Fuel Pressure Gauge? A/F Ratio Gauge?

[Rider90]

I did a quick search around the net and around here, but could not turn up much information. I am looking for some gauges and I was wondering what the advantage is to have a fuel pressure gauge and the advantage to having a Air/Fuel ratio gauge. Can someone explain the two to me?

[MM03MOK]

It depends how you're driving your car. Street and drag racing? Steady highway travel? Also, do you have the ability to change these parameters yourself? Is your car tuned to begin with? You'd need more than the A/F gauge to do it right. You'll need a wide-band O2 monitoring system. There are more important gauges for all around use that would better serve you as performance monitors, such as a tranny temp gauge.

[fastblackmerc]

I'd go with a tranny temp gauge also. I don't think fuel pressure is of any help.

[Rider90]

Already have tranny temp :)

[Pat]

Rider90; a tranny temp guage was recommended but you already have that.
An A/F ratio meter to be of any value has to be of the Wide Band variety and cost several hundred dollars and requires new bungs in the left and right exhaust header down pipe if memory serves. The value is marginal for a street machine unless you have a turbo or supercharger and a tuner.

The fuel pressure guage would be a nice addition with a power adder, ie nitrous. Since I have a Zex nitrous system both a fuel pressure and nitrous gas pressure would be beneficial. I'm in the process of saving for these two items. I have the pillar pod already.

The oil pressure and battery voltages guages already in our cars can be upgraded.

So, for your instrumentation, upgraded voltmeter, oil pressure, fuel pressure and tranny oil temp would monitor your engine/tranny's health nicely.

[RF Overlord]

^^^what pat said^^^

Jason, do you have the OEM fake oil pressure gauge or the real one?

Here's another thought: how about a real coolant temp gauge, instead of the half-assed OEM? That would be of more value than either the fuel pressure or the A/F for a street-driven N/A car.

[Rider90]

I have the ScanGauge so I have Water Temp, Volts, Ignition or Load, and MPG.

I have a Tranny Temp Gauge, OEM Voltmeter which will be pulled since I have the ScanGauge voltmeter, and OEM dummy oil pressure.

I will have a real oil pressure, oil temp, tranny temp, and what else?? two more slots open.

Lets say I get boosted down the road, so maybe a boost gauge, now that leaves one more open?? This also means I would be forced induction, what other gauge should be neccessary?

[MikesMerc]

As has already been said, an AF gauge without a quality wideband would be pretty useless.

Fuel pressure is a great gauge to have if you have a power adder. I watch my FP gauge, not the boost gauge, when I'm "on it." A good FP gauge can save you when you're running a power adder.

For NA cars, I wouldn't bother with either. I'd focus on the temp and oil gauge upgrades, then go with a tranny temp.

[Warpath]

Fuel pressure gauge is nice if you have an upgraded fuel system. Some aftermarket pumps will burn out over time in the returnless environment. You don't have to worry about OE pumps like the Cobra or Focus pumps. The fuel pressure gauge will give you an idication that the pump is starting to go.

A/F gauge is nice if you are pushing the hp envelope or are blown. It will let you know if you have bad gas or something else going wrong. EGT will do the same. You can put the A/F gauge in one of the rear 02 sensor bungs if you have the OE sensors turned off.

Autometer is coming out with wide band A/F meters soon. So, you will be able to get one that matches the rest of your gauges (if you have Autometers).

[SergntMac]

It depends how you're driving your car. Street and drag racing? Steady highway travel? Also, do you have the ability to change these parameters yourself? Is your car tuned to begin with? You'd need more than the A/F gauge to do it right. You'll need a wide-band O2 monitoring system. There are more important gauges for all around use that would better serve you as performance monitors, such as a tranny temp gauge. OMG! Spot on! My word, we have a gear head monster Bunny on our hands!

Honestly, I could not have said it better. I have a boost gauge because it came on the car, but I rarely look at it when into the boost because my attention is elsewhere, unless I'm on the race track in a controlled environment.

FP and AFR gauges are nice to watch. Very active...Keep moving around a lot. But, neither do much in providing advance warning of something gone wrong, with enough notice to correct the situation.

The only gauge I would like to add, would be tranny temp, but there is so much flexibility in my ScanGauge, I can pretty much tell when something is not right, so, I haven't gotten around to it yet.

If I were to gauge up (and I may) I would buy the Nexus stuff from AutoMeter. Only the best for my #1x.

[MM03MOK]

OMG! Spot on! My word, we have a gear head monster Bunny on our hands!The "gear head monster :bunny2:" has great mentors! :bows: And she's a pretty smart cookie to boot!

