fuel injector question

[dsmtalontsi95]

I have a 2.3 stroker and a frank 3 wich is a 57 trim I plan to run aroun 20psi. My setup is 255hp pump and -6 to replace stock lines, aem fuel rail, afpr, and 660's. The question is will the 660 hold up now that I have -6 lines?

 

[snowborder714]

You shouldn't have a problem running a -6 feed line with 660cc injectors. Just know that you're pretty much at the upper limit of the S-AFC.

 

[dsmtalontsi95]

I'll be getting link before I start to run the car.

 

[snowborder714]

If you're getting DSMlink, then you'll have no problem controlling the 660cc injectors, and might even want to think about upgrading them since DSMlink can handle it and you would know you would never max them out.

Edit: Just saw that you're from PA as well. Nice to see more locals on here

 

[JayRolla]

If your going with link then get 1150cc injectors. This way you will never have to upgrade again and if you want to run e85 you wont have a problem.

 

[dsmtalontsi95]

I herd e85 is screwing everything out of control. I know boat gas tanks made of fiber glass are leaking through with just the 10% ethanol.

 

[Splitpi]

I don't think you would ever utilize the full potential of the turbo with your 660's. Get 800's, rewire the fuel pump. Then shoot for the moon.

Honestly you are hitting fuel limitations if you go larger than 800'cc. Stock Fuel pressure is 43.5 psi. If you raise boost by 20 psi, your fuel pressure will be 63.5 psi. Your maxing out the 255 flow rate. See this link for info on how to calculate it.

I roughly calculate you will max the wally 255 with 880'cc injectors running 20 psi of boost. I would never run that close to the edge and so would give my self a 15% safety buffer ... which is 750 cc injectors. But that is my opinion on safety and what to run based upon my rough math (yes I used linear interpolation rather than a more appropriate quadratic... the end result is "close" in either case).

Here is a link to give you the calculations for a ball park figure of what kind of power you can achieve under ideal conditions from injectors. I get a figure of between 350 to 418 hp depending on fuel, temperature, humidity, engine efficiency etc... Note: if you drop the safety margin to 10% you end up with 800 cc injectors and a potential maximum power range of 375 to 443.

If you are fine with these numbers, the great you are good to go. If you wanted more power or thought you get more out of them... then you will need to reconsider your fuel supply.

 

[whiteythepimp]

all you need is 950 injectors to run e85.. and you need to retard the hell out of your timing to get more of a gain then regular pump gas.. Just my .02 though..

as far as injectors go.. Order you dsmlink programmed with whatever size you choose.. I wouldnt recommend going high then 950's because it's a waste unless you wanna push low 8's or high 7's.. Even then I dont think you'd need 1150's IMO from building motors in the past..

 

[Splitpi]

all you need is 950 injectors to run e85.. and you need to retard the hell out of your timing to get more of a gain then regular pump gas.. Just my .02 though..

as far as injectors go.. Order you dsmlink programmed with whatever size you choose.. I wouldnt recommend going high then 950's because it's a waste unless you wanna push low 8's or high 7's.. Even then I dont think you'd need 1150's IMO from building motors in the past..

As shown above, any thing larger than 880's (at 80% IDC usage) will cause a lean condition as the fuel pump will no longer be able to supply the injectors the fuel they need to maintain the power and fuel mixture. Assuming he has a turbo and setup to actually get to fully using 880's. And mind you while Ethenol has less BTU's (i.e. energy) than gasoline so you must go larger, the fuel pump will still only flow x amount of fuel irregardless of it being ethanol or gasoline. So the larger Injectors would gain him nothing.

So if the fuel pump is running 20 psi, it can flow 880 cc/min (max) that is the largest injectors he can theoretically take advantage of with out causing the injectors to outflow the fuel pump. Now if Ethanol is used in place of the fuel, you still cannot increase the injectors as you gain nothing since the fuel pump cannot flow more than 880's. The rule of thumb on Ethanol is that it requires 30% more fuel than Gasoline to produce similar power (this can very of course). So ineffect, running 880's with Ethanol would be equivalent to running 600's with Gasoline. So actually, Ethanol would be a further power hinderance.

The limiting factor still is the fuel delivery via the pump to do the boost pressure. A drop in fuel pressure would greatly increase the pump's ability to deliver more fuel. However, the injector now flow less due to the lower fuel pressure. But the plus side is that you can then use larger injectors to compensate and still have a net result of more fuel flow due to the fuel pump being in a more ideal power band.... if that makes sense.

