620 S Build

[CarYenta]

9 hours ago, MV8 said:

You've motivated me to get a new DVR to replace my 15 year old 118C. Still going but night vision is poor and the stick tape went away. Does the a229 have a dock? It looks like you put tape on the gps module to hold it on. I thought you might go with a 119 mini or touch screen mirror for this since I see no rear view cam. The 229 really puts the scale of the car into perspective.

 

Yep A229 has a dock. Has great 4k. I had the A229 left over from the GT3 so figured I'd try to repurpose it for this car. I've been plugging it into the cigarette lighter each time I turn on the car which also has a USB going off of it to power my phone. Not the easiest solution, but this car is never easy

 

I don't have a rear camera as I'm only concerned with people trying to insurance fraud me saying I hit them. So if they hit me from the back, I can show video that I wasn't backing up. If I was backing up, well I shouldn't have been haha

 

Recently got a usb-c card reader so I can pop the card out of the camera and read from the phone much much more rapidly than waiting for a wifi transfer and the terrible viofo app.

 

2 hours ago, CBuff said:

I went with Vantrue k1 dash cam. Keeps things hidden away and gives your front and rear camera and isn’t effected by windshield vs aero

IMG_7191.HEIC 2.1 MB · 0 downloads IMG_7205.HEIC 1.3 MB · 0 downloads IMG_7190.HEIC 2.12 MB · 0 downloads IMG_7207.HEIC 1.76 MB · 0 downloads

 

Wow! That is a clean install. Since I have mine on the roll bar I can still aero screen..

 

 

[MV8]

I like the full mirror dash cams (where it can be seen well enough in the moment without using a phone) too except for those cars in limbo years with auto dimming mirrors but no touch screens. Very few mirror DVRs have auto dimming when it should be standard since a flipper mirror would throw off the front camera angle.

 

[CarYenta]

Did some measuring for my MCS special projects guy in prep for them designing remote 3-ways:

Please tell me if something looks off!

 

 

This is for the stock sport suspension at the ride heights 150 mm front 165 mm rear.

 

Motion Ratio 

 

Front:

Measuring chassis height / shock stroke when lowering car back onto the ground after the tire was squished came back consistently at 1.66:1 (3" chassis change for 2" stroke)

Measuring the wheel movement while compressing it in the air with a jack under the tire was inconsistent as the chassis was moving up and down and pivoting on a jack stand and there's some camber change. Even trying to control for that, that was from 1.5-2.0

I think that's measuring the same thing.

 

Rear:

For the back, being a de Dion, it's 1:1 but I guess varies with severe bump angle.

 

 

 

Total Droop Wheel Travel from Ride Height

 

Front:

Full droop front change to ride height is 2.5".

 

Rear:

Full droop rear change to ride height is 1.75".

 

 

 

Total Compression Stroke Travel from Ride Height

 

Front:

Ride height to full compression is 0.5" stroke (0.5" silver visible). From full droop to full compression is 2" stroke.

 

Rear:

Ride height to full compression is 1.25" stroke (1.25" silver visible). From full droop to full compression is 2.6" stroke.

 

 

 

Weight

 

For weight, the internet gives 610 kg for S3 620S, but this is an SV so + 25 kg = 1400 lb minimum. I'm guessing that's with fluids, I don't think it's the kerb weight with a driver?

Then I have maybe 30 lb of junk in the trunk, about 40 lb extra? roll bar since mine is a track day cage, and then a fire system etc. is maybe +100 = 1500 lb without me.

 

 

With my untrusty bathroom scale that maxes out at 400 lb and is likely ultra inaccurate at the max range, and about 50 highway miles less than a full gas tank I got:

 

340 lb front corner without me in it

410 lb rear corner without me in it - went to 400 and errored out but was slowing, looked like it would go to about 410 lb based on the rate and the jack being nearly entirely unloaded.

Since I sit on the rear axle and am 150 lb, it's probably like 10-20/80-90  fr/rear adding me, so maybe

360 lb front corner with me

465 lb rear corner with me

Is 1650 lb total, full fluids and me in it which seems to check out.

