bjhines

The Accelerator pump design for the Webers is unique. The Pump piston is mechanically raised whenever the throttle is closed. Fuel is drawn into the cylinder and the pump is ready for operation. When the throttle is opened the piston is actually driven down by a spring(not the throttle arm). This allows the duration and volume of the extra fuel to be controlled by changable jets. The system has 2 check valves. Both check valves ensure that a full charge of fuel can be drawn into the cylinder as quickly as the throttle shaft closes(very quickly). The upper check vavle(21) ensures that fuel is drawn from the bowl not the delivery passages. The lower check valve(23) allows fuel to fill the cylinder at a high flow rate. This lower check vavle also houses a bleed hole that will allow some fuel to be(slowly) returned to the bowl. The amount of fuel delivered and the duration of the charge can be altered by changing the delivery jet size and the return(bleed hole) back to the bowl. I think there may be alternate springs as well. To answer the idea that fuel is drawn from the accelerator circuit all of the time; This is NOT true. The accelerator circuit has a weighted check valve(21 the wedge shaped piece above the ball) that will not allow venturi vacuum to draw fuel through the accelerator circuit.

Ahhh.. Emulsion tube.... A problem inherent in all Carbys is slow response time. One of the ways they improve the response to rapidly changing conditions is to "lighten the fluid" in the passages. They do this by mixing the fuel with air-bubbles. This is where the emulsion tube comes into play. The shape and placement of the air passages in the E-tube serves to mix the bubbles with the fuel in the well. The emulsion well ensures that there is plenty of extra fuel available to the E-tubes when instant demand sucks fuel out of the well faster than the main jets are replenishing it. The heavy fuel in the main jets is slower to begin flow and the inertia of the heavy fuel keeps it flowing a little too long. The E-tube and it's well act as buffers in the system and greatly improve the response time. About the plethora of E-tube designs: The various E-tube designs were intended to work around issues with various carby applications. A quick revving race motor has entirely different requirements than a slower reving street engine. The positions of the air holes are also intended to work with specific float levels. You really need to figure out which application the various E-tubes were made for and then look up the float levels and jetting that particular E-tube was designed for. As an example: one of the designs I have seen has passages drilled at angles. I figure that the passages were intended to maintain constant flow even when the well was nearly emptied. This would make sense on a race motor where the engine can rev very quickly. A lot of fuel may empty from the well before the main jets begin to flow enough to replenish it. The angled passages help to "lift" the fuel into the rest of the system.

IMO, The Webers are indeed an all-out race carby. The lack of a low-vacuum enrichment circuit on the DCOE Webers is their Achillies' Heel for streetability. That workaround can bandaid so many situations where the Webers want to fall flat on their face. This is especially true for the larger choke sizes and relatively low velocity, highly pulsed airflow through the venturis. You have to keep in mind that each "barrel" of a DCOE sees a single pulse every other revolution. This means that airflow is not even close to smooth flowing.

Scott, You post in disagreement about choke sizes and in the same post you inform us of your 13 second, modded L28. My experience is not from just one car. Your engine may make fine use of larger chokes, but the Datsun/L6 kits these carbys came with are not that large. Secondly you are hunting for power above 6Krpm. A street driven Z car needs torque at lower RPMs to be "fun to drive". Larger choke sizes and street drivablilty are mutually exclusive. If you want both then go EFI. I noticed a few comments about the large choke size results from a chart. There has been a commonly available chart for some time that has been mis-read by a large number of people. If it is the chart I am thinking about, RE-check your math, The chart is for a FOUR cylinder engine using 2 carbys. We have a 6 cylinder engine that uses 3 carbys. You need to plug in displacement values that are only 2/3rds actual displacement for the numbers to work out correctly. There are a lot of ways to get good driveability out of a set of DCOEs. I am not saying that you cannot get good driveability with the larger chokes. It will take a great deal of time and money to finally get that tune. The larger choke sizes make the carbys much more sensitive to ambient conditions and fuel quality even if you find just the right jets for any one set of conditions. This means you will need a notebook and a year to tune for all conditions. You may have had good luck with the larger chokes, but I know for a fact that a shop could never turn that tune over to a customer and expect it to work for more than a few months or in rainy weather. Most S-30s do just fine with 28mm chokes. The DCOE 45s are considered a race only carby and most class-limited L6s run 30-34mm chokes. The Weber DCOE design is a highly tuneable carby. It gives the user control over virtually every aspect of metering. It does have it's shortcommings. The lack of a power-valve/circuit can make these designs a little harder to street than the typical Holley. It is ironic that a Holley built for road racing will typically have the power circuit disabled and the main and transition circuits jetted much more like a Weber.

^^^^ you have bad wiring or connectors. The voltage sensing wire must be solidly connected in order for the voltage regulator to work properly. A fault here would cause the votage to increase a limited amount. 17 volts is generally the internal limit for these devices. That would explain one problem. As far as the alternator "blowing", I dunno. It could be tied to the VS problem. It could also be the result of arcing connections freaking out the semicinductor devices and causing damage. If your VS wire is faulty then there are likely other faults as well. Alternator wiring is very improtant. They are often low in the vehicle and prone to fouling and heat damage. Make sure your wiring is in order and these problems will go away.

