Well I have some new news to share. Testing has been completed, and the Truechoice suspension is worth over one second per lap reduction over the Nismo S-Tune suspension.

There will be 2 versions. Both will have the shortened shock body as even a 1" lowering requires this. The Phase III will maintain the OEM front upper shock mounts for street & HPDE drivers. The Phase IV will have a spherical bearing as the upper mount for true race cars. You be the judge of what you want.

The pro drivers doing the testing liked the shocks set right in the middle of their bump & rebound adjustments. This will leave a lot of room to tune to your tastes.

This package is also very "Girl Friend" (ride comfort)friendly!

The shocks are ready now. The delay is the adjustable rear spring seats. They are about to enter production now that the design is finalized. They are hoping to ship in 2-4 weeks.

Cost has not been finalized, but should be by next week.

Now, what am I forgetting............SPRING RATES :

Front: 500 Lbs/inch Rear: 425 Lbs/inch

Shocks are designed to work well with softer or stiffer rates. Play to your hearts content!

 

After re-reading what I wrote, I need to add a couple things. The testing was done at Willow Springs with Mike Cronin Jr. doing the driving. He was VERY impressed with the improved stability under braking and how quickly it recovered from bumps.

I can't wait much longer to get this on my Z!

 

Hrm... am I really selling my car? There's something wrong with me...

 

Since I know how these were R&D'd or more specifically by whom. Can you ask someone in the know that did the R&D why they went with spring rates that transfer a awefull lot of roll stiffness to the front?

1. Are the lower rear rates the result of geometry change in the rear under load?

2. Did the R&D car or cars have oem bushings on the camber arms and radius rods?

3. What sway bar settings were used in the end?

 

I asked about the transfer of roll stiffness towards the front also. My contact just said that "all front engine cars need stiffer front spring rates". But he will check with the development team for a better answer.

I'll ask about the bushings & the sway bars.

I currently only have the Cusco sway bars, set at soft front, with non-staggered wheels & tires, and I would say my car is very neutral, and others that have driven it have said the same thing. So, I am very curious as to why they felt a need to stiffen the front as much as they have.

 

Generally speaking softer rear springs get the power down better. I don't necessarily see the stock setup as the perfect baseline. I don't think the suspension is all that well sorted out from the factory. (Perhaps I am the only Z owner suffering oversteer so I am looking forward to these).

I hope they keep the prices somewhat affordable on these. The person I spoke with gave me a rough estimate that was much higher than I anticipated.

 

Enthuz, couple of questions.

1. What is the range of heigth adjustment? Can stock height be kept?

2. Can custom spring rates be used? Say I wanted 450 lbs/in front and rear.

3. Is compression and rebound adjustment tied together or are they seperate adjustments?

Thanks for any answers you can get. Looking forward to these coming out and learning more.

 

Details:

Test of KONI Suspension on 350Z

May 10, 2005

Cars

Test car 1 is a 2005 350Z with the following modifications:
StopTech Brake Kit 355 x 32 ST-40 with ST-22 Rear
Tilton clutch and flywheel
Nismo headers and exhaust with high flow cats
Jim Wolf air intake
Nismo body kit
Nismo oil cooler
Koyo radiator
Cusco limited slip
Nismo finned diff cover
EVO 350Z sway bars
Unitech adjustable upper control arms

Test car 2 is a 2003 350Z with the following modifications:
StopTech front brake upgrade 332 x 32 ST-40
JWT clutch
Nismo flywheel
Injen intake
Injen exhaust
Nismo limited slip at soft setting
Nismo finned diff cover
Sparco racing seat
EVO 350Z sway bars
JIC rear traction and camber arms
Unitech adjustable upper control arms
Nismo Power Steering Cooler
Koyo radiator

Both cars run on the same wheel and tire package:
Nismo 18 inch wheels with Hoosier 2004 spec Grand Am Cup tires
245/40-18 front and 275/35-18 rear
Tire pressures were set at 31 front and 28 rear cold.


The suspensions tested were as follows:

Package #1 – Truechoice/Unitech KONI
Truchoice custom phase 3 double adjustable KONI shocks
Hyperco front springs at 500 lb./in. coil over
Hyperco rear springs at 425 lb./in.
Unitech rear spring adjusters
Ride height set at equal to Nismo S-Tune
Shock adjusters set at 6-6 front and rear



Package #2 – Nismo S-Tune


Package #3 – Brand X
12 kg/mm front springs 670lb/in coil over
12 kg/mm rear springs 670lb/in
rear spring height adjusters

The official driver was Mike Cronin Jr.

