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Mikelly

Looking for a few good candidates (And their money)

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I assure you there is no controversy, I just don't see any reason to attach plywood to the bottom of my car in a fashion that would not exactly duplicate what I would actually have on my car on the track. Let me assure you that an engineer or aerodynamicist has never in the history of time just attached some plywood to the underside of a modern race car to see the data in a wind tunnel, when they use cad programs to design every piece on the car and simulate the aero in a virtual tunnel before they fabricate exactly the under-tray that is ultimately the best treatment for the car given the data supplied prior to ever even fabricating the first piece on the car.  I want my car to be as slick as I can. I would love to smooth out the bottom of my car and create more downforce, however, in understanding how an actual flat bottom tunneled car works, it would require a total redesign of "MY" car. I also understand clearly the advantage of power to weight ratio's and would prefer my car to be as light as possible. I constructed the front splitter, the side skirts and the wing to help air lay on top of them at speed and through practical, on track application, I have found them to be helpful to me. 

 

The reason to do it is to see what the results are before you go and redesign your whole car. If the effect is good enough, it might be motivation to go for it and really make that sort of change on your car. Have you ever heard of Simon McBeath? He does the Aerobytes column for Race Car Engineering and wrote Competition Car Aerodynamics and Competition Car Downforce, and he tries stuff on the fly in the tunnel all the time. I've never seen him test a whole floor that was plywood, but he makes parts from cardboard, wood, etc and tapes them to the car to test in the tunnel. Seen articles where he modifies fenders with cardboard, blocks off grill openings and ducts with cardboard, cut holes in fenders with a cutoff wheel, carboard extensions on diffusers, etc. He has done that kind for years, check out some of the old back issues of RCE and you'll see what I'm talking about. He also does CFD and has a company that manufactures wings. I remember Hot Rod Magazine did a LSR car and they had all kinds of crap taped all over it, including the airdam and the hood scoop. After optimizing in the tunnel and then actually mounting the parts, it ended up going 250+ mph and they were able to get the Cd from something like .5 to .22 on their late 60's Camaro. Halfassing it in the wind tunnel makes sense because you can see what works before you put the time and effort into making it permanent. That's the beauty of the wind tunnel.

 

I'm just making suggestions, and it seems like there is a lot of pushback and I'm not understanding why. FWIW though, I've seen flat floors on cars that weren't designed for them and it's not as impossible as you're making it out to be, especially with as much ground clearance as you have. Chris Rado's AWD Scion comes to mind. It had a dropped panel that was probably 4" lower than the floor to avoid all the drivetrain crap underneath the car, and to get the floor down to where it would actually do some good. You or anyone else could fairly easily attach plywood to the bottom of the car to create a flat floor, test it, then take it off and have maybe a few extra nutserts in the chassis or something like that. That's the beauty of the tunnel. It doesn't have to be "right", it just has to be there, and this piece would be easy because it is flat. Anyone could make a flat panel the right shape in 1/2 hour with a jigsaw, then it needs only to be mounted it in the most rudimentary fashion to the car. Do a very simple diffuser, just a 7* angle and see what happens.

 

As to the applicability of this idea to your car, it appears to me that you have plenty of room to drop a floor down to 2 or 3 inches off the ground. If you ran droop limiters you might even have enough clearance to go under all the suspension arms. The windspeed in the tunnel is 80mph as I recall, so I don't think you're likely to be developing huge amounts of downforce. 

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 I have often envisioned a flat bottom 240Z. If you go and try and smooth it out and add a diffuser it actually works against you. I don't need a wind tunnel to tell me that, I've tried it on the track. To make my car a flat bottom, a functional flat bottom, not a smoother undertray that works around all the crap that is under my car, it would actually require a total redesign of the car.

 Nice post, good info

 

 

Why does an undertray and diffuser work against you? What does it do wrong?

 

What would have to be redesigned on a 240Z to make it work?

 

 

I may have something to donate to this cause in the near future.

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 Nice post, good info

 

 

Why does an undertray and diffuser work against you? What does it do wrong?

 

What would have to be redesigned on a 240Z to make it work?

 

 

I may have something to donate to this cause in the near future.