The overall body size of the carbys is WAYYYYYYY bigger than the useful venturi size. Most 40mm carbys came with 28mm chokes. My DCOE 45mm carbys are using 32mm chokes. That is for track use ONLY. They are shitty on the street. I tried 28mm and I tried 34mm chokes. The smaller the chokes the more responsive the carbys are at midrange RPMs. The larger chokes do not provide enough vacuum to pull fuel through the main circuit until you are over 4k RPM @WOT. ANY street driven Z car should be using the smallest chokes possible. 28mm is a good starting point. The larger the chokes the harder it will be to tune and drive. Ohh.. and as a side note... Changing the choke size will change everything!!!! you will need to COMPLETELY rejet every aspect of the carbys with any change in choke size.

Yes... It falls flat on it's face at WOT under 3k RPM due to the large chokes and late comming on the main circuit. ...

http://forums.hybridz.org/showthread.php?t=115259

Kirby I can compleely agree with what you have said. It is correct but not something that cannot be deviated from at all. Solder connections are usually reserved for wires that carry high frequency signals. In that case the connectors sheild the wires from interference and serve as high quality strain reliefs. The S-30 fuse panels and internal splices are often a source of heat and failures on these old cars. Many people solder the rivets on the back of the fuse panels and solder the factory crimps. Someone who has a lot of skill with a soldering station can do a very good job without stiffening the wires too far from the splice. Typical heat-shrink can properly protect his kind of splice.

The typical Haynes Manual diagrams and the factory wiring diagrams ARE WRONG!!!! There is no correlation between these diagrams and the actual Main power circuits in your car. This really blew my mind when I finally tore several harnesses apart to find how it really works. Here is a greatly simplified picture of how the main power circuits REALLY work in your early S-30 ...

Ummmmmmm.... You may get airflow into that hood scoop. But the highest "pressure" may be in the front clip. There is a whole lot more air moving out of the way of the front clip than there is trying to get into the little scoop.

Most modern sports cars have smooth undersides. I can take some pics of a Porsche, E-46 M3, Minis, and a Lancer EVO, etc. None of those cars have tunnels or diffusers, But they have near-perfectly flat undersides. The tunnel areas are covered and the lower control arms have plastic inserts to smooth them out. There are often trip-strips right before the suspension components(front and rear). I have also seen scoops or turnouts near the control arms to divert air into the wheel wells(brake cooling).

A better idea for the S-30 may be to simply smooth out the underside of the car and keep air from getting caught behind the rear roll-pan. Maybe you could figure out how to get the rear filled-in better ...

I have some pics of a 360 spyder underside to use as examples. Notice that the area under the driveshafts is only crossed by the wing shaped lower crossmember. The suspension pickups are outside the framerails. This leaves a nice "Tunnel" area under the Ferrari. Our Datsuns don't have this kind of space for a tunnel.

Hmmmmmmmmmmmm... Ride height Camber gain Anti-dive Caster Ackerman bump steer all of these change or could be changed to improve handling on a race car.

shiny side up guys!!!

Carbon/Aramid composite unibodies are on the way. This is what it will take to get the MPG numbers you want along with safety to boot. You will also see simplification of suspension and braking components on these future cars. For example. The springs could actually be areas of the unibody with "flex" that a simple control arm would bolt directly to, instead of a complex spring+shock+upright+control arm+track rod set up used on today's cars.

how the hell does the fuel stay in the bowls with the carby so far from the crank center. That is a slosh-monster for sure.

I used the above diagrammed system with the exception that I put the PCV valve on the block vent after passing through an air/oil separator. I plumed the valve-cover top vent to the exhaust venturi. I was running a cheapo muffler that was fairly restrictive at first. It still pulled vac on the system. The vacuum was significantly improved when I installed a turbo muffler. I also connected the original tank breather vent valve in it's original configuration.

More people can drive the GTR faster than the Vette. The Vette is typical of a challenging, high-horsepower, rear drive car. The GTR is something your grandmother could drive as fast as you could.

I made some judgements based on the structure of the car. I looked into this with a cagebuilder who knows spec classes pretty well. We took some liberties with my design for sure. The accepted design has been to attach to the tops of the wheelwells. The usual design uses the belt-retractor pockets instead. JM used the rockers to attch his hoop which is probably the best design for safety. I am more worried about hitting a wall, not as much by a T-bone incident.

It can be done without the tool. But a proper connection that will not pull loose needs the proper crimp tool. You also need to practice with the tool to ensure you get a well set crimp. There is also a pin pusher to release the pins from the sockets. This is a smart purchase unless you never make mistakes.

I have pretty much figured it out in my head, that it is cheaper in the long run to order automotive paint and the most basic parts of the product system. You don't need every type of additive on the list to do the interior, engine bay and underside. I used single stage NASON paint. The automotive paint is so much tougher than the types of paint sold at the hardware stores. It is also VERY DANGEROUS if you breathe the droplets into your lungs. The paint goes on thick and lays out smooth. It resists sags and runs. It hardens to a mind boggling shine. The stuff is so damn glossy you do doubletakes before you put your hands on it.

Most people use relatively thin spacers, 10mm or so. Good spacers are hubcentric with a male and female side. This is to repeat the original hub ring for the wheel to engage. Lugcentric like our cars are... can be a bit harder to do right. The jury is out on what is good for the common man in this regard. I know from others' experience to constantly check the lug nuts on my modified vehicles. The stock system was designed to be idiot proof. If they are properly torqued then they will not generally loosen by themselves. Sytems with modified wheels or added spacers may not actually tighten properly the first time around. You have to tighten wheel lugs in at least 3 steps. The spacers add an extra bit of slop in the system, this adds complexity in properly torquing them down. Besides all that, I have found that they tend to loosen the first track session. I usually have to retorque them at least once before they stay in spec.

What? No paint??? lol. I have had the paint on my interior for 1 year and the damn thing is still not complete.