The Kimini 2.2 - Design
Home Build Diaries Books, Catalogs, and Websites
A comment about parts suppliers for your car project – think “outside the box.” That is, just because you're building car doesn't mean you have to buy parts from specialty automotive “boutique” parts venders. Some of the lowest priced parts I found were from places like Home Depot, Digikey, McMaster Carr, circle track parts venders, 4x4 off-road shops. Just keep it in the back of your mind when confronted with buying an expensive part, it might be much lower priced if you can find the same thing at a shop that doesn't cater only to roadracers.
The Overall Process
I recently reviewed with a builder the order in which the project should be designed, and I realized that list should be here. I strongly suggest doing these steps in order. I learned some of these the hard way. So, here it is, my suggested sequence of events: (a work in progress....)
Decide what you want it to look like. Make a list of all the “must have” features. Ligher is better for performance.
What are you going to do with it? Race, cruise, autocross? I didn't want to spend years making a trailer queen, so it had to be street legal.
If a street car, how are you going to get it smogged? If you're in California you better look into this NOW.
How many seats will it have? Where do you sit? Left, right, center?
Can you afford it? I found that I had to buy most of the parts up front, *before* design started, because I couldn't find dimensions of the major components. That made it very expensive up front, which was Not what I expected.
Do you have room to build it? How much time to you think it will take. I'll warn you now that setting a goal... better called a deadline, can absolutely ruin the fun of it. It has to be fun to build.
Where is the body coming from? From a kit car, composite, metal? If you want a custom composite shape, where is the mold coming from? Are you making it?
Who's going to design the car? You? Good!
What type of chassis will it have? Tube frame? Composite? Monocoque?
Which means around now you should assemble a design library. Check out the link above, Books and Catalogs. Expect to read, and reread them. This will take a good portion of a year... no kidding. The good news is it's relatively cheap... much cheaper than buying parts at this point.
What engine will it use? Where will the engine mount, front, mid, rear? If you use stock half-shafts, realize the width of the car must be the same as the doner vehicle.
What tires do you want? Tires decide *everything*. If they're much different than the doner drivetrain's, they will affect overall gear ratios. They also decide ground clearance under the pan and CG height. Remember lighter is better.
What suspension uprights? Stock or custom, struts or ? How will they mate to the half-shafts?
What brake rotor and calipers go with these uprights? Are they large enough for the expected performance.
What wheels fit over the uprights and brakes? At this point you need to know what kingpin offset will be acceptable, which will help you decide what offset to get.
Based on the suspension uprights, what type of suspension will be used? Rocker arm? Push or pull rod? Straight axle?
Okay then, time to start sketching the chassis. Remember that safety is THE most important thing. All through design you must constantly ask yourself, “what will this do in an accident?”
Take measurements of all major components, including you. Draw it all out to scale, be it on computer or by hand.
By now you already know the wheelbase, track, suspension type, and uprights which will be used. Using whatever method you want, design the suspension.
Big tip, the suspension designs the chassis, not the other way around. Don't worry about not having the chassis yet, just design the suspension, only making sure the inner links don't go somewhere impossible, like inside the oilpan, or in the middle of your knee. Expect this to take months.
Now knowing the suspension points, draw the chassis.
Build a full size wood mockup. Yes, full size. It's the only way to sort out all the interrelational aspects of the major components, including the body shell. More months.
Still in work.......................
The issue of the lightweight crank pulley
Designing and building a car will truly enlighten you to the word “compromise.” Sometimes it is the realization that you can’t afford titanium wheels, sometimes it is the indecisiveness of where to place the roll-centers. You have to play an endless game of “give and take” in order to get the thing built. If you don’t, you risk getting the dreaded “Design paralysis: The inability to make any decision whatsoever because of numerous conflicting issues.” This can also lead to the belief that, when the car is done, one or more of the following scenarios will occur:
Pushing it out of the garage for the very first time reveals that in your excitement, you neglected to put in brake fluid. This causes your car to coast down the driveway, across the street, and into the neighbor’s yard -- the neighbor who is upset about the loud banging sounds and blinding blue-white light coming from your garage late at night.
