V-12 Engine into 308 Build, over on Grassroots

That is where the pedal box bolts bolts on. I pulled and the steering column out to make access a whole lot easier.

 

Thanks Mark,, that’s what I was thinking but wasn’t sure..

 

Well, I was feeling bad about wasting my time on steering with the engine sitting and checked on my mcmaster order for the lapping bar......it jumped back up to 3-4 weeks with Apr 6 the date....plenty of time to finish the steering

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The fast steering is basically done....just a little cleanup on the cover and then final install
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it works well


and in other news I ordered a set of 600lb/in front spring to replace the 450s hoping they better match the 400lb/in rear springs. Also I'm about talked into a new front sway bar to go with......almost......

 

I'm close to pushing the order button for a much stiffer front bar....its in the cart.....

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Do these fit the stock configuration or have you modifies the connection points? (In other words, would this set fit my stock car?)

 

Maybe and that is part of my hesitation. I don't know and can't find the bolt spacing on the pillow blocks to understand how easy they are to bolt to the frame. I also am unsure about the arms that go on the end.....the 308 front bar has an odd shape and the arms would probably need to be bent but that changes the strength...which brings me to the final uncertainty around stiffness. Calculating to match the hollow bar to any given solid bar is pretty east, but I'm not so sure how the ends are contributing exactly....I might need to do an FEA model to help finalize.

But assuming the arm can be bent and the pillow blocks installed, then yes it would be a bolt-on.

 

I just noticed they do offer custom arms but don't show a price. I need to get my steering hooked back up to check clearances and see what exactly will work.

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Here's where the car is with the new front springs....1.49Hz front, 1.42Hz rear.
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the ref I found is:
passenger car: 1.0
sports car 1.25-1.75
low/no down force autoX, roadrace 2.0-2.5

stock subaru brz 1.45 so my new SUPER stiff springs are nothing like super stiff and are actually what would be considered a soft spring, stiff bar setup I guess.

To get to 2.0Hz would be 1100/900....that's a lot of spring compared to what I here people are running on these cars! Another way I've done the math is 4" travel is good, and should have 1.5" sag max with 0 preload, that pops out 715/595 and says my new front spring belong on the back and I need new new front springs. The other end is 1" sag min with 0 preload pops out 1073/894 which matches the 2.0hz numbers...funny how the numbers all match up

With my current 450/400 springs the numbers are 1.29/1.34.....so the rear is stiffer than the front which certainly explains the oversteer issue.

 

So...speedway called me today to let me know my springs would be delayed, they only had 1 in stock but more had just arrived, 1-2 days. I decided that was a sign from God/Enzo that I ordered the wrong springs and was getting a chance to correct the error. The stiffest springs I could find that fit my shocks were 900lb/in, so I ordered 900/750 that put me at 1.2" sag and 1.83hz front and rear. With such a big change in the springs I will put the swaybar project on hold to see what I have before making more changes.

 

Holy Crap! Make sure you have good dental insurance.

 

LOL, it should be fine.....I've set street cars up stiffer than this before. I decided I've been listening way to "them" way too mcuh when I should have been trusting the math. My SUV has firmer springs than the 308 even after I doubled the OEM rates....that's shouldn't be.

What you feel, what knocks out fillings (which I don't have btw ) is the compression damping in the shocks. For some reason a lot of places think they need to increase the compression damping proportional to the spring rate increase and create horrible driving cars in the process. That's just nonsense or perhaps they have no choice, there is a reason good shocks are expensive and control is that reason.

The point of compression damping (IMO) is to prevent the tire from leaving the pavement at the top of a bump so its about the mass ratio between the sprung and unsprung weight and has basically nothing to do with spring rate. My shocks are very close to stock compression damping and as a result the basic feel over bumps is about stock even though my current springs are double the OEM spring rates and the new springs shouldn't change that much I don't think. below are my shock graphs, the oem koi is the black line on the top graph, the purple on the bottom graph....very little change.

What was changed and I may change more is the rebound (the negative numbers). The different lines are different settings in clicks. The shocks go 0-35 clicks, 3-33 is considered ok, 6-25 optimal so if you get out of that range they recommend a re-valve. The rebound is what damps the springs and it the recovery from the bump, not what you feel hitting the bump. Here too little and the car will sink a bit over multiple quick bumps as the suspension doesn't recover fast enough, too little and bounces a bit....not sure I have enough rebound for these springs, it will be close but its easy to have them re-valved to whatever spec.





