Bring me your Under-Tired, your Poorly Performing, your Huddled Massflow Sensors . . .
. . . Yearning to Breathe Free on the Tracks of America!
How to Approach Track Driving. . .the RIGHT Way!
1) Choose your car. Most are tempted to go for more than they can truly handle. In reality, almost any car will do.
2) Make sure it is up to snuff mechanically. Tons of dollars spent on upgrades IS NOT NECESSARY at this point, and is actually COUNTER PRODUCTIVE. If the shocks, brakes, and tires are good, then you're ready to drive.
3) Only when you are easily capable of exceeding the cars limits, yet in a completely composed and controlled manner, should you consider upgrading to better components, or a better car.
If you can't SERIOUSLY hustle a car around the track, while scraping the door handles off, in complete serenity,
YOU HAVEN'T EARNED IT!
When you HAVE earned it . . . come see me!
If you've learned your basic lesson and truly earned your upgrades, then it's time to consider improvements. This is just such a car and owner. The owner has become quite a track junky since beginning the build up of this car, averaging 30-40 track days a year. The car has MANY mechanical upgrades from stock, but there are still many original items remaining. Not all of these upgrades were working that well together to make the driver's job easier. In some respects, they were making it harder. The owner is now easily capable of overdriving the car, and has reached the point where further improvement of his skills and enjoyment require improvments to the car. BRAVO !!
This is a multi-faceted project. The first thing I tackled was improved oil cooling.
This 77 930 has a larger Turbo, Electromotive ignition, Kokeln intercooler, and adjustable boost. As skill was gained, and boost added, oil temps began to rise past the 250 degree level, and the search for improved cooling was necessitated. At right is the cooler arrangement the car had. As you can tell, it is not nearly an efficient setup. The cooler is large, but does not look particularly modern or efficient. Further, it was simply bolted to the front body panel, with virtually no provision for air to flow through it. Not good.
A 911 is not an easy car to get a front cooler in with efficiency. There is very little space behind the bumper to mount a cooler, let alone get any airflow. The early cars had no coolers at all. The mid-model years had a "Trombone" cooler in the right fenderwell below the headlamp. This was certainly better than nothing, but not up to the rigors of track use. Many folks install the popular Mocal fender cooler system, which does improve things some. Still, the fenderwell area is NOT a place that is conducive to proper airflow characteristics.
High speed air is what you are looking for, to some degree coming in, but more importantly, going out. The original system was in the right place for input, but if air can't get out, you won't get much in!
I am nobody's idea of an engineer or aerodynamicist. I work on instinct and intuition, and have developed some theories based on this. Hopefully, my thoughts are correct and my ideas actually work to at least a moderate degree! ;-} Obviously, airflow is important, both in and out. The area below a front bumper is very high pressure, full of turbulent forces as the air hits the front bumper and tries to find a way over, around, or through it. Some of the air does go over the hood, and stays at a high velocity. Some goes around, some goes under. These last two aspects combine to render the fenderwell coolers far less efficient than you might imagine.
Air, like water, will follow the path of least resistance. The air going around and under the bumper forces its way into the first void it can find; the wheelwell. All of that air stuffs intself in this area faster than it can get out, making the pressure extremely high. In such a contained space this creates LIFT, which you obviously don't want! It also severely limits cooling airflow, both for any oil systems present, and for the brakes. You might have noted that this is a Slant Nose 930S. Part of that package is the vented fender tops. These vents allow the high pressure air to escape the wheelwell, thereby reducing lift. This is also the reason for the common prototype extraction method of openning the fender up behind the wheel.
What about the air that forces intself under the bumper? Like in the wheelwell, there is only a limited amount of space there, and this space, if less than the air that enters it, becomes extremely high pressure. You guessed, LIFT... AGAIN! Spoilers and splitters only do so much to keep this air out from under the bumper, and cars can only be just so low.
In any event, this is a very turbulant, high pressure aerodynamic zone. Good for air intake at the front, but would it then make sense to try and exhaust your oil cooler air in this vicinity? Methinks not! Chaneling airflow away from this area before exhausting is the only solution. One way of doing it is the classic prototype method of ducting the air up through the hood, which I did on the 911 GT3 Racer I built some years back. However, this is not quite a viable method for the average car. No, the air can only go two other places; either under the front of the car somewhere, or out the sides of the front spoiler, ala various 993 and 996 versions of the 911. But that is expensive in terms of plumbing, with lots of hoses, two coolers, and limited space.
I have developed a theory for removing this air to a point under the chassis. I executed this theory recently on the 914/6 GT Conversion project I did. It is a method that hopefully gives decent airflow characteristics relative to other methods, while not requiring huge invasions of the sheetmetal or mechanical assemblies. Given the high pressure area immediately under the front of the car, my idea is to move that air through an angled front mounted cooler, down and under the front portion of the body through a fabricated air channnel, and having it exit somewhere in front of the steering rack. My theory is that the turbulant air that has entered under the car has to some degree straightened itself out and begun to flow more swiftly by the time is goes past the wheel centerline. This means that it will be a better place to exhaust cooler air, perhaps even creating some vacuum to pull air through!
