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PostPosted: Thu May 01, 2014 3:24 pm 
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Howdy all,

Thanks everyone for your input, much appreciated. I have scored some 925lbs king springs which should assist in the cause. I just need some Shocks to suit...

Im thinking of going with adjustable KONI yellows but which ones??

DAT04 you mentioned that you use KONI yellows which is what someone else has also recommended also. but how do I know which ones to use and you also you said that yours are modified Commodore ones. Did you modify them yourself? if not who can modify them ??? do you have a part no.?

SR20Datsun - A part no. would be good! As Im in Sydney


FeZ

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PostPosted: Thu May 01, 2014 10:53 pm 
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In my 1600: Commodore Koni yellow (externally adjustable rebound) have part number:
8041 1094 sport


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PostPosted: Thu May 01, 2014 11:22 pm 
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Thanks JK

Did you need to modify them?

FeZ

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PostPosted: Fri May 02, 2014 12:17 am 
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No wakkas Fez.
You don't need to modify them (other than replace the bottom bush if i remember correctly), I used them off the shelf for a while.
I ended up getting them re-valved in an attempt to cure my wheel-hop and reduce squat, and at the same time had them shortened to limit the excessive droop and keep the short/hard springs captive (just). I'm actually considering selling these at the moment as i want to try something firmer...


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PostPosted: Fri May 02, 2014 7:04 pm 
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Super wrote:
.....SR20Datsun - A part no. would be good! As Im in Sydney.....


FeZ



Hi FeZ,

Part number is 8242-1015 SPORT. These are the double external adjustables I am running. They are silver in colour (Koni Race Colour) and you can tune the shock to suit a variety of springs to minimise your axle tramp/bouncing.
You can get the supplier (ToPerformance in Vic for example) to modify the lower bush from 58 to 37mm in width, and bore the ID of the bush from 14 to 16mm. OR you can do this yourself. This will suit the Datsun rear end shock mount (lower)
The shock rebound/compression base range is a fair bit higher than the factory which should fit quite nicely with the springs you would like to test.


For example the 8010-1032 external rebound adjust range is 1050 - 450 N at 330mm/s
The 80-2299 (close to factory-ish) is only "removable" adjustable, and the rate is 300-100..
the 8242-1015 is 1100-450 for rebound and 2300-1600 for bump (if I remember the way it goes around!)

Admittedly, the price of the double adjustables is just over 3 times the cost of the single adjustables... so it's up to you about how much you want to spend.

Out of curiosity, what happens if you put a load of stuff in the back of the car when you take off? Does this make any difference to the bounce?

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PostPosted: Sun May 04, 2014 12:51 pm 
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Hey guys,

A lot of food for thought here...

I have several questions though

SR20Datsun - to answer your question no I have not tried to load up the trunk and take off. I used to run 2 x 12" subs a while ago weighing 70kgs but they always came out when I went to the track as the car is quite heavy (1200 kgs). What will the added weight achieve do you think?

I can tell you that when my power output went from 240rwkw to 300rwkw this problem arose. With my current setup (615lbs and kyb shocks) this was perfect for my previous figure of 240rwkw as I was running consistent mid to high 11's. With the power increase I currently run consistent mid 11's but I feel this should much lower. Im putting it down to suspension and other changes like larger tyre diameter. I will be reverting back to the smaller diameter and Ive also sourced a 4.11 R200 (previously 3.9), with the new springs and some shocks to suit Im hoping to break into the 10's

Can you please explain to me in more detail the relevance of the adjustable rebound range. Excuse the ignorance as this is all new to me and Id like to understand suspension a little more. In your example the rebound range on all the types you listed vary significantly... How do I know what will suit me best. Say to suit the 920 lbs for racing and 615 lbs for street, is there an adjustable that will cover both.

Also what does double adjustable mean??? is there other than the rebound adjustment on the 8242-1015? And when you say 3 times the price... what are we talking here?