43.5% fr/56.5% r

 

Super scientific. Wow.

 

 

Next is take off some shocks, do unsprung weighing with my really nice scale and ship a front and rear to Georgia.

[KnifeySpoony]

4 hours ago, CarYenta said:

 

I have maybe 30 lb of junk in the trunk

pics plz

[Croc]

Given I now ...cough cough...own....cough... a 620S.....(sheepish look) I am very interested in this thread.

 

So...why are you changing shocks?  Assume you must be changing springs as well at the same time?  What poundage are you going to?

 

 

[JohnCh]

35 minutes ago, Croc said:

Given I now ...cough cough...own....cough... a 620S.....(sheepish look) I am very interested in this thread.

 

Given it's purple, you need to add at least one or two more coughs to that statement.

[CarYenta]

20 hours ago, KnifeySpoony said:

pics plz

It's pretty dark in there even after unbuttoning.

 

 

18 hours ago, Croc said:

Given I now ...cough cough...own....cough... a 620S.....(sheepish look) I am very interested in this thread.

 

So...why are you changing shocks?  Assume you must be changing springs as well at the same time?  What poundage are you going to?

 

 

The S shocks are really under damped. Around town and back roads they are fine, but over 60-70 mph the car has no body control whatsoever and is all over the place. Very jittery, bouncy, no good. Exactly like my ND3 Miata was with the club shocks before getting Xidas. Except I got 1-way Xidas which was a mistake as I want less high speed compression generally or more rebound.

 

The standard spring rates for S shocks are 170 lb/in linear front and 140-250 lb/in progressive. 

Currently, the front seems to have a lot more droop than compression travel, so I think a tad more compression travel would be nice to have. I see 250 lb/in an being popular. For rear, probably 150 to 200 lb/in depending. However, I need to know how much spring rate comes from the shock gas pressure, so MCS will shock dyno these when I send them over. What that means is that the springs rates we choose for the MCS will not directly translate to the bilstein shocks (probably).

 

 

Question:

What is the lb/in that the bilstein compressed gas gives? Could it be upwards of 200 lb/in?

 

Front of car height change full droop to ride height
2.5"
Shock stroke associated full droop to ride height
1.5"

 

Motion ratio = 2.5/1.5 = 1.66

 

350 lb f at front wheel
X lb f at spring at 1.5" stroke

 

F wheel * d wheel = F spring * d spring

F spring = 350 lb * 2.5 inch / 1.5 inch = 583 lb on the spring at ride height 

Travel of 1.5 inches = 388 lb/in

 

But the quoted spring rate is 170 lb/in, leaving 218 lb/in on the table.

Did I measure something wrong?? That seems like a lot.

 

 

For the rear, 1.75" full droop to ride height and about 410 lb without me in it means the effective ride height spring rate is 234 lb/in which is much higher than the spring range also.

 

Edited February 7 by CarYenta

[KnifeySpoony]

Don't forget to add in the spring rate from the bushes. Not sure how much that adds. But obviously they limit both droop and compression in theory.

 

My S3 with track pack has 250/215 spring rates. With my damper and low ride height, I have a lot more droop than compression, esp up front. I know I must be in the bump stops a lot but I've never felt a "hard" hit like I've bottomed the shock, even smashing curbs/G outs on track. That said, why not just try the track pack shock/damper setup from caterham. My car is 1200lbs and it works very well on track. The damping is well-matched to the spring rate. It feels quite stiff on road (it's no cruiser), but good on track. Definitely wouldn't want it any softer on track though. With your car being heaver and street-focused, they could be a good setup for you. Why re-engineer what caterham has presumably already worked out?

[CarYenta]

6 hours ago, KnifeySpoony said:

Don't forget to add in the spring rate from the bushes. Not sure how much that adds. But obviously they limit both droop and compression in theory.

