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Al Fernandez
07-29-2008, 10:25 AM
Guys
I posted on the CMC national site two updates on rules, one regarding radiator air deflector length (to help with cooling) and another on wording to eliminate potential conflict regarding engine configurations. Please head over there and take a look.

Al Fernandez
08-07-2008, 07:28 AM
Another CMC update...compression this time. Please check the national CMC site.

RichardP
08-07-2008, 09:54 AM
one regarding radiator air deflector length (to help with cooling)


Similar to the AI ride height rule where the details aren't spelled out...

Is this new measurement to be taken with or without the driver?


Richard P.

Al Fernandez
08-07-2008, 10:36 AM
I would measure with driver, but you have a good point that we should specify.

Waco Racer
08-07-2008, 11:35 AM
When during the event are you going to want it checked? Please, consider this when deciding if the driver is in or out of the car.

Al Fernandez
08-07-2008, 11:40 AM
Typically this would be checked post weighing in, so the driver is available.

mitchntx
08-07-2008, 12:37 PM
Typically this would be checked post weighing in, so the driver is available.

Speaking of "weighing in" ...

Post qual 1 me and car weighed 3373
Post race 1 me and car weighed 3384

I added no fuel, no ice, nothing ...

michaelmosty
08-07-2008, 12:56 PM
My weighing was a little odd as well.
Weighed before R3 at 3174. Added roughly 2 gallons of gas to shoot for 3190. Came off track at 3183.

AI#97
08-07-2008, 01:09 PM
Typically this would be checked post weighing in, so the driver is available.

Speaking of "weighing in" ...

Post qual 1 me and car weighed 3373
Post race 1 me and car weighed 3384

I added no fuel, no ice, nothing ...

I noticed a similar inconsistancy at Hallett. Ran qual..didn't weigh. Ran race weighed 3230...unusually high for me especially post race... added 5 gallons and raced R2...usually burn 6 gallons per race, came off 324X...

I think the NASA tech scales need to be sent in for calibration/rebuild after all these years of abuse! I am sort of in la la land regarding weight of the car before nats as I have no idea what is accurate. Considering I would come off the scales at Houston at 3154 and 3170, that tells me that either I personally have put on 60lbs (actually lost 15) or the scales need some attention. Take into account I am running a wheel package that is 16-20lbs lighter...and the delta grows even more.

I realize we never get perfectly lined up on the pads and that can affect things but before I go nuts with a plasma cutter and cut 80lbs out of the car mistakenly, it would be cool if NASA could give some attention to the scales.

I would also like to know how we can suggest they get Johnathon some help in tech... not that he isn't competant, but having just one guy there really puts a toll on him by the end of the weekend and he can get overwhelmed with questions and general exhaustion doing so much all by himself in tech!...

AllZWay
08-07-2008, 01:24 PM
Michael and I were talking about the weigh in problems also.

Wirtz
08-07-2008, 01:34 PM
I might be able to get some good data to look at from TWS. I measure my fuel load before and after each session. I need to look at my race notes to check.

Jeff

jeffburch
08-07-2008, 01:37 PM
Those scales have suffered this since they bought them.
I don't think they are linear with temperture (shade vs. sunlight).

jb

Waco Racer
08-07-2008, 01:43 PM
Typically this would be checked post weighing in, so the driver is available.

Available is not the issue. Pre-race or Post-race? I'm not for putting them back into a hot car on a hot day or checking this during the weighing process.

NASA Texas is aware that the scales need to be checked. NASA Texas also needs to improve their system of setting up the scales. They need to measure and check squareness of the pads. However, my suggestions aren't always followed.

RichardP
08-07-2008, 01:43 PM
I am sort of in la la land regarding weight of the car before nats as I have no idea what is accurate.

I realize we never get perfectly lined up on the pads and that can affect things but before I go nuts with a plasma cutter and cut 80lbs out of the car mistakenly, it would be cool if NASA could give some attention to the scales.

Why do you care what NASA TX scales read if you are going to Nationals? They use different scales there.

