If you’ve read my posting for a while you’ll recall my trips to the great state of Kentucky and my trips to the place the worlds most recognizable car is assembled.
Yes I’ve taken the Corvette assembly plant tour more times than anyone I know, hell when I retired I’m going to volunteer to work the tour route in the plant. I love Bowling Green!!!!
The last time I visited they were building out the plant for the Chevy Volt and working on the new section for the C7 Corvette. These upgrades mean more work for the plant and those doing “God’s work” (LOL).
Well there is more. Corvette has had a program where the an soon to be owner of a new Corvette can pay to build the engine for his car in the Performance Build Center (http://corvetteblock.com/2011/11/performance-build-center-open-house/). That may be the coolest idea I’ve heard. Well this program is being moved from Michigan to the Bowling Green assembly plant.
I think that is great news!!!! You an build your engine, watch it installed in your car and drive it out of the factor!!!!!
Perhaps is was my imagination but there seemed to be a lot of guys dressed like the late Carroll Shelby (dark clothes, dark wide brimmed hat). What wasn’t my imagination was all the Shelby Mustangs up for sale, there were a lot. Normally, there are quite a few but there were more than usual.
I grabbed a lot of shots and I thought I’d share them.
1967 Shelby Mustang:
Here is a quick vid of them bringing a Shelby GT 350 in from auction. I had hoped they would fire it up but they were waiting for few cars in front of them to park.
Few post back I mentioned the issues with being able to shift the C6 into reverse and then generally the shift began to get worse. Additionally the clutch fluid would become low.
As most Corvette owners know, the C6 has a separate hydraulic clutch. I had the fluid flushed numerous times and eventually we found a small leak at the clutch slave cylinder.
Replaced the cylinder and stopped the leak. This stopped the fluid usage and shifting improved, but only slightly.
Eventually it began getting much worse. With the ignition on the car would not go into reverse at all. The only way to get it into reverse was to turn the car off, put the that trans in reverse and start the car. Even then, it would sometimes kick itself out of gear when started Then highway shifting began slipping and RPM when up.
I do auto cross the car and I guess some spirited street driving. Here is what my clutch and flywheel now look like, yes… I saved them!!!
Clutch1
Clutch 2
Those shiny rivets – not a good thing!!!!
The Flywheel, interesting coloration, don’t you think?
Meanwhile, manual-shift enthusiasts are upgrading to modern units packing more heavy-duty horsepower capacity—and more gear ratios.
“The generation that is now in their 60s can afford to build the cars that they wanted to build when they were in high school,” said Dick Hill, sales manager for Centerforce Clutches in Prescott, Arizona. And while those folks are not usually looking to build a race car, “they do want a four- or five-speed manual transmission,” he said.
More surprisingly, the trend extends beyond muscle cars and into traditional hot rods as well.
“I have friends who are building Deuce roadsters and they are putting LS motors in them, with a five- or six-speed manual transmission,” Hill said. “There are people who put Cadillac V-8s in 1949–1951 Mercs, and they want a stick. They want a three-pedal car. So that, too, is contributing to the growth of the high-performance clutch market.”
Hot rodders who already own or have owned multiple cars are now looking for something different.
“It’s like the people who buy their first Harley, they want it with every doo-dad they can get, where older bikers are turning back to the Knucklehead or even Flathead motors,” Hill said. “It’s the same with the hot rodder who already has two or three or four toys in the garage. The newest toy is going to be a stick car. And it’s for the same reason that someone will buy a brand-new Camaro, put 1,000 horsepower in it, and drive it on the street while blowing cold air and playing tunes. They want a manual not because they’re going to race it, but because they can have it. That’s what we hear all the time: ‘Because I can.’”
Rating the Ratios
American Powertrain of Cookeville, Tennessee, sells a broad range of high-performance drivetrain components, from complete crate engines to driveshafts and pedals. The company also distributes Tremec transmissions.