[Vortech347]

I run an AEM wideband and Autometer Electric fuel pressure on my stang. They match just fine. The new AEM's you can set up 6 different ways. Jegs has them right now for 280$!! Stay way from the POS autometer a/f gauges. (at least the older narrowband style) They read off your stock 02 and is not accurate for tuning.

DO NOT run an mechainical fuel pressure gauge inside the car unless you use an isolator (which are a pain to setup) . Its not legal at the track and stupid for street use. Electric ones are more expensive but they are much safer.

Here's a pic of the ones on my stang.

http://www.mercurymarauder.net/forums/attachment.php?attachmentid=85 45&d=1138734567

[martyo]

Since I have to take my glasses off to read the damn gauges, they are all a waste when I am driving. :D

I do use my boost gauge a lot, but mostly the recall function when I am at the track.

[sailsmen]

Our OEM Temp guage is useless, need 40+* to get it to move.

The FP is a good indicator on whats going on temp wise. As the temps in the heads increases the FP will increase.

[MikesMerc]

FP and AFR gauges are nice to watch. Very active...Keep moving around a lot. But, neither do much in providing advance warning of something gone wrong, with enough notice to correct the situation.


Not true at all. The marauder is my third supercharged car and all of them had (have) fuel pressure guages.

I saved my motor in my blown 1991 Mustang LX 5.0 when I noticed the fuel pressure wasn't where it was supposed to be. After only a few months of use, the new Ford Motorsport 155lph in tank pump started to die and starve the T-Rex in line pump. This happened only on WOT conditions under boost. I would never have noticed I was running lean if not for the guage. My exhuast was loud on that car and any hint of detonation at WOT was inaudible. After noticing the pressure wasn't where it should be on WOT (gradually falling pressure under WOT), I laid off it and shut it down until I could get it to the shop. Sure enough, the pump was bad. Although the computer compensated as best it could, and that did indeed buy me time, the gauge saved my motor.

[Rider90]

And where should the pressure be at? Also, would it be better to get a Digital FP gauge or analog based on the readings I need to keep track of?

[MikesMerc]

What pressure you run depends on your application, injector size, etc, etc. When you want to make smaller injectors "act" like bigger injectors, you raise the fuel pressure. In addition, under boosted applications where the cylinder pressure is higher, the extra pressure in the injector is needed. This was what boost a pumps do. They work fine up to a point.

Larger injectors can deliver more fuel at lower pressures. Your pump needs better flow rate, but the injectors need less pressure.

So, it completely depends on your set up. There is no one answer. For example, my 39lb injectors in my blown 5-0h needed 70 psi to deliver the right fuel under boost. On the other hand, the 60lb injectors I have on the Marauder only need 40 PSI to do their work. The Mustang put out 475rwhp, and the Marauder 530rwhp.

As for digital versus analog...I'll throw in my own opinion as there is no "best" solution. When it comes to fuel pressure, you'll find that the gauge "bounces around" alot...this is natural. This is caused by injector cycle (how fast the motor consumes fuel), whether you are under boost (boost a pump), etc, etc. Under these conditions, I personally feel an analog gauge is easier to read. Digital gauges moving too quickly don't tell the story clearly. That's just my opinion.

[QWK SVT]

AN A/F Guage can be very useful, particularly for boosted applications. Running an engine lean while under boost is a pretty good way to install a window in the block. This is assuming it's a wideband. A narrow band sensor is only going to act as a pretty light show, and an inaccurate one, at that.

Personally, I lean towards digital guages, as I don't want to have to think to hard about what the reading is, while I'm pedal to metal...

I've got one of these on the way, for my Lightning:
http://www.innovatemotorsports.com/xcart/product_image.php?imageid=60
Innovate Programmable Digital Gauge, Bosch 5-wire Wideband 02 Sensor, Bung/Plug Kit, and can output to my Xcal2, for datalogging at the track :banana:

[Rider90]

Thanks for the replies everyone!

[MikesMerc]

That wideband gauge is sweet! I'm going to look into that.

[Fourth Horseman]

A/F gauge is nice if you are pushing the hp envelope or are blown. It will let you know if you have bad gas or something else going wrong. EGT will do the same. You can put the A/F gauge in one of the rear 02 sensor bungs if you have the OE sensors turned off.


Does anybody know if Lidio's tune turns off the rear O2 sensors?

[Marauderjack]

I think all of the base SCT tunes turn them off??:beer:

Marauderjack:D

[QWK SVT]

That wideband gauge is sweet! I'm going to look into that.

Retails for $399US, for everything pictured. I got it from a supporting vendor of a different board, for $350US including shipping. Not a bad deal, and one of the better looking guages on the market. It's available in white or black face and aluminum or black bezel...

I'll have it this week. Mid pipes and high flow cats flow cats are coming for the L this week, too... Hopefully, I'll be able to find the time to do the install, in a couple of weeks. ;)