Rear spoilers, opinions and comments welcome

[Dat73z]

Lol no doubt, I was just curious if anyone had modeled or tested it. It sounds like no. I was a licensed and practicing fluid/thermal dynamics engineer for a decade so I understand the core concepts and have used all the tools. Nowadays I just work on my Z and other cars for fun but not at that level of getting into these details again...yet 😅

 

Yes some of these pics are likely from Alan, they came up in Google as I've been looking at the undertray on and off for a few years. I'll gladly remove them if he asks but I'd be curious his take as well. Hopefully I didn't stir up the pot there, at the end of the day these are just hobby cars for most of us and we're all enthusiasts

[HS30-H]

13 hours ago, JMortensen said:

Some of the stuff they did back in the day was pretty shady. Look at their homologated roll bar. Terrible. And now we'll get Alan Thomas in here being an ass because I criticized the factory roll bar. BTW, you better hope those aren't his pics. He's super generous about it when people use his pics to spread the general knowledge online.  

 

Ha ha. My red telephone just lit up. "...pretty shady".

 

I don't mind people using 'my' photos, scans and data as long as they understand what they are talking about. Your recent appraisal of the factory 'overfenders' on the Fairlady 240ZG was a case in point; You didn't seem to know *why* they existed, or what they were really *for*.

 

The factory 4-point bolt-in 'safety bar' is another example. It was simple clubman-level mandated protection, that's all. Nobody was pretending it was a spaceframe. In fact Nissan had intended to use a 6-point version with door bars for their own rally cars, but the team drivers (being gung-ho types) vetoed it because they felt it was "too intrusive". My personal opinion is that the factory kit is rather impressive in some ways, particularly the fact that the side mounting points were in EVERY bodyshell that was rolling off the production line. I'm not sure if your dismissal of it (I remember you calling at a "joke") is because you mistakenly believe it to have been an attempt to add structural rigidity for dynamic performance gain? It wasn't.  

 

What really grates is the people criticising what what Nissan did in period, first of all without truly understanding  what was going on, but also with the great luxury of hindsight. I'm interested in much of the stuff that went on in period from a historical perspective, and when I walk around a museum or a historic race paddock looking at 50+ year old race cars I don't tend to ridicule or deride the designers and engineers who made them, or recommend incongruous modern aero tweaks and carbon composite bolt-ons.

 

The HybridZ forum mostly revolves around the S30-series Z, which was designed and built as a road car for several different markets. The engineers involved had to be pragmatic and I don't think anyone has the right to critique their product (with 50 years of built-in hindsight) without taking into account the restrictions forced on them. As some of the photos above show, Nissan *did* conduct aero-related testing and parts development before the Z was in full production but that department was not going to be allowed to add anything to a 3.5k USD sports coupe in which the engineers were too frit to use a Servo synchroed transmission because the average buyer might think it was already broken. Built down to a price, with only one spec, right? Most of the time you didn't even get to order a particular colour. 

 

The topic title asks about rear spoilers, and mentions the "...'real/original' BRE spoiler...". The original BRE spoiler was actually the factory rear spoiler developed and homologated for the 432-R model in 1969, way before BRE even got hold of a Z. It was designed to work in conjunction with other aero-related components, but still had to exist as a viable roadgoing component. I don't think the factory engineers were lacking in expertise (they developed these parts in conjunction with Tokyo University and Japan's national aerospace department staff) and they were not stupid; They were simply forced to be pragmatic and practical.

 

Here, have a photo for fun. Factory race car, mid 1970. PZR (not 'ZG') overfenders. 10j & 8j wheels. Factory 'safety bar' (especially for you...LOL), reduced-maw front panel and ducted radiator with separate induction inlet. Full engine and transmission undertray. Brake cooling ducts. Quick jack hard points. Essential kit: Duct tape and an adjustable wrench. "Pretty shady", right...?

 

 

                   

[JMortensen]

6 hours ago, HS30-H said:

The HybridZ forum mostly revolves around the S30-series Z, which was designed and built as a road car for several different markets. The engineers involved had to be pragmatic and I don't think anyone has the right to critique their product (with 50 years of built-in hindsight) without taking into account the restrictions forced on them. As some of the photos above show, Nissan *did* conduct aero-related testing and parts development before the Z was in full production but that department was not going to be allowed to add anything to a 3.5k USD sports coupe in which the engineers were too frit to use a Servo synchroed transmission because the average buyer might think it was already broken. Built down to a price, with only one spec, right? Most of the time you didn't even get to order a particular colour. 

