The above quote was taken from the FAQ section of Fuddle Racing website. Can someone describe for me what PWM sounds/feels like when it happens?

 

It kinda feels like a vibration/shudder. It sounds like the exhaust is vibrating hard against the floorboard. I have a fuddle 3400 and have yet to feel it when it locks up. Tune your shift firmness or get a shift kit and you should be golden.

 

What is the advantage of this? I'm not sure i've even noticed what you guys are describing...

 

From what I've read, there are two separate "gates"
in the TCC chain. An apply solemoid valve, and a
sub-regulator which is PWM'd (more duty cycle =
more pressure, opposite of the force motor). The
TCC line depends from the force motor main so you
have an issue at light loads, the force motor starves
the TCC even at full TCC%. And sometimes it goes
downhill from there.

I have the "Street Performance" converter and have
detected no such thing (audible tones or squeal).

If you tune the car and just set the minimum TCC PW
to 99% you will not have the "soft apply" going on.

PWM is a regulation scheme which is more "digital",
you modulate the delivery of voltage/current in time
and either on or off, which has the result of spending
all (almost) of your time in one of two highly efficient
states and little is lost in the power switches. Either
full voltage but no current across the switch, or no
voltage (closed switch) and full current. In either
state something times zero is zero losses. Big deal when
you are talking amps of current and 12V inside a poorly
cooled PCM case. The scheme depends on something
downstream to have an averaging effect - usually the
inductance of the load, or a filter choke. When you chop
voltage really fast the inductor will let the voltage swing
wherever, and just pass an average current (needing a
few other things like a freewheel diode etc.).

But it beats the hell out of dropping a large amount of
the load power inside a linear regulator; that's cook, cook,
cook.

PWM is the squeal you hear in your cordless drill at half
trigger.

At WOT you should be seeing full TCC duty and probably
hear nothing. Anything you do hear is clutch face squeal,
there. Where you would hear PWM tones is more likely at
part throttle TCC apply.

Typical PWM frequencies are 10kHz - few hundred kHz as
these fall in the realm of reasonable inductor sizes and
reasonable switching (frequency) losses. So unless you
have dog ears, you're unlikely to hear the chop frequency
(though there can be sub-harmonics in the iron etc.). If
the note is down in the hundreds of Hz, trumpet instead
of piccolo, this is not the PWM frequency but the clutch
making its own music due to weak apply and being allowed
to skate rather than grab.

I believe you're more likely to hear the clutch itself squeal
due to grab-and-skip, fluttering when the pressure is not
quite enough to hold, but enough to keep the faces in
contact. Every clutch material system is different in this
respect, stockers are chosen for longevity (in "normal"
envelope use) and noise while busting on it all season at
full power wants a different compromise, a hard grab,
and fingernails on the chalkboard may be your downside.

 

bigman...You have described exactly what is happening. It happens very rarely, but under certain conditions, it is is obviously audible. Thanks for the reply.

jimmyblue...could you go into a little more detail please? Just kidding...
Thanks for taking the time to explain the cause and effect so well. Wow, I feel like I spent the night at Holiday Inn Express now. I will probably look into a shift kit to get rid of the situation. Thanks again.

 

Based on my experience in a 2004 GTO with Fuddle 2800 it can take several forms. It can be a brief low frequency shudder ( think slide trombone playing low C) for a couple seconds when accelerating in 4th gear between 40-50 mph. Since the RPM's are under 2000, they don't change very much. This is noticeable but not too annoying.

Or it can happen during re-lock going 50-60 mph after touching the brakes. Under these conditions it is a lot louder, more raspy and can continue for up to ten seconds, especially going uphill. This can occur in 3rd or 4th gear at 2000 RPM+.

I'm hesitant to do the shift kit fix because, heaven forbid, suppose there is something wrong with the tranny or the TC. Then the warranty is blown and I'm SOL.

Here are some links about the situation:

http://www.4l60-e.com/#Performance%20Parts


http://www.sonnax.com/bulletins/tech/TS-BW-699.pdf


http://www.gmhightechperformance.com...07htp_projls1/


http://www.transmissionspecialty.com.../DM/4L60-E.htm

 

Thanks for your input, surfgzr. I hear what you are saying about the warranty; but I figure the installation of the TC has already put me out of that ball game. Actually, if I am reading the Fuddle FAQ correctly, the clutch in the stock TC is doing the same thing...you just don't hear it because of the different clutch material. Mine only rarely is audible, so I might just live with it for awhile.

 

My car would do the PWM after I put in the Fuddle stall at under 2k rpms and mostly up hills, I had screws put in my foot, so car sat for around 4 months with only maybe 6 times driving it. Friday I noticed I am starting to get the PWM at 1/4 throttle or less, even sometimes over 2k rpms, so now is getting more irritating. I could car less about a shift kit, but looks like is what will be needed and I seen they make the kits to fix particular problems, so now will have to talk with transgo and hopefully they have a kit to solve this problem. I'm not sure how a shift kit could fix this problem since it is part throttle and normally not occuring at shifts(it can when it shifts at low rpms but that isn't the main issue), if any basic shift kit does work then it is from increased pressure, but I would rather fix just the problem. The PWM didn't bother me at 2k and under before, but now at 40 mph, 60mph, tap the gas a little and sounds like crap..I can't drive WOT all the time, as much as I would like to