When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
2020 Corvette of the Year Finalist (track prepared)
C7 of Year Winner (track prepared) 2019
Originally Posted by Red86Cfour
I think it will add about ten pounds of downforce!
I've worked with a few race cars that actually have down force producing devices on them. One of the main reasons for using a diffuser is to help activate the rear wing. But in order for it to work ramp angles and distance to the road surface all need to be at optimum to work. This one isn't even close. I've never seen a diffuser that was worth anything have flat horizontal surfaces, they're all curved like the bottom side of a wing (on a car). And they won't do squat below at least 60 Mph. And they won't do squat without airflow either.
If you're going to test it you need some specialized equipment such as pressure taps, and at minimum ride height sensors at all four corners. Load cells would be better. All hooked up to a decent data acquisition unit.
There are many diffusrs in motorsport that have flat topped tunnels. Sure some are more effective than others.
though just to be clear im not arguing that the diffuser the Op linked is functional or not. I'm arguing that it would be marginally effective in a track setting and more than likely not noticeable at all to the Op.
what do you mean "activate the rear wing" a diffusers primary goal is to accelerate the air under the car. That shouldn't have any impact on any wing.
Last edited by lobsterroboto; 01-21-2019 at 03:35 PM.
There are many diffusrs in motorsport that have flat topped tunnels. Sure some are more effective than others.
though just to be clear im not arguing that the diffuser the Op linked is functional or not. I'm arguing that it would be marginally effective in a track setting and more than likely not noticeable at all to the Op.
what do you mean "activate the rear wing" a diffusers primary goal is to accelerate the air under the car. That shouldn't have any impact on any wing.
Because it's relative. If the air above and below are "sped up" to the same speed, there is no lift/down force. And it doesn't accelerate the air under the car as much as the air exiting the car.
Anyway, diffuser doesn't do much without a really flat underbody.
2020 Corvette of the Year Finalist (track prepared)
C7 of Year Winner (track prepared) 2019
Originally Posted by village idiot
Because it's relative. If the air above and below are "sped up" to the same speed, there is no lift/down force. And it doesn't accelerate the air under the car as much as the air exiting the car.
Anyway, diffuser doesn't do much without a really flat underbody.
That's not true.
Diffusers are just more effective with a flat bottom. There is data to support this. RHR even has their data available publicly comparing their diffuser on a "dirty bottom" car to a flat bottom car. The flatter you make the bottom the better the results.
Just because something isn't as effective doesn't make it not effective.
As far as what you're talking about since you quoted me I have no idea what you're talking about. Ideally there is zero air above most of the diffuser. Just below it, your statement of getting rid of the air is literally speeding up the airflow under the car just in different words. Which creates a low pressure area underneath the car thereby creating "downforce" for the chassis not just that one little spot the diffuser is at.
I love the rear window slats!!! I had similar on my Datsun 260Z when I was a kid, loved 'em. I'd love to see more pics of this car from different angles to really see the visual effect of the rear window slats.
Wow
I'm quite impressed by the number of forum members who have access to wind tunnels
and have tested this diffuser to definitively state that it provides no functional improvement..
Just because you don't understand it, doesn't mean we don't. That's why I said "virtually zero". It may add 1 lb or 2 of down force at 100+ mph. But so does holding your **** in before you go on track.
Last edited by BrunoTheMellow; 01-21-2019 at 10:35 PM.
I love the rear window slats!!! I had similar on my Datsun 260Z when I was a kid, loved 'em. I'd love to see more pics of this car from different angles to really see the visual effect of the rear window slats.
Here ya go:
Last edited by agapsdiver; 01-21-2019 at 11:55 PM.
Diffusers are just more effective with a flat bottom. There is data to support this. RHR even has their data available publicly comparing their diffuser on a "dirty bottom" car to a flat bottom car. The flatter you make the bottom the better the results.
Just because something isn't as effective doesn't make it not effective.
As far as what you're talking about since you quoted me I have no idea what you're talking about. Ideally there is zero air above most of the diffuser. Just below it, your statement of getting rid of the air is literally speeding up the airflow under the car just in different words. Which creates a low pressure area underneath the car thereby creating "downforce" for the chassis not just that one little spot the diffuser is at.
I never said it doesn't do anything. I said it doesn't do much without a flat bottom. In a true race car, half or more of the downforce comes from flat underbody + diffuser. That's just not happening with an "OEM" underbody with exhaust and lines and worst of all- the wake off the tires. I think F1 has like 60 or 70% of downforce coming from flat underbody. It's also a more efficient way of creating downforce relative to wings and such. None of it is going to happen at anything near street speeds at anything resembling a street ride height either so this whole conversation is moot (though interesting).
As far as wing- thing of the whole car as an airfoil. If the air above the car and below the car are the same speed, you're not going to have (much) lift (positive or negative). There is an interaction with wing and diffuser, if nothing else, because they're right on top of each other. I wish I remembered more details- it's been nearly 2 decades, but the two interact.
To say it "doesn't work" is a little bit of a misnomer imo.
It has an under tray from the rear axle to the rear of the car. This will help with the low pressure air moving under the car.
With that said, I do have a revised "track version" of their diffuser that im more or less beta testing, the fences are longer and taller My car is fairly low and coupled with the taller fences I imagine it may be a little bit functional.
Nice track car!! Just an observation....Your decals on the rear fascia; TT2 and 281 are aligned at the top but not the same size fonts so they look crooked. That would drive me crazy. Hahahaha
2020 Corvette of the Year Finalist (track prepared)
C7 of Year Winner (track prepared) 2019
Originally Posted by WICKEDFRC
Nice track car!! Just an observation....Your decals on the rear fascia; TT2 and 281 are aligned at the top but not the same size fonts so they look crooked. That would drive me crazy. Hahahaha
Thanks, yep the car was a DE car for a while before i started in time trials and added the class decals. I never noticed it until you said something. My car has been washed like 3 times since 2015. v0v
decals are slightly off from each side of the car as well btw.
01-21-2019, 03:31 PM
