underscore
Well-known member
I'm not sure where the best spot to tap in is, I'm just hunting for options to add an easy way to drain bad fuel without risking a fuel leak either.
Are the running numbers with the vacuum hose still attached to the fpr? When at vacuum, the fuel should have less pressure than the "base" pressure. Base pressure is whatever the fuel pressure is when the pump is in high-voltage mode and when the FPR doesn't have any vacuum applied to it.Roreri":2ks666xc said:Ignition to ON position, but engine off: 33-38psi--I do observe this range when starting the car.
FP and B+ jumped Ignition to ON, but engine off: 33-38psi
Idle: 27-31psi, or 28-30psi--I observe 34psi, which is a little high. Upgraded fuel pump? Something else?
"Stock Fuel Pressure" (while under load?): 40-42.5psi
"pump running full blast and the engine off (no vacuum on the regulator)": 40-43psi
I'll check the base fuel pressure with FP +B and ignition to ON tomorrow morning.
ChrisD":2ks666xc said:Here is his opinion on Fuel Pressure: "It is VERY important to calculate fuel pressure by using base FP + boost pressure. Both combined contribute to pressure in the fuel rail due to the 1:1 FPR."
Roreri":2ks666xc said:Here is a representative full load onramp run: https://youtu.be/Sr-txGnDAgE
Roreri":2ks666xc said:US 93 octane E10 fuel is almost certainly sucking for the JDM ECU which is probably always asking in its silent little digital Japanese voice: "Why you cheap out on gas, asshole?"
Roreri":2fyk69q3 said:I took the Lorelei on a number of loops onto the expressway and off and back through the neighborhood, running on stock boost max 9psi. I gave it a number of full load onramp accelerations and some good load on the expressway. Did some video recording so I could analyze afterwards--too many gauges to look at all at once. My findings were as follows: 32psi at idle, 40psi at load, up to 45psi max.
This is lower that what grip-addict posted should be observed:
"At full vacuum, 30-32 something-ish psi fuel pressure
At 0 bar boost, 42-44ish fuel pressure (please review bgb for exactly numbers)
At 14.7 psi boost, 58ish psi fuel pressure.
1:1 is the law of the land."
Performance was generally good up through 9psi. Air-fuel ratio was properly rich under load. One time, I experienced dropout, while at full load--wasn't recording then so I don't know what exactly was going on, but I'm suspecting fuel starvation. I think I should be seeing above 50psi fuel pressure at 9psi boost.
Roreri":2fyk69q3 said:If you were to get a passthru Banjo bolt then attach a male to male 1/8” NPT fitting and rubber hose to the top of it and run it down, you could probably do it that way. In my case that would not work as the fuel system does not pressurize when the key is turned to the ON position. Perhaps a JDM ECU peculiarity.
grip-addict":2fyk69q3 said:Actually, down this thought process, do you have an air compressor? You could manipulate the FPR by putting varying pressures on it and seeing how the fuel pressure reacts. Maybe your fuel pressure DOES get to the target but it takes a while to get there. A steady-state amount of air pressure would help you determine that.
Roreri":2fyk69q3 said:Fuel System Flowchart (Check for Confirmation):
I think the fuel system is set up like this:
Tank-->Sender to Fuel Gauge
Pump
Fuel Line From Tank-->Charcoal Canister
Fuel Filter-->Fuel Pressure Gauge
Fuel Rail
Injectors-->Cylinders
Fuel Pressure Regulator
Return Line to Tank
2Gen 3S-GTE Fuel Pressure:
Various forum discussions I've found regarding the 2Gen 3S-GTE say stuff like:
Ignition to ON position, but engine off: 33-38psi--I do observe this range when starting the car.
FP and B+ jumped Ignition to ON, but engine off: 33-38psi
Idle: 27-31psi, or 28-30psi--I observe 34psi, which is a little high. Upgraded fuel pump? Something else?
"Stock Fuel Pressure" (while under load?): 40-42.5psi
"pump running full blast and the engine off (no vacuum on the regulator)": 40-43psi
I'll check the base fuel pressure with FP +B and ignition to ON tomorrow morning.
Heinlen fan?Roreri":2fyk69q3 said:Fuel System Limitations:
So, in my case: If my max fuel pressure is 42.5psi, then base of 34psi + 8.5psi boost is my limit. So...thought here...I'm only seeing 42.5 because I'm only achieving that much boost. If I achieve more, I'll see more pressure up to the fuel pump limit and the injector duty cycle. That might be DUH to the wise, but I'm just now grokking these concepts with the aid of instrumentation.
This is purely conjecture on my part, so definitely not gospel. But food for thought.Roreri":2fyk69q3 said:This observation from ChrisD is particularly telling because it seems to speak directly to my observations: "I think most people can run 12-14psi safely on the stock turbo, as long as everything is in good condition and they *pay attention* to how their car responds to the boost. If there is anything like hesitation, loss of power like its being "held back", stumbling, etc., you might not be able to run as much power."
So, whatever the case, it seems evident that I'm outrunning my fuel pump or injectors when I try to go for the higher boost levels. The Blitz Twin SBC can boost beyond the setup's limitations. I observe plenty rich conditions. Low 11s under full load at up to 8.25psi stock boost (sometimes it will give me .64kg/cm2--9psi).