 

My S3 with track pack has 250/215 spring rates. With my damper and low ride height, I have a lot more droop than compression, esp up front. I know I must be in the bump stops a lot but I've never felt a "hard" hit like I've bottomed the shock, even smashing curbs/G outs on track. That said, why not just try the track pack shock/damper setup from caterham. My car is 1200lbs and it works very well on track. The damping is well-matched to the spring rate. It feels quite stiff on road (it's no cruiser), but good on track. Definitely wouldn't want it any softer on track though. With your car being heaver and street-focused, they could be a good setup for you. Why re-engineer what caterham has presumably already worked out?

 

I thought about getting the adjustable race Caterham suspension which is 250/250 I think, also thought about the nitrons and Penske's and other tried and tested suspensions. Then thought, if I'm spending a bunch of money, cry once and spend a little extra to make it perfect. The MCS should have a wild amount of adjustability, so I can play with a bunch of different spring rates over time to really get what I want without sacrificing damping and having to buy yet another damper set. Why not just get Penske 3 ways 8300? I like MCS techonolgy more and don't have to pay tariffs since it's not coming from England even though Penske is a US brand. 

 

[KnifeySpoony]

I guess if you know how to tune 3 way dampers, go for it. Having a 3 way is no guarantee of perfection though. Even though I know all the theory of damper tuning, I feel I would just chase my tail trying to set it up. Suspension can be a bit of a black art with cars to me. I had 2 way penskes on another car and felt like I never got the full benefit from them. 

[CarYenta]

39 minutes ago, KnifeySpoony said:

I guess if you know how to tune 3 way dampers, go for it. Having a 3 way is no guarantee of perfection though. Even though I know all the theory of damper tuning, I feel I would just chase my tail trying to set it up. Suspension can be a bit of a black art with cars to me. I had 2 way penskes on another car and felt like I never got the full benefit from them. 

On my GT3 I had a DSC module that via laptop made the pasm dampers into 6-way adjustable plus lateral g-force, brake pressure, acceleration, steering angle lol. Talk about a rabbit hole, I spent a long long time working that system to get something I was happy with (more than 100 iterations) for both normal mode and sport mode, but it made a really really big difference even without changing the actual dampers or spring rates themselves. It ended up being that there simply wasn't enough compression stroke to make it a comfortable ride over city streets, but on the highway, it went from a pogo stick to smooth as butter.

Edited February 8 by CarYenta

[CarYenta]

Took two Bilsteins off the car. Talk about the absolute easiest car to remove suspension from! Wow that was easy. Now that I know the wrench sizes and where the bolts are, it would literally take under 5 minutes per corner.

 

Loosen rear lugs (don't really have to remove rear wheels but is easier)

Jack up car

Remove rear wheels

 

6 mm allen wrench, short for front upper

6 mm allen socket for front lower

8 mm allen socket behind the upper seat rear carpet

19 mm socket with breaker bar and then a short extension on impact

 

Shocks come out easy without any sudden jumping.

 

[Croc]

13 hours ago, CarYenta said:

The S shocks are really under damped.……

 

 

It really is nice to read a post on USA7s where I get sent down a rabbit hole of offline research and thinking with the morning coffees and Bruce Springsteen on the record player.  Thank you.   
 

To confirm (apologies if I missed this earlier in this long running thread) your use is primarily road with odd track day maybe?

 

My initial drives are confirming what your data is suggesting.  There is an odd feeling asymmetry in the front and rear under load - your spring rates are hinting at it.  It’s not as well controlled as my UK 420R which was just the standard off-the-shelf suspension package.  I’m changing to poly bushes all round and will test again as that makes it easier for me to feel what is happening. 

[CarYenta]

6 hours ago, Croc said:

 

It really is nice to read a post on USA7s where I get sent down a rabbit hole of offline research and thinking with the morning coffees and Bruce Springsteen on the record player.  Thank you.   
 

To confirm (apologies if I missed this earlier in this long running thread) your use is primarily road with odd track day maybe?

