Longer Final Drive + JDM Torsen

[eracer]

Hello,

I'm a CTR newbie from Belgium, I have just bought a 2003 Type R EP3. I drove it 300km to make the paperwork for it, and I am thrilled to own it. Such a pleasure to drive, so light, so responsive, so accurately pointing where you want

I was (and still am) driving a Prelude 2.2VTEC since 1997, it has done 400.000km and still VTECs many times a week Just before buying the Prelude in 1997, I had the luck of driving the Intrega DC1 with the Torsen differential, and the only regret I had with the Prelude was that it so much deserved one. It missed me for 400.000km.

So, I am right now making the change right away to a JDM Torsen diff in the Civic.

Also, according to my test drive, it can cope with a longer Final Drive because the small gears are very short, and the 6th would be better a bit longer for the motorway.
I am expecting little change at the traffic light, less noise and less fuel on the motorway. The price to pay is a calculated (I'm engineer) 10km/h loss in top speed in 6th, the top speed would be reached on the rev limiter of the 5th actually. But actually I don't care, I am driving this fast.

So, I am changing the Final Drive from 4.764 (stock) to 4.389.

I am quite confident in the change, but it's not common. Has anyone tried it, and what is the feedback ?

===========================
Colin Chapman said : LIGHT IS RIGHT

Driving the CTR absolutely confirms his true quote.

 

[eracer]

I am posting my first feedback.

First about the Final Drive change. The change from 4.764 (stock) to 4.389 makes all the gears 8.2% longer. It give a little less the feeling that you are doing a rallye stage with short gears, but frankly, the 1st and 2nd gears are still short enough. The longer drive make the car less noisy and very likely more sober on the motorway. The engine is revving at 4600 rpm instead of 5000 rpm at 160km/h, which is my usual cruising speed on long distances. I am really looking forward to make a full tank drive. Before the change, and between 140 and 160km/h I did 8.96l/100km.

Now, about the Torsen. Well, it gives a lot of torque steer ! The inside wheel does not spin anymore, this is for sure, but their is a hell of steer torque in 1st and 2nd. I need to get used to it, but now I never put my foot on the floor with if I don't have my 2 hands on the steering and if I have to leave the steering wheel with 1 hand for changing gear or to change my hands position at the exit of a tight corner. I have the car for 3 days, on the dry, not have had the opportunity to take 3rd gears corners. Anyway, on the dry the 200BHP are going straight to the road, no doubt.

It makes the cars more agressive and I suppose significantly quicker, but I need to get used to it, and I give to the car to someone I will brief to take it very easy.

Also, the self alignment torque of the steering is reduced, you kind of feel like the steering is sticky and does not come back to straight position by itself. So, definitely not a change to recommend to anyone, but for advanced drivers.

I will post my comments after more driving experience with the car in the coming weeks.

Anyway, the car feels light, feels moving easily, even under 3000rpm it goes so much quicker than the daily traffic. The CTR is a very effective car, with lots of room inside. Child number 2 coming in less than a month. Not space problem.

 

[Shaenei]

Top review :smt023

 

[Griffin]

 

[eracer]

Caster

I had a talk with ELR (European Luigi Racing) in Belgium, who used to race with those cars. Marc said to me that the caster angle on this car was very little. This is causing weak steer alignment, and does not hide the torque steer.

I have had a look at some cars spec sheets (from http://www.hondahookup.com/manuals/) :

* Prelude 92-96 (my previous car, my reference, very good car overall) : Caster 2.67 +- 1 deg
* Integra 93 (I don't remember torque steer) : Caster 1.30 +- 1 deg
* Civic EP3 : Caster 1.33

Well... I don't get it between the Integra and the Civic EP3. I will be checking tomorrow if I can have the caster measured on my EP3.

This forum is going in the same direction : http://honda-tech.com/showthread.php?t=2639666

Anyway, it looks like 1 more degree woudn't hurt the EP3 compared to the Prelude.

I found some parts to increase caster :

by moving the lower front wishbone forward
* SUPERPRO http://203.31.191.243/fulcrumCat/ P/N SPF2308K
* J`s Racing http://www.risingsunperformance.nl/j-s-racing-high-caster-lower-arm-left-civic-ep3.html

by moving rearward the top mcpherson pivot attachement point
* K-MAC http://www.k-mac.com/pages/newprods/honda/honda.htm
* D2 http://www.japshop.co.uk/acatalog/civic_ep3-Suspension.html

I see no indication of how much the caster will change.

Has anyone tried this out, and has any comment to share ?

 

[eracer]

Torsen LSD on the wet

First days of wet roads with the CTR this week end, and with the Torsen diff. I had the opportunity to drive around places I know really well with the Prelude, and the CTR handles beautifully ! No more inside wheel spin, the understeer is gone. Amazing.

A guy was following me in an Audi A4 2.0TDI, I turned in a wet and usually slippy corner carefully, then applied throttle massively in medium rpm from the apex, then had the wheels straight with full throttle, looked in the rear view mirror 2 seconds later, that poor guy was looking like standing still in the corner. He was left 50 meters behind in a single corner, without exceeding 6000rpm. Amazing. The LSD is a clear "unfair advantage" in the wet ! Wonderful device ! :lol:

The day after, I'm still laughing.

