Improved Rules wording needed

[tb911]

One of my goals as the Rules coordinator has been to improve the wording of vague or otherwise confusing rules.
This week it came to my attention this is one of those:

III E. Induction system modification:
Electronic or CIS to carbs/mechanical injection and/or Venturis or fuel distributor/controller other than original -- 4 pts.

So how can we improve the wording?
I need some help from the techies, for example, what does CIS stand for?
Also, since Tom Tweed stated that fuel distributors and controllers are specific to CIS and Motronic, would someone tell me what they are/do?

How about:

III E. Induction system modifications replacing electronic fuel injection or CIS with carburetors or mechanical fuel injection and/or
non-stock carburetor venturis, CIS or Motronic fuel distributors or controllers -- 4 pts.

thanks

[tb911]

Oh, yes, it probably goes with out saying, but we can't change the meaning of the rule, only the wording for clarity.

Second, I need this quickly, gotta go to press in a few days.

thanks

[Tim Comeau]

CIS= Continuous injection system.
Anything other than stock original is going to be for improvements in HP, right? No one's going for better fuel economy, right? Can we assume that any change will be for an increase in power? If so, might we simplify the rule by stating that any change to any part of the "mechanical fuel delivery system" i.e., from the gas tank to the combustion chamber, is 4 points? Chips would be separate and electronic, not mechanical.

[tb911]

Actually, we can't make that assumption.

Often MFI is removed because of expense or pain in the neck factor to maintain it.
I know that is true of 914 injection as well.

And the result is sometimes less horsepower

[ttweed]

So how can we improve the wording?
I need some help from the techies, for example, what does CIS stand for?
Also, since Tom Tweed stated that fuel distributors and controllers are specific to CIS and Motronic, would someone tell me what they are/do?

We need the hardcore techies to chime in here, but I'll do my best and they can correct me. The CIS system was the next evolution beyond pure mechanical fuel injection by Bosch, which Porsche used beginning in the early '70s. As Tim said, it stands for "Continuous Injection System" and was also known as "K Jetronic" injection. It is actually an "electro-mechanical" system which bridged the gap between MFI and the later true EFI of the Bosch DME (Digital Motor Electronics or "Motronics") system. Take a look at this article http://www.ncr-pca.org/?option=com_content&task=view&id=48&Itemid=2 on the PCA-NCR site. The fuel distributor is the "control center" of the CIS, metering fuel to the injectors according to the position of the air sensor plate positioned before the single throttle butterfly, with compensation for fuel pressure and volume according to a number of ancillary electronic/mechanical sensors. As more air enters the manifold, the sensor plate lifts, pivoting an arm that connects to the control pin in the fuel distributor, allowing pressurized fuel to flow to the injectors. Here is a schematic of the CIS used on a (gasp!) Corvair engine:


The early Bosch Motronic (DME) systems integrated the spark timing element with then-existing Jetronic fuel injection technology to create a complete electronic engine management system. The heart of the Motronic system is an electronic control unit (ECU) consisting of a microprocessor and memory. The memory contains a program with data for determining the injection amount and the moment of ignition for varying conditions (engine speed, load, air pressure and temp, etc.). Sensors provide the microprocessor with information on the amount of intake air, engine speed, crankshaft position, etc., at over 6,000 times per minute. The sensors are, basically, the air-flow meter, the speed sensors and the temperature sensors. The fuel is metered by signals to the solenoids that control the electronic fuel injectors, by altering pulse width of the injector (how long it remains open). Thus, the ECU is the "fuel controller" in this instance, rather than the mechanical "Fuel Distributor" of the CIS. Revising the fuel and ignition maps in the ECU's memory is an easy and quick way to increase output, if emissions and fuel mileage are not considered. This can make a ridiculous amount of difference on a model like the new Turbos, while being nearly undetectable without sophisticated equipment.