Pushing it out of the garage for the very first time reveals that you have the steering rack installed such that a right turn is left. (This can actually happen.)
After getting it all done a friend casually says “You know, for all that work and money, you should’ve just bought a used Viper,” and you agree.
After spending months making the perfect design decisions, people tell you how they would have done it, and you realize their ideas are superior to yours.
After putting it into gear for the very first time and popping the clutch, you realize your custom shift linkage cause Reverse to be where First should be.
After doing all the calculations, including multiplying in your safety factor, the very first pothole you hit causes a wheel to break off.
At the first event you enter, you are squarely beaten by a Honda Civic driven by a kid wearing baggy pants, crew cut, and backward baseball hat.
You take your car to The Big Event. You notice some guy looking at your car, shaking his head, and you realize it’s Carroll Smith. He comes over and casually asks, “Is this yours?” “Um, yes… sir.” He asks, “Why did you build it this way, what were you thinking, and this, this here, it’s all wrong, and that over there is in single shear. Didn’t you read any of my books?”
In spite of all this… I pressed on… besides, the odds of meeting Carroll Smith must be really low…
If I’m doing this only once in my life, it has to be worthwhile. My interest is autocross and time-trials, so the list of requirements went something like this:
Mid-engine, where God intended engines to be.
A two-seater (you have to share things like this.)
Composite skin with a tube frame chassis, for lightweight, ease of assembly and repair.
Independent rising-rate suspension front and rear, rocker-arm in the front.
A well balanced chassis, with as close to 50/50 weight distribution as possible.
A Quaife limited-slip differential.
A12.7 second quarter mile, or better ( a completely arbitrary number, but one I'd be very happy with.)
And to reach that goal, a maximum race weight of 1650lbs including driver.
Radiator air exiting up out through the hood (coincidentally, the only way of make it fit).
Smooth under-tray for some (hopefully) serious down force at speed.
And finally, a real rear fin for track events, not some "ricer" fin with nonexistent down force and drag data.
So I started buying books and reading, and reading, and reading – for a year. Part way into the research phase I came to an expensive realization. The idea was to finance the project as time went on, buying parts as money allowed. But since detailed component data was sparse, how could it be designed? It meant parts had to be purchased before the design even started, causing it to be very expensive up front. But where was I to start? What was the single most important component in the car? The engine - but which one?
The engine search took quite a while, with some of the "drivetrain contestants" being (in 1996):
Toyota supercharged MR-2.
the time I reached my 180-200hp target, some of these contenders
would cost a lot to build up. It seemed like a waste; why not just
start with a larger engine to begin with? I had already had enough of
high-strung little engines with no torque (Datsun 1200). I wanted
something with some grunt, something that right out of the box would
be plenty fast. Something that, as someone said, could provide
"shameless smoky burnouts." On the other hand, weight was a
BIG issue, and it was very frustrating finding absolutely no
information on weights, so I ended up guessing. Yet another
requirement was the availability of a Quaife limited slip
differential. Using "hp/$" to cut down the choices, the VR6
looked good, but it failed the "Quaife requirement" and was
surely too heavy.
So... after much debate, the Honda H22A1 won out. Fairly light (I thought), lots of power, and Honda reliability. Back in 1996, they were hard to find... and when I finally found one, I had trouble with the vendor. (Expensive lesson - get ALL the parts you need up front.) So finally the big box arrived, and boy was it HEAVY - a big disappointment!!! While my Fantasyland weight estimate was 350lbs, reality slapped me with a 475lb lump.
