S.A.S.C.
Solo => Technical Talk => Topic started by: Jackal on September 28, 2016, 11:02:36 AM
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Hi All,
I'm starting this thread for interpretation of the Street Class rules. Although limited, there may be some questions about what may or may not be permitted.
Hopefully this thread can be collectively used for folks to prepare their cars effectively for the Street class only. No Touring, Prepared, Modified chat here please.
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I'll start.
I have the 2006 Z4MC and I would like to remain in BS as this particular M car is omitted from Touring classes and skips straight to Prepared.
MY question is in regards to Exhaust bypass cutouts. As per the rules for Street Class Exhausts....
"Any part of the exhaust system beyond (downstream from) the last catalytic
converter, if so equipped, may be substituted or removed provided the
system exits the car in the original location and meets the requirements of
Section 3.3.3.B.16, Section 3.5 and Appendix I where applicable. Vehicles
equipped with exhausts that exit in multiple locations may change to a single
outlet in any of the original locations. Stainless steel heat exchangers
are permitted only if the physical dimensions and configuration remain
unchanged."
Realizing that the cutouts will have their own challenges with sound limitations, does this rule look like cutouts may be a legal modification? I like the idea of getting the power from the bypass, and if I have a variable switch for it, I should be able to ensure I'm under the sound limits as well. I just want to be sure I'm within the letter of the law.
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My Second question is a bit funny.
I love the look of the Z4M with a GT style wing on the back of it. Staying within BS won't allow it. However, if I were to remove the actual wing itself but leave the uprights on the car, would that still qualify as a BS car?
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I'd say no to exhaust modifications you're looking at. You have to run the tailpipe to one of the holes in the rear bumper after the cat anyway. Or are you thinking muffler on one side outlet and muffler-less on the other side? I think the added weight and complication wouldn't be worth it and even that might be a no no.
The rules are basically saying you can replace the "cat-back" portion of system all you want and can goto a single outlet if original was a dual outlet.
I don't think anyone would protest having the uprights left for the wing but if you trophy anything can be picked apart that isn't OEM or specific in the rules as it is allowed.
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I'd say no to exhaust modifications you're looking at. You have to run the tailpipe to one of the holes in the rear bumper after the cat anyway. Or are you thinking muffler on one side outlet and muffler-less on the other side? I think the added weight and complication wouldn't be worth it and even that might be a no no.
The rules are basically saying you can replace the "cat-back" portion of system all you want and can goto a single outlet if original was a dual outlet.
I don't think anyone would protest having the uprights left for the wing but if trophy anything can be picked apart that isn't OEM.
Basically my idea would be to have the stock exhaust fully intact, but right at the X pipe (well after the CAT), run two exhaust cutouts that allow the exhaust to bypass completely the stock hardware. My confusion was generated from the ability to "remove" any component. With a cutout half engaged, half the exhaust has the potential to exit from the stock location.
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The performance gain would be negligible for autox, So I would just run it closed for events which should definitely be legal and enjoy it open the rest of the time. I thought S2000 guys used to just disconnect their catbacks all together.
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I always say build the car you want to drive every day, and worry about the RAW scores if that matters to you. Unless you're holding the top of your class or top times of the day, it just doesn't make sense to try mods that conform to the rules IMO.
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The performance gain would be negligible for autox, So I would just run it closed for events which should definitely be legal and enjoy it open the rest of the time. I thought S2000 guys used to just disconnect their catbacks all together.
There's not a lot I can do to squeeze more power out of the car.
In BS I can't use underdrive pully's, or replace headers. The exhaust mod is about the only power adding mod allowed.
I always say build the car you want to drive every day, and worry about the RAW scores if that matters to you. Unless you're holding the top of your class or top times of the day, it just doesn't make sense to try mods that conform to the rules IMO.
Eventually I'll be building her for BSP, where I can have the aero, pully's, headers.....
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The performance gain would be negligible for autox, So I would just run it closed for events which should definitely be legal and enjoy it open the rest of the time. I thought S2000 guys used to just disconnect their catbacks all together.
To meet rules, you need at least a straight pipe to guide the bypassed exhaust to one of the original openings. And you will certainly need a muffler on this straight pipe to meet sound.
BTW, it is illegal (and extremely unsafe) in any class to have exhaust released underneath the car. You wouldn't pass tech if you tried that.
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Eventually I'll be building her for BSP, where I can have the aero, pully's, headers.....
BSP does not allow wings, just spoilers without endplates. To get a wing, you need to move up to SM.