This has been mentioned before. Accuracy is irrelevant. Consistency is important. I suggest you weigh yourself at Nationals and have a plan for adding ballast to the "correct weight" if you want to play the game close. Add "a little" margin in for the inevitable inconsistency of the scales.

The same concepts hold for the dyno that will be onsite at Nationals.

(Yes, it would be nice if the local scales were more consistent.)


I would also like to know how we can suggest they get Johnathon some help in tech...

Always a good plan...


Richard P.

rpoz27
08-07-2008, 02:37 PM
NASA Texas is aware that the scales need to be checked. NASA Texas also needs to improve their system of setting up the scales. They need to measure and check squareness of the pads. However, my suggestions aren't always followed.

Heard someone say something about having laser levels to check for squareness in future (after Jay had to be realigned every time he went across). Scales were set up like l/ rather than ll on Saturday.

Adam Ginsberg
08-07-2008, 03:53 PM
Why do you care what NASA TX scales read if you are going to Nationals? They use different scales there.

This has been mentioned before. Accuracy is irrelevant. Consistency is important. I suggest you weigh yourself at Nationals and have a plan for adding ballast to the "correct weight" if you want to play the game close. Add "a little" margin in for the inevitable inconsistency of the scales.

Richard, as usual, is spot on. Check the CCR's for the actual wording, but the gist is...."the scales at the event are the scales - period". The ones used at the Nat's are serious units, BTW.

Additionally, get on the dyno at the Nats right away, and be prepared.

AI#97
08-07-2008, 04:25 PM
Why do you care what NASA TX scales read if you are going to Nationals? They use different scales there.

This has been mentioned before. Accuracy is irrelevant. Consistency is important. I suggest you weigh yourself at Nationals and have a plan for adding ballast to the "correct weight" if you want to play the game close. Add "a little" margin in for the inevitable inconsistency of the scales.

The same concepts hold for the dyno that will be onsite at Nationals.

(Yes, it would be nice if the local scales were more consistent.)

Richard P.

I have a ton more faith in dynos being consistant from one to another not taking into account any figiting with the programming.

Scales however, could be VASTLY wrong. I know for a fact I have been taking weight out of the car for 2 years little by little, however, the weight continues to go UP! Strangest thing I have ever seen! Now, that being said, let's say that I think my car weighs 3180lbs with 100lbs of ballast in it based on the TX scales and the scales are so wrong, I actually weigh 3080lbs.... Now, I arrive at nationals and with the cold weather I make more power which I cannot adjust at the track... and suddenly have to add MORE than the allowable 150lbs of ballast? It would suck to have to buy a cool suit setup and bolt it in and a bunch of other crap to stay legal....right?!

I agree, you have to be ready to be legal per the dyno and scales on site at any event...however, if the window of accuracy with a potentially damaged set of scales is wide enough, you can only PLAN for so much delta. I guess I need to roll the car onto a known good set of scales to be sure, just trying to avoid having to incur costs to do so.

And for the record, from my record keeping from 3 years of rolling onto the TX scales and known weight removal efforts, I still contend they are reading 80-105 lbs heavy even with taking into account some allowable "inconsistancy".... Just data to ponder on.

AI#97
08-07-2008, 04:28 PM
[.."the scales at the event are the scales - period". The ones used at the Nat's are serious units, BTW.
.

Are they similar to the ones we have at TX events...? Mostly concerned about the height of them as I already have a problem getting onto them without moving them with the splitter... I may ping JWL so we can get an idea ahead of time....

jeffburch
08-07-2008, 05:05 PM
They contract out the scales.
Plateform style. Sectioned diamond plate steel deck.
Your street sweeper will clear easily.

jb

mitchntx
08-07-2008, 05:12 PM
Why do you care what NASA TX scales read if you are going to Nationals? They use different scales there.

This has been mentioned before. Accuracy is irrelevant. Consistency is important. I suggest you weigh yourself at Nationals and have a plan for adding ballast to the "correct weight" if you want to play the game close. Add "a little" margin in for the inevitable inconsistency of the scales.