“The hot market right now is for the Magnum six-speed in a classic muscle car,” said Gray Frederick. “The Magnum is Tremec’s replacement for the T-56 is the aftermarket version of what you would get in a new Shelby GT500 or Camaro SS.” Frederick added that people are putting them into classic Mustangs Cougars, Camaros Firebirds, Barracudas and Challengers.
“The cars that people spend the most money on are the cars that [are] getting Magnum six-speeds,” Frederick added.
The Magnum is available with two sets of ratios, with the closer-ratio unit being the more popular of the two.
“The wide-ratio box has a 0.5 overdrive, which is very tall; a lot of engines can’t pull that much overdrive,” Frederick said.
But when it comes to overdrive, isn’t more better?
“That’s a myth,” Frederick said. “You can say, ‘Alright, I’m at the ragged edge of my cam, where if I’m on flat ground I can hold 70 mph all day.’ In a perfect world, that would be great. [I]n the real world, at some point you’re going to have to slow down for construction, and then speed up again; or you’re going to hit a rise, or something else that causes your engine to run out of breath. [T]hen you’re going to have to shift and that’s what you’re trying to avoid.
“You want to put it in sixth gear and leave it sixth gear,” he continued. “You don’t want to run down the highway at your cam’s peak performance, which would be 3,000–4,000 rpm. But you do want an rpm where your engine can pull your car up hills, and pass without dropping a gear. If every time you put your foot in the gas the engine lugs and you have to shift, that becomes very inefficient. We’re helping the customer understand that, even on the highway, you want to stay in your powerband. Otherwise the overdrive doesn’t do you any good.”
Frederick recommends the wide-ratio unit mostly for torquey big blocks.
“A Pontiac 455 will pull a stump out of the ground at 800 rpm; it doesn’t have trouble pulling a car at whatever rpm you’re running,” he said. “A Mopar 440 and some other big blocks with a lot of low-end grunt can usually handle the taller overdrive, too. And of course we’re dealing with a lot of electronically fuel-injected (EFI) engines now, and most of them have computers that can cope with low rpm very well.
They can retard the spark, they can meter the fuel differently, they can do all kinds of things.
“We help the customer choose a rearend ratio and a gear set that’s going to give them the best performance, from top to bottom,” Frederick said.
Pedal Pressure Another concern, according to Hill of Centerforce Clutches, is the physical effort once associated with a high-performance clutch.
“Our customers all ask, ‘How stiff is the pedal?’” he said. “That’s why we’ve been very successful, whether it’s a single-disc clutch for mild upgrade vehicle, or dual-disc unit that can hold 1,300 lbs./ft. of torque, we’ve been very successful in making them streetable.”
The average consumer, Hill said, could climb into a car with a Centerforce dual-disc clutch, push the pedal to the floor, and not realize that the car was modified.
“[T]he person who has a $75,000 Camaro or Corvette wants race-car performance without the race-car effort, so this is pretty significant,” he said.
Still, selecting the optimal clutch for any particular application is a complex task best left to experts.
“There are different linings and different friction materials on the pressure plate,” Hill said. “Heat is a factor. The first thing you have to know is how the vehicle is going to be used. Drag racers realize they are going to drive their car until they break it, where hot rodders don’t beat their cars up as bad. They are very proud of their cars and they want to drive them, not break them. And unless the car has been tubbed, a street machine generally runs smaller tires, so you want to tune the clutch for that.”
McLeod Racing of Placentia, California, offers its RST and RXT Street Twin clutches, both double-disc units that hold up to 1,000 horsepower, with the pedal pressure of a stock clutch, said President Paul Lee. Contributing to this low effort—and to easier installation—are McLeod’s hydraulic release bearings, “which fit most applications, replacing worn and/or outdated mechanical linkages,” he said.
