great video Greg, there's a few things i will add tho...instead of ABS plastic, I'll be going with 3/8" thick high density polyethylene. this stuff can bend in a complete "V" and not spider crack. it's UV resistant and has memory. it will always go back to its original shape should you hit something or bend it...i would use washers on your oval holes, it will help with clamping force. lastly, when i build mine, I'll take it back apart to have each piece hydro dipped in carbon fiber. I'll be using some of these techniques when i build a diffuser and splitter for my mustang 💪
@@itz-amemario426 oh wow really? I'm not an expert, but i liked the properties of PE. can you explain why it's not good for street cars and race cars? thanks
@@PANTYEATR1 It isn't bad, It just wouldn't be my first choice. ABS is stiffer and tougher, it has decent heat resistance and you can easily glue and weld it. You can form ABS using heat. PE is softer, it deforms permanently. PE is good for stuff like paddings, bushings, gaskets, or non stick surfaces, so food processing or linings. That being said I wouldn't bother with either and go straight to aluminium or alumalite.
@@itz-amemario426 thanks for your reply. i choose the PE cause it has impact resistance and it returns to the original form if a parking curb or speed bump was hit. in cold/hot weather temps, i don't know if ABS could handle those issues without chipping. since this will be on a street car, i wanted something that could handle the imperfect habitat of the streets. if it was a race car only, aluminum or alumalite would be an option. i don't recall the thickness of the ABS used in the video, but I'll be using 3/8" thick PE. I'll run the information mentioned through the plastic store expert and see what they say. if ABS is good enough, I'll buy that. i know it's definitely cheaper.
Tip: run a finger along the length of the fin to even out the bead of silicone. Best way to get a nice even finish. Learned that from home renovations. I looked for a good tool for a bit the first time I did caulking and then I saw a couple videos and realized the best tool was attached to my body already :)
First off thank you for taking the time from your everyday life and dropping all the legit content you put out. I admire your passion for the MX5 , much respect for what you do.
greg it's called flatbar! also, use simplegreen and spray it onto your caulk bead then run your finger across it. i promise it'll look a lot better than the screwdriver method lol
It’s defo getting done... was gonna go the omg miata way but this is much more home brew.. and not as time and money consuming 👌🏼👌🏼💪🏽 for when I fuck it up on track
Another project to add to the list! What is the butt dyno telling you about its effectiveness and do you think you will be able to see a difference via Dragy runs?
So, you cut the bumper so that it doesn't catch air and then you essentially put a scoop that shoots air up into your bumper. ... hmmm.... looks cool! :)
No, the majority of the air will be prevented from flowing up into the bumper from the diffuser (ideally, there'd be more panels covering the diff and drive shaft of course)
The majority of the air under the car will flow on the underside because there's more space there. But that was true before the bumper cutout. This thing is still scooping a lot of air up into the bumper.
You should have cut slits into the flat plastic base, pushed the fins through those slits and mounted them underneath so you can't see any of the screws!!! All of those screws are disrupting air flow. Why do you think they filed all of the bolts on aircraft, surface smooth??? And it would not only work much better in a practical application, but would also look a lot more professionally done.
If you cut each fin with multiple tabs. The tabs could fit up through the slot in the main sheet (instead of putting a bracket down through each slot) then the brackets can still be used to attach them but you don’t see so many bolts on the outside. Cutting the fins would be much more fiddly but the overall look would be neater. Just a thought 🤟
I would just paint the entire thing wrinkle black in the end, then u dont have to see the silicone that fills the air gaps and u also dont have to deal with having a smooth and textured look. Also maybe black hardware would make it a little easier to see the actual lines of the diffuser. The silver hardware is a little distracting. Looks fantastic otherwise.
Looks great and I'm sure it will have aero benefits as it's similar in total area, length, and angle to other diffusers on the market that have been tested. Some other beneficial supporting aero mods would be flat paneling the bottom as much as feasibly possible(can also be done with abs plastic) as well as an under tray/front splitter. You'll easily see some testable benefits if you do all that.🏁🏁🏁
KPower Industries is ready for you! I have their BMW transmission swap kit in my car. Heavily contemplated doing a K Series Miata, the engines are just so good even in factory form
@@TheCarPassionChannel yea I’m a Honda guy and love the k series engines lol. The first advertised swap kit I seen was from k Miata. I’ll have to do some research and see which one fits my type of build lol.
