Jump to content
HybridZ

Windtunnel Testing the Datsun S-30 Z


Recommended Posts

I still think you guys are wrong about the air under the hood. If NASCAR can get neg pressure under the hood, then we can. NASCAR cars are very basic in terms of shape, previous to last month's release of the COT they didn't have splitters or anything else. No undertrays, no nothing. All they do is get the nose of the car ON THE GROUND, and use the shape of the car to extract air from under the hood.

 

I see no fundamental reason why we can't do the same thing.

Link to post
Share on other sites
  • Replies 79
  • Created
  • Last Reply

Top Posters In This Topic

I have no idea where the cooling airflow comes from when it's all plugged and panned. Even without a pan, with the radiator blocked, it doesn't seem to really affect it. The temperature we saw at Bonneville can probably be directly related to holding the car at 8000+ rpms for five miles straight....

 

I mean, I never took a static pressure reading in ALT configuration, but now you guys got me wondering if we indeed have some sort of 'negative' under there, and the radiator is basically 'ground breathing' for circulation. Our Bonneville car is pretty low, without anybody in it, I can't fit my wrist sideways under the T/C section of the frame at the firewall---I have to use a can picker-upper to stuff the plugs in the header collectors. Though now since we didn't see any loss by running the twin 3" exhausts, we can plug them at the rear of the car instead of trying to plug them from underneath.

Link to post
Share on other sites

I won't speculate further. What I know is what a guy who does it every day for a living recommended to the 9 of us in the control room. Without testing the setup, we can mentally spar until we're tired.

 

We can certainly add it to the list for next time, and do some myth busting.

 

Mike

 

I still think you guys are wrong about the air under the hood. If NASCAR can get neg pressure under the hood, then we can. NASCAR cars are very basic in terms of shape, previous to last month's release of the COT they didn't have splitters or anything else. No undertrays, no nothing. All they do is get the nose of the car ON THE GROUND, and use the shape of the car to extract air from under the hood.

 

I see no fundamental reason why we can't do the same thing.

Link to post
Share on other sites

So how about a reinforced home depot lip? Held in place by some spring steel...

On my car at full down on the suspension my home depot lip (hard plastic lawn edging, not the soft rubber stuff) is about 1" from the ground. I usually run about 2.5" higher than that though to get over normal street bumps and road transitions. I am going to be mounting my belly pan soon to help reinforce the air dam and block off the radiator-airdam gap.

Link to post
Share on other sites

One source of high pressure air is just in front of the windshield. You can see the yarn is some of the photos drops into the windshild wiper grill. I know there's one post about overheating at speed caused by a rear hood cowl. High pressure air in front of the windsheild slows flow through the radiator enough to raise engine temps significantly. The problem was solved by moving the vents closer to the stock outboard locations. Maybe this answers the low 15mph radiator exhaust flow.

 

With a couple of the test cars having hood latch problems and that there are small passages from the wiper area to under the hood, I think future tests could make sure the rear of the engine compartment is sealed as well as the front.

 

I know it's being debated whether or not negative engine compartment pressures can be acheived, but it looks to me that efforts to reduce pressure will not only help with down force, but with drag by increasing the pressure differential between the front and rear of the radiator, thus allowing for a smaller mouth opening.

Link to post
Share on other sites

I still think you guys are wrong about the air under the hood. If NASCAR can get neg pressure under the hood, then we can. NASCAR cars are very basic in terms of shape, previous to last month's release of the COT they didn't have splitters or anything else. No undertrays, no nothing. All they do is get the nose of the car ON THE GROUND, and use the shape of the car to extract air from under the hood.

 

 

Yeah I think the important thing to think about is if your cars a street car or a race car. Im sure it would help to have the airdam scraping the ground but then you cant go over any bumps etc. Just thought Id mention that.

 

Anyways like on the car of tomorrow the front air dam routes air out the sides in front of the tires. If you were to make a panel that extends out from under the air dam and then goes around the side of the car to the front of the tires where some kind of flare routes the air out sideways? Would that help. Ill work on some kind of picture its hard to explain.

Link to post
Share on other sites
Just a few questions/observations...

 

 

 

Isn't this backwards? If you look at #9-#10 (change to the whale tail), the rear lift numbers went from positive (lift) to negative (downforce), not negative to positive, as that says it would.

 

 

Also, looking at total front lift during #5: the difference between the hood popped test and the retest is 120lbs of lift! Correct me if I'm mistaken, but doesn't that mean that an easy way to reduce front lift for those of us with stock/near stock bodied s30's is to just pop the hood to the second latch when we near those speeds? Or did it miss the second latch and pop a few feet up or something?

 

This is what we were starting to conclude in the whaletail thread.

Link to post
Share on other sites

No.There is a high pressure region at the base of the windshield.The original purpose of the original "cowl induction"hoods was to tap into this high pressure to help feed the engine's induction system with cool positively pressurized air.Of course nothing is certain until tested.The windshield base/cowl area of the Z has very complex flows and pressures.You have high and low pressures adjacent to each other.Very small details in this type of zone can swing downforce and drag numbers from one and of the spectrum to the other.There really is not enough data to draw any conclusion yet.Let's go back to the tunnel!

Link to post
Share on other sites
  • 2 months later...
  • 2 months later...

okay...i was looking at the numbers on the jpeg image and i couldnt really make much of it (havent got into aerodynamics yet ;) ). is there any way to kind of sum up what works vs what doesn't? i.e.: headlight covers = less drag, etc??? if not its okay...maybe if i stare at it long enough it will "magic eye" into something useful lol

Link to post
Share on other sites
  • 2 weeks later...
  • 5 months later...
  • 5 months later...

Was wondering what happened to this thread? Sounds like intresting stuff, but is there suppose to be some pics?

 

Also as far as negitive underhood pressures go. Dont forget to duct in some good air for your motor or you could cause flow problems for the motor when it needs it most. I have seen motors get choked out with ducts in the wrong places.

 

 

EDIT""" Sorry I found it.

Link to post
Share on other sites

You might be interested in knowing that we found that "less air" is more when it comes to ducting to the radiator. According to the windtunnel engineer, NASCAR uses 2X4 inch openings for air flow to the radiator and close or open them with tape as needed...

 

Do a bunch of reading on this test. We found a lot of great info.

 

Mike

Link to post
Share on other sites
You might be interested in knowing that we found that "less air" is more when it comes to ducting to the radiator. According to the windtunnel engineer, NASCAR uses 2X4 inch openings for air flow to the radiator and close or open them with tape as needed...

 

Do a bunch of reading on this test. We found a lot of great info.

 

Mike

 

 

Was that directed toward me? I think i already put that same info in another thread about tilting the radiator. I think you missunderstoodwhat I was saying as i was talking about choking the flow to the motor not through the rad. I totaly agree with what you said above though.

Link to post
Share on other sites
  • 10 months later...

I just thought I would share my 1976 280z 2+2 Wind Tunnel Testing I completed recently, I figured it would be great food for thought for our resident aerodynamics specialist to comment on, as well as everyone to benefit from.

 

Best of all this testing was done for free overnight while I slept and yielded the optimum aerodynamic profile for a S30.

 

Here you go:

spict0001_thumb.jpg

spict0002_thumb.jpg

spict0003_thumb.jpg

spict0004_thumb.jpg

16068_thumb.attach

spict0006_thumb.jpg

spict0013_thumb.jpg

spict0014_thumb.jpg

spict0015_thumb.jpg

spict0007_thumb.jpg

Link to post
Share on other sites

×
×
  • Create New...