Why You Need A Fuel Pressure Gauge On The Dash
 

For the second time in about 13 years, my Denso fuel pump started loosing the ability to maintenance pressure at the higher rpms for boost over 14 psi.

The first time I did not have WI and the Denso was the first upgrade from them for the FD. I noticed knock levels were increasing but safe at the same time fuel pressure was dropping for the higher rpms.

This time with WI, knock was the same but fuel pressure was dropping off again but I was at 17 psi boost. Base FP is 40, Around 6000 rpm the fuel pressure dropped from 57 to 50.

The Aeromotive Stealth pump fixed the problem. No more Denso pumps for me.

While I was at it, I installed gauge 10 new internal wiring for the pump.

Without the fuel pressure gauge, I would not know the pump was wearing out.
Safety First!

or just a wideband. i do run an electronic fuel pressure gauge also. ive never had a pump go bad, but a FPR crapped out on me. at the time i didnt have a fuel pressure gauge, but could tell something was wrong when it idled in the 10's AFR and leaned out to 13's in boost

And if you have basically any other ECU other than a PFC you can wire the gauge output into the ECU and have the ecu automatically take protective measures if the fuel pressure drops below your predetermined safe levels.

I'm a huge fan of a fuel pressure gage and consider it second to boost as a must-have indicator of engine system health (oil pressure isn't even close). Especially if you retain the unreliable stock fuel pump resistor relay. The most underestimated gage period.

RENESISFD makes an interesting point about using the ECU to elicit alarms/warnings/shutdowns, however for most of us who use a boost dependent FPR, this strategy is infeasible (unless you own a Motec apparently). This argues strongly for running a simplified fixed pressure regulator at ~60psi base fuel pressure, although I've yet to implement it.

If you run more than one boost level, then you probably only can have the fuelsafe for the highest boost you run.

My EBC has 4 boost settings. I do have the four top PFC boost rows set for them. I actually tune my total map. I run WI but only the highest boost level is AFR tuned with the water.
The three lower boost settings are AFR tuned without WI.

Haltech

No. Failsafes work off the pressure delta of MAP versus fuel pressure. The ECU sees more boost pressure and expects more fuel pressure. If it doesn't see it, various programmable levels of failsafes are implemented.

Even the likes of AEM will have these features... AEM already offers it on their infinity ECU's and in an update coming early January, their older AEM Tuner software is getting Fuel/Oil pressure protection, O2 lean protection and improvments to the existing knock control.

I would hope you tune the entire map...

In addition to the failsafe's mentioned before, most ECU's today have excellent boost control stragities and will allow you to add an input to the ECU that can lower boost if the WI tank low level switch is activated.

And they are not all expensive like Motec, there are many plug and play options that can be had for right around the cost of a new PFC.

Here is a screen shot of what the engine protection looks like. The reason it is red is because Haltech knows that I do not have a fuel pressure input selected so my settings would be useless here. You can see on the right as C.ludwig mentioned the fuel pressure works off of delta pressure not overall fuel pressure. Obviously that minimum time would need to be changed. IMO, people running single turbo cars should start to open their eyes to other ECU's other than the PFC. Things like this can save an engine. People can sell their PFC and spend another $800-900 on an ECU that is plug and play just like the PFC but have much better control over their engine functions. The PFC is dead for single or non-sequential cars IMO.


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That is good. Back in 1999 all we had that was easily useable was the PFC.

noticed the same issue with the Denso pumps. when they die they don't just quit, they have a tendency to want to take the engine with them on the way out.

doubt i will ever trust a Denso above cosmo TT OE level again, junk.

Must datalog fuel pressure, not only afr, it was easy to setup for the power fc with electronic fuel pressure sensor.

That is certainly true :lol: Back in 1999 I was in fourth grade. But it is now 2012.

datalogging can surely point you to the reasons for an engine failure but it won't protect you from it.

wideband gauges are nice, but usually by the time you see the AFRs spiking it's already too late.

thanks, now i feel old. again.

Can you elaborate, what pumps are on a cosmo TT oe level? And is a cosmo OE still available?

my Denso Cosmo is 13 years old and still running fine. it does get plus 20% additional V in boost thanks to my Kenne Bell Boost A Pump. 40,000 miles of running fine.

i ran 25 psi MGP at 43.5 static this year and it put out 68.5 psi on the dot. maybe your pump was built friday afternoon:)

this is an important thread.

as Tom indicates, knowing fuel pressure under boost is essential.

watch a gauge
log it
whatever.

but know your pressure in boost.

there are many things that can effect fuel pressure, all negatively, and you don't have to lose all pressure to lose ALL of your engine.

howard

supra TT is the offender i'm referring to, at least the more current ones seem to fail slowly, especially if you push more voltage to them like Howard's Boost a Pump but the cosmo pump seems to handle it ok, probably superior winding process on the older pumps versus newer.

no clue if the Cosmo pumps are still available, if they still manufacture them by chance i probably wouldn't trust one. it would have to be a new old stock pump.


it's easy to say add a guage but in all honesty there are a number of important gauges, and you won't be watching all of them all of the time. best bet is to get a warning threshold type gauge with an alarm. except for many gauges they will fluctuate in and out of warning range normally, so wouldn't really help in that respect with the exception of EGT and ECT. overbuild the engine to hopefully take a pop or 2 to the point that you notice a problem as it arises and can diagnose it.

i hate driving street driven cars that have a thousand gauges and idiot lights, they still wind up eating motors eventually anyways no matter how diligent the owner's are.