would have chosen the GSR drivetrain today, but if I waited around
for the "perfect" drivetrain, I'd still be waiting. Life is
short and we can't sit around waiting forever, time to get on with
it. In fact lately I’ve been thinking that if I were
doing it all over again I’d use a 180hp Hayabusa sport bike
engine. With a 6-speed sequential gearbox, and a total weight
of 180lbs… nice…
Wheels and tires:
Seemingly a small detail, yet every other part of the car depends on these. The wheel dictates brake size, axle centerline distance above ground, oil pan clearance, and on and on. For the Mini, 13" was the "correct" choice visually and it gave a nice ground clearance under the pan. Another reason for small wheels and tires is weight and rotational inertia, not something to be ignored. The difference between 13” and 18” wheels can be an effective 20hp during acceleration. Think about what you’d pay to get 20hp and you might reconsider buying those huge wheels.
My choice may come back to bite me; applications for 13" tires are drying up, along with manufactures’ interest. Everyone is moving on to 15", if not 16", 17, or 18". Yet a Mini with 18" wheels would make it look like it belongs at a tractor pull competition... no thanks.
This was an interesting component. Everything I read, and everyone I spoke to, said the same thing, do NOT cut corners on shocks. In a car where handling is the primary function, nothing makes more of a difference than good (or bad) shocks. Shocks you buy for your family car cost about $50 each, not so with shocks intended for real sports cars. They are very expensive, ranging from roughly $300 - $1200 EACH!!! That's what it takes to make a car handle well. If it is outside the budget, consider cutting expenses elsewhere else - shocks are that important. So, going solely upon what people wiser than I advised, I purchased Koni double adjustables.
Roll center height:
Choosing roll centers was a (self-imposed) difficult choice. On the one hand most of the books talk about how important it is, but on the other hand some people said it doesn’t really matter. What to believe… If it’s high, the “lever arm” between the RC and CG is small, resulting in little body roll. Seems like a good thing, but it isn’t because it results in high jacking forces in the corners. It also makes tuning the chassis difficult because since the chassis doesn’t roll, how can you adjust something that isn’t changing? OTOH if the RC is low, the car tends to roll more, a bad thing… but a good thing to since the suspension is now easy to tune. Plus, there is little jacking forces. Now you see why people spend months anguishing over such decisions.
One of Carroll Smith’s books shows a diagram of a car sliced like a loaf of bread, with the centroid located in each slice. The centroid points are then connected with a line to form a “centroid axis.” Between that drawing, and reading somewhere that I should keep the centroid axis parallel to the roll center axis, caused me to do just that. Since that time more than one person has questioned that theory. They point out that the chassis is (more or less) a rigid structure - there is no centroid axis, only a single point at the CG through which all cornering forces are applied. A chassis designer also pointed out that it all depends on how the car is used. When I told him it would be used for mostly track events, he said the RC height wouldn’t matter that much; the car is so stiffly sprung that the RC won’t move around much.
The general rule of thumb is to make the RC higher at the end of the car that has a higher CG (like the end with the engine in it.) And conversely setting the RC lower at the end of the car with the lower CG (like at the end with nothing but suspension in it.) The funny thing about this rule is it tends to confirm Carroll Smith’s drawing, yet I also see how his drawing (to me) doesn’t make sense.
I finally chose 1.5” front and 4.5” rear. Did I make the right choices? Guess I’ll be the first to know…
Center of gravity:
I created a spreadsheet program to determine CG from the x and y locations of every component. It ended up being 13” above ground, with 40% front and 60% rear bias (with me in it.) I am however continually trying to move weight forward to get it as balanced as possible (for example placing the battery in the passenger foot well.)
I’ve never driven a mid-engine car before and look forward to it. My brother once got a ride in a Porsche 911 at Laguna Seca raceway. He said that while his modified Mazda RX-3 was faster in a straight line, the braking ability of the Porsche was amazing. I’m sure rear weight bias holds the back of the car down during braking, allowing the rear brakes to do some serious work unlike typical FWD cars.