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I had an error in my spring spread sheet and the springs I ordered are kind of stiff and mismatched


It looks like the 900 front should pair with 575 rears and yield 2.6hz which is kind or moving into downforce car territory.....but still softer than the simple sag math suggests I want. I generally prefer stiffer springs and small swaybars so I'm going to let this order roll I think.

A buddy has 580/380 and that is 2.1Hz....so kind of the other end of the autocross/track range spring wise with 1"/.875" sway bars and says its good. With the heavier springs I'm going to stay where I am swaybar wise, 3/4 front, nothing rear and see....I suspect it will want a bit more front....but I need a running engine to be sure.

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The question now of course becomes where to set the ride height? Stiff spring means it will tolerate a pretty low ride height.......hmmmmmm

Still working on the steering a bit. I dropped a u-joint bolt, it fell into the throttle pedal floor opening and I heard it roll....I've having a bit of trouble recovering it and its an odd bolt so I'd like it back. A new flexy shaft magnet is arriving tomorrow. I have the fiberglass cover installed and as I suspected the top mount bolt is a challenge, I think I have a plan...will post pics when I get a bit more done.

 

I'm mystified ...
All too often I read about the simply huge increases in spring rates specified, not only by individuals, but also damper manufacturers. And whilst the Europeans (and specifically the Germans) seem to have penchant for uncomfortably high spring rates, you guys in The States take the fetish to a different level altogether

I've owned and driven a good few Porsche 911's over the years (both aircooled and watercooled) my favorites being the 964 RS from 1992 (not imported into the US of A) and the Mk1 996 GT3 from 1999 (again, not imported into the US of A).

The 964 RS was a stiffly suspended car, and most now consider it to have been "before its time" as it was a stripped out, lightweight, focused street car which subsequently proved to be perfect for use on the burgeoning trackday scene that was sweeping across Europe. It was THE most connected road car I've owned, (I owned 4 of them over the years)

I loved the car for its manual rack and pinion steering (LHD cars ony) its ultra responsive 260hp engine that made the 2 valve carbed 230-255hp (depending how you chose to measure those horses) of the 308, feel disinctly lack lustre. The perfectly formed bucket seats and huge 965 Turbo/928S derived brakes only added to what was an exceptional package.

But the suspension proved to be divisive, the journalists who drove it at its launch were scathing, most saying the springs and dampers were far too stiff, and whilst they were certainly the main culprits (specificially the compression valving of the dampers) the solid monoball strut top mounts didn't help, nor did the uprated bushes in the front and rear suspension. The adjustable sway bars seemed overkill for a street car, and on fast cresting, bumpy roads, pretty much any econobox sedan would leave the car from Stuttgart for dead. But on smooth twisty roads, the car came into its own and was an absolute joy to drive, and it's grip with 255 rear and 205 front tires was almost otherwordly, and all this was allied to the most fabulous manual steering.

Fast forward seven years and Porsche had embraced water cooling 2 years previously, but stung by accusations their products had gone soft, they rolled out a 996 with an altogether harder edge in the form of the 996 GT3.

The GT3 may have had a harder edge, but compared with the 964 RS, it still felt soft.
I subsequently bought a GT3 in 2005 and enjoyed it, but felt it could be improved in the suspension department. Fast forward 5 years and I decided I needed to fit the ultimate suspension to it, solely I may add, for street use.
I found a set of 3 way adjustable, remote canister ex-996 RS Ohlins racecar dampers for sale at a reasonable price (when they were new back in 2001-2002 they would have cost $15,000, I paid $3,500 for them)

I didn't even try bolting them on the car as I could tell the spring rates were crazy high. So I took them to an Ohlins service center and asked them to rebuild them for street use. They contacted me several weeks later to give me the quote for the rebuild. That quote included new rear damper bodies and shafts, because despite being told by the vendor the dampers would bolt straight onto my roadcar (techically they would), being race dampers, they were roughly 3" too short !!

Having negotiated the cost of the rebuild somewhat downwards, we got onto the subject of spring rates.
I told the center I'd purchase a brand new set of OE springs so they could dyno them and let me know their rates, difficult because either the fronts or rears (can't remember which) were progressive rate items).

When he told me he'd dyno'd them and gave me the figures (182lb fronts and 548lb rears) I popped into to see him and then told him that's the rates we'd be using on the dampers.

He laughed... but rapidly stopped laughing when he realised I was deadly serious.
He then told me they'd be "waaaay too soft". So I asked him how so when they were near perfect when coupled with the OE Bilstein dampers...?

"They'll be hopeless on track" he replied. I responded by saying that's fine, because the car wouldn't be used on track ...

Once he'd conceded and accepted these were the rates we'd be using, he made one final caveat "If they're too soft you'll have to have them re-sprung and re-valved too, and it'll be at your expense"

"Fine" I said as I walked out of the workshop without so much as backward glance.