 

[whiteythepimp]

that makes plenty of sense. But heres the whole catch.. Theres a couple of threads on other forums (honda and nissan.. Dont want to name drop exact forums..) that they have successfully rewired the 255 walbro to in fact make more pressure.. How I dont exactly know cause i'm very noob at wiring.. Well not that i'm noob but i'd much rather have a trained professional do something like that since it is dealing with fuel, which in my case would probably wind up being an explosion at 100 on the highway... In any event, theres ways out there to manipulate, to get what you want.. As with any car in life

 

[Splitpi]

that makes plenty of sense. But heres the whole catch.. Theres a couple of threads on other forums (honda and nissan.. Dont want to name drop exact forums..) that they have successfully rewired the 255 walbro to in fact make more pressure.. How I dont exactly know cause i'm very noob at wiring.. Well not that i'm noob but i'd much rather have a trained professional do something like that since it is dealing with fuel, which in my case would probably wind up being an explosion at 100 on the highway... In any event, theres ways out there to manipulate, to get what you want.. As with any car in life

The 255 is voltage dependent.... higher voltage better results. Basically if we look at P(power) = V(voltage)*I(current) then if current remains the same and we increase voltage we get more power. Also it probably has alot to do with the luck of the draw on the pump and how well it is made.

There are also two flavors of 255's the regular the HP (high Pressure) version. I only quoted the regular version. The HP gives a little extra oomph.. at the higher boost levels than the regular version. So it may be better suited for the 20+ psi high power usage. You can crunch the numbers if you like.

The point I am making is not that my numbers are exact, they aren't, they are just ball bark and in my best guess withing 10% accuracy of what could maximally be expected from the Wally 255. I am a cautious modder, and I just don't want people to blow their car up. So take my advice as you will.

The other point though is that there is alot of math behind this that can be applied to give you an idea of what the parts can do in a setup under certain conditions. It takes some of the guess work out.

 

[JayRolla]

As shown above, any thing larger than 880's (at 80% IDC usage) will cause a lean condition as the fuel pump will no longer be able to supply the injectors the fuel they need to maintain the power and fuel mixture. Assuming he has a turbo and setup to actually get to fully using 880's. And mind you while Ethenol has less BTU's (i.e. energy) than gasoline so you must go larger, the fuel pump will still only flow x amount of fuel irregardless of it being ethanol or gasoline. So the larger Injectors would gain him nothing.

So if the fuel pump is running 20 psi, it can flow 880 cc/min (max) that is the largest injectors he can theoretically take advantage of with out causing the injectors to outflow the fuel pump. Now if Ethanol is used in place of the fuel, you still cannot increase the injectors as you gain nothing since the fuel pump cannot flow more than 880's. The rule of thumb on Ethanol is that it requires 30% more fuel than Gasoline to produce similar power (this can very of course). So ineffect, running 880's with Ethanol would be equivalent to running 600's with Gasoline. So actually, Ethanol would be a further power hinderance.

The limiting factor still is the fuel delivery via the pump to do the boost pressure. A drop in fuel pressure would greatly increase the pump's ability to deliver more fuel. However, the injector now flow less due to the lower fuel pressure. But the plus side is that you can then use larger injectors to compensate and still have a net result of more fuel flow due to the fuel pump being in a more ideal power band.... if that makes sense.

My brother is running 1000cc injectors on a rewired 255 and has no problems at all. Your math and info seem logical but in real life situations ive seen many people run just a 255 on 1000cc or larger injectors.

When it does become a problem you can run a 255 inline along with the internal pump without issues and have all the fuel delivery you need to run e85 and those injectors. E85 will give you every last bit of power out of that turbo and motor. It allows you to run as much boost as the turbo can and add pretty much any amount of timing that you feel safe with. Not to mention its under $2/gal in most places, plus your helping save the air.

You look at a lot of race fuel tunes and they are running 30+ psi and 14-18* timing when you look at e85 tunes and they are running the same amount of boost and incredible amounts of timing. Ive seen people run 32* by redline on e85 tunes.

 

[Splitpi]

My brother is running 1000cc injectors on a rewired 255 and has no problems at all. Your math and info seem logical but in real life situations ive seen many people run just a 255 on 1000cc or larger injectors.

When it does become a problem you can run a 255 inline along with the internal pump without issues and have all the fuel delivery you need to run e85 and those injectors. E85 will give you every last bit of power out of that turbo and motor. It allows you to run as much boost as the turbo can and add pretty much any amount of timing that you feel safe with. Not to mention its under $2/gal in most places, plus your helping save the air.

You look at a lot of race fuel tunes and they are running 30+ psi and 14-18* timing when you look at e85 tunes and they are running the same amount of boost and incredible amounts of timing. Ive seen people run 32* by redline on e85 tunes.

What boost level, what fuel pressure, what IDC? Also is it a regular 255, or a HP 255? Also what voltage is it receiving? 1000cc's on a 255 is meaningless without the context, and I mean no disrespect for saying it that way Jay. So please don't take offense.