“We’re selling more clutches for vehicles from the 1960s and 1970s, and installing a new hydraulic clutch in one of these cars can significantly reduce pedal effort,” said Rich Barsamian, national sales manager for Advanced Clutch Technology (ACT) in Lancaster, California. The company also offers a wide range of clutches for GM, Ford and Mopar applications, each rated for torque at the crankshaft.
When installing an aftermarket clutch, Barsamian suggested, “be sure to use the right amount of lube on the input shaft—it is possible to use too much. Be sure parts are free from dirt and oil, and washed in a non-petroleum-based cleaner such as acetone, alcohol or brake cleaner. Be sure to follow the correct torque and tightening sequence when installing the clutch cover—and do not use impact tools.”
If you are going to race you need to be safe. Now, I don’t have a roll cage in my cars and I do race them from time to time (on a track or SCCA – not on the street.) but I’m not going to be putting down numbers where you really need one. But still building one is always a “safe” bet. This build is for a C5 Corvette but the principles are the same for any car, even my Mustang.
Most race cars are required to have one. Most street cars don’t. Get on your lid and you’ll wish you had one. It both keeps you safe and keeps your car stiff.
We’re of course talking about roll cages, and in this featured tech piece we’re going to take a look at the in’s and out’s of the basic roll cage, from the materials they’re constructed of, to where you can have one installed, what it will cost you, and what NHRA regulations you need to know before you chop up your prized vehicle and start bending and welding.
To really get a good understanding of the business of roll cages, who better to sit down and chat with than some of the veterans in the industry who make their living building race carchassis and chassis components? Below, you’ll hear from the likes of Chris Alston’s Chassisworks, Wild Rides Race Cars, Alston Race Cars, and Ridetech (for the street and muscle car inclined) as they share their knowledge and experiences in this pseudo beginner’s guide to roll cages.
At the surface, a roll bar and a roll cage are designed to accomplish one very critical goal — to keep the driver safe should they be involved in an accident; particularly a crash that involves the shiny side down. But as chassis builders found early on, there’s more function to that puzzle of bars than just safety, which we’ll get into later. As most of our readers know, a roll bar and a roll cage are not the same thing. Same purpose, different execution.
Shown here is a visual difference between your basic 4-point roll cage and an 8-point roll cage from the Chris Alston’s Chassisworks catalog. The bars shown in blue are optional.
The basic, 4-point roll bar consists of a main hoop behind the driver, two rear struts, and an optional cross brace on the main hoop should you need it or the rules require it. From there, you can go with a 6-point roll bar that includes a driver and passenger side door bar, while an 8-point setup includes a pair of rear-facing side bars for extra support of the main hoop.
Moving on to roll cages, you first get into the 8-point roll cage, which includes a main hoop, cage sides that route along the A-pillar, a windshield brace across the forward section of the roof, a back brace bar, roll cage gussets, and subframe struts. A 10-point cage includes rear struts and commonly an X-bar through those rear struts for torsional support.
Once you go beyond the basics, you start getting into 12-point and 14-point cages and on into full tube chassis cars with Funny Car cages that fall under the SFI 25.X certifications. Today, however, we’re going to focus on your first roll cage — the basics.
NHRA Regulations You Should Know
So even though the rules say you don’t have to run it, we really suggest you put at least an 8-point in any car that’s going to be raced. – Jim Wright
The National Hot Rod Association, the premier governing body in the sport of drag racing, outlines a number of requirements for roll bars and roll cages for racers competing at sanctioned tracks and events the world over, based on elapsed time and, in some cases, on speed.
Vehicles running 11.00 to 11.49 in the 1/4-mile or 7.00 to 7.35 in the 1/8-mile (including those with T-tops), convertibles running 11.00 to 13.49 (7.00 to 8.25), and dune-buggy-type vehicles running 12.00 and slower are required to have a roll bar installed in the vehicle.
