550's EvoIII 16g Fuel pressure?

[New2tuning]

If anyone is running an EvoIII 16g, 550's, 2G MAF, 255 fp I was wondering what fuel pressure your running. Im running 43psi (hose off) atm but I am outflowing my injectors at just 18 lbs of boost, m high throttle settings are in the upper 20 to lower 30s and still getting some fuel cut style stutters at the track. Im curious what the max psi I can set my AFPR at is so that I dont go too far when adjusting the pressure.

 

[andymoraitis]

I know this isn't the answer you're looking for, but the 550's are really undermatched to the EVO III. I would sell them and install some 650's. In the interim, you can try 45psi and see if that lower IDC's as it should, but in the long run, you'll need the larger injectors to get your IDC's where they should be.

Good luck!

Andy

 

[Boiler2]

I agree with what was already replied above. That is the right way to go. However, I have had the setup you list and had the same problem. I do have the supra pump though and ran 47 psi (2G) with no issues. As long as your fuel system and injectors can handle the extra few psi, it should not be too bad. I discussed it with RC Engineering beforehand. In a simplified way, it makes the 550's "act" like larger injectors.

 

[240kid]

47?!?! try 40ish

 

[New2tuning]

47?!?! try 40ish

43 is what should be run stock. I have it at 50 right now and not having the problem.

 

[ITSME4G63]

43 is what should be run stock. I have it at 50 right now and not having the problem.

this guy has a 1g, base fuel pressure is like 37.5, on 2g's its 43. So you say 550's dont do a 16g justice or just an evo16g? Im modded jus tliek this guy is , 2g maf, 550's, small16g, and a afpr, in my case though, I think its getting too much fuel, WHen I smash the throttle, the car just kind of hesitates into the higher rpms, but when I push it half way it just moves along without problems. I dunno, gonna have to throw the logger on it and a wideband in the pipe.

 

[GVR4592]

550's are too small for any 16g if you want to use the turbo to it's full potential.

 

[v2ner]

That all depends on what octane you're running. 93 octane with 550ccs shouldn't be pushed pass 18psi. Now, with 110 octane+ and 550ccs you can definitely max out an EVO III or 16G (28psi....then falls a couple in high RPM).

 

[Stapl3]

43 for 2g, 37 for 1g.

I remember back in the day when 550's were plenty for 20g's. Back when people didn't overkill.

 

[Generation X]

43 for 2g, 37 for 1g.

I remember back in the day when 550's were plenty for 20g's. Back when people didn't overkill.

Amen to that!! I run RC 550's with my ported FP B28 @ 22psi, while spraying a Zex 75 wet shot on pump 93. I also run the HKS 264/272 cam combo, and I get about 17 to 18 degrees of timing on third gear pulls on spray. I do have a afpr but I leave it at the stock 43.5psi.

 

[v2ner]

A little off topic but hey Generation X, may I ask why you spray in 3rd? Wouldn't it benefit even more to spray in forth if you're behind? Just curious.

 

[daren_p]

In your origional post are you adding fuel or takeing away? If you are adding 20-30% fuel , thats why your getting fuel cut & running out of fuel. As for outrunning 550's on an evoIII at only 18 psi, that seems like a pretty low amount of boost to be doing so. What fuel are you running & what are you using to tune? With my 750's I see about 65% IDC at 18 psi on my evoIII. I would think with a good tune you would be in the 85-90% IDC with the 550's (which isn't the best idea to run this high, but their not completely "maxed" out).

 

[v2ner]

For 93, anything after 18psi is pushing it unless you have meth/alky.

 

[Generation X]

A little off topic but hey Generation X, may I ask why you spray in 3rd? Wouldn't it benefit even more to spray in forth if you're behind? Just curious.

The only time that I spray in 3rd is if I'm logging a run with my logger. I usually spray in 2nd if I'm racing, and keep on spraying through the rest of the gears if necassary.

That's why I said in my earlier post that I get about 17 to 18 degrees of timeing at the top of third gear. That's only when I'm logging a run. I don't have time to look at a logger while I'm running through the gears on nitrous.

 

[Caithness]

Are you running aftermarket cams?

We've got my buddy's Evo 16g car running 21 psi on 93 octane with an 11:1 AFR and it sits right at 85-90% IDC. I've read some interesting threads recently that lead me to believe the 80% IDC cap is way too conservative for modern injection systems, and some newer cars run injectors all the way up to 95%. I know we were running his car at low 90's before we leaned it out a bit.