 

[eracer]

SuperPro Front Castor Kit

I have the SuperPro front bushing kit fitted, to increase caster.

It changes my life. I have the LSD, and the car was exhausting to drive because the steering was not aligning itself. I was holding the steering wheel so hard to maintain the wheels pointing straight on the motorway and in the corners to avoid the barriers that I was exhausted driving the car.

Now, with the bushing kit the steering wheel is returning well to neutral, I can take my hands off from it on the motorway without being afraid of going into the wall at the next bump in the road, I am sooooooooooooo happy with it. I feel relieved, and I enjoy the car and the LSD.

The LSD was amplifying the lack or steering self aligning torque, and I strongly discourage installing the LSD without fitting the bushing kit.

The kit moves the front lower wishbones forward by about 5.5mm, which increases castor by around 0.6°. The car could certainly aford the same increase again. The (little) price to pay is a heavier steering when parking the car. But this is nothing compared to the benefits!

Attached : instructions for the SuperPro kit and the alignment values of my car with the kit fitted.

Now in total my car is std with the following changes :

• JDM Torsen LSD
• Longer final drive : 4.389
• SuperPro front bushing kit (castor increase).

The car feels great, I hope to have some free roads to try it out ! I strongly recommend the combination LSD + Castor increase.

 

[Kozy]

Are you sure you are not confusing the torque vectoring effects of the Torsen with a weak self centering? Because you are applying different amounts of torque to the inside and outside wheels coming out of a turn the effect is similar to tank tracks where the car actually wants to turn more than you are steering. With a Quaife in my EK4 I found I could drive round hairpins on autotest courses without even holding on to the steering wheel (not recommended!) due to this effect.

 

[Stoo.]

The reason for the poor self-centring characteristic is due to the very small amount of positive castor present before adjustment.
Even now, after adjustment, there is still very little positive castor.
Plus, the imbalance of camber on the front whee;s won't have been helping either.

I'll bet that the car had a tendancy to pull right.

 

[eracer]

Are you sure you are not confusing the torque vectoring effects of the Torsen with a weak self centering? Because you are applying different amounts of torque to the inside and outside wheels coming out of a turn the effect is similar to tank tracks where the car actually wants to turn more than you are steering. With a Quaife in my EK4 I found I could drive round hairpins on autotest courses without even holding on to the steering wheel (not recommended!) due to this effect.

It confirms my findings. With LSD and with std castor the steering wheel self alignment torque is overridden by the torque difference between the FR and FL wheels (LSD), which tends to turn the steering wheel into the corner. The total of the two cancel eachother, and indeed in some situations the steering "locks" itself into the turned position upon applying throttle. I hate this feeling because you have to turn back yourself the steering into neutral to exit the corner. This is exhausting and stressful.

Now with the increased castor, the steering wheel self alignment torque is much higher than the LSD torque back, and I actually feel the LSD only in the polar moment of the car. Not anymore in the steering wheel. And of course by observing no understeer !!! When I put enough throttle to saturate the outer front tyre, there is no hint of a wheelspin but the feel like the front tyres are slipping sideways gently. It feels like a racecar. The LSD is very, very effective from the apex up to the corner exit.

 

[eracer]

The reason for the poor self-centring characteristic is due to the very small amount of positive castor present before adjustment.
Even now, after adjustment, there is still very little positive castor.
Plus, the imbalance of camber on the front whee;s won't have been helping either.

I'll bet that the car had a tendancy to pull right.

As I said, the car would easily afford 2.5° castor, while driving. However, parking the car would be more difficult, and the power steering would need an upgrade.
My car goes straight, no problem at all. The castor difference FR/FL does not show on the road.

Now I need definitely more space and less crowded road to see what the limit of the rear end is ;-)

 

[Kozy]

It confirms my findings. With LSD and with std castor the steering wheel self alignment torque is overridden by the torque difference between the FR and FL wheels (LSD), which tends to turn the steering wheel into the corner. The total of the two cancel eachother, and indeed in some situations the steering "locks" itself into the turned position upon applying throttle. I hate this feeling because you have to turn back yourself the steering into neutral to exit the corner. This is exhausting and stressful.

Now with the increased castor, the steering wheel self alignment torque is much higher than the LSD torque back, and I actually feel the LSD only in the polar moment of the car. Not anymore in the steering wheel. And of course by observing no understeer !!! When I put enough throttle to saturate the outer front tyre, there is no hint of a wheelspin but the feel like the front tyres are slipping sideways gently. It feels like a racecar. The LSD is very, very effective from the apex up to the corner exit.

This is all very interesting, I never knew you could match the LSD steering force with castor angle. Know you've mentioned it though it makes perfect sense. Would explains why the Quaife in my EK felt so 'alive' (i.e. you had to wrestle the wheel) and yet you can't notice the effects of the OEM Torsen in my ATR.