There are multiple ways that these systems can be tweaked to improve performance for our P-cars, through conversion and upgrade processes, which is the point of the induction modification rule penalty. Emissions and fuel efficiency has been a big concern of the Porsche engineers for many decades now, and their engineering choices have been guided by the need to reduce harmful emissions and fuel consumption to meet smog rules and consumer demand for high fuel mileage cars. In racing, emissions and fuel efficiency are less prominent goals. Carbs and MFI are simple systems which make good power with great throttle response, due to the nature of their design, with an individual throttle body for each cylinder, but they are not very fuel-efficient and big smog producers. The CIS and Motronic systems depend on a single throttle body and air sensing port feeding a "plenum" type manifold, which suffers from a lack of immediate throttle response compared to ITBs, as well as from reversion pulses in the manifold if too "hot" of a cam is used. It was a design compromise for efficiency's sake, which Porsche has spent the remaining decades improving, with ever more sophisticated design revisions, up to the current Varioram intake with variable valve timing as well, which has finally resulted in engines with the same specific output of 100+ HP/liter in the new GT3 street and race cars that they achieved with the original carb'd and MFI Carrera 2-liter engines in 1967, but with far greater efficiency.

How this development applies to our competition rules is a very complex subject, and it is difficult (if not impossible) to write a rule which would apply fairly to all the possible induction modifications. Simply changing a CIS car to carbs with no other mods renders an instant improvement in throttle response, but not that great of a power increase if measured on a dyno. Bruce Anderson has said that it is perhaps a 5-10 HP improvement, but it feels like 20 or 30 because of the increased throttle response. To take full advantage of the carbs, the cams should be changed from the mild CIS profile to the more aggressive early "S" cams or hotter. The USA-spec CIS on the 911SC, for instance, can be upgraded to the Rest of World (ROW) system, which had a different fuel distributor and larger manifold runners to the individual cylinder ports to gain a few HP, but the Euro version of the SC engine had higher compression as well, so simply changing the induction will not give you the full HP of the Euro motor. An extreme example of what can be done with cubic dollars is this engine owned by PCA member Randy Wells:

This began life as an early 2-liter motor, which has been increased to 2.7 liter displacement, with a later Varioram induction system adapted, along with a Motec M48 engine management system replacing the Bosch Motronics. The most powerful 2.7 factory air-cooled engine for a street car built by Porsche that I know of is the Type 911/83 1973 RS engine with MFI making about 210 HP. The water-cooled 2.7 Boxster engine made about 240HP in it's most powerful version, I believe. This engine can make 270 HP with street cams and 290 HP with race cams and appropriate tuning revisions to the Motec system, and easily fits into an early 911 chassis. And this is without any forced induction! I only mention this because it represents the difficulty of "rules writing" due to the kind of range of revision/modification that must be addressed, taking into account the entire evolution of Porsche cars.

How about:

III E. Induction system modifications replacing electronic fuel injection or CIS with carburetors or mechanical fuel injection and/or
non-stock carburetor venturis, CIS or Motronic fuel distributors or controllers -- 4 pts.

I looked at the language of this next year's rule and last year's, and it did not change, as far as I could tell. The real change was in 2008-2009. The 2008 rule read:
Induction system modification:
Electronic or CIS to carbs/mechanical injection --- 4
Venturis or fuel distributor/controller other than original --- 4
Thus, we used to have a two-tiered rule with separate penalties which were consolidated to a single "and/or" 4-point penalty. I think that was a good move, because custom engine modifications have historically been more harshly penalized than stock engine swaps for the same sort of HP increase, IMHO. If you are making these kinds of induction changes, they are usually accompanied by other displacement/head/cam/compression changes which carry their own additional penalties.

As far as how the wording might be improved now, I think you have a good start, there, Tom, but I would rather see something like:
III. E. Induction system modification:
Induction system modifications replacing older, stock electronic fuel injection or CIS with carburetors, mechanical fuel injection, or aftermarket EFI with Individual throttle bodies (or later-model Varioram system); replacement of stock carburetors with MFI or EFI systems; and/or modification of stock carburetor venturi and jetting configuration, upgraded CIS or Motronic fuel distributors, manifolds, throttle bodies or controllers (including ECU and MAF sensors) -- 4 pts.

That's my best shot--let the experts fire away and refine it. I intentionally included "venturis and jetting" as a "coupled pair," neither of which should be penalized without the other, as I don't think a venturi change alone offers much improvement without matching jetting reconfiguration, and some jetting changes are necessary in the older engines to accommodate the modern fuel formulations compared to what was available "back in the day," even with stock venturis. Hopefully, this wording also makes it clearer that an MFI to carb conversion is not penalized, only the carb to MFI conversion is specifically called out.

That's my $.02, and I've probably overlooked something...
TT

[tb911]

Thanks, Tom, much appreciated

Will discuss with Steve G tomorrow and that should wrap it up!