First off Enjoythemusic let me say your QV is one of the best looking Iíve seen. Second off congrats on getting your car closer to your ultimate goal of performance.
I have a few questions for you and also some personal experiences to relate as to the set up of your car.
One of the things you didnít list is your tire sizes. Iím assuming theyíre something between 205-255 width 40-50 profile on a 16Ē rim for the front, and 225-235 width 40-50 profile on a 16Ē for the rear. Those sizes will have a big effect on handling as well. I have the same Kuhmos on my car (MR2 Turbo) and love them. Iíll be looking forward to your impressions of the new tires. Also, did you change your sway bars?
Iíll try and tic off items as close to their position in your original post to help answer some of your questions. The weight of steering resistance you mentioned I would put at the new set up from KTR. Springs and shocks operate to manipulate bump and rebound. More on that later. Items such as steering input have more to do with caster, camber, toe (in or out), corner weight, and other things like Ackerman angle. The 308 had buckets of caster. This causes the steering to be heavy and also gives the car stability in a straight line and at high speed. Caster is the angle that the upright leans back toward the back of the car. In other words the bottom of the upright is a little bit in front of the top of the upright. When this is the case, as you turn the wheel (lets say to the right) the left wheel not only is turning but pivoting- forward and to the right. The right wheel is pivoting- back and to the right. This creates ďnegative scrubĒ. In other words the tires donít want to turn and you need more force to do so. It keeps it tracking in a straight line. The closer the uprights are to 0 deg the easier theyíll be to turn. Iíll bet anything they eliminated some of your caster. But, you're more stable at higher speeds... more on that in a minute as well.
The new bushings alone would have made a tremendous difference in the way your car handled. Old rubber bushings that are worn out can give a millimeter here and a millimeter there. Big deal? You bet! Think bout your four pick up points on each corner (two on your upper A arm and on your lower). If all of those are allowing movement of 1mm your suspension could be 8mm out of whack. And thatís just the front. Throw the back components into the mix and you can see why urethane bushings are such a good investment. So. If your car was squirrelly over the bumps Iíd say this was the primary cause. Or maybe a bad shock that wasn't quite up to par. As those old pieces of rubber compressed and flexed your car really didnít have any set camber, caster, toe, etcÖ it probably wasnít until the car took a full load in a corner that it ďsetĒ into some form of static alignment due to loads being applied to the different pick up points. Now that all of that is working properly the rest of your suspension has a chance to do what it was designed for. Which brings us to your new shocks (dampers really) and springs.
You said your ride improved. Normally stiffer springs mean stiffer ride. Are they progressive springs? Ok, hereís how spring rates work. If a spring has a rate of 300 that means it takes 300lbs of force to compress the spring one inch. 600 to compress it two inches and so forth. A progressive spring has a varying rate. Most manufacturers make springs in 50lb increments or some in 25lb. They also make springs in a variable rate. And with Coil-Overs such as yours you can get a ďTender SpringĒ and Main spring. This combination gives you a progressive rate up to the main spring rate at which point when the tender is fully compressed the main rate is the final spring rate. Confused? Go here: http://eibach.com/cgi-bin/htmlos.exe...72582100012211
Iím betting you have a progressive spring set up on your car now. Iíll bet the initial rate is softer than the stock spring and gets progressively stiffer as the spring compresses. Giving you a better ride (due to the softer initial rate) and better handling as you get more aggressive with the car (as it gets stiffer). Talk to Nick if this is what heís sold you. If not then I'd say you have a placebo effect from your new suspension.
Also you can now play with this spring set up yourself. The other new item on your car are the shocks. With, it sounds like, adjustments for both bump and rebound. I said earlier that it should really be called a damper because thatís what it does. It dampens, controls how fast the suspension goes into bump and then into rebound. I can go into this if you like but it will require a lot more explanation than I have time for at the moment. Let me know if youíd like me to talk about it though.