Anyway, we're doing that on 450cc injectors, with a non-turbo FPR pushing base fuel pressure to 47.6 psi. It basically works out that they're flowing ~20cc/min less than 550cc injectors on 36 psi base. Even with aftermarket cams, 550's should be more than enough if you push the base fuel pressure to the 48-50 psi range, which is perfectly fine on a smaller turbo which has lower flow demands and lower boost pressure, keeping the fuel pressure below the 75-80 psi range where pump flow falls off. Unless you're tuned really rich, you should have no problem maxxing an Evo 16g on those injectors.

 

[Generation X]

Are you running aftermarket cams?

We've got my buddy's Evo 16g car running 21 psi on 93 octane with an 11:1 AFR and it sits right at 85-90% IDC. I've read some interesting threads recently that lead me to believe the 80% IDC cap is way too conservative for modern injection systems, and some newer cars run injectors all the way up to 95%. I know we were running his car at low 90's before we leaned it out a bit.

Anyway, we're doing that on 450cc injectors, with a non-turbo FPR pushing base fuel pressure to 47.6 psi. It basically works out that they're flowing ~20cc/min less than 550cc injectors on 36 psi base. Even with aftermarket cams, 550's should be more than enough if you push the base fuel pressure to the 48-50 psi range, which is perfectly fine on a smaller turbo which has lower flow demands and lower boost pressure, keeping the fuel pressure below the 75-80 psi range where pump flow falls off. Unless you're tuned really rich, you should have no problem maxxing an Evo 16g on those injectors.

Yeah I'm running the HKS 264/272 combo. They seem to compliment the FP B28 very well.

And yes I agree with you about the IDC's. Hell... theres a guy on the boards that goes by THEDUKE and has run 11's with the stock 450's. Here's a link to his profile. http://dsmtuners.com/forums/member.php?&do=vehicledetails&userid=12315

Anyways, I actually run 20 psi off nitrous, and then when I spray it hits 22 psi. So far I have been getting pretty good timing with my set up. If needed I can always bump my fuel pressure up a little with my AFPR.

 

[2gGSX]

I know I'm a little late, but I'd propose that someone with 550's, a big fuel pump and an AFPR would have no problems supporting any 16g. Before you start flaming, remember what some people have said:

43 is what should be run stock. I have it at 50 right now and not having the problem.

I agree with what was already replied above. That is the right way to go. However, I have had the setup you list and had the same problem. I do have the supra pump though and ran 47 psi (2G) with no issues. As long as your fuel system and injectors can handle the extra few psi, it should not be too bad. I discussed it with RC Engineering beforehand. In a simplified way, it makes the 550's "act" like larger injectors.

In the first case, his injectors are effectively running similarly to 600cc injectors--550(50/43)^.5=600, and in the second 575cc--550(47/43)^.5

Both give enough overhead to keep IDCs lower. In any case, a set of 550's will flow 3.68 lbs/min of fuel at 100% IDC and 3.31 at 90%. In any case, with an 11:1 tune that equates to support for 36 lbs/min of airflow. I'd postulate that the average Evo III owners will be around that area (meaning not the freaks that flow 45 lbs/min )

Basically, for the people with 550's, an AFPR and a beefy fuel pump you will be fine keeping those injectors. If IDCs start getting higher than you'd like, bump up your base fuel pressure while staying within the limits of your fuel pump.

 

[Generation X]

I know I'm a little late, but I'd propose that someone with 550's, a big fuel pump and an AFPR would have no problems supporting any 16g. Before you start flaming, remember what some people have said:


In the first case, his injectors are effectively running similarly to 600cc injectors--550(50/43)^.5=600, and in the second 575cc--550(47/43)^.5

Both give enough overhead to keep IDCs lower. In any case, a set of 550's will flow 3.68 lbs/min of fuel at 100% IDC and 3.31 at 90%. In any case, with an 11:1 tune that equates to support for 36 lbs/min of airflow. I'd postulate that the average Evo III owners will be around that area (meaning not the freaks that flow 45 lbs/min )

Basically, for the people with 550's, an AFPR and a beefy fuel pump you will be fine keeping those injectors. If IDCs start getting higher than you'd like, bump up your base fuel pressure while staying within the limits of your fuel pump.

Agreed!!

 

[GVR4592]

Both give enough overhead to keep IDCs lower. In any case, a set of 550's will flow 3.68 lbs/min of fuel at 100% IDC and 3.31 at 90%. In any case, with an 11:1 tune that equates to support for 36 lbs/min of airflow. I'd postulate that the average Evo III owners will be around that area (meaning not the freaks that flow 45 lbs/min )

I had a walbro 255hp, Rc 550's, Evo 3 16g 10.8:1 A/f and I maxed the injectors out at 24 psi with stock fuel pressure. I increased the pressure to 50 psi and I was only able to get another 2 psi of boost before I maxed the injectors again. I was flowing 41 lbs/min on 92 octane. With race fuel it would have been a lot better. That's how you see people with 20g's running 550's and guys with 450s in the 11's, you can't run those lean a/f ratio's with pump gas. Pump fuel and high boost means you have to run it fairly rich to keep the knock down.

