With older Mazda rotary sedans and Rx-7s still demonstrating themselves to be formidable in SCCA racing, autocross, and even the drag strip, it's no wonder the rotary community is so large. It's been said many times that the track will determine the historic value of an automobile, and the Mazda rotary has certainly not failed to make it's mark in that respect.

Here I will be very happy to post photos of anyone's race car and/or crew. I'll also grow  an Internet link listing of reputable rotary racing service and product providers.

I'll also try to include rotary racing history in this section because racing history is always such an important part of the evolution of engine and sports car design.

Fuel Pressure

The race Nikki should have fuel pressure that is only as high as the highest fuel demands. This way, the emulsion system is kept from being overwhelmed as much as possible. Fine tuning for performance is a must to be competitive on the track, and tuning the emulsion system is the key to fine tuning the modified Nikki. If the emulsion system is drowned in fuel at any time during a race, you can bet the law of averages that it's going to be when you rely on it the most! So keep that fuel pressure down to where is just meets the demands of your engine at the highest RPM.

Ideally, the fuel level should be kept right at the halfway point of the site glass no matter what the demand is at any given time. This would enable the emulsion system to work to it's fullest potential, consistently. About the best we can do to maintain a consistent fuel level is to lower the fuel pressure so it does not exceed the maximum fuel demands of the carburetor, and to install Grose jets. Grose jets are a special needle & seat assembly that eliminate the need for the complex, rather less precise OEM needle & seat assemblies. Their advantages include the fact that they already have a consistent matched drop, the valve is actually a glass ball that can't bind, and the fuel inlet is .099 inches, whereas the fuel inlet on OEM seats measures .075 inches. This trouble free operation, and an increase in fuel flow to the bowls, which translates into a more consistent bowl level.

The Grose jets are an added expense, also, and they seem to be a bit difficult for me to locate thus far.

All SMW class specific racing Nikkis are modified only within the parameters defined by the sanctioning body. It is the customer's responsibility, if not obligation to be completely familiar with the rules and the "accepted interpretations" of them. Customers will need to be responsible for any regional-specific rules, amendments, clauses, etc that may further limit the modifications allowed on the Nikki carburetor for their class. I stand behind my work, but I only know as much as I'm told. I am aware of the basic SCCA rules for most classes, but I make it my policy to discuss them with my customers so that we are "on the same page". I can't afford the energy trying to defend myself combating a possible bad reputation if someone gets caught racing with illegal modifications on a carb I built for him.

Racers are among my most serious tuners and are more often inclined to hit the dynamometer with their car than most. I offer racing teams breaks on prices when I can by working out deals for dyno data. I don't have easy access to a dynamometer so any data I receive is always welcome, provided all the jetting and engine configuration details are also provided, along with permission to accredit the team with the dyno data. I will also work out situations with non-racing customers with the same conditions, but usually only after the sale is complete, and I am confident they do know what they are doing. In such cases I would offer future carb work at a reduced price, or perhaps a reduced price on a ported manifold or some other new product. I'm always open to service exchange ideas, but I'm not always in the best financial position to make such deals, so they are "hit or mss" opportunities all the way around. Never be shy about asking.

Track side assistance while jet tuning is pretty rare for me. That's why I hardly ever give out my cell phone number. If it's an emergency situation, I still need to know in advance, and then I'm usually willing to set up a call time. But basically, I'm making a huge effort to include everything I would ever suggest for performance tuning on the section of this site dedicated to that.

I also highly encourage racers to join and participate in the Back yard Mechanic's Club . There is a separate section devoted to racing, and all input from racers is always a healthy addition to any sports car enthusiast's forum.