Chris,

 

I would love to make my car flat bottomed. I would however approach it in a way that the underwing and diffuser actually worked and didn't resemble a flatbottomed car. I see loads of people who attach panels to the underside of a car, I see people buying diffusers all the time and not actually realizing that they are not doing anything but adding weight and drag to the car. The purpose of the diffuser is to allow the air that has been accelerated by the front splitter and undertray and due to that air being accelerated it creates a lower pressure area under the car and causes downforce to occur. The diffuser decelerates the air back to as close to the same speed that existed in front of the car originally. If a diffuser is designed in a wind tunnel or in a CMG virtual program it can then maximize the downforce and create less drag for the underwing. I point out that the undertray or flat bottom is simply much more than a large piece of plywood attached with clamps to the underside of my car. Thats fu@#ing stupid...........Could I redesign the underside of the car and create a functional flat bottomed underwing that had a functional diffuser. Yes I could. Do I have the time and money to undertake such a project, NO. I also contend that I am having a real problem with certain individuals that have all the advise of an armchair quarterback and no real practical sense of what is involved in actual application. I also wonder why does this data actually matter, when no one really has the need for such data. There are maybe a handful of people on the planet that actually would benefit from a functional tunneled undertray and diffuser for a 240. If you take that myself and only a few other individuals actually race these cars in a division that no build rules apply, anyone racing in any vintage division could not do anything with this data or application. At present, if I can get my car to the finish line in a 1 hr sprint race without something breaking I usually have a good chance at winning the race overall. That's really difficult to do and very satisfying when it happens, however if I were to redesign the underside of the car and do all this work and pay for it all, just so we can go to the windtunnel and a few curious people can see the data, well once again I see that as a waste of my time and money. An old saying is that "The juice is not worth the squeeze". If I had an unlimited amount of money and I really thought that this would make a difference worth the investment, I would probably do it. If I had an unlimited amount of money and could do whatever I wanted I probably would be racing at LeMans next week and not on Hybrid Z forum.

 

If I were to spend money wisely and do the next step in the evolution of my car and do something I know would make it even more competitive is the suspension and brakes. I am presently working on fitting adjustable shocks and a MTI Racing big brake kit off of one of our Corvette race cars. That would be the wheel hubs and all. Just take the geometry that already works and I am familiar with and make it work under my Z car. The need to stop my car, to take it deeper into turns, to keep the brakes functional for longer periods of time, to make it stronger, smoother, more stable, better balanced, adjustable, etc.... You get the picture. I assure these items are 100% more important and relevant to my build than trying to attach plywood to the bottom of my car in a windtunnel.

 

If anyone disagrees with me, I am no stranger to confrontation or controversy, I support your decision to take your car and your plywood, at your expense ($425 hr) to the windtunnel and supply me with the data.

 

For the record............."I've been told that I'm really a nice guy in person".

Edited by cobramatt

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That's a lot of words for not really answering my questions.  ;>)

 

""I would love to make my car flat bottomed. I would however approach it in a way that..... didn't resemble a flatbottomed car.""

 

this makes no sense to me.

 

""I see loads of people who attach panels to the underside of a car, I see people buying diffusers all the time and not actually realizing that they are not doing anything but adding weight and drag to the car.""

 

I don't see very many people doing this. Of all the build threads I've read in the last 7 years I think there are 2 that did underpanels.

 

Assuming you are talking about aftermarket diffusers, my main question is, you say they don't work, WHY do they not work?

 

I understand the concept of an aftermarket part that has no benefit and in fact may be detrimental. Like a front strut brace with big kinks in it is doing nothing for rigidity. But you haven't explained what makes these bad diffusers and underpanels bad and you haven't explained what makes a good underpanel/diffuser work properly.

 

"" I point out that the undertray or flat bottom is simply much more than a large piece of plywood attached with clamps to the underside of my car. Thats fu@#ing stupid..........""

 

The concept of plywood is just as a mock up. I don't see why plywood if it was done right wouldn't work for the flat areas of the under panelling. I've seen a RUF underpaneled Porsche, it was completely flat to behind the rear axle. The diffuser section after that curves smoothly upwards, I don't really think it's rocket science. Seems to me that was what a Ford GT looks like also, nothing all that complex.

 

"" I also wonder why does this data actually matter, when no one really has the need for such data. There are maybe a handful of people on the planet that actually would benefit from a functional tunneled undertray and diffuser for a 240.""