Once he'd rebuilt the dampers and they'd been fitted to the car, he accompanied me in the car to carry out the final adjustments to the bump and rebound settings, and when we got back from one of my favorite stretches of bench-marking black top, he admitted just how good the set up was.

In my very humble opinion, race and damper engineers rightly focus on making cars go as fast as possible around circuits, but making a car work well on our unique roads here in the UK is a very different discipline altogether.

Some years later I lent the dampers/springs to an individual on appro. He tracked the car with the dampers on the car, and I was lucky enough to passenger with him. To say the car was impressive would be an understatement, it road the kerbs like a magic carpet, and far from being too soft, the springs and dampers were perfect apart from the rear end getting slightly squirrely exiting one high speed corner.

The individual who sold me the dampers originally, told me the benefit of really high end dampers is the ability to run soft/er springs and "prop the car up with the dampers" and control the roll with sway bars.

All of which is very long winded way of saying, why do most feel the need to fit springs with such high poundage rates to their cars, when they don't appear to be necessary ?

 

funny you should mention shocks that were too short....as I was driving home I was thinking I need to check mine to see if they are short enough for my plans.

Spring rates and damping rates are a bit of a preference thing for sure....but also for sure once you've raised the car 3" it will be slower in and out of the turns. When you lower the car there is less suspension travel available so the suspension needs to get proportionally stiffer or you spend most of the time on the bump stops

A stock 308 is one of the worst handling cars I've driven with suspension tuned much more for comfort than performance....I was competing for the slowest car at the autoX. It was embarrassingly slow. The stock springs are about 200lb/in iirc which is about 1.1-1.2 hz depending on car weight...below what could be considered a sports car, 1.0 is a luxury car. Very soft and takes for what seems like forever to settle into turn so its never settled in quick switchback, just kind of floundered and rolling its way through the course.

But how much stiffer to go?....yeah, I won't even pretend I have the answer. I tried a 350/250 setup which is about 1.7hz, more toward the top of OEM sports cars and it was much better, good enough for a win in class but still felt pretty loose and certainly not competing for streetcar time of the day . Then the 450/400 setup which is 1.9/2.1 so a bit mismatched and just getting into what is considered autoX or track worthy.....still loose and even out on the street felt just fine, smooth enough that 1 friend said "I thought you put heavier springs in this thing, did you take them back out?"...so its not just me, it was plenty soft. The new springs will be 2.6hz and at the top for street tire use. If they are too stiff I can do a 700/450 setup at 2.3Hz using the 450s I have or maybe 625/400 at 2.2.....somewhere it the 600-900 range on the front seems right, at least for me personally.

As I said in the other post, I think a lot of what people are reacting to is excessive compression damping not excessive spring rate when say think the setup is too stiff. I have done street cars stiffer than this with no issues and this isn't going to be used for cruising down the highway for hours. worse that happens is I have to buy another set and I'm out a $150.

I'm kind of leaning to setting the ride height at 4.5"-5" for the street and try about 3" at the autoX where the rule I just learned is "Tag the ground at least once on the course".

 

On the basis of the various videos on YouTube of Grp 4 308's spinning, or certainly "suffering" with huge amounts of oversteer, one has to wonder if those massively wide Michelin TB's aren't up to temp, the rear dampers are way too stiff (ditto springs) or the rear sway bar is too stiff, or the individuals driving them, are amateur gentleman drivers who aren't particularly able behind the wheel. Certainly in European rallying, whether on gravel or Tarmac, the old adage is to "Keep the car as soft as is practically possible to ensure traction is maximised".

There is caveat to my lengthy initial post above though, if you want to run low spring rates and rely on the dampers to prop the car up, you'll need top quality dampers to pull the trick off, a set of cheap adjustable coilovers won't afford you the luxury ...

I have to admit I have a damper fetish, and my experiences with the expensive Ohlins dampers on the Porsche convinced me of what others had told me previously, that being decent dampers are all too often misundertood and overlooked. Their fitment can be far more beneficial than that modified engine that cost $10,000 and provides another 50hp, but all to often the additional power it provides can't be deployed effectively (especially on something like an AutoX event) purely because the chassis and its dynamics are so poor.

As you've most likely experienced for yourself, the fitment of truly high quality dampers to a car can totally transform its behaviour at elevated speeds, and provide a magic carpet ride into the bargain. Regrettably they're all too often overlooked, or not considered "cool".

