OR, they could have the same setup as you, but not care about running high timing on pump gas. If you can pull -30% air and get dropped to a lower load timing map, yet still run without getting knock, then there's not much to worry about.

If you can stay above at least 1.8 g/rev, then your ECU would shoot for 19 degrees peak timing. That's *somewhat* doable (I say somewhat because a lot of people go for high boost low timing), although you may have to look into adding some E85 or some sort of injection to do it.

The lowest fuel pressure that I've seen anyone run on a regular basis is 32 psi. The car also has 1600cc injectors, runs on straight E85, and has 280* cams--not exactly a street car. He does drive the car around town and comments on poor street manners, but that's due to any number of things.

[linksys42]

Originally Posted by 2gGSX

The difference in airflow could be due to having a setup with greater VE, and thus more airflow at the same boost. OR, they could have the same setup as you, but not care about running high timing on pump gas. If you can pull -30% air and get dropped to a lower load timing map, yet still run without getting knock, then there's not much to worry about.

If you can stay above at least 1.8 g/rev, then your ECU would shoot for 19 degrees peak timing. That's *somewhat* doable (I say somewhat because a lot of people go for high boost low timing), although you may have to look into adding some E85 or some sort of injection to do it.

The lowest fuel pressure that I've seen anyone run on a regular basis is 32 psi. The car also has 1600cc injectors, runs on straight E85, and has 280* cams--not exactly a street car. He does drive the car around town and comments on poor street manners, but that's due to any number of things.

Ya now that I am having problems with this I wish I would have went with the ball bearing 5031re. But hindsight is 20/20. I was going to order engine runup water/meth kit soon here. Looks like really soon. I have done some reading on e85 and I can get it here im my town and its really cheap! I can also get 103 octane at the pump here also but it’s like 5.00 dollars a gallon! What exactly do I need to convert too to run e85? Or can I just run it with no ill effects? I would think that ethanol would be corrosive to certain fuel supply parts? And can the e85 be mixed with 93 to a mixture of like 2 to 1? How are people mixing it or what ratio do people run to get good results? Thanks again for all the help!

[2gGSX]

Originally Posted by linksys42

Ya now that I am having problems with this I wish I would have went with the ball bearing 5031re. But hindsight is 20/20. I was going to order engine runup water/meth kit soon here. Looks like really soon. I have done some reading on e85 and I can get it here im my town and its really cheap! I can also get 103 octane at the pump here also but it’s like 5.00 dollars a gallon! What exactly do I need to convert too to run e85? Or can I just run it with no ill effects? I would think that ethanol would be corrosive to certain fuel supply parts? And can the e85 be mixed with 93 to a mixture of like 2 to 1? How are people mixing it or what ratio do people run to get good results? Thanks again for all the help!

Lots of people have been running E85 without any issues on the stock lines/rail/etc. The only thing that I would really worry about would be the fuel pumps, as that would probably be the first to fail. There's a list somewhere of E85 compatible fuel pumps, but I do know that the common Walbro pumps as well as the Supra pump are all E85 compatible.

People do mix E85 with pump gas, you just have to tune for it. The exact ratio is up to you, as there isn't really a "recommended" ratio as far as I know.

The real issue with running big power on E85 is that it puts huge demands on your fuel system, especially your fuel pump(s). Colloquial reports say that you need 30% more fuel when running E85 than with pump gas.

I've got some preliminary estimations, but with E85 being really out of the way for me, I haven't had a chance to really test it out. I'll send it to you via a PM though.

[matthewdesigns]

Try searching threads on Colorado DSM Club Forums - Powered by vBulletin and Rocky Mountain DSM Forums - Rocky Mountain DSM . There are a number of guys here in Colorado running straight and/or mixed E85. There's a thread on the first site where members list their setups. Here ya go: Post your E85 setup - Colorado DSM Club Forums

30% more fuel, a 255 Wally w/AFPR, and at least 850cc injectors are the bottom end of what's required by most people running it around here. Oh, and Link or some other standalone for fuel management (not an AFC...).

Edit - I've played around with mixing it with pump 91, but my IDC's are already borderline with the amount of boost I'm running, so I typically throw fuel trim CEL's when I mix it in, even with an AFC. And I'm not going to give up any psi

[linksys42]

Originally Posted by 2gGSX

Lots of people have been running E85 without any issues on the stock lines/rail/etc. The only thing that I would really worry about would be the fuel pumps, as that would probably be the first to fail. There's a list somewhere of E85 compatible fuel pumps, but I do know that the common Walbro pumps as well as the Supra pump are all E85 compatible.

