planned miata project
 

Hi all,

I finally took the plunge and joined this site after using it as a reference several times. About a year ago I got a 2006 prius and started hypermilling, at first my avg tanks were about 5.0l/100km but I soon got that down to 4.4 and then by the end of the summer I was getting some 3.9 tanks. The best sustained period I had was 3.4 for about 70km but I couldn't keep that up for the whole tank. I did a few modifications including: stubby antenna, motorcycle side view mirrors, top grill block (added a lower block for winter too), lip spoiler at the trunk edge as my version had the smaller spoiler, rear wiper delete (summer only), LRR XI2 winter tires (which actually improved vs the non LRR falken tires). So far my lifetime avg is 4.88 for 19369km, winter tanks tend to be around 5.1-5.4 and my worst where I tried to drive moderately aggressive was 6.18.

I love my prius, I even convinced my dad to get a new prius V which is funny because my last car was a Saab 95 wagon and he bought one for my mom a few months after I got one. However with our first child on the way the wife and I decided she should drive the prius due to the higher seating and easier loading hatchback (for the stroller). Since we have a miata that hardly ever gets driven I will use that as my work commuter and we will turn in her lease to save money for the eventual day where we need to haul two kids + and I get my prius back and hope to convince her the highlander hybrid is the best car for her.

So with all the fun I've been having saving gas I've started to think of some planned projects for the miata. It's a 93, 1.6l 5spd with 195/60/14 performance Hankook RS2 tires, just purchased a hard top, no AC.

Planned mods are:

• Skinnier tires, looking at fitting 155/80/13 on steel wheels and if I find they handle well enough then getting Honda VX rims. If they don't handle well enough then 175/65/14 on the stock 12lb miata rims. - Fitted 155/80/13, 60% tread for $50 on steel rims, great deal off kijiji
• air dam - one of the miata problem areas is the exposed front tires which I'll have to address
• skid plate/undercarrage Coroplast extension to stock undertray
• motorcycle mirrors - Complete, no passenger side mirror
• tire spats - I'm thinking about mounting to the suspension arms to get them really low integrated to the undertray, coroplast so it's low and if it hits it won't cause any damage
• diffuser - I don't think this will be easily accomplished
• kammback
• projector HID lights inside turn signals (i'll keep the pop up head lights for legality but use the projector lights in the city) H3 (non projector) lights plus LED DRL
• possible alternator disconnect switch
• de power steering rack belt removed, if it's a good enough benefit I'll loop the lines and remove the pump. I may even remove the rack and convert it to a manual (flyin miata for details)
• grill block (partial) complete
• ignition advance (this is very easy on the miata and I already did 8 degrees I think, I'll try a few increments on the various fuel grades to see which is best. If I can use premium at a cost neutral level I will because we can get 0% alcohol premium at shell.
• maybe rear wheel skirts
• max tire pressure - 38psi
• warm air intake - this is very easy since there is already a cone intake I'll put some pipe from the exhaust side over to the cone - complete, removed the heat shield on the header and supported the cone intake right over top
• 0w20 engine oil and a change of trans and diff oil too (haven't looked into what type yet for them) mobil 1 engine oil, don't think I'll do the trans/diff as the cost would probably not be recovered
• vac gauge
• I'll try a single wiper arm but may just go with 2in smaller drivers, 3in smaller passenger side went with 2in smaller drivers, 3in smaller pass side
• stubby radio antenna

and that's the starting point.... I havn't driven the car for normal commutes in a few years but when I was younger and avg about 140km highway I was getting 9.5 and found that by slowing down to 110 I could avg high 8s. Based on fueleconomy.gov the avg for all years of 1.6l cars is 7.9 so I'll be shooting for 6.9 pre major mods and I would be very happy if I could get it down to 5.0 but realisticly I think 5.9 may be the lower limit.

Nice job on the mods. Check out the "Physicist" thread... I might add, I was a 6'4" teenager with one sister and the biggest car the folks had at the time was a VW Rabbit and it worked just fine.