Nerdy comment about using 1 fin for tracing all other fins vs tracing each fin off of its predecessor; that's a brilliant example of error propagation! 1% error on tracing and cutting each fin successively = 1.01*7 = 1.07, or 7% error by the time you've cut out fin #8. Compare that with 1% error if you were to trace fins 2-8 directly from fin #1. Pretty neat!
Great job Greg! Adds an amazing look. Me personally, if I ever do this, I would give the hardware a quick spray of black paint because I don’t like the “studded” look the hardware gives being silver. But hey, none the less, this is an AWESOME template that people are going to be able to use to make their own, perfect to them, diffuser. Thanks for bringing the knowledge and showcasing it for us.
I think Flat undertray would make this diffuser way more efficient, also entire car way less aerodynam... I mean less aerodragic. Like flat under engine tray, following the contours of the lip of the bumper, following with entire trans, driveshaft, diff cover plate should increase the flow of air around(or atleast under) the car.
cant really do that since everything is air cooled. you would need a cooler for the trans, diff, engine or just make ducts under the car that funnel air to the fins on the oilpan, trans and differential
Like FatalGaming said, I'm not sure if that hurts the cooling too much, but additionally this diffuser is wayyyy too steep to be effective as an aerodynamic device. Diffusers are usually pretting long and pretty flat because the ariflow needs to stay attached in order for the diffuser to have the necessary expanding effect on the underbody airflow
one thing I would change immediately in my build are the screws. first off black screws (optional), but most importantly I would use the sleeved type of screw/nut combo with flat head that screw into each other and you end up with two flatheads on both sides with nothing sticking out. Rivets would do the same job, but then its harder to adjust or pull apart/replace damaged fin. other than that sweet vid, thanks :)
@@berniehayhurst1811 oh, didnt mean rivnuts, did a quick search for those im thinking of and funnily enough, they are called sex bolts or chicago screws :)
Tip, about the silicon instead of using the screwdriver. Take some soap water dip your finger and just smooth it out, will not stick to the skin and looks better.
Yeah since I planned to do pretty much full voiceover I didn't bring any mic setup with me lol. Combine that with a small room where all 6 surfaces are hard and you get meme level echos
Would love a vid with some A/B testing to see if this thing works. I guess there is no easy way to see if it prdouces some downforce, but maybe some 100 - 200 kph pulls to see if drag is reduced.
Ok I get it I don’t have any friends thank you for reminding me. Also I recommend aluminum composite, it’s more stiff and rigid and holds bends and won’t flex plus you can make it thinner for less weight. My diffuser in 1/8 inch thick.
Looks good but if you want any real function it must stick out away from the bumper lease 4 inches or its pointless. Your setup looks good tho with function good distance.
So what are your thoughts on skipping the heat deflecting sheets or mounted embossed aluminum heat deflecting sheets in lieu of simply covering everything axle back with ceramic fiber wrap? I understand that wrapping is rarely a good option for a street vehicle, but if the fab'd diffuser shields the muffler so much that it requires heat deflection to avoid damage, should it not also shield the muffler from the water and road grime coming from the other side of the diffuser as well, thus making the main caveat of the wrap (fluid retention and consequent rust) no longer a caveat?
i really hope we will se more underbody aero, it deserves more when you now have the ball rolling :). Check Julian Edgards youtube channel to get some ideas on how to easily DIY measure if the aero is working.
Funny thing is, its been proven that bumper "parachute effect" isn't a real thing. CFD simulations show that a stock bumper is better than a cut bumper or a Honda fan boy drilled bumper or a poorly designed diffuser. On the street, it doesn't matter either way. On the race track, you may notice hundredths a lap.
will you perform a string test to see how well airflow follows under the diffuser? i mean, tape some string or yarn to the diffuser on the rear part of the strakes and plane, point a gopro at the string (keeping the camera out of the airflow) and check to see that the strings are pulled straight back in laminar flow instead of being pulled randomly in turbulence. this can show if the upward sweeping angle of the diffuser is too steep.. in that case the airflow will be stall-like and turbulent.