People do mix E85 with pump gas, you just have to tune for it. The exact ratio is up to you, as there isn't really a "recommended" ratio as far as I know.

The real issue with running big power on E85 is that it puts huge demands on your fuel system, especially your fuel pump(s). Colloquial reports say that you need 30% more fuel when running E85 than with pump gas.

I've got some preliminary estimations, but with E85 being really out of the way for me, I haven't had a chance to really test it out. I'll send it to you via a PM though.

I am running a walbro 190L with the 650’s afpr and big 16g so with a 30% more demand I would only be able to run safely at about 15-16 psi correct? If so, if I watered down the e85 with 93 say a 50/50 mix I should be able lessen the demand of 30% more fuel to around 15% so I can at least run 18psi and be able to lean it out to around 11.0:1 to 12.0:1. And when tuning i should just aim for that a/f ratio with 0-3 counts across the band. If you have any other recommendations let me know I really appreciate it.

[matthewdesigns]

Originally Posted by linksys42

I am running a walbro 190L with the 650’s afpr and big 16g so with a 30% more demand I would only be able to run safely at about 15-16 psi correct?

I would say that is about right, as I figured 14-15psi on my car (rewired190/550's/E316g).

Originally Posted by linksys42

If so, if I watered down the e85 with 93 say a 50/50 mix I should be able lessen the demand of 30% more fuel to around 15% so I can at least run 18psi and be able to lean it out to around 11.0:1 to 12.0:1. And when tuning i should just aim for that a/f ratio with 0-3 counts across the band. If you have any other recommendations let me know I really appreciate it.

That's too much for me I only have a shallow knowledge of how these things interact...I don't want to tell you the wrong thing!

Go check out those forums I linked to, and read up a bit, as there's been a lot of discussion regarding E85 on those boards this year. And join and ask questions, especially co.dsm.org...lots of friendly knowledge there. There are also a couple of threads here on Tuners about E85 that are fairly informative.

[2gGSX]

I shot you a PM that should answer those questions, although it's all based on some theory. In essence, fuel flow demands increase proportionately to airflow increase. It's not so much how much boost you can run, but how much air you're trying to flow.

Lower airflow numbers will allow you to run more E85 with the same injector flow requirements--using the numbers from the PM I sent you: given 600 cc/min of usable flow (92% IDC), with 45 lbs/min of air you'd only be able to run 1 or 2 gallons of E85, whereas with 40 lbs/min you'd be able to run 10 gallons.

Edit: I thought you had a 54 trim for some unknown reason. In this case, you should be fine as a typical 16g setup on a relatively stock motor averages around 35 lbs/min.

[GVR4592]

Can you post a datalog, along with the boost setting, fuel pressure, any wideband data you have, and safc settings for that particular datalog.

[linksys42]

Originally Posted by GVR4592

Can you post a datalog, along with the boost setting, fuel pressure, any wideband data you have, and safc settings for that particular datalog.

I don’t get why when I post the html code it puts this long space in? Any way you need to scroll down to see the log. Its at 19-20 psi, fuel 43.5 psi, flowing 30.6 lbs/min, 2.1 g/rev. Hi settings on this log are -22 all the way across didn’t fine tune it just plugged them all in quick. Wide band is off the chart pig rich all the way thru the run. the 0-5 signal wire off the wide band is spliced into the 2nd o2 sensor pinout on the ecu.These are 650's. Thanks

 
 
 
 
 
 
 
 
 
 

  
TPS
  
RPM
  
TimingAdv
  
AirFlow
  
O2Sensor
  
O2Sensor2
  
AirTemp
  
InjDutyCycle
  
KnockSum
 
 

  
22.745098
  
2656.25
  
33
  
100.64
  
0.0975
  
2.457
  
79.20592
  
3.966666667
  
0
 
 

  
33.7254902
  
2656.25
  
31
  
163.54
  
0.0975
  
2.6325
  
79.20592
  
6.8
  
0
 
 

  
63.5294118
  
2750
  
27
  
276.76
  
0.8775
  
2.3595
  
79.20592
  
10.56
  
0
 
 

  
80
  
2687.5
  
27
  
276.76
  
0.7605
  
2.2425
  
78.41055
  
10.32
  
0
 
 

  
100
  
2750
  
28
  
283.05
  
0.0975
  
1.7355
  
78.41055
  
10.56
  
0
 
 

  
100
  
2781.25
  
27
  
295.63
  
0.0585
  
2.808
  
78.41055
  
11.27333333
  
0
 
 

  
100
  
2812.5
  
27
  
314.5
  
0.117