825 replies to this topic

[speedengineer]

^Yup!  Also, Steve, you may want to look into a Recaro Pro Racer Hans. It's such a narrow seat that I easily fit it without even having to notch the trans tunnel.  Did need custom mounts though, similar to what Chris described.

 

I will be performing the floor pan lowering modification on this build.  I'm not tall at just over 5' 8", but am tall in the torso.  On the last car, with the seat bottom touching the floor pan, when I moved my head to the side, my helmet would hit roll bar padding at the same time as the seat head wing.  That scares me in a side-impact scenario, potential for compression of the neck.  Thus, I will be taking advantage of floor pan lowering mod.  Also looking forward to how easy it will be to mount the seat, as now it will be bolted to a flat piece of sheet metal! 

[Steve Scheifler]

Tunnel notch panel helps a lot with those problems. Also for fia seats using a bracket that is a 90 deg bend at the bottom as apprised too the normal sparco type that bend out first allows the seat too be positioned another inch too the right helping with clearance. Biggest 2 guys I know are 6'5 220 and 6'2 220 both have the sparco pro adv with a Miata cage too the floor with out problems. Both cars have notch panels and straight sided 90 deg bottom brackets.

I'd like to get a closer look at those. We have the notch panel and the right-angle brackets, but without placing the seat way off center inboard the shoulder supports do not clear. I like shifting my weight inboard but there is a limit in terms of comfort with the angle to wheel and pedals. Part of the problem is the location of door bars, relatively high, and of course that can be mitigated when building around the seat, but we were retrofitting to old cars.

[Steve Scheifler]

Why wouldn't you lower the floor before installing the cage??

[speedengineer]

Why wouldn't you lower the floor before installing the cage??

 

I like making things difficult, haha.

 

A few reasons, but mostly because I'm concerned about the chassis tweaking when I cut out a large section of floor pan.  I don't think it is likely to tweak since most of the structure is in the rocker panels, but I don't want to risk it. Once the cage is in, then I know it wont move, and I'll cut the floor pan out.

[Ryan Roberson]

Looking good Jason!  It's going to be cool to see what you accomplish during your week off!

[dstevens]

I like making things difficult, haha.

 

A few reasons, but mostly because I'm concerned about the chassis tweaking when I cut out a large section of floor pan.  I don't think it is likely to tweak since most of the structure is in the rocker panels, but I don't want to risk it. Once the cage is in, then I know it wont move, and I'll cut the floor pan out.

Take into account the landing/footing for the driver side rear of the cage  Take a look at Drago or Wheeler's pan mods and you'll see the cut goes all the way back to the package tray base.  If you land the cage on the normal level of the floor when you cut the floor for the pan you may have to re fab the landing for that leg of the cage.  A couple weeks ago when I was going to drop the floor I noticed that in mine.  I didn't have any stock thick enough to rework the landing and it was over a weekend so I decided not to do it right now.  If I were building right now and in a time crunch I'd get one of the floor pan kits.

 

If you are concerned with twist tack a piece of tubing to the underside of outboard side the rocker and you should be good to go.  I had to cut some big patches of the driver floor ( most of the front footwell a foot or so back from the pedals)  as they had rusted through and didn't have any flex issues when they were out and it was just a tub.  Though it wasn't as much as you'd cut for the mod.

[chris haldeman]

I'd like to get a closer look at those. We have the notch panel and the right-angle brackets, but without placing the seat way off center inboard the shoulder supports do not clear. I like shifting my weight inboard but there is a limit in terms of comfort with the angle to wheel and pedals. Part of the problem is the location of door bars, relatively high, and of course that can be mitigated when building around the seat, but we were retrofitting to old cars.

Seat is off center quite a bit. Looks funny sitting still. Never noticed when driving

[speedengineer]

Take into account the landing/footing for the driver side rear of the cage  Take a look at Drago or Wheeler's pan mods and you'll see the cut goes all the way back to the package tray base.  If you land the cage on the normal level of the floor when you cut the floor for the pan you may have to re fab the landing for that leg of the cage.  A couple weeks ago when I was going to drop the floor I noticed that in mine.  I didn't have any stock thick enough to rework the landing and it was over a weekend so I decided not to do it right now.  If I were building right now and in a time crunch I'd get one of the floor pan kits.

 

If you are concerned with twist tack a piece of tubing to the underside of outboard side the rocker and you should be good to go.  I had to cut some big patches of the driver floor ( most of the front footwell a foot or so back from the pedals)  as they had rusted through and didn't have any flex issues when they were out and it was just a tub.  Though it wasn't as much as you'd cut for the mod.

 

Well, Dave's pan actually drops down about 2 or 3 inches in front of the rear bulkhead, and Jim's about 1 inch in front. 

 

I'm probably just being paranoid about chassis twist...

