Which N75 should I use? F, H, or J? 2000 1.8TQM w/ GIAC
12-04-2008, 04:56 AM
#1
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Which N75 should I use? F, H, or J? 2000 1.8TQM w/ GIAC
My only mods are a GIAC chip and a 710N diverter valve. I have been having an occasional surging issue at partial throttle and have been logging an intermittent charge pressure control negative deviation. I have no leaks. I probably have the older C version valve which was known to go bad. Which version wastegate valve should I get as a replacement?
12-04-2008, 05:18 AM
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H is most reliable from what I hear...
There was a poll over at passatworld.com... H was best in regards
to providing power like the J but more reliable.
Be forewarned, you may be swapping them out to see what works
best for you. Many folks resorted back to stock because of
issues from non-stock valve.
to providing power like the J but more reliable.
Be forewarned, you may be swapping them out to see what works
best for you. Many folks resorted back to stock because of
issues from non-stock valve.
12-04-2008, 05:37 AM
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I'm leaning towards the (stock) F
I haven't pulled my old one, but I bet when I do it will be the older 'C' version which was discontinued and replaced with the F. I want the valve that will provide the smoothest throttle response throughout the rpm range.
12-04-2008, 06:12 AM
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That's a wise choice... I would also stick to stock or as close to stock as possible.
However, if you were interested in gaining more power, you could
try the H as a safer bet than the rest.
try the H as a safer bet than the rest.
12-04-2008, 06:56 AM
#6
If the car is 2000 or newer, there's no gain to be had.
The 2000+ A4 1.8Ts have a MAP sensor, the ECU adjusts duty cycle down to compensate for the more agressive N75s. All you end up with then is a boost spike followed by a valley which might actually make the car slower, plus less smooth part throttle.
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12-04-2008, 09:38 AM
#9
It should be... (more)
If your original N75 was failing, that would explain the increase in performance switching to a new valve.
The other caveat is the tune. Most tuners use PID ( <a href="http://en.wikipedia.org/wiki/PID_controller">http://en.wikipedia.org/wiki/PID_controller</a> ) to control the boost on stage 1 and 2 chips on cars w/ OEM MAP sensors. If you're running a tune which was developed in a way where the N75 duty is hard-coded and doesn't compensate with MAP sensor input, you would see more boost.
I would suggest logging blocks 003, 114, and 115 with a properly working OEM valve and your upgraded valve. I'd be curious to see the results.
The other caveat is the tune. Most tuners use PID ( <a href="http://en.wikipedia.org/wiki/PID_controller">http://en.wikipedia.org/wiki/PID_controller</a> ) to control the boost on stage 1 and 2 chips on cars w/ OEM MAP sensors. If you're running a tune which was developed in a way where the N75 duty is hard-coded and doesn't compensate with MAP sensor input, you would see more boost.
I would suggest logging blocks 003, 114, and 115 with a properly working OEM valve and your upgraded valve. I'd be curious to see the results.
