G8 GXP Rear diffuser on an S30

[RB30X]

Has anyone here fitted a G8 or GXP rear diffuser on an S30??

 

I think it would look ok, especially if you have twin pipes out the back.

 

 

They are pretty cheap to buy, I wonder how easy to fit?

 

Someone with some photoshop skills should merge one onto a rear end to see what it woud look like.

[emeraldlion]

Having looked closely at the rear of LOTS of g8's I would say not easy to fit at all. I think the overall curvature horizontal would be off.

[RTz]

That's not a diffuser. That's a purely cosmetic trim piece, attributing less than 10 cents worth of aero performance. It would probably be easier to fab a potentially functional diffuser to fit a Z.

[zeeboost]

Although I've been planning on building one out of sheetmetal or abs plastic, my roommate has an evo 8 with the JDM rear bumper/diffuser...it's got me thinking. Here's a pic of one similar to it:

 

 

 

 

Actually, I think it's this one:

 

[RB30X]

That's not a diffuser. That's a purely cosmetic trim piece, attributing less than 10 cents worth of aero performance. It would probably be easier to fab a potentially functional diffuser to fit a Z.

 

That's correct, but its a start that looks good, and you could modify underneath to actually become practicle. As far as fabbing up a functional diffuser to fit a Z, if it was that easy, why don't we see them everywhere already. I mean good ones.

[JMortensen]

That's correct, but its a start that looks good, and you could modify underneath to actually become practicle. As far as fabbing up a functional diffuser to fit a Z, if it was that easy, why don't we see them everywhere already. I mean good ones.

Probably because the sides need to be about 2" off the ground for them to really work. There was a good article in Race Car Engineering a few years back...

[Challenger]

I'll hopefully make a functional one for my car when it's on the road. I just plan on having each blade swivel so it can fold upward if I go over a bump or up a driveway. That way it can be close as John describes.

 

I don't see the g8 looking good on a z. Just make a fake one that yourself if you don't care about function.

[GOTHALOSISM]

In a way its a good idea to hide the fuel tank for us that run shaved rears.

[Challenger]

Yeah, the fuel tank is kind of ugly. Anything to make the back end look less like a 4X4. haha

[260DET]

Have a search for a S30 named Red Bird, he has a really good custom rear diffuser. Thought I had a pic of it but can't find.

[ZROSSA]

Have look in my photo album on this site. I havent done much more with it but its a similar concept to what you are looking at. I have made it so its flush with the fuel tank. I realy think it only lets air out a bit better, maybe integrates it better into the air stream behind the car as well but like john said, it wont produce downforce.

 

I need to get back into the zed. So close but yet so far!!!!!

 

 

Douglas

[bjhines]

I might make a few observations. Mayolives could not use that piece. It was highly unstable.

 

Nearly all modern performance cars have a full length, perfectly smooth underpan. They also have many other aero components to go with them.

fully housed wheels,

Wheel well liners,

sealed front clips

sealed engine compartments(front engines).

 

The thing to keep in mind is that the term-"diffuser" does not work with these designs and is 80% styling even from BMW and Merc. It neatly ties the underpan into the rear bumper and that is all.

 

=====================================================

If you get into the SUPERCAR category then you begin to see real diffusers that have a real effect.

 

The entire underside of the car and the placement of the suspension mounting points is affected to use a real race car diffuser.

I have pics of a Ferrari that I had my greasy mits on a while back.

 

====================================================

As you can see... That will not work on a "normal" car. So forget performance and realize that what you are doing is for styling. If you really wanted to improve aero then buy a later model car, or follow the Aero threads for hundreds of useful mods. The S30 is always going to be a brick. The trick is making slight improvements without making it unstable at speed.