Stepping up the performance ladder, a roll cage is mandatory for any vehicle running 10.99 (6.99) or quicker or exceeding 135 mph. In any full-bodied vehicle however that maintains an unaltered firewall, floor, and body running between 10.00 and 10.99 (6.40 and 6.99) a roll bar is permitted in place of a roll cage.
In these two photos, you can see the comparison between a frame and unibody car. On the left is a unibody car with the NHRA mandated 6 x 6 x .125
Despite the regulations, nothing says you can’t overdo your setup and run a full 12- or 14-point cage on a 12-second car. Fact is, you can never be too safe. “Our philosophy has always been that in the case of a rollover, the roll cage that protects the top of the windshield is much stronger and provides a lot more protection,” explains Jim Wright of Chris Alston’s Chassisworks. “So even though the rules say you don’t have to run it, we really suggest you put at least an 8-point in any car that’s going to be raced.”
If you’re working with a car with an OEM frame, the roll bar/cage must be attached to the frame, while in unibody cars (which make up most late model cars), a 6-inch square steel plate measuring 1/8-inch thick must be welded to the floor as a base for each bar that makes its point of contact inside the car. Bolted-in bars require a pair of 6-inch steel plates — one underneath and one above, with four 3/8-inch bolts through the rocker sill to hold the two plates together.
Digging into materials, all tubing has to measure 1-3/4-inch outer diameter, with mild steel .118-inch thickness and chromoly .083-inch. Swing-out side bars, popular for many cars that will be driven on the street and climbed in and out of, are permitted on cars running 8.50 and slower, with a number of caveats in terms of the clevis, bolts/pins, and more.
The NHRA, in conjunction with the SFI Foundation, has put in place mandates for welding processes that must be used on both mild steel and chromoly. As well, plating and grinding of the welds is expressly prohibited.
All roll bars/cages constructed of 4130 chromoly tubing must be welded using an approve TIG heliarc process, while mild steel must be done with an approved MIG wire feed or TIG heliarc process. Grinding and plating of the welds is prohibited, so keep these points in mind if you’re a do-it-yourselfer.
The 2012 NHRA Rulebook has 12 pages in the General Regulations section that pertain to frame requirements, which is far more than we could ever outline here in detail. If you’re considering building a roll bar/cage yourself, we’d suggest if you’re not already an NHRA member, to either get yourself signed up or pick up a copy of the NHRA Rulebook, which is available for $10 from the NHRA Store online.
Moly Versus Mild
Your choice of material for a roll bar/cage comes down to one of two options: mild steel or chromoly. Each one, when built within the specifications of the NHRA rulebook, offers the same amount of strength and protection. What it really boils down to then is a tradeoff between cost and speed. How fast do you want to go?
The Weight Debate
By nature and pound for pound, chromoly is a stronger material than mild steel, and that allows for chromoly to be a thinner wall tubing (.083″ compared to .113″). This gives chromoly a distinct advantage in terms of weight, but that advantage comes at a cost that customers must weigh (no pun intended) before they build.
Mild steel is far less expensive than chromoly, but comes with the disadvantage of more weight. For the grass roots racer on a budget that we’re targeting here, that cost versus weight decision can be a big one.
“The only reason to use chromoly is if you’re building something that the class requires it or if weight is a real big factor, because it will be lighter,” explains Wright. “Technically they’re the same strength, and chromoly is an upgraded material that will certainly save you some weight, but 99-percent of people buy the mild steel because of the price.”
For comparisons sake, using a 12-point roll cage from Chassisworks as an example, the mild steel version will tip the scales about 50-60 pounds heavier than the chromoly, according to Wright, but is nearly double the price.
As pointed out above in the NHRA regulations, the minimum wall thickness on mild steel is more than that of chromoly to achieve the same result, and that is because, by nature, chromoly offers more strength pound-for-pound, so to speak.