It was kind of funny how this turned out. I knew most kit cars use a Triumph Spitfire or Dodge Omni steering rack. I learned the Omni rack is for “front steer” cars, while the Triumph rack is for “rear steer” cars, which is what I wanted. “Whatever,” I thought; the chance of finding a Spitfire in a wreaking yard these days in Southern California is about the same as finding a blank sheet of paper at Steven King’s house. So I combed the yards searching for a rack not knowing what I’d find. A nuisance were the steering wheel locks (obviously none of the cars had keys in them.) It meant I couldn’t turn the wheel back and forth to calculate the speed, or pitch, of the rack, that is, until I got a little “medieval.” Another problem is that we’ve all gotten lazy, virtually nothing these days has a manual rack in it, and if it does, it takes about 47 turns lock to lock (okay, not that many, but you get the idea.) So after several days I hadn’t found anything… until I came around a corner and there it was, a 1976 Triumph Spitfire. Well go figure, now I know why everyone uses them. Light weight, fast ratio, $50 from the yard, what’s not to like, so I bought it.
I managed (with some trying) to design the rack in as-is, without having to modify the length at all. The nice thing is if I ever have to replace it I can just buy a stock part and it’s done.
Using the same “weenie-ware” suspension software I used for roll center calculations (which constantly crashed,) I calculated where the steering arms had to be. I know Mr. Bumpsteer personally, having driven my sister’s MG Midget - what were the designers thinking? In a nice constant curve you could hit a bump and, with your hands never moving on the wheel, the car would steer left, then right about three feet. No thanks. So I went to a lot of trouble to try to have none of that - preliminary measurements show none. We’ll see once the steering arms are attached permanently… and I dive into that first corner...
Double A-arm, upper rocker arms, in-board shocks. Nissan 280ZX struts were adapted since they are cheap and larger brake kits are available if needed.
Double A-arm, though they are rotated to miss the drivetrain, essentially acting as lateral and trailing links. There wasn’t much choice besides this layout, other than using struts, but which wouldn’t allow camber compensation. Rear uprights were fabricated from scratch (consuming months.)
Why not use a cheap plain aluminum tank like the kit cars use?
Here’s a story. I saw a video of a guy in a sprint car race where he stopped for some reason and got rear ended. The thing was, the impact was at about 5mph. That was just barely enough to crack the gas tank, located in the rear of this car. The seam split, spilling about 10 gallons of gas under his seat, around his feet, and down onto the headers. He was in a blazing inferno for a long, long, time; it just about made me ill to see. How long can you hold your breath while burning alive? When they finally dragged him out, he was not moving.
Then and there I decided to use the best fuel cell I could find.
Still unresolved. There are many reasons to not use one, as well as many reasons to use one.
Very expensive, about $3500 by the time it’s done. For Honda’s, Peterson has a complete system for the B-series, and is developing an H-series system.
Need room for a large tank full of heavy oil, plus hoses and pump.
Heavy, more stuff to leak or fail.
The best way to lower the engine as much as possible (not an issue in my case since the oil pan has no clearance problem.)
Eliminates the stock oil pump from sucking air during high G-force maneuvers (very likely in my case…)
De-aerates the oil.
Windage losses are minimized by removing oil immediately (translating to 5-10% hp!)
Scavage pumps draw a vacuum in the block, decreasing crank rotational resistance, increasing horsepower.
Dry sump tanks used to be huge because the oils in use at the time had trouble de-aerating. I’ve read that new oils like Red-Line are much better at de-aeration, so tanks can be made smaller.
Or… I can just use an Accusump. I’ve been told by several people that these aren’t a perfect solution. Perhaps, but at around $300 or so, they’re much cheaper. Like I said, I haven’t made up my mind either way.
The H22 tranny has two levers, pushing or pulling one lever selects the gear “column.” That is, it selects gears 1-2, 3-4, or 5-Rev. Pushing or pulling the other lever selects the gear “row.” That is, if the first lever has selected gears 1-2, the second lever selects first gear or second gear.