[ZR8ED]

I don't know if I still have any pics up of my "rear diffuser" posted on this site. I can't say that it worked at all, but I can say that it didn't make the car unstable either. It was mostly a styling "look". AND it took a tremendous amount of planning and effort to construct, and then to actually install it so it will STAY on. Mine is now removed since I redid the rear fascia, but I have plans to put something back on again in the future. I would only do it as an "interesting project". I already have extensive aero mods already to the front of the car. At least as much I am prepared to live with on a "street car"

 

Retro fitting a diffuser on our cars from another model, is mostly useless, and with the amount of effort to get one to fit, might as well not have to deal with all the compromises (to get it to fit) and just custom make one that fits perfect.

 

Scott.

[JohnH]

A rear diffuser must work in conjunction with front end & mid section areo mods. Basically a flat plane of narrow road to vehicle under surface height must be created in front of the diffuser which will channel air from the front of the vehicle to the end of the diffuser. Its this venturi effect that cause a low pressure point that enables downforce.

 

for your reading & viewing pleasure.

 

http://www.racecar-engineering.com/articles/f1/316271/diffusers-explained.html

 

.46 minute on the youtube video

 

http://www.youtube.com/watch?v=7TwOBR5Yep8

[proxlamus©]

Its this venturi effect that cause a low pressure point that enables downforce.

 

 

 

Almost right.. the lower the car is to the ground, the velocity will increase.. which reduces pressure. High pressure creates lift.. in this situation.. lift is reduced.

[RB30X]

Ok. Maybe this has gone a little deep. I'd love a practical diffuser but how about just cosmetic. I've since found out it's about 150mm to wide any way so it would have tone shortened.

[260DET]

It should not be forgotten that the earliest diffusers were simple rear mounted angled pieces, nothing more. Sure a diffuser will work better if its part of a complete undercar aero package but thats not necessary to get a worthwhile benefit. I've looked at putting one beginning at the back of and level with the bottom of the 280ZX's fuel tank and can see no reason why it should not work.

[zsteelman]

Depending on if you put a piece to funnel air away from the top of the tank you might creat an air pocket that will cause turbulence.

 

Dont the majority of cars that use these for actual aeeodynamics have full plating across the entire belly of the car?

[JMortensen]

It should not be forgotten that the earliest diffusers were simple rear mounted angled pieces, nothing more. Sure a diffuser will work better if its part of a complete undercar aero package but thats not necessary to get a worthwhile benefit. I've looked at putting one beginning at the back of and level with the bottom of the 280ZX's fuel tank and can see no reason why it should not work.

I think you're right. As an example of an extremely crude diffuser, the pre-COT NASCARs had a really high rear end, and my understanding was that the spoiler in conjunction with the high rear end pulled air out from under the car as a diffuser does. I remember reading when the COT came out that there was an engineer on every team whose sole duty was to determine optimal placement of the fuel tank for best aerodynamics, and how those guys would be out of a job. At lower speeds without a clean path for the air to flow through, I think a rough diffuser might have limited benefit compared to a properly designed one that has fences close to the ground, etc. I'd love to see that idea tested, maybe with Mayolives' car as suggested previously. I can say that in McBeaths book Competition Car Aerodynamics (which I know Richard has) both the splitter and the spoiler are shown to be net improvements on NASCARs with rough underbodies and no trays. What I'm beginning to take away from this is that the "best" solution would be a nicely fabricated undertray with splitter and diffuser, but if that isn't possible a splitter in front, crude diffuser in back with a spoiler to help it pump air, and maybe a wing on top of that is a relatively easy solution. Funny, I think that's basically what the blue Z in the video has (although it may have a full tray under it, can't see in the vid). Still wondering what would happen with my air dam at the end of a splitter chin idea...

Edited August 14, 2010 by JMortensen

[260DET]

It was a Jaguar racing team that I think 'discovered' rear diffusers. The backs of their cars were so low they had trouble getting them on and off the transporters so the rear ends were modified to form a slope up angle underneath for better clearance. This resulted in more rear grip on the track and improved lap times, love those sorts of incidential discoveries that result in advances in car performance