Tuesday, February 28, 2012

Alfa Romeo Giulietta - aka Dodge Dart


Some of you may know that the Dodge is re-releasing the Dart later this year to fill the compact car opening in its vehicle line up.  Though the body will be Dodge its bones will be Fiat; more specifically the Alfa Romeo Giulietta.  Since I am not the die-hard buy American type I am actually pretty excited that Chrysler is using this chassis since the car may retain some of the Alfa’s character.  Even though Alfa Romeos are notoriously unreliable the Top Gear guys still love these cars.  Which means I will definitely take the opportunity to drive one when I get a chance.  I do like the body styling of the new Dart, and I hope its fun to drive.  According to a friend of mine who is a vehicle dynamics engineer with Chrysler said the engineers working on the Dart are trying to preserve the Alfa driving experience.  I hope they do.

I can’t say there are many benefits to living in South East Michigan – like crumbling roads and loose rocks that crack windshields, but I do get to see a lot of the new cars in their razzle-dazzle or flat black paint schemes like this Alfa Romeo Giulietta mule I saw a couple days ago.  I can only speculate what Chrysler’s intentions are with this car; testing for the Dart, Fiat may release the Giulietta in the US, or they may use the platform for a number of other cars.  I heard a newer smaller Jeep model might use this chassis

Alfa Romeo Giulietta test mule painted flat black.

Alfa Romeo Giulietta test mule painted flat black.

Thursday, February 23, 2012

How to Choose Spring Rates

Spring Rates Calculator
Using Suspension Frequency to Help Determine Ideal Spring Rates for your car.

In the right margin of this blog I have posted a spring rate calculator.  It looks like a small excel spreadsheet and it will help you determine what spring rates will work best for your application.  Most consumers who are upgrading their suspension don’t think about spring rates they choose a coilover kit or brand of springs and bolt them on.  They may be basing their decision on opinions or reviews they read online and they may not be getting the best setup for their application.  When I say most consumers, a large majority of consumers are modding their cars for cosmetic reasons and aren’t actually intending to participate in any motor sports.  So for them, the spring rate is inconsequential because they are looking for either a good brand they can brag about or something that is inexpensive.  

If, on the other hand, you are interested in actually participating in some sort of motor sport like AutoX, track days, or racing, then a properly tuned suspension will give you an advantage over your competitors who may have only bought a recommended coilover package.  This isn’t necessarily a bad way to go since there are a lot of good coilover kits out there that are tuned for the car and application.  But understanding spring rates and how they can be used to custom tune your suspension to very specific tracks or your own driving style can give you an edge on the competition.  At the very least it will give you a better understanding of how the suspension works. 

You don’t need coilovers to adjust spring rates, but one advantage of coilovers is that the springs have a standard diameter and you will be able to find a variety of spring rates and lengths online.  Usually the rates will be available in 50lb increments.  This gives you much better suspension tuning options than an aftermarket spring kit that is designed to fit the stock spring locations.  These kits are cheaper since you don’t need to upgrade to coilovers but there won’t be a variety of spring rates available to choose from.

The standard spring rate measurement I will be using is lbs per inch which represents the amount of force in pounds it takes to compress a spring one inch.  For example a 400lb spring will compress one inch when 400lbs of force is applied.  The same spring will compress two inches when 800lbs are applied and four inches when 1600lbs are applied.  To give you some perspective a Ford Focus might have 80-150lb springs, a mildly built Miata might have 300lb springs and a full track car may have 600-2000lb springs.  Obviously the higher the spring rate the harder the ride. Bigger cars will also have stiffer springs since the springs will have to carry the weight of a heavier vehicle.  

It seems obvious to many why stiffer springs would be more desirable, but it may not be obvious to everyone.  A brief explanation is that a stiffer spring maintains to road contact, the car won’t lean as much in a turn, and it won’t bow as much under heavy braking.  The compromise is that the ride quality will be much harsher and that means less comfortable for daily driving. This will be covered in more detail in future articles.