“Some people say ‘well chromoly is stronger’, and it is stronger on its own, if you took equal tubing of the same wall thickness and tested them side-by-side, but they’re allowing you to run a thinner wall thickness with chromoly to save some weight and still equal the same structure, strength-wise,” explains Gene Giroud of Wild Rides Race Cars.
Two Birds With One Stone
The primary means of a roll bar or cage is to protect the driver, but barring such an incident, those bars will serve a daily purpose of stiffening the entire vehicle up and creating less body roll and twist. Each bar added to a roll cage adds another dimension of structural support and rigidity. For example, the X-brace shown here is not only stronger than the straight rear struts, but also provides added torsional strength to the car. The downside, however, is that the X-bar essentially eliminates your back seat.
The benefit of a roll cage is really two-fold. It’s designed to protect you first and foremost, but the every day bonus to the existence of a roll cage is improved stiffness of the vehicle, and that’s a big plus for drag racers planting the tires to the ground.
“On the surface, the primary purpose of a roll cage is crash protection, but in reality, you only use the cage in that context one time,” explains Bret Voelkel of RideTech. “But every time you start the car and drive it, the roll cage offers a lot of structural and torsional strength, and that gets applied every time you use the car.”
On the surface, the primary purpose of a roll cage is crash protection, but in reality, you only use the cage in that context one time. – Bret Voelkel
Adding more bars to a roll bar/cage not only adds to the structural integrity from a safety standpoint, but each additional bars presents more rigidity to the chassis.
“The more points you put in the car, the stiffer the platform of the car is going to be. And if you put an “X” in it for example, that’s going to make it even stronger,” says Mike Ruth of Alston Race Cars. “And the more horsepower and torque you have, and the better ‘bite’ the car gets, the more it’s going to try twisting on the launch, so more bars you add the more rigid the chassis will be.” By maintaining that stiffness within the body and chassis, the shock and suspension tuning adjustments that you make will deliver results you can truly see.
Buying A Cage For The Street Versus The Strip
Something to keep in mind when you’re in the market for a roll cage is the fact that what’s designed to save your life in a dedicated race car isn’t necessarily optimum for a car that spends all or most of its life on the street. Most chassis builder, including those we spoke with in this article, generally build their roll bars/cages to NHRA specifications regardless, but these chassis builder also know there are safety discrepancies between a street and a race car.
What’s designed to keep you safe on the track can be your worst enemy on the street. Imagine getting broadsided and striking the cage seen here without a helmet on. For this reason, many chassis builders will shy a customer away from a full roll cage if the primary use of the vehicle is street driving.
Said Giroud, “The roll cage that’s designed to save your life on the track is meant for an environment where you’re using proper safety gear — a helmet, harnesses, and everything else. You don’t want to put a person in unsafe situation by putting too many bars in it, because it presents what I would consider a more unsafe situation than too few bars on a race car. You don’t want to put a bar by the drivers head and then they get broadsided and hit their head on that bar and not have a helmet on. What’s there to save your life at the track can be your worst enemy on the street.” There’s no specific rule of thumb for track versus street split time, but if you’re doing a considerable amount of street driving, a roll bar might be your best, and safest, bet.
This Ain’t The Zoo’s Tiger Cage
Though not currently NHRA legal, RideTech offers a bolt-in, stainless steel roll cage known as the Tiger Cage that’s easy to install and form-fits a number of specific and popular early and late model muscle cars. Shown here is the complete Tiger Cage system, with a seat brace bar and door bars.
For the muscle car crowd amongst us or for those looking for affordable and easy-to-install alternatives to the weld-in roll cage, the folks at RideTech offer their Tiger Cage stainless steel roll cage system. These bolt-in cages are pre-engineered and designed for specific makes and models, with patented clamp collar components that tie the cage to the structure of the car for safety and rigidity. And the best part is, you can install these at home in 4-6 hours using just three simple tools found in any basic toolbox. “The Tiger Cage is basically a modular, bolt-in, stainless roll cage system for muscle cars,” says Voelkel.