I think we finally got to the heart of it, Alan. Only took 20 years. The HybridZ forum is dedicated to putting modern engines and aero on the S30. We have every right to criticize what was done 50 years ago and there is no mandate for anyone to consider why it was done that way originally. The purpose of the site is to modernize the cars, using all of the knowledge and developments that have taken place since then, not to consider the limitations of engineers back then or restrict ourselves to them, let alone canonize those badly designed roll bars or flares or undertrays on race cars. Don't force your hagiographic pedantry on me, and for my part I won't bolt a carbon fiber swan neck wing onto your 432 when you aren't looking.  

[HS30-H]

1 hour ago, JMortensen said:

I think we finally got to the heart of it, Alan. Only took 20 years. The HybridZ forum is dedicated to putting modern engines and aero on the S30.

 

The OP is asking about putting a 'BRE' rear spoiler on his 280Z. And ".....This will be a street car with a few passes at the dragstrip per year." I don't think we are at the "modern aero" stage quite yet...

 

1 hour ago, JMortensen said:

We have every right to criticize what was done 50 years ago and there is no mandate for anyone to consider why it was done that way originally.

 

I was talking about critique. You are talking - automatically, it seems - about criticism. Quite different.

 

I have no problem with pointing at negative aspects, but - as I was trying to get across - it would be wise not to judge decisions taken 50+ years ago without taking into account the full circumstances surrounding them (as you did with the ZG overfenders homologation recently). I don't know why you find that so problematic?

 

1 hour ago, JMortensen said:

Don't force your hagiographic pedantry on me, and for my part I won't bolt a carbon fiber swan neck wing onto your 432 when you aren't looking.    

 

Hey, hagiographic pedantry is a dying art. Somebody needs to keep it going.

 

And that would be just great, thank you. But only if you could try to rein in some of your more Phyllis Stein-like tendencies when talking about matters that are - when all is said and done - historic.

   

[HS30-H]

Oh, and - come on - don't be lazy. You didn't criticise the car in the pretty picture I posted. There must be a whole bunch of cardinal rules the damn fools didn't even know they were breaking. Killjoy. 

[JMortensen]

Just now, HS30-H said:

The OP is asking about putting a 'BRE' rear spoiler on his 280Z. And ".....This will be a street car with a few passes at the dragstrip per year." I don't think we are at the "modern aero" stage quite yet... 

He's asking a question about a spoiler. We are having a conversation about which spoiler works best and why. You are derailing it with bullshit about why we shouldn't criticize a given part because it was produced 50 years ago.

Just now, HS30-H said:

I was talking about critique. You are talking - automatically, it seems - about criticism. Quite different.

Must be using that British English, or your language pedantry isn't as strong as your Datsun pedantry. From Merriam-Webster:

critique: an act of criticizing

criticism 1a: the act of criticizing usually unfavorably

Just now, HS30-H said:

Hey, hagiographic pedantry is a dying art. Somebody needs to keep it going.

 

And that would be just great, thank you. But only if you could try to rein in some of your more Phyllis Stein-like tendencies when talking about matters that are - when all is said and done - historic.   

I don't need to rein in anything. You should rein in your tendency to interject with offended posts that have nothing to do with critiques of these shoddy parts. 

[HS30-H]

1 hour ago, JMortensen said:

He's asking a question about a spoiler. We are having a conversation about which spoiler works best and why. You are derailing it with bullshit about why we shouldn't criticize a given part because it was produced 50 years ago.

 

No, I'm here because you name-checked me after somebody used my scans & photos in the topic. 

 

"Bullshit". Noted. No surprise, but noted. "We shouldn't... " also noted. I think the word you are looking for is "I".

 

1 hour ago, JMortensen said:

Must be using that British English, or your language pedantry isn't as strong as your Datsun pedantry. From Merriam-Webster:

 

"That British English" LOL. How quaint. How colonial.

 

I'm using English. My native tongue. You cite Merriam-Webster, an American dictionary. This is... typical. Critique isn't necessarily negative in the English language.

 

And please, Nissan. I'm usually talking about the company which made this stuff. Not a badge that was affixed to their product.

 

1 hour ago, JMortensen said:

I don't need to rein in anything.

 

No, really. You do. You're far too personal with all this. Give your head a wobble, have a glass of water or brush your teeth. To wit:

 

1 hour ago, JMortensen said:

...these shoddy parts. 

 

Parts like the 'BRE' spoiler?

 

You don't know enough about them to go anywhere near that far, but you go there because you don't like the messenger. You'll hate them because you think I love them, right? Freud had a theory about all that.

 

Really, you need to step back from the keyboard and cool your heels a little. You invoked my presence here by citing my name with a slight (go back, remind yourself). I had my tongue firmly pressed in my cheek initially, but you just can't help yourself can you? Sow the wind, reap the whirlwind...   