 

Here is my approximate plan to do the floor pan with the base for the main hoop already in place.  The diagram doesn't show it, but like Jim and Dave's designs, the floor pan metal will overlap the existing sheet metal.  It'll likely also overlap the 'front plate' of the main hoop base, for strength.

 

Version showing the 'overlap' of panels:

[speedengineer]

Looking good Jason!  It's going to be cool to see what you accomplish during your week off!

 

Well, I didn't accomplish very much on my week off, Ryan!  Thursday and Sunday night I worked on building a welding cart, which has to get done prior to the cage. 

 

No progress on Friday or Sat.  It is Justin Hille's fault. 

[Jim Drago]

Well, I didn't accomplish very much on my week off, Ryan!  Thursday and Sunday night I worked on building a welding cart, which has to get done prior to the cage. 

 

No progress on Friday or Sat.  It is Justin Hille's fault. 

don't forget to add that cart into the budget And it is all Hilles fault, all the time!

[Bench Racer]

  It is Justin Hille's fault. 

That's what his competitors say when they come off track after a race.

[Chad Martin]

Good Stuff Jason, can't wait to see your finished product on track!

 

I'm a fan of this effort and what it represents between the lines.

[Lmcgrew79]

As always, I appreciate the advice and tips many have given.  Keep em coming 

 

Just getting going on the build now - been busy getting the house ready for a long winter as well as installing a 2-post lift and getting a new welder set up.  So far, nothing too exciting.  I've been stripping that trunk and interior in preparation for the roll cage build.  Next steps will be to remove all the tar sound deadening and begin scraping seam sealer and removing paint where the cage footings will weld to. 

 

 

 

Unfortunately, the car apparently had a leaky soft top at one point in it's life.  That water caused the rear package tray and fuel tank access panel to be rather rusty.  Looks like I'm going to have to purchase new ones of those. 

 

 

 

On the previous race miata I built, I removed the tar sound deadening using a putty knife and heat gun, then a wire brush on an angle grinder removed the remaining residue.  This actually worked very well and didn't take long, it's just messy.  I've seen dry ice method, but it doesn't appear to come off much easier, and I'll end up dinging up the sheet metal with the hammer.  Does anyone have any other clever tricks for removing this stuff?

 

 

I also scored an OEM hard top for $550.  It does need a bit of work, bit of bondo on the trailing edge where it must have been dropped, and paint of course.  I'll probably have another $75-$125 into it at that point, but ~$650 isn't bad considering how much these go for now days!!!

 

 

 

As everyone has mentioned, difficult to compete at a majors level unless your car is making the HP, period.  I am well aware of this!  It's very possible that my motor build won't make the numbers that the pro builders can achieve, in which case I'll have to pony up some cash and buy one.  However, it's also possible that my motor will be right there.  Anyway, I've run some analysis using a lap simulator I wrote to determine the laptime sensitivity to HP at Mid-Ohio.  Hmm, Mid-Ohio   Anyway, it shows what we already knew, that you've got ZERO chance of running up front if you don't have the motor for it!  Eight hp per second means you can't afford to be down more than a couple from the rest of the drivers, or you will be having to drive all that much harder/better.  I also calculated the laptime weight sensitivity, just for fun. Being lazy setting your fuel load, thus crossing the scales at 20lbs more than you wanted, means you give up about a tenth of a second per lap. 

 

 

 

 

So this is pretty incredible, can i give you some numbers and see what you get? What do you need weight, rwhp, frontal area, drag co effiencey?

[speedengineer]

So this is pretty incredible, can i give you some numbers and see what you get? What do you need weight, rwhp, frontal area, drag co effiencey?

Thanks.  What are you trying to investigate?  I've got the inputs set up pretty well for a spec miata.  The simulation is best at calculating the difference in performance between two or more cases, so you only need to vary the input that your are trying to investigate.

 

 

 

Example inputs:

note: these inputs are just an example for an FRS, not a miata:

[Lmcgrew79]

So will it do a theoretical lap or more for compairing 2 simular

cars.

[speedengineer]

So will it do a theoretical lap or more for compairing 2 simular

cars.

 

There are many variables that affect the theoretical lap time, thus the accuracy of that theoretical time isn't so useful.  What is beneficial is it allows you calculate a theoretical lap time for a car, then add say 5hp and determine the difference in lap time.  Or change weight, or aero, or final drive ratios, etc.  Say I wanted to study the difference in potential benefit of 99 vs VVT performance at Mid-Ohio, I could simulate the lap with a representative VVT power curve and weight, and with a 99 power curve and weight, and see the lap time difference, and where on track each was better. 

[Todd Lamb]

Are we at $20k yet?

[speedengineer]

Since no pics of car progress, here is a cost update. 

 

So far, up to about $7400.  When I estimate what I have left to purchase to complete the build, I come up with around $3800.  This makes the build only a little over $11k excluding data system and transponder!!!

 

[speedengineer]

Are we at $20k yet?

hahaha.  that was coincidental timing 

[Lmcgrew79]

Eerie!