Z3 1990 Miata
 

Hi everyone,
I recently bought a z3 converted miata(sounds sketchy), it is in rough shape but nothing that I haven't tackled before. Goal is to build a drift car with 250-280whp. Right now I'm thinking of getting this car in good shape and selling it and starting with NB miata. But if I will have hard time selling it, I will get 1.8 salvage donor for drivetrain swap. Boost set up I have in mind is 1.8 engine controlled by MS II V3.0, gt28 turbo, alcohol/water injection. I have same set up on my KLZE probe but with China EMUSA 50 trim http://www.cardomain.com/ride/3352149/1993-ford-probe/ .

Now let's lunch this fail boat with some pics. I'm using iPhone right now, so I might have to edit this post as I go.
Here is how I got it
http://http://i30.photobucket.com/al...psolot1s7m.jpg

It seems that iphone is failing me big time on posting pictures, here is a link to a photobucket.
http://s30.photobucket.com/user/art4...ary/Z3%20Miata

Curly to the rescue!

https://www.miataturbo.net/attachmen...ine=1419518467

http://i30.photobucket.com/albums/c3...pskheaciuw.jpg

Let me go trough list of fails
Body- major fail, paint is peeling down to metal, trunk lip/spoiler was built worse way possible(new paper used as a core for fiberglass) I gonna start with new trunk lid and build a proper ducktail that doesn't look like cavalier.
Engine was running on 2 cyl, cyl 3&4 weren't firing and white smoke coming out of exhaust. I thought it was a head gasket, pulled intake, the gasket looked like coolant port leaked into cyl 3&4, I replaced the gasket, no change. Next was to pull the head, head gasket did not show any obvious fails, I had the head pressure tested and resurfaced. When fired up, problem was still there, I did more troubleshooting, turns out fuel pressure regulator failed and was pumping gas into intake trough vac line, good thing KL FPR is the same.

Clutch slave and master are shot, so I'm waiting on parts to fix that.

Gauges weren't working, turned out to be a bad fuse.

Soft top is all ripped, gonna rebuild that.

I been reading threads for past few days, tons of useful information. I have done a fair share of fab work, I was also engine lead at WSU Formula SAE when I did my mechanical engineering degree, so I can't wait to start this build. Some of my other projects are C3 Vette, KLZE probe and my wife got e46 330CI ZHP.

Welcome to the forum. It certainly looks like you have your hands full with that project.

Good luck.

Merry Christmas.

I was expecting a miata with a z3 engine

that poor car. Please tell us you are going to remove that hideous body kit and return it to proper miata form?

Pretty cool probe you have as well, a bit boy racer for me.. but still neat.

What a pile of shit.

Please tell us how many of your hard earned dollars you used to get this, a dozen? 2 dozen?

Ditch the style bar, it does no good. It blows my mind why people make miatas look like Z3's...Z3's aren't expensive. If I had my choice over Z3 or S2000, it would be S2000 all day.
Good luck with your fixing up.

I paid $1300 for it, there is nothing worth looking at around here for less than $2200, all 1.8s start at 3k. I was gonna fully cage it, and if sell attempt fails, I will end up either 6 or 8 point caging this. The big downside of this kit for race car, if I tag a wall, that $1500 just for fiberglass, and I havent see any for sale yet, that's why I would like to get NB and use this as fund raiser.

Curly, I'm living in Portland, do you know any dyno shops that rent dyno for <$100/hr ?

English is 100 an hour KO is I want to say 65 if memory serves correctly

What Martin said. KO is $60 an hour, ER is $100 an hour.

You paid $1300 for that car?

:hahano:

Welcome, Artsvetkov!

Cage that thing and Lemons or Chump car it.

Best idea ever.

Quick Update
 

Got all of the mechanical and electrical things sorted out, got soft top replaced and converted the mouse trap into a roll bar.
https://www.miataturbo.net/attachmen...ine=1421550010

https://www.miataturbo.net/attachmen...ine=1421550010

Only thing left is to build a proper duck tail and paint before a sale attempt.

Why is it still alive.

How exactly do you figure that?

Sale attempt. :hahano:

it's still a mousetrap

I ran Stress analysis with simplified assumptions like A36 steel and simple fixtures, using 3000lb force in x direction and 3000lbf in y. I got min FOS 1.7 and Max displacement of 0.026". What do you base your assumption of a mouse trap?


https://www.miataturbo.net/attachmen...ine=1421613242

https://www.miataturbo.net/attachmen...ine=1421613242

Without a doubt, that is a style bar. Designed for looks, not safety, and that's just from the mounting points. Drill a hole through it, you'll probably be shocked at how thin it is.

Seems to me that all you've really done there is GUARANTEE that it will fold forward into the occupants' space in the event of a rollover.