This list is very close to the list for my car in most respects, so I like. But you should have a better opportunity than me for a Kammback because your Miata is convertible. Couldn't you build a nicely curved and tapered top? It could come off as easily as the stock hardtop, but have some of the ideal aero lines often discussed on this site. And congrats of the new child too! But I have to agree with Frank Lee too... my wife and I got buy with this two door coupe when our daughter was a baby... and I remember epic road trips with my two brother, my mom, our dog and cargo in a 1975 VW Bug. It can be done!

I'm 6'4" too so the miata is a tight fit but very comfy once inside. My first car (which I still have but it's a race car now) is an original mini. So I'm quite use to making small cars work.

I want to build the kammback onto the hard top for a few reasons. I already know from racers that the stock hard top improves aero, they say it's good for at least 7mph on straight long sections of tracks. It's weather tight, I won't find in the dead of winter that it leaks and I don't have an indoor area to work on cars. Build time will be reduced a lot Safety, I know the stock hard top is on tight and will not fly off. In the event that part or all of my kammback comes off it will be a much smaller and less dangerous event. I think that it will look a lot better and cleaner with the hard top. And the most important, body flex, the miata is famous for this, and my year (the lightest) has the most. I'll probably add a roll bar if I can, but before that any full kammback from the windshield back is likely to break or leak due to the normal everyday flexing of the chassis.

Since it's a convertible with no AC in July and Aug I'll probably end up going back to the soft top and I want something that comes off easily and still leaves the mounts for the soft top.

The kammback is also planned to be for utility. The first one I'll probably do coroplast for testing but eventually I want to use plexiglass with a higher back, remove the trunk lid and have the back section hinged to add trunk volume. I figure the old trunk seals will give me a place to bolt/screw to that can be hidden and returned to stock. I'd rather spend my time perfecting this than the fit and seal at the front of the roof.

Thanks to kijiji I found some 155/80/15 tires, 70% front and 50% rear for $50 so I drove and picked them up today. Since the miata has 14s and people say most 13s fit I was glad to try it out with a cheap set. They fit weel, not much clearance with the brakes but enough. One downside is the max psi, only 34!!! So I pumped them up to 37.5 front and 37 rear. I figure on a 2200lb car that it's probably enough.

Here's an overview of the car, a shot showing the amount of tire that sticks out past the front bumper and a comparison of the rear view when one side was changed.

.....and the pics will be posted after 5 posts....

I still haven't sold the wifes car and haven't insured the miata yet but I can't wait to drive it, but with gas up at $1.30/L now I'll miss the prius.

http://i173.photobucket.com/albums/w...d/IMAG0257.jpg

http://i173.photobucket.com/albums/w...d/IMAG0256.jpg

http://i173.photobucket.com/albums/w...d/IMAG0255.jpg

I'm diggin' the Superman color scheme.:p

Welcome to EM!

Got my miata on the road since I needed to loan the prius to my mom as her car broke down. I started a few projects, put the motorcycle mirror on the drivers side which needed to be done since the stock mirror had rusted out and wouldn't stay in the position it was adjusted too. Also added a roof spoiler. I was thinking it would probably work better up on the roof vs the glass but since I want to vinyl wrap the roof I chose to put it on the glass.

http://i173.photobucket.com/albums/w...d/IMAG0276.jpg

http://i173.photobucket.com/albums/w...d/IMAG0279.jpg

Have you considered losing the windscreen, going for a partial windscreen and waterproofing the passenger side while suiting up yourself?

Too hardcore?

Yes, too hardcore, the car has to offer me daily commute including Ontario winters.

My first fill up got me 6.1l/100km, 38.6mpg. 371km, about 1/3 city, 2/3 highway at 95km/hr. The highway revs at 3200rpm too so that's probably hurting the economy.

I'm pretty happy with that and it has me thinking that maybe 5.0 (47) is achievable.