Here, you can see the clamping system used to hold the Tiger Cage together. Although geared toward the muscle car and street crowd, this kit is in fact NHRA-legal for cars running 10.99 and slower.
“We used stainless for a number of reasons,” continued Voelkel. “Beyond the aesthetic benefits of it, you don’t have to paint it or worry about scratching the paint. The stainless that we used actually has a higher tensile strength than mild steel and approaches that of chromoly.”
The Tiger Cage is sold in modules, beginning with a base 4-point roll bar containing a main hoop and two rear struts that will allow you to retain the back seat. Additions that include a door bar that are situated down low on the door can also be added for more structural support. Tiger Cage’s are currently available for 2005 and later Mustangs, ’67-69, ’70-73, and ’74-81 Camaros, as well as ’64-67 and ’68-72 GM A-Bodies and ’68-74 Novas.
How Do You Find A Good, Quality Chassis Shop?
The world wide web and magazines are your friend. Publications like National Dragster feature extensive ads for chassis builders and chassis manufacturers, and the use of web search engines like Google and Bing will turn up plenty of builders in your area.
But chances are you don’t buy many things without trying them out first, or at the very least, finding out everything you can about the product beforehand. And the same applies to a roll bar/cage. So, if you really want to find a good, quality chassis man in your area, the best thing you can do is to visit the local track, take a look at some of the cars, and ask questions.
Here, you can see a number of different roll cages installed in a variety of cars out of the Alston Race Cars shop. In addition to complete in-house chassis service, Alston also sells complete roll cage kits that are ready to notch and weld.
“Without a doubt, going to the track and talking to people and asking who did their chassis or cage is the best way to go about it,” says Giroud. “If you see something you like, you can ask who did it, and how their experience was. Word of mouth is the best way.” After you’ve talked to the racers and asked the questions you’d like to ask, a visit to the chassis shop will often give you tell-tale signs of the service you’ll get.
“I always tell customers to come to our shop, and then visit some others, and make a mental note of the cars that are in their shops, and then go back three weeks later and see how much work has been done to those cars. If they’re covered in dust and in the same condition as the last time, chances are your car is going to sit a while,” says Ruth.
Manufacturers like Chassisworks, which make and sell components but don’t construct/install them, do have networks of chassis shops that use their products around the country, and in the example of Chassisworks, Wright relayed to us that they can generally find a customer a shop within 100 miles of their location. But again, the rule applies that asking questions at the track is always best case. With decreased racing budgets and an influx of tools commonly used by chassis shops more readily available these days, many racers today are taking on the project themselves in their own garages in increasing numbers.
With easy and affordable access to tools used by chassis builders these days, more and more people are going the DIY route for installation of their roll cages. Alston Race Cars’ Mike Ruth cited a $49 tubing notcher available at Harbor Freight as a prime example of a tool plenty capable of doing the job at home.
According to Ruth, the DIY route has become more popular for entry-level customers looking for a roll bar/cage. “Our pre-bent roll cages come with great instructions, and it’s really not that difficult to install a roll cage,” says Ruth. “The average guy that’s out there hot rodding has used carpenter tools and knows what a level and all that is. You can buy a very inexpensive tubing notcher that hooks to a drill press and after a few cuts, you could make a cut as good as anybody.”
What Should You Pay?
The cost to have a roll bar/cage varies widely from region to region, and a lot depends on which shop you have it done at. A one-man band that does chassis work in his sop on the side may be much cheaper than a full-time shop with dedicated welders and fabricators, with overhead costs and insurance. But don’t be fooled by presentation, as there are countless part-time chassis guys out there that do exceptional craftsmanship.
As Wild Rides Race Cars’ Gene Giroud stated, I always tell people to keep in mind they’re not buying tires here, so don’t go price shopping.” The craftsmanship and level of service you’ll recieve will always play a pivotal role in how much you’ll pay for a roll cage, and as always, keep in mind that you do in fact get what you pay for. Seen here is a roll bar with a swing-out drivers door bar in a ’55 Chevy out of the Alston Race Cars shop.