 

Define benefit. By this definition nobody needs a hybrid Z, it's just being done for the sake of doing it. I want a Z with a flush bottom and a functioning diffuser. I'm never going to race but I just like the idea of having it. Heck I might want to go fast and it would be nice to have solid functioning aerodynamics.

 

I think a lot of people benefited from the last wind tunnel test, don't see why that couldn't happen again.

 

Just an FYI, Solidworks has CFD software embedded, even in the base version, and it's not that hard to use. It would take a while to accurately model a Z but it's probably already been done.

 

 

 

 

 

 

Edited by Chris Duncan

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 I see loads of people who attach panels to the underside of a car, I see people buying diffusers all the time and not actually realizing that they are not doing anything but adding weight and drag to the car.

So am I correct in asserting that the reason you are so virulently opposed to the flat bottom idea is that plain old flat bottoms with plain old diffusers don't work? That seems to be the only line of reasoning to answer Chris's question. 

 

In Competition Car Aero McBeath used CFD on a NASCAR model to simulate a flat pan under the engine and cabin. No diffuser, no wing, not even a splitter. Just flat panels starting at the nose and continuing under the engine and cabin on an otherwise non-optimized car. Panels stop at the rear suspension. Result: 6.5% increase in downforce, 1% reduction in drag. McBeath also said in an email to me that I should panel as much of the underside of my Z car as possible, even if I could only get the engine compartment done. The email is in my splitter/airdam thread if you're interested. 

 

In Race Car Aero Katz examines a 1991 RX7 GTO car with flat floor and simple 6 degree diffuser and says that the published L/D for the car was -.3 to -.4, which is much better than anything that went through the wind tunnel last time. He also says that with a little more attention to detail and room to maneuver with an open ruleset it probably could have generated -1. In looking at this book again, it must be where I got the idea for the diffuser fed with a duct opening in front of the rear tires, as he describes air rolling under the RX7 and increasing the performance of the diffuser. Damn. I really thought I came up with that myself. He didn't describe fences on a flat bottom to make a venturi though. I think that one is an original...

 

I've read other books on aero, but these are the ones I own and can check right now, but so far I'm 2 for 2 in general principle. Obviously I can't make you do anything and I don't want to, but your irritation with my line of reasoning doesn't seem to be an appropriate response to the way I'm approaching the subject and doesn't really fit with anything I've read re: aerodynamics. 

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So the title of this thread was "Looking for a few good candidates and their money."  I've not started to collect donations for this effort yet, and I'd be just fine with not collecting donations.  Jon, You seem like you're hell bent on dictating what we will and won't test.  For the record, Matt's comments above MIRROR those of the wind tunnel operator during the last test.  Now he didn't write a book on competition car aero, but the guy works in a windtunnel every day with ALL the NASCAR teams located in the region.  His comments were simple.  it's a dirty unibody chassis that was NOT designed for the advances seen in current auto platforms.  likeing a 40 year old platform to a tube chassis nascar platform is a waste of text so lets just stop with the comparisons. 

 

 

Now, Matt and I, and others who are willing to spend the money and time to roll their cars thru the wind tunnel will take ideas and suggestions, but quite honestly, unless you want to get a group together and run your own tests, take the hint and back off on an idea that those conducting the test aren't hot on wasting valuable time to try.  I'm not saying there won't be flat bottom panels associated with my car or a difuser.  I am actively in the process of welding Dzeus fasteners to the chassis this coming week.  I plan to fabricate an NUMBER of aero ideas that I plan to try, just to collect the data.  Give us a chance to come up with our OWN plans since we will be the folks spending OUR OWN MONEY.  Matt Isbell is doing more with this chassis than anyone else I'm aware of.  I'll defer to his judgement any day and twice on Sunday.

 

Chris, to your comments, I believe Matt was referring to what he sees any given weekend on other platforms.  And if you follow any of the aero articles in GRM, you'll see those examples displayed.  You are a smart guy, and you know well that what sometimes seems like a good idea in theory sometimes falls flat.  So the point is that we will have very limited time in the tunnel.  As with last time, we'll need to be practical in our approach.  i'm not certain that we'll be able to pull off a number of verying and difficult tests while collecting data that each of the car owners needs for their specific application as well. 

Edited by Mikelly

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I've got bigger fish to fry today guys, should have a new baby here in a couple hours. Suffice it to say that I'm in no position to demand anything of you, and that you're in position to ignore me if you so choose. I only persist because I think you're wrong, just like I thought the wind tunnel operator was wrong that splitters and rad ducts don't work on Z cars. I will donate if given the opportunity, and I will read through the numbers after the fact like a kid on Christmas morning.