But you are absolutely correct that you can add other pumps to compensate. And I am not knocking... no pun intended, the value of the Ethanol. It is a useful fuel due the high Octane levels decreasing knock. But as always there are trade offs to every approach. I just want to ensure that the OP is aware of the trade offs for reaching his goal and let him decide on the path he wants.

 

[dsmtalontsi95]

Yes, no pun intendeed please. I will have to upgrade then, I just didn't know how long to stay with the 660's. I guess times up.

 

[2gGSX]

What boost level, what fuel pressure, what IDC? Also is it a regular 255, or a HP 255? Also what voltage is it receiving? 1000cc's on a 255 is meaningless without the context, and I mean no disrespect for saying it that way Jay. So please don't take offense.

But you are absolutely correct that you can add other pumps to compensate. And I am not knocking... no pun intended, the value of the Ethanol. It is a useful fuel due the high Octane levels decreasing knock. But as always there are trade offs to every approach. I just want to ensure that the OP is aware of the trade offs for reaching his goal and let him decide on the path he wants.

Sorry to whore the OP's thread even more, but this brings up an interesting point regarding the fuel pumps.

As Splitpi mentioned, the biggest opponent of fuel pumps is high fuel pressures. IIRC, Jay's brother runs a 1g as well and thus should be at 37 psi base fuel pressure. With that number and assuming the pump gets 14.0V constantly, then the 255HP would be good for 3828 cc/min of fuel *IDEALLY*. His 1000cc injectors would actually be behaving like 923's (again theoretically), and thus he would be nearing the very peak flow capacity of the fuel pump.

Most people would rather not run this close to the theoretical max of the fuel pump, especially given that the actual flow is definitely below the projected flow. To that extent, they should take strain off the fuel pump by lowering base fuel pressure (and/or boost) and then compensating with larger injectors.

 

[Splitpi]

Someone asked me this question and my response to fully answer it was too long to reply with. I thought it would be informative and so I am posting it in this thread aswell.

i was just wondering why it seems like on higher fuel pressure the pump flows less? and how do you get a flow rate with the fuel pressure and voltage?

I don't know "why" exactly other than it does. I can reason why though. Imagine trying to toss a water balloon 10 mph... now try to throw it 100 mph. It gets alot tougher because you are putting alot more energy into it make it move that much faster. Or perhaps in terms of an air compressor. For instance if you have a small pancake compressor it may only deliver 2.0 SCFM at 90 psi, but can make 4.0 SCFM at 40 psi. While a large compressor could easily make 4.0 SCFM at 90 psi. Basically, its just that the pump is stronger and more efficient.

I based my calculations off of Road Race Engineerings data. Then linear interpolated the values for inbetween them. In reality, the real numbers are quadratic... but that is too difficult to solve quickly and linear is within 10% of the actuals.

See the attached jpeg for the table.

To solve the interpolation for value, choose a fuel pressure. Which is (boost Pressure) + (Base Fuel Pressure, i.e. 43.5 for 2G) = Boosted Fuel Pressure. So 20 psi boost + 43.5 base = 63.5 fuel pressure

then interpolate for the values you want.

y = y0 + (x - x0) (y1 - y0)/(x1 - x0)

for example I want to know the maximum output of a Wally 255 running at 14V and 20 psi. I look on my table and see that 63.5 is between the points 58 and 73 of the data sample... so I will use those numbers.

New pressure = 230.92 + (63.5 - 58)*(182.97 - 230.92)/(73 - 58)

which equals 213.34 ltr/hr.

Now convert liters per hour (ltr/hr) to cc/min

(213.34 ltr/hr * 1hr / 60 mins)*1000 cc/ltr = (213.34/60) * 1000 = 3555.6 cc/min

That is the maximum flow for all 4 cyclinders , so lets find the individual cylinders...
3555.6 cc/min / 4 cylinders = 888.9 cc/min

That is the maximum injector size.

 

[JayRolla]

What boost level, what fuel pressure, what IDC? Also is it a regular 255, or a HP 255? Also what voltage is it receiving? 1000cc's on a 255 is meaningless without the context, and I mean no disrespect for saying it that way Jay. So please don't take offense.

But you are absolutely correct that you can add other pumps to compensate. And I am not knocking... no pun intended, the value of the Ethanol. It is a useful fuel due the high Octane levels decreasing knock. But as always there are trade offs to every approach. I just want to ensure that the OP is aware of the trade offs for reaching his goal and let him decide on the path he wants.

He is running 26psi that drops to about 21psi by redline on his evo16g. Running stock fuel pressure on a 255hp. I think he said he was at 73% IDC on e85. He has it rewired so I'm guessing the pump is seeing 14volts constant. He also had upgraded hard SS line from tank to upgraded fuel filter and braided SS line from filter to stock rail.

He just retuned after a new head with 272's. He was pushing 30* timing and had zero knock all the way through. He is also using the greddy emanage to tune and I'm very impressed on how well it controls the large injectors.

