hancheyb

Wanted to do a quick update on the Evo. We're waiting on rear top mounts to test with the rear suspension, but we had enough time on Friday afternoon to get the fronts on. By "we" I mean "me", Fair was hiding selling something or designing something so he said. Gosh! ha!

We installed our new camber plate and AST 4200 double adjustable shocks. For this first install we used Hyperco 7", 450 lb, 60mm ID springs. Not sure where we'll end up but that's where we'll start. AST 4200s are monotube, nitrogen charged dampers. They run the same components (piston, shims, etc) as the higher level 4300s that cost $2,000 more. This set in particular is designed to be internally adjustable so we don't catch as many TT points. A future set of 4200RR (remotes) might be installed for testing at a later time.



The spring perch was moved up to almost seat with the spring platform when installed. This lowered the car approximately 1" from stock. I didn't want to lower it too much with stock height still in the rear. We'll finalize various spring height combinations depending on what dealers and customers ask for. Yes, we're aware of driving with such drastically different rates and how that affects handling, ride, etc. This is just to test fitment, etc. We'll put the package together and head out to the track over the holidays if all goes smoothly.

The camber plates had our typical range of just over 2.0 degrees of change per side. I didn't get to check caster yet, but we did design it to provide stock caster and one adjustment for more caster. With the strut eccentric maxed out the car sat with -1.2° of camber and maxed out at -3.3° of camber. Since the eccentric gives you some range we will probably change the camber plate to have a final max of -4.5° and then -2.3° or so. If you change the eccentric bolt then you can get back into the stock spec range. The other side of the car had the bolt minimized and it was only at -0.9°. So you can see we have a large enough range to give you street and track setups. No one ever runs as much camber as we do, but we've seen situations where some tire/surface combinations require it. Usually it is for autocrossing, and this car will be doing that as well.



I drove the car over the weekend, granted all the testing was street driving on 5 clicks from full soft rebound, 0 on compression. We have 12 clicks total rebound and 12 clicks compression. The car rode extremely well passing the "spouse test" with flying colors. She had no idea anything had changed on the car which is what we were shooting for. That likely means we can go higher in rates helping some of that lean in the 3600 pound Evo.

Here's where it sits at the moment. Lowering the front really helps visibility. The Evo sits up so high, us shorter torso folk can't see over the huge, flat hood.




We'll have a followup on our tuning day at Cobb Tuning last week. We're testing the Access Port on our MR, one of the first MRs that Cobb has tuned.

Fair

One more benefit - this mod is also making the car lighter:


19.4 pounds for the OEM strut, spring and top mount


13.1 pounds for the AST 4200, Hyperco spring and Vorshlag camber-caster plate

Nice 12+ pound drop of unsprung weight off the front axle.

Fair

Dyno testing for the baseline setup and First Dyno Tune at Cobb Tuning. The EVO still has the completely stock exhaust and otherwise is "as delivered" from the dealer.


click to enlarge

+50 whp peak and more power everywhere. Car already felt good at all engine speeds but feels amazingly good now.

Dave Mac

iTrader: (2)

Wow Terry. It looks like the torque curve really shifted to the left a bit. I'd imagine the car feels like a beast now. You could gain another 20whp with an exhaust and intake. Cool.

kekek

iTrader: (22)

No helper or tender on the frt damper??? Got a good reason to skip one?

Dave Mac

iTrader: (2)

John-

Remember my Ohlins didn't have them.

I might be checkin out a set of AST's for my 135.

brian94ht

iTrader: (4)

Based on the space btwn the upper perch and the top of the spring, I would say he is waiting on the helpers or the spacer adapter btwn the two?

kekek

iTrader: (22)

Mine don't currently, nor did my Tein Super Racing. Nor do ALOT of the coilovers out there.

Just because they didn't have them doesn't mean the car wouldn't be better with them. The total lack of droop, especially with high rate springs contributes to lots of skipping and lack of compliance in bumps. I prefer to have some, personally.

I'm really just curious why AST chose not to run them, especially with all that extra stroke.

Dave Mac

iTrader: (2)

True, true. The more I study suspensions for ST cars the more I think they'd be better off with more droop and helpers. I guess Terry could be waiting for a helper spring and adapter as theorized above.

Fair

Yea, its just better everywhere. We've got the new exhaust bits we built waiting for us to tweak and install them.

Weight. Cost. Lack of Need.

But let me preface this with this statement: we aren't done with this suspension installation yet (rear isn't installed), much less the fine tuning of this setup. In the end we may in fact need tenders at either or both ends of the car.


At this ride height setting the spring is unseated from the upper perch at full droop, and a tender spring would fix that. This spring setting ended up being way too low (picture at right) and at the final ride height (much higher) the main spring did touch the upper perch at full droop.

If you're not going to lower the car very much tenders sometimes aren't needed. At the final ride height the EVO ended up at (see below) and with the 7" long 450#/in spring, at full droop the front spring is still touching both the upper and lower perches, so there would be zero benefit with a tender added. If the main spring never unseats at full droop then a tender is pointless.


Final ride height was much higher than the first iteration.

This isn't always the case and we do offer tenders on most coilover strut set-ups, but wanted to try this without and it worked fine. If the car was run any lower, tenders would be needed to keep the spring seated at full droop and we will offer them as an option on this kit when its in full production. If in doubt, and if wheel/tire room isn't a concern (adding a longer spring or tender can often make the spring package sit below the top of the tire, limiting wider wheel & tire room inboard), then adding tenders would have no downside other than their extra cost.


