8 to 10 psi
06-06-2005, 04:48 PM
#1
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8 to 10 psi
ok i am planning on boosting somewhere in the range of 8 to 10 psi to my understanding there are three ways to increase fuel, fuel pressure, injector size, and duty cycle, i was wondering if 8 to 10 psi could be accomplished on the stock injectors without having to worry about injector failure. i know that i can use a fmu to increase fuel pressure with boost but will this work and be as effective as larger injectors? i mean i guess i just shouldnt try to be cheap and try to find out a way to get out of having to buy a set of 600 dollar injectors, but if there is a way to do it without increasing the possibility of injector failure tremendously, that would save me from spending money i dont have right now.
06-06-2005, 05:32 PM
#2
The way i understand it is Duty cycle is just a percentage of how much of the injectors maximum potential workload is being done. Example is a injector is at 80% duty cycle, this means that the injector is spraying 80% of the maximum amount of fuel it can spray.
You don't need larger injectors at 8 to 10 psi. I ran a 8:1 FMU on 10 psi for 1 year and had no problems what so ever. However running a FMU is a very crude and IMO ghetto rig way of tunning. It is hard to get a good tune using a FMU. I went the expensive route and went with the 510cc Power Enterprise injectors(listed for the 350z which uses the same injector as our car) and the Greddy emanage w/ the support tool and injector harness. I also went w/ the walboro fuel pump and the SARD FPR. I got lucky and found the Power Enterprise injectors for 550 shipped on ebay, but they usually go for $800-900 new. So total you are looking at about $1,500+ tunning expenses if done by a shop. Not cheap but once you take this step your options on boost and tunning become less limited incase you get a little boost hungry
You don't need larger injectors at 8 to 10 psi. I ran a 8:1 FMU on 10 psi for 1 year and had no problems what so ever. However running a FMU is a very crude and IMO ghetto rig way of tunning. It is hard to get a good tune using a FMU. I went the expensive route and went with the 510cc Power Enterprise injectors(listed for the 350z which uses the same injector as our car) and the Greddy emanage w/ the support tool and injector harness. I also went w/ the walboro fuel pump and the SARD FPR. I got lucky and found the Power Enterprise injectors for 550 shipped on ebay, but they usually go for $800-900 new. So total you are looking at about $1,500+ tunning expenses if done by a shop. Not cheap but once you take this step your options on boost and tunning become less limited incase you get a little boost hungry
06-06-2005, 05:38 PM
#3
IMHO, if you are only staying in that boost range on the V2 using a 3.25" pulley... just get a Walbro GS342 pump and an adjustable FPR...
It may be crude but it works... I've been running a 3.12" pulley on stock injectors with the above setup for over 2 years w/o any problems. I do use a J&S Ultrasafegard and bored out TB, though the J&S rarely intervenes.
What it really comes down to is how much are you're willing to spend to "optimize" your setup... More stuff can equal more problems... simple is good... simple can work surprisingly well.
It may be crude but it works... I've been running a 3.12" pulley on stock injectors with the above setup for over 2 years w/o any problems. I do use a J&S Ultrasafegard and bored out TB, though the J&S rarely intervenes.
What it really comes down to is how much are you're willing to spend to "optimize" your setup... More stuff can equal more problems... simple is good... simple can work surprisingly well.
06-06-2005, 06:53 PM
#5
my fault, I misunderstood what you were asking. Thanks for the pm, and I unlocked the thread.
AND to help answer your question.....
100% IDC is bad. We know this. The "standard" answer for "safe" IDC is 80%. RC enginerring uses this, along woth several other Injector companies.
A good worksheet is http://www.rceng.com/technical.htm#WORKSHEET
You can put in HP figures and find the best injector solution for you.
NOW.. the Fuel Injector Pressure debate...
IIRC the 5th gen has a lower max fuel pressure at the injector than the 4th gen. I may be incorrect. IIRC the max FP you want is 100psi, that's HI.
At that point I would ge bigger injectors. Hope this helps and my bad
AND to help answer your question.....
100% IDC is bad. We know this. The "standard" answer for "safe" IDC is 80%. RC enginerring uses this, along woth several other Injector companies.
A good worksheet is http://www.rceng.com/technical.htm#WORKSHEET
You can put in HP figures and find the best injector solution for you.
NOW.. the Fuel Injector Pressure debate...
IIRC the 5th gen has a lower max fuel pressure at the injector than the 4th gen. I may be incorrect. IIRC the max FP you want is 100psi, that's HI.
At that point I would ge bigger injectors. Hope this helps and my bad
06-08-2005, 05:31 PM
#7
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Originally Posted by Chunger
IMHO, if you are only staying in that boost range on the V2 using a 3.25" pulley... just get a Walbro GS342 pump and an adjustable FPR...
It may be crude but it works... I've been running a 3.12" pulley on stock injectors with the above setup for over 2 years w/o any problems. I do use a J&S Ultrasafegard and bored out TB, though the J&S rarely intervenes.
What it really comes down to is how much are you're willing to spend to "optimize" your setup... More stuff can equal more problems... simple is good... simple can work surprisingly well.
It may be crude but it works... I've been running a 3.12" pulley on stock injectors with the above setup for over 2 years w/o any problems. I do use a J&S Ultrasafegard and bored out TB, though the J&S rarely intervenes.
