temporary fueling solution ideas?

[vrg3]

Absolutely correct. Who said a 1:1 was a rising rate?

Mike and Jason.

The whole assed solution apparently isn't reasonable.

I'm assuming you're saying that a very expensive standalone ECU is the whole-assed solution. Not everybody agrees. There are several solutions that are expected to arrive sometime in the next few months that may be better.

By static, do you mean BASE fuel pressure? If so, then no, your rrpfr does not allow you to increase base pressure.

If you only want to increase base pressure (as you call it, "static") then a rising rate is not the correct way.

Yeah, I think there's some confusion going on here... Increasing base fuel pressure or static fuel pressure is not what I was suggesting originally to Jason.

[THAWA]

Is a self-tuned piggy back really a whole-assed solution though? Seems to me like it's more of a three-quarters-assed solution or so.

[vrg3]

Maybe. There are other options too though... MegaSquirt II is coming out soon, and some kind of hacked-stock-ECU thing still might happen (I'm due to graduate in the first week or two of March).

[Innovative Tuning]

inovative, does the fpr your talking about come with barbed ends and a gauge for that price?

It accepts a standard 1/8" NPT fuel pressure gauge. The ones we use are liquid filled and they're cheap (20 bucks).


Call me crazy but I've always understood that if an FPR increases fuel pressure based on positive manifold pressure, it is a rising rate regulator. Whether the regulator uses a ratio of 1:1 or something else doesn't change that and neither does whether it is adjustable or not. Rising rate, not rising ratio.

The stock FPR on a legacy turbo is a 1:1 non-adjustable RRFPR. Fuel pressure increases with positive pressure (boost), but there is no adjustment for the ratio, or for base pressure. The Aeromotive regulators I use are adjustable 1:1 RRFPRs because you can adjust the base pressure, but not the ratio of fuel/boost.

Some FPRs do NOT increase fuel pressure as positive manifold pressure increases. These are not rising rate FPRs, regardless of whether base pressure is adjustable on them or not.

RRFPR - Rising Rate Fuel Pressure Regulator - Fuel pressure rises with positive manifold pressure. Fixed base pressure.
ARRFPR - Adjustable Rising Rate Fuel Pressure Regulator - Fuel pressure rises with positive manifold pressure. Adjustable base pressure.
AFPR - Adjustable Fuel Pressure Regulator - Fuel pressure remains static regardless of positive manifold pressure. Adjustable base pressure.
FPR - Fuel Pressure Regulator - Fuel pressure remains static regardless of positive manifold pressure. Base pressure is not adjustable.
FMU - Fuel Management Unit - Crap!



Someone asked for me to use numbers but I'll give you a recipe rather than specific results. FMU's uses different ratios such as 2:1,3:1,6:1 to add 3 parts fuel per 1 part boost, whereas the stock FPR adds 1 part fuel per 1 part boost. I hate FMUs...they're a hack. Even moreso than an S-AFC is a hack.

-Mike

I've never known a circumstance where a rising rate is better then a fixed rate adjusted accordingly.

Any boosted application...but perhaps you're using a different definition of RRFPR and that's why you're saying this.

-Mike

[vrg3]

It accepts a standard 1/8" NPT fuel pressure gauge.

NPT or NPTF?

Call me crazy but I've always understood that if an FPR increases fuel pressure based on positive manifold pressure, it is a rising rate regulator.

Okay, you're crazy.

Whether the regulator uses a ratio of 1:1 or something else doesn't change that and neither does whether it is adjustable or not. Rising rate, not rising ratio.

What rate is rising in that configuration?

The stock FPR on a legacy turbo is a 1:1 non-adjustable RRFPR. Fuel pressure increases with positive pressure (boost), but there is no adjustment for the ratio, or for base pressure.

Fuel pressure doesn't exactly "increase with boost." It's just maintained constant relative to manifold pressure. At idle, fuel pressure is around 26 psig, and when the motor's not running, it's 26.3 psig.

This does not increase fueling with boost.

Some FPRs do NOT increase fuel pressure as positive manifold pressure increases. These are not rising rate FPRs, regardless of whether base pressure is adjustable on them or not.

They certainly are not RRFPRs. Nor are they manifold-referenced FPRs.

Someone asked for me to use numbers but I'll give you a recipe rather than specific results. FMU's uses different ratios such as 2:1,3:1,6:1 to add 3 parts fuel per 1 part boost, whereas the stock FPR adds 1 part fuel per 1 part boost. I hate FMUs...they're a hack. Even moreso than an S-AFC is a hack.

What you are calling an "FMU" here is what a rising-rate fuel pressure regulator is.

It is certainly a hack.

And it is the hack that will help Jason's car run.

[THAWA]

I see. What you and the other Jason are refering to as RRFPR, we are considering a FRFPR (fixed rate). And what we're considering a RRFPR, you're considering a FMU. Just a miscomunication.