Suspension frequency (SF) describes the natural frequency of the spring in relation to wheel motion and can be used to estimate the appropriate spring rate for various applications.  The calculation isn’t particularly difficult but will require either finding data or taking measurements of the car.  You can also use this to evaluate spring rates of various coilover kits and stock spring packages.  Most passenger cars will have a rate of approximately 1 Hz.  A fairly aggressive suspension setup will be around 2.0 Hz and a track dedicated car will have a frequency of around 3.0 Hz or more.  So you can use this information to figure out where on this spectrum of suspension frequencies will fit your application.  If you drive your car to the track or AutoX event you might want to try a SF a little over 2.0.  It is important to note that you want your rear SF to be slightly higher than your front otherwise the car might start to porpoise; rock forward and backward.  Also keep in mind that you will need to upgrade your dampers (aka shocks) to handle springs that are stiffer if you haven’t done so already, especially if you choose a very aggressive spring rate.   

The spring rate calculator on the right is fairly simple to use.  Figure out what suspension frequency you want, update the vehicle data for your car in the white cells and the ideal spring rate will update in the yellow.  Everything in gray should be left alone and the calculated spring rates will be yellow.  For now none of the cells are protected so you could go in and modify any of them but none of the changes will be permanent.  If you make any mistakes, refresh the page and it will reset the calculator.  The spring rates are calculated for individual corner of the car but since the left and right side should be essentially the same the calculator will only calculate front and rear. If you want some more background information check out the Eibach website.  Please note for a live axle or solid beam axle this calculator will not work.

User Inputs:

Race Weight - This is the weight of the car with fully suited driver, and fuel.  If the car is stock, take the curb weight, add your own weight when fully suited, and a little extra for incidentals.
Weight Distribution Front - percent of the total weight of the car in the front.  You can use stock data to get you close.
Unsprung weight - this is the weight not supported by the springs, so this is the weight of the wheels, tires, hubs, brake caliper, half the control arm, etc.  You can estimate this weight and it will probably be somewhere between 80-100lbs per corner.  Keep in mind that particularly large wheels will be significantly heavier and may push your unsprung weight well over 100lbs per corner.  Since some cars have staggered wheels the unsprung weight from front to rear may be very different.
Spring Angle - if you have a McPherson Strut, you can estimate the angle at 5-10 degrees.  Otherwise you need to determine what angle from vertical the spring/coilover/strut is mounted in the car. 
D1 & D2 - D1 is the distance from the spring mount on the control arm to the control arm pivot point. D2 is the distance from the ball joint to the control arm pivot point.  The units aren't important as long as they are the same (mm, inches, feet, furlongs or whatever). If you have a McPherson strut, then leave these numbers alone since 98/100 is the approximate ratio.  You will see you need to do this for the front and rear.  If you are a Mustang owner and have a live axle, just do it for the front since this is not setup for solid axle setups. 

Everything in gray should be left alone since it is either calculated for you based on the info you entered in the white cells or cell descriptors but I will explain what the various measurements are.

MR - Motion Ratio, this is the ratio of the motion of the wheel to the motion of the spring.  This is calculated by taking D1 and dividing it by D2.  That is why the units of measure aren’t important, since we are using them to calculate a ratio.
ACF (Angle Correction Factor) - This is needed to accurately calculate the how much the spring compresses in relation to the wheel motion.
Front and rear Sprung Weight - In this formula, this is calculated based on the weight distribution and unsprung weight.  In this current configuration, the unsprung weight is considered to be the same for front and rear wheels.  I will update it shortly so that you can put unique values for the front or the rear.
Spring Rates - These are the required spring rates to achieve the desired suspension frequency.  You probably won’t be able to get a 212.3356 # spring, so you will have to decide if you want to with a 200# of 250# spring.  When deciding which way to go, remember that you want the rear SF to be slightly higher than the front, so look at both the front and rear SF before deciding. 

If you have any questions please feel free to leave a comment, and feedback would be appreciated.

Wednesday, February 15, 2012

Review - 2012 Abarth 500 - In the Snow!

Abarth 500 - US Version
Story and Photos by Matthew Eddy


Abarth 500 Logo.

I got to drive the Abarth (pronounced ahh-bart, or ahh-bath depending on who you talk to) 500 for 235 miles over 4 days in both sun and snow.  During that time I had 2 people ask if it was a Porsche, which amused me because this doesn’t look anything like any Porsche that has ever existed.  At least 3 people give me the thumbs up, and one guy told me I am going to get a lot of chicks with this car.  To be honest, I am not sure this would be the most powerful chick magnet, but it is sharp looking; at least from the side.  The face of the car has a very distinct European style that will only appeal to a minority of drivers. 


