825 replies to this topic

[38bfast]

Best way is to have the car chemically striped and e-coated.

[Bench Racer]

Best way is to have the car chemically striped and e-coated.

Watch em Jason, some ^ are pushing your attempt at under $15 k build.

[speedengineer]

Best way is to have the car chemically striped and e-coated.

 

Watch em Jason, some ^ are pushing your. attempt at under $15 k build.

 

Don't worry, I won't fall for their tricks!

[speedengineer]

What is a typical amount of ballast an SM will need to run?  I weigh ~150lbs with gear.  Based on what my last car weighed and estimated difference in weight for going to SM parts, I'm guessing around 90 lbs of ballast to get to 2400lbs.  Does that sound about right?

[Bench Racer]

99 spec line weight @ 2400 pounds - 150 pound driver - 12 pounds gear -safety gas @ 7 pounds - cool suite case/water 19 pounds = 2212 pounds + weight of your razzel dazzle seat.

 

2212 + 90 = 2302 pounds suggests more beer and pizza required.

 

Do I see a stuff/weight data chart on the horizon?  

[speedengineer]

99 spec line weight @ 2400 pounds - 150 pound driver - 12 pounds gear -safety gas @ 7 pounds - cool suite case/water 19 pounds = 2212 pounds + weight of your razzel dazzle seat.

 

2212 + 90 = 2302 pounds suggests more beer and pizza required.

 

Do I see a stuff/weight data chart on the horizon?  

 

Well, my last car could weigh 2215 with me in it with no ballast and minimal fuel.

 

To convert, guessing on weights:

-switch to oem top, +30 lbs

-switch to oem header, +20 lbs

-add fire system, +10 lbs

-drop floor pan, seat back brace, seat, +15 lbs

-add back heater core and other stuff, +10 lbs

-add package tray, center roof cage bar, +6 lbs

-add evap system, +8 lbs

-oem flywheel, pp, +10 lbs

-remove air dam, undertray, and wing, -20 lbs

-add a radio system, +4 lbs

-SM dampers and bars heavier, +5 lbs

 

delta:  +97 lbs

So, 2313 lbs, so maybe 90 lbs of ballast?  That's without a cool suit though. 

 

Beer and pizza method might be cheaper than the cost of lead for ballast 

 

No time for chart making, have a race car to build!  I think I hear her calling my name right now.  Guess I have to go back to the garage...she's so needy.  Needs attention, time, and money constantly.

[Bench Racer]

  I think I hear her calling my name right now.  Guess I have to go back to the garage...she's so needy.  Needs attention, time, and money constantly.

That's the nice thing about a 4 wheeled significant other, provide all her needs and she'll never let you down.

[chris haldeman]

I weight 168 and run 135 pounds of ballast in my car.no fancy stuff in the car

[Bench Racer]

2100 pound 99 car, great job.  

[dstevens]

Using Jason's cost methodology since dipping the tub is taking things off the car it shouldn't count toward the build cost.  

 

Around here dipping is expensive.  A full size sedan with doors, hood, deck lid is just south of a couple grand, and that was a couple of years ago.  It's the way to do it, though.  I'm glad I didn't dip the 90.  It may not have come back with too much of the floor pan or lower rear quarters intact.

[speedengineer]

So these are out of the car.  Not really that much work to remove them, but cleaning and painting them will take a while...lots of nooks and crannies.  Hope it's worth the trouble.  The front one has so much grease and dirt caked on it that to clean it with cleaner/solvent and paper towels would be wasteful and take forever.  It's supposed to be unusually warm today here in MI, almost 50 degrees.  I  am planning to turn the exterior faucets back on and break out the pressure washer!

 

[speedengineer]

For just a bit, let's go back to the official SM compression ratio spreadsheet that the smac is working to get approved.  It's been mentioned that it is ideal if tech uses the pre-known piston dome volumes, and just has to measure the depth of the piston in the bore.  Is there a specified way to take that depth/deck height measurement in the instructions for the proposed CC spreadsheet? 

 

The reason I ask, is that the pistons actually can wiggle around quite a lot, would be very easy to take a measurement that is 0.005" off.  0.005" error here correlates to 0.1 CR change, which is quite large.  What is the standard way to do this, wiggle it and take an average?  Take the largest measurement for the benefit to the competitor?  Measure on both (or all four) sides of the piston top?  Thoughts?  Doing the block/piston CC method has potential to be more accurate because you can use a dial indicator on the top center of the piston which has little height sensitivity to wiggle, and no need to ever measure the deck height for CR purposes.