Looks good, I have thought about doing this but I am too afraid to do a bumper cut. Looking at the process you guys used I think you could have made your life a little easier if you would have used a heat gun to relax the plastic.
The idea and build is awesome but the diffuser is basically pointless as the underside of the Miata is not smooth, so that means that the air will get dirty before it hits the diffuser and it won't help. Do a smooth underside before a diffuser and that smooth underside helps a lot more than the diffuser right now
are the bolts more better and more secure than something like plastic welding? I was thinking that potential money could be saved using a plastic welder.
You should do a test with some wool ropes and tape + GoPro to see if the flow is attached. What's the weight? Do you feel any difference? Looks sick ;)
Great DIY! I strongly advise you to add some kind of rigid brace joining two rear mounting points and connect central section of the diffuser to that brace. Aluminium angle or square tube is first thing that comes in mind for this. Because it seems that it might not hold for too long if it really works and will be able produce any significant downforce. Ant it looks like it really can! ;) Shape of the diffuser definitely provides some rigidity, but abs+exhaust heat+force applied will probably bent it out of shape over time. Ideally you can use fins mounting bolts to hook central section to the brace.
Not only miata dad helps us make our miatas fast but he also helps us get that street cred
I cant wait to make this diffuser for my gaming chair
buying home depot stocks now before miata nation descends on the aisles
LMFAO. truth.
STONKS
great video Greg, there's a few things i will add tho...instead of ABS plastic, I'll be going with 3/8" thick high density polyethylene. this stuff can bend in a complete "V" and not spider crack. it's UV resistant and has memory. it will always go back to its original shape should you hit something or bend it...i would use washers on your oval holes, it will help with clamping force. lastly, when i build mine, I'll take it back apart to have each piece hydro dipped in carbon fiber. I'll be using some of these techniques when i build a diffuser and splitter for my mustang 💪
Good to know man, thanks for the heads up!
Actually ABS is way better for that purpose than PE.
@@itz-amemario426 oh wow really? I'm not an expert, but i liked the properties of PE. can you explain why it's not good for street cars and race cars? thanks
@@PANTYEATR1 It isn't bad, It just wouldn't be my first choice. ABS is stiffer and tougher, it has decent heat resistance and you can easily glue and weld it. You can form ABS using heat. PE is softer, it deforms permanently. PE is good for stuff like paddings, bushings, gaskets, or non stick surfaces, so food processing or linings. That being said I wouldn't bother with either and go straight to aluminium or alumalite.
@@itz-amemario426 thanks for your reply. i choose the PE cause it has impact resistance and it returns to the original form if a parking curb or speed bump was hit. in cold/hot weather temps, i don't know if ABS could handle those issues without chipping. since this will be on a street car, i wanted something that could handle the imperfect habitat of the streets. if it was a race car only, aluminum or alumalite would be an option. i don't recall the thickness of the ABS used in the video, but I'll be using 3/8" thick PE. I'll run the information mentioned through the plastic store expert and see what they say. if ABS is good enough, I'll buy that. i know it's definitely cheaper.
Tip: run a finger along the length of the fin to even out the bead of silicone. Best way to get a nice even finish. Learned that from home renovations. I looked for a good tool for a bit the first time I did caulking and then I saw a couple videos and realized the best tool was attached to my body already :)
First off thank you for taking the time from your everyday life and dropping all the legit content you put out. I admire your passion for the MX5 , much respect for what you do.
Beautiful work sir!
Such diffuse. Very airflow. Wow.
Use a woodburning tool and abs zip tues to platicweld it instead. Do it outside or with good ventilation.
Nice project!
I agree that some rough edges and no smooth silicone kit gives it a nice racing-touch. A lot of work, but:
Well done. 😮
greg it's called flatbar! also, use simplegreen and spray it onto your caulk bead then run your finger across it. i promise it'll look a lot better than the screwdriver method lol
looks great, but the top sheet should be made of a sheet of aluminum to avoid melting on catching fire =P
Pretty solid. Came out nice. Going to attempt to make one for my 17 Hyundai Sonata Sport 2.0T
Looks great. Pro tip: wet your index finger and run it over the silicone bead to smooth it out. (P.s. when did you get those slicks!!!)
It’s defo getting done... was gonna go the omg miata way but this is much more home brew.. and not as time and money consuming 👌🏼👌🏼💪🏽 for when I fuck it up on track
Holy cow! Your car has a nice caboose.