Richard, as usual, is spot on. Check the CCR's for the actual wording, but the gist is...."the scales at the event are the scales - period". The ones used at the Nat's are serious units, BTW.

Additionally, get on the dyno at the Nats right away, and be prepared.

Not denying the wording in the CCR. But with 10-15lb swings in either direction from session to session, how is that fair?

The gist of Richard's post was the number doesn't matter. Richard probably won't refute that repeatability does.

Adam Ginsberg
08-07-2008, 05:25 PM
Not denying the wording in the CCR. But with 10-15lb swings in either direction from session to session, how is that fair?

Like it or not, the "scales are the scales". Fair has nothing to do with it. I won't deny the large swings in weight from session to session sucks. However, each competitor is responsible for making weight with the scales at the event - that's why it's so critical to weigh prior to getting out on track (yes, I'm aware NASA TX doesn't always have the scales set up in time...that's another issue).


The gist of Richard's post was the number doesn't matter. Richard probably won't refute that repeatability does.

IMO, the gist of RP's post was...it makes no difference what NASA TX's scales show @ TWS when MFW weighs his car @ the Nationals.

mitchntx
08-07-2008, 05:55 PM
Not denying the wording in the CCR. But with 10-15lb swings in either direction from session to session, how is that fair?

Like it or not, the "scales are the scales". Fair has nothing to do with it. I won't deny the large swings in weight from session to session sucks. However, each competitor is responsible for making weight with the scales at the event - that's why it's so critical to weigh prior to getting out on track (yes, I'm aware NASA TX doesn't always have the scales set up in time...that's another issue).


The gist of Richard's post was the number doesn't matter. Richard probably won't refute that repeatability does.

IMO, the gist of RP's post was...it makes no difference what NASA TX's scales show @ TWS when MFW weighs his car @ the Nationals.

So a car GAINING weight after an event wouldn't cause you some concern about the scale's repeatability?

You would DQ racer over being 5 lbs light after it's been shown the scales vary 10 lbs from session to session?

michaelmosty
08-07-2008, 05:59 PM
- that's why it's so critical to weigh prior to getting out on track (yes, I'm aware NASA TX doesn't always have the scales set up in time...that's another issue).


I actually weighed 25 minutes before our race and then again right after coming off track and the numbers seemed very "off".

I would be pretty upset if I knew I went out on track at 3195 and came in under 3150. This thankfully has never happened but with the fluctuations at TWS it would have made things interesting.
FWIW, I shoot for 3165 lbs.

marshall_mosty
08-07-2008, 09:37 PM
At the April TWS enduro, after taking a 3 gallon splash in the last 10 minutes of the race, I still came off track at 2760 with a full cool suit I didn't have in the car previously. That would put me at 2740 without the suit... that's just plain nuts. I'd say it was reading easily 40 lbs light in April.

Just a data point.

Adam Ginsberg
08-07-2008, 10:00 PM
Hell yes I'd be concerned. AAMOF, if I saw that happening, I'd be pushing for a reweigh, and/or completely resetting up the scales.

Frankly, we're barking up the wrong tree here - this information should be taken to NASA Texas in the proper manner. Granted, I wasn't there, but based on what you guys are saying, those scales need to be recalibrated.

mitchntx
08-07-2008, 10:15 PM
Hell yes I'd be concerned. AAMOF, if I saw that happening, I'd be pushing for a reweigh, and/or completely resetting up the scales.


A re-weigh could very easily swing 10-15lbs the other way and then be good to go? You serious?

And a reset invalidates everyone prior to that? So the racer before that was lucky enough to get the scales when they were reading high ... and that's is OK?

Oh yeah ...


Fair has nothing to do with it.


Crystal clear ... So, yes you would DQ over 5lbs knowing the scales were fubared.



Frankly, we're barking up the wrong tree here - this information should be taken to NASA Texas in the proper manner. Granted, I wasn't there, but based on what you guys are saying, those scales need to be recalibrated.

They stopped using them at Hallett for this very reason.

