Yeah it looks like stevie wonder welded this

 

So since there is a lot of confusion about built motors that do not hold as well of vacuum, I have a question:

My motor idles at 8~10 mmHG. A stock motor idles at 18~20.
Which answer is correct?

A: With vacuum hose connected, set FPR to 33 psi. Disconnect vacuum hose, and my FPR would read approx 37 psi.

B: With vacuum hose disconnected, set FPR to 43 psi. Connect vacuum hose, and FPR reads approx 39 psi.

Thanks in advance

 

Answer C is correct.

A and B are both wrong.

 

Well what the **** dude, can you ever ****ing explain yourself. WHy is it so hard for you to be a decent guy on this board. Help us for once, ****ing understand what your saying.

 

First of all, you have to be at sea level.
If you're at high altitude, the numbers need adjusting, depending on how you're doing the measuring.

With a stock pump and FPR, you can jump the pump (no need to run the engine), it should read about 43 PSI with the resistor in circuit.
The easy way would be to find the pump test connector and jump it with 12v from the battery. It'll be 12 ish volts (key off and pump resistor not in circuit), not 13 or 14 so will outflow the reg a bit but it'll still settle at 42 to 43 when off.
When you shut down the pump, it should hold that 43 PSI, maybe 1 PSI less? So maybe 42 PSI.......it should hold that for weeks without leaking down.


If it passes that test (same goes for an aftermarket FPR), you can go onto the next test which requires vacuum.
You can either run the engine assuming it pulls the correct vacuum or you can use a hand held vacuum tester/ pump. You should see 33 PSI, you then shut it off (maintaining the vac) and the pressure should remain at 33 PSI or maybe 1 PSI less ........so 32 PSI would be correct.




The way to set the pressure is with zero flow and when there IS flow , it's still within spec.
If there's TOO MUCH FLOW, then the numbers go up and it's out of spec.





Going up in altitude complicates things due to less air pressure so I won't go into it.


If your car won't idle with sufficient vac, there's something wrong with it. Gauge broken?, cams installed wrong? AFR wrong? timing wrong?
Yes, hot cams will idle with a bit less vac but only a bit less.
But you're at high altitude?


Most aftermarket FPRs are junk and can't flow any more than stock ones.
Not only that but the valves tend to leak so they bleed down within minutes of shutting off, you then have problems restarting, more cranking required.

 

Ok, I am kind of following.

I lose pressure the minute the car is off.

I have a Walbro 450, hard wired, with dual relay to control low and high voltage. Pressure on AEM regulator holds solid at idle, after driving and boost pulls, come back to idle and it holds all day long as well.

I have FIC 1350 Injectors. I can get the car to idle with 39 psi, vacuum line connected, with Size scaled to 1366 real world or 1170 Mitsubishi scaling, latency at 14V is 1.104, trims are damn near perfect at -1% for both cruise and idle. I have tested repeatedly for the last 3 days these settings, and they are the same tried and true. I can hold 13.9~14.1 volt all day long. I lose fueling in boost. Running 25 psi DD and 30 psi on race map. My car idles at 10 inHG cold, and 12 inHG warm, all day long, has done this for two years, since full build. Even before 7 years ago with same cams it idled at 12 inHG cold, and fluctuated from 12~14 when warm.

My elevation is 12.5 or 4200 FT.

Where do I go from here?

 

So if I do the math, 14.7 atmosphere, idle set to 43.5 vacuum disconnected, nets a 10 psi drop when it is connected to get 33 psi base idle, correct? Stock Evo's idle at 18~20 inHG. So that is .67 bar, plus 2.33 Bar equals 3 Bar or 43.5 psi... So at my altitude in the equation, 12.5 is a decrease of 15% atmosphere right off the bat. I idle at 12 inHG when warm. 12 inHG warm equals .4 Bar. SO lets set up the equation of 43.5(.85 account of decrease in atmosphere) = 36.975 psi or 2.55 BAR. It looks really easy, add my .4 Bar and you have 3 Bars once again. What am i missing. If I set base idle with vacuum disconnected to 37 psi, and then add vacuum line, it will show 33psi on the gauge...

