22 replies to this topic

[T5Hammy]

In regards to running an adjustable fpr instead of buying greens.

-If I pick up the EST 3-5 bar adjustuble FPR, is there a limit to what whites and the stock system can support, I know Hussein is running around 4 bar at idle, is it feasible to run 5 bar at idle? In theory this would take whites from 350cc/min to 450cc/min, if the whites can even handle the flow.

And it will be tuned for once it's installed and turned up, if I can't run 5 bar I'll probably set it to 4 bar for ~400cc/min

Only car I've done much fuel adjustment on had mechanical fuel injection so the whole adjustable fpr is kinda new to me, forgive me if this question is stupid

[sjmcarz]

Most likely the injectors can only flow what their max rating is no matter how much FP you send to them. That's why we have orange,whites, blues, greens.................. On the other hand, I'd imagine that one could get greens and use an adjustable FPR to lower the flow.

Hopefully someone with more info will chime in.

[T5Hammy]

Thats what I was worried about

[Volvo5.0]

I would think you could get a little more flow from the whites by cranking up the fuel pressure. Not sure how much though. These are the injectors I use http://www.ebay.com/...2138113&vxp=mtr and if you read through the listing you'll see they have different flow rates at higher pressure.

[Deimos]

The way I've always understood how fuel injectors work is that the computer opens and closes them in timed cycles to shoot in X amount of fuel based on the pressure. Higher pressure, more gets shot in in the same cycle length. And a learning ECU will notice it's running rich and tighten up the cycle times.

[Black Betty]

More FP will give you more fuel but I've never seen a FP curve vs flow rate for the volvo injectors. Injectors are not linear though so it wont be clear how much more fuel you've got.

If you had a way to monitor AFR, and Duty cycle of the injectors you could set you're optimal FP but that also means retuning the fuel table

[sjmcarz]

I would think you could get a little more flow from the whites by cranking up the fuel pressure. Not sure how much though. These are the injectors I use http://www.ebay.com/...2138113&vxp=mtr and if you read through the listing you'll see they have different flow rates at higher pressure.

But what pressure does Volvo use for their max flow rates?

[Deimos]

But what pressure does Volvo use for their max flow rates?

Presumably 3bar which is what they run them at.

[T5Hammy]

Hmm...maybe I will run some testing on the whites to see what I can get them to flow, I have a wideband, can you see injector duty cycle through OBD II or any other simple means (I know the controller for my water/meth kit can operate off of pulse width, can that be converted to duty cycle)?

Does anyone have any actual data on flow curves (or even accurate geusses), I know all the calculators are linear, which can't be accurate.

[fischmama]

I figure at some point they may start leaking if you go way above the designed pressure.

[aggarcia]

The orange and white injectors are rated at 3 bar. The blue and greens are rated at 3.8 bar.

One of the injector websites when discussing changing fuel pressure recommended limiting total pressure to 68 psi. Turning up the fuel pressure will is not meant to replace proper injector sizing.

AG

[Volvo5.0]

But what pressure does Volvo use for their max flow rates?

Since the stock fuel pressure is set at 3 bar for a '98, I assume Volvo is just listing the the flow of the white injectors at 350cc at 3 bar. May not be the max they can flow though. Looking around at different Bosch injectors, it looks like a lot of them show flow rates from 3 to 4 bar. I would assume you could safely go to 4 bar. Could you push them to 5 bar??? Don't think I would try it.

Like BB said, the changes would need to be tuned for. I had to when I replaced my injectors. I'm logging, so I could immediately see the drop in injector duty cycle. Some multimeters will let you check IDC.....http://www.amazon.co...e/dp/B0062V74Y6

[fischmama]

You guys do realize that M4.x will run 3 bar at idle and around 4 bar in boost right.

[the commissar!]

Best way to flow test them is bench test (special equipment).

If you just change FP or injectors (bigger) the ECU will adapt to the incorrect fuel level if you try to do it in the car. Eventually it will get out of range and set a CEL.

You cannot push more than x amount of fuel through the hole so there is a point where you gain nothing. Plus, the injector will also pattern differently when you change the pressure which will affect how efficiently combustion happens. Initially you might get better atomization but at some point you will get more of a stream which is not good for your air/fuel mixing. Unless you have a way to tune for the different fuel pressure and or different injectors, its best to leave be...