Like anything else, you get what you pay for in a roll bar/cage. Go to the track, check out the quality of the work you see, and compare prices amongst those shops. The ones that charge more may not always deliver the better product, and vice versa, the cheap shops aren’t necessarily rolling shoddy jobs out, either.
“I always tell people to keep in mind they’re not buying tires here, so don’t go price shopping,” says Giroud. “You don’t get the same product from everyone.”
Whether you’re on the hunt for a quality chassis shop to install your roll cage or you’re diving into the project yourself, the best thing you can do for yourself is take the time to do your homework. Consider how you’ll use the vehicle, both now and several years down the road. Weigh the cost versus weight debate, and decide what meets your needs. Again, the primary goal here should be keeping you safe regardless of your driving habits, and remember, you can never be too safe.
OK, if there has one thing that being a forum surfer has taught me over my brief tenure of being such, is there are a lot of things that affect, generate, hinder and enhance engine performance that are not understood or simply just ignored.
Most of this stuff is simply just not shared, be it that they are considered speed secrets or the lay person simply does not understand it, whatever.
I wanted to start a thread to discuss some factors that affect engine performance and the parameters that performance engines live within. Read, argue, whine or cry, this is the truth. And as Jack Nicholson said in "A Few Good Men"- "you can't handle the truth". Well, maybe you can, let's find out.
Get your calculators ready, over the next few weeks, you will need them.
Now, with all of that out of the way, let's start by nailing down the first thing we need to consider when wanting to build a new engine and get the maximum performance out of it. Knowing what we want to use it for will deliver the best possible results. Building a high strung engine to take the family to picnics on Sundays will probably not deliver the experience you are after. Well, maybe the experience you are after, but probably not everyone else in the car.
The best place to build a starting point is to determine intended purpose of our engine and then correlate this to a range of piston speeds.
Piston speed will have a crazy-huge effect on how the engine performs.
I am going to break this down into different categories. For those of you playing along at home, I will give you several examples to experiment with, I am not going to lead you down a primrose path to a result that I have predetermined. Your rules, build what you want without spending a dime.
OK, the categories are:
Street engines (stock)
Mild performance or street/strip
Endurance/NASCAR/Road Race
Maximum effort (Mileage limited/drag race)
AYFKM effort (Component failure limited)
Now, the classification for each of these categories are split by how fast we fling the piston. But first, I guess we need to know how to determine piston speed so we can then determine which category we belong in, or vice versa.
The formula for Mean Piston Speed (MPS) is MPS in ft per minute=(inches of crankshaft stroke x (engine RPM/6))
Depending on the stroke of the crankshaft, and the RPM you expect to see, we can categorize our engine. This will affect our pocketbook, because it will directly affect the type and quality of parts we need to buy to support our performance objectives.
Now let's put these categories in a manner where piston speed can help us determine what we are building. Or, what we need to build to fit into a certain performance category.
Street engines (stock) 2000 to 3000 ft/min
Mild performance or street/strip 3000 to 4000 ft/min
Endurance/NASCAR/Road Race 4000 to 5000 ft/min
Maximum effort (Mileage limited/pro class drag race) 5000 to 6000 ft/min
AYFKM effort (Component failure limited) 6000 to 7500+ ft/min
OK, so if you tried a few different combinations, you probably realize we can change the category by solely changing the stroke, changing our RPM, or both. So great, wow, what a speed secret. Thanks a whole pantload Parker, I read through all of this for that? You're an asshole. Yeah, I know I am, thanks. But the thing that we need to understand about the formula is you need to understand engine speed (RPM) is power. Let's take a look at two theoretical engines and another formula, this one you have probably seen.