Suggestions, or do you know a better formula?

 

Modified car always have much more than just one problem.
First of all you need to fix the leak (AEM is the crappiest of the crappiest low quality aftermarket junk and can't handle the flow). Check that first by pinching the return line (after you turn off the engine, while it's leaking down).
With an atmospheric pressure of 12.5 PSI , the engine should be able to suck 2/3 atmosphere of vacuum (8.3 PSI) so you'd expect about 35 PSI (43.5 - 8.3) on the gauge at idle.


So while it's idling, pinch the vac line at the FPR (that retains the vac at the FPR) then shut it off and read the pressure.
When you've fixed the leak.

 

Ok, so My rail is holding 40 psi now, when car is off. I verified this. My AEM unit is actually holding, the gauge just doesn't work when car is off, but it holds pressure. I used a different gauge to read, and then decided to pull the line, it hissed loudly and then fuel squirted everywhere.

SO, 12.5 psi at 4200 feet is 15% less than 14.7 psi at sea level. I see you account for this, but I don't see you accounting for my 12 inHG at idle of vacuum, where a completely stock car will idle at 18~20 inHG. Also, speaking to several car shops the last two days, they say at this altitude, they have seen cars that have factory 20 in HG vacuum at sea level, only idle at 16 inHG at this altitude. THese are brand new cars. So help me factor all this together, please.

 

So it's 3 PSI too low?....no, more like 2 PSI.
You'd expect about 42 at no flow and 43.5 at full flow.


Hot cams always have a bit less vac at normal idle speed but not much less. When you increase the idle speed you get the vac back, or most of it.

You also lose vac at idle with a bad tune, as in the AFR is too rich or too lean.



To eliminate those variables in order to test the FPR.....as I posted elsewhere........measure the pressure at idle with the vac line ON.
Then pinch the vac line to retain vac in the FPR, then shut off the engine and note the difference in pressure.

"Outflow " of the FPR happens when there's too much flow for it.
That shows up as an excessive pressure difference comparing full flow to no flow.


That's why there's a variance in the factory specs for fuel pressure. The no flow number is the lower one and the full flow spec is the higher one.

 

Fuel pressure is constant and set 43.5 no vacuum, and run 39.5 with vacuum. Holds strong, no bouncing or playing, and holds in boost.

So here’s the data. It has been 60 Degrees F here for last 3 hours, and my tuning routine has been to drive 20 miles west into the wind, monitoring MAF Heat, and then stopping and idling with hood/bonnet open to maintain cool air at idle. Then driving 20 miles to the east with wind at my back. Same stop, lift hood, to maintain temps.

Trims at Idle at 60 degrees F are -1.13% and hold firm, they fluctuate +/- about .5% but then settle right back down to that number. And I verified it with 4 laps of my tuning layout. They always settle right back down.

Trims at Cruise are at -1.56% and fluctuate +/-1% on that, verified the same way, and then settle back on that number. I get the same numbers in various gears, various loads, all in cruise loads and MAF HZ.

Ok, since my update to my pump -->https://www.evolutionm.net/forums/ev...l#post11767178
My pressure has increased and is staying stable. You can read the mechanical updates I did to my hanger and sending unit.

In doing this, my warm idle is now up to 12~14 inHG at idle. SOlid 12, but bounces to 14 randomly, but more often then before. I also have idle target at 975, and it fluctuates between 960 and 1050. I checked pressure several times, and it holds solid between 39~40, after various cruises and idles, and boost pulls.

Did this, and it now holds at about 41 psi.

Not tracking, but, next question would be, how do I fix? THere are 3 different sizes of return cylinders that are interchangeable in the AEM FPR. I have the largest diameter one in there, should I go back to the smallest?

Thanks so far.

 

Yes, I had a feeling there were 3 different valve sizes for the AEM FPR?

Use the biggest one.
Gives the most flow.


But they're still crap.