Base Set-up FV Alignment
For doing the following you will need normal metric/US hand tools, a couple tape measures, long straight edge or a Toe Plate Set) and a good angle gauge.
A lot of you visiting here might be new guys to FV. While engine tuning info and general racing info is available elsewhere and applies to most any class car, Vee chassis set-up is different. So, I will give you a few basics here. This will apply to most all zero-roll vees running the slick road race tires. (Hoosier, Goodyear etc.)
First let talk about the front end of the car. The items of interest are Toe (the parallel relationship of the two front wheels, Camber (the angle of the tire/wheel to the ground plane), Caster (the angle of the tire/wheel pivot point to the ground plane), and .
In the above illustration toe is typically referenced by the difference in inches from Measurement 1 and Measurement 2. eg. If Measurement 1 is 56 inches and Measurement 2 is 55 7/8 inches, you have 1/8" toe in. Correspondingly if Measurement 1 is 55 7/8 and Measurement 2 is 56 in, you have 1/8" toe out. There are a couple dynamics with this geometry that we will cover later. Given everything else equal:... A good starting point is 1/16" to 1/8" toe in. Excessive toe in will cause tire wear and the car won't turn in as fast. Excessive toe out will also cause excessive tire wear, the car will turn in very fast, but will wonder on the straights and dart right and left under braking. A faster setup is 0 toe in or even 1/16" toe out, but should be reserved for when you have lots of seat time and feel you are ready for it.
The above measurement can me made in several ways. You can get a nice set of toe plates (also handy for camber measurements) and tape measures from us inexpensively, or use some form of straight edges on the outside of each tire and then take the two measurements. You can also jack each wheel up and scratch a line into the tire as you spin it. Then you can measure between the lines on each tire.
One of the dynamics with the measurement is called "bump steer". Depending upon how your tie rods are mounted and the type of pitman arm and locations of both items can cause the above measurement to change under braking or acceleration. Most people would prefer to have no bump steer and have x toe at all ride heights. This may not be possible with your cars configuration. So you make a compromise: Adjust your toe for 0 at normal ride height (with you in the car) and set it for 1/16 to 1/8" toe IN under breaking (when the front end is low.) This can usually be achieved by placing shims at the tie rod ends so that the inside of the tie rod is slightly higher than the outside (the point at the wheel pickup). Then when the front of the car drops the tie rods will push the wheels into slight toe in condition.
Due to the loose sloppy front suspension on a VW link pin beam you really have to check the above periodically and certainly after any off course session. After awhile you might want to experiment with other settings.
Camber is usually measured in degrees and in the angle of the tire in reference to perpendicular of the ground. I.E. If your tire/wheel is straight up and down you have 0 degrees of camber. If the top of your tire is tilted in toward the center of the car 1 deg, you have 1 degree of negative camber. Tilted outward you would have 1 deg of positive camber.
On a Vee (like most race cars) you want negative camber. Optimum is in the 1.5 to 2 degrees negative on each side. Any more than this and you might find some better low speed corners, but you will eat up the inside of your tires more than desired. Any less than this and you will push more than desired. Camber is adjusted on a Vee by inserting shims between the control arm and link pin carrier in the top and bottom arm on the inside or outside. (Please refer to a VW manual for this visually.) The problem is that the original Link pin VW was designed for positive camber. So, when you insert the shims to get more negative camber the suspension will bind. To achieve 1 deg or more of negative camber you need to install an offset bushing set into your link pin carriers. Many Vees already have them installed. If not, you will need them. If you have these bushings installed you will probably be able to install enough shims to get -2 degrees of camber. Contact us for assistance needed.
Base Rear FV Alignment
This alignment is very car dependent and hopefully you have some original set-up info. But... you will want the rear wheels to be at about 0 or 1/16" toe IN (see above). This is usually achieved by adjusting your leading or trailing arms. Extending one and shortening the other. Keep in mind that in conjunction with this you want to keep the car square. You will need to measure from a fixed point on the front beam near the link pin carrier, back to a fixed point on the rear axle on each side. So you will have to adjust and measure several times possibly.