Results

Car #1 Package #1 Truechoice/Unitech
Best lap time 1:27.29
Slight entry understeer
Good mid-corner grip
Driver could induce exit oversteer to balance car

Car #1 Package #2 Nismo S-Tune
Best lap time 1:28.35
Less confidence under braking
Good balance, general bounciness in corners

Car #2 Package #1 Truechoice/Unitech
Best lap time 1:28.51
More front understeer than on Car #1
Tires starting to give up

Car #2 Package #3 Brand X
Lap time not recorded
Good turn in
Lots of oversteer

The EVO sway bars were all set at their middle settings.
Neither car had the EVO solid rear bushings.
Both cars had the OEM front upper shock mounts.

 

1. OEM ride height can be maintained. Not sure YET on the amount of drop allowed, but I'll guess about 2".

2. You will be able to run any spring rate you want. Softer than stock to......I'll guess 700 Lbs/inch.

3. They are seperate adjustments.


Breaking news:

Front toe is out 5 min. for a tight track we could have optimized at 15 min. out Rear toe is in 5 min.
Front camber on Car#1 is 2.5 deg. neg. Car#2 is 2.0 deg. neg.
Rear camber on both is 2.2 deg. neg.
Ride height on both cars with the Koni is set to equal the ride height of the Nismo S Tune(about an inch drop IICC).

 

So now you all know why I waited to post.........

More details:

1. The lower rear rates are not designed to allow changes in the rear geometry in fact as the car squats the rear geometry change is going towards an undesirable direction. The soft springs do take advantage of weight transfer and the ability to absorb undulations in track surface and keep the tire working.

2. The rear of the Car #1 is stock. The rear of Car #2 is modified as you know.

3. The sway bars on Car #1 were set at middle front and full soft rear.
We would probably make rear bar adjustments at the track to deal with track conditions and would also probably start most people at middle middle. Car #2 is at middle middle I believe.

 

Thanks for the quick answers. All this is great info. So the reason for the softer rear spring rates is to maintain rear tire traction? Is that correct?

 

Can you pass along any information about the shock valving? Does it have less compression like an off the shelf koni? Is it at all digressive?
Are they sharing shock dynos?

Also, I understand this is a street/track compromise setup. Will they offer or recommend using higher spring rates for those willing to sacrifice ride quality in the name of better handling? Or are these rates believed to be the best handling combo?

Enthuz thanks for fielding all the questions? What's your relationship with unitech?

 

Since a LOT of work went into developing this shock/spring package, they rightfully so are not divulging specifics. Race cars are a different animal. I don't think many of us are running race rubber. You MIGHT try the Phase IV set-up with stiffer springs. Remember that 2 pro drivers running the same lap times may have totally suspension set-ups.

As to my relationship with Unitech, I sleep with all their wife's.

 

That's what I figured. Doesn't hurt to ask.

 

Me want ... I have been waiting patiently for this setup .

 

Where do I deliver my kidney?

 

Well that's what the oem car has when you look beyond things in simple spring rate terms. How much of the spring's force actually makes it to the wheel, which is of course the wheel rate. Take a look.

oem wheel rates
160/123

Which got me thinking, didn't I see a pic of these coilovers and aren't the rear springs run on the rear shocks and not in the oem location? I could be wrong, but I swear the pic I saw of the actual setup was just that way. So, I have to ask,....are they? If they run them on the rear shock bodies, things are totally different concering roll stiffness balance.

Truechoice wheel rates if rear spirngs are on the shocks
254/251

if not
254/153

 

http://www.truechoicekoniracingservi.../new/index.asp

 

thanks for the updates, much anticipated

these products have shown up on the truechoice website (not sure when that happened since i havent checked lately)
see pdf

http://www.truechoicekoniracingservi...eb_Catalog.pdf

interesting that they list phase 1 through 4 solutions
EnthuZ? any word on the phase 2 kit?

list of phase 3 is $2300 on page 22 of the document but elsewhere lists $2600

pp

 

just beat me to it gsedan

pp