Note that recently it was mentioned that I and others are running these adjustable FPR's, but we also are running TurboTuner or have tunes designed for the mods or both. It is not a good idea to just throw more fuel in the mix without accounting for it in the tune so consider that before dropping coin on one. That being said, no reason not to buy one and set it at the factory setting...will work exactly like stock FPR and cost less but you have to get it set correctly and that may be tricky since there is not a conveinent dial that says 3bar, 4bar, 5 bar and you just dial it in to what you want.

You guys do realize that M4.x will run 3 bar at idle and around 4 bar in boost right.

yes, as I understand it, they (stock for '98) are variable FPR which is different from adjustible and variable FPR. The adjustment is in the starting point or base fuel pressure.

[sjmcarz]

The orange and white injectors are rated at 3 bar. The blue and greens are rated at 3.8 bar.

One of the injector websites when discussing changing fuel pressure recommended limiting total pressure to 68 psi. Turning up the fuel pressure will is not meant to replace proper injector sizing.

AG

^^^ Good advice ^^^

[T5Hammy]

I figure at some point they may start leaking if you go way above the designed pressure.

Good point, not my goal haha

The orange and white injectors are rated at 3 bar. The blue and greens are rated at 3.8 bar.

One of the injector websites when discussing changing fuel pressure recommended limiting total pressure to 68 psi. Turning up the fuel pressure will is not meant to replace proper injector sizing.

AG

ok, so thats definitely helpful for knowing how far to push them.

You guys do realize that M4.x will run 3 bar at idle and around 4 bar in boost right.

yes, the injector flow is rated at 3 bar though, correct?

Best way to flow test them is bench test (special equipment).

If you just change FP or injectors (bigger) the ECU will adapt to the incorrect fuel level if you try to do it in the car. Eventually it will get out of range and set a CEL.

You cannot push more than x amount of fuel through the hole so there is a point where you gain nothing. Plus, the injector will also pattern differently when you change the pressure which will affect how efficiently combustion happens. Initially you might get better atomization but at some point you will get more of a stream which is not good for your air/fuel mixing. Unless you have a way to tune for the different fuel pressure and or different injectors, its best to leave be...

Note that recently it was mentioned that I and others are running these adjustable FPR's, but we also are running TurboTuner or have tunes designed for the mods or both. It is not a good idea to just throw more fuel in the mix without accounting for it in the tune so consider that before dropping coin on one. That being said, no reason not to buy one and set it at the factory setting...will work exactly like stock FPR and cost less but you have to get it set correctly and that may be tricky since there is not a conveinent dial that says 3bar, 4bar, 5 bar and you just dial it in to what you want.



yes, as I understand it, they (stock for '98) are variable FPR which is different from adjustible and variable FPR. The adjustment is in the starting point or base fuel pressure.

First I have no intention of running this without tuning for it, I'm not intending to run rich (if that was my goal I'd go get some low impedance 1500cc injectors and run mad flames out my exhuast yo /gangsta voice).
Just looking for more fuel once I have a 50 trim installed, for less than a set of injectors (ie a bandaid).

As far as setting it to the initial pressure, can't I do what Hussein did and connect a pressure gauge to the fuel rail then adjust accordingly. If thats not a solution why not check inital duty cycle with the stock FPR at idle then install new adjustable fpr and set it so the injectors are at the correct duty cycle (not an exact method but should get a ballpark), then it can be slowly turned up (while tuning on a dyno) and tuned for accordingly (or turned back down if it isn't helping). This should make it obvious when you reach the higher end of the injectors efficiency.
Am I way off target here?

I knew more pressure meant better atomization, hadn't considered the fact that it will stream at some point, but it makes sense.

[the commissar!]

I didn't mean to be condescending, I just didn't want someone reading this who didn't know what they were gettin into to think of this like a MBC...a cheap easy way to get more power. More fuel = more power right?! Clearly you know it is not that simple...