You will want the rear camber to be in the 4 to 6 degree negative area. (Total) Since if you have a zero roll suspension the full assembly can twist one way or the other, it is best to move the suspension so that one wheel is at 0 camber and then measure the other. (4 to 6 degrees on one wheel with the other at 0 is a total of 4 - 6) Each time you adjust, make sure one wheel is at 0 and then check the other. This is how I do it, but if you prefer, just measure both wheel and get the total to the 4-6 negative. This is with you in the car after you have bounced the suspension a bit to get it to it's normal ride height. This is normally adjusted by the push rods or spring collar. Either will work, but make sure that your car doesn't bottom out on the shock, bind the spring, the bell cranks don't hit the shock housing etc.
Now, jack up the back of the car from the bottom of the transmission and let the wheels drop to their limit. You should have a droop limit rod that limits the amount that the shock/spring can open. Adjust this rod so that the wheels go to about -1 degree. (I.E. The wheels will never drop to the point of 0 or perpendicular to the ground.)
(To be continued.)
Electric Fuel Pump
(This item FST Only)
Due to a quality issue on all new fuel pumps coming into the US for the T1 engine, Formula First has now changed it's rules to allow electric fuel pumps. (FST Rules). The good things are, that it fixes the quality problem and we can start our engines a bit faster after they have been setting for awhile. The bad thing (not all that bad) is that it has to be installed and wired in. Installation is pretty simple. Just find a convenient place to mount it, insuring that no fuel lines will come in close contact to exhaust pipes, etc. One wire goes to ground and one wire should go to 12V. This 12V pickup point can simply be the Positive (+) (15) position on your coil, or you can run it back to the ignition switch on your dash.. OR add another switch for the fuel pump. (No real good reason to do this.) Make SURE that it shuts off with both the ignition or fuel pump switch and your "kill switch".
A couple other nice positives out of the electric fuel pump. You can empty your fuel tank (for winter storage) very easily. Just disconnect the line and place it in a bucket and turn the pump on. You will empty your tank in just a few minutes. You can also easily check your fuel system for leaks without running your engine.
We spin these engines up much faster than they were ever intended to turn. Along with oil mods, balancing is the most critical item on an engine. The VW clutch housing, which is typically considered a bolt on replacement item, has become a problem. The new available diaphragm type clutch housings are terribly out of balance. Plus, they are not self centering. (I.E. They can be bolted on well out of concentric.) This was not much of a problem with the older "finger lever" clutch. It now is a big problem. We now do the final balancing of the rotating assembly with the clutch housing installed and pinned on the flywheel. If you are building your own engine, make sure your machine shop does this or if you don't, make sure your engine builder does. If he doesn't have his own balancer, he isn't going to like to do this, but it is almost mandatory for maximum HP and reliability.
Oil (and Air Cooled Engines)
I won't go into a lot of detail here, since there are posts all over the web regarding oils and what they do. But let me make a couple points:
1. Claims regarding oils that give gains of like 5 -10 % more HP, Fuel mileage, or 40 deg drops in operating temps are simply bogus. The total frictional losses in an internal combustion engine are in the area of 6%. (Lubrication Sciences, Mobile Labs tests, etc.) So even if you went from no oil to an oil that eliminated all friction (not likely), you might see 6%. (Actually we did some tests a few years ago and at normal operating temps, there was literally NO difference in HP or BSFC between any oils of the same ratings.) When measuring all the functions that oils provide, there were certainly differences in oil performance, but none as far as HP or economy.
2. There are SOME caveats to this. Assuming equal oil viscosity ratings. (20W, 30W, etc) a synthetic will provide some measurable HP (and economy) when below 140 degrees or so. Also at above 280 or so, synthetic is mandatory. It will remain as oil. However, a non-synthetic will fall apart. (Actually not at 280 degrees, but consider that at the actual lubrication points on the bearings etc. it is actually much hotter than that. The 280 that you are reading is the oil in the pan. So, I wouldn't even consider a non-synthetic in a full out race engine.
3. All oils are a compromise. It has to be formulated to be heavy load bearing (cams, and gears), it has to reduce friction at the lighter loads (bearings, cylinder walls), it has to carry away heat, it has to clean (detergent), it has to keep particles in suspension (sequestering agents), it has to be formulated to operate across all normal temperature ranges, and.... it has to be formulated so as not to pollute, destroy sensors, or catalytic converters. Many of these things are in conflict with each other. If you wanted to go real fast, you could use kerosene at high pressure for your bearings, but your cams and gears would be destroyed very quickly. Or you could use 90W gear oil and go real slow, but keep your mechanicals working forever. Other things would destroy the heat dissipation, or sensors, or cleaning capability, etc. You get the idea
For you FV racers (air cooled) there are some things that you want above, but some things that you don't care about. For example, lots of zinc is great protection for your bearings in those high G turns when you are likely to hit a dry spot once in awhile. All street oils have removed most zinc under government pressure. (Zinc destroys catalytic converters and 02 sensors)
So, for you guys with flat tappet cams. (FV/FST and more). You MUST us a high zinc oil. These are oils that are marked "For Off Street Use" or "Racing Only". If your engine is fresh, it is mandatory for proper cam and lifter break-in. I would recommend it for all racing use, but after break-in it's not quite as critical. Red-Line, Gibbs, Mobil One, Valvoline and more make an "Off Road Oil".
