I'm having a heck of a time finding a good damper solution for my 1993 Mitsubishi Lancer Evo 1. So few options remain other than stuff built with parts from Taiwan, and the good options (Aragosta/AST and a bespoke Ohlins kit) are inflating out of reach.
My car currently has a set of Toda Fightex DA-G dampers. These are a pricy 'gymkhana' damper that come from the factory with a default 12k/10k combination. I got them from a parted out race car with 500 km of use as 12k/12k (unsure if they were ordered with custom valving to match), and I now have them flipped to 10k/12k. These are definitely race-oriented dampers and are not suited to our bad roads, even turned down to their softest setting. It's fine on smooth roads and okay on bumps, but it's terrible on rebound (dips and potholes, etc). I have maybe 2,000 km on them and haven't driven the car in a decade. When I bought the dampers 12 years ago, the character was fine, but I'm old now and it's not a race car anymore.
I can't find any good examples of people softening 'race' dampers. I admit I'm not great with valving windows and understanding how to match damping to spring rates, but I assume the valving is pretty stiff on these. Am I pissing into the wind by trying to step down from 12k/10k to 9k/7k to make it more civil? A re-valve is probably out of the question if I have to send them back to Japan for service. Help, anyone?
Yes, going softer on the springs will help a lot.
I don't know anything about the valving on those particular dampers, but those spring rates are way up there for ride comfort.
For reference, here's the progression we took on out Triple Threat ND project, while balancing track performance vs street use. And that's for a car with SLA suspension with much lower motion ratio than your struts. You are getting way higher wheel rates out of those already-high spring rates.
For comparison, I bought a Miata ND-RF that came with coilovers. Springs are 6K/3K, and it's not bad on the street. It will likely never see a track day. Your proposed 9K/7K is still plenty stiff.
I have some re-valved by Redshift Motorsports BC coilovers on my Track Mirage which is the same suspension geometry as the CE9A. I'm running 2178 LBs at a 62/38 weight distribution.
I've got Swift 7F/6R on it and it works decent enough to be driven on the street and is really playful on the track with the factory 16MM front/12MM rear swaybars and a little toe out up front. With the extra 500ish LBs of the CD9A, I'd try out a 8 or 9K up front with a 7KG in the rear if you want to keep it trackable. Otherwise you should be fine to run that at the 7/6 that most of the street coilovers run at. Stock those ship with a 12K F 10K rear so those usually have a 3-4K varience window on better coilovers before you revalve.
This is all very helpful stuff.
My Evo is 2560 lbs (64/36 with driver) and I'm topped out at 215mm tires. It will be on stock 16mm Evo 2/3 front sway bar and Whiteline 20mm rear sway bar. With damping adjustments, it's neutral and fun to play with on the current spring combination, it's just terrible to live with. We get a lot of influence from the Evo 7-9 crowd, who really like the 10k/12k combination on Ohlins, which are now 9k/9k from the factory. The Ohlins eat 10k springs and spit out comfort, so spring rate itself isn't necessarily the problem. Granted, they are mostly around 2,900-3,000 lbs and can run 265mm tires pretty easily, so not exactly the same thing. I had Aragosta 'Type S' dampers (AST 5100 equivalent, I think?) ordered with a 7k/6k combo, up from the default 7k/4k combo, but the vendor came back wanting more money, so I pulled the plug.
Stock Evo 123 springs were roughly square around 3.5k/3.5k, and may have actually been higher in the rear than the front. The rear shock has a lower motion ratio than the front strut, around 0.86 from what I recall (don't quote me on this). Most street-style for us coilovers are 7k/4k area, and most dual-use are 8k/6k area. At 9k/7k that's a bit more spring, with a 5k swing in rate out back from what is on there now. On paper that's great, but the worry is still an overdamped shock for the now lower spring rate, which might ride equally bad?
In reply to CanadianCD9A :
Do you have someone that you can borrow springs from to test? I'd let you borrow some if you were closer.
If square works well today and you like the feel then I'd keep it square just softer. I would be surprised if something like 8K all the way around would be too much spring for the shock. My Evo 9 is a completely different on what it wants from a setup so I wouldn't compare it to that.
You are about right on the motion ratio. I measured mine at .87
No idea on your actual question, but just wanted to say that I needed a Toda flywheel somewhat quick a while ago. Every big well known shop in the US quoted me either NLA or 6 months delivery. I sent an email to Toda Japan and, not only did they respond within hrs, but 3 days later I had a brand new flywheel in my doorstep. I was VERY impressed.
I would send them an email and maybe they have options for you.