As you can see, the old cooler was just a bodge. Not only didn't the air get out, because it wasn't in the middle, not all of it could get in either! Out it goes!
Here's the first salvo, the first cut through the front body panel to fit in the massive modern cooler, placed properly! Full use of the openning, proper placement to utilize all the available air, and no restriction behind it to let that air in AND out. The last shot brings the plan in to better focus and shows you more of where I'm headed.
I like to protect my coolers. Nothing is worse than sticking a $4-500 cooler out there in harms way where it can get biffed during even the slightest moment of agricultural driving. I also like to provide my customers with ease of securing their cars on the trailer. The signature REDLINE tow hooks! Here you see the frame boxed in and the cooler in place.
Here we see the lower baffle assembly being fabricated from 0.50" steel square tube and aluminum sheet. The side panels are made to fit close to the underside of the body, and an aluminum panel also closes the opening from inside the trunk. It all comes apart pretty easily for maintenance.
The bottom panels are installed with only a very few sheetmetal screws at left. Above is the path air will take as it flows through the air chanel.
The front body will receive the original Wurth body coat and all the pieces will be painted. Then all that's left is to put together the braided stainless line and fittings, and to fasten it all together. It should make for a neat and effective system! Since this part of the fabrication is done, we'll jump ahead to the next part of the project.
a driver for wanting to be safe!
We had been talking cage for a year or so. The mechanicals have settled down to the point where the car can now be driven, so it was time for some safety. At right is the main hoop. Look closer. Oh yeh... there IS a tube there! You can also see the side hoop intersecting it, and both again below at right. Pretty sanitary install, eh?
You can get a cage lots of places. But one that is this slick takes time, patience, and thought. Tubes running every which way simply won't do. 911 interiors are cramped enough without some bundle of tubes and all their compromises stealing what's left. In fact, until the rear braces go in, you won't hardly be able to see the cage from the outside! Maximum use of space, and having the tubes running so close to the body means they can easily be welded to the existing chassis, making use of and increasing what stiffness is already there.
Late last summer, we got rid of those faltering 25 year-old-sport seats in favor of some nice racing seats. I am a particular fan of the Kirkey racing seats compared to all but the more expensive fiber seats. They are light, stiff, compact, the covers replace easily, and they are cheap! You can also get them in a wide variety of styles, sizes, and colors.
This happens to be the little known Pro Street Drag Seat. They make a nice compromise between the old style NASCAR rib crushers (which nobody uses anymore), and the beautiful but expensive Deluxe Road Race model. These were installed with custom fit double locking sliding seat brackets. Less than 25lbs each fully installed!
At last... some "Final Photos!"
(Remember... these cars are never done! ;-)
Since this page is already pretty big, and for the sake of the dial-up viewers, click the link at right to go to the final page. (final... for now!)
I am installing a full Leda coilover system on this car. At the far left you can see the stock rear shock mount. It is fine for handling only the load of a relatively soft stock shock absorber, but it is defintely not designed to handle the entire weight of the car plusall the suspension loading, which it has to do when the torsion bars are eliminated. These mounts have been known to fail even when retaining the torsion bars and only adding a stiffer shock! We don't want any such failures!
After some discussion, the owner also decided he would like the rear suspension mount points x-braced to the cage to further stiffen the chassis. This sort of requires cutting through the rear body in some fashion to do a proper reinforcement. In this case, the piece that I cut out will be replaced by fabricated, removeable access cover. The panel below the mount area will be reconfigured a bit for all flat panels to fit.
I removed the top portion of the original mount, and fabricated a new one from 0.50" steel. It is easy to see why these mounts fail, because I didn't have to get my air chisel in very far before the whole cap popped right off!
Here's the next piece in the puzzle, the rear uprights. Here is where we get our first direct piece of triangulation. The triangle is the stongest of the geometric shapes, and if you look at any well built race car, you will see lots of them. From the humblest street stock right up to the last of the super hi-tech 911GT1 Porsches, the triangle rules.
Triangles are so strong because they are made up of the least number of straight lines, and - in cage use - usually corners of no more than 90 degrees (optimally less). If you have a triangle with all angles under 90 degrees, it will be super strong. Straight sections are the strongest of linear forms, so one can always look to areas that are not straight for good points to reinforce with triangulation. The area that this upright lives is just such a place.
The frame section that this triangle sits on receives all of the suspension stress, and since the major mass in a 911 is in the rear, all of those static and dynamic loads as well. The frame section here is very tall and made of thicker metal in multiple layers, but all of this cannot fully overcome the curved shape. This triangle will go a long way toward stiffening the entire area.
At right you see the almost finished rear cage structure. It is an extremely efficent setup; very stiff, not that intrusive to space or rear view, and allows nice access to the front of the engine which is never accessible at all when the engine is in, even if you do remove a lot of intake plumbing. Once the cover is made, it will be a snap to service items in this area.
The last item in the rear cage will be a removeable belt bar. In cars I've built previously, the seeming abundance of rear space and access is ruined by this piece, but the removeable bar will maintain that opportunity. It doesn't seem like a big deal, but when it is all fixed in place, you just can't do a thing because of the belt bar in the way. Considering there will be a lot of monitoring and diagnostic electronics going in the rear area, access will be important.
One important factor in making a cage easy to live with is getting the tubes tucked as tightly inside the perifery as possible. Of particular importance to ease of ingress/egress is the lower attachment point for the side hoops. If these tubes cannot go through the dash somehow, they must bend down very early and attach to the rocker sill a fair distance out into the door openning. This makes them very much in the way of your feet as you try to enter or exit the cabin. Definitely a pain, especially with a race seat... extra especially if you are my size!
If you have a nice vent or speaker hole in this area of the dash (like a Series II 944), and can live without its original function, you can get them tucked in pretty well. If you are fortunate enough to have a car that can be further modified, the sky is the limit.
At left is a nice, neat approach to finishing off what otherwise is always a rather unattractive spot. I simply formed some sheetmetal pieces and used them to attach the end of the dash (which I had cut off) to the side sill and
Here's a side hoop. The bend at the base of the windshield that kicks the tube in to follow the windshield pillar upward is the tricky one and causes the most difficulty because it takes the top and bottom sections "out of plane" to each other.
Figuring the length of the straight sections is simple, and getting the bend angle right is fairly easy in the longitudinal sense (using the homemade angle gauge pictured), but in the radial sense it is REALLY difficult. If all
the bends were made in the same plane using the same tube centerline it would be simple, but when you take it out of plane with the windshield pillar bend, you also change the centerline for the bend at the top of the pillar.
How do you get side hoops to fit as well as these? Well... I don't know how other people do it, but I revert back to my Tinker Toy days. It is far too difficult and wasteful of time and materials to take pot shots at getting things right, so I make up "Tinker Toy" prototypes. I measure the angles and bend short sections of tube, sleeve the 1.75" main tube with 1.5" scraps, and tack weld them together inside the car to create an actual pattern of the appropriate relation of the bends. This protoype you see (bottom) is then used to calculate the centerlines for the various bends to create a perfect piece (top) the first time. It may seem time consuming to do this, but my experience has shown that in the end it saves a lot of time and material. The snug fit of the finished product doesn't lie!
Here's the removeable belt bar mentioned previously. Easy in, easy out, allowing easy access to the rear compartment.
Arguably the most important bar in the whole system. Yes, the windshield bar is key. In truth,
you rarely see any other part of the roof come down but the front. Not just any bar will help. First, you need some curvature to provide some amount of arch for strength. A straight bar not only infringes on forward visibility, but will simply buckle and then pull the side hoops in if stressed to even a slight degree. The curvature in this bar will send forces down into the side hoops, spreading the load into the rest of the system in compression instead of isolating the load in one particular spot in shear.
Since this is a very isolated part of the cage which cannot benfit from much in the way of triangulation, the tube braces in the corners are quite useful in adding some rigidity to the area. The finishing touch of "webbing" the corners with sheetmetal not only further strengthens the area, but it looks nice too!
cage. A little filler followed by a coat of paint will make for a very pleasant result! Incidentally, the rest of the dash will be getting a complete makeover later on in the project.
Remember the seats we did last year? Well, they needed some further help. Commonly a driver's head will hit the headliner, as it did here in this sunroof car. Further, I have never been a big fan of the early 4-bolt mounts using tiny 6mm fasteners running into sheetmetal.
These new mount rails were built from 0.125 angle iron and utilize 10mm bolts. Oh yeh... they are also lowered 1.75 inches!
It all looks pretty basic, but trying to get all the angles right and
Here is our strut project. We will be doing awesome Leda coilovers later, but first we needed a nice home for them. 911s are impossible to get enough negative camber in. The only commercially available option is to go with fragile and EXPENSIVE 935 adjustable front control arms. REDLINE has different ideas, naturally!
A new top plate was fabricated from 0.250 steel. With it tacked in place you can clearly see the space - and thus camber - limitations of the old tower and cap (cut out, above). The angle gauge was initially used to get a reading on the relative angle of the old tower cap to approximate it for the new setup.
Those of you paying close attention will have noted that not only are the bearing mount plates (which I made) slotted, but the tower plate is as well. Not knowing exactly where the zero camber mark will be, this provides a huge range for adjustment. A quick check at left to see that everything is positioned such
that all of the top plate's adjustment can be utilized, and then it's on with the rest of the tower.
The almost-completed tower is at right. The top is made of 0.250", the side of 0.125" and the front & rear of 14ga. steel.
welding to a center tunnel crammed with hoses and wires is definitely not easy. However, the increased headroom was sort of mandatory, and the vastly improved solidity of the seat mounting will be worth the effort.