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The wind tunnel operator was the reason my radiator IS ducted and that I have my front end configured the way it is.  I think something was lost in the translation somewhere, but everything he advised I took to heart and am trying to translate onto my own chassis.  I WILL try the front, mid and rear panel closeouts on my car if possible, if for no other reason, than to put this discussion to bed once and for all.

 

Mike

Edited by Mikelly

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Wife is on a monitor for a couple hours. Past this point I'm just going to back off and throw some money at you guys. 
 

http://forums.hybridz.org/topic/55913-windtunnel-testing-the-datsun-s-30-z/

 

Me: I know you guys were keen on blocking the open space between the air dam and the rad core support. Was there any attempt on any of the cars to seal the top of the core support to the underside of the hood?

 

You: Jon M., We didn't test any advanced airboxed. We tried to stick mostly with basic stuff.

 

You again: Well lets backtrack to the other comment you made for a second... You're worried about an extravigant sheetmetal box for the radiator, but you missed the whole section on how the radiator only needs 2X4 inches of space to stay cool... That sheetmetal "box" is probably effective at doing that, but probably isn't as big of an aerodynamic aid as you might think, so you have to think in different terms there.

 

Me: I'm not sure you're getting the point of the box. It isn't only there to limit the amount of air coming into the radiator. That is it's less important purpose. It's more important purpose is to eliminate the pressure from the underside of the hood. And this ties in with the other question as well, about sealing the core support to the hood.

If you have positive pressure inside the nose of the car and have not sealed the core support to the hood, then presumably just as the air can go down underneath the airdam under the car, the air can also go OVER the rad core support and through the holes in the core support as well. This will increase the amount of pressure under the hood.

If one were to do the box structure and seal the hood to the grill area so that all the air that went into the box went through the radiator, then you'd get a couple of benefits. You guys already showed that cutting down the amount of air is beneficial. In addition though, you'd cut down the size of the pressurized area in the front of the car. In fact, you could probably get negative pressure in the front hood area above the box. Negative pressure under the hood, coupled with the pressure of the air being diverted over the hood = more downforce, and that's why you see so many race cars using that type of radiator duct. If memory serves I think preith has this type of setup on his car, with a sealed box and a much smaller inlet hole for the radiator.

Here is a link that describes what I'm talking about from a circle track magazine: http://www.circletra...ch_definitions/

The magazine article has some flaws, but the article estimates a 180 lb downforce gain from this type of box. It also talks about using a wide airdam to suck air out of the fenderwells.

 

You: Jon, No. Not according to Bob Smith. His comments were that you're going to get air packed in under the hood... There's no getting around it. Sealing off the nose of the car in general, like Roddy Sugg's car does, is an effective way to deal with the area at the mouth of the car. Look at the test data for #28, along with the other data for closing off the grill in other tests...

Also, remember, air is exiting the radiator/fan assembly at 15mph. You're travelling a lot faster than that (we hope) and what does that create? An area for air to pack up and create lift. Forego the whole "Aerodynamic downforce" theory of yours for a moment and think about just closing off that gaping hole in the front of the Zcar, known affectionately as the "grill". Do that, provide minimal feeding for air, and then funnel that air to your radiator however you wish, via ducts, tuning, sheetmetal/plastic radiator box, or whatever. Just remember that the air isn't travelling any faster than that, which means the larger that opening, the more air is getting caught there... and remember the first lesson we passed on from our friend Bob Smith. What happens at the very front of the car will impact everything else along the way... Total package, JM. Total Package!

 

Me: I think I'll have to disagree with Bob on that point then. I don't think you'd see so many race cars from so many different classes doing the same thing if there were no point. The opening to the box I'm suggesting could be whatever size you want to get a very small frontal opening. 

This is very similar to the point you guys proved about sealing the air dam to the core support. That prevents air from spilling out UNDER the radiator. The box prevents air from spilling out OVER the radiator and through the holes in the core support. And if you have a LOT less air in the engine compartment you might just make a low(er) pressure area under the hood, which translates to more downforce.

 

You: I won't debate "IF" a box would have worked, since it wasn't tried. But Bob Smith has tested hundreds of cars, and his insite was amazing. All these boxes on these cars could very well be tested, or could very well be something people "Think" is a good idea. Until we test them, I'm listening to the man that does this stuff for a living. he wasn't wrong pretty much every recommendation he made... choice is yours to trust a pro. I am.

Edited by JMortensen

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Right... MY radiator doesn't HAVE the core support that MOST Zcars have.  THAT is the point in all of this.  My car is vastly different from a stock chassis and that will alter everything in my tests.  Bob Smith told me exactly what you posted.  He also told me that i would require a box based on all the sheetmetal I was MISSING from my chassis.  He was very specific in his point that you WILL pack in tons of air under the hood and at a point, it fills to capacity and you won't be able to extract it.  It's the same exact effect as having the windows rolled down inside the car.

 

Goodluck with the impending stork visit.

Edited by Mikelly

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Guess your fish aren't that big since you posted all that back and forth, which clearly took lots of time... Here's a tip.  We all know you have to be the smartest guy in the room all day, every day.  Every thread you're in... we got it.

 

Go have your baby.  I think your water just broke.  :icon56:

 

I've got bigger fish to fry today guys, should have a new baby here in a couple hours. Suffice it to say that I'm in no position to demand anything of you, and that you're in position to ignore me if you so choose. I only persist because I think you're wrong, just like I thought the wind tunnel operator was wrong that splitters and rad ducts don't work on Z cars. I will donate if given the opportunity, and I will read through the numbers after the fact like a kid on Christmas morning.

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Guess your fish aren't that big since you posted all that back and forth, which clearly took lots of time... Here's a tip.  We all know you have to be the smartest guy in the room all day, every day.  Every thread you're in... we got it.

 

Go have your baby.  I think your water just broke.  :icon56:

I'M HERE TO TELL YA, THAT'S DAMN FUNNY RIGHT THERE..............

 

 I don't want to be all long winded like Chris pointed out so I'll be brief.............

 

Chris Duncan: You don't have the slightest idea of who you are talking to or what you are talking about. Your quote ( I want a Z with a flush bottom and a functioning diffuser. I'm never going to race but I just like the idea of having it. Heck I might want to go fast and it would be nice to have solid functioning aerodynamics.) I'm glad that "Heck" you might want to go fast one day. You sound like a teenager who has gotten his first car and wants to make it look cool. I don't have any flat bottom on my car and its probably one of the fastest 240Z race cars on the planet, so what would I know about going fast or winning races or NASA and SCCA Championships. For the record I've won 6 in a Z car. So like I said, what would I know??? The reason you don't understand my comments is you don't understand the questions you are asking. 

 

Jon:  I would love for my car to have a functional underwing and diffuser. I do not have the money nor the time to pursue that fabrication right now. Do I think it would work, yes. Do I think it would be worth the time and money to design properly, fabricate and install, NO. Do I feel there are other items I can address on my car presently that could give me more bang for my buck, without question, YES. It is just not a priority for me right now. 

 

Items that will reap larger returns: 

1. larger calipers (hence bigger pads / more surface area) possibly adding ABS

2. better and bigger rotors

3. stronger / larger wheel hubs

4. adjustable coil overs

5. tube frame chassis

6. more and more weight reduction

7. better rear end (9inch ford or curry)

 

These are the items that I feel are of more importance to me.

 

Lastly...........I think it is interesting that you know I have all this practical knowledge and hands on experience and I find out tonight after reading Mike Kelly's post that the gentleman who runs the wind tunnel, the guy that certainly knows more than any of us, said the same thing that I did about the underside. I don't mind being questioned or challenged but knowing what I said and what a guy who runs the wind tunnel said about the under-tray are identical yet you still push your agenda. 

 

Lets please return to the topic of this thread and organize and mobilize the crew that will make this event happen. 

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Chris Duncan: You don't have the slightest idea of who you are talking to or what you are talking about. Your quote ( I want a Z with a flush bottom and a functioning diffuser. I'm never going to race but I just like the idea of having it. Heck I might want to go fast and it would be nice to have solid functioning aerodynamics.) I'm glad that "Heck" you might want to go fast one day. You sound like a teenager who has gotten his first car and wants to make it look cool. I don't have any flat bottom on my car and its probably one of the fastest 240Z race cars on the planet, so what would I know about going fast or winning races or NASA and SCCA Championships. For the record I've won 6 in a Z car. So like I said, what would I know??? The reason you don't understand my comments is you don't understand the questions you are asking. 

