77 replies to this topic

[Strongbad]

Alberto

I am missing the logic train on the argument you are putting forth. I don't see how any of your four bullet points affect the question at hand (allowing overboring)

A sealed Spec Miata engine is a completely different consideration, and one that I beleive we should seriously be considering before the cost of the arms war destroys the popularity of the class.

Just my $0.02

Not that long ago (2months) Mazdaspeed was selling sealed MX-5 engines for $4500! I bet those will last (read:competitive) for a couple of seasons. Maybe we should stsrt thinking longer term?

Joseph

[Jim Drago]

That makes complete sense. By the same token, I'd like to have a better feel for whether there is a performance DISadvantage due to the weight penalty.

Are 0.010-over pistons the exact same weight as standard? Logic tells me they would be 0.6% heavier since they fit a hole 0.6% bigger. If that's true, how much of the gain in displacement is offset by losses in reciprocating mass?

Granted, the estimated 0.77 hp gain is well within the 'noise' but it will become the standard for the pointy end. The flip side, IMHO, is if we put a weight penalty on it to discourage that practice, it doesn't help the parity wars. Besides, what a nightmare for tech. 2 chassis, three displacements, five generations of ECU/engine combo... Then we have to have 2 different weights for each?

For simple minds like mine, this gets confusing!

All true...
I feel very comfortable saying that the gain is probably 1/2 HP or less in all versions... There would be likely be no measurable performance gain going .010 over with no weight penalty. But the " we have to build a new motor to the new spec to be competitive" and the probability of the overbore becoming the standard, along with more perceived costs... IMO would do far more damage than the good of allowing the .010 with no penalty. 10-20 lbs is only a "real" penalty to the top 10% ( being very generous as I have been 30-35lbs over all season) of the drivers in this class.


The overbore was intentionally put out with "ear marks" It is overbore and penalty, or likely no overbore at all. but all are welcome to send in their input in any fashion they like.

[dstevens]

Benjamin bunny? Who the f is that?

LOL, you have kids or grandkids?

I'll cop to ASSuming it was a test instead of reading what he wrote. Fully my fault. That said, if that is just a calc I wonder how much of it will really make it to the rear wheels.

[Rob Burgoon]

It is overbore and penalty, or likely no overbore at all.

Thank goodness for that!

Could always add plans to ditch the penalty in 2014 or something if the goal is to have us all on overbore rebuilds at the pointy end eventually.

[Jim Drago]

Thank goodness for that!

Could always add plans to ditch the penalty in 2014 or something if the goal is to have us all on overbore rebuilds at the pointy end eventually.

That is "my opinion" as well, if it gets to where there are significant number of overbores in the field, the fear will die down about potential gains and becoming the standard, the weight penalty could always be dropped at a later date.

[Alberto]

Alberto...

I'll give the reasoning behind it if I can under each of your bullets.

My reasons:

1. I can get a 1.6 for $500 off craigslist or a JDM importer (Atarco for example).

What do you do when the bore on your supposed 30k Japanese engine or salvage or street car engine that you just bought for $500.00 is too large for a decent rebuild That is the case in 75% of all the 1.6 blocks over 100k. I would bet 95% are over 100k at this point, despite what they "say" they are. get a car fax and match vin plate on oil pan and see for yourself.

2. I have seen absolutely no evidence of lack of 1.6 motors or parts. Prove it if you can.

Ask most of the engine builders, I know we see as many Miatas, probably more than anyone in the country and rarely do we get 1.6 engines in less than 125k. The problem is not as bad i the 1.8 or 99's, but it is absolutely problem with the oldest cars that happen to be 1.6's

3. $3,500 for a crate motor ain't bad and I'm sure the quality is excellent. In my brief time in SM, I've seen and read of more than a few "PRO" motors blow up w/ not much use.

Do a little research on crate motors, you will find many of them blow up as well. All these engines can and will blow up, we stress the heck out of them. More often than not it is a tuning or assembly issue.

4. I suspect that building the motor would cost about as much as a crate motor. I remember reading ad nauseum on the old site about how building a motor was much more expensive than buying a crate.

It is.


If they want to make engine rules changes, they should switch to a spec sealed engine package like other spec series IMO. IT is a builder's class. SM is a Spec class.