I had a busy weekend working on the car. First off my second tank, not as good at 6.33l/100 which involved 100km of stop and go rush hour vs the previous tanks 50, and also more city driving this tank.

I started my work on the car with trying to adjust a noisy belt which started a chain of very annoying events. The power steering belt was removed to test the econo benefit from that. That was easy enough, but the alt/water pump belt was the one making the noise. I turned the adjuster and snap, bolt broke off. Easy enough to fix though so I went to turn the bolt that holds the adjuster on.... snap.... ok so now I have to take the alternator off and drill out that snapped bolt so the bottom bolt has to come off. Can anyone guess what happened? Yes, snap... So I can't get a drill in that space so I have to use the dremil to drill out that snapped bolt which would be fine except my dremil breaks....

So I borrowed my dads, drilled it out, got the belt back on and as tight as possible, a little better but still a small noise from the belt so I figure now I get to do the fun stuff.

Oil change with Mobil 1 0w20.

I added LED stripes for the day time running lights DRL. I'll be using all LED for the lighting with the exception of the front turn signals so that less energy is used during EOC.

http://i173.photobucket.com/albums/w...d/IMAG0291.jpg

I also removed the stock DRL/turn signal and drilled a new hole in an unused side portion of the light. I then added some H3 lights inside the spot that use to be the DRL/turn signal to use as headlights and avoid the aero hit of the pop ups.

I wired these up to come on with the parking lights so I can turn them on for night driving but still use the pop up low and high beams if I ever need the full lighting system. I will also be adding 50w HIDs in 4300k to the system. I ordered them after trying out just one of the lights and thinking it was a little too low, but after both were hooked up I was starting to think it might be enough.

http://i173.photobucket.com/albums/w...d/IMAG0296.jpg

Next came the front grill block. I went to the local dollar store and picked up some coroplast garage sale signs, $1.25 each. They also had some blue duct tape that looked really close to the miata blue. I bought that only thinking it would be for the passenger side mirror holes but then decided to use it on the coroplast instead of painting that black. I sized the hole in the middle so that in the winter I can simply turn the license plate bracket upside down and lower the plate to block it.

http://i173.photobucket.com/albums/w...d/IMAG0289.jpg

Next I turned my attention to the front wheels, a well know miata aerodynamic nightmare. I ran out of tape so only covered one. I will be going and getting some steel L brackets from the home depot tomorrow to hold the sides in against the high winds.

http://i173.photobucket.com/albums/w...d/IMAG0292.jpg

And with the left over coroplast I started on an under tray extension as the miata has what looks to be a pretty decent undertray already. This is a really horrible picture, I should have got it from the side to show how the corners have been fully filled prior to the front wheels.

http://i173.photobucket.com/albums/w...d/IMAG0294.jpg

Now I'm very excited to see how I can do on my next fill up. I will probably then re hook up the power steering to see exactly how much I can attribute to that mod.

Any updates on your '93 project?

I've got a '91 BRG that I've been working on for better economy as well. A few things you may want to consider doing later down the road that truly help improve mpg's...

* An aftermarket front spoiler (lip) as they call them. I thought about getting the stock R Package lip, but decided on the Garage Vary lip instead as it's bigger, effectively getting the front of the car closer to the ground. I haven't measured it, but if I had to guess, I'd say the bottom of the lip is roughly 3" off the ground.

* Lowering the car about an inch to inch and a half, either with slip-on adjustable spring perches or full coilovers which I have. Measuring from the center of the hub to the wheel well, I'm sitting at 12.25" front and 12.50" rear.

* A free flowing exhaust system including NOT a 4-1 header but a 4-2-1 header as they are better for low to midrange power. A free flowing cat and muffler as well, all 2.25". I find this to be a great combo to the stock intake.

* Shave as much as weight as you see fit. So far, I've removed 135 lbs from my Miata and plan to remove a little more by deleting the power steering. I'll elaborate more on the weight shaving if there's any interest.