Roreri":2fyk69q3 said:Full rich (11.3:1) under stock 8.25psi boost at 5000rpm. 42.5psi fuel pressure. I think my base is 34psi. That's what it sits at on the gauge at idle. Which suggests something, because all the discussions seem to center around 30psi as the base for a 2Gen 3S-GTE. Upgraded fuel pump? Different FPR?
I could perhaps adjust the "high" boost setting (the Blitz Twin SBC has a dial knob for the "low band" and "high band") down to like 12psi and see how it does.
US 93 octane E10 fuel is almost certainly sucking for the JDM ECU which is probably always asking in its silent little digital Japanese voice: "Why you cheap out on gas, asshole?"
Roreri":2fyk69q3 said:Water/Meth Injection
Look...any time I think about being able to say "This car is on meth" with a straight face it makes me giggle. There's gotta be a bumper sticker. Plus, for whatever reason I'm not attracted to an FMIC. So, water/meth injection to achieve proper octane and correct IATs seems like a fine approach to mitigate U.S. gas octane deficiencies and get the most that I want out of this car: Stable 14psi boost, which is the limit of turbo efficiency and probably coming close to the advisable limit for stock 30 year old internals.
I wanted to know more. So I watched this: https://youtu.be/SgzDRaa4xLc
My takeaways: Water/Meth injection lowers charge temperatures and increases octane making higher boost possible. But it riches out the air:fuel ratio overmuch, sapping power. So, a tune might be necessary, to take fuel out to compensate for that. Might be possible to spray a little water/meth and get away with not having to do a tune, though. My goals are modest: Stable 14psi boost, elimination of possibility of detonation.
Holy crap. I totally forgot he had an ATA intercooler.....underscore":cimcgvf2 said:Especially since you're already trying to work around having a top mount ATA intercooler with an RC hood.
Personally I'd hunt down that fuel leak first, if nothing else just for safety. I'm assuming if it's leaking gas when full it may be leaking fumes at all times which can be dangerous.
Also don't forget that the stock fuel cut is 14.7psi, so if you're setting boost north of 12-13psi (factoring in tolerances of equipment) that's something to be aware of.
Not a necessary mod. I don't even know if it's worth it to do it. How it works is the relay normally routes power for the fuel pump through a resistor, so the pump gets less voltage, and works less, delivers less fuel flow (pressure should still be the same because it's governed by the pressure regulator, not the pump). Less flow does deliver slightly less fuel to the injector (Flow and pressure are related, but different. Topic for another discussion. ). Slightly better gas mileage and less wear on the pump.Roreri":8uvp97u9 said:Thanks for the information about the 5SFE Fuel Pump relay jumper. It definitely seems to be a good idea at some point. Any time I can replace a vulnerable and aged relay with a dead simple jumper and get the same or better function I'm interested. I don't want to be lazy but is there a part number I should be looking for? I think it might be called a Sub Fan Relay? Alternately, I think I could just paperclip jump FP and +B if I wanted to be cheap about it.
underscore":3c8hevu7 said:You can just make a jumper out of a couple of male spade terminals and some wire. I wouldn't use a paperclip for that one because I believe it's all the power for the fuel pump running through there, not just a trigger wire. Why the fuel pump power takes such a scenic route I don't know.
I don't know the exact name for the 5SFE jumper but not all of them have it. I was going to swipe it from my old 92 GTS but it had a relay there so it might just be a 90-91 thing?
alltracman78":1fsd84g3 said:underscore":1fsd84g3 said:You can just make a jumper out of a couple of male spade terminals and some wire. I wouldn't use a paperclip for that one because I believe it's all the power for the fuel pump running through there, not just a trigger wire. Why the fuel pump power takes such a scenic route I don't know.
I don't know the exact name for the 5SFE jumper but not all of them have it. I was going to swipe it from my old 92 GTS but it had a relay there so it might just be a 90-91 thing?
FP in the DIAG box isn't a trigger wire.
alltracman78":1fsd84g3 said:The normal wiring goes the senic route for safety reasons.
Sorry, read too fast.underscore":2bqrem7r said:alltracman78":2bqrem7r said:underscore":2bqrem7r said:You can just make a jumper out of a couple of male spade terminals and some wire. I wouldn't use a paperclip for that one because I believe it's all the power for the fuel pump running through there, not just a trigger wire. Why the fuel pump power takes such a scenic route I don't know.
I don't know the exact name for the 5SFE jumper but not all of them have it. I was going to swipe it from my old 92 GTS but it had a relay there so it might just be a 90-91 thing?
FP in the DIAG box isn't a trigger wire.
That's what I said, though I'm talking about the fuel pump relay up by the alternator.
Didn't give that clear an answer. Too much typing for me.underscore":2bqrem7r said:alltracman78":2bqrem7r said:The normal wiring goes the senic route for safety reasons.
I'm struggling to wrap my head around how having the fuel pump wiring go from the left rear corner of the engine bay, to the right front corner of the engine bay, to the left front corner of the engine bay, back to the right front corner of the engine bay, and then to the fuel pump makes it any safer. I guess if you have a hard enough crash on either front corner you'll damage the wiring and turn off the pump even more?