Go to Marshall's hardware for all you nuts and bolts, they are in Miramar. They have a crazy selection and great prices and no I don't work there.
Greg spray da boltz! Looks sick tho, those fat tyres make it look nutty
So sick!
Super rad, good job man!
Badass build guys where can I get the plastic to make ine of my own.?.
I love this so much. Can’t wait to try it out on my car
Finding this 2 years later, how'd it hold up? Long term review?
10:33 - It's commonly called flat stock. Just FYI. 😉
Just curious why you didn't rivet the vanes to the support brackets? Why nutless bolts?
Awesome!You are the best.
Yeahhh fresh content 😍😍😍
Man, a tiny bit of red spray paint on that but if white where you cut the melty bit off the bumper would go a loooong way..
Amazing
Don’t use a flat head for the silicone! Use an old paddle pop stick or run your finger down it
Another project to add to the list! What is the butt dyno telling you about its effectiveness and do you think you will be able to see a difference via Dragy runs?
So, you cut the bumper so that it doesn't catch air and then you essentially put a scoop that shoots air up into your bumper. ... hmmm.... looks cool! :)
No, the majority of the air will be prevented from flowing up into the bumper from the diffuser (ideally, there'd be more panels covering the diff and drive shaft of course)
The majority of the air under the car will flow on the underside because there's more space there. But that was true before the bumper cutout. This thing is still scooping a lot of air up into the bumper.
@@umakegoodcookies fix it by adding a pool noodle ....;-)
Only if broke and boosted had this...look so sick tho!
I'm so making this the entire length with holes for the exhaust in the diffuser
Epic indeed! Very race car.. still owe you a pig out sesh. Ps I agree with the rivet comments but that may require extra tooling cost
You should have cut slits into the flat plastic base, pushed the fins through those slits and mounted them underneath so you can't see any of the screws!!! All of those screws are disrupting air flow. Why do you think they filed all of the bolts on aircraft, surface smooth??? And it would not only work much better in a practical application, but would also look a lot more professionally done.
Looks cool. Any idea what it weighs?
I would guess less than 10lbs, can easily lift it with my pinky
@@TheCarPassionChannel thanks. You’re doing the community a great service. Keep it up!
only thing I hate is the exposed hardware could maybe paint them black
KYLE.ENGINEERS makes some steller vids if you want to learn how to optimize your diffuser for real downforce.
Thanks
now i only have to spend a couple hundred more on all the tools
Damn it dad now I’ve gotta spend more money on the five this month 😅
hell yeah
how much does this thing weigh?
If you cut each fin with multiple tabs. The tabs could fit up through the slot in the main sheet (instead of putting a bracket down through each slot) then the brackets can still be used to attach them but you don’t see so many bolts on the outside. Cutting the fins would be much more fiddly but the overall look would be neater. Just a thought 🤟
I would just paint the entire thing wrinkle black in the end, then u dont have to see the silicone that fills the air gaps and u also dont have to deal with having a smooth and textured look. Also maybe black hardware would make it a little easier to see the actual lines of the diffuser. The silver hardware is a little distracting. Looks fantastic otherwise.
Seriously badd ass!
Looks great and I'm sure it will have aero benefits as it's similar in total area, length, and angle to other diffusers on the market that have been tested.
Some other beneficial supporting aero mods would be flat paneling the bottom as much as feasibly possible(can also be done with abs plastic) as well as an under tray/front splitter. You'll easily see some testable benefits if you do all that.🏁🏁🏁
Use ACM and it won’t melt
im here dad
Damn I miss my Miata. Once I’m done with my move, I have to get another one. I want to ruin one with a Honda k series lol
KPower Industries is ready for you! I have their BMW transmission swap kit in my car. Heavily contemplated doing a K Series Miata, the engines are just so good even in factory form
@@TheCarPassionChannel yea I’m a Honda guy and love the k series engines lol. The first advertised swap kit I seen was from k Miata. I’ll have to do some research and see which one fits my type of build lol.
@@aaronpratt89 Same company 👍 they changed their name from KMiata to KPower Industries once they started progressing with E30 and BRZ swap kits
@@TheCarPassionChannel 😳😳 well I guess that settles that!!! Hell yea!