What it really comes down to is how much are you're willing to spend to "optimize" your setup... More stuff can equal more problems... simple is good... simple can work surprisingly well.
I was running the 3.125" pulley and getting about 300whp.
I didn't even bother getting the Walbro pump until almost 7-8 months after running it this way. Once I got the Walbro, I could disconnect the auxilliary pump...
Bottom line is, even though some people consider the above setup ghetto rigged, it is safe and reliable and costs a whole lot less than buying new injectors and then investing in some type of AFC...
06-08-2005, 05:36 PM
#8
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all information is greatly appreciated, i think that i will go with the fmu seeing as that i have emanage it will save me a good amount of money right now but i will probably go with larger injectors somewhere down the line, my car is also turbo not supercharged, but the information is very useable thanks!
06-08-2005, 06:01 PM
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Originally Posted by midnightmax01
one question though, at 10 psi of boost and stock injectors, what size fmu disc should i go with and what kind of fuel pressure will i be looking at?
don't know what my pressure was... didn't have a fp gauge back then...
06-09-2005, 08:12 AM
#12
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Originally Posted by midnightmax01
one question though, at 10 psi of boost and stock injectors, what size fmu disc should i go with and what kind of fuel pressure will i be looking at?
FMU's are not a bad fuel management tool for lower boost levels. But 10lbs of turbo boost on a maxima requires more than an FMU to run properly and be reliable.
Remeber guys, he is turbo not SC.
06-09-2005, 09:25 AM
#13
Given that it's a TURBO.... and that peak boost is maintain throughout a RPM range... I would get the larger injectors (etc)... I was only referring to a Vortech setup where peak boost is at redline...
06-09-2005, 10:13 AM
#14
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You will not be able to boost at 10psi with an FMU. Way, way too much fuel pressure. With my 4th gen, My injectors are maxed out and I am seeing close to 90psi of FP @ 5-5.5psi. You would be at or above 100 psi of FP tyring to use an FMU at 10 psi. I WOULD NOT TRY IT.
allen
06-09-2005, 10:24 AM
#15
It all depends on your willingness to risk blowing your motor.
SCers especially on 5th gens that have 290cc vs. 4th gen 240cc-260cc injectors can get away with a bit more. However, turbos make power in the midrange vs. SCs at redline.
Since you're turbo, I'd just keep the boost low until you're ready to pony up for injectors and toss the FMU.
Where did you get $600 for injectors? Which ones? RCs?
SCers especially on 5th gens that have 290cc vs. 4th gen 240cc-260cc injectors can get away with a bit more. However, turbos make power in the midrange vs. SCs at redline.
Since you're turbo, I'd just keep the boost low until you're ready to pony up for injectors and toss the FMU.
Where did you get $600 for injectors? Which ones? RCs?
06-09-2005, 11:01 AM
#16
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Originally Posted by allen222
That's absolutely just not true my friend. I ran 9 psi w/a 7:1 FMU on my 240sx for a long time w/ no problems what so ever. The amount of fuel pressure increase from an FMU depends entirely on what ratio of FMU you buy. A 12:1 ratio FMU would have made my maximum fuel pressure about 153 psi, I ran a 7:1 which made it about 108 psi (figuring on 45psi base). That's pretty high but like I said, no problems.
allen
allen
Running very high fuel pressue like that is bad for many reasons.
Injector lag time is effected.
The injector can actually over heat, although side feed are not as bad as top feed.
The injector can leak
O-rings can leak
Is hard on the fuel pump
Pulse width can become erradic
But the most dangersous part IMO, is that when your running 100% injector duty cycle is you have no head room. If you tune your car when it is hot out and then you find yourself boosting in 50 degree weather you may be seeing as much as 20hp more. If your injectors are maxed out your ECU cannot compensate via your MAF. The car will start to run lean.
For a turbo maxima to run 10lbs and have a safe AF (11:1) using stock injectors and an FMU it would need at least a 10:1 disk. This would put you close to 120psi of fuel pressure.
06-09-2005, 04:03 PM
#18
1)Power Enterprise 380cc or 510cc are Plug-N-Play, ie no splicing or spacers.
2)RC Engineering makes 370cc on up that require you to splice on electrical pigtails and use thicker fuel rail spacers.
3)Nismo makes a 480cc PNP, but their pretty much impossible to find/get.
2)RC Engineering makes 370cc on up that require you to splice on electrical pigtails and use thicker fuel rail spacers.
3)Nismo makes a 480cc PNP, but their pretty much impossible to find/get.
06-10-2005, 07:33 AM
#21
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Originally Posted by MaxInProgress
I got the nismo 550cc and im gonna start off not intercooled, so a 8:1 fmu disk would be siffice?
Don't you have a JWT ECU? If so then no need for an FMU as long as your using the correct size injector for which the ECU is programed for.
Non-intercooled? Now that I have had a chance to drive my car is summer heat there is no way I would run w/o an intercooler, even at low boost levels. The only thing saving me is my intercooler. You really have to see for yourself what type of heat is gonna be generated, it is pretty crazy.
06-10-2005, 08:22 AM
#22
Yeah i got the jwt ecu programmed for the 555 injectors. Yeah so im gonna throw the idea of going non intercooled out. You just varyfied what I didnt wanna hear lol. Thanks for the advice. There goes more money.
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