Air Fuel Ratio with the 28 PCI or 34 PICT Carb
28 PCI (FV)
One of the most important items on an engine is the air to fuel ratio mix that is getting into the cylinders. This mix is (hopefully) controlled by the carb jetting. For all practical purposes the two jets that we are most concerned with is the Air Corrector and Main Jets. The main is located under a 14mm (sometimes 13mm) brass plug on the side of the carb. The air corrector jet is the brass screw in the center of the air horn looking down into the carb. There is also a idle jet for setting the correct air fuel when the throttle is closed. The idle jet very little effect on a Vee modified carb, but I will give you info for setting it.:
After the engine is running and warm, back the brass idle mixture screw out a couple turns. Set the idle at the lowest point that it seems to run ok. Now turn the mixture screw back in until the engine idle drops back 50-100 RPM. Now adjust the idle screw back until it idles well. That should be close. Don't worry much if your engine doesn't react well to the adjustment. Your carb has been heavily modified for racing and the idle circuit is usually not very responsive. You are mainly interested in how it performs when the throttle is open.
You probably want your engine to idle a little higher than normal (1200+) RPM when warm. Less change of it stalling in a corner or under heavy braking, which can be somewhat distracting.
When the throttle is opened, the main and to a lesser degree the air corrector jets come into play. The main jet meters the amount of fuel in the mixture at most RPM and loads. The wider the throttle is opened the more air that comes in and thus the more fuel "sucked" in. However, at high RPM's and loads, the mixture will get excessively rich. That is where the air corrector jet comes into play. The larger it is the LESS the fuel is added (at high RPM). So it works inversely to the main jet. The bigger the a/c jet, the leaner the mixture becomes.
(Note that an FV prepped carb is pretty crummy in metering the a/f ratio below 2500 RPM. The car was designed for the tiny venturi that VW originally installed. Any race carb has had it's venturi replaced with one that is almost twice the air volume. This destroys the original low speed design. Also being 30 years old, there is probably lots of throttle shaft air leakage etc. You probably won't even be able to get the engine to idle well at below 1000 RPM. That's ok. All you want to worry about it that the carb works at 4500 RPM and above and particularly at WOT.)
Jet sizes are typically referred to as 190, 200, 210, etc. These number actually refer to the mm diameter of the jet hole. A 190 jet is actually 1.90 mm, a 210 is 2.10 mm, etc. MOST FV carbs will have a main in the area of 1.80 to 2.00. The air corrector will be 2.00 to 2.40. (BTW, these jet are not interchangeable.) However, noting the above relationship between the jets, It is possible to make a carb run fairly well with a 2.20 main and a 2.60 a/c. (as an example.) It probably is running very rich at low throttle openings, but might be fine at WOT (wide open throttle). (NOTE ! The jets were originally marked with the size on them by the manufacturer. However, most all of them have been resized and the tops rounded off (a/c jet). So don't go by the markings. You HAVE to measure them with a jet tool or drill bit.
All that being said.. carbs and to some degree engines can vary in the jet requirements. There are only 2 ways to make them perfect. EGT's and 02 measurements:
EGT (Exhaust Gas Temperature) is taken with a probe and gauge. The probe is located in the header at about 2" from the exhaust flange. After a WOT run of 10 seconds or so this temp should be in the 1250 - 1325 range. Anything higher than this indicates a lean condition and correspondingly much lower indicates a rich condition. Either will cost you horsepower and lean will hurt your engine. Neither will cause missing unless something is terribly wrong in jetting.
