Rules

#21

I’m very much for the spec exhaust. This is definitely an area that is not "spec". I don’t care when it is implemented and I’ll buy 2 exhaust systems if necessary but I’d like to see a spec pipe. I like everthing else. Except the bumper rules :stuck_out_tongue:

#22

robweenerpi wrote:

This will not be adequate I don’t think. It is possible to add hardened material to an OEM cam without changing lift, then grind it to a different spec. You can add duration without increasing lift which can give a marginal gain that is very useful. I’d prefer if we came up with a very detailed spec on what the cams must be in lift, duration, and overall profile.[/quote] this is the issue Spec Miata had. Unmodified factory cam should be the spec OR all specifications of the cam need to be defined. This issue got real ugly in SM

#23

Good posts everyone.

It’s 6:15 here in the east.

I’ll be on the road for the next few hours but will try to address some of the questions tonight. Days Inn has free wireless!!

And we will act quickly on all these issues.

Carter

#24

The 318is will be a problem for you guys if you don’t control the cam specs. The M42 has a Higher VE because of the high compression which helps suck air past that inlet restrictor BMW called a MAF in the 80’s. There are allready cheater grinds for ITS M50 engines that will swap directly over to the M42 head. We also have adjustable cam gears which help tune the engine. I think a 140whp ‘cheater’ M42 would be no sweat for a good engine builder. If somebody had more budget than I they could obsolete the 325i, or get the 318is handicapped in just a few short races right now.

It theoretically is possible to build a jig that attaches to the head with the valve cover off. Measure the cam at multiple points in it’s rotation to check for a stock profile. If you are different from the known stock measurement, you get DQ’ed.

Kinda screwing myself on the horsepower end as it’d be rather cheap for me to throw that package together, but I’d rather it be fair for guys with salvage yard motors.

#25

Rob, that is the spirit. Perhaphs Spec e30 can pick you up as an inspector. What an idea… Like I’ve said many times, we’ve all raced before and the experience factor is a great deterrent against out-of-bounds rule bending. Trunk lights be darned and tool kits will be removed, but any big stuff will be noticed.Regards, Robert Patton

#26

Carter wrote:

[quote]Good posts everyone.

It’s 6:15 here in the east.

I’ll be on the road for the next few hours but will try to address some of the questions tonight. Days Inn has free wireless!!

And we will act quickly on all these issues.

Carter[/quote]

Mike and I are discussing the few issues tonight and over the next couple of days. And when I say that we will act quickly, mostly regarding the exhaust, I mean that the spec will come out quickly (in the next couple of days) for the new car builders but that it won’t be required quickly. No current car will have to swap the exhaust until after a grace period because it won’t be too far from what most cars have now.

Carter

#27

Can the exhaust spec just be the number of tubes and tube size and we leave the muffler free? I really don’t want to spend money on another muffler. The tubes I don’t really mind if those get spec’d since that’s cheap.

Oh, and Mills has a locked diff on his 318. So you might get some resistance from him about that. :wink:

#28

Carter wrote:

[quote]Carter wrote:

[quote]Good posts everyone.

It’s 6:15 here in the east.

I’ll be on the road for the next few hours but will try to address some of the questions tonight. Days Inn has free wireless!!

And we will act quickly on all these issues.

Carter[/quote]

Mike and I are discussing the few issues tonight and over the next couple of days. And when I say that we will act quickly, mostly regarding the exhaust, I mean that the spec will come out quickly (in the next couple of days) for the new car builders but that it won’t be required quickly. No current car will have to swap the exhaust until after a grace period because it won’t be too far from what most cars have now.

Carter[/quote]

Carter,

Why the change for exhaust all of a sudden? Given all of the other items that we limit, is changing out the exhaust going to yield that great of a difference?

I am going to admit that I have a custom exhaust that no one else has. But, it is because I do not like the sound of the typical "two pipes and cherry bombs at the end" exhausts.

If there is definitive evidence that a custom exhaust will yield a significant advantage, then it is probably a good idea. But, there does not seem to be concrete evidence, either from dynos or in our discussions, that it will provide an unfair advantage.

