Body Kits / Aero Parts

[TRS]

@NoHaveMSG: Yes Sir!

Originally Posted by churchx

200mph? I predict one may also hit max speed limit in ecu tune, if one uses stock ecu. Wasn't there something like 235-245kmh max, even if car could have went faster? (and something like 180kmh in JDM twins).
Was going to suggest hood louvers to reduce front lift to compensate rear downforce/keep aero balance, and only then noticed mention of vented hood.

Im LS swapped. Car already does 185 MPH:

https://www.instagram.com/reel/Ci5rd...d=YmMyMTA2M2Y=

[churchx]

LS swapped street legal in Germany? o_O

[TRS]

Originally Posted by churchx

LS swapped street legal in Germany? o_O

Yes Sir. Street legal in Germany. 100% Homemade. Want to learn more? Click here.

BTT...

[x808drifter]

Hood vents, a rear wing and a splitter.
Not a giant one, but definitely something that attaches in the middle.
Rear wing is more for lateral stability than downforce.

Angle of attack does matter.

[TRS]

Originally Posted by x808drifter

Hood vents, a rear wing and a splitter.
Not a giant one, but definitely something that attaches in the middle.
Rear wing is more for lateral stability than downforce.

Angle of attack does matter.

Thanks for that input! Concerning rear wing, I would consider this more a aero part which adds downforce for the tradeoff of adding also drag. With other words not the most efficient aero part. Though, I can Imagine that it adds stability, but so gar this not a concern yet. So my plan so far was go with Just the existing TRD ducktail (I maybe should have mentioned eralier).

For the splitter, what exactly is meant with "attached at the middel"?

[soundman98]

Originally Posted by TRS

seems to me that the way the underbody panel is made, it could be acting as a parachute for any air funneled through the drive shaft tunnel. how does that air get out of the back bumper?

also, have you tried running without a hood? that would help to determine if the hood venting/aero is what caused the front end lift at 200mph.

[churchx]

Originally Posted by soundman98

seems to me that the way the underbody panel is made, it could be acting as a parachute for any air funneled through the drive shaft tunnel. how does that air get out of the back bumper?
also, have you tried running without a hood? that would help to determine if the hood venting/aero is what caused the front end lift at 200mph.

As openings, i see space around exhaust tips.
But imho you overestimate parachuting impact/drag. Think of how vertical spoilers on back of some cars can work, or that many airplanes don't have doors completely closing off retracted gear, and still don't have much extra drag due that. Also i'd certainly wouldn't aim to close airflow completely. There is reason why many aero part makers often leave some openings by design in underbody panels - for example to cool LSD diff. If there are products like casing with extra cooling ribs or even external radiators for diffs, no cooling might be wrong choice.

[TRS]

Based on my tuft test results the area above the rear diffuser is not pressureized. Some tufts was beeing sucked through the gap between rear fog light and bumper. So the pressure infront of the rear bumper is lower then behind. The idea was to use the exhaust flow as a kind of ventury style suction thing. Dont know If that works or If it is simply caused by the low pressure region of the diffuser which, unfortunately, is connected to the area above the diffuser due to the necessary exhaust cutout.

Anyway, Im planung to close the undertray to a flat floor as far as possible. There will be NACA ducts needed to cool converters, tranny, differential and driveshaft. As well the cutout for the exhaust besides the differential has to stay. There is simply not more room and this is only a 3" pipe. Im planning to go for a 3.5" pipe since I have very high gas velocity in the exhaust. Only thing I will be able to optimize in that area is the opening directly under the differential. This will be closed in a future revision of the diffuser. How exactly is not clear yet. Im considering to weld cooling fins to the lower side of the diff housing which lower edges are flush with the diffuser plane. This, at the same time, could act as an air vent/exit for the NACA inlets upstream in the tunnel.

[churchx]

Originally Posted by TRS

... Anyway, Im planung to close the undertray to a flat floor as far as possible. There will be NACA ducts needed to cool converters, tranny, differential and driveshaft. As well the cutout for the exhaust besides the differential has to stay. There is simply not more room and this is only a 3" pipe. Im planning to go for a 3.5" pipe since I have very high gas velocity in the exhaust. Only thing I will be able to optimize in that area is the opening directly under the differential. This will be closed in a future revision of the diffuser. How exactly is not clear yet. Im considering to weld cooling fins to the lower side of the diff housing which lower edges are flush with the diffuser plane. This, at the same time, could act as an air vent/exit for the NACA inlets upstream in the tunnel.

