R34 Sedan Aero Improvements

[V28VX37]

Hi guys, I'm trying to figure out some potential aero improvements for the 4door and keen for some input.

The goal would be to have more downforce to improve high speed stability. The one time I've been at the track in the car it didn't exactly feel planted doing 199km/h up the back straight at Sandown.

Would a rear undertray/diffuser help with this? There's a massive cavity under the boot area in the R34 sedan - is there anything similar to the GT-R undertray available for it?

With the front of the car, this URAS bar looks very trick, however I wonder if it makes any actual difference?

I'm currently running Origin rear window and boot lip spoilers but they probably don't do much. Would a bigger drag style wing help with downforce?

Any other tips are welcome too!

[niZmO_Man]

Make you own undertrays.

[V28VX37]

Make you own undertrays.

Yes that's an option, have you tried that? It'd be great to hear experiences on what difference it makes.

[dori34]

maybe the top secret style rear diffusers for the coupes will work on the Sedan?

[Trex]

Yes that's an option, have you tried that? It'd be great to hear experiences on what difference it makes.

quite a few build on hardtuned that are dedicated track cars. some have seen great results with info on what part of wakefield it had the most effect.

[V28VX37]

maybe the top secret style rear diffusers for the coupes will work on the Sedan?

I'm pretty sure the under boot area is slightly different dimensions in the sedan compared to the coupe but perhaps with some modifications. I'll need to get the tape measure out.

quite a few build on hardtuned that are dedicated track cars. some have seen great results with info on what part of wakefield it had the most effect.

Cool thanks I'll see if I can find the right threads!

[V28VX37]

Found some good threads on the R34 GT-R rear diffuser:

http://www.sau.com.au/forums/topic/405318-r34-gtr-v-spec-rear-diffuser-aero-data/

http://www.sau.com.au/forums/topic/456810-r34-rear-diffuser/

This was really interesting, sounds exactly like what I'm after:

i put one on my previous GT-T and there is an easily noticeable difference at high speeds. Cruising around, nothing, but at 80-100km/hr+ you could definitely feel the car was more stable. Even my gf sitting in the passenger seat noticed it and she a) didn't know it was on b) i hadn't even told her i put it on. Maybe it's a bigger difference to a lighter GT-T, but you could definitely tell the difference.

there are naca ducts in the standard diffusers.

as for the Z-Tune diffuser having 2.2 times more downforce..... that's relating to the front - diffusers can be front and rear. The front Z-Tune diffuser is mix of CF and magnesium... looks sex, can't buy em though unless you're a Z-Tune owner (or know one i guess) - hate to think how much they are...

Maybe I'll just start with a cardboard stencil and DIY it ... what's some decent material for this? Aluminium, what thickness?

Edit: Also found that East Bear do a 4door rear diffuser (at a ludicrous price) so they do exist: http://www.nengun.com/east-bear/rear-bumper-diffuser-r34

Edited September 17, 2015 by V28VX37

[75coupe]

Need full undertray as just a rear diffuser will still allow airflow above and below rear diffuser, full undertray will prevent that

[V28VX37]

Need full undertray as just a rear diffuser will still allow airflow above and below rear diffuser, full undertray will prevent that

Yeah a full undertray would be better but I reckon having a rear undertray with a tight leading edge would still help.

I'm thinking something like in the GT-R rear section:

I'd love to make one out of aluminium if I had the skills (this is obviously the front):

Edited September 19, 2015 by V28VX37

[75coupe]

That front undertray looks great, ive been wanting to make a full undertray ever since i install a cf rear diffuser, i cant see how a rear diffuser will do much without a full tray

[V28VX37]

That front undertray looks great, ive been wanting to make a full undertray ever since i install a cf rear diffuser, i cant see how a rear diffuser will do much without a full tray

Yes indeed. Just to clarify, when I'm talking about rear undertray I mean the whole rear section, not just the diffuser. I agree a diffuser by itself probably won't do much.

[75coupe]

Keen to see the results, may give me some ideas...