KgS4

I know the normal operation of an N75 - the ECU uses a duty cycle to open/close it enough to maintain a desired level of control pressure in the wastegate line. And, somehow, the ECS valve *must* maintain less pressure in that line for a period of time (wastegate is slightly more closed) than stock, in order to make more boost. It's been said that the ECS valve just reacts slower, but in what way - it opens and closes slower? I don't necessarily see how that would change the control pressure - the ECU is sending several pulses a sec to the N75, wouldn't the avg opening be the same? And even if it did react "slower", doesn't that mean when you first get on the boost (and the ECU tells the N75 to open), it wouldn't open as 'fast' and you wouldn't spool as fast??? Thanks for any explanation, I just can't make sense of ECS's information!

TTschwing

The N75 Duty cycle (solenoid pulsing) does not change since this is controlled by the ECU. Vag runs have confirmed this. The amount of boost released to the wastegate to open it does, due to some restriction in the ECS N75 . See this picture (and the Restrictor label):

<img src="http://images.fotki.com/v12/photos/7/7305/149094/n75a-vi.jpg">

With less boost being released to the wastegate, the gate is opening slower and not as much, thus altering the boost curve ie: allowing boost to build earlier and not blow off as much at high RPM loads. Here's a schematic, it's pretty intuitive (just mentally reverse the N75 ports from the picture above):

<img src="http://images.fotki.com/v9/photos/7/7305/149094/turbo_schematic-vi.jpg">

Basically the ESC N75 just alters the boost curve through restricting the boost to the wastegate, similar to the operation of manual boost controllers, but it does retain some of the ECU based curve....

Here's a boost curve with stock and ECS valves in operation on my car shortly after the ECS valve install:

<img src="http://images.fotki.com/v8/photos/7/7305/149094/ECSN75-vi.jpg">

Steve

JohnLZ7W

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KgS4

1) I heard the valve doesn't work (increase boost) with APR Stg3 - now, I once saw an N75 duty cycle log of stg3 where it holds 100%, where as most programs hover around 80-90%. So would the explanation be that at 100% duty cycle, since the valve is just completely open, the wastegate sees little pressure anyway (whether it be stock or ECS N75 place), and hence no difference?

2) If the ECS N75 simply releases less boost pressure to the wastegate at X duty cycle (compared to the stock valve), why wouldn't it also make more boost in the upper RPMs? (I do see your graph does make a bit more, but ECS and others say gains are down lower). The ECU's N75 duty cycles in the upper RPMs are often similar to those in low rpms from what I've seen on N75 graphs, so I'm surprised the same gains would not be had there also?

Thanks in advance

TTschwing

As the N75 I'm running came from Marcus who has a stage 3 set-up. We've vagged both cars and you are correct. It did not work on his car, infact we got lower boost numbers. APR does not recommend the valve because they've taken care of it in the programming of the N75 duty cycle. They've essentially done electronically what the N75 does mechanically on (lessor) cars. I've vagged the duty cycle on Marcus's Stg 3 and it indeed does start out at 100% and gradually taper. The HIGHER the duty cycle in % the LESS boost is being released to the wastegate. 100%=None, so the wastegate is not opening at all.
You approach the ability of the turbo to spool pressure at higher RPM's ie efficiency drops and anything less than 100% is cracking open the Gate and bleeding some boost.

KgS4

on their programmed in N75 duty cycles? I'm thinking of trying this on a chipped S4 by the way (which apparently there is little data on for this application, but ECS claims it should work).
I wanted to check with you guys as you seem to have the most experience with it. Right now (chipped S4) I currently see about 80%-85% duty cycle pretty much through the rpm range, in any case.

TTschwing

The only issues have been with MTM and GIAC X chips which tend to tune for more boost out of the box. There have been no issues with APR chips to my knowledge. The VW Vortex boys also have problems when running the X chip and this valve. Typically throws the car into limp mode fairly regularly, but the ECU limits are lower in the VW camp. Try it...there's a ready market for resale if it doesn't work for you!

KgS4

Thanks for all your input.

economisTT

i was considering getting the ecs n75 valve, but since i also want to get the apr stage 3 kit (hopefully this spring), i won't!

TTschwing

I might have a little interim fix for you for less than $25. Soons I get the car running again and test it, I'll spill the beans....