I had a supra pump and was loosing fuel pressure. The result was a blown engine. Still not 100% sure if the pump was the issue, relay or how it was rewired - I sold the car.

My new car I swapped the supra pump for an aeromotive 340, and that pump died while I was sitting idling. I had only used it for a few thousand kilometers too. Now I got a new 340 pump.

Any pump can crap out on you. A safety system, and gauges monitoring the FP would be helpful.

My main two gauges are a boost gauge on the left side and the fuel pressure gauge to the right of it. Easy to glance at both and know what is happening.

when at full boost who can really look at the road, the tach, and the fuel pressure gauge all at the same time?

driving around normal is one thing, but at full boost im concentrating on shifting and driving

I was gonna say the same thing, especially with 500+ HP, It's dangerous unless in 4th gear on a wide open highway late at night, That's why I would datalog almost every pull on the street.

Unless you've lost traction at 60 mph :)

:) :). Don't forget, you're right foot is your FRIEND and can be regulated!

Chuck,
Great thread. But I need to correct you. Back in 1999 we also had the infamous PFS Purple Peter Motor Eater. :D

Regards,
Crispy
with *THREE* gauges - boost, FP, and....oil temp (for those of us that are comfortable tracking their car in 100degF ambient temps)

Then by your reasoning only stock gauges are good and all others such as boost are useless. It depends on the location.

Center speaker location which still allows forward level sight.
Maybe some of us have faster eyes/brains.

I had one of those before the PFC came out. One day it gave total fuel cut under boost while in the learning mode in third gear. Scared the shit out of me. Then I bought a reprogrammed ecu.

For normal dayly driving you are not going to log all the time.
A quick glance once in a while why accelerating is what I have been talking about, not tuning. Because most likely this type of failure will happen when you are not tuning.

And watch the wideband at the same time haha

This brings us back to ECU's that are not from 1999. My current ECU has internal logging. I have it setup for conditional loop logging. It automatically starts logging every time throttle is greater than 60% (or any variable you like). The loop logging allows the ECU to re-write over itself until I decide to pull a log. So if I do a pull and notice something wrong I always have the data.

I honestly don't know why so many people stick with the PFC for cars other then sequential cars.

If I was still working instead of being retired with a limited budget, I would replace the PFC. But after 20 years of FD ownership, 13 years of PFC without any problems,
you can say "Chuck is stuck in a rut.". So be it, but my car is better overall than most FDs are.

Wow.... so you've been running your current motor for 13 years. How many miles does that equate to Chuck? Has it been trouble free this entire time, or has data logging saved your bacon a few times?

Make up your mind, is it once in a while while accelerating or is it while at full boost?
I said WHILE AT FULL BOOST who can look at everything at the same time.
Of course you can look at anything "once in a while" while at your leisure, at full boost im making sure i shift and i dont crash . Once in a while while accelerating i look at a lot of things

the fuel pressure gauge only verifies your fuel pump, lines, and regulator. A wideband gauge verifies all that and more.. injectors, map sensor, tune, vacuum leaks, etc.

i would rather look at a single gauge that monitors the final product (exhaust AFR). fuel pressure is something you would use for troubleshooting if something went wrong, not as your first indicator. it leaves out a lot of information a wideband can provide

Just a tad over 50100 miles at 350+ whp untill 2005 when i went single to about 400+ whp.

Here is my recent compressions test done with a calibrated electronic tester.
Front Leading Spark Plug: 129.04/125.39/124.17
Rear Leading Spark Plug: 125.39/121.74/121.74

Engine built by me but rotating parts balanced by Mazda Trix.

The problem is that different cars react differently.

My home built balanced engine with stock ports but port matched and enlarged port runners, port matched manifolds, moded TB, full supporting mods,
etc with an A-Spec GT35R 1.06 kit will hit full boost before 4000 rpm even at 17 psi boost. It also has WI.

Even when I floor the throttle in 2nd or 3rd gear it will hit full boost by 3600 - 4000rpms and hold boost flat all the way to redline.
Thus my max boost is the same as acceleration.
What is so difficult to understand about that?
It was above 6000 rpm that fuel pressure was dropping off.


Can you handle that?

Relax man all i was saying was at full boost who can look at all that, was just making a comment talking about the subject i didnt say your idea was bad or to explain everything. I didnt talk shit to you but You are the one who is saying your eyes and brain are faster which obviously implies i am slow.

Merry christmas to you

"Here is a screen shot of what the engine protection looks like. The reason it is red is because Haltech knows that I do not have a fuel pressure input selected so my settings would be useless here. You can see on the right as C.ludwig mentioned the fuel pressure works off of delta pressure not overall fuel pressure."

post ten caught my eye. in a (more) perfect world the ECU would sense a separation of the fuel pressure from the boost pressure and immediately make an engine saving adjustment.

that's just what post ten is about. very impressive, good job Haltech.

i checked w ViPEC and they alerted me to a parameter entitled "Differential Fuel Pressure."

you simply select it, enter whatever differential pressure value you wish and the computer will react if triggered by switching to another 440 cell ignition map, fuel map or open the WG.

a valuable feature.

howard