 

:icon10:  I didn't mean for this to be a hostile exchange.  :icon10:  And it's pretty easy to see who you are, after all you made a video of a race day. A lot easier for me to see who you are than you to see who I am.

 

You described what a diffuser does, I already know that. You've asserted that the ones you've seen (at the track) don't work.

 

My questions, that you haven't answered, are, why do they not work, and what would it take to make them work?

 

I just love it though, and it really feeds my drive to succeed at something, when someone says something won't work or I don't know what I'm talking about. So keep it up, it has positive effects. :icon10:

 

I've been building cars from scratch for 25 years. I was wrenching on Z's before you had a drivers license. I don't know why these aftermarket or scratch pans and diffusers don't work and I was asking someone I thought might know. But even race car drivers don't know everything I guess. That's disappointing, I thought they were omnipotent. :icon10:

 

That's okay though, I'll figure it out one way or another.

 

I invested in Solidworks (with CFD) a long time ago. Pretty sure I can dig up a s30 solids file. I'll spend some time with the Z aero and get back with you guys.

Edited by Chris Duncan

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:icon10:  I didn't mean for this to be a hostile exchange.  :icon10:  And it's pretty easy to see who you are, after all you made a video of a race day. A lot easier for me to see who you are than you to see who I am.

 

You described what a diffuser does, I already know that. You've asserted that the ones you've seen (at the track) don't work.

 

My questions, that you haven't answered, are, why do they not work, and what would it take to make them work?

 

I just love it though, and it really feeds my drive to succeed at something, when someone says something won't work or I don't know what I'm talking about. So keep it up, it has positive effects. :icon10:

 

I've been building cars from scratch for 25 years. I was wrenching on Z's before you had a drivers license. I don't know why these aftermarket or scratch pans and diffusers don't work and I was asking someone I thought might know. But even race car drivers don't know everything I guess. That's disappointing, I thought they were omnipotent. :icon10:

 

That's okay though, I'll figure it out one way or another.

 

I invested in Solidworks (with CFD) a long time ago. Pretty sure I can dig up a s30 solids file. I'll spend some time with the Z aero and get back with you guys.

Chris,

If you are proficient in solid works that means you are more than likely a mechanical engineer. If you have been wrenching on Z's before I had a license that would make you around 55 to 60 years old. Given that you have all this experience you don't need my omnipotent race car drivers input anyway. I guess its just the immature way you post, your verbiage skills, the fact you don't read very well or it could be the fact you don't really understand what I'm trying to say to you. I never said that the diffusers (AT THE TRACK) that I see don't work. I am discussing our cars. 240Z's. Thats why I'm posting on HYBRIDZ. I have never seen a 240Z with a properly designed and functional underwing and diffuser. EVER. I have seen and driven plenty of modern race cars (AT THE TRACK) with perfectly balanced undertrays and diffusers that work just fine. Question for you.....Do you think you can take a modern race car undertray with diffuser and remove it from that car and attach it to the underside of a Z and it function properly. With all your experience wrenching on Z's I would have guessed you said yes given your previous posts. This of course is incorrect. It doesn't work that way. You say I've "asserted" that the ones I've seen at the track don't work. That is not what I said and Mike Kelly tried to point that out to you as well but you still insist that is what I said. For the record...........I said, ( I see loads of people who attach panels to the underside of a car, I see people buying diffusers all the time and not actually realizing that they are not doing anything but adding weight and drag to the car). Thats copied and pasted from my post. I am referring to the idiots who try and make their cars look like a race car but have in actuality caused more weight and drag thus it actually works against them. The design of a diffuser actually begins with the splitter and nose of the car, but you probably already knew that. I remember now, you dont ever want to race but might want to go fast someday and you wanted a functional underbelly and diffuser for your Z to be able to fully take advantage of the aerodynamics. Given that I'm 50 years old and omnipotent I'd say you better hurry up and get busy goin' fast. 

Edited by cobramatt

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:icon10:  I didn't mean for this to be a hostile exchange.  :icon10:  And it's pretty easy to see who you are, after all you made a video of a race day. A lot easier for me to see who you are than you to see who I am.

 

You described what a diffuser does, I already know that. You've asserted that the ones you've seen (at the track) don't work.

 

My questions, that you haven't answered, are, why do they not work, and what would it take to make them work?