* I haven't done this yet, but I plan to in the near future, which is do a small cutout on the rear bumper. It traps quite a bit of air back there like a parachute, so trimming a few inches off of it will reduce this drag.

* Get a good 4-wheel alignment! I have aftermarket 15x7 (14.7 lbs) wheels with 205/50-15 performance tires with a fairly aggressive alignment and actually saw an increase in my mpg's after the alignment.

I've done all of the above except for the power steering delete and rear bumper cutout. All of this allowed me to achieve 30mpg keeping up with traffic (between 75-80mph). In complete stock form I could only manage 31mpg doing a constant 60mph, or about 25-26mpg at 75-80mph.

Now, doing 60mph and some hypermiling, I've done a best of 37.8mpg on my last tank, managing 393 miles to that tank. I'm still "feeling out" the car as far as hypermiling is concerned, figuring out optimum shift points and acceleration rates. So with every tank, I'm increasing my mileage a bit more. I'm sure I'll see over 400 miles on this tank.

BTW, I travel 112 miles every day, 100 miles on the highway at 60mph and the other 12 miles in town between 25-45mph. In town, I can actually coast nearly half of that. While on the highway, I only coast on the downsides of hills and overpasses. I have yet to do any real Pulse & Glide as I can't see how that's going to help me on the highway, not to mention there always seems to be too much traffic to attempt it.

Anyway, here's a pic of my little pride and joy!

http://charlest.zenfolio.com/img/s3/...74044856-4.jpg


One more thing, I too have replaced ALL of my exterior lighting with LED's, minus the headlights of course. I even converted my left backup light to a fog light with a high-output LED.

http://charlest.zenfolio.com/img/s3/v40/p50858870-4.jpg

Looks like a good start. Looking foward to seeing more.

Not much to update as on my last drive the alt belt broke and I got towed home. Then I left for 3 weeks training in BC so no driving.

I've been thinking of a front lip for a while. I'll probably end up making one out of garden edging. I wanted to get the full front under tray done first, see what improvement that made as the front lip increases the cda, it's only beneficial because the miata underbody is very poor. Also since I will be winter driving the car the lower suspension and an expensive lower front lip are not the best combinations for me. I also don't want to do suspension work because the car hasn't had many kms since the alignment. The cost to lower and re allign will never be recovered by the FE improvements I think I'd see. I also don't want to put any money into the exhaust system.

I may start the rear bumper with drilling some holes and/or covering the bottom with coroplast. I'd rather test that for the small cost first before cutting a lot out.

I was also thinking of getting taller tires, stock being 185/60/14 I have heard that 185/70/14 has been used, that should drop 400 or so RPM from the highway cruising speed.

Also to update the full grill block it caused the temp to rise too much at highway speed on a 15degree Celsius day even though it had been fine at the low city revs of 2000rpm and below.

Wow. Just about all of my suggestions shot right down.

Just an FYI, I have kept a fuel log ever since I got the car in Jan 2011 via Gas Cubby on my iPhone. With everything that I've done to this car over that time, I have seen constant improvements with every modification made.

Also, adding the lip spoiler does NOT add to cdA, it adds to the frontal area. But when the car got lowered, that frontal area also got reduced slightly. Due to the installation of the GV lip spoiler, it greatly reduced the air flowing under the car, thus reducing cdA a bit as well.

But anyway...

Im sorry I didnt mean it to sound like I was shooting down your ideas, I agree with all of them I just wanted to say how I don't have any money to put into the car.

Fellow Miata owner here looking forward to future updates.

The next big update will be fitting 195 70 14. Since the car revs so high at highway cruise I hope that will improve my mpg. It should also allow longer EOC, also the 155s only have a 34 psi max and I've been running them at 38. They tend to leak put back to 34 but not much lower. I hope that the tire spats will compensate for the 4cm per tire.

