Swapping "vac box"/moo valve with single use N75 valve

Hello,

I have the multi vac box on my Polo



All it does now is control the turbo, it never did anti shudder (electric on the BLT) and I don't have EGR anymore

I want to delete it so I can access my top mounts to adjust damping/rebound/camber easily

I don't want to relocate it, reasons:
- Expensive to replace
- Big and ugly
- Heavy (every gram counts)
- Its my engine bay and my car and I want what I want

I want to swap it with the "golf" N75 valve:



Wiring and vac line I've got sorted.

My question is, do they behave differently? In real explicit terms:

Does a specified amount of voltage to both valves result in the same vacuum on both valves.

Or are they scaled differently - if so, is there a linearisation map for it

Think along the lines of swapping a 3 bar MAP sensor for a 4 bar MAP sensor

Not familiar with the multi-vac device currently in your Polo, but I can tell you that the N75 is a bang-bang valve... meaning it is either on or off. 12V or 0V.

The ECU controls it using pulse-width modulation, but I don't believe it's a calibrated system per-se, rather just simple closed-loop control where it simply adjusts the PCM signal until the MAP reports the targeted boost.

they both work the same, we do it all the time, they work on 5v too!

Thanks for the useful information! I helped your advice!

Perfect!

Ryan gave me the answer I was looking for and very interesting to know how it works re: pulse width modulation. Thank you both

Any need for the vac ball Ryan following these changes?

i am interested in doing this conversion also.
can one of you help with the wiring info? what wires on the plug to use for the N75 valve...

thanks

Sheppy said:

Hello,
- Heavy (every gram counts)
- Its my engine bay and my car and I want what I want

Click to expand...

So I take it you starve yourself and make sure you take a big hard poo before you hit the race track?
100 lbs. = 0.10 second in a 1/4 mile ripem, I get it.

My 2 cents! You’re obviously getting a tune right? Just delete it and put the boost right into the waste gate actuator and adjust the rod to gain more boost like you do on the Cummins. If you’re that uptight about 12 ounces of parts, then you’re going for all out 110% ripems right? With this argument, you don’t need it at all. You don’t need half the crap in your engine bay.

Mongler98 said:

So I take it you starve yourself and make sure you take a big hard poo before you hit the race track?
100 lbs. = 0.10 second in a 1/4 mile ripem, I get it.
My 2 cents! You’re obviously getting a tune right? Just delete it and put the boost right into the waste gate actuator and adjust the rod to gain more boost like you do on the Cummins. If you’re that uptight about 12 ounces of parts, then you’re going for all out 110% ripems right? With this argument, you don’t need it at all. You don’t need half the crap in your engine bay.

Click to expand...

very interested how you can control a vacuum actuator with boost

it's sprung the wrong direction for one, and for two, the diaphragm's on the wrong side of the internal can shaped washer dealie (that dingus that keeps the diaphragm from tearing)

Change the actuator to boost controlled, solved for my point. You could just weld the waste gate shut and run a boost blow off and fix with tune. Aside from that, no I guess not. I thought the n75 is a boost regulator not a vacuum regulator?
You mentioned the n75 so that’s why I thought your turbo was boost controlled actuator.

Can anyone help with the wiring info of the "vac box"? what wires on the plug to use for the N75 valve...
To convert the vacuum box to the standard N75.

Mongler98 said:

Change the actuator to boost controlled, solved for my point. You could just weld the waste gate shut and run a boost blow off and fix with tune. Aside from that, no I guess not. I thought the n75 is a boost regulator not a vacuum regulator?
You mentioned the n75 so that’s why I thought your turbo was boost controlled actuator.

Click to expand...

N75 is controlling boost to wastegate actuator on A3/B4 but N75 controls vacuum to the vane actuator on VNT cars.

It is weird that VW uses the same nomenclature for these but I think that's where the misunderstanding here is...

R-TDIGR said:

Can anyone help with the wiring info of the "vac box"? what wires on the plug to use for the N75 valve...
To convert the vacuum box to the standard N75.

Click to expand...

Wire 3 and 5 from the plug on your original vac box loom go to the N75.

ketchupshirt88 said:

N75 is controlling boost to wastegate actuator on A3/B4 but N75 controls vacuum to the vane actuator on VNT cars.

It is weird that VW uses the same nomenclature for these but I think that's where the misunderstanding here is...

Click to expand...

is it the same part #? If it is, it makes sense, its just a metered controlled valve

they are not the same part number.

The MK4's N75 looks (and works) just like the N18 EGR solenoid on your MK3 except white where the hoses go instead of black.

Boost86 said:

Wire 3 and 5 from the plug on your original vac box loom go to the N75.

Click to expand...

thanks very much

On the polo 9n/seat Ibiza we use the polo 6R n75
Works a treat