JK - Out of curiosity what did you want for your 8041 1094 sport?

Again thanks heaps guys

FeZ

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PostPosted: Mon May 05, 2014 6:18 pm 
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Putting a bit of load in the back is just trying to change the harmonic at which the bouncing occurs. Putting weight in the rear also compresses the springs providing a little bit more 'pre-load'. Just trying to find out whether the 180B has the same problem as the 1600 in that the rear end flaps around when you get a bit of axle tramp going. This only makes it worse as the rear (from the shock towers) isn't really that well supported. Hence the reason I put some sheet metal diagonals to strengthen up the rear.
It's a quick way of finding out if it's structural or not.

"Rebound" is the rate at which the shock extends back to normal over a certain extension speed/load/time. By having this adjustable, you can tune it to the road surface, or the spring you are running (or both). You want the system to be close or actually critically damped (do a search on google). Currently your system may be under damped, which means you need to adjust the rebound to suit the spring/system. Hence the adjustment. The range I am referring to is typically for a heavier car (the holden commodore) which usually runs heavier springs (like the 240K KDRL07 for example), so you need a rebound setting similar to this. The ranges that I provided (both the single adjustable and doubles) should provide you enough play to work with both spring rates you referred to. It's just a case of a few clicks on the top adjuster for rebound.

Double adjustable is basically a rebound and bump (extension and compression) adjustable shock absorber. It allows you to change both bump and rebound usually independently of each other. The 8242 has both. 3 times the price puts it at around $1300 ish for the pair. Well worth it IMHO.

My idea would be to borrow a set of shocks that are single/double adjustable from someone, put them in real soft on rebound (worry about bump/compression later), watch and feel the rear end bounce. Go back, put them on the tightest setting which is hopefully when you watch/feel as you wheel spin. By finding the sweet spot (depending on the spring) between these, you will have found nirvana. In some instances, you may want a little wheel spin (doesn't bog the motor down), so you adjust the shocks a little stiffer than the sweet spot. Having the shock too stiff means you don't get the car to squat (weight transfer to the rear), which usually means wheelspin!

If you can't get the car to stop the bounce, then you need a stiffer rate which means the adjustment of the hopefully borrowed shocks isn't enough and you can return them and try something harder...

The other thing that no one has mentioned on here is tweaking the front end too. The front end typically tries to come off the ground when you dump the clutch. If the spring rate/shock rate on the front isn't 'matched' to the rear, you will get a 'resonance/harmonic' and the front and rear fight against each other kind of giving you the bounce you <may> be referring to.

I've probably forgotten heaps, and worded everything really crappy, but that's what you get typing this stuff out on a phone screen :D

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PostPosted: Mon May 05, 2014 10:12 pm 
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Nice write up


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PostPosted: Thu May 08, 2014 12:23 am 
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I was going to say that your knowledge for suspension is quite impressive, but the fact that you wrote it all on a phone touch screen blows me away...

Jokes aside, thanks for the info SR20Datsun you seem very knowledgeable in this area and I appreciate your help. I have installed the 920 lbs springs and for now and used the KYB's that I have for the moment as I shop around for new shocks. I think I will end up going with the re-valved commodore yellows -8041 1094 sport. Wholesale suspension has quoted me $440 and will take a week or so to deliver from Melb. but I think I might be able to get them for a better price. The double adjustables would be ideal but they are just way out of my price range for $1800 ( wholesale suspension price).

I took the car out for a quick spin and had a couple of half assed take offs and It seems better with the transfer of power... But the real test will be at the track I guess. I think Ill have to get out and try some decent take offs before Wednesday next week.

In regards to matching the front and rear suspension... can you give me a example of spring rate / shock rate that's is matched? Im obviously matching the front spring rate / Shock rate to the rear, correct?

FeZ

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PostPosted: Sat Jun 14, 2014 4:51 pm 
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Ok I have been to the drags since reverting to the 925lbs spring and found instant improvement.