Sm is spec, not sealed. take a look at the SF thread on sealed engines from a month ago where one car had like 8-10 hp on the field and no one knew how or why. In a sealed engine class ( which the ship has long sailed in SM by the way) Those who prep cars will have the same advantage or more IMO. This has been discussed for years as well


Jim

Jim,

I appreciate your comments and insight.

A few more points and counterpoints:

1. I will accept the fact that most of the unrebuilt, non-crate motors have 100k+ miles on them and could show some hone wear and that this wear could cause the block to be un-usable. However, there are plenty of competitive, high mileage, un-opened motors out there making good power. A fellow competitor dyon'ed 115 HP on his 100K mile motor yesterday. My 89k mile motor feels strong as well.

2. If one does need to get a new motor, why not just get a crate at that point? They are $3,100 from Mazda Motorsports (just got off the phone w/ Scott). Why would having one of the vendors overbore an old motor be better than an all new motor? Especially given the past conversations on how expensive it is to rebuild a motor vs. a crate.

Regarding longevity/reliability, My research on crate motors is that they last longer than Pro motors. My past experience racing karts and speaking with people in SM that have Pro motors says that Pro motors don't last as long as crate motors. If the price is the same and longevity of a crate is better, and all the brain trust on the old forum say to get a crate instead of rebuilding, then I don't understand how all that changed...


Regarding Spec series, the Spec series that I've raced in the past all had sealed motors from a few pre-approved vendors. Heck, SCCA's Spec Racer Ford has one source for their motors and they are all sealed and SPEC. "Formula", Production and Improved classes are the ones that usually have race built engines w/ overbores and head work and such - not a Spec class. I wish they had done that from the start in this series.


By the way, I'm really NOT trying to be argumentative. I just don't understand the benefits.

[Tom Sager]

I'm all for the rule if motors with standard bores can run at a slightly higher CR ratio. You can have one (over bore or over CR) but not both.

[Ron Alan]

Ron
How do you enforce over bores now? How about illegal rings? pistons? illegal valves and valve jobs? lightened cranks? There are a lot cheaper and easier ways to cheat if that is someones motive. There is a rule, if you break it you are illegal, At most races it will NEVER be checked. So why not just go .040 over and 11:1 if that is the mentality? I still believe that MOST want to abide by the rules, push them maybe, but not cheat. Running the overbore without the weight is intentionally cheating!


As for being a 1.6 only. This is primarily to benefit the 1.6 owners, eventually the 1.8 cars as well. But if it were a 1.6 only change, it would be perceived as a comp adjustment WHICH IT IS NOT and the 100 flaming posts would read, Why does the 1.6 guy always have to spend the money, why not just put a restrictor plate on the other cars. How it was presented was well thought out before putting it out for input.
We wanted to insure their was no performance advantage,no implied necessity to change, no way it could be interpreted as a comp adjustment and lastly it was a way to contain costs.
Jim

My post was tongue and check for entertainment purposes...but explaining how and why it is being presented is helpful, thanks Jim.

Most rules have to boil down to the honor system, and as you correctly state most want to be within the rules. If a penelty has to be assoc. with a fractional gain then I guess that's the way it has to be...enforceable or not

BTW...our car was randomly selected(along with 3 others) to be whistled this weekend at the SFR Thunderhill regional. Glad to say 3 passed while the fourth I'm not sure...as the driver I believe had to go run another class and the car disappeared while ours was being done.

[Rob Burgoon]

...enforceable or not

It is enforceable. Look out, here comes algebra.

If the spec bore is X and the bore tolerance in tech is +/- Y and the proposed overbore piston is Z, and Z is less than Y, then anyone can cheat and go overbore and probably get away with it right now since it's still in the tolerance.

However, their safety margin is now Y - Z instead of Z. If you want the full safety margin of Y, then you declare overbore pistons, take the 15 lbs and your bore has a maximum of X + Y + Z instead of X + Y - Z.

If Z is greater than Y, then if someone tears you down, you're busted for sure.