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BTW, it is illegal (and extremely unsafe) in any class to have exhaust released underneath the car. You wouldn't pass tech if you tried that.
There are a few classes that do allow this but they generally are ones that are a dumping ground for roadcourse cars. For example Spec Miata's can terminate at the rear axle, then again we cannot run with windows legally so it does help to minimize the safety concern.
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The performance gain would be negligible for autox, So I would just run it closed for events which should definitely be legal and enjoy it open the rest of the time. I thought S2000 guys used to just disconnect their catbacks all together.
To meet rules, you need at least a straight pipe to guide the bypassed exhaust to one of the original openings. And you will certainly need a muffler on this straight pipe to meet sound.
BTW, it is illegal (and extremely unsafe) in any class to have exhaust released underneath the car. You wouldn't pass tech if you tried that.
Deuce! and Double Deuce!! Time to erase that idea and start coming up with others.
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Eventually I'll be building her for BSP, where I can have the aero, pully's, headers.....
BSP does not allow wings, just spoilers without endplates. To get a wing, you need to move up to SM.
Hmmm SM does give me a reason to get that supercharger I've been pining for.
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As I've learned after the fact like many before me...Street prepared/Street Mod are the cut your fender for stupid wide tires class that tricks people into thinking it is the add power to my car class. It takes a very high level of car preparedness to hope to pax well in those and higher classes.
Tires first, then power unless your going to ignore pax like me and then I'd say add all the power you can and have fun!
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As I've learned after the fact like many before me...Street prepared/Street Mod are the cut your fender for stupid wide tires class that tricks people into thinking it is the add power to my car class. It takes a very high level of car preparedness to hope to pax well in those and higher classes.
Tires first, then power unless your going to ignore pax like me and then I'd say add all the power you can and have fun!
I've made that mistake before on the 135 and ended up in STU for wheels only. I've done alright in SM with a Subaru way back when as well, but that one I just blindly wandered into a class without thought.
My goal with this car will be gradual mods and likely an eventual settling in SM, by way of BS and BSP. Next year I'd like to compete in BS and put at least a full year to that class.
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Street prepared/Street Mod are the cut your fender for stupid wide tires class...
Some of us can fit 10.5" wide wheels without cutting fenders. ;D
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My 2 cents worth would be, keep it stock and fix the nut behind the wheel. RE71 R, sway bar and a set of konis will transform the car and still run in BS
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My 2 cents worth would be, keep it stock and fix the nut behind the wheel. RE71 R, sway bar and a set of konis will transform the car and still run in BS
The flabby bit behind the wheel is always the biggest factor. I'm sure if I gave the car to Ryan, Cam... or any others on that side of the leaderboard, I'd see very different results.
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That is also the challenge for the rest of us. As for me I shan't be doing any mods to my Mazda that takes me out of C street.
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A good set of brake pads can really help as well. I'm not sure what the best pads for a Z4M are but carbotech or hawk hp plus pads seem to be the most popular in autocross on other cars. They cause a lot of heat so having a high temp brake fluid will help keep your brake pedal firm and consistent as well. It never hurts to search for other forums on the internet to find out how guys are setting these cars up south of the border. There is a good chance that someone has already done the homework for this car and has a good base line set up to begin with.
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Just thinking about the SM comments, I think the Z4M would fall into SSM. What's better than being in a Super class?
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A good set of brake pads can really help as well. I'm not sure what the best pads for a Z4M are but carbotech or hawk hp plus pads seem to be the most popular in autocross on other cars. They cause a lot of heat so having a high temp brake fluid will help keep your brake pedal firm and consistent as well. It never hurts to search for other forums on the internet to find out how guys are setting these cars up south of the border. There is a good chance that someone has already done the homework for this car and has a good base line set up to begin with.
Brakes are one of the first things on my list. The braking was a bit weak these last couple events.
There is so much info available on these cars it's tough to sort through it all really.
My current list to stay in class, likely in order of appearance;
New tires and wheels
New brake pads and fluid
Alignment
Cat back exhaust (resonator delete)
Front sway bar
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Just thinking about the SM comments, I think the Z4M would fall into SSM. What's better than being in a Super class?
So it's omitted from Touring and Street Modified. Geeze!!
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SM - sedans/4-seaters.
SSM - 2-seaters ...