Several different approaches were considered for the shifter activation. The obvious choice was to simply use the stock shift scheme. Another was to use hydraulic actuation to eliminate mechanical cable play. And finally an ambitious attempt to design a mechanical sequential shifter was considered but shelved due to time concerns. Suspecting the hydraulic solution could be a time sink also, the traditional cable shifter was chosen.
I considered making my own shifter from scratch, but after looking at the stock shifter in the Honda Service Manual I wondered why I was trying to reinvent it. Honda's are known for their excellent shift feel and a used assembly was only $65. I'd spend that much on spherical bearings along, never mind my time - so I bought one. Remember while the engine is now behind me, "forward" is still forward; the shifter must remain in it's original orientation so first gear is where it should be. But that meant he push-pull cables would have to turn 180 deg where they exit the front of the assembly. While the bearing and pivot assembly is excellent, the overall assembly is heavy and over 12" tall! So after staring at it for a long time, I decided to use the shaft, bearings, and actuator in my own housing. The bearing assembly will be turned around so it points to the rear of the car, the shifter cut off above the top cable shaft, then the assembly turned upside-down, and finally the shift lever will be welded back onto the main bearing housing. This solves several problems at once; it saves weight, the shortened shifter decreases the shift distance by about half, and is now half as tall as the stock part. Most importantly, the shift pattern is exactly the same - no bell-cranks or U-turns adding slop in the linkage. The only unknown is the higher shift force, will it be acceptable...
The shifter turned out really, really nice.
I used to race a Datsun 1200 which used VDO gauges. Long story short, I wanted something better, so I chose Autometer gauges this time. Since the Mini can also be driven on the street, a speedometer was needed along with a tach. I didn’t have much room on the dash for both so I was looking for something “just right.”After a long search, I came across just that, Spa Techniques combined tach/speedo. For about $300 you get:
Stepper motor drive for high accuracy and definition
Built-in 3-Stage programmable shift lights
External shift light capability
Low voltage warning
Odometer (total miles traveled)
User configurable trip odometer
Acceleration times (0-60 & SS 1/4 Mile
And the Stack ST700. Even better since it shows more sensor data, but it wasn't out when I ordered my tach (or I didn't see it), but it's much more expensive at about $750.
As delivered from Honda, the header is a 4-2-1 type, exiting the front of the engine, going straight down, with the two intermediate tubes turning rearward below the oil pan, and exiting to the rear of the car. Since there was so much else to do, the exhaust issue sat on the back burner a long time being ignored. Besides, there were certainly reasons to leave it alone; simple, cheap, and “good enough,” is plenty good enough to leave it alone.
But as construction proceeded the exhaust became more of an issue due to several conflicting sub-systems. Because of Honda’s choice of putting the exhaust on the forward side of the block it put the header square in the way of everything. (If Honda had the exhaust at the rear of the block it would have made life much easier.) Everything exiting the center tunnel would face the header heat, and when I was designing the shifter I was finally forced to make a final decision regarding the exhaust. There were three choices of exhaust routing: under the pan and out the back like the stock system, or out the right side, or left side, ahead of the rear tire.
I didn’t care for running the exhaust under the pan because it would only serve to overheat the oil in the pan.
