Fuel Injector Chat and Discussion

[Supa Ninja]

Looks I'm going to be make a couple changes to my setup with these findings. I'm going to turn my pressure up to 75psi and the check back to my FPR so that I'm at a constant 75 psi. The pricision injectors didn't like the higher fuel pressure at idle unlike the IDs. Thanks Jay for being the guinea pig. I just replace my OEM so hopefully that will fix the cold start problems (I got the fueling good enough to fire the first try when I was jump starting in the morning).

[Hondata]

Excellent Info. Thanks.

What this shows is that adding the Walbro alone on a returnless fuel system adds only 2-3% additional flow and does not prevent the large pressure drop. It does however set the stage for an increase in fuel pressure.

Math : At WOT 8000 RPM the fuel pressure only increased from 43-45.5 psi. Fuel flow increase = root( 45.5/43). This equates to 2.9 % increase in fueling. You measured a 2% duty cycle drop so the theory fits the observed values.

Be aware that flow volume drops with pressure increase though, so more pressure is not always better. See our tech article on fuel flow vs pressure.

[Supa Ninja]

Flow will be affected by restrictions from the pump to the inj, correct? Since my biggest restriction is the plastic barb on the fuel cage(same spot as the pressure drop). Now I'm running -6an fuel line straight to the rail(with a high flow filter of course) so my lph should be good enough to run the higher fuel pressure, correct?


BTW-big props for giving us live tuning, I figured out how to use it and got my vacuum maps dialed in...quickly.

I'll know tomorrow morning for sure if the cold start is fixed(going to below freezing again)

[Str8JDM]

i want to crush my fuel pressure regulator but not sure how well my 900cc fuel injector clinic injectors will take the high pressure. better to be safe then sorry?

[mucter]

Originally Posted by Supa Ninja

Flow will be affected by restrictions from the pump to the inj, correct? Since my biggest restriction is the plastic barb on the fuel cage(same spot as the pressure drop). Now I'm running -6an fuel line straight to the rail(with a high flow filter of course) so my lph should be good enough to run the higher fuel pressure, correct?


BTW-big props for giving us live tuning, I figured out how to use it and got my vacuum maps dialed in...quickly.

I'll know tomorrow morning for sure if the cold start is fixed(going to below freezing again)

Nick, read the paper that came with the injectors carefully. It mentions how to ideally setup your fuel pressure if you have a fuel return.

Originally Posted by Str8JDM

i want to crush my fuel pressure regulator but not sure how well my 900cc fuel injector clinic injectors will take the high pressure. better to be safe then sorry?

Did your injectors come with any documentation? You might talk to Jotech or try to contant IC directly and ask them. I think the IC injectors are the newer injector body style, they probably do fine with higher pressure. I'm no expert though and you should do some research.

[Str8JDM]

Originally Posted by mucter

Did your injectors come with any documentation? You might talk to Jotech or try to contant IC directly and ask them. I think the IC injectors are the newer injector body style, they probably do fine with higher pressure. I'm no expert though and you should do some research.

no documentation, they look exactly like the IDs and are supposably comparable. ill have to research some

you want to sell your regulator crusher?

[mucter]

PM Jotech, I know he uses IC's a lot. He can probably answer your questions.

[mucter]

Originally Posted by Str8JDM

you want to sell your regulator crusher?

I can't sell it, it's not mine. I'm actually borrowing it from someone else.

[Str8JDM]

Originally Posted by mucter

I can't sell it, it's not mine. I'm actually borrowing it from someone else.

ya im going to need to do the same cuz i dont think they sell them seperate. figure i would ask though

[mucter]

Just find someone with a CT-e charger and PM them about it.

[EvansTuningDotCom]

Above 80 psi or so the internal bypass valve on the walbro pump opens. The flow drops off drastically. You can easily "crush" the bypass valve on the pump in about 30 seconds and get way more output from the pump. This is kinda old news, but a good read: AMS Ultimate Fuel Pump Test - NASIOC

[vtecmike1]

i'm gonna hang out in this thread and start a business charging people to crush regulators lol yay comptech lol

[soxfan143]

Originally Posted by EvansTuningDotCom

Above 80 psi or so the internal bypass valve on the walbro pump opens. The flow drops off drastically. You can easily "crush" the bypass valve on the pump in about 30 seconds and get way more output from the pump. This is kinda old news, but a good read: AMS Ultimate Fuel Pump Test - NASIOC

Interesting. Sounds like a pain in the arse to pull that pump apart to crush the bypass valve inside. But it might be necessary.

[EvansTuningDotCom]

Relief valve is on the top of the pump near the plug connector. Takes 30 seconds to do it. Google walbro relief mod, you'll find pics from DSM forums. I have been doing it for years. It makes a huge difference at high base pressures and high boost pressures.

[soxfan143]

Wow. It IS wicked easy to do. All you do is collapse the relief valve right next to the outlet nozzle. That's awesome!

http://www.driven2modify.com/showthread.php?t=11702

[Str8JDM]

Originally Posted by EvansTuningDotCom

Above 80 psi or so the internal bypass valve on the walbro pump opens. The flow drops off drastically. You can easily "crush" the bypass valve on the pump in about 30 seconds and get way more output from the pump. This is kinda old news, but a good read: AMS Ultimate Fuel Pump Test - NASIOC

80psi is really high, i doubt anybody would get that high on our cars unless its a full blown race car. it has no advantage at anything under 80psi right?

[EvansTuningDotCom]

With a properly crushed FPR and returnless system, you are correct 80-85 psi base pressure wont be reached or maintained. I have noticed that crushing the relief valve seems to make a difference below the point at where it opens up, so in the 65-75 psi range. Its easy to do if you are throwing the pump in there.

When people start doing return style systems on these cars running with 60-70 psi base pressures, yes you'll be in the range of the relief valve opening. The ID injectors do run better at higher pressures, so there is no reason not to have a higher base pressure. It should be noted that the walbro pump is no where near as good as the bosch 044 pump at high pressures. If you guys start pushing your cars hard, with a ton of boost the 044 pumps are the way to go.

On a side note increasing fuel pump voltage has a HUGE effect on output. Going from 12 volt to 14 volt is substantial. Going from 14 volt to 17 volt is a huge step as well. Another interesting read here: Stealth 316 - Fuel Pump Upgrade Guide

[Supa Ninja]

Thanks Jeff I found that dsm forum article(Mike beat me to the punch on posting the link), i'm doing the mod to my spare walbro.

I'm running my returnless at 60 psi, i'll install that modded pump and run 70psi. I also put a check valve to block the vacuum to the reference of the FPR, that will hopefully help with my cold start problems. Seems like the ID's need the higher fuel pressure. BTW I'm trying to run 20 PSI....friggin internal gates(hopefully next week i'll have the part to put my 18psi actuator in, giggity)

I put a new battery in it yesterday but it was in the low 40's this morning and it still wouldn't start till squirted some carb cleaner into a vacuum line. This is getting really old.

Great link evanstuning

[mucter]

Nick, my car starts like a tard too, you're not the only one.

[Supa Ninja]

Originally Posted by mucter

Nick, my car starts like a tard too, you're not the only one.

I'm glad yours is having problems too just kidding.
I'm still trying to sort it out. Mine fires right up if i squirt a little carb cleaner into the vacuum line for the BOV.

Just something else we need to sort out. I am glad that I'm not the only one working on this problem. We need to get Mike to install his ID's too so there will be 3 of us :wigglesmile y: