316 superlite

[varg]

This project is shaping up nicely, and I dig the sheet metal air dam you made. Tell me more about the design of your diffuser, the profile looks aggressive.

[petrolhead]

The E30 will always be nose heavy, I actually plan on similar mods to get mine closer to an even 1000kg. I haven't even begun to get into the small details that you've already done, so I am going to borrow some of your ideas.

I wish I had some ideas that contribute but your list includes everything I can think of.

The double edged sword is those sweet independent trumpets, they help with power but are heavier than a single TB setup.

A corner balance obviously will help too regardless of the total overall weight. Mine was able to get a perfect 50 cross.

Keep it up, good things are to come

I don't believe it has to be nose heavy. My car is 53:47 at the moment, with a fat 103kg driver. If I moved say the battery to the trunk, it's not only minus 8 kg from the front, it's plus 8 to the rear. In short, moving 1% has a 2% effect on weight distribution. My wallet allowing, theres loads of stuff I can shave or move from the nose. Getting the engine/box rearwards would be good. Plus the further back I get them, the lower polar moment of inertia the car would have.
Right now I'm only concentrating on making it drivable for one short summer. Mind you we keep our cars tucked away from October to April :/.

This project is shaping up nicely, and I dig the sheet metal air dam you made. Tell me more about the design of your diffuser, the profile looks aggressive.

Thank you sir.
The diffuser is 105cm from start to finish and 58?cm wide. Lowest point is just under the diff. It has a constant radius. I've seen many DIY diffusers that are angled but not curved. Curvature means smooth transition, the air flow is more likely to stay laminar. Plus, curved means the air travels a longer distance which should means accelerated speed which should mean pressure drop. The exit point is 28cm higher than starting point, trailing edge is about 26 degrees. In the pics it lacks plates that go in the middle. Bit like the vertical sides but smaller and shorter. If nothing else, removing spare wheel well and cutting open the rear valance will remove a massive air brake. My mods do have some effect.. The rear lights and plate now gather snow/sand madly quickly.

[varg]

Thank you sir.
The diffuser is 105cm from start to finish and 58?cm wide. Lowest point is just under the diff. It has a constant radius. I've seen many DIY diffusers that are angled but not curved. Curvature means smooth transition, the air flow is more likely to stay laminar. Plus, curved means the air travels a longer distance which should means accelerated speed which should mean pressure drop. The exit point is 28cm higher than starting point, trailing edge is about 26 degrees. In the pics it lacks plates that go in the middle. Bit like the vertical sides but smaller and shorter. If nothing else, removing spare wheel well and cutting open the rear valance will remove a massive air brake. My mods do have some effect.. The rear lights and plate now gather snow/sand madly quickly.

There is certainly some effect, though there is going to be some efficiency lost with the relatively large angle and the radius of the curve. Diffusers are by nature in a region of low energy flow, particularly on a car that lacks a full undertray. The lower velocity, more turbulent airflow under the car limits the angle you can use without boundary layer separation significantly. Even cars with relatively aerodynamically optimized designs and full body undertrays usually use a less aggressive radius for curved diffusers and/or shallower average angle than what it would appear is present here.

Are you planning on putting an undertray on your car? It would make a world of difference aerodynamically, and would increase the effectiveness of your diffuser significantly. There would be some weight added though which doesn't seem to be in the theme of what you've done so far. With aero on a car like yours there's no one answer, it's just figuring out what is worth the time and effort and added weight. In my opinion the small amount of weight added with an aluminum undertray would probably be worth it for the reduction in drag. There are worse cars than the E30 when it comes to under body airflow, but it certainly isn't a pretty picture down there.

[petrolhead]

Most certainly I'm thinking of an undertray. Not an easy task if you want it to cover a lot of the undercarriage, but ofcouse smoother is always better. In an ideal situation the whole underside would be of the shape of a wing's underside.
Anyway, I've got more boring/ordinary things to iron out right now.

[petrolhead]

There is certainly some effect, though there is going to be some efficiency lost with the relatively large angle and the radius of the curve. Diffusers are by nature in a region of low energy flow, particularly on a car that lacks a full undertray. The lower velocity, more turbulent airflow under the car limits the angle you can use without boundary layer separation significantly. Even cars with relatively aerodynamically optimized designs and full body undertrays usually use a less aggressive radius for curved diffusers and/or shallower average angle than what it would appear is present here.

Are you planning on putting an undertray on your car? It would make a world of difference aerodynamically, and would increase the effectiveness of your diffuser significantly. There would be some weight added though which doesn't seem to be in the theme of what you've done so far. With aero on a car like yours there's no one answer, it's just figuring out what is worth the time and effort and added weight. In my opinion the small amount of weight added with an aluminum undertray would probably be worth it for the reduction in drag. There are worse cars than the E30 when it comes to under body airflow, but it certainly isn't a pretty picture down there.

One thing I gotta mention.. lot of people are very skeptical about these DIY aero-thingies. Either the design is wrong, or the argument is that "E30 doesn't go fast enough to benefit from wings" etc. I've heard every joke and sarcastic comment about them.
After we got ~50kg of measurable downforce from a fairly modest DIY rear wing, it changed my view. This was on another E30 that had a top speed of 160 km/h.

I've been thinking about making an undertray from thin plywood. It's light, easy to work on and cheap. I don't expect version 1.0 of anything I've made to serve for very long, so why make it from something so expensive you'd mind breaking.

[petrolhead]

The car developed a nasty overheating tendency. I was ready to pull the head. I abandoned it for a few months and consentrated on my buddy's time attack-E30 instead.

However I decided to try it with a new waterpump, bigger radiator and opening up the front opening of radiators front tunnel. Seemed to work. Still leaks oil.

Couple pics of the racer.





I built two LSD's for the car, a 4,45 and a 3,64 (for faster circuits)


First time out we came 3rd. That's me fiddling with the rear tyre


If my car should hold together I'll try to tune the engine mapping and suspension. Hoping to be able to attend a trackday or two this summer.

[Bearmw]

Looking good man.

[econti]

Am I alone in loving drilled bumpers like that

[petrolhead]

Does that pic link^ work?

The parking signs in the background say "for low emissions cars". In my neck of the woods these parking spaces actually exist :). Do these exist anywhere else?

[pazi88]

You still run e85? Then it's in right parking spot :D

[petrolhead]

Yep RE85. Ecopower multifuel Bluemotion :).

[alistairolsen]

Just been through this over a few days, very cool build!