A rant: A manufacturer of a Honda Prelude header recently had the nerve to claim their header flowed so well, that it actually lowered the engine’s oil temperature. That was the biggest load of BS I’ve seen in a long time. Did using their header make the oil temperature lower? Sure, because it ran out the side of the car, and not under the oil pan. But their claim is that isn’t why the oil ran cooler. What? I get so tired of endless marketing bullshit. Apparently lies are “business as usual” for many companies…
Since I almost certainly will modify the pan anyway, the exhaust would be in the way. Running the exhaust out the back, while the quietest solution, would also move weight further toward the rear – the last thing I needed with already 60% on the rear tires. That option gone, I had to chose running it out the left or right side. To driver’s left didn’t work well for several reasons. While I don’t have an air-conditioning compressor, I wanted the space open in case a dry-sump pump was needed, and didn’t want to cook it. The alternator and belt are right there too. And finally, I didn’t want the exhaust making me deaf in my left ear. So I choose the passenger side, exiting ahead of the rear tire because it minimizes routing and heat, keeps the weight forward and to the right (offsetting my weight,) and keeps the entire exhaust system a reasonable length. This choice meant the exhaust runs at right angles to all the tubes, cables, and wires coming out the tunnel from the front of the car, minimizing heat exposure. Of course running the exhaust out the side meant a full custom install. It was an overwhelming temptation to make my own system anyway, and I gave in.
I did a lot of reading and research on header design. Two of the best places are Burns Stainless and Headers By Ed, with both offering very reasonably priced header design services which I took advantage of. The final design was an equal length, 4-1, 32” header with 1.625” primaries and 2.5” collector. Once the header was designed, another reason popped up to not run the exhaust under the pan, the new collector would simply not fit. As far as header material goes, I considered what’s used by everyone else, and how often I plan on making headers - once! I didn’t want it rusting away or cracking, so with the advice of people who know, I choose 321 stainless. I bought the tubing and bends from Reid Washbon (no website) in Newport Beach, CA (949-548-9783). I also found a (comparatively) cheap source for 321 stainless, the aviation industry. Sky Dynamics has the lowest prices I found for 321 stainless tubing; the only drawback is it is only available in ¼” increments for diameter. If their sizes fit your needs, great.
Note: As a very sobering story, I offer up this tale of woe from a builder of a sportbike-powered car who went through hell making his own. He has far more patience than I... who would have thrown them across the yard long before they ever got completed. I fear I may have severely underestimated just how tough the job will be. We'll see... Headers from hell
I chose the SuperTrapp unit. I’m well aware many people don’t care for this muffler, but it certainly solves many problems at once. Weight, tunability, size, stainless construction, plus it’s rebuildable, how do I beat that? If it proves a poor choice, the Walker Dynomax is a very close second, though I don’t know how it would fit.
These were a tough item to spec. I saw lots of nice seats in catalogs, with no way of sitting in them before I bought them. What to do. The only place within driving distance was a Cobra seat dealer. Went there, sat in them, and bought them. I suspect there are better seats out there for the money, but if I can’t sit in them first, then what? Yet another reason why I envy the Brits. They seem to have a disproportionately large sports car industry for the size of the country(!) and have many seat manufacturers. Must be easy to check out seats there, but shipping them here from England is expensive.
I always assumed the frame would be powder coated. The reason is, with a chassis of many tubes, it’s all but impossible to avoid missing at least one side of a tube somewhere while spray painting it. Because of how powder coating is applied, it tends to “go around the backside” of a tube as it’s applied, making it easy to completely cover a tube without having to spray it from all directions. Plus, powder coating is extremely tough and good looking. So why is there any question…
After someone reminded me this is a one-off car, and that it’ll never really be done, I started thinking about paint. Powder coating is very difficult to remove and there’s a good chance I’ll have to work on the chassis. How do I remove powder coat, or do I consider some other type of paint? I don’t want to turn the garage into a paint booth in order to spray. But what if I use some high quality epoxy paint and brush it on? That has several advantages as it’s far cleaner than spraying, it cheaper than powder coat, and it’s easy to touch up. From another point of view, the chassis will for the most part be completely hidden. If there’s a paint run here or there, it will never be seen. I haven’t made up my mind yet…… Regardless of the paint used, I’ll probably prep the chassis by sandblasting.
Why a separate section about this? It’s because some people say they have trouble with braided-stainless fuel lines leaking. One guy claimed they leaked like a sieve when pressurized (the V8 914 builder). Another said if fuel sits in them for just a few days, it starts to dissolve the rubber. He used to run dyno tests on race engines, and if they left race gas in the lines over the weekend, it would be black when he drained them Monday morning (but I’m using pump gas). Several people said I need to use Teflon lines for fuel as nothing else will work.