[JasonGrahn]

They're all FMUs in the general scope of things. They are all units designed to manage fuel, so PLEASE (and this goes for everyone, for the sake of making things easier on the board in the long run) don't define one product by a general term.

but perhaps you're using a different definition of RRFPR and that's why you're saying this.

I can't say I agree with Innovatives definitions and IMO they simply work to confuse the matter.

It is certainly a hack.

And it is the hack that will help Jason's car run.

Vik is correct, in a movie line sort of way.

he certainly is a madman. And he's the madman that is going to save this planet...

[vrg3]

Hehehe.

Hardy, I don't think it really is just an issue of differing definitions... The rising rate fuel pressure regulator was first introduced by Bell Engineering as a hack to provide some kind of fuel control for their turbo kits.

The manifold-referenced fuel pressure regulator's been around longer. The term "rising rate fuel pressure regulator" was coined by Bell to describe their new device and describe what it does differently from other FPRs.

[azn2nr]

soooo the question remains. whats the best bandaid (aka: haffassed solution) to get more fuel in at higher boost in order to run higer boost safely. be it fmu or wot wet fuel injection. and where do i find it.

standalones are a good solution and a whole hearted one at that but the thing is a standalone costs more than half of the price of the car when i bought it. the piggyback in devlopment should be a viable option and the autronic plug and play may be a viable option too. im not much on megasqurits mostly because electronics i have to build usuly dont work.

[Innovative Tuning]

Well folks...I was 99% sure my definitions were correct, and then I confirmed them with a tuning reference manual and a GM fuel injection manual.

If a fuel pressure regulator raises the fuel pressure with positive manifold pressure, it is a rising rate fuel pressure regulator.

The stock FPR on a legacy SS is a non-adjustable RRFPR because it raises the fuel pressure with positive manifold pressure, but you can't adjust base pressure. An aeromotive is an adjustable RRFPR because it raises fuel pressure with positive manifold pressure and you can adjust base pressure.

The average honda for instance has a standard non-adjustable FPR. If you boost the car, the fuel pressure will not rise with manifold pressure. You can also buy adjustable FPR's which can adjust base pressure, but do not increase the fuel pressure with positive manifold pressure.

-Mike

[vrg3]

Jason - A rising rate fuel pressure regulator with a rising rate will be the easiest one to set up. Try one with maybe a 4:1 or 6:1 rise ratio to start with... Ideally you'd find one that lets you change the ratio.

You can buy preassembled MegaSquirts from several sources. They cost more than the parts, of course, but they're still pretty cost-effective.

Mike - Well, we seem to have conflicting info.

It seems kind of silly to call an FPR "rising rate" if there is no rate that rises though. I wonder what GM was thinking.

Where did you hear that Hondas don't have manifold-referenced fuel pressure? I know my parents' 95 Odyssey does.

[douglas vincent]

I think (and I could be wrong, was once before) that the easiest way to tell a rrfpr from a regular fpr is simply whether or not the fpr has a vacumn line attachment. The only reason for the vacumn line would be to activate fuel pressure, correct?

[vrg3]

Well, we're still disagreeing on what an RRFPR is.

I say the stock FPR, which has a vacuum line, does not have a rising rate.

[azn2nr]

in all techinal terms the rate does rise with the maniflod pressure. but thats beside the point.

where do i even start looking for one of these real rising rate controlers?

[vrg3]

What rate rises? Pressure is not a rate.

Like I said earlier, I believe Kelley had one for a little over a hundred bucks. You might PM him or visit http://www.perfectionmotorsports.com/.

[azn2nr]

fine if pressure is not a rate you are right.

[douglas vincent]

http://www.horsepowerfreaks.com/viewpro ... nits~.html

[Innovative Tuning]

Mike - Well, we seem to have conflicting info.

It seems kind of silly to call an FPR "rising rate" if there is no rate that rises though. I wonder what GM was thinking.

Where did you hear that Hondas don't have manifold-referenced fuel pressure? I know my parents' 95 Odyssey does.

They have manifold referenced pressure, but fuel pressure does NOT increase with POSITIVE manifold pressure. As I've been saying, this is the difference between a standard and a rising rate regulator.

As long as the fuel pump can keep up with the demand, as pressure increases, the flow rate increases as well. That is the rate that's rising.

-Mike

[azn2nr]

douglas, thanks for the link but with thoes id still have to figure out which ratio i would need. if olny the ratio was adjustable?

[vrg3]

They have manifold referenced pressure, but fuel pressure does NOT increase with POSITIVE manifold pressure.

What does "positive" manifold pressure have to do with it? A manifold-referenced FPR doesn't know anything about "positive" or "negative" pressure because those are just terms used relative to barometric pressure, and the FPR has no diaphragm exposed to the atmosphere.