 

 

 

 

 

 

[JMortensen]

You're searching forums for your own name so that you can chime in with your thread jacking pedant posts? LOL I suppose I should have known. Like a hair trigger Beetlejuice. Please, can we spend less time talking about how you're misusing words and more time talking about spoilers and aero and how they work, and less about who made them or making excuses for them? 

 

[HS30-H]

12 hours ago, JMortensen said:

You're searching forums for your own name so that you can chime in with your thread jacking pedant posts?

 

No, of course not. You're so funny.

 

I have servants to do that kind of thing...

 

(for best effect, read my posts aloud in Stewie Griffin's voice)

[jhm]

On 4/14/2022 at 3:55 PM, JMortensen said:

Not sure if this link direct to the album will work. https://www.facebook.com/media/set/?set=a.1581733071873043&type=3

 

Yep, that link worked.  Thanks for the reference data!

 

@fusion, the discussion may have gotten a bit off track....but did you get the info you needed to make a decision for your 280?

[AydinZ71]

wait... do we still get to post about the semi-relevant conversations? Not related to air dams/spoilers, but the tangent of airflow at the front of the car.

If so... disclaimer: these are my thoughts and opinions. I don't have wind-tunnel or extensive track experience and I am experimenting.

 

SCCA EP: We are not allowed any new openings in the bodywork (no vents), including between the wheel-well and the engine bay. We can modify airflow once it has made its way past the bodywork, so no problem blocking off air from going over and under the rad. support. A few pics posted and eager to hear your opinions and have a discussion. 

 

1) I put a relief in the firewall to allow access between the OEM cowl vents and the engine bay. The cowl was completely rusted and needed replacement anyways, so seemed like a clever idea. Some say the air will actually flow from the cowl down into the engine bay, but the vents are several inches in front of the high-pressure point on the windshield so who knows. The idea was to relive the low-pressure on the underside of the hood with the means available so we'll see.  

 

2) rad area. I have not put the aluminum cladding in yet, but as several have mentioned I will be blocking air from diverting away from the rad support going over the top and bottom. What you can see is how I block the horizontal flow of air from going anywhere other than for a purpose. There is an engine air intake, two air intakes for the fresh-air ducts (I was told you need as-much fresh air as you can for a race car), and the rad of course. Two holes on the left are for grommets to allow the oil cooler lines to pass-through. Plenty of room and space for riv-nuts for fastening of AL cladding. 

 

Eventually I will be installing the 280Z FRP bumper to further block and re-direct air away from this massive front-end opening. 

Edited April 18, 2022 by AydinZ71

[fusion]

13 hours ago, jhm said:

 

Yep, that link worked.  Thanks for the reference data!

 

@fusion, the discussion may have gotten a bit off track....but did you get the info you needed to make a decision for your 280?

 

Yeah, I ended up ordering the newer version of the BRE spoiler.  Since I have the Type 1 air dam I feel that I shouldn't have to worry too much about the front end feeling light.  I also hope my hood vents keep the pressure underhood to a minimum.

[JMortensen]

21 hours ago, AydinZ71 said:

1) I put a relief in the firewall to allow access between the OEM cowl vents and the engine bay. The cowl was completely rusted and needed replacement anyways, so seemed like a clever idea. Some say the air will actually flow from the cowl down into the engine bay, but the vents are several inches in front of the high-pressure point on the windshield so who knows. The idea was to relive the low-pressure on the underside of the hood with the means available so we'll see.  

I think this is the wrong move, but it would be pretty easy to test if you put yarn tufts on the cowl vents. If they blow into the cowl, you're forcing air under the hood. You mention relieving the low pressure under the hood, but you want low pressure under the hood. You'll already have low pressure on top of the hood as the air flows past, and if you can get it, you want lowER pressure under the hood. The pressure differential will act on the surface of the hood, making downforce. If you equalize the pressure, you'll eliminate the downforce. The opposite is when you see a hood blowing up like a balloon, like the Janspeed car. You can imagine if that's .1 psi on the bottom surface of the hood, which is something like 3x5 feet as a rough estimate, that's 2160 square inches or 216 lbs pushing up on the bottom side of the hood. You can see what looks like here. Leading edge and sides of the hood are bowed up pretty severely. Looks like a thin FG hood, but makes the point pretty clearly: 

21 hours ago, AydinZ71 said:

2) rad area. I have not put the aluminum cladding in yet, but as several have mentioned I will be blocking air from diverting away from the rad support going over the top and bottom. What you can see is how I block the horizontal flow of air from going anywhere other than for a purpose. There is an engine air intake, two air intakes for the fresh-air ducts (I was told you need as-much fresh air as you can for a race car), and the rad of course. Two holes on the left are for grommets to allow the oil cooler lines to pass-through. Plenty of room and space for riv-nuts for fastening of AL cladding. 

 

Eventually I will be installing the 280Z FRP bumper to further block and re-direct air away from this massive front-end opening. 