Tire off the ground. This situation should be avoided at all costs. (this was a prototype test car that later got tweaked)

Once we autocross the car with this new setup, if we notice a wheel leaving the ground (never good) we may have to go back and add more droop travel and tenders. The rear is where we'll probably need to concentrate the most, as they tend to come off the ground on these front heavy cars that are lowered a lot. More than likely the rear will have tenders then.

Cheers,

kekek

iTrader: (22)

I guess with a 450 lb/in main you'll have a fair amount of droop in the front. If the spring was unseated though and you have no tender there is no load at all on the tire.

When you start raising rates into BSP/SM land you begin to lose quite a bit of droop due to the rate increase. This is one place where I think a tender (not helper) can help.

As for tire clearance, I am all too aware of the fitment in the front. Hoosiers are damn wide at the bead/sidewall.

GTWORX.com

iTrader: (35)

You got a 135 Dave? Sweet!

Anyway, your Ohlins were dual height adjustable (and had very little droop anyway).

- Andrew

hancheyb

Ah ha. Here's the problem, definition of helpers and tenders. kekek gets it, but just so everyone understands the difference btwn the two. A true tender spring is not bottomed out at static ride height. A true helper is really just a spacer that keeps the springs from banging around at full droop. The problem is most companies say they sell tenders when they are really helpers. We're lazy and mix the terms too just to avoid confusing people.

Here's the rub. On a performance vehicle, full droop is almost always achieved in one condition, when the car is on a lift. When you start adding sway bars, increasing spring rate and rebound in the damper, you almost never use the full stroke of the shock in a track or autocross environment. You are simply not in that condition (wheel off the ground or unloaded) long enough to see the spring unseat.

Now, for a car that is track and street driven the helper is nice to have so in those odd situations like big dips in driveways or giant dips on highways, having the spring always seated is a good thing, keeping everything quiet and not risking damage to the perches, etc. Performance-wise *most* helpers offer little help in keeping the wheel on the ground.

We actually DID get sort of a hybrid helper to work on our STS E30 318is (no limited slip allowed). We made some custom length rear shocks (extra droop) and ran a heavy helper on the rear with very little rebound. It was bottomed out (barely) at static ride height so that it offered *some* force on the inside rear. The car could be flat footed out of turns, granted it has 130 lb-ft of torque. This was a very unique application driven by the rules of the SCCA STS class. I'd never recommend that setup normally, but for custom apps it worked well.

Currently the front of the Evo is running around with the 7" Hypercoil spring touching the perch (always in contact) and no helper. We always offer helpers as an option and if you want to lower it more (like Fair said) we recommend it. The car with camber plates and 4200s is quieter (and rides better) than it was with the stock Bilsteins. And since the spring touches, there's no banging around, ever.

Now for the true tender. We likely won't do it in the front because of the packaging issues. The springs end up running so far down the strut you lose the option of running a big wheel and tire. For the rear, a true tender might work well for the X because of the AYC's tendency to allow almost too much turn-in at corner entry and some awesome push at exit. Obviously in stock form they have different parameters to work with than we do. This seems to get worse the more aggressive you are with the car. If you drive smoothly you don't notice this as much. Therefore, we might bypass the rear tender and set it up for a smooth driver using our ability to control compression and rebound valving instead since that is what matters the most in transitions.

Final parts should be in this week and I'm hoping we go to the track next week if we're lucky. Sorry for the long post, I don't get to post often these days.

weneversleep

Wow, really great thread guys. As I've told you before, I know where I'll be sending my X MR when I'm ready to prepare it for the track... but I'll let you guys do all of the prototyping and testing first.

I need to make a trip up to Dallas. Vorshlag, now Cobb... I also want to go drive ECR soon...

--michael

Fair

Lightweight Battery install


Left: OEM battery. Right: The Deka ETX18L we used instead

A common autocrosser/track trick to lose weight from a car is to use a lightweight AGM style battery in place of the stock unit, when allowed. The Original Equipment batteries used in most modern cars (which can range from 35-55 pounds) are usually a cheap lead-acid wet cell battery, spec'd to work in extreme hot/cold and to have a lot of reserve power - so you can leave your lights or hazard indicators on for a long time and still be able to start a car at -30°F. With smart use in "engine off" situations, racers can deal with a bit less reserve power and we tend to use much lighter, high cranking amp mini-batteries that are made for motorcycles.



The Absorbed Gas Mat (AGM) style batteries can deal with more vibraiton and do not de-gas (Hydrogen) like a standard wet lead-acid battery, and they tend to work better in racing environments. We've used many brands over the years but have noticed that a lot of the higher cost names are just rebadged batteries made by a select few battery manufacturers. The Deka AGM battery we picked for the EVO X is one we've used in a number of our other cars, including our V8 powered BMW. They work well for the relatively mild winters and hot summer weather we see here in Texas (15°F to 105°) and usually last 2-3 years of street/track/autocross use. A $10 low amperage trickle charger (a "battery tender") is a good idea if the car sits for more than 5 days or so without being used.



The factory battery mount was surprisingly versatile and simple (stock design used J-hooks that you can get at AutoZone!) and with little more than a spacer block (with a shaped cutout to grab the narrower Deka) it worked great and took all of 15 minutes to swap in. I'm not showing the spacer up close and no, we are not going to be selling this part. Yes, it will even pass a tech inspection - something most homemade battery mounts rarely do.

This Deka battery cost about $78 and the Werker SAE top post adapters (automotive style brass posts that convert a motorcycle battery for automotive use) were another $9. So for about $90 we dropped another ~17 pounds from the car. Yes, it removes weight off the rear, but we always go for the lightest legal class weight at all costs (esp. on this heavy EVO!) rather than strive for the "perfect weight balance" by adding weight (which is not beneficial). Car started great and has been working fine for street use.

Cheers,