Abarth 500

Abarth is a factory tuner for Fiat similar to Chrysler’s SRT or Ford’s SVT group and they took a Fiat 500 and made it a bit sportier.  Of course, when I hear “sport car” I want to see some numbers; 160hp, 170 ft/lbs of torque in a car that weights 2535 pounds.  That is a good start, and for once the US market is getting a European car is that is more powerful than its European counterpart which only has 133hp.  It’s easy to see that the car is going to be quick and with its small wheel base, it will be nimble.  Besides the extra horses, Abarth lowered the car 1”, stiffened up the suspension, tweaked the front facia a bit and slapped a bunch of scorpion badges all over.  Actually the car doesn’t say “Fiat” anywhere on it. 

Like most cars these days the Abarth has Electronic Stability Control and Sport mode. Both of which can be turned on and off. When in Sport mode, the throttle response is sharpened up and you can call upon all 160 horses.  The ESC, in my snow driving experience, was probably designed for the Fiat 500 and was easily overpowered by the extra power.    It won’t perform the magic that EVO’s or GTR’s traction control can achieve by helping the driver negotiate a turn that they had over driven.  I was able to get wheel spin in 1st or 2nd when with the ESC on and it didn’t seem to be able to rein it in when I was hard on the throttle.  Also, from a stop, there were times I thought the ESC would stall the car because it bogged down the car so much.  It probably didn’t help that I am used to driving a Subaru and was a bit to aggressive with the throttle from a stop so when I was a little lighter on the throttle and feathered the clutch a bit more the Abarth was able to take off from a stop a lot more gracefully.  Overall the ESC was handy to have in the snow when you are driving sensibly, but it’s not very sophisticated and really only seems to try and control throttle induced wheel spin.  So don’t expect it to save you if you tear into a corner to fast.  Here is a video of me driving in the snow and playing with the ESC: http://youtu.be/IiQXgJRh2pE


Abarth 500 in the Snow at Night.

Abarth Wheel in Snow


In Sport Mode is activated by a button on the center console, and its pretty much just on or off.  When activated the throttle response is very noticeably sharper with the boost kicking in sooner and with more punch.  Perfect for when you are merging on to the freeway or need to pass some Sunday driver sleeping in the left lane.  Otherwise you can gust cruise around in normal mode to help conserve some fuel since that is probably part of the reason you would buy a small car.   

What is nice about the Abarth and the Fiat 500 in general is that if you are the Jolly Green Giant, you will find the car to be quite spacious.  Unless you are closer to seven feet tall you shouldn’t have any problems fitting into this car.  I am an even six feet tall and I had about 6” of head room.  So this car has plenty of room for you, a helmet and even a roll cage if you decide to race it. 

Besides being quick, my favorite feature of the car is the exhaust.  It sounds more like a muscle car than a little four banger with a turbo bolted to it.  I am now convinced that Italians inherently know how to tune an exhaust like no other.  It growls and gurgles like a V8; to bad it isn’t louder!  At freeway speeds it’s drowned out by road and wind noise because it’s just not that loud.  Here is a short video I shot so you can hear the exhaust note for yourself:  http://youtu.be/2Cy4ybqFlZo


Abarth Engine Bay - the turbo can be seen at the bottom of the image, its under and to the left the the silver heat sheild.


On regular roads the car felt pretty good even though the suspension is significantly stiffer than the Fiat 500.  As to be expected with any short wheelbase car on uneven pavement like we have all over the Detroit area, the ride can be pretty bumpy.  If you are shopping for any subcompact car, you won’t be able to avoid this issue  and I didn’t find it to be a problem.  This car would make a fun and comfortable commuter.  


Abarth 500 - Sporty Pedals

Abarth 500 - Seats - nice red detailing.











Performance & Handling

I wouldn’t call the Abarth fast, that label is reserved for cars whose 0-60 times are sub 5 seconds but it is definitely quick.  Though I haven’t see any official figures I am estimating it in the high 6 second range; probably a little slower than the Mini S comparing the power to weight ratios.  At a stop, in first gear, you can very easily get the front wheels spinning.   Actually, for me it was kind of hard to resist not doing it every time but that’s probably because I am like a kid with a new toy when I was driving this car.