Not sure I follow you here, but just to give an example here is a link to some pre-fab rad ducts: https://www.jegs.com/p/Five-Star-Race-Car-Bodies/Five-Star-Radiator-Ducts/2834016/10002/-1

Years ago I linked to an article from Circle Track magazine where they showed the difference between a ramped duct with a smaller inlet like in the link above vs a duct as big as the hole in the grill without a ramp, and there was a significant advantage to the smaller opening with the angled duct. I want to say it was worth 100 lbs downforce or something crazy like that. The article is gone now, unfortunately. A NASCAR isn't exactly the same as a Z because circle track cars have no fenderwells and they can exhaust a lot of air out of the sides, but I would still do the duct that way since it's better in theory and I don't think it will be significantly harder to make. YMMV.

[AydinZ71]

@JMortensen ahh! Yeah you are right, I misspoke. The air going overhead is creating the negative pressure on TOP, hence the ballooning hood. I thought this could relieve the high pressure under the hood, but like you said il have to stick some yarn on there and see how it performs. Might not work or be counter productive. We’ll see! 

 

the rad support area I made is just the steel mounting surfaces and structure, but I can duct the air in various ways with AL sheet. The goal was to stop air from diverting away from the rad. The pass-through’s that did not serve a purpose were removed, so now it’s ready to have AL on top, sides, and bottom during assembly. The ramped opening (I guess they are called diffusers?) for the rad and other coolers is something I saw in the 80’s Paul Newman turbo ZX car as well. Il have to look more carefully at what I’m allowed to do in the front. The bumper was used in EP as a tool to block more rad opening surface, so il have to look more carefully as how much (if any) of the OEM opening can be restricted by simply blocking more of it off. Absolutely agree the opening can be much smaller than OEM for a road racing car, and diverting air around to the sides of the car should reduce the drag coefficient. 
 

hey I’m all ears for any other ideas you have! 

[calZ]

One thing I see a lot in automotive aerodynamic discussions online is that people tend to group things into "high pressure" and "low pressure" areas, when in reality it's anything but binary. The cowl area is definitely near the upper end of the pressure range, but as long as the engine bay is even higher, air will still flow. There's been plenty of people who run a popped hood and get better cooling, which shows the potential, but the cowl vents are much closer to the windshield in a relative sense. Are you allowed to add metal the outer body of the car? A raised flap/ramp in front of the cowl openings would almost assuredly make the pressure gradient favorable enough to get flow how you want it. 

[calZ]

This is a lot further forward than the cowl would be, but see my old MR2 racecar as an example. 

[JMortensen]

I doubt that a flap right in front of the cowl would turn the positive pressure area into a negative one, maybe as you said, change the pressure enough to get the air to flow. You could think if the windshield as being a flap that is 20x as tall and I think the windshield would overpower the flap. It is something that could be easily tested though; just tape a piece of angle to the hood in front of the cowl vents. Probably easier than making a block off plate to close up the firewall.

Edited April 20, 2022 by JMortensen

[AydinZ71]

Cool! Yeah, unfortunately I am unable to add anything to the body besides flares, and a front air dam. No new vents or openings into the body. No scoops etc. 

 

what you had on your MR2 makes sense! Makes double sense with front-engine cars so you can get rid of the hot radiator exhaust air vs. warming all your under hood components. Especially if your intake/carbs are pulling from the engine bay 

 

my initial reason for opening up the space between the engine bay and the cowl was to expel heat under the hood. In that context, it didn’t matter if the air went in or out of the cowl vent, as long as it’s moving. I would imagine similar would be true for alleviating the pressure differential between the top and bottom of the hood. 

[AydinZ71]

I will have to make a block-off plate for the engine-side of the firewall so I have it handy in case the stewards flag the experiment as a no-go. It’s not completely futile since it replaces much of the stiffening the OEM heater chimney/manifold used to provide. The firewall (in multiple spots) and windshield sill are conveniently tied to the roll bar. 
 

i will definitely be doing the string-test Jon mentioned just to see which direction the air is moving. 

[A to Z]

Wow, a lot of good comments and info....we obviously have well educated and experienced folks on here.

 

For me, I care about looks.  For my 240Z I went with BRE front and rear.  Since Pete Brock offers an new updated rear spoiler that is taller, maybe that is what you need.  But for me, I like the front "spook" spoiler and the original BRE rear spoiler.  Yes it has 6 contact points, which I think is a good thing......If you ever want to drive it at any kind of speed, you will need the extra bracing to keep it on!

 

I will be adding some flexible "ZG STYLE" bolt on flares I found on eBay that will give me some coverage on my wheels since I do have "poke out"...1 inch front 2 inch rear.

 

 

Edited July 3, 2022 by A to Z