You are not off base at all, you can do that to adjust it and if you use the newer design it can be done easily (where the adjuster is separate from the vac line. On the older straight design like I have, you would have to pull it, reset, and check reading...till you got it right. Again, not wanting people to think that it is a simple dial and go install. That comment was based on thinking that most don't have fuel pressure guage laying around but I guess "they" have loaners...but setting it up does take some effort.

Cheers!

[Volvo5.0]

One of the injector websites when discussing changing fuel pressure recommended limiting total pressure to 68 psi. Turning up the fuel pressure will is not meant to replace proper injector sizing.

AG

Probably the best advice. Get the proper size injector for your setup. If the whites are way to small for the job, get greens. BUT if the whites are borderline, you "might" get the little extra needed by bumping up the fuel pressure a little with an adjustable FPR and adjusting the fuel map.

[Platinum 850]

To address the initial question, injectors will flow more as pressure increases.
Here is a helpful link: http://www.witchhunt...ectorcalc1.php4

As others have already stated, increasing fuel pressure isn't the solution. Especially if you're going well above your stock pressure. to get your 350cc @ 3bar, to 450cc you would need to increase fuel pressure to: 5.0bar. And to think that when you are into boost, you'll be closer to 6.0 bar...

realistly a better question is what fuel pump do you have? what makes you think your fuel pump is up to the task of moving more flow at such elevated pressures?

I wouldn't exceed 4.0bar, which would net you ~404cc and thats with an upgraded fuel pump (proper walbro), I woudn't run beyond stock pressure with stock fuel pump.

I have actually been running greens @ 4.0bar (greens flow: ~480cc at this pressure) for the better part of a year now, and I do have a walbro fuel pump.
I have had no issues but I am actually installing these, http://www.fiveomoto...rch/?p=013us550 already ordered just waiting on delivery. The reason being even with an upgraded fuel pump, the addtitional strain of one full bar just doesn't sit well with me. If you can have the same result and run at a lower pressure, by using a properly selected/ sized injector, that is the way to go.

I will be selling the green injectors and 4.0bar dodge FPR once I get the new injectors. Feel free to PM or chech the for sale section, as I 'll post them once they have been removed from the vehicle.


A simplified way of viewing how an injector works, is anyone familiar with flow dynamics, picture an orifice. The purpose of an orifice is to allow "X" amount of flow as a direct result of delta P across the orifice.

This is regardless of ECU control or pulsation, which obviously factors into your injector duty cyclye. My statement is in regards to how pressure physically affects your setup

So if you're white injector was injecting into your cylinder with (0psig, Cylinder Pressure), and your FPR maintains 3.0 bar (~43.5psig, as your rail pressure). the delta P (or differential pressure) across your injector/ orifice is 43.5-0 = 43.5psig, which means your injector will flow 350cc/min

Same injector but now you are into boost at ~14.5psi, your variable FPR will be ~4.0bar (~58). As your injector has 4bar of pressure feeding into it, it is now injecting into a cylinder that is at 14.5psi, yet your delta/ differential pressure is still 3.0 bar (~58 - 14.5 = ~43.5).

Your are putting more strain onto your pump and anyting on your fuel system by having to maintain an increased operating pressure. This is all with your stock fuel pressure.

So imagine what happens as you increase your base pressure...

[850wagonT5]

Didn't see this mentioned, but another thing to keep in mind is when you change the fuel pressure, you're also changing the SPRAY PATTERN of the injector. It's spray pattern is engineered for the specific operating pressure it was intended for. This usually isn't an issue when moving up in pressure by small amounts (like 1.0 bar), but it's something to think about when running an injector designed for 4.0 bar, on a car only running 3.0 bar fuel pressure - the fuel won't atomize the same at the (25%) lower fuel pressure as it would @ 4.0 (OE) pressure.

That said, I was running at ~400cc (4 bar and whites) for a while on the T3/T4, before going to E85, and it didn't lean out on the wideband while running 17-18psi. That's about all I could run without ping or serious timing retard on regular gas (it wouldn't make any sense to run that setup @ above 20psi on regular gas and OEM management). So if you're planning to stay on regular gas and/or under 20psi, you'd be fine on the whites/blues and 4.0 bar.

I'm now running ~550cc and 4.0 bar on E85 and it's fine @ 22+psi. I switched to a Walbro 255lph, and this is on the same ARD tune as above.