Some feedback on 4.08 FD+ SRM+Quaiffe LSD on road course.
 

So over the last 2 weeks I have had the following installed:

1. 4.08 Final Drive.
2. Quaiffe LSD.
3. SPL solid Diff bushing kit.
4. Nismo finned Diff cover.

Thanks Z1 for the great Xmas sale on the Quaiffe, thanks C3 for the deal on SPL, 4.08 and of course the fantastic install.

Literally got the car back last Friday at noon; I headed out to chuckwalla valley raceway 2 hours later for my Bday weekend(29) :tiphat:

Here's my thoughts and feedback:

Pros

1. This car should have come with the 4.08 FD in the 6mt to begin with. The 4.08 FD is basically everything you wanted this car to be in terms of acceleration, drive-ability, etc. Everything this car does, the 4.08 will make it do better.

2. The Quaiffe diff is amazing-I know the torsion type vs clutch type debate could go on and on, but this diff with the solid bushings, brings this car to a whole new level. Press pedal to floor, and power goes to ground-end of story.


3. The SPL solid diff bushings are a no brainer, if you are going to do a new diff, put the SPL's in and be done with it. If you are concerned with the noise, then I am not talking to you, don't read the rest of this thread.


Cons:

1. Don't under estimate the complexity and difficulty of the install of these parts. Thanks Z1 and C3 for dealing with it, but anyone that has done this install, I am sure can attest to the endless list of widgets, washers, shims, etc that are needed. When all is said and done, you are going to put yourself back about 5K+ if you aren't doing your own install. If you are not a professional mechanic, this is not something you can just learn on your own and requires a substantial amount of labor in addition to some very expensive parts. If you are serious about racing or doing time trials with this car though it is something you have to do.

2. SRM no longer works on track, oddly enough it works fine on DD. But as soon as you hit a high rev downshift, the ECU freaks out and shuts down SRM, you getting a warning message on your LCD and SRM will not turn back on until the car has been turned off. Be ready to heel-toe the crappiest, narrowest gas pedal on earth -anyone have pedal solutions?

3. Not much else-if you are serious about putting the power down, a mechanical diff and solid bushings is a must on this car. If you have any holdups about buying or installing the 4.08 don't. If you are dependent on SRM for your rev match, get ready to learn something new!

In Summary:

4.08+ mechanical diff is a huge huge performance upgrade for this car in terms of rear traction and making this car do what it needs to.

I would still like to hear any feedback on why anyone thinks that a clutch type diff is better than the torsion type for this car. Having only tried the quaiffe now for 2 days, I am in awe basically at what it does.

Finally, if anyone knows a fix for SRM and the 4.08 please chime in. It is better and safer to turn off SRM on track than it is to attempt to use it with the 4.08. SRM will work at low RPM shifts, but will ultimately fail on track when you least expect it. It is a safety concern imo because it will work for a lap or so and then just shut off and then you will clutch kick at some random point in time. If anyone has solved the SRM/4.08 problem via ecu/tune/flash/cut the purple wire etc, would be interested to hear.

Just curious, what is your mileage around town with the taller gear, any chance you can tell us how tall 2nd gear is with this rear? and if so what size rear tire?

I have the quaiffe/ SPL combo as well and love it. the difference it made in autoX was very noticeable and it dropped my times. The bushing I have grown to love the sound and the tightness of the rear end. I have noticed on hard braking the TC freaks out but whit it off and on the track it is great. I had the diff put in for around $850 at my trusted Nissan dealer and the diff bushing I did my self........ NEVER AGAIN! because it sucked getting it out and putting it in.

You really need to disconnect the yaw sensor (both slip and VDC lights on) to feel what the differential is doing, especially in braking.

Still sort of looking for a good how to. There seems to be piece meal information and pictures on this procedure, but I haven't seen a simple. 1. Do this. 2.Then do this...etc

I definitely drive with traction control off on track, and am interested in the effects of disabling the yaw sensor, but most of the articles seem to either conflict or are incomplete on how to accomplish it.

How I did it was pull out cup holder (pull back and up). There is a piece of plastic covering the yaw sensor so I got some tin snips and just cut the plastic. Then get a screw driver and press the tab on the yaw sensor plug (tab is on drivers side) and pull on plug until it pops out. You could remove the whole center console so you don't have to cut anything or if you have ninja hand skills you might be able to get around the plastic and get the plug out but I knew I would be getting in there a lot so I didn't mind cutting the plastic to make it easier in the future.

2nd will take you to sixty-maybe 60.5 mph on my 18" 285/35 RS3's according to my lab results as of this morning ;).

Also while performing this experiment, I ran into a familiar issue-when I hit the rev limiter, SRM went wacko, it shut off SRM and the little gear indicator. The car up shifted very rough after this happened, it was just like when you do a battery disconnect and have to wait for the ECU to adjust again.

This was not what happened to me when I was on track. When I was on track and I downshifted, SRM turned off, but I did not lose my gear light and experienced no "reset" condition like I did when I revved to redline.

So it seems two different things can trigger SRM being disabled with two different results:

1. If you do a downshift at high RPM like a 4 to 3 going into a braking zone, you will lose SRM, but you will not lose your gear indicator on the dash.

2. If you redline RPM(in 2nd gear anyway) you will lose SRM, lose your gear counter, and then you will experience a driving condition that is similar to battery disconnect.

Maybe I should post some of this info over in the engine/tuning section and see if anyone has any feedback.

And then what? I don't understand what needs to happen exactly after that. I know there is a green wire, etc. Some people put a switch in, yadda yadda. Do you just cut the green wire and then solder in a switch?

http://www.the370z.com/diy-section-d...er-switch.html

looks like just cut the green wire.. then solder it to the post of a switch and thats it.. maybe buy extra wire to extend it to reach the switch if u have to?

I have a Quaife and upgraded to a KAAZ clutch-pack and 4:08:1 gears because I use the kerbs quite aggressively and the Quaife won't drive when one wheel is in the air

The Quaife is now being fitted with 3.9:1 gears as a "spare" (I can use it on higher speed circuits to avoid running out of rev's).

The thread reference tells you how to insert a switch to control the yaw sensor, BUT you have the cycle the ignition to reset it. With the yaw sensor disabled, you can trail-brake to your heart's content

here's 2 threads i just skimmed through.. seems like it have some good info.. hope this helps

http://www.the370z.com/track-autocro...or-review.html

http://www.the370z.com/diy-section-d...er-switch.html

I had considered the 3.9's, but for the courses near me, 4.08 makes more sense. We don't have many tracks where you get much into 5th gear on the 3.7. And even our "fast tracks" top out at around 130-150.

I like the strategy of having a backup unit pre built though, nice idea.

Does ecutek fix this issue at all?

ECUTek can retune the SRM for a 4.08 FD ratio.