 

[2gGSX]

(Cliffs notes at bottom)

This is completely for argument's sake (and to get out of studying for bio), but--

Formula 1
Using a regression to calculate the flow characteristics of a fuel pump at certain fuel pressures I estimated that the function f(x)=255.4753/(1+.00000013255e^(.19221x)) gives an accurate answer with an alpha-level of .006% in the area of question (73-88 psi fuel pressure).

Formula 2
The function f(x)=(x/43)^.5 x 550 x .76 x 4 / 454 = (41/.9)/10.8 allows you to determine base fuel pressure needed to run your injectors at an estimated 90% IDC at 10.8:1 AFR and 41 lbs/min airflow.

Thus, if you solve for function 2 you get 56.4 psi base fuel pressure necessary to achieve the above conditions. HOWEVER, if you then plug that number + 26(boost pressure) (total is 82) into function 1 you get 132.53. If you do some quick math (41 / 10.8 x 454 /.76) you get 136, which is your fuel requirement from the pump in LPH. Thus, your fuel pump would not be able to keep up and you'd get screwed regardless!

The moral of the story is, it can still be done, but like I said under the conditions that you
1. Aren't hitting crazy numbers (like 41 lbs/min)
2. You're using AT LEAST 93 octane (I just realized all those calculations have been using .76 as spec gravity of fuel, which isn't the correct value for 92 octane d'oh)
3. Have an enormous fuel pump (capable of flowing high numbers at ludicrous fuel pressures, like 80+)
4. Have a fuel system capable of not exploding with that much fuel pressure

But this is all just bench racing in the end, and I agree with you that once you start hitting huge airflow numbers from an Evo III (such as the 41 lbs/min above), there's no way you would have just read all that crap above and should upgrade to bigger injectors anyways!

One final comment--running 40 lbs/min airflow on pump gas (92 at that) is already very impressive, especially on 550's

Cliffs notes: You can make do with 550's at moderate airflow (around 35 lbs/min) and even at high airflow (over 40) with an enormous fuel pump, but why bother? And, I'm a big loser who doesn't want to study.

 

[Generation X]

I had a walbro 255hp, Rc 550's, Evo 3 16g 10.8:1 A/f and I maxed the injectors out at 24 psi with stock fuel pressure. I increased the pressure to 50 psi and I was only able to get another 2 psi of boost before I maxed the injectors again. I was flowing 41 lbs/min on 92 octane. With race fuel it would have been a lot better. That's how you see people with 20g's running 550's and guys with 450s in the 11's, you can't run those lean a/f ratio's with pump gas. Pump fuel and high boost means you have to run it fairly rich to keep the knock down.

That's still pretty damn good bro, running 24psi on pump gas with stock fuel pressure, and even better @ 26psi with a bump in fuel pressure, especially on a Evo III 16g.

22 psi is all that I can muster off of 93 octane gas with the stock 43.5 base fuel pressure. I might be able to go a few psi higher if I were to bump my fuel pressure up to 50psi. Although I'm also at 2500ft above sea level so I can't be to sure on that, without doing a log.

Anyways... since I'm running nitrous, and it being a wet kit I don't have to worry about it as much since the nitrous gets it's own fuel from it's own source, and has nothing to do with the injector size.

 

[Stapl3]

For 93, anything after 18psi is pushing it unless you have meth/alky.

I cannot stand posts like this. Where the hell do people get this shit from?

 

[v2ner]

What are you talking about?

 

[imdrax]

If anyone is running an EvoIII 16g, 550's, 2G MAF, 255 fp I was wondering what fuel pressure your running. Im running 43psi (hose off) atm but I am outflowing my injectors at just 18 lbs of boost, m high throttle settings are in the upper 20 to lower 30s and still getting some fuel cut style stutters at the track. Im curious what the max psi I can set my AFPR at is so that I dont go too far when adjusting the pressure.

Had to bring this from the dead because this is EXACTLY what I'm experiencing. My settings are in the +20's-30's, I get "fuel cut style" stutters, and my IDC are increasing with my afc settings increasing. Did the OP ever solve the issue? Did raising base FP help with your IDC's? My setup is EXACTLY the same so any extra input would be greatly appreciated.