When I got my weight post race I ask the tech guy wearing glasses (sorry, don't know his name) as he was pushing me off the scales how the car gained weight during a race. He smiled and kept pushing.

How many times do we have to bark, sir?

I posted this as a racer wondering if it was an isolated case or not. It was the only convenient way to ask a question of the group. There was/is no agenda, just asking a question.

David Love AI27
08-07-2008, 10:49 PM
run AIX... no worries, be happy...

GlennCMC70
08-07-2008, 11:31 PM
i took this up w/ Shannon Sunday at the track. she is well aware there is a problem here.

AI#97
08-08-2008, 06:30 AM
run AIX... no worries, be happy...

aix still has a minimum weight and you can be dq'd for not showing up at the scales....ask david armstrong about that one!

Rsmith350
08-08-2008, 06:06 PM
Note** cars will be at least 10 lbs. heavier after lunch at TWS** Those were some good burgers. :lol:

David Love AI27
08-08-2008, 06:57 PM
run AIX... no worries, be happy...

aix still has a minimum weight and you can be dq'd for not showing up at the scales....ask david armstrong about that one!

Last check, 3380 leaves lots of room for error... LOL

Adam Ginsberg
08-09-2008, 08:34 AM
aix still has a minimum weight and you can be dq'd for not showing up at the scales....ask david armstrong about that one!

Only his qual time was tossed - he was not DQ'd for a race, IIRC.

RichardP
08-09-2008, 11:11 AM
Only his qual time was tossed


You mean he had to start from the back of the AIX field? Wow, that would be hard to recover from...


Richard P.

AI#97
08-10-2008, 12:05 PM
Only his qual time was tossed


You mean he had to start from the back of the AIX field? Wow, that would be hard to recover from...


Richard P.

He started at the back of the pack, same as JG and me....I had a mechanical and didn't cross the scales...

RichardP
08-11-2008, 02:17 PM
Boy has this thread been derailed. Lets try and get it back on topic.



Another CMC update...compression this time.


Is there any effort going to be made to make the compression checking tool available to competitors to check their cars and verify that it is in compliance? Other official tools (scales, dyno, etc.) are availble ahead of time for verification.


Richard P.

Al Fernandez
08-12-2008, 09:18 AM
Great question. Todd, any input?

RichardP
08-15-2008, 02:48 PM
When critical measurements are taken to determine the legality of a car, I think it is important to understand the underlying principles behind the measurement and to have a good handle on its potential sources of error.

Looking into the details of the Whistler compression ratio checker I see that it doesn’t actually measure the compression ratio. It effectively uses sound waves to measure the cylinder volume when the piston is at top dead center. It then calculates the compression ratio using the displacement input into the machine. If the displacement is incorrect, so will the measured compression ratio. Not knowing the effective temperature of the cylinder or not accurately getting the cylinder to top dead center will also cause measurement errors.

The displacement input is interesting to me. Without testing, the operator doesn’t know the displacement of the motor. For example, Fox Mustangs have a base displacement of 302 cubic inches but are allowed to overbore during a rebuild which increases displacement.

Using the formulas for displacement, I found that a 10:1 302 cubic inch motor has a cylinder volume at top dead center of 4.189 cubic inches. If the Whistler measures that volume and you input a displacement of 302, 10:1 is the compression ratio the machine will kick out.

More interesting is the calculations when the displacement is a little off. If you have bored your 302 “60 over” but still have the same cylinder volume at top dead center your real compression ratio will be about 10.3. If you don’t tell the inspector this and he types 302 into the machine, a compliant 10:1 will still pop out of the machine.

If you go deep into the cheater realm and show up with a 331 under the hood, you can effectively have up to about a 10.9:1 compression ratio before the tech inspector shows you to be out of compliance when a 302 displacement is input.

So, the key here is for people with over bored motors to tell the inspector that they have a stock bore to get a little margin on the compression test.

Similarly, if you have a full cheater stroker motor, you really need to scale up the compression ratio appropriately so it’s not so obvious if you get your compression checked… :roll:


Does NASA have the tools to check displacement? Is it going to be a part of tech inspections at Nationals? I think it should be.