-Steve

#29

Personally I like the idea of a spec exhaust that is simple, cheap and adds HP. Other than street legal, another consideration is Laguna Seca has a 92db limit. I would prefer to not see the street be a lowest common denominator, and would happily swap out a street/Laguna Seca exhaust for a couple of HP at the track.

The earlier point that some higher dollar / shop equipped guys will have sways for each track is almost a given in my mind - it’s an adjustable variable.

The only other thing I would add is that it would be nice to have the free $ upgrade of removing the driver’s side highbeam light for cold air - it would help both the stock airbox guys as well as the CAI guys and costs nothing but 10 minutes. Easier, cheaper and less intrusive than the allowed airbox fab.

Carter / Mike, thanks for asking for thoughts from the community.

Cheers,
-aj

#30

Looking for data…Steve mentions that there is not a definite difference in exhaust and performance. My dyno experience does not reflect that exhaust systems make a hill-of beans difference. The definition of a hill-of-beans:

The results were from Laura’s car with the runs done in the same morning

With stock cat and stock muffler:134.0 137.6
With two straight pipes: 137.2 141.0
With two glass-packs loud: 138.8 143.8
With two glass-packs quiet: 139.9 144.9
HP difference: 2.7
Torque: 3.9

Well, maybe the difference is more than a hill of beans. Clearly the catalytic converter robs power, 5.9 hp and 7.3 torque. And, surprisingly the open pipes were not the hot set-up. The vanes-toward-the-exaust-flow glass packs (quiet numbers) added some backpressure (?) and made the best number,. Or was it dyno error, or was it a fully warmed-up car? The 1.1 and 1.1 numbers were not enough for me to chop off the "loud" set-up that was already installed on the Taxi Cab and reverse the direction of the vanes.

The testing on Laura’s car was done last March to try and find out why the car was so slow as compared to the Taxi Cab. I finally found the problem, an aftermarket/will-fit cylinder head that was used in an earily engine overheat/rebuild. Subsequently a BMW head was installed an the car makes respectable numbers in the low150s.

Regards, Robert (slow for three years in the police car) Patton

#31

Post Script…The rules allow you to use adjustable fuel pressure regulators. Why? Why not delete the sentence from the rules? I’ve yet to see a front-of -the-pack car with one installed. I can save you the trip to the dyno store…No go ahead and spend your $200 for the regulator and $75plus for the testing.

Yes, the BMW engineers are smart.
Yes, you lose power with higher pressure and no ability to tune the ECU.
Yes, SCCA ITS racers sucessfully used them in their cars, but they had a different engine rules package.

Regards, Robert Patton

#32

Thanks for sharing that dyno/exhaust data.

-Matt

#33

Patton wrote:

[quote]
Yes, you lose power with higher pressure and no ability to tune the ECU.
Yes, SCCA ITS racers sucessfully used them in their cars, but they had a different engine rules package.

Regards, Robert Patton[/quote]

Probably because we cannot run a header (in addition to not being able to tune the ECU). What’s the stock A/F mixture ratio look like? I was thinking about toying with it since I had good success with the Lindsey on my 944, but I also had a different chip and header.

#34

Eric, the fuel pressure dyno test left me bewildered.I thought that more pressure would translate into more fuel per injector opening and a richer a/f ratio. At 40psi the a/f was about 13 give or take. At 50psi it dropped to 12.5, at 60 psi it went way south to 11 with a dip down to 10.2. Power dropped 5hp and 3 torque. End of test. The stock set-up looked good to me and I returned the borrowed BMP Design fuel pressure regulator. Did I do something wrong?

And now, back to the discussion on rules…

Regards, Robert Patton

#35

Patton wrote:

[quote]Eric, the fuel pressure dyno test left me bewildered.I thought that more pressure would translate into more fuel per injector opening and a richer a/f ratio. At 40psi the a/f was about 13 give or take. At 50psi it dropped to 12.5, at 60 psi it went way south to 11 with a dip down to 10.2. Power dropped 5hp and 3 torque. End of test. The stock set-up looked good to me and I returned the borrowed BMP Design fuel pressure regulator. Did I do something wrong?