 

Yes, there is a reason one of my first upgrade was a set of Ohlins shocks. They are only single adjustable but still quite nice and on setup where I had more adjustment I rarely touched anything but the rebound so these seemed fine. When I was race motorcycles the upgrade to an Ohlins shock was night and day....like a 10%hp bump leaving the turns and all or a sudden most of my passes were on the front straight because I could take a nice run at them exiting the last turn. Good shocks are critical.

Also as you say, as soft as possible on the springs to maintain as much compliance and grip as possible....but you still need to get in and out of the corners fast which tend to push you toward stiffer setups. Everything is a compromise and the best balanced setup generally win in the end.

 

So I just went out to check something else and realized I'd misremembered spring lengths so what is on the way is wrong

right length now coming (6in/8in to replace the longer 7/10 I currently have)...and you guys scared me a little so they are now 800/500 which is about 2.5hz. The 800 is a number I remember was offered as an option from the guy I bought parts and the car from 20 years ago so for sure that is a tried and true 308 spring choice.

 

A nuisance, but maybe for the best ?
I do wonder if the standard 308 chassis (and specifically the GTS) is sufficiently stiff both torsionally and flexurally to work with springs with high rates ?

MAT undertook finite element analysis of the chassis prior to designing the FIA cage and the additional strategically placed strengthening members, to improve safety and the strength of the chassis on their Michellotto replica builds.

 

As I was saying earlier, there is no magic or "right" setup. The 800/500 is a bit of a safer choice and will want a bit more sway bar probably but I'd probably never notice the difference, I'm just not that good of a driver.

The chassis is for sure not as stiff as I'd prefer it was....but to be brutally honest, most of the time when people start blaming chassis stiffness it BS. What a flexy chassis means is setups tend to be inconsistent ..traction changes, flex changes, camber changes, that kind of thing. Yes the 308 is relatively flexy by modern standards and yes the GTS is worse than the GTB....but its not terrible, its not actually an issue most of the time. You could never possibly feel it with stock suspension setup. This is an at the limits kind of issue which basically never happens on a 40-50 year old car, its just what people blame for poor driving skills. I had no problem bringing home class wins against modern cars and as I said, I'm not a particular good driver.

 

I should probably add this bit....when you feel a stockish 308 squirming and rolling around what you MOSTLY feel is the high profile, soft sidewall tires. That is 70-80% of what you'll ever feel in any car. After that the springs are tuned for comfort on the highway, way too soft to let the car actually respond to driver input in a timely fashion. The shocks aren't too bad and pretty well matched to the factory springs as they should be, but because the springs are soft the shocks end up with too little rebound which again means the car takes a long time to settle. Together they form the "flexy chassis" feel. After that is all fixed, the chassis is flexier than preferable and will cost you a second or maybe 2 a lap compared to what you'd have if you went through and did a full race prep with a well done cage....but all the other stuff is costing 10+ seconds so the car can be made WAY better before you can really even find the chassis issues. Its just not on my to-do list.

If you want to convince yourself a quick way to see it is put the car up on jackstands on the frame about in line with the axles. Then put a jack under 1 front corner, , remove the jack stand, and a add a dial indicator to each front corner to see how far up you can move the jack before the corner still on the stand lifts. I've not done it and my engine is out so is won't work on my car right now....my guess is 1/4"?, which is a lot in race car terms, but on the stock setup the wheel+tire flex travel is about 8" so 3% is frame flex is torsion, about 0% in bending (when the 2 front or rear tire hit the same bump). That is not something most people, myself included) can feel. Maybe I'm way off though...I'll measure it once the engine is in to be sure if no one else does in the meantime....its going to be a small number though % wise in stock suspension. It will be more like 10% on my setup I'm guessing which will make tuning F/R swaybars and such a bit much challenging and inconsistent but that is why god gave of adjustable bar options. We'll see for sure once I have real numbers.

 

It'd be interesting to do the experiment. My 996 GT3 would "3 wheel" driving across the sidewalk to get onto my drive. But it was low, stiff (bodyshell and springs) and had limited droop.

 

Why is it that the stock Konis only have adjustable rebound? Why might I want to adjust rebound given that everything else is unadjustable? It there is only one thing to adjust, I would have expected it would have been compression.

 

To be 3" wheel travel means you're springs are tuned to about 2.5hz, exactly the spring I just ordered for my car. This means wiht the springs set to 0 preload (they are loose when the car is jacket up) you lower the car until the tire touches the ground and mearsure the height, then let it down and give it a bounce and remeasure....it will have dropped about 1.5"... little more due to tire flex. That is about the stiffest they suggest for non areo effect setups. In use there will be about 1" flex in a modest sidewall tire so maybe 4" total.