And, yes, some cars do not have a place in Street Touring, although the Z (corrected) is allowed in STR ....and let's not forget BSP,
R
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Look in here:
http://cdn.growassets.net/user_files/scca/downloads/000/017/206/2016-8-23_Appendix_A.pdf?1471970139
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Brakes are one of the first things on my list. The braking was a bit weak these last couple events.
The braking issue was most likely your rubber. Get better tires and you might be amazed at how good your brakes are working. I run a ceramic pad for cold performance (first run) and sharper initial bite than the OEM, but there isn't any more maximum braking available compared to the OEM pads. I run OEM brake fluid, and have yet to experience any fade or softness at autox, even with two drivers.
My current list to stay in class, likely in order of appearance;
New tires and wheels
New brake pads and fluid
Alignment
Cat back exhaust (resonator delete)
Front sway bar
I would argue that your best path would be this order:
Tires + alignment (this will be your biggest gain)
Brake pads
Sway bar
Adjustable shocks (to help with some of the handling issues usually caused by the sway bar)
Wheels (mostly for diameter change if it is helpful for your car) (don't forget about the rules WRT wheel size and offset)
Exhaust
Be careful with the exhaust change; you may end up with a car that is mostly undriveable on the street. Or one that exceeds the sound limits. And it will probably give you the least improvement of the entire suite of changes.
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SM - sedans/4-seaters.
SSM - 2-seaters ...
And, yes, some cars do not have a place in Street Touring, although the Z (corrected) is allowed in STR ....and let's not forget BSP,
R
Unfortunately he has the Z4M, so is excluded from STR.
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Ah, I did not realize that......the M is classed differently.
Have to watch those high perf. models ... just like the S2000CR is in AS instead of BS like the rest of the S2000's ...
R
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Firstly, thanks everyone for the help. Damn fine community we have here. :D
SM - sedans/4-seaters.
SSM - 2-seaters ...
And, yes, some cars do not have a place in Street Touring, although the Z (corrected) is allowed in STR ....and let's not forget BSP,
R
That all makes sense. I don't have a hope in hell of competeing in SSM on my budget. Lol I think I'll avoid that class.
Brakes are one of the first things on my list. The braking was a bit weak these last couple events.
The braking issue was most likely your rubber. Get better tires and you might be amazed at how good your brakes are working. I run a ceramic pad for cold performance (first run) and sharper initial bite than the OEM, but there isn't any more maximum braking available compared to the OEM pads. I run OEM brake fluid, and have yet to experience any fade or softness at autox, even with two drivers.
My current list to stay in class, likely in order of appearance;
New tires and wheels
New brake pads and fluid
Alignment
Cat back exhaust (resonator delete)
Front sway bar
I would argue that your best path would be this order:
Tires + alignment (this will be your biggest gain)
Brake pads
Sway bar
Adjustable shocks (to help with some of the handling issues usually caused by the sway bar)
Wheels (mostly for diameter change if it is helpful for your car) (don't forget about the rules WRT wheel size and offset)
Exhaust
Be careful with the exhaust change; you may end up with a car that is mostly undriveable on the street. Or one that exceeds the sound limits. And it will probably give you the least improvement of the entire suite of changes.
I plan on 18's for next season, which were an option for the Z4M. The tires will have to wait until then as well. I should have actually placed the tires and wheels last on the list I posted before. My bad. Unlimited budget and the wheel tire upgrade would already be done.
Quick clarification. As I understand it, converting to studs is not allowed, but longer bolts are if required to compensate to stock offset. Is that correct?
I wanted to take care of the little things before then though brakes, alignment, exhaust for a few extra HP, and the sway.
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Something to keep in mind: If you go to larger diameter wheels, you may be increasing your unsprung weight which may not be an increase in performance ... more weight, spinning mass = less acceleration and less braking, also they may be taller which can affect your gearing. Even the weight of the tire will be more.
For autox you might be better off with a smaller diameter wheel if you can get the width of rubber you want and the wheels fit around the brakes ... and your gearing works out etc.
IN fact, I know of people downsizing brakes for autox to save unsprung weight (rule-of-thumb - save 4 lbs = 2x4 = 8 lbs equivalent of sprung weight) since you do not use the brakes very much ... we probably use them more than most due to the long airport runway at Fort Macleod.
Lots to think about there.
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Certainly good food for thought there Reijo. In my case though, I'll be looking to step down to 18's from the 19's that are on there currently. I like a little more sidewall and feedback from the tires.
I'm looking at a set that are lighter than what's on there currently, stock widths ( I was looking for an extra .5 inch width, but they aren't available in that size), and only a few mm difference in offset.