When the next time your going to the track
But does it work?
When are you gonna do a ca legal ecotec swap? lmao Ill be dreaming of the day that happens
I love you
@11:32 The word you are looking for is aluminum flat bar
That "steel" you have there certainly has the thickest aluminization I've ever seen...
Nerdy comment about using 1 fin for tracing all other fins vs tracing each fin off of its predecessor; that's a brilliant example of error propagation!
1% error on tracing and cutting each fin successively = 1.01*7 = 1.07, or 7% error by the time you've cut out fin #8. Compare that with 1% error if you were to trace fins 2-8 directly from fin #1.
Pretty neat!
That’s why you use the same fin for each tracing
Edit: well actually you literally just said that so lmao
It's like the fabricators version of the telephone game lol
Why not use shorter screws so they don’t stick out sideways?
Rivets!
@@mixalisstathis274 my thoughts exactly!
@@winguard96 if it gets damaged bolts make it easier to fix ;) but saying that i do like the sound of Rivets
Is that parking lot at the end the same one from the “stolen” hardtop video?
Finally the diffuser vid!
Great job Greg! Adds an amazing look. Me personally, if I ever do this, I would give the hardware a quick spray of black paint because I don’t like the “studded” look the hardware gives being silver.
But hey, none the less, this is an AWESOME template that people are going to be able to use to make their own, perfect to them, diffuser. Thanks for bringing the knowledge and showcasing it for us.
Saaaaame
If you do this mod in germany, you‘re going to jail. Modding cars in US is so much easier
Yeah getting this past the tüv would be a nightmare. Such a shame, it looks really good.
Whenever I have a bad day I watch the Car Passion Channel... Then Happiness
I think Flat undertray would make this diffuser way more efficient, also entire car way less aerodynam... I mean less aerodragic. Like flat under engine tray, following the contours of the lip of the bumper, following with entire trans, driveshaft, diff cover plate should increase the flow of air around(or atleast under) the car.
cant really do that since everything is air cooled. you would need a cooler for the trans, diff, engine or just make ducts under the car that funnel air to the fins on the oilpan, trans and differential
Like FatalGaming said, I'm not sure if that hurts the cooling too much, but additionally this diffuser is wayyyy too steep to be effective as an aerodynamic device. Diffusers are usually pretting long and pretty flat because the ariflow needs to stay attached in order for the diffuser to have the necessary expanding effect on the underbody airflow
Can’t wait to see every lowered Miata with one of these now 😂
This feels like an architecture project, fun stuff greg, great video!
Gotta clean them up the RWB way and run your finger over the silicone lol
Only part that bothered me. Lol
subscriber since the old 1.6, i'm amazed by how much this mx5 has evolved, inspired me to get my own and work on it, miata dad is the f goat.
Completely off topic: from the looks of the back tires, you are having a lot of fun with the car. Yay!
He did this vid before going to the track. His track video had the diffuser on the car already.
Be that as it may, its a "getinsitdownshutupholdon" kinda car that makes it so awesome.
one thing I would change immediately in my build are the screws. first off black screws (optional), but most importantly I would use the sleeved type of screw/nut combo with flat head that screw into each other and you end up with two flatheads on both sides with nothing sticking out. Rivets would do the same job, but then its harder to adjust or pull apart/replace damaged fin. other than that sweet vid, thanks :)
They are called "Rivnuts" in aviation.
@@berniehayhurst1811 oh, didnt mean rivnuts, did a quick search for those im thinking of and funnily enough, they are called sex bolts or chicago screws :)
Are you going to have to put in a full under-tray to keep air from going between the car and the diffuser ?
Angle iron, but it aint iron nor angled
Hahahahaha just thought it was funny
Now I got to make one out of aluminum and flush rivets
Tip, about the silicon instead of using the screwdriver. Take some soap water dip your finger and just smooth it out, will not stick to the skin and looks better.
Bro, watching the first bit of the video sounds like Im watching a video back in like 2008 😂
Yeah since I planned to do pretty much full voiceover I didn't bring any mic setup with me lol. Combine that with a small room where all 6 surfaces are hard and you get meme level echos
Would love a vid with some A/B testing to see if this thing works. I guess there is no easy way to see if it prdouces some downforce, but maybe some 100 - 200 kph pulls to see if drag is reduced.
