A lot of good points made here, but itâs interesting that there is no real consensus. The idea behind this thread was to propose a solution to a rule problem that does not allow all cars to achieve the same amount of camber. Although car preparation is a large part of racing and will never be equal, parity is very good in our series, but there is an issue with front camber. Iâve measured many crankshafts, pistons, and other engine components and found that BMWâs manufacturing tolerances are ridiculously tight. Itâs odd that same precision isnât seen in the front suspension and max camber variance is as high as a few degrees. Perhaps BMW used lower quality technicians in the suspension assembly, but thatâs unlikely. Itâs more likely that our suspension components have either been intentionally or accidentally bent over the last three decades.
In a spec series, fewer rules are generally better. Any time a rule is added, cost could be increased and there could be unrealized unintended consequences of creating loopholes that allow creative tinkerers to gain a performance advantage. Considering that, rule stability makes sense, but there is no reason why some of our rules cannot be improved to remove some of the loopholes and match what actually gets enforced at the track. In my opinion, a rule is no good if itâs not enforced or itâs so difficult to enforce that the officials donât spend money or time on compliance.
Robert Patton makes a great point that can be applied to a lot of our rules in that âbent stuffâ canât be enforced and this idea was considered when rules were changed to delete the max camber rule. The reality is that we would not be talking about this issue if all cars had equal camber; that is not the case and the only difference between cars that impacts camber is in fact the geometry of the suspension components. My car was originally started by another builder for CCA KP class and I donât know what may have been adjusted in the suspension before I purchased the car. I bet that precision measuring equipment would point out that my struts are slightly different than a garage queen E30 which would also be different when compared to a 300,000 mile beater car that has hit thousands of pot holes. But like Robert said, why bother? It would be costly, time consuming and just a pain in the ass to spend the time measuring strut tubes at the track.
So we have a rule that does not allow folks to bend there strut tubes. Thatâs fine, but the unintended consequence is that folks will have to swap strut housings until they find a set that provides the desired camber. Thatâs time consuming and expensive; some racers will do it and some will not. Itâs ironic however, if they find a strut housing that allows a lot of camber, they are just finding a strut housing that has previously been bent either by pothole, accident, a well-intended shop, etc⌠Ignoring this consequence and not changing the rule in some way will put some racers at a disadvantage. Although I have never installed a cherry strut housing on a pristine car and measured the camber, my bet is that if I did, I would not be able to achieve -3.5 degrees of camber.
If the idea is a level playing field in car preparation, the current rules are obviously pretty good, but I also think itâs important to improve the rules when issues are pointed out. Scottâs idea of new a new spring design would require every racer to buy new springs and is simply too costly. Paul Baconâs idea of setting a minimum camber of -2.8 degrees is a good one if that is what can actually be achieved by a pristine car with verified âstraightâ strut housings. In my opinion though, Robert Pattonâs point on why bother to enforce bent stuff is the simplest idea to enforce and this should also be included in a rule modification so that many racers donât have to change their strut housings if the maximum allowable camber is reduced. That said, I like the current rule and prefer that we just add a provision for strut housing modifications that is well thought out and worded to only allow folks to add camber. The obvious consequence is that some racers will have to work a little bit harder to get camber to where many of the front running cars are already.
I donât agree with Paulâs idea of new rules to prevent maximizing compression ratio by applying a minimum cylinder head and block thickness for two reasons. First, many of the current LEGALLY âbuiltâ engines may not comply and it would be costly to many to replace out of spec blocks and heads. Itâs really not fair to change the rules in a way that makes a currently legal car illegal after implementation of a new rule. The second and bigger issue is that itâs a bad idea to create rules that canât be enforced. There is no non-destructive inspection method that could reliably provide any indication on block and cylinder head thickness. Cranking compression is not going to change much and there are many other factors that have a much larger influence on cranking compression. The only way to inspect would be disassembly and to actually measure both thicknesses. The unintended consequence of a very difficult to enforce rule is that honest racers will remain honest and cheaters will cheat because itâs easy to not get caught. In my opinion, this falls in the why bother category because enforcement would be so unpopular and costly that it would never occur and simply create an easy way for some racers to gain a performance advantage (if done properly). It also falls into the why bother category because increasing compression is only one of the many legal improvements you can make when building an engine. Increasing compression alone can actually decrease torque because of other things decking the block changes and otherwise only has a very small change in engine performance.
The front running engines are not making big power because they have thin heads and decked blocks. Sure it matters, but the very small increase in compression through decking is only one of many factors that will help engines perform better. Besides, you really canât go very thin on the head (or block) without having piston to cylinder interference. The Bentley specs 4.909â as the minimum thickness for cylinder heads and most heads start out around 4.930â or so from the factory. Going below the Bentley Spec effectively, by decking the head or block, will put piston to head clearance less than .040â. Below .030â, you WILL start having piston to head contact. Removing .021â from the head or block only provides ~.5 increase in compression ratio in the very best case. The thermal efficiency of an engine is a function of compression ratio and air. With the properties of air remaining constant, 8.8 and 9.3 to one engines are 58.1% and 59.0% thermally efficient respectively. Assuming all other things affecting performance remain constant and engine management can actually take advantage of the increase in efficiency, increasing compression ratio by .5 could theoretically improve performance by 2.4WHP. However, the actual performance increase will likely be less. Again, why bother to create a rule that would be extremely difficult to enforce and the maximum achievable performance advantage that rule might influence is within the margin of error of repeatable dyno results? Many other things matter a lot more than compression.