The steering effort is firm and communicative.  As expected the car will tend to understeer, but that is to be expected from a FWD and manufactures will tune that into the car since its considered safer.  I don’t think it will take much to get it to be a bit more oversteery; different alignment and a larger rear sway bar should do the trick.  A few practice slaloms I tried the car felt very responsive with slight understeer developing toward the end.  Under hard corning the car was well balanced front to back but I was worried that the narrow track of the car and its height may make it prone to tipping.  I did see a picture of a 500 on two wheels through a corner and I think that made me a bit overly paranoid.  Plus I know I would never hear the end of it if I rolled the car, so I was aggressive, but didn’t push it to the limit under hard cornering. 

Overall the driving experience was very enjoyable and is a fun car to drive.  The performance of the car is such that I think you could surprise a few people with how quick it is.  I know I surprised a friend of mine when I spun the wheels launching it from a stop. 

Though is possible to nit pick any car, especially at this price point, the car has, only one major flaw; seating position.  My first thought when I got into the car was that I felt like I was getting into a van with captains chairs.  It even has a fold down arm rest!  This is great for commuting, but I was expecting a sports car.  I want to feel like I am getting into the cockpit of a F-16.  It felt so tall that I was at eye level with other drivers in full sized cars.  Some people might like this since the car, from the driver’s seat, doesn’t feel small.  However, I was just imagining this car just tipping over under hard cornering.  So much so that I would lean well over the passenger seat if I was really ripping through a corner.  Also, with this very vertical seating position I found my left leg was getting a cramp in my shin.  Basically, it was comfortable, but it didn’t feel sports car like and I had a hard time imagining myself taking this to a track. 

Abarth 500 - Steering Wheel and Dash Detail.



Abarth 500 Interior.



My only other complaint is the transmission wasn’t very smooth.  Sometimes I had to find 5th, and I got a crunch from the transmission when I was putting the car into reverse.  It wasn’t horrible, but a smoother tranny would improve the driving experience. 

I should also note that the back seats are really only usable for children.  There isn’t enough leg room or headroom for adults to sit back there comfortably.  If you are buying a subcompact then you probably already know that the backseats are decorative, or at the very least a convenient padded shelf to place luggage and weren’t actually expecting to seat people back there except in emergencies.  The trunk, on the other hand, is actually larger than you would expect.  You can probably hold at least one body if packed properly.

Looking at the car in a vacuum (not comparing it to any other cars), it is fun, quick, agile, looks good, and the exhaust sounds great.  This would make a great commuter and at around $22,700, the price it’s a fair amount less than other available turbocharged cars.   The problem is that the Abarth isn’t the only car in its class and it’s direct competition is the Mini Cooper S and some might also say the Mazda MX-5 Miata.  Originally I though I should compare it to a Ford Fiesta, Mazda2, Honda Fit and a few others but really none of them have a comparable model that comes close to the power of the Abarth.  So those cars aside, how does it compare to the Miata and the Mini? 

First off it beats them both in price.  The base MX-5 starts at about $23,500, and the Cooper S is at least $24,000, but you are probably looking at closer to $27,000 when comparably equipped for either car. In terms of fuel economy, the Abarth and the Cooper S are fairly similar.  I haven’t seen any official figures for the Abarth, but I am estimating that it will be approximately 30mpg on the highway compared to the Mini’s 32. Personally I got an average of 26mpg over 235 miles of combined city/highway driving but I was driving the least economical way possible so that doesn’t really is a fair assessment.  Where the Mini edges out the Abarth is the feel; the Mini feels sportier, the seating position is better and it has 181hp giving it a better power to weight ratio.   

If I had the money, I would buy a Mini over the Abarth especially if you plan to do some autoX or track days.  If you are serious about getting into motorsports than the MX5 would be the best choice since its rear wheel drive and has 167hp from a naturally aspirated engine.  But, if you like the looks of the Abarth and want a car that is kind of unique then take one for a test drive.  They are fun, sporty, comfortable, and would make a fun daily driver.