Clear? No more whining about it being "unenforcable" since if that is true, it's already tech shed legal and we're just legitimizing a cost saving "pro" practice. (nothing wrong with that)

[Ron Alan]

Clear? No more whining about it being "unenforcable" since if that is true, it's already tech shed legal and we're just legitimizing a cost saving "pro" practice. (nothing wrong with that)

LOL...very good! I should have originally chosen my words better...change can't to wont(Jim nailed it). Though i was being sarcastic his explaination for the weight penelty makes perfect sense. Here's some more math...

2450/130=18.85
2470/130.77=18.88

2275/123=18.49
2285/123.7=18.47

As low budget racers I welcome the idea of a cost savings. And it would appear the proposed thinking is equitable for the little guy and pointless for the deep pockets...my last 2 cents

[Johnny D]

So.... would it be, "if" you don't pass the whistle, you should weigh 2470(99)?
Or something more documented?
J~

[Jim Drago]

So.... would it be, "if" you don't pass the whistle, you should weigh 2470(99)?
Or something more documented?
J~

The whistler checks the compression, .25 mm over or not, the compression ratio must remain the same.
Jim

[William Keeling]

The whistler checks the compression, .25 mm over or not, the compression ratio must remain the same. Jim

I thought the engine size was a whistler variable -- that is why my overbore, high compression lump whistles low when measured at 1597CC

just kidding

[Johnny D]

The whistler checks the compression, .25 mm over or not, the compression ratio must remain the same.
Jim

So let me put it this way...
Are the cars going to be marked that there over?

Just last minute dotting I's and crossing T's stuff.
J~

[Jim Drago]

So let me put it this way...
Are the cars going to be marked that there over?

Just last minute dotting I's and crossing T's stuff.
J~

A rules change that is coming into effect 1/1/12 is ALL cars in ALL classes must post their weight on the side of the car. So it will be apparent who is claiming standard vs .010 over bore. We are our own best police officers.. If someone has standard weight on their door, I bet at least someone knows that is wrong and will call them on it. We know SM cars better than tech ever will.
Jim

[Johnny D]

Min weight.
So true.
J~

[Qik Nip]

A 10 thou bore is nothing. Let's say .77 hp. If you have it done just for performance sake, it's about US$800 if you do it send the block out and do the wrenching yourself with parts from the Zoom Zoom discount, about a grand if you have them do it all. For the sake of argument let's say $800. That's about a grand per hp for the mod. If guys want to spend that kind of dough for that small of a performance gain alone, let them. That 3/4 hp ain't why they are beating you. I'll take that grand and go get a good dyno tune from a pro shop or some seat time and tires or put it toward a pro head. A $1200 head is going to get you much more than 3/4 hp.

I just picked up my freshened motor last monday. Had this rule been in place, I would have absolutely added .77 HP for zero dollars. Adopting this rule means that every professionally built motor will be overbored. I'm okay with the rule change, but only with the added weight.
Rick
P.S. Anyone thinking 3/4 HP isn't material needs to think of that time when they were just "this" short of completing that long straightaway pass.

[Colin MacLean]

Guys FORGET that 0.77 number. Until someone dynos their car, bores it out .10 and re-dynos it we don't know anything. When I took my car from SM to ITA I took my ragged out motor and bored it out with .20 over pistons. $500 engine job plus rebuild parts. No headwork or anything. I added a header (2hp), intake (2hp) and that was it.

I then put my 1.6 car on OPM's (PFM) rototest dyno. It made 121/112. That was the same as a new 1.8 pro-motor on the same dyno right after me. Those 20 over pistons made a world of difference in area under the curve. They transformed the car. Don't think for one second that 0.10 pistons won't make a big difference. They will.

[Danny Steyn]

Colin

0.10 pistons will make a BIG difference. ...... 0.010 WONT

[dstevens]

At .10 we'd be seeing oil and water...

I don't have a sim to do a 4 banger, I should probably buy one. I'm not that familiar with the B6 yet but I do have a fair amount of experience poking around inside race lumps. One can't simply change one thing, in this case displacement and have it be a magic bullet. Even Jim is saying it's perhaps more like 1/2 hp. The rotating assembly is heavier, as Steve pointed out earlier, there is more surface friction and the static and dynamic CRs change as well. Someone is going to have to do some pulls for a real world comparison. If guys feel they need to spend it to be competitive knock yourselves out.