We are hoping he can get his custom actuator to hold some more boost bye tightening it up a little, if not we are going to go with an external wastegate.

 

[JayRolla]

I herd e85 is screwing everything out of control. I know boat gas tanks made of fiber glass are leaking through with just the 10% ethanol.

You do know that most gas at pumps are already a 10% ethonal mix. At least in CO it is, says it right on the pump.

 

[Splitpi]

You do know that most gas at pumps are already a 10% ethonal mix. At least in CO it is, says it right on the pump.

Ya, Iowa sells 15% mix 89 octaine (mid grade) cheaper than the straight 87 (regular) and 91 (premium). I used to run it in my mustang and I never really noticed a mpg drop from the 15% over the straight.

 

[Splitpi]

He is running 26psi that drops to about 21psi by redline on his evo16g. Running stock fuel pressure on a 255hp. I think he said he was at 73% IDC on e85. He has it rewired so I'm guessing the pump is seeing 14volts constant. He also had upgraded hard SS line from tank to upgraded fuel filter and braided SS line from filter to stock rail.

He just retuned after a new head with 272's. He was pushing 30* timing and had zero knock all the way through. He is also using the greddy emanage to tune and I'm very impressed on how well it controls the large injectors.

We are hoping he can get his custom actuator to hold some more boost bye tightening it up a little, if not we are going to go with an external wastegate.

Ahh... so now we have substance.

Base 1G Fuel Pressure is 37 psi. Boost pressure is 26 psi. At boost fuel pressure is 63 psi.

1000 cc injectors are rated at that value for 80% IDC (generally) at 43.5 psi fuel pressure. So if you run 1000cc at 37 psi, you are dropping the flow rate. We can calculate the loss by:

New flow rate = Sqrt(New pressure /Old pressure) * Old flow rate

New flow rate = Sqrt(37/43.5) * 1000 = 922 cc/min. So running the 1000 in a 1G will only be flowing the same as 922 in a 2G.

Also as measured he is hitting 73% IDC at that boost, which is ~ 857 cc/min.

If I crunch the number for a Wally 255 at 63 psi on a rewire, I get somewhere in the neighborhood of 880 cc/min. Meaning, yes it is possible under the conditions you stated and a is real life collaboration of the math.

The devil is always in the details.

 

[JayRolla]

Ya, Iowa sells 15% mix 89 octaine (mid grade) cheaper than the straight 87 (regular) and 91 (premium). I used to run it in my mustang and I never really noticed a mpg drop from the 15% over the straight.

You shouldnt lose fuel mileage since your not adding fuel. You loose fuel mileage on straight e85 because you are adding 30% fuel to compensate.

 

[JayRolla]

Ahh... so now we have substance.

Base 1G Fuel Pressure is 37 psi. Boost pressure is 26 psi. At boost fuel pressure is 63 psi.

1000 cc injectors are rated at that value for 80% IDC (generally) at 43.5 psi fuel pressure. So if you run 1000cc at 37 psi, you are dropping the flow rate. We can calculate the loss by:

New flow rate = Sqrt(New pressure /Old pressure) * Old flow rate

New flow rate = Sqrt(37/43.5) * 1000 = 922 cc/min. So running the 1000 in a 1G will only be flowing the same as 922 in a 2G.

Also as measured he is hitting 73% IDC at that boost, which is ~ 857 cc/min.

If I crunch the number for a Wally 255 at 63 psi on a rewire, I get somewhere in the neighborhood of 880 cc/min. Meaning, yes it is possible under the conditions you stated and a is real life collaboration of the math.

The devil is always in the details.

Ok then I guess it does work with the math.

 

[Loewen21]

You shouldnt lose fuel mileage since your not adding fuel. You loose fuel mileage on straight e85 because you are adding 30% fuel to compensate.

Because of the amount of ethanol in there, you may have to add more fuel to get the same desired result vs. fuel with 0 % ethanol.

 

[Splitpi]

One other thing I do want to point out about the fuel pressure. I mentioned that as you change your base fuel pressure you must compensate for the decreased pressure to figure out your new flow rate with the equation:

New flow rate = Sqrt(New pressure /Old pressure) * Old flow rate

Now you (generic you) are thinking huh... AHA but under boost I'm pressurizing the fuel line more so wouldn't my injectors flow more? I.e 800 at 60 psi would flow:

New Flow Rate = Sqrt(60/43.5) * 800 = 939 cc/min?

And the answer is no. The reason is because you must think in the perspective of the Injector. On side of it is pressurized fuel and in this case at 60 psi. On the other side of it pressurized air entering at 16.5 psi. This is the exact same pressure differential as if we had 0 boost psi on one side and 43.5 psi of fuel pressure. Meaning the fuel is still entering at 43.5 psi over boost. As such we still use the injector value as measured at its base pressure.