Author Topic: Home pop testing. Pressure Differential (Read 4600 times)

Jet A · « **on:** August 20, 2008, 09:34:42 pm »

So i am calibrating the injectors while the head is being worked on. I built a pop tester real quick like.

My question is. How much pressure difference between them will really affect the performance. Say one injector is 1800psi and another is 1900 psi (122bar-129bar) Is this enough of a gap to try to get closer?

Also, what are these pumps rated to handle. If one wanted 200 bar, would the pump go that high? I want to experiment with pressure and timing to see if i can get any performance/effeciency out of them. I am hoping to get 155 bar out of my na injectors. Got some more lapping to do on the surfaces anyway.

So far, the only thing i have not messed with on this motor is.....umm....i will get back on this one.

Ohyeah, forgot the pics

How to loosen those stubburn injectors!!! :shock:

Excuse the mess

jimfoo · « **Reply #1 on:** August 20, 2008, 10:00:20 pm »

Quote from: "Jet A"

Also, what are these pumps rated to handle. If one wanted 200 bar, would the pump go that high?

Well, my M-TDI is running 220 bar injectors. Don't forget it takes more power to make more pressure, so if you aren't really gaining anything with higher pressures, you are loosing power trying to make them.

burnt_servo · « **Reply #2 on:** August 20, 2008, 10:26:48 pm »

i've done some engines that before i tore aprt the injectors , where 200 - 300 psi off from each other . and the engine didn't feel right when it was running .

same engine but new injectors within 10 psi of each other and it purrs like a kitten .

you do know that the higher your injector pressure , the more advanced the pump needs to be .....

Turbinepowered · « **Reply #3 on:** August 21, 2008, 02:14:24 am »

With a ~100psi resolution on my own pop tester, I shot for a ~50psi differential between injectors. Looking to get a sharper resolution gauge so I can get them closer together, but for right now the one I have will work.

According to Bentley, each .05mm shim size difference increases breaking pressure by roughly 71psi, and their opening pressure range on stock injectors in a 1.5NA engine was 1706 - 1849PSI, so the pressures could vary by 143PSI.

Jet A · « **Reply #4 on:** August 21, 2008, 10:00:37 am »

Cool info....Looks like we will shoot closer than the 200psi i got. Going to buy a higher res gauge as well. Just bought a chepo to see if the tester would work. Thanks for the info

Im not ACTUALLY looking to do anything nuts with the pressure, just was wondering if increasing the pressure a touch would hurt. But like was mentioned it takes power to make power....

jtanguay · « **Reply #5 on:** August 21, 2008, 10:20:17 am »

the main reason why vw increased the pressure to 155 bar for turbo motors was to "ensure safe fuel atomization." i've heard of 130 bar injectors working just fine in turbo applications, but maybe with super high boost there could be some issues...

burnt_servo · « **Reply #6 on:** August 21, 2008, 10:55:24 am »

jet-a ....

looking at the pic of your gauge , the width of the needle on your gauge is roughly 10 psi .

the first set i did took me 6 hours to get within 10 pounds of each other ..... i've got that down to a couple hours now .

it's finicky work , but the results are worth it .

Smokey Eddy · « **Reply #7 on:** August 24, 2008, 02:58:15 am »

Hey!
I don't have a pop tester. Can someone pm me a link on a build for one?
Also, do you have to buy a shim set? how are you changing the pressues so precisely?
im possative mine are WAY off because i took them apart cleaned them, lapped them and then put them back together with possibly mixed up parts from all four. The car runs fine but has issues starting and idling after startup

Smokey Eddy · « **Reply #8 on:** August 24, 2008, 12:48:02 pm »

Ohhhhhhhhh I see. Yeah that's what i was doing wrong i didnt search for "all terms" so i'd get hundreds of useless posts where someone just mentions "tester" or "pressure"
Thanks!

CoolAirVw · « **Reply #9 on:** August 24, 2008, 06:12:17 pm »

Andrew Libbybapa says....

:lol:

:? :x

:wink: :roll: :cry: :cry: :lol:

Smokey Eddy · « **Reply #10 on:** August 24, 2008, 06:51:20 pm »

hahahah yeah thanks....
i wish i could delete that post :roll:
but i was serious when i said do you have like a massive collection of shims to get it all that precise... i SEARCHED and found shim sets but you must need SO many more to get it that close?

Vincent Waldon · « **Reply #11 on:** August 24, 2008, 07:12:03 pm »

You can lap the base(s) of the spring and dial down to any pressure you want without a massive collection of shims.

To answer your first question, Mr. Search Nazi shoots for 10psi if I recall correctly

!!!!

Smokey Eddy · « **Reply #12 on:** August 24, 2008, 07:19:48 pm »

well im gonna shoot for 10 .....kilopascals!!!! (roughly 1.5 psi

)

Smokey Eddy · « **Reply #13 on:** August 24, 2008, 07:33:10 pm »

I was totally kidding about the 10 kilopascals thing....
but yeah im sure you can get close with tightening the injectors together as long as they don't leak but that's getting a little OCD

Smokey Eddy · « **Reply #14 on:** August 24, 2008, 07:39:19 pm »

and RIGHTFULLY so!