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fyi, I used Hawk HP+ pads on the S2000 and they dust but they were vastly superior in initial bite compared to the stock pads ... very worthwhile. I have stock pads back in and the brakes do not quite feel the same anymore even though the S2000 was noted for having excellent stock brakes. :)
Of course, if you use the car for track days as well, then you will have to change set-up etc. etc. if you want to be competitive ... or run some compromise set-up etc.
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Certainly good food for thought there Reijo. In my case though, I'll be looking to step down to 18's from the 19's that are on there currently. I like a little more sidewall and feedback from the tires.
I'm looking at a set that are lighter than what's on there currently, stock widths ( I was looking for an extra .5 inch width, but they aren't available in that size), and only a few mm difference in offset.
Ah, so you are going in a good direction ... and smaller dia. wheels/tires are cheaper too. :)
You are allowed up to 1/4" (6.35 mm) leeway for offset as per the rules.
R
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As I interpret the rules, spacers are allowed and counted as part of the wheel to ensure stock offset.
I'd love to go to studs though for ease of wheel changes. I know longer bolts are allowed to allow spacers, but a stud conversion is not a Street allowable mod.
May I just add... get with the times German cars!! Use studs. Wheel bolts are a pain... especially with spacers!!
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As I interpret the rules, spacers are allowed and counted as part of the wheel to ensure stock offset.
I'd love to go to studs though for ease of wheel changes. I know longer bolts are allowed to allow spacers, but a stud conversion is not a Street allowable mod.
May I just add... get with the times German cars!! Use studs. Wheel bolts are a pain... especially with spacers!!
Yeah.... sometimes the rules can be a pain and there may be no gain (studs = bolts weight-wise) ... You could actually write a letter to that effect to the BOD and see if are willing to allow that. I think that would be a reasonable request and you never know.
Reijo
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Lots of people giving setup advice here, but I'm going to pull rank since I ran an E46 M3 nationally for a season in 2014. :) They're obviously different cars, but the Z4M's platform was derived from the E46 M3's and should have similar setup needs.
The M3's Achilles heel is understeer due to its skinny front wheels and a lack of front camber, and I can't imagine the Z4M's any different. Given that, I'd start off with just tires and an alignment. RE-71Rs are a significant improvement on almost any other street tire and should help your times a lot. For the alignment, max out your front camber (making sure that you remove the strut top pins first), set the front toe to around zero, and set the rear toe to zero or a hair of toe-in in.
Struts are probably a good idea since, if you're still on the stock shocks, they're almost definitely worn out by now. Unfortunately, it doesn't look like Koni has an off-the-shelf shock for the Z4M, and I know from firsthand experience that Bilsteins raise the car's ride height significantly due to their gas pressure. Not really any good options there without spending big bucks -- it might be worth your while to research if it's feasible to modify M3 struts to work on your car.
Get wheels if you really want them, but they're not going to make a significant difference in your times.
Last but not least is the sway bar. Everyone I know who ran an E46 M3 (myself included) got a stiffer aftermarket front bar, then ended up running it on full soft because the car would push too much otherwise. Given that, if I were you, after making the changes above I'd run the car with the stock bars and only get a bigger bar if needed to address balance issues. I'd even consider a bigger rear bar.
You are allowed up to 1/4" (6.35 mm) leeway for offset as per the rules.
Actually, last year the allowance was increased to 7 mm.
I'd love to go to studs though for ease of wheel changes. I know longer bolts are allowed to allow spacers, but a stud conversion is not a Street allowable mod.
Stud conversions are actually legal in Street and quite common on German cars. Alternately, you can buy a couple of wheel pin / hanger tools like this one (https://www.turnermotorsport.com/p-376087-wheel-hanger-m12x15-thread/) -- they make changing wheels easier, although not as easy as a stud conversion.
Last but not least, check out the E46 setup thread on M3Forum (http://www.m3forum.net/m3forum/showthread.php?t=458429) if you haven't already.
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Here's where you can request a rule change:
https://www.crbscca.com/
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I stand corrected. Thanks Stephen! Good info.
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Here's the wheel offset rule:
13.4 WHEELS
Any type wheel may be used provided it complies with the following:
A. It is the same width as standard and as installed it does not have an offset
more than ±7.00 mm (±0.275”) from a standard wheel for the car. The
resultant change in track dimensions is allowed.
