Ok, I'm hearing different things from org members on what to expect from my gauges. At idle with the engine at normal operating temperature, are my gauges suppose to read the following, 20hg for boost (I don't even know what that unit of measure stands for), and 30psi for fuel pressure? Someone said thats normal, but I need a 2nd opinion. Also, let's say I consistently run 9psi at redline in 3rd gear (auto) which is around 125mph, 10psi at 130mph still in 3rd gear but deep in redline, I never had a chance to read my fiel pressure at that point, where should it be at 9-10psi so next time I can look out for it? Thanks.

-Ben

 

your boost guage is fine.

 

Ben I have read at redline your fuel pressure should be at least 45psi. At idle 30psi is just fine also. As for your boost gauge, it's perfect.

 

Hmmm...I'm just getting 10Hg Boost most of the time. I've noticed after a few spirited romps that it goes up to 15Hg. I guess with everyone getting 20Hg my setup isn't correct?
Hope to have my Y-pipe and EGT installed this Saturday.

 

you've got a nasty vacuum leak somewhere... mine is generally at 20, but wanders between 18-20 after driving

 

Factory spec for Idle is between 17-21 Hg for Vaccuum.

Fuel pressure at idle is usually between 30-35 PSI, outside temp plays a role in this as well, when it gets warm out expect that number to be closer to 35 PSI

At full boost the FP will follow Vortechs formula

FMU Disc ratio * PSI of boost + 1/2 of base fuel pressure. (Keep in mind Base FP on a 4th gen is 34PSI)

So let's say you have a maxima with a 6:1 FMU disc, and 10 PSI of boost, the equation would look like this:

6*10+17 = 77PSI

So at 10 PSI of boost you should be seeing ~ 77psi of FP. This will vary a little bit from guage to guage.

 

When you say vacuum leak are you talking about the gauge setup?
Then that must be that kink I put in it.

 

Man, you did the math on that one. I did go for another drive on the highway today to watch the fuel pressure gauge this time and that 77psi you say seems to be exactly where I was when my boost gauge was saying 9psi. Ok, so I assume everything is okay. (knock on wood) Thanks for the useful info guys.

-Ben

 

Jusss doin my job Sir....

 

When you installed the gauge. the tube that comes with the kit for the vacuum line, did you uncoil it and straighten it out?

 

Yup, I uncoiled it and straightened it out, actually I did it too fast and it put a kink in it, so I used some pliers to remove the crimp and installed it like normal with no problems.

 

are you 100% on this?? if so, don't most deal with injector lock at approx 100psi , and anything near or above 90-100+ is dangerous right?

 

If that formula is right, I should be pushing over 100 psi of fp...




hmm i guees i wont be boosting near redline anytime soon

 

The formula is correct it is on Vortech's website.

So yes Hal you would be putting out some insane FP @ 10 PSI

Sexima... What FMU disc do you have?

I would worry @ about 100 PSI.

 

8:1

 

I got a kink after I threaded it down the A post gap and pulled on it. I'm going to pick up a replacement hose after work today. I definitely think its the kink.

 

Daniel,

There are some places that sell it in copper, much harder to kink.

Go for it

just make sure you get a new compression fitting too.

 

So wait... when I had the 3.125 pulley in there doing 11psi with the 8:1 in there that means I was pushing well over 100psi on the injectors.

11x8+17 = 105psi

Wouldnt I be pushing injector lockup everytime I hit 11psi then? I had stock injectors in my 2k1. I know plenty of other people who were running this type of setup and never had any issues of injector lockup.

Is there something im missing? Teach me

 

Yeah I would think you would be at the limit, but my opinion is if it's only for a split second or so you are OK.

Also there have been some members that ran up to 120 PSI fairly often and never locked em up. I guess it's just the luck of the draw, but if you were to do that, and an injector were to fail... you would understand why and deal with the consequences.

 

But the part I lose you on is how is it only for a split second? When you hit 11psi or so at say 4k rpms all the way to 6500, that might be for a good 15seconds on the road on 3rd gear. Or are we talking about it being at 6500 for only a split second? Or is the injector definetely going to fail if I keep it at 6500rpm for a good 20second?

What happens when an injector locks up?
What psi is lockup for stock injectors on a 2k1?
What psi is lockup for say 370cc injectors?

This is really helping btw since Im going to try an alternative method of boosting besides a s/c and want to know if I really need to upgrade the injectors or not. All this disc size on the fmu and these calculations confuse me like crazy. Can never seem to understand certain parts on why it is okay to leave it and others say it is not.....Any info you provide even outside the scope of my questions will be appreciated, im sure others are in my shoes as well

Dixit

 

Dixit,

I think pressure for the most part is going to be the same across the board unless you have a freak car out there that is made to run really high FP. Remember most high HP cars (from the factory) have high CC count injectors to keep the FP low. I still maintain, (but I am no expert) that anything close to or over 100 PSI of FP is too dangerous on any injector until I see solid proof otherwise. When an injector locks up it is no longer spraying fuel into the cylinder. Briguy blew a motor that way.

 

Fuel injectors are simply fast acting solenoids that open a needle valve against the fuel pressure. There is a limit to how much force the solenoid can exert, and if the fuel pressure is high enough the needle valve won't open.

Anybody know the answers to the other two questions? If some people are running 120 psi, then apparently it is at least that high. Better to err on the safe side, though.

 

After replacing the nylon hose with a new nylon hose and rechecking all of the hose fittings I'm still getting around 10Hg. I guess I'd better check the piping connections for leaks.

At least my EGT is reading correctly.