Ok I get it I don’t have any friends thank you for reminding me. Also I recommend aluminum composite, it’s more stiff and rigid and holds bends and won’t flex plus you can make it thinner for less weight. My diffuser in 1/8 inch thick.
Looks good but if you want any real function it must stick out away from the bumper lease 4 inches or its pointless. Your setup looks good tho with function good distance.
So what are your thoughts on skipping the heat deflecting sheets or mounted embossed aluminum heat deflecting sheets in lieu of simply covering everything axle back with ceramic fiber wrap? I understand that wrapping is rarely a good option for a street vehicle, but if the fab'd diffuser shields the muffler so much that it requires heat deflection to avoid damage, should it not also shield the muffler from the water and road grime coming from the other side of the diffuser as well, thus making the main caveat of the wrap (fluid retention and consequent rust) no longer a caveat?
i really hope we will se more underbody aero, it deserves more when you now have the ball rolling :). Check Julian Edgards youtube channel to get some ideas on how to easily DIY measure if the aero is working.
It ain't perfect but it looks so good! ❤
Funny thing is, its been proven that bumper "parachute effect" isn't a real thing. CFD simulations show that a stock bumper is better than a cut bumper or a Honda fan boy drilled bumper or a poorly designed diffuser. On the street, it doesn't matter either way. On the race track, you may notice hundredths a lap.
will you perform a string test to see how well airflow follows under the diffuser? i mean, tape some string or yarn to the diffuser on the rear part of the strakes and plane, point a gopro at the string (keeping the camera out of the airflow) and check to see that the strings are pulled straight back in laminar flow instead of being pulled randomly in turbulence. this can show if the upward sweeping angle of the diffuser is too steep.. in that case the airflow will be stall-like and turbulent.
Paint the bolts black
Wanting to do this to my car except with a center exhaust and rear defuser made out of aluminum Tig welded. Coming soon on my channel?
I can tell you have never caulked a bathtub. Great video though! I will surely need it!
Good thing diffusers don't need to be waterproof ✅
@@TheCarPassionChannel But you could have used the skills to make the silicone clean. Not trashing you, just my opinion. Thanks for the reply
Looks good, I have thought about doing this but I am too afraid to do a bumper cut. Looking at the process you guys used I think you could have made your life a little easier if you would have used a heat gun to relax the plastic.
Just a thought but I'd be swapping the bolts and nuts holding the fins for rivets. Some black ones would be much less visible
Im seeing a Diffuser in my Miata's future, that is once Home Depot replenishes stock Miata Nation must have descended on my local store :D
The idea and build is awesome but the diffuser is basically pointless as the underside of the Miata is not smooth, so that means that the air will get dirty before it hits the diffuser and it won't help. Do a smooth underside before a diffuser and that smooth underside helps a lot more than the diffuser right now
Wrapping your muffler with manifold tape would have looked bad ass too. 🔥🔥🔥
Good work, but if you want it to actually do anything other than add weight, you need to add a flat floor :-)
are the bolts more better and more secure than something like plastic welding? I was thinking that potential money could be saved using a plastic welder.
Brother I know its an older vid, but man that shit is popping!!!! maximum street cred!!!!
That transmission getting caught on the intro tho!! 😅 all jokes aside, good job guys! 👍🏼
You should do a test with some wool ropes and tape + GoPro to see if the flow is attached. What's the weight? Do you feel any difference?
Looks sick ;)
Next up, flat floor... otherwise this was totally useless (not counting street cred) :)
Hey miata dad and followers dose anyone by chance know the length of the 1.8 engine with and with out the standard gearbox
Goddamn, the abs will be out of stock for weeks🤣
0:07 i think we just found out what minecraft steve looks like irl (right)
Great DIY!
I strongly advise you to add some kind of rigid brace joining two rear mounting points and connect central section of the diffuser to that brace. Aluminium angle or square tube is first thing that comes in mind for this.
Because it seems that it might not hold for too long if it really works and will be able produce any significant downforce. Ant it looks like it really can! ;)
Shape of the diffuser definitely provides some rigidity, but abs+exhaust heat+force applied will probably bent it out of shape over time.
Ideally you can use fins mounting bolts to hook central section to the brace.