I have a hard time with this. What do car manufacturers use because they don’t have problems. What type of fuel was used when these problems happened? Will this happen when unleaded automotive fuel is used? I’m bugged because I already bought all the line, Earl’s Autoflex. What’s odd is if “everyone” has trouble with this stuff, how is it that Earl’s markets it as fuel line? And, they don’t even make Teflon hose that’s really intended for fuel… unless you count the stuff for F1 cars. All the “normal” Teflon lines are very small diameter because they’re intended for brake and clutch lines.
Since I already have the stuff (read that as: nothing to loose) I’m going to use it. It should give me several years to figure out if it’s really that bad.
I was told by people who know that I should use structural rivets, not weenie hollow pop rivets from the local hardware store.
Unlike a pop rivet, a structural rivet retains a length of the mandrel when it "pops." The retained stem runs the full length of the
installed rivet, acting as an sheer pin in the assembly and making it extremely strong. Two common strutural rivets are the Cherry Q rivet
and the CherryMax rivet. Anyway, I went on my merry way having had the decision made for me and didn't give it much thought until it came
time to buy them years later.
They're expensive, very expensive when compared to solid rivets. But if your car has rivet holes drilled in the tubes there's no other solution but to use blind fasteners. One possible compromise is to use less rivets and some kick-butt adhesive (which can be expensive in itself.) But at the time I didn't think about that, other then planning to use silicon seal to prevent rattles, leaks, and to keep dirt out from under the tubes. So I drilled many, many holes. It wasn't until years later I added them up... nearly 2500 holes!
It was a pain to find a place that actually stocked the size and type I wanted and they were expensive. My advice is to research the size and type of rivet you want to use before starting your build, to see if you can find them and what it'll cost. The following are places I found that carried (or claimed to carry), Cherry Q, or CherryMax rivets. Be aware that, other then the first two, the pricing is all over the place. I found a span of $0.16 to $1.01 for exactly the same part so do your homework:
Bon Aero Best price for Cherry Q rivets.
Rondure Company Best price for CherryMax rivets, in monel at that!
Aftermarket Lightweight Crank Pulley:
The popular opinion on the street is that aftermarket lightweight crank pulleys cause bearing failure.
So what’s the stock rubber lined pulley for? One theory says it’s to filter out the torque pulsations from individual cylinder’s power strokes. That at certain rpm’s, the crank will resonate (like a bell) and start vibrating, damaging bearings. The rubber in the factory stock inertial dampener mechanically filters out this resonance. The aftermarket part doesn’t have this rubber ring, so can’t filter the pulses. The other theory perpetuated by the aftermarket lightweight crank pulley manufacturers is that the rubber is there only to filter out the instantaneous crank speed variations from traveling through the accessory belts, and the stock pulley filters out an unpleasant noise. They say if the noise doesn’t bother you, there’s 6-10hp to be had by reducing the rotational inertia of the stock unit.
Further muddying the watter is how a car with one if these pulleys installed is treated. People who add these don’t baby their cars, and tend to be high-rpm drivers. That in itself isn’t bad as long as they stay under red line. But I wonder about instantaneous high-g loads, whether drag race starts or high-g cornering causing oil starvation. If true, the bearing damage could incorrectly be attributed to the crank pulley. The real question I have is, do these cars that are driven hard with the stock pulley see the same type of bearing damage? No one will say… The real test would be to find someone who uses a dry-sump oil system and this pulley.
How many of these stories are real; or are 99% of the ones, i.e. “these things wreck engines,” just something that’s “heard from a friend who heard it from a buddy’s uncle” and passed on as fact? There is a huge volume of anecdotal stories about this pulley and it’s hard to tell what’s real. How about the people who say they installed the pulley and never had any trouble (and have inspected their bearings to prove it?) If they don’t have a problem, it starts shooting holes in the entire theory about them being wrong by design.