 

Example, stock pistons in stock bore.  Lot's of wiggle.  Pardon the dirty hands, was in the middle of dropping subframes when I took this vid. 

[Bench Racer]

 

The reason I ask, is that the pistons actually can wiggle around quite a lot, would be very easy to take a measurement that is 0.005" off.  0.005" error here correlates to 0.1 CR change, which is quite large.  Thoughts? 

 

 

 

Experiment, take 3 equal appropriate diameter gauge pins, place equally around piston OD to cylinder wall air space and CC. 1 pin perpendicular to wrist pin axis other 2 pins equally spaced.

[speedengineer]

Experiment, take 3 equal appropriate diameter gauge pins, place equally around piston OD to cylinder wall air space and CC. 1 pin perpendicular to wrist pin axis other 2 pins equally spaced.

You mean to place the pins to remove the wobble, and then to measure the deck height, not cc, right?

 

The beauty of CC is that it doesn't matter if the piston rocks, volume will remain pretty much the same, as one side of the piston comes up, the other goes down.

 

Just to note, 0.005" deck height measurement error results in the 0.1 CR error.  Now, for CC method, you could have 0.001" swept piston distance error PLUS 0.6 ml volume measurement error to have the same 0.1 CR error.  You would have to try really hard to have 0.6ml of volume measurement error during the CC process.  When I measured my piston/block, the measurements were repeatable all within 0.1 ml. 

[Bench Racer]

You mean to place the pins to remove the wobble, and then to measure the deck height, not cc, right?

 

  Yes

[Jim Drago]

on most sheets even if you cc... You will still need to measure the piston height.
I made a sm specific bridge with a dual indicator hole in the center. Also measured Pistons on a granite block and recorded distances from top of dome to flats.. So now I check piston in the center. Seems to be most accurate for me

[speedengineer]

on most sheets even if you cc... You will still need to measure the piston height.
I made a sm specific bridge with a dual indicator hole in the center. Also measured Pistons on a granite block and recorded distances from top of dome to flats.. So now I check piston in the center. Seems to be most accurate for me

Your tool sounds like an excellent way to measure, though that requires tech to have said tool and to know what the dome heights should be.  Lots of ways to do it though.  Could be as simple as two depth mics at once on opposite sides of the piston, take the average.

 

The only reason I bring it up is because if there's going to be an SM specific cc spreadsheet approved, it should include instructions for the deck height measurement procedure.  It's not quite a trivial measurement, has a significant impact on measured CR, and thus we should have a standard way for tech to perform that measurement to provide consistency.  I heard that this new spreadsheet is being proposed to the CRB on Tuesday, so just wanted to bring it up. 

 

In my opinion, a CR calculator spreadsheet using the fluid method that requires a measurement of deck height is overly complicated.  That is an unnecessary measurement!

[speedengineer]

Pressure washer worked pretty well on the subframes.  Removed all of the thick crud, flaky paint, etc.  They'll still need a solvent wipe down prior to paint though, to remove the last layer of oil, etc.

 

I depowered the steering rack today.  Before:

 

Took it apart.  Removed the chamber separating ring by using a cutting wheel to 'almost' cut through in two spots 180 degrees apart.  Then you use a chisel to break the ring off.  That way you don't have to cut into the shaft with the cutting wheel.

 

 

 

DON'T DO THIS, PROBABLY ISN'T SCCA SM LEGAL...NOW i HAVE TO BUY A NEW RACK.  It's legal now!!  Welded up the torsion bar in the steering shaft.  This removes a fair bit of compliance in the steering system.  -2 seconds laptime 

 

Put back together.  Sorry, no photos of greasing, but you put lots of grease in as that is the lubricant, now that power steering fluid no longer runs through the system.  The last time I did this, I spent way too long capping off all the openings where lines/fittings used to attach to.  I used the old fittings, removed the line from them, welded them shut, and reinstalled.  Way too much work, which is probably why some miata parts retailers sell pre-made block off plugs that you can purchase.  I didn't see the point in that.  All you're doing here is preventing dirt or water from getting into the rack.  So, I just filled the fitting holes with grey RTV.  Done.  Took longer to unplug my can of RTV than it did to fill the holes!  Will never let dirt in, quick to do, negligible cost, and it weighs less than metal plugs.  Less weight, so -2 more seconds 

[Bench Racer]

"So, I just filled the fitting holes with grey RTV.  Done."  Per Factory Shop Manual. TMI  

[Steve Scheifler]

Not to be a pinhead, but strictly speaking I don't know that welding anything would fall within the rules, or do you figure it is legitimately part of de-powering it?