 

My initial drives are confirming what your data is suggesting.  There is an odd feeling asymmetry in the front and rear under load - your spring rates are hinting at it.  It’s not as well controlled as my UK 420R which was just the standard off-the-shelf suspension package.  I’m changing to poly bushes all round and will test again as that makes it easier for me to feel what is happening. 

That's why I bought this car, it's always interesting!

 

Yes, I will spend 99% of the time driving not on a track.

 

I'm wondering if some of the handling imprecision out of the box is the lack of a watts linkage? I would think since the car is so light the bushings wouldn't make as much a difference as they would on a heavier order car like an e36 m3.

 

18 hours ago, KnifeySpoony said:

Don't forget to add in the spring rate from the bushes. Not sure how much that adds. But obviously they limit both droop and compression in theory.

 

I stuck my bathroom scale under a front wheel without a coilover on it, and there clearly is bushing force limiting movement. Lowering the car from the air down onto the scale, it progressively went up to 100 lb (with the wheel on) before it was at what looked like a full compression position. Dead lifting the unsprung wheel by hand, it felt stiff and with resistance to movement.

 

 

[Croc]

4 minutes ago, CarYenta said:

I'm wondering if some of the handling imprecision out of the box is the lack of a watts linkage? I would think since the car

Early 620s had a Watts Linkage.  Phased out due to cost I believe. I drove the 620R Watts linkage in Portugal and Spain after it was first released (refer write up in library - track day report).  It felt better than the 620S I am trying to sort now.
 

Poly bushes are good for improving feel.  You feel what a suspension is doing and not a couple of rubber rings providing artificial suspension.   

[CarYenta]

52 minutes ago, Croc said:

Early 620s had a Watts Linkage.  Phased out due to cost I believe. I drove the 620R Watts linkage in Portugal and Spain after it was first released (refer write up in library - track day report).  It felt better than the 620S I am trying to sort now.
 

Poly bushes are good for improving feel.  You feel what a suspension is doing and not a couple of rubber rings providing artificial suspension.   

Which bushings are you changing to? Powerflex looks like the go-to? All bushing points? Do you have to take each suspension part off and stick it in a press or can you do these while on the car? I am always looking for ways to make more squeaks lol.

[Croc]

4 hours ago, CarYenta said:

Which bushings are you changing to? Powerflex looks like the go-to? All bushing points? Do you have to take each suspension part off and stick it in a press or can you do these while on the car? I am always looking for ways to make more squeaks lol.

Making squeaks?   I only do that to my passengers!   Only one that didn’t squeak was @Vovchandr‘s better half @FasterThanVov.  She is obviously used to going fast as a driver.  @S1Steve did you squeak?  
 

Yes I have always used PowerFlex brand on my Caterhams since 2007.  No squeaks ever.  I always lube the bush before I insert (that does read vaguely ooo’errr).  I always pull off the parts and use a press to do  it properly.  Ensures the polybush stays intact while fitting.  
 

If you look after your bush and lube well annually then polybushes last a long time.  Still on the original set on my 2010 Caterham with no wear to speak of.  Caterham rubber bushes wear and fail really quickly. 
 

PowerFlex USA sells all Caterham bushes out of PA. USA website.  

No squeaks ever!!!

[S1Steve]

1 hour ago, Croc said:

Making squeaks?   I only do that to my passengers!   Only one that didn’t squeak was @Vovchandr‘s better half @FasterThanVov.  She is obviously used to going fast as a driver.  @S1Steve did you squeak?  
 

Yes I have always used PowerFlex brand on my Caterhams since 2007.  No squeaks ever.  I always lube the bush before I insert (that does read vaguely ooo’errr).  I always pull off the parts and use a press to do  it properly.  Ensures the polybush stays intact while fitting.  
 

If you look after your bush and lube well annually then polybushes last a long time.  Still on the original set on my 2010 Caterham with no wear to speak of.  Caterham rubber bushes wear and fail really quickly. 
 

PowerFlex USA sells all Caterham bushes out of PA. USA website.  

No squeaks ever!!!

The only thing squeaking was your front tires from having an extra 230 pounds of counter weight in the passenger seat..😀