First run 11.9 - not bad for a first run
Second run 11.3 - Yeeha personal best. But still had a lot of bounce... time for some shocks!



Its a little difficult to see but on the first gear change I'm getting a lot of bounce

Third Run - at the burnout stage the 610 swung left then right then a rumbling noise followed after I backed off the accelerator. I paused for a second then continued to stage as the car seamed fine (not). The light when green and I launched it like it never been launched before! Halfway through first gear the car stalled and I was stranded halfway down the track. I couldn't start the car again as I lost power to everything.

Anyway the official came down with the Quad and strapped me on and continued to tow me off the track and through to the pits. As this was happening... I could hear a feint fizzzzing sound coming from the rear??? I signalled for the official to stop and got out to check where it was coming from. Next to the official I opened the boot and to my surprise the battery enclosure had disintegrated and the battery had fallen over and the positive terminal was shorting out on the fuel Tank!!! The official sh*t himself and stepped back lol. I quickly removed the battery before it exploded as it was very hot making a lot of sound, but the fact that it was arcing on the fuel tank really had me worried as it could have ended very badly. So I thanked my lucky stars, reconnected the positive cable to the terminal and drove home :)

Getting back to suspension I have done some serious research and I opted to go with Koni's 8210-1158 SPORT (1050 rebound / 450 bump) adjustable rebound. After speaking to Toperformance and Wholesale suspension we came to the conclusion and thanks to steve from Wholesale we found a shock that suited. Even though Toperfoemnce recommended that I get these revalved for 925 lbs springs I opted not to in an attempt to try them out first.

I was really interested in the 8242-1015 SPORT as they seem to be a great shock with the double adjustment but for the price - $1800 I just could not do it...

Anyway I installed the 8210-1158 SPORT yesterday and went for a quick test run and wow! immediately I noticed difference in driveability, I am certain this will give me much more improvement and with a few tweaks to other parts of the car like the accelerator cable (So I actually get 100% throttle) I'm hopeful to break into a 10 sec pass.

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PostPosted: Sat Jun 14, 2014 8:24 pm 
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Get that battery into one of those plastic battery boxes and also get a normal battery hold down clamp. Drill holes in the floor (and through the plastic box) so the rods hold down the battery properly.
I was able to get one rod through a section of double-thickness steel of the chassis rail under the boot floor, and on the other rod I used a extra large flat washer. These babies aren't gonna pull out!
Throw away the new brass wing nuts that come with the clamp and put on nyloc nuts and flat washers. The brass wing nuts have been known to strip.
I also use a slab of rubber under the battery.


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PostPosted: Sat Jun 14, 2014 10:51 pm 
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Hey Fez congrats on the 11.3 nice run


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PostPosted: Sun Jun 15, 2014 12:19 am 
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Thanks Adam, hows your beast goin? and when are we gonna see you back out there?

xfaxta - you're right its definitely something I need to sort out. Ive replaced the box and anchored it better than previous and I think it will do for now but I'm definitely gonna steer in the path you've gone. By the sounds of it your battery aint goin nowhere.

FeZ

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PostPosted: Sun Jun 15, 2014 8:04 am 
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I checked what I actually did with my battery box, I'd basically bolted the battery box down and used all-thread instead of the rods that came with the clamp. On the all-thread I used a nut on the inside of the box as well as underneath the boot floor, that way it won't fall through to the ground if you need to remove the clamp and battery.
The rubber sheet covers the bolt heads and gives the battery a flat base.
I used double nuts locked together on the underside and nyloc nuts at the top on the clamp. The double nuts underneath and the single but on the inside all tighten together against the floor of the boot.


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PostPosted: Sun Jun 15, 2014 9:18 am 
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[quote="Super"]Thanks Adam, hows your beast goin? and when are we gonna see you back out there?


Its going good Fez im actually hopeing to get out there for a couple of runs with in the next month


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