Observations: NA pump vs TD pump with a vnt15.

[hamradio]

So, I recently swapped from an old worn out NA pump to a "condition unknown" 1.6td pump from an '84 jetta.  It doesn't leak...I'm happy...$60 well spent.  I previously had an NA pump with the fuel screw turned in enough to not be able to get the idle any lower.


Anyway, some observations-

Upon free revving, it revs down much slower than it did with the na pump.  It seems like the boost falls at the same time the engine revs down...maybe boost is still built and it's fueling it a little extra?


If one holds their foot on the throttle and gives it enough throttle input to slowly build 3 or 4 psi, once the boost is built, it will start revving more.  Is this due to the enrichment?


Also, it now builds boost ridiculously quickly...I can feel the vanes open in 1st like it is nothing...I feel it long long before I hit the governor on the pump.

[jtanguay]

i think theoretically you can get more fuel out of a TD pump with the enrichment device.  you can screw in the fuel screw to where the car just wants to run away, and then the enrichment device on the pump should add even more fuel under boost.

so hamradio, what would your advice be to anyone who would want to get a VNT turbo, but is worried that it'll break?  how long have you been running yours?  i'm guessing you're not gentle with it  :lol:

[Rabbit on Roids]

ive had my vnt on my car for almost a year now. and that thing sees full boost pretty much whenever i drive the car. it seems to be a very reliable turbo.

[jtanguay]

ive had my vnt on my car for almost a year now. and that thing sees full boost pretty much whenever i drive the car. it seems to be a very reliable turbo.

good to hear!  

[hamradio]

Hmmm...it's not due to enrichment.  I unhooked the tube, and the revs would hang in the same way.  I'm thinking the fuel screw is turned in too far...it was up against the collar when I bought it.  I also have crappy old worn out injectors.



Come to think of it, I don't think I've ever driven my car without hitting full boost...it's natural, it seems.  Usually by the time I'm through first and 2nd gear, not even revving hard, it has hit full boost.  I also can hit full boost in 5th on the freeway just by flooring it.

[subsonic]

What kind of boost levels are you talking about.  Any problems so far with high boost at lower rpm?

[Hey]

i think theoretically you can get more fuel out of a TD pump with the enrichment device.

In fact, IF the pump is very well adjusted (which is VERY VERY rare), you will have the same quantity because it is not en enrichment device but a "cutting" device. If the pump is not well adjusted (often) you will have less.

It doesn't give you fuel, it just makes the pump wait for some boost before giving you more... it serves to prevent fumes.

LDA might be: Limiting Device Actuator

[Golf/Jetta]

i don't know if this will work, an Air tank
i was going to say an Air Regulator, i wonder if that stalls.
ideas

[Rabbit on Roids]

i don't know if this will work, an Air tank
i was going to say an Air Regulator, i wonder if that stalls.
ideas

?!?! what? randomness about air tanks and regulators? making a pneumatic turbo spooling device?

[jtanguay]

i think theoretically you can get more fuel out of a TD pump with the enrichment device.

In fact, IF the pump is very well adjusted (which is VERY VERY rare), you will have the same quantity because it is not en enrichment device but a "cutting" device. If the pump is not well adjusted (often) you will have less.

It doesn't give you fuel, it just makes the pump wait for some boost before giving you more... it serves to prevent fumes.

LDA might be: Limiting Device Actuator

but the LDA itself does the same as screwing in the fuel screw under boost. so in actuality it does increase fueling, and more so than you could without it (and have a good stable idle)

[Hey]

You are correct... but let me clarify my point of view.

If you just remove the boost-pin... you will have more fuel.

If you put a boost-pin you have less fuel when there is no boost.

Then it's a Limiting device since you have less with it.


A NA pump is a pump without this limiting device. So this is why the guy may see faster boost building up without it.

The LDA only shorten the throttle lever movement. So even if you put the pedal to the floor, in fact you are ¾ full throttle until there is some boost.

[hamradio]

OK, here's an issue that's driving me bonkers.


The car started and ran great with my old worn out 1.6na pump.  The engine started immediately when about 30* outside...with the new 1.6td pump, cold starts are much harder and smokier.  I do have old worn out injectors, but it's as if the car is running on 2 cylinders at idle until I actually drive it a little distance, and blue smoke pours from it.  Timing is reasonable...sounds right, but I need to get to a dial indicator to check it.  Fuel screw is cranked to the collar and idle corrected (changing fuel screw had no effect on this missing issue).


After the car has been driven a little, even 1/4 mile, it runs fine.


Any thoughts?

[Rabbit on Roids]

OK, here's an issue that's driving me bonkers.


The car started and ran great with my old worn out 1.6na pump.  The engine started immediately when about 30* outside...with the new 1.6td pump, cold starts are much harder and smokier.  I do have old worn out injectors, but it's as if the car is running on 2 cylinders at idle until I actually drive it a little distance, and blue smoke pours from it.  Timing is reasonable...sounds right, but I need to get to a dial indicator to check it.  Fuel screw is cranked to the collar and idle corrected (changing fuel screw had no effect on this missing issue).


After the car has been driven a little, even 1/4 mile, it runs fine.


Any thoughts?

yea, this is the same thing my car is doing. POURS blue smoke when your cold.

[Hey]

I think a timing issue would be the most probable cause.