 

I just love it though, and it really feeds my drive to succeed at something, when someone says something won't work or I don't know what I'm talking about. So keep it up, it has positive effects. :icon10:

 

I've been building cars from scratch for 25 years. I was wrenching on Z's before you had a drivers license. I don't know why these aftermarket or scratch pans and diffusers don't work and I was asking someone I thought might know. But even race car drivers don't know everything I guess. That's disappointing, I thought they were omnipotent. :icon10:

 

That's okay though, I'll figure it out one way or another.

 

I invested in Solidworks (with CFD) a long time ago. Pretty sure I can dig up a s30 solids file. I'll spend some time with the Z aero and get back with you guys.

Edited by cobramatt

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I'm here to gain knowledge, that is all.

 

I learned a few posts ago that you can't just "bolt on" an undertray and diffuser and expect it to work. I had suspected that already.

 

I was asking why, and what needs to be done to make it work, that's all.  I meant no disrespect but I think you took it that way.

 

I still don't have an answer...

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Here is a novel idea, if you don't like the agenda of those who are spending their time and money to conduct a test, and willing to share the data, then DO something constructive to contribute to the Zcar community yourselves. Otherwise, when you get pushback, think about WHY you are getting it. Chris I don't know or give a good goddamn about how old you are. I am 46 years old and have never claimed to be an engineer.  I have repeatedly stated that I listen to "true" experts, of which one person in this thread qualifies for based on real world first hand experience.  The points being made are when its your money tilting windmills is fine. Dont crtisize us because we choose not to ignore smarter peoeple than those in this thread.

There is an excellent laypersons explanation of what doesnt work with rear difusers in Junes GRM. An "expert" wrote that article, but as this thread has proven, his advice will likely be ignored too. Good luck with your software tests and finding a solidworks 240z model. Burton Brown has been looking for one for a while.

 

 

Now, since we keep getting asked "But why" (and I'm having flashbacks to my kids at 11-13), Maybe it has to do with the simple facts that the 40 year old Datsun Chassis is, well OLD, and designed 40 years ago.  Look at the fender openings and where the suspension uprights sit.  Where is the fuel tank located?  Notice how FAR BACK it sits behind the rear axle?  Look at how uneven the floor pans are.  What cars have you owned that have excellent aerodynamics?  I've got first hand experience with the most recent Corvette platforms, and both employed cab forward designs parking the wheels into the corners and minimalizing overhang.  Both employ saddletanks that rest in front of the rear wheels.  Both utilize complex shapes to help aid not only suspension and subftrame design but the designs of the fenderwells/liners to assist in clean aero, ALL before considing the tunnel for the driveline or the floor pans, which are, you guessed it, FLAT. 

 

 

Now lets move on to the Porsche.  One of the most sopisticated platforms made.  I've torn appart TWO of the most current 911s of the last decade, the Twin Turbo and the GT3.  Having owned both, I was intimate with their design.  Having converted the Twin Turbo to FULL FACTORY FUNCTIONING GT2 AERO, I can tell you with a great deal of confidence that they too exercised much of the same elements used in the C5/6 Corvette in designing the chassis for the task, only taking greater steps to incorporate those designs.  Aero channels starting just behind the nose and incorporated in the front closeout panel, air guides and diverters, vents and scoops built into the fender liners and other undercar panels... Google Mikelly and 996TT and you'll find the work done, and much like my Zcar pics, PLENTY of documentation. 

 

http://www.renntrack.com/forums/showthread.php?2227-FUNCTIONAL-GT2-Bumper-Conversion-DIY-Facts-Fiction-Broken-ankles-oh-my!&highlight=Mikelly

 

THOSE MANUFACTURERS DESIGNED THE CARS TO FUNCTION with ACTIVE AERO.  Datsun didn't in 1969.  That porsche Turbo was the car the windtunnel engineer pointed to as reference to what would be required to get  a Zcar to function like, well a POrsche.  His comments were something like this "Better off spending your money on one of those.  It'll save you the time of trying to recreate it."  I'm sure Mortensen can dig up the exact quote from somewhere, as he seems to need to prove I am foulable.

 

You guys want to create something that was unintended, and you can't just accept that "MAYBE" something won't work on the vaulted S30 chassis.  I love the Z.  It's why I still have it and all those other cars are long gone.  But I am a realist.  I know its limitations are somewhere below the basic platform of any host of other platforms.