I can see going for bigger diameter in these tires, but you might trade some of the FE gains from RPM reductions at highway speeds for FE losses due to wider and heavier tires.

Got the new tires installed today. 185 70 14 front and 195 70 14 rear. It has dropped about 500-600 rpm at 100km/hr. The speedo now reads 100 when I am going 102-103 instead of reading 100 and going 95 as it was before. The odo was pretty dead on before and now puts 14km on for every 15km I drive.

I had searched and heard that 185 70 14 fits on the front with minor right hand turn rubbing, however I found it was pretty annoying and had people turning heads when I entered the gas station. I trimmed back part of the wheel lining and then after a quick test drive it was only minor rubbing. If I had to do it again I would have went with 175 70 14 fronts.

Here is a picture with just the passenger side changed to show the ride height difference.

http://i173.photobucket.com/albums/w...d/IMAG0338.jpg

Here is a picture from the side.

http://i173.photobucket.com/albums/w...d/IMAG0339.jpg

I can tell it's much higher when I'm getting in and out, about 2 in over all diameter so 1 in higher. It actually makes it more comfortable to get in and out of. Because of this height I will be concentrating more on the under air flow and playing around with air dams. I went to Home Depot but couldn't find the appropriate edging that I have seen used before.

Now I'm at 45psi all around, I never did a full coast down test before but on one main slight downhill from my house I made it past a stop light that I was usually starting back up before. It feels like it coasts smoother and when trying to shift at 1800rpm first gear feels like it should instead of an instant shift to second.

The next big project will not be fuel economy related. Painting the hard top flat black. However it will allow me to do a tank or two with the soft top up/down and compare the MPG from having the hard top installed.

You'll have to change the name to Bigfoot or Sasquatch.

Ex GF used to think she had big feet so I'd call her Sasquatch. Hmmmmm....

Oh also forgot to add that I thought I may have needed to re connect the power steering but these turn as easily, maybe even better than the 155 80 13 did.

I was excited as I was approaching the half tank mark since I had done way more km than I usually get. I usually hit 200km either just before or just after the half way mark, hitting it before was a good indication that I was going to have a good tank. So when I left work at 244km and not at half way yet I was really excited to see how many km I'd hit half way at. Well I got home just a hair under half way at 288km so the new tires really are working.

After several longer tests the odo is off by a factor of 1.088. and all the kms I have are corrected. The old odo was never off by more than .1km after 20k tests so it was pretty accurate.

I'm very excited to start work on an air dam but I really want to do a whole tank with the tires being the only change first.

5.43 L/100 km
43.31 mpg (US)

It's been fun.... but the miata is dead. Took it in to get it certified to switch from my dads name to mine and it was found to have a leaking gas tank. The mechanic said "that's a major safety issue" and it's bad but my first thought was.... that means I was actually getting better millage than it read since some of it was just leaking out!

So now it's time to look for a new car. I'm thinking to leaning towards a cruze eco 6spd or hyundai accent 6spd. I love the hatch back and larger back seat of the hyundai but the cruze is just a much nicer car for the front seat occupants and the triple over drive will be nice for the work highway drive.

or you could just buy a new or used gas tank, phone around to some junk yards.

The problem is the gas tank is under the rear subframe. Fixing/replacing it involves dropping the whole rear axle and removing a lot of bolts that are very rusted on. I thought about it but with the labour involved in just getting it out to maybe find that it won't bolt back up together was too much of a risk.

Replaced with 2012 Kia Optima 6sp manual.

What a waste.

Getting rid of a perfectly good Miata just because the fuel tank needed to be replaced. A competent Miata owner (in a local club) could have had it switched out for you within a day for the cost of lunch or something...

Winter driven Canadian Miatas are not that kind to the rear subframe, there was a good chance that if it came out it would not go back.

If I had driven it it as a daily it would not have been salvalgable when I was done with it. At least at this point someone can still easily put a fuel cell in the trunk and still have years of fun summer driving it.