Richard P.

AI#97
08-15-2008, 04:20 PM
When critical measurements are taken to determine the legality of a car, I think it is important to understand the underlying principles behind the measurement and to have a good handle on its potential sources of error.

Looking into the details of the Whistler compression ratio checker I see that it doesn’t actually measure the compression ratio. It effectively uses sound waves to measure the cylinder volume when the piston is at top dead center. It then calculates the compression ratio using the displacement input into the machine. If the displacement is incorrect, so will the measured compression ratio. Not knowing the effective temperature of the cylinder or not accurately getting the cylinder to top dead center will also cause measurement errors.

The displacement input is interesting to me. Without testing, the operator doesn’t know the displacement of the motor. For example, Fox Mustangs have a base displacement of 302 cubic inches but are allowed to overbore during a rebuild which increases displacement.

Using the formulas for displacement, I found that a 10:1 302 cubic inch motor has a cylinder volume at top dead center of 4.189 cubic inches. If the Whistler measures that volume and you input a displacement of 302, 10:1 is the compression ratio the machine will kick out.

More interesting is the calculations when the displacement is a little off. If you have bored your 302 “60 over” but still have the same cylinder volume at top dead center your real compression ratio will be about 10.3. If you don’t tell the inspector this and he types 302 into the machine, a compliant 10:1 will still pop out of the machine.

If you go deep into the cheater realm and show up with a 331 under the hood, you can effectively have up to about a 10.9:1 compression ratio before the tech inspector shows you to be out of compliance when a 302 displacement is input.

So, the key here is for people with over bored motors to tell the inspector that they have a stock bore to get a little margin on the compression test.

Similarly, if you have a full cheater stroker motor, you really need to scale up the compression ratio appropriately so it’s not so obvious if you get your compression checked… :roll:


Does NASA have the tools to check displacement? Is it going to be a part of tech inspections at Nationals? I think it should be.


Richard P.

Great info RP! To throw an even bigger "cheater" wrench into the mix...the whistler essentially checks the dynamic compression ratio based on the camshaft timing. If you have a camshaft that has a different LSA (another cheating element), the static compression ratio and the dynamic compression ratio are VASTLY different. My cam for example is on a 108 LSA and the intake valve doesn't close until the piston is significantly on it's way up in the bore. Therefore, my 12:1 motor really only sees a 10.2:1 dynamic CR. If I were to install an off the shelf Comp cam with similar durations and lift with an 113 LSA, I would gain back nearly a full point in dynamic compression ratio. Also about 15-25 hp with timing and 100 octane gas.

I think the whistler is a good step forward for checking but as you seem to point out, has it's flaws.

RichardP
08-15-2008, 06:15 PM
Great info RP! To throw an even bigger "cheater" wrench into the mix...the whistler essentially checks the dynamic compression ratio based on the camshaft timing.


That's not how the whistler works. It is a static measurement taken at top dead center with all the valves closed. It uses sound waves to measure the chamber volume. Given the right parameters, it will measure the static compression ratio.

A "compression tester" that screws into the spark plug hole and gathers a reading in pounds per square inch (PSI) while you turn the engine over would be an example of a dynamic compression test. The value you would get from it depends on all the factors you mentioned.

There is no realistic way to correlate the two measurements, although I have seen charts that attempt to do this.


Richard P.

donovan
08-15-2008, 06:27 PM
my head hurts...

:lol:

King Matt
08-18-2008, 12:07 PM
Excellent analysis of the Whistler, Richard. The only thing I would add is that the use of an engine displacement pump would accurately measure the displacement of the engine so that variable is not left up to chance. I beleive that tech at Nationals has access to one and it should SOP to use both when testing CR.

AI#97
08-18-2008, 12:14 PM
That's not how the whistler works. It is a static measurement taken at top dead center with all the valves closed. It uses sound waves to measure the chamber volume. Given the right parameters, it will measure the static compression ratio.

Richard P.

Woah! Sounds a lot more complicated than I was lead to believe! I think i am going to get David and I some tylenol....extra strength!