 

 

Now, onto your jab at Matt Isbell for his video.  That's a pretty cheap shot and quite honestly, if he won't comment on it, I will.  I was SPONSORED by vendors for doing DEs in my Porsche.  Given parts to use, parts at huge discounts, or parts to evaluate and send back.  For DEs.  Matt is racing in NASA and winning nearly everything he enters, wheel to wheel.  You ever stop and think that marketing his talents might land him a seat in a pro ride?  Of course not, because it is to easy to look too shallow and assume this is a guy who is bragging and "look at me"... If you aren't a businessman or don't have an understanding of marketing in motorsports, you'll never understand how it is that I got porsche parts sponsors to give me high dollar porsche parts for free or at/below cost, or why a guy like Matt Isbell made a movie about his "day in the life" of a club racer.  And since you don't understand any of that, I guess it comes as zero surprise why the hell the issues around aero and flatbottoms on Datsuns is a HIGHLY unlikely successful venture.

 

 

I'm done justifying my efforts in getting some of the most developed Zcars in the country into the tunnel.  Those who want to participate can contact me offline.  Those who want to argue and be the smartest guys in the room can have this thread.  And as usual, run it into the ground.

 

EDIT:  NOW I'm DONE, and I've used the F'N ignore feature on this board for the first time.  No more Smartest guy in the room posts!!!

Edited by Mikelly

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Yesterday was a false alarm, for the record. Just a few more questions before you go Mike. I read that GRM article too. What materials did he suggest making a diffuser from? Did he say anything about needing CFD or tunnels or any other extravagant methodology to make one? How did he compare the Vette diffuser to the Civic diffuser that looked like it was built in a garage? Most importantly, is the author right because he is an expert, or is the guy at the windtunnel right because he is an expert? 

Edited by JMortensen

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Hey Matt that's a sweet vette, testarossa, caddy, maxima you've got there.  But on a serious note, I saw an Audi that was fast, really really fast... it had an underbelly, rear diffuser, AND a diesel engine.  Does that mean that if I put a diesel engine in my 240z that it will be faster?  Just like the Audi? 

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Seriously though thank you for all the input.

Rodger,

 

Thats my new daily driver and I'm glad you like it. I did that with plywood, cigarette smoke and a floor fan in my garage / wind tunnel. I am pretty sure it works because it looks really cool and I get a lot of looks. It seems I'm getting terrible gas mileage now for some odd reason but "heck" was thinking maybe I wanted to go fast one day and I just wanted to know I had functional aerodynamics on my car. Its a flat bottom as well.

 

About the Audi........If it said R18 on the side then you are correct. It is very very fast, very very quiet, very very expensive and very very exclusive unless your name is Alan McNish. This guy by the name of Dr Wolfgang Ullrich has made a living by winning LeMans every year and all he does is hang plywood under a car and see if it works. It can be hung relatively anywhere under the body and I think he is moulding his diffusers out of cardboard. Amazing stuff............I wonder if we could do that to one of our cars? If you ever do put a diesel Audi engine in your car, the undertray and diffuser come with the kit, you just bolt it on.

 

You are welcome for the input and I will continue to try and forward our cause and push the boundaries of what we thought was possible. How are my old wheels you bought from me working out? Do you ever run them? 

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The wheels are garage jewelry until I get the chassis done. The injectors are off getting cleaned and flowed. And the damper will go on when I swap the new cam in. Hopefully all done by end of summer. Just trying not to set her on fire for the time being. Your ride has come along nicely btw. Let me know if you decide to do the pinstripe as I have black vinyl and the last ever "stripe cutter". Sorry for the off topic guys...

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The wheels are garage jewelry until I get the chassis done. The injectors are off getting cleaned and flowed. And the damper will go on when I swap the new cam in. Hopefully all done by end of summer. Just trying not to set her on fire for the time being. Your ride has come along nicely btw. Let me know if you decide to do the pinstripe as I have black vinyl and the last ever "stripe cutter". Sorry for the off topic guys...

I forgot about all the items I've sold you. If you want to come to Road Atlanta this weekend and watch the car in action, there will be lots of people and lots of cars, I think our race has 50 cars. It will be a very big show and would love to have you out. Don't worry about being off topic on this thread as I have forgotten what the topic is anymore, so no worries. 

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