This is simple. Drive the car into a garage that has some sort of overhead hoist.
Attach cable to "newly engineered style bar" and try to lift the car off the ground. If it comes off the ground, you win. Try it and find out though...on video...just for proving me wrong purposes.

https://www.miataturbo.net/attachmen...ine=1421618282

you are the one making assumptions.
they will kill you some day. literally

If you look at that picture the bar didn't fail, it folded at the seat belt tower due to non triangulated load. If you take hard dog 4 point bar and chop rear legs off, it will do same thing. Btw style bar is 2.25x1/8" tubing, seems like people talking about it never handled one in person, and I agree that with no rear legs that thing will fold easy. As for assumptions, I was neglecting load distribution to front/rear contact point of the car when it flips, and assuming that the bar takes full stress. In real life, quite bit of the weight will be on the front portion of the hood, just like a hinged beam simply supported at other side.

There's only one way to prove us wrong... real life roll over testing.

All joking aside it's an improvement but why mess around with skimping on something that might one day save your life (or end it). Hard dog and similar design roll bars are proven to be structurally sound to do it's job in a roll over. Why risk it?

Don't forget the load the center portion of that thing will now have to take. The boss frog double bar attaches to the transmission tunnel for a reason.

Very interesting that's for sure. Lotsa ambition.

The reason for the work put into some shitty chinese pot steel is "because Probe owner."

These guys don't understand what it's like to have legit parts readily available at fair prices raining from the sky.

The only thing worse than having a problem is convincing yourself that you don't have one.

I can tell by your stress analysis results that your model isn't a good representation of reality. You are assuming that that bar had true fixed supports all over the place. As in, when this thing rolls, no piece of the chassis will deflect even 0.001". Really?

Also, a 3000lb force is too small. Sure, if you gently set the car down on the bar, it MAY survive. Rolling at speeds of even 10 mph the forces involved are much, much larger than 3000lb on a 2500lb car. At 50 mph, I don't even want to know what the forces are the roll bar may see.

Your assuming the material, the bar thickness(and its uniformity through a very questionable style bar), the welds will be perfect, the forces are really low, and true fixed supports on the chassis. Each one of these assumptions makes this model invalid.

Just buy a real roll bar that's actually approved by some sort of sanctioning body, like SCCA. They are pretty cheap for the miata. This will potentially save your life, or the person you are selling it to. Enough said.

Going with what 18psi said, your trying pretty hard to convince yourself that everything is fine. Your additional bar added to the style bar will strengthen it some, but not enough to be trustworthy for a real roll bar.

Just flip it off a cliff and prove everyone here wrong.

A 2400lb car falling on its roof at 20mph in 6 inches of distance (let's say it was soft dirt) exerts 64,227lbs of force somewhere. Some of that force will be taken by other parts of the car body, sure. But what portion of that does the roll bar need to withstand?

Source calculator: http://hyperphysics.phy-astr.gsu.edu/hbase/carcr2.html

a 3000 (a street miata with people and stuff) lbs vehicle decelerating from 73.33 feet per second (50mph) to 0 feet per second (0 mph), in 6 feet (distance from front of car to style bar) will create a force of 20.9 tons. or 41,800lbs. if the style bar is the first ting to hit and the distance is 0 feet then the force will be 124 tons or 248,000lbs of force.

source. http://hyperphysics.phy-astr.gsu.edu/hbase/carcr2.html

In for stress analysis results on 248,000lbs.

Hell, I'm in for stress analysis on 64,000 lbs.

For reference, the machine pictured weighs 57,000 and is lifting a segment of 42" diameter RCP (Reinforced Concrete Pipe) that weighs just under 7,800 lbs (or about 3 Miatas).

https://www.miataturbo.net/attachmen...ine=1421688843

Also for reference, the iihs tests roof strength by lowering a steel plate with a force equal to 3 times the weight of the car.

Those are different forces, you are comparing crumple zone to a roll over force. Car trevaling at 50mph and not rolling over and stoping in 6ft, friction coefficient of steel is far less than a tire on pavement, so you will be skidding on your roof to a stop a longer distance than a regular stop.

I'm not claiming that this bar is an ultimate roll over protection, six point cage is a minimum that I would trust on roll over. I'm just saying that it won't fold over like the original bar would. Btw DOM tubing is a regular ERW tube processed through cold work that gives it 40% strength increase, a tubing spec for 2500lb car is 1.75"x.095 wall DOM which is what Hard Dog bar uses, next step for 3000lb car is .25" OD increase, switching to .120 also counts as a step increase. I used 2"x.120 wall DOM for my tubing and main structure is 2.25x.120, so even with untreated steel, the size is 4 steps up.

It will, though...