The Legendary 'Left Hand Stumble'

When I discuss racing applications with regards to Nikki modifications, I usually use auto cross as my primary example. This is not just because I have several customers who auto cross with Sterling Nikkis, but also because the demands of auto cross racing are the highest. There is a great need for good mid range acceleration in auto cross, as well as for the carburetor to decelerate quickly and corner without stumbling. As I've stated many times, in any case, running at WOT can be optimized just the same no matter what the performance application. So the auto cross racing Nikki must meet the demands of all types of racing, with the exception of drag racing.

The Sterling Nikki is as optimised for the street as it is for auto cross. The only difference between a Sterling Street Nikki and a Sterling Racing Nikki built for competition with few modification regulations is the float set that I use. In auto cross and track racing there is a problem with the Holley, and to a lesser extent the Nikki, where upon exiting a left hand turn, there is a stumble. This is a known annoyance that most SCCA racers learn to "drive around". But any time that can be shaved off the track, and any distraction that can be eliminated is going to be good for the racer.

People are usually surprised when I explain to them what is actually happening inside the carburetor in these instances. The series of events that follows a hard left corner is rather simple but the problem caused by them is compounded and unique. Understanding what's really going on inside the carburetor will help those racers that are forced to drive around the issue because their class rules do not allow for one very simple modification...

Because of the orientation of the carburetor, the fuel is forced to the back of the float bowls with great force during left hand turns. As the fuel collects at the back of the float bowls, the primary emulsion tubes, and in severe cases even the primary fuel jets, are uncovered and starved of fuel for an undetermined, but minute amount of time. Two things happen while the carburetor is in this state; The main circuit delivers a lean condition, though the driver may never notice a decrease in power associated with it if he's feathering the pedal through the turn, and the floats drop, letting in more fuel.

When the car exits the turn and the G-forces acting on the fuel let up, the fuel returns to a fairly level position, but there's far too much of it. The emulsion tubes are completely submerged, and the carburetor is flooded. Because there is usually a down shift in the turn and a "power out" attempt upon exiting the turn, the driver is pressing on the throttle, trying to accelerate. At this point, the flooded carb would normally drop down to the appropriate fuel level fairly quickly on it's own. But the accelerator pump is adding even more fuel to the incoming air for a duration, and the engine bog that drivers experience is actually due to a rich condition from the combination of the siphoning of fuel from the over-loaded emulsion system and the action of the accelerator pump.

I've had many racers tell me ( in some cases, insist ) that they want baffles installed in the air horn of their race Nikki. I try once to explain why that won't work, and if they insist I do it anyway, I charge extra and I make it clear that I take no responsibility for the fact that it will make no difference. This is because the air horn gasket already traps the fuel and keeps it from climbing back up into the void at the top of the airhorn as much as any baffle ever could. No baffle installation is going to keep the fuel from going where artificial sideways gravity dictates. This baffle installation modification is a carry-over from the 70s when the gaskets used on the Nikki did actually allow for terrible fuel slosh. The current replacement gaskets are the same design for both the earlier Nikkis and the later ones, so there is no reason not to use an early Nikki.

A very simple and much more effective solution to this problem is to install the floats designed for early Nikki carburetors. These floats are only found in pre '79 and some '79 - '80 Nikki carbs, as far as I know, and they are full sized, as opposed to the later design that look like they are diagonally cut in half. I have not measured the volume of each float yet, but it's inconsequential. What actually matters is that they displace as much fuel as possible inside the bowl. The larger floats work by taking up room that would otherwise become a void that would fill with fuel when the float drops from the sideways G-force that throws the fuel to the back of the carburetor, when the float no longer has anything supporting it to keep it closing the needle valve. The carburetor will still go through the first stage of the cornering issue where the primary main emulsion tubes and fuel jets are uncovered, though it might be less likely that the fuel jet would be uncovered, depending upon your fuel pressure. But the second stage of the corning issue, where the float normally drops down allowing fuel to enter in will be much less dramatic, if it even happens at all. I have yet to test side by side comparisons of this issue. Testing such things is always difficult for me as I don't have easy access to a track, and racing around on roads is just never a good idea to check these types of things.