IIRC some makers were making alternative diff casings that provide both larger oil volume for diff and those cooling ribs. For example Cusco (also ports to attach external cooling rad, if needed). So not sure it's worth custom making own. Then again, your max speed build probably is meant for straight line? LSD diff generates heat when car corners a lot, such as on track. Probably it will work less in straights where max speed is attainable.
P.S. speaking about aero mods .. - what do you think of round covers for wheels faces to smoothen flow/reduce drag? (IIRC some porsches had such). I'd also think of reducing drag by mods to some smaller bits, like side mirrors/antena.

[NoHaveMSG]

Originally Posted by soundman98

seems to me that the way the underbody panel is made, it could be acting as a parachute for any air funneled through the drive shaft tunnel. how does that air get out of the back bumper?

also, have you tried running without a hood? that would help to determine if the hood venting/aero is what caused the front end lift at 200mph.

It should be okay since the flow should be mostly attached to the floor.

The only thing that caught my eye was the vortex generators on the central section of the diffuser. I hadn't seen that before but am not versed well enough to know if it's good/bad.

[norcalpb]

Originally Posted by TRS

Hello all,

actually this post is more a question. But I didnt know where Else to put it since, surprisingly, there is no section for functional aero mods in the forum. (Or Im just too dump to find it)

So first things first, here is a pic of my self developed rear diffuser:



Now my question: Im considering to aim for the 200mph mark. Is somebody arround here expierienced with high speed behaviour of the 86 chassis in matters of aero?

To be very clear right away, I do NOT talk about giant Front splitters for timeattack racers. The car is and shall be street legal (in Germany if you know what I mean...). Im currently investigating my options to reduce overall drag while improving or at least keeping downforce (or better said lift) conditions of the car. In order to maybe giving kind of a frame, the inspiration/attitude of this build is the YellowBird Porsche. (What does not mean that I would actually compare my build with this masterpiece of automtive engineering)

Currently Im topping at round about 185-188mph, depending on conditions. The car feels still stable at those speeds and already accepted a little jump at arround 180mph without getting nervous. I had oversean a bump in the road what caused short lose of ground contact.

My current aeromods are minor. I have a guided radiator airflow by a radiator scoop & ducting, a vented hood (equal seibon TS Style), a bottom line kit equal to HT Autos (which was more intended for optical appearance, but the front lip actually makes a mesureable difference in top speed) and my rear diffuser. The car is slightly lowered on B16 coilovers, front Ride height about 3" and round about a 1" rake. Rims are currently way to wide and sticking out the fenders, what is one of the first things I will adress for drag reduction.

My planned further steps:
-changing 9.5" to 9" wheels with a Offset to ensure they are not sticking out the front silhoutte
-full flat underbody with a small exemption near the differential since I otherwise have no options to route a big enough exhaust pipe
-increasing power from currently 450 to ~520 flywheel hp
-custom setup Öhlins coilovers with spring rates and valving to match my exact wheel loads and as well some more freedom for Ride height adjustment without blocking out the dampers (Im expecting some gains concerning drag with slightly lower ride height, Im aiming for about 2" Front)

So If theres anybody out there having expierience with modifications of the 86 chassis for this kind of aero I would appriciate any contact to exchange some thoughts and knowledge.

PS: Mods, If theres any better section for this Post, please move...

Thanks in advance!

Do you have any of the TRD trinkets installed? Not sure if they do anything, but they sure are priced like they do!

[TRS]

Originally Posted by norcalpb

Do you have any of the TRD trinkets installed? Not sure if they do anything, but they sure are priced like they do!

Thats a good one. Yes, the rear window Aero cover is something I was considering earlier, but somehow forgot about that...

@NoHaveMSG Concerning Vortex generators: they wasnt my inital Intension, but they are necessary. You See that bent half way Up the middle diffuser tunel? This is die to space requirements for the muffler,so it Can't bei erased. Die to that bend the AOT of the rear section is Higher then intended and actually tuft test proofed that it is too high to keep airflow attached. Therefore I was forced to introduce VG's to re energize boundry air layer. Tufts now are still flikering due to vorticees caused by VG's, but they are at least poonting to the rear of the car and Not, as before, Vice versa.

Edit: Just remembered that I also Made a video of the tests.