Just ran a sim on 4 point bar traditional style with a main hoop using 1.5OD and 0.12 wall with 75ksi yield strength(TuffDOM) regular DOM 1020 steel is about 60ksi. using same 3000lb loads I got this.

https://www.miataturbo.net/attachmen...ine=1421723957

https://www.miataturbo.net/attachmen...ine=1421723957

not any stronger but about 10lb lighter due to superior strength compared to 35ksi I used for no brand bar.

You are the dumbest dumb if you think you're doing these tests correctly, or that your bar is in any ways adding safety.

Who makes a bar that looks like that anyways?

Show me a proof using statics/mechanics of materials or FEA analysis.

Show me real life proof that any of your statics/mechanics of materials or FEA analysis has anything to do with real life/actual roll over.

You still haven't come CLOSE to matching an actual roll bar or it's mounting points. Much less come close to real life forces.

If you're so hell bent on using FEA, you need to be doing stress tests on rolled over miata roll bars, not guessing by the weight of the miata.

How about i don't need to. I took advantage of chep legit miata parts and spent my time working a few hours of overtime to buy a quality part that isn't dangerous.

If your idea was good, people would have done it. No certified roll bars look like that. Either of your examples, actually.

Hard Dog Hard Bar Sport - Polished Stainless Steel

That's what I used for second bar. I used same loads for comparative analysis only.

Anything I say or prove doesn't matter because everyone is going on "Nobody does this bias".

I would be more worried about the material than the structure of the bar. Is it really 1/8 inch thick tubing? Because if so that is a damn thick style bar. Most of the ones I've seen are built out of like exhaust tubing.

I think what everybody is trying to say is, if you take a buffer and some wax to a turd, no matter how much you polish it, its still a piece of shit.

I have no idea where this bar came from, but I was surprised at how thick the components on it are, I would of expected exhaust tubing as well. It weights over 30lb which is consistent with mass properties of my model.

I think I found the source of this style bar MossMiata.com - Parts & Accessories for Your Mazda Miata

The ones I saw on eBay are polished stainless steel and 2" OD, mine is chrome finish with 2.25" OD. Maybe that's why ebay bars are so thin, because they are a visual copy of this one but they are too cheap to add chrome plating process and knock it out of a thin walled stainless steel to save cost.

You notice how even Moss lists it as a style bar?

C'mon man. You're smarter than that.

I mean there's really no need to pretend. Half the cars here don't even run any bar at all, which is dangerous too, so it's not like you're doing something absurdly crazy. I just think everyone's issue with this is that you're convincing yourself that this is safe when it's not.

They not listing it because it needs to have 4 points of contact. I get what you are saying, if I was to race this car I would go with 8 or 10 point cage, but for street use I don't think it's worse than nothing. I agree that with 2 points of contact it is worse than nothing.

The sanctioning bodies for NASA and SCCA track days also require a minimum of one diagonal support to the main hoop and that your helmeted head not exist at a higher point than a line drawn from the top of the rollbar to the top of the windshield (infamous broomstick test).

https://www.miataturbo.net/attachmen...ine=1421777673

build it like this. then run your tests the material should be 1.75" .095 Dom tubing.
FYI this is a lemons cage. it doesn't get any "less" then this.

http://www.autopowerindustries.com/I...d/DSC_2848.jpg

here is a typical NASA legal roll bar. note the support tube mounting position on the main hoop. also note the cross bar location inside the main hoop.


although there is some name calling in this thread. everyone does have your safety in mind, and they are trying to help you.

I will give that sim a shot, not trying to prove that I have awesome bar or anything, I'm just curious how will a proper sanctioned bar will behave under equivalent loads and sort of stress distribution path it will take and see FOS.

a properly sized bar will attempt to protect you in a roll over. the style bars in the industry have no horizontal support. when a car rolls over, the forces are not 100% vertical. The vehicle will be moving forwards or backwards too. that forward movement will bend the style bar and it could trap you under it. that's why everyone is calling it a mouse trap. :brain:

the other thing to look at is that the style bar simply isn't tall enough to protect you in a roll over. that combined with the potential to be trapped by it makes running no style bar safer then running one.

The other thing that no one has really pointed out is how the "style bar" bolts to where the seatbelt bolt in. For a roll bar that is not an acceptable mounting point. If you check out how any of the real roll bars mount, they may have a bolt there, but they also go much further down and bolt into the actual chassis.

Done and sold.
https://cimg4.ibsrv.net/gimg/www.mia...2c058cdb55.jpg


https://cimg5.ibsrv.net/gimg/www.mia...751db395b1.jpg


https://www.miataturbo.net/attachmen...ine=1445179882


https://www.miataturbo.net/attachmen...ine=1445179882