Here’s what AEM says:
“Vehicle manufacturers have thoroughly investigated the use of torsional vibration dampeners and conclude that their use significantly reduces NVH (noise, vibration and harshness). Furthermore, manufacturer and independent research shows that torsional vibration dampeners are critical to engine life where long-term use is intended. Removing the torsional vibration dampener from an engine can be highly detrimental to its long-term operation!”
The first part seems to agree with the aftermarket manufactures point of them being just for noise control. And the last sentence seems to indicate something in the engine will wear out faster, but what? So how much of this applies to me? I don’t really care about NVH, and what do they mean by “long-term” operation? I don’t expect to drive this much, so where does that leave things… we’ll see. I’m still looking into it, and have submitted questions regarding the pulley to a drivetrain engineer. Why not ask the one person who knows rather than the endless guessing about what’s going on. Here's his reply:
“I talked to an engine builder who builds high performance V8s. He occasionally builds engines without vibration dampers, but only for hill climbing / sprinting. He recommends that the crank is replaced after no more than 4 seasons racing due to the fact that it will eventually fail. The overall milage covered is therefore very low over 4 seasons.
I've been checking out every other possible lead that I have and one of the most interesting is the fact that <mfg name removed> will use the production damper on the new V6 racing engine. The engine is based around a production block and crank and will be used for circuit racing. The milages will be higher than sprinting but not so great. The engineers think that the damper can be improved slightly, (probably reduced mass), but not deleted altogether. This is interesting because with a 6 cylinder engine or multiples of 6 it is possible to achieve perfect primary and secondary balance. The pulses through the crank from each cylinder is what is clearly being damped as you probably already knew by now.
A failure related to the damper will result in a broken crank, possible pressure plate etc rather than bearing damage. I think that any failed bearings etc are as a result of general abuse and not down to the vibration damper.
I think that it is clear that any vehicle that will cover moderate milages should have a vibration damper to prevent the risk of crank failure.”
And on the otherside of the argument is this from Unorthodox Racing's website: Scroll down to FAQ #4-6. Regardless, cranks do flex, so there is an issue... After thinking it over I decided it's not worth the risk and I'm leaving my stock pulley on.
I narrowed it down to several lightweight units. This link is very helpful. The exact unit you need depends on your current requirements.
The Hawker Odyssey or Genesis: Hawker, BatteryMart, or Portable Power.
Varley red top: DMS
Both Yuasa and Varley are carried by racing-stuff.com. They also have several small lightweight batteries intended for electric cars and motorcycles.
Digikey has just about anything electronic related (terminals, shrink sleeving, LEDs, IC, everything!) McMaster has more industrial-related supplies (everything!), which is where I bought my toggle switches, they were cheaper. Wherever you buy toggle switches, pay attention to the DC, not AC current rating, as there's a big difference. It has to do with the arc which happens as the switch is opened under load. AC, which reverses direction 60 times per second, will always go to zero amps within 1/60th of a second, so the arc always goes out. With DC, the arc can persist for a very long time, burning the contacts very quickly. Switches made specifically for DC usually have very fast switching time. If the switch doesn't have a DC rating, don't buy it. What's a bit annoying is that most catalogs don't show the DC rating. The only way around that is to search out the manufacture's Web site and check the real data sheet.
The headlight, wiper, and brake switches are from Painless Performance, and I bought them through CarShop. Painless has most everything for wiring a custom car... not exactly cheap, but they do much of the hard work for you. Take this for what it's worth, I'm an Electrical Engineer, yet I bought their wire harness kit from them. Why? Because I know what a pain it is to collect all the little bits to do it myself. Plus I didn't want to search wrecking yards for an old corroded fuse panel which no doubt wouldn't work or fit anyway.
For the turn signal switch I'm just going to use a toggle switch with a long handle, placed “just so.”