02 Measurements have to be made with a Wide Band 02 Sensor. (NOT, one of the cheaper >$150 narrow band systems. They cannot be used properly for WOT use.) Again, this is a sensor that is usually placed in the collector near the merge point of the exhaust pipes. It measures the amount of free oxygen in the exhaust gasses. The gauge or data collection unit converts the voltage developed by the sensor into an air/fuel ratio for display. At WOT this ratio should be about 13.2 : 1 to 13.5 : 1 on a Vee.
By far, the Wide Band 02 unit is a better way to determine mixture. An EGT is most acceptable when you have had you carb jetted correctly and you have a base line EGT. Then when conditions or the carb changes, you will be able to recognize it via the EGT reading change.
If you don't have one of the above instruments, keep the jet settings that your engine builder set up on the dyno. If for some reason, you don't have that info, use a Main jet of about 1.90, and an air corrector of about 2.10. This should get you pretty close. You can also send us your carb for set up. We will check it's performance on the flowbench and jet it on an engine on the dyno. If desired, a full rebuild of the carb will be done also.
Air Flow in General
Now that you have your air fuel ratio correct, you want to get as much of that stuff as you can into the engine. The rules stipulate the maximum compression ratio (via deck height and displacement). So, assuming you have a well built engine the only thing left to get more of the combustionable material into the engine is via your carb, intake manifold, heads and exhaust system. (Well, cam and cam timing also, but we will cover that a bit later.)
If you are racing ( and finishing above last place) you have obviously had your manifold, heads and carb prepped for racing. To find out HOW well they have been prepped, you need a Flow Bench. It measures the amount of flow that can be ingested by your engine components. There is no real way to do this without a flow bench. A good one will set you back several thousand $. So it's best to use someone else's. You can use ours. We will flow your components and advise you of their flow compared to hundreds of others that we have done. (Regional, National, Vintage, etc). One item of real note: While your heads and manifold will remain good (or bad) as far as flow goes over the years. There is a problem that we see quite often with carbs. The WOT setting. We see more and more of these things where the throttle stop tang is bent or has been modified by someone to open the "throttle all the way." Probably 1 out of 3 of the carbs we see are either not going to WOT, or are going PAST WOT. Just for comparisons sake, a good carb may flow at 112 CFM. That same carb opening just 1/32" past WOT (or short of) may flow at only 109 CFM! That is a lot of HP. The problem is, you CAN'T adjust by eye. You need a flow bench. Call us if you suspect this. It's fast and inexpensive to fix.
Another potential for limiting air flow: We see many engines come in with the stock 28pci carb gasket. This gasket (especially when compressed) squeezes into the air flow. Even a slight shroud at this point can cost you several CFM. Use a 30pci gasket or open the standard 28 gasket by a 1/8" or so, and make sure it is centered on the flange. The same type of problem can be true at your intake manifold where it mates to the head. Check this.
Cam Timing and Lift.
Ok, let's talk about cam timing. On a legal FV, we are stuck with the stock cam specs. This means we use a cam that was built for a 40 hp 4000 RPM motor. Normally to get more air/fuel into an engine we have to increase the duration of the cam or the lobe lift. We can't do either. But we can do a couple things. One is cam timing. We retard it a few degrees. Lots of people wonder why. Some even wonder why not advance it. Here is why: We are mainly interested in these engines producing work at high RPM above 3500+. If we retard the cam timing the intake valve opens a bit later, and that doesn't hurt much. However that delay keeps the intake valves open later. So even though the cylinder is through its intake stroke, the air mass is still moving down those intake runners at high speed. Instead of slamming the valve in it's face, we leave it open to get that mass forced into the cylinder. (It is called a supercharging effect.) Of course there are no free lunches, we sacrifice some torque at the very low end of RPM, but we don't care. Typically a Vee cam is retarded by 2 to 5 degrees. This retard moves the peak torque point (and HP) by a few hundred RPM. While it is a only a slight trade-off on the low end, it free legal HP at the high end, where we want it.
Lift is more obvious. The bigger the valve opening, the more flow we can get into it. However all we can achieve is what the rule book says. (.3365" Exhaust and .354" intake. So push rods length, rocker tip adjuster shape and subsequent valve geometry is designed to get it as close as we can. A flatter adjustment tip on the adjusting screw will give a bit more lift. The longer the pushrods (without rocker arm interference etc.) the more lift that can be achieved. Get as close as you can to the above measurements, but leave some buffer for legality.