You don't think the Honda Odyssey's fuel rail pressure will be higher if the manifold's above atmospheric pressure than when it's at exactly atmospheric pressure?

As long as the fuel pump can keep up with the demand, as pressure increases, the flow rate increases as well. That is the rate that's rising.

That is not correct.

With a 1:1 manifold referenced FPR like the ones mentioned in this thread (including the ones that are stock on the Honda and on the Subaru), the flow rate of the injectors does not increase as manifold pressure goes up. It just stays constant.

douglas, thanks for the link but with thoes id still have to figure out which ratio i would need. if olny the ratio was adjustable?

You could just pick a Vortech unit and then possibly shell out a little more money for a different ratio kit if necessary. You might want to look through the "Aftermarket Forced Induction" forum on NASIOC to see what ratio RS-T people like. You'd probably need something similar or maybe a little bit less.

Most easily adjustable RRFPRs are pretty expensive... Like twice as expensive as the fixed-ratio ones. So even if you have to buy one or two recalibration kits you'll still probably come out ahead of paying for an adjustable one.

Or maybe we can work some math through and try to predict what ratio would work well. We'd just have to predict the airflow you'd expect and then figure out how much fuel you need for that much air. Then we could figure out the pressure needed at the injectors. If we do this for a few different values of manifold pressure we could probably settle on a good choice for the ratio.

Yeah. We should do that.

I'll try to figure some of this out. If you don't see a post from me about it in the next day or two, PM me to remind me.

[Innovative Tuning]

To answer the question about a hack to get more fuel, we don't hack cars together at my shop so I hesitate to add my 2 cents, but I'd do the injector mod of hacking the caps off if that's possible on the legacy injectors, get a walbro 255 high pressure pump, and a piggyback fuel controller like an E-Manage as a barebones fuel upgrade.

Timing control is still a major issue, especially if you're running a boost controller that can create high boost at part throttle, so that cannot be ignored if you want the car to run properly. That said, we've pushed our rally car to the limit by running 13-14psi at 12-12.5:1 air fuel with no intercooler on 93 octane with stock timing control during race conditions and the engine is running strong. The 22t is a serious piece of work.

-Mike

[azn2nr]

your idea of the modded injectors is the way i will be going as soon as the piggyback in devlopment is completed or the autotronic unit is found to work with our cars

[vrg3]

Don't take this the wrong way, but I don't have time to argue this anymore as I'm running a business.

I take no offense. I'm just trying to do my part to make sure the facts are presented correctly. I think it's important to understand how things work and to avoid perpetuating misconceptions.

On this new point of flow vs. pressure. The flow rate of the injectors DOES go up with pressure increase as long as the fuel pump can back up the demand for increased flow/presure. That is the whole point of boost referencing the FPR, so there is more fuel available under boost.

This is incorrect.

The purpose of most OEM manifold-referenced fuel pressure regulators is to maintain a constant fuel flow independent of manifold pressure.

An MPFI fuel injector is essentially a solenoid valve between the fuel rail and the intake manifold. Flow through an orifice depends basically on the size of the orifice and the pressure difference across the orifice.

Thus, maintaining a constant pressure differential between the rail and manifold is done not to increase flow at higher pressures but just to maintain constant flow at all pressures.

While gauge pressure in the rail is increasing, differential pressure between the rail and manifold is staying constant. This is an important point to understand. Our 370cc/min injectors flow 370cc/min at idle (fuel pressure of about 26 psig) and 370cc/min at peak boost (fuel pressure of about 45 psig), because manifold pressure is always 36.3 psi below fuel rail pressure. Always. Always always.

[Innovative Tuning]

vrg3 - I don't know what I was saying in that post. Sorry about that. I need to stop making technical posts while I'm on the phone with customers. LOL. I just edited it so nobody gets confused.

-Mike

[vrg3]

Okay, I don't have time right now to do the calculations all the way
through, so let's just try a back-of-the-envelope one now.

Assumptions:
Engine speed = 6500 RPM
VE = 80%
Ambient density of air = 0.00125 g/mL
Density of fuel = 0.7 g/mL
Air/fuel ratio = 11.0:1
Boost = 15psi
Density ratio = 2.0:1

Airflow = 2212 cc/cycle * 3250 cycles/min * 0.80 = 5751200 cc/min
Required fuel flow = 5751200 * (0.00125*2) / 11 / 0.7 = 1867 cc/min
Required flow per injector = 1867 cc/min / 4 = 467 cc/min
Required differential pressure increase = 36.3psi*((467/370)^2-1) = 21.5psi
Required rise ratio = (21.5 psi / 15 psi) + 1 = 2.43:1

So it looks like a 4:1 rising rate fuel pressure regulator would be plenty. Did I do this right?