High speed handling. Iím very surprised your car was a bit floaty at over a 100mpr in stock form. That one I donít have an answer for. The 308 is normally a great platform for high speed driving: http://www.bobnorwood.com/Ferrari%20...the%20salt.htm
When you lowered your car you lowered your center of gravity. This is the second thing I always tell people to do if they want to make their car handle better (bushings is the first). This is why SUVs suck, as we all know. You also lowered the front lower than the rear. What did this do? It shifted some of the weight from the rear of the car to the front wheels. Think about it this way. Youíve helped a friend move a couch havenít you? Well when itís level the weight is evenly distributed between the guy at the front and at the rear. When the guy at one end raises his end (say, going up a step) the weight shifts to the guy on the lower end. Thatís helped your stability. Iím assuming you had the Euro spoiler on the car prior to this new set up. With that alone your carís front end should have been nice and firm. (Iím still scratching my head). When you dropped the front another thing happened. This time to your aerodynamics. Hereís how downforce works on a car. Air flows over and under a car. When air flows under the car faster than it does over it creates a lower pressure under the car and a higher one over the car. The higher pressure then presses down on the car. Drag and downforce are not directly related. Aerodynamics and drag are. See here: http://www.mulsannescorner.com/data.htm
for some awesome fun stuff (also www.mulsanecorner.com
). When you lowered the front you exposed more hood surface area to the air flow. Also your front windshield angle was altered in relationship to wind deflection as well. Under the front the gap was made smaller. The bottom of your car now angles up from the front. This causes less air under the car than there was before and the air now has to accelerate to fill the new space underneath. Youíve created a little venturi under your car. Also remember though that itís pulling air under from the sides as well at this point. Your addition of the Euro spoiler did that on you car to start with. By dipping the front you increased the effect and also slowed the air over the car even more by increasing the frontal area of you car. But, this increased frontal area and more aggressive windshield angle has increased your drag. By how much I really canít tell you. I also canít say if this is the sole cause of the reduced speed and acceleration at higher speeds. How aggressive an alignment you have will also come into play. More toe in means more rolling resistance and such. ďGoing fast requires a TON of power. Air resistance goes nuts with speed, increasing exponentially as the cube of the increase in speed. Air resistance over 120 mph becomes extreme, which is the speed at which a human body free-falling through the air (prior to pulling the ripcord!) reaches terminal velocity and will not fall any faster. If you could go 100 mph on, say, 80 horsepower, to double speed to 200 mph requires 640 horsepower! If you could go 150 mph on, say, 210 horsepower, doubling speed to 300 mph requires 1680 horsepower!Ē (http://www.bobnorwood.com/The%20Fast...0in%20Utah.htm
And going 100mph on the 80hp has to do with your aerodynamics. By increasing your frontal area every extra square inch youíve now exposed is being attacked by the air resistance mentioned above. It takes more of your hoarsepower to overcome that resistance to reach that speed. If you really need that top end speed Iíd say start dropping that back end down bit by bit and see how it feels. But that extra resistance becomes an advantage when you enter into a high speed braking zone! It will help your car decelerate faster from those high speeds.
ďHow it feels.Ē Thatís the most important thing here. I could go on and on with set ups and numbers. Having been a race ďengineerĒ I can tell you two things that are for sure. No two drivers are alike in their abilities and driving styles and even though it works on paper doesnít mean it works in the real world. I canít tell you how many times we did calculations and put a killer set up on a car only to get it to the track and the driver to go like a pig. The sheet would be thrown out the window and weíd go with our gut. Usually the gut was right. A set up on your car that will enable me to drive around a track at X time doesnít mean you can get the same time. Do you like a tail happy car? Or a more balanced? Can you drive through problems, like Senna, or do you need to fix them before you can go fast, like Prost? Both are world champions who drove the same cars with totally different set ups and still were as fast as the other.
I hope your driving skills are up to the challenge ahead of you. And once again, Congradulations! :green: Once you start making adjustments you might find your times going backwards instead of forwards! Donít despair. This sometimes happens and is part of the learning curve. Iíve written a small amount about a very large subject. I recommend the following books by Carroll Smith:
Tune to Win
Engineer to Win
Drive to Win
They cover everything youíll need and were my bibles when I was racing and working as a mechanic.
Looking forward to the "You don't know what your talking about" post that will follow after this... :wink: