I hate to think what the number of hours would be. Many of which have been spent drinking coffee and scratching our heads while engineering solutions for problems that none of us have encountered before...data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
Are you still hoping to make the Pod for Easter?
Unfortunately Easter is no longer a possibility. With the hold ups in recent weeks and another car in the workshop having the last of its tinwork being finished (another fuel FC as it happens), it's pushed plans back a little. The next round of the championship isn't until the end of June, but most of my crew aren't available until Dragstalgia in mid-July - so that's the intention. It's unlikely to have paint on the body, for cost reasons (a barrel of fuel, barrel of oil and sundries comes to the same amount as the paint).
That's still not a lot of time - so needs must, I've taken to assembling bits of engine in the spare bedroom at home... data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
I thought it time my Lego Technic Porsche met some proper horsepower data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7.
With the fuel system bits and pieces back home, it's time to start assembling it all for the last time. Or at least it would be if some small parts had arrived... delays in the US. They're good enough to try and save the customer money by shipping everything in one lump, but when you're only waiting on some bolts, it's frustrating that the rest of the order hasn't been flown over.
In any case, to explain the fuel system further, upside down as it were - I talked about the role of the bugcatcher injector before. Many will have seen these before, if not at the race track, probably in films such as The Fast & The Furious etc.
/proxy.php?image=http://i264.photobucket.com/albums/ii184/topfueldigger/DSC01911_zpsuxocchcx.jpg&hash=6d133f88278580dfe5aaa4ffb895b0a4
These can carry up to 8 fuel injector nozzles and allow the motor to drink around 1.5 gallons per minute at idle. Lower down in the intake manifold is where the bulk of the fuel goes.
/proxy.php?image=http://i264.photobucket.com/albums/ii184/topfueldigger/DSC01913_zpsxqahphwi.jpg&hash=4971cc9c2bf68d85157b578cbd1b69bd
The number visible is the nozzle orifice, in thousandths of an inch. Typical numbers for these will something like 50-55 in the injector hat and a staggered arrangement in the manifold but with much larger numbers (low 70's up to high 80's).
/proxy.php?image=http://i264.photobucket.com/albums/ii184/topfueldigger/DSC01918_zpskkfovfb4.jpg&hash=69ea4dbea0a91557a2fd06e210ab2bf7
When the poppet valve in the port line check valves (seen here with the orange blank off) exceeds 10psi, this opens and allows fuel to be distributed to 8 more injector nozzles, one per cylinder.
/proxy.php?image=http://i264.photobucket.com/albums/ii184/topfueldigger/DSC01914_zpsmycdghfl.jpg&hash=edc97611e9f3e683e10d9452a7e9a3c2
As this manifold was designed originally for big show cars, it has provision for 3 injectors per cylinder. If you had the pump volume these would be used, but with a baby fuel pump as dictated by the rules, one per cylinder is sufficient. These nozzles point at the intake valve and go a long toward providing the 21.0 gallon per minute target.
/proxy.php?image=http://i264.photobucket.com/albums/ii184/topfueldigger/DSC01916_zpswlp0icn0.jpg&hash=bfe95e34166549c8076f0869cb77e0aa
/proxy.php?image=http://i264.photobucket.com/albums/ii184/topfueldigger/DSC01917_zpsc0eh1f9i.jpg&hash=ff79c0b4db0f4c88f56e767e097fe1db
The burst panel at the front of the manifold is a safety feature, mandated by the rules (in nearly all blown classes nowadays). It allows a build up of pressure to be relieved by giving way before the manifold and blower assembly make an escape for low Earth orbit. The manifolds come either cast with the opening in them (like this one), or you'll see them be machined if it's aluminium and of Chevy / Ford / Chrysler application.
Onto the clutch. I'll perhaps do a comparison of this versus the first choice clutch in a few weeks. The differences are mostly cosmetic as the physical operation is similar but the lever locations are different.
/proxy.php?image=http://i264.photobucket.com/albums/ii184/topfueldigger/DSC01908_zpstp5ujcrt.jpg&hash=efefe7bb44806efe8e77d65582f8fb05
This is the spare clutch which might well be sold on shortly - there's nothing wrong with it, I came to acquire it as a package deal and whilst it's a lovely bit of kit, there's no crossover for spare discs and floaters due to it being a 10.5" all titanium deal rather than the 10" part titanium one.
Much like a moped, it's a slider clutch that locks up under centrifugal forces. Adjustment is 3-fold. Firstly the air gap which decides with how much force the clutch is initially applied, is set by adjusting the stands you see in the photo below. A good track will allow you to get aggressive and open up the gap for it to hit harder. A poor track needs a softer transition. 0.040" is the typical figure that's a happy medium between the two.
The holes allow them to be spun up and down the threads. All of these clutches, without exception are a pain to adjust for air gap as the top cover needs to sit flush and you're often chasing your own tail to ensure each stand is the same height.
/proxy.php?image=http://i264.photobucket.com/albums/ii184/topfueldigger/DSC01910_zpssa50uvd6.jpg&hash=e1bbe61c9781f3034fefbed9ef5135c0
The 6 springs in the top photo control idle pressure i.e. how much the the clutch locks up when the car is stationary. These are set generally to allow the springs to turn but not freely. This is a rule of thumb that normally means the car can coast by itself, much like a torque converter road car. The difference in this instance being it'll want to coast at 30-40mph on occasion.
The 6 levers are what decide the rest. How quickly the clutch locks up depends on the weight on the fingers. More weight equals more mass turning and therefore it locks up quicker. The nut & bolt arrangement is where weight is added or subtracted. We adjust in grams, sometimes a little can make a lot of difference.
The goal is to have the clutch fully locked before the 1/8th mile. It also helps reduce wear - as the fingers rotate the radius on the heel of them pushes into the pressure plate, jamming the clutch pack together.
There's a whole science about this element, with different radius finger heels (compound curves, normal curves, you name it). I've never deviated from the standard fingers that the clutch comes with - maybe in the future.
Of everything that goes into a nitro burning race car, the clutch is what makes or breaks a run. The crowerglide type of clutch has been used in nitro racing since the 1960's, as technology moved on, the design didn't change all that much, it just (as most American things) got bigger and then electronics and control systems came in...
A current Top Fuel and Funny Car clutch looks like this:
/proxy.php?image=http://www.darkside.ca/sites/default/files/clutch-fuel2.jpg&hash=259f6e564f3aa30468c43b9406d98e47
18 levers, 10 stands. All titanium construction - these use a canon system where if you imagine the levers throw out (the fingers will throw toward you as you see it) the throw out bearing is controlled by a pneumatic or hydraulic system controls how quickly, and at what rate it locks up by restricting the lever movement.
This is perhaps the most critical difference between and old style and current Top Fuel clutch. When you're able to accelerate, pause or decelerate the lock-up action of the clutch, you have much more control over proceedings and can tune for track conditions - especially when you consider the amount of power available and that track conditions may vary down track and you have to be going a decent speed before aero kicks in and allows you traction over and above the mechanical traction the car naturally has.
With the old style clutch we use, track conditions are assessed (you walk to the start line, dig your heel in, wiggle it, cross your arms, squint, perhaps let out a small grunt) and decide what it'll take. It's really not very scientific. There are few things as rewarding as getting the call right and having a glide clutch lockup just right, with none of the modern day trickery. Old-skool!
In a few weeks once the SFI tags are sorted on the actual clutch I'll be using, I'll do a proper comparison, and also a weight check - I myself don't know how different they are in raw weight, but when such a mass is hanging off the back of the crank, the rear main bearing prefers to be abused as little as possible by a big titanium lump bobbing around data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7.
To my eye, these are all things of beauty. But that would make a very expensive coffee table/ mantle piece item.
Things a coming together now.
Can't wait for the final build to appear in the AV Forums classifieds data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
Disputed trades
This doesn't seem as economical as I'd hoped. //static.avforums.com/styles/avf/smilies/facepalm.gif
And it seems to have removed my fillings, rolled my eyes so they won't stop and ruptured a spleen when leaving the lights.
I suspect I'd need to enlist lawyers with more intelligence than Volkswagen did when it comes to explaining discrepancies with emissions... data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
This is indeed a great thread, thank you for taking the time to document and share. I used to be involved on the bike scene many years ago crewing for a TF Harley that used to run at the Pod and Avon Park (and anywhere they would have us) a lot of hard work and fun, good days.
keep the updates coming and if I get to the Pod this year I'll look you up...