Ok, yes, there is one more way to get more flow into the engine. The exhaust system. It's not just pipes for the cylinders to push burnt gasses through. It "scavenges". And some scavenge better than others. Where the exhaust pipes come together (collector) the system is designed so that when gasses flow out one pipe they create a low pressure in the pipe(s) next to it. This low pressure "scavenges" that pipe so that when that cylinder goes into its exhaust stroke, it will not only see less back pressure, it will clear the cylinder better and allow more of the new air/fuel in on the intake stroke. It's not all quite that simple, but you get the point. The length, diameter and design of the exhaust pipes and collector dictate how much gains and at what RPM they will take place. However the gains are significant. On a Vee as much as 2-3 HP difference can be seen between a good set and a poor set of designed headers.
You can't get much HP or better handling out of your Vee with the electrical system, but you can make sure you finish more races. Make sure all your screw and slip on connectors are firm. Put a dab of clear RTV over each connection. It keeps them from vibrating loose, corroding and even helps to prevent shorts with nearby items.
I can guarantee you that $50 spark plug wires, expensive coils, etc. will not get you .001 HP on a Formula Vee engine. We have very low compression ratios, run at very low RPM (Only 2 cylinders per revolution fire, vs. 4 cylinders on a V8), so it is a very trouble free system with no gains to be made with high dollar items. . However, you do want to ensure that what you do have is working. Make sure that your spark plug wires are secure, Points fresh and dwell adjusted properly, a clean distributor cap (inside and outside) and wires that don't have cut insulation and aren't crushed.
Dwell and Timing
Dwell is simply a resultant measurement of ignition point gap. Dwell is the length in degrees that the points will be closed during a full revolution of the crank. The original VW called for about 42-44 degrees of dwell. You could measure this with a dwell meter, or achieve approximately the same results by setting the point gap to around .017" at the highest opening point. Thankfully, it not real critical so the adjustment was easy either way. You coil is "charged" during the time the points are closed. At the moment they open the coil releases it's energy as the high voltage spark to the distributor cap where it is "distributed" to the plugs. Since we run at 4000 to 7000 RPM, it is better to set the dwell to 52-55 degrees. You can get there by adjusting your point gap to about .015. Again, it's not real critical. What IS critical is that the points opening is going to determine the timing. So, any time you adjust the points, you MUST adjust the timing. Timing is adjusted to about 36-37 degrees advanced. This point should be marked on your front pulley by your engine builder. Adjust it for the mark when the engine is reved to about 3000 RPM. (At lower RPM the timing will be much less. When the engine is reved up, a set of weights in the distributor give it more advance. Full advance is where you will be setting the timing. This should occur by 2500 RPM.) Remember point gap or dwell is not critical, but Timing IS. (If you have upgraded to a Pertronix or other electronic ignition system, dwell is not adjustable and the above can be ignored. See next section.)
Ignition Modules (Pertronix I , Pertronix II, Compufire and EMPI)
These modules are now legal in FV (and have been in FST). There are 4 types that I know of. (3 Manufactures). We did some testing here on them and comparisons against the standard points. First... None of them will get you any more HP than a good set of points will. However, points can go bad, come out of adjustment and invariably have to be replaced periodically as a matter of course. So the above can be a good investment. Any of the above will give you a few more volts to the plugs. Not that we need any more, but it's nice to have them. They all install pretty easily (15 minutes). They all provide a little more spark voltage to the plugs, with the Pertronix I and II having the edge.
The Compufire units that we tested seemed to have
more spark scatter, and we saw 2 failures on track with them. This is the same
unit sold by EMPI under their name.
The Pertronix I unit had less scatter and we haven't seen one fail yet, (unless connected backwards <g> )
The Pertronix II unit is more money, but has a built in dwell extender according to the manufacturer. In theory, this extended dwell would saturate the coil better for better spark at higher RPM. Not bad, but probably overkill for a 4 cylinder engine running below 8000 RPM. (Our coils already get as much saturation as a V8 running at 4000 RPM.) But I have been told that they made other improvements also.
Another nice thing is that you no longer need the condenser on your 009 distributor when you use these units. So your investment is paid off pretty quickly. Also, if you are using a Data Acquisition dash/system, you may find that the Pertronix will clean up the RPM signal a little better.
Warning: These units all hook-up very simply with 2 wires across the coil. HOWEVER make sure you have the right wire connected to the right place. When points were connected wrong, you destroyed them also, but it only cost you a few bucks. These will also be destroyed immediately and it will cost you much more.