Horsepower = (Torque x RPM)/5252
By solely changing RPM, I can make one of these engines a grocery getter and the other, an F1 contender.
Two little six cylinders; both make an eyeball popping 246 pound feet of torque :lol
In the first one, my maximum usable RPM is 4500, and when plugged into the above formula (go ahead and do it, doofus), we see the engine is capable of making about 210 horsepower. :facepalm:
Now we will leave everything the same as far as torque, but let's give the engine an F1 race car caliber RPM of 19,250. After you do the math (I don't have to call you doofus this time, do I?) we see that though my torque stayed 246 lb/ft, my horsepower climbed to a panty-dropping 910! :willy
RPM is power folks, RPM is the shit. RPM can also stand for "Ruins People's Motors" if you don't know how to handle your newfound knowledge.
Piston action has a dramatic effect in the way air and fuel enter, and exhaust leaves the engine. Going back to our categories, we are going to relate the effectiveness of this piston action with our engine and piston speed categories. We do this using something called Volumetric Efficiency, or VE. VE simply put is; if I have a 100 cubic inch engine, and that engine can breathe in and expel 100 cubic inches of air for every camshaft (two crankshaft) revolution(s), it is 100 percent volumetric efficient. If the design of the heads, intake and exhaust only allow 85 cubic inches of airflow through the engine, it is 85% volumetric efficient. If it can move 110 cubic inches of air flow, then it is 110% volumetric efficient. Are engines over 100% VE possible? Why yes, yes they are, and I am going to show you how to build one. Wow, a 350 cubic inch engine that can move 385 cubic inches worth of airflow? Oh yes, yes indeed.
But that will wait until the next installment, for now, let this digest.
Street engines (stock) 2000 to 3000 ft/min 80-90% VE
Mild performance or street/strip 3000 to 4000 ft/min 90-110% VE
Endurance/NASCAR/Road Race 4000 to 5000 ft/min 110-120% VE
Maximum effort (Mileage limited/pro class drag race) 5000 to 6000 ft/min 120 to 127% VE
AYFKM effort (Component failure limited) 6000 to 7500+ ft/min 125 to 128% VE
So we have learned that how fast the piston moves has a great affect on the performance I can expect. And we also learned that piston speed is primarily controlled by the stroke of the crankshaft and the RPM of the engine. We also see how changing piston speed makes my engine fall into different performance categories.
Next time I will give you some real world examples I have tuned on the engine dyno and tested on the drag strip, as well as begin to talk about hw we get the air into the engine to take advantage of all of this piston speed we just talked about.
Cheers, Parker
I've been fiddling a bit with the Vette. I have a few projects to do now that I've become a lot more familiar with the car in the last two and a half months.
Although the car sounds cool, the cheap aftermarket mufflers are completely rusted inside. The baffles are all loose with lots of holes. On the outside they look new. They are the source of most of the rattles.
The lumbar supports on the sport seats don't work. I can't hear the pumps run so inspecting electrics first on those.
Rear speaker amps are toast. Expensive so it's not high on the list.
Steve’s 1990 C4
Tranny service due. No biggie and not expensive.
PRNDL lights are out. Not bad considering it's 22 years old and all other lights work. I was amazed at the sheer number of lights inside. Courtesy lights and mood lighting. The interior alone must have 15 individual lights.
Drivers side headlight motor needs to be repaired. It works most of the time. LOL.
It's a pretty short list considering the age.
It pretty much sits in the garage. We are in the 100's (110 today) this week so it's morning and evening use. The ac does not work but it still has the factory seals on the service ports so I'm hoping for good news there. We do have R12 available here. I unbolted the roof when I got it and it hasn't been back on since. I always wanted a convertible and the coupe is a good compromise.
The most annoying thing about the car is the static electricity. It doesn't shock me or anything but dust sticks to it like glue and the California duster only moves it from place to place. I never thought about a "plastic" body in that way. The duster works just fine on my steel cars.
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