And now, back to the discussion on rules…

Regards, Robert Patton[/quote] the O2 sensor will defeat the higher FP by shortening the pulse time of the injectors to try to keep the ratio correct to the stock fuel map

#36

Hi All,

Just wanted to add my $.02.

First, thanks Carter for starting the thread and soliciting feedback and for all who have responded. It speaks well of the whole class and gets me all the more enthusiastic about getting my car ready and getting out on the track with everyone! :woohoo:

I’d agree with making a ‘spec’ exhaust being a priority. Having one design would certainly make things simpler (for me…someone who hasn’t spent any money on one yet. I undertand and appreciate it could be a problem for those who have already spent the $$ on their design).

Thanks for all the great information and participation through this forum. It’s been a huge help to me!

#37

Sean, thanks for helping me understand the error in my test.Live and learn…

So, what you are saying is a pressure regulator can only work if you remove or "unplug" the O2 sensor. Since the rules don’t say that an O2 sensor can be removed…well it can’t be removed. I can’t wait for some goober to challenge Carter on the definition of a functioning trunk light or a functioning O2 sensor…

In the meantime, for all of the tech administrators to note: If Freddy Fastguy has a fuel pressure regulator on the car you should hand him a FUNCTIONING O2 sensor and have him install it in your presence. Geez… Carter, remove the temptation to play with fuel pressure as the spy-versus-spy games are no fun for either party involved?

Regards, Robert (too dumb to unplug the sensor) Patton

#38

Given Patton’s info, I’m not sure it’s worth making so many cars change their exhaust. Not a lot of variation in those numbers on the same car. Don’t you like talking about stability…or something? :wink:

#39

Patton wrote:

[quote]Sean, thanks for helping me understand the error in my test.Live and learn…

So, what you are saying is a pressure regulator can only work if you remove or "unplug" the O2 sensor. Since the rules don’t say that an O2 sensor can be removed…well it can’t be removed. I can’t wait for some goober to challenge Carter on the definition of a functioning trunk light or a functioning O2 sensor…

In the meantime, for all of the tech administrators to note: If Freddy Fastguy has a fuel pressure regulator on the car you should hand him a FUNCTIONING O2 sensor and have him install it in your presence. Geez… Carter, remove the temptation to play with fuel pressure as the spy-versus-spy games are no fun for either party involved?

Regards, Robert (too dumb to unplug the sensor) Patton[/quote] unplugging the O2 sensor puts the ecu into a default map all the time I think…I have to look that one up. The factory FPR works off intake vacuum…disconnect the vacuum hose to the FPR and the system will run at whatever pump pressure is(43 or 46 PSI) if I remember right. the fuel map at a given RPM expects to "see" a certain FP and times the injector pulse for that pressure. If the fuel pressure is too great, you get a rich condition because the air didn’t change. Too rich and you dilute your oil, this cannot lead to good things.

#40

I just finished my car and I hope we don’t start making changes already. In my opinion, the exhaust is no big deal. let’s leave that alone. A good driver can make up for 5 hp. I know that I am in big trouble dyno wise already because unless you are taking the engines out and using engine dynos, there is no way these cars are going to make 170 hp at the rear wheels stock. I don’t mind random checks of ECUs, bring it on. If a car is significantly faster than all the others in a straight line, then you have something to look at.

Regarding locked diffs, I vote removing that from the equation and limiting diffs to standard LSD as from the factory. You can shim them and get a little more locking but it is not the difference between losing a winning. No big deal.

Mirrors aren’t going to make you faster, just safer. I run a BSR 17" flat mirror that allows me good vision to the rear and side to side at a single glance.

I want to say again that I am looking forward to racing in this series because it sounds like fun and I know the cars will be more equal. I come over from 5 years in BMWCCA club racing in prepared classes and one year in stock class.