Interestingly, I went looking for the stud conversion rule and didn't find anything relevant. I've personally seen countless cars at national-level events that have done it in Street (nee Stock), so I know it's a commonly accepted modification, but the rule could use clarifying -- as I read the rule book, a strict interpretation could indeed hold that a stud conversion was illegal. I'll write a letter.
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Interestingly, I went looking for the stud conversion rule and didn't find anything relevant. I've personally seen countless cars at national-level events that have done it in Street (nee Stock), so I know it's a commonly accepted modification, but the rule could use clarifying -- as I read the rule book, a strict interpretation could indeed hold that a stud conversion was illegal. I'll write a letter.
That is interesting - I had the same recollection as you.
All I can find in the Street rules is this:
13.4 WHEELS
~~~~Wheel studs, lug nuts, valve stems (including pressure-relief types), and/or
bolt length may be changed. ~~~~
That could be interpreted to mean it's ok, but in the Street Prepared rules the conversion is explicitly mentioned. I would take that to mean it's not "Street" legal . Looks like the street allowance is only to change wheel nuts or bolts, but not to convert bolts to wheel studs/nuts.
From Street Prepared
15.4 WHEELS
B. ~~~~ Wheel bolts may be replaced with
studs and nuts.~~~~~
As a BMW owner who regularly curses wheel bolts I would say it's definitely a comfort and convenience (and sanity) upgrade.
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13.4 WHEELS
~~~~Wheel studs, lug nuts, valve stems (including pressure-relief types), and/or
bolt length may be changed. ~~~~
That could be interpreted to mean it's ok, but in the Street Prepared rules the conversion is explicitly mentioned. I would take that to mean it's not "Street" legal . Looks like the street allowance is only to change wheel nuts or bolts, but not to convert bolts to wheel studs/nuts.
From Street Prepared
15.4 WHEELS
B. ~~~~ Wheel bolts may be replaced with
studs and nuts.~~~~~
As a BMW owner who regularly curses wheel bolts I would say it's definitely a comfort and convenience (and sanity) upgrade.
All of this pointed me to the thought that converting from bolts to studs was not allowed in Street classes. Although I will say that when using spacers, there is no better reason to move to BSP. I almost don't care if no other prep is made for that class.
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We're a bit friendlier here, but if I were still in the States, I'd advise you to convert to studs, run in Street anyway, and punch anyone who complained in the nuts. :p
As Brian posted, in a formal protest you could very reasonably argue comfort and convenience, especially since (as I understand it) the reason German automakers use bolts rather than studs is to save weight.
I wrote a letter, but it'll be a few months before a response is printed in Fastrack.
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We're a bit friendlier here, but if I were still in the States, I'd advise you to convert to studs, run in Street anyway, and punch anyone who complained in the nuts. :p
As Brian posted, in a formal protest you could very reasonably argue comfort and convenience, especially since (as I understand it) the reason German automakers use bolts rather than studs is to save weight.
I wrote a letter, but it'll be a few months before a response is printed in Fastrack.
I'd like to stay within the letter of the law, but the bolts are a significant pain.
By "wrote a letter", what do you mean? Are you a contact from us to the powers that be in the SCCA?
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Anyone can write a letter to the Solo Events Board (SEB) ... inquiring about rules, suggestions for rule changes and new rules etc.
Of course it does not mean they will respond favourably to you! :) They evaluate every letter that comes in ... btw, see the link I posted somewhere above about writing a letter .... that is how you do it.
R
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I'd like to stay within the letter of the law
The point that Brian and I are making is that the letter of the law is ambiguous. I'd be comfortable making this change under the comfort and convenience allowance in 13.1, which reads:
comfort and convenience modifications which have no effect on performance and/or handling and do not materially reduce the weight of the car are permitted.
Do studs affect performance or handling? No. Do they materially reduce the weight of the car? No. I think you can therefore reasonably claim them under comfort and convenience. But hopefully the SAC / SEB clarify the rule anyway.
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Awesome. I think I'll move forward with the change then.
Thanks again for all the input! Hopefully this thread will help more in the Street classes. Great community here!!
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I wrote a letter, but it'll be a few months before a response is printed in Fastrack.
This month's Fastrack contains a response to my letter -- replacing bolts with studs is now explicitly legal in Street:
Tech Bulletins
#20399 Clarify wording on converting wheel bolts to studs
Per the SAC, add as follows to section 13.4:
“Wheel studs, lug nuts, valve stems (including pressure-relief types), and/or bolt length may be changed. Wheel
bolts may be replaced with studs and nuts but the number of fasteners may not be changed.”