Truenotch's BEAMS AE86 racecar discussion

[Truenotch]

9 minutes ago, Hyperblade said:

Use plywood as R&D first (with testing on track), then once your happy make the carbon version.

Yep, I think the foam core ACM panels I have in stock will get used for testing. If that works, I'm quite keen to attempt a PU foam core carbon splitter since we have all the equipment and supplies at work already. 

10 minutes ago, Hyperblade said:

One thing to note from an aero point of view, i was recommended to have my splitter go back to the firewall (and seal to it), and also seal off the wheel wells.

It's true that the further back you extend the plane, the better things will get, but it also adds more admin and makes it more difficult to keep engine bay temps down (which is already a problem with no splitter). Having said that, it's an option to add a fixed panel at the back of the engine bay later on.

13 minutes ago, GARDRB said:

Don't you work for some South Island billionaire? Can't you steal the heavily starched sheets from his AirBNBs and use them for your splitter?

Should I just steal the factory underfloor from this thing? 

[Hyperblade]

1 hour ago, Truenotch said:

Yep, I think the foam core ACM panels I have in stock will get used for testing. If that works, I'm quite keen to attempt a PU foam core carbon splitter since we have all the equipment and supplies at work already. 

It's true that the further back you extend the plane, the better things will get, but it also adds more admin and makes it more difficult to keep engine bay temps down (which is already a problem with no splitter). Having said that, it's an option to add a fixed panel at the back of the engine bay later on.

Should I just steal the factory underfloor from this thing? 

 

As with all aero what you should do is a trickly balance with being practical!

Temps were always my concern, takes some thinking to trying and keep some airflow through the bay.

At least steal the diffuser...

 

[Rhyscar]

Here’s one for the too-hard basket — but if I’d learned more about aerodynamics earlier, I would’ve realised that directing radiator exit air either ahead of or behind the front wheel wells is a much smarter choice than venting it out the bonnet. As it's a more efficient way to manage airflow. 

Inspired by BTCC setups, a V-mounted dual-pass radiator could help make this geometry work. It allows better airflow through the radiator and cleaner, more aerodynamically effective exit paths — either through the quarter panels or into the wheel arches — without creating lift or disrupting the flow over the top of the car.

Of course, it sounds simple… how hard could it be, right?!*

 

*Thanks ChatGPT for turning my rambling into something another human can decipher.. 

 

[Rhyscar]

On 07/05/2025 at 11:18, Truenotch said:

Should I just steal the factory underfloor from this thing? 

 

Man for the flashness of that car, the wheels are gross! Straight off someones uncles commodore. Hope they don't permanently live on that car?

[Truenotch]

3 hours ago, Rhyscar said:

Inspired by BTCC setups, a V-mounted dual-pass radiator could help make this geometry work. It allows better airflow through the radiator and cleaner, more aerodynamically effective exit paths — either through the quarter panels or into the wheel arches — without creating lift or disrupting the flow over the top of the car.

I'm not so sure about this. BTCC were heavily restricted with their aero and the cars weren't allowed extra vents. If they were allowed, you can almost bet they'd be venting out the top. 

Look at less restricted classes to see how they do it. LMP1/Hypercar, FIA GT3, Porsche cup, TCR and Time Attack all vent out the top. You can't tell me they wouldn't be venting all their air out the sides of the bumper if it was an advantage.

They're also really hot looking vents tbh.

 

Also FYI, chat GPT doesn't know the truth (yet).

[Roman]

The Alfa 155 DTM cars did the dual radiator thing where they come out in front of the wheels. But yeah I agree its likely more to do with rules than ideal aero. 
I am guessing much like BTCC, they werent allowed to change the body panels much or at all.
So werent allowed to chop a big hole in the bonnet, but modding the bumper was fine.
So it was probably just best way to deal with a bad situation handed to them by the rule book.

It's funny how many times race car stuff isnt "ideal" so much as, just best conforming to some really abstract constraints.

[Truenotch]

3 hours ago, Roman said:

The Alfa 155 DTM cars did the dual radiator thing where they come out in front of the wheels. 

It's funny how many times race car stuff isnt "ideal" so much as, just best conforming to some really abstract constraints.

I guess with the 155 is the engine was too far forward to have an effective exit duct? It's such a cool and weird car with a bunch of compromises for the 4wd system.

*Edit - After a google image search, no cars in dtm had bonnet vents until 2012. There must have been a rule change, because they've all had bonnet vents of some sort since then.

[Rhyscar]

Oh yeah that’s interesting and makes a lot of sense when you think about touring cars needing to represent production cars.
 

I started pondering the idea after watching one of your vids with the interesting aero guy (can’t remember his name or find the link again) and I think Connor interviewing him where he pretty much said it’s a hugely overlooked option for venting. And when I look at my car, and btcc cars, it makes a lot of sense because the packaging is so much nicer than going out the bonnet. Keeping aero restrictions low in the car would help the handling too (I know there’s a way better way to word this but you get what I mean) &nbsp
 

and then I thought about it some more and a car is wider than it is tall, so the air moving around the sides has been displaced as much, if not more than that going over the bonnet. And bonnet venting can be good, but the ideal placement of the exit duct can often be hard to achieve where you’ve got a decent pressure differential because of bonnet and windscreen shape etc. 

[mjrstar]

If you peel the "bonnet" off that audi I have a feeling it'd look a bit like an LMP car underneath, not like our modified production cars with hoses and brackets and crap everywhere. Just a nice smooth tunnel down each side of the bonnet.

Might be wrong though.

[Truenotch]

39 minutes ago, mjrstar said:

Just a nice smooth tunnel down each side of the bonnet.

Oh yeah, it'll definitely be two beautifully made dry carbon ducts from the cooler to the exit.

46 minutes ago, Rhyscar said:

I started pondering the idea after watching one of your vids with the interesting aero guy

Kyle (kyle.engineers on youtube). He's the host of the aero course too.

I think it would make loads of sense for your car, but it looks like a lot of work to fab the dual radiators and all the ducting. 

[Roman]

I guess another way to look at it - There are fast as fuck race cars, that do any and all of the above. 
So long as you are following some well established general principals I'd not get too hung up on the details for starters. 

I bet there's a fairly decent deadzone where you get similar results from lots of different ways of doing something. 
Where different wings or angles etc are a fairly linear drag vs downforce tradeoff.
Then you're chasing incredibly diminishing gains to optimize it all.

Might be time for some sideskirts? 🤐

[Roman]

3 hours ago, Rhyscar said:

and then I thought about it some more and a car is wider than it is tall, so the air moving around the sides has been displaced as much, if not more than that going over the bonnet. 

Here's another thought. 
You have a high pressure zone right at the nose of the car. 
then a low pressure zone right at the middle of the rear of the car. 

Why not run a big tube through the middle of the car, that joins the engine bay firewall to the lowest pressure area at back of the car. 

Turn your car into a donut for reduced cross sectional area. Haha

[Truenotch]

I can't find a photo, but there's an old time attack Evo (?) that had huge ducts running from the middle of the underfloor out to the back of the car between the tail lights. 

Apparently it worked, but you dont see anyone doing it these days.

Just like you won't see me running side skirts (for a while, at least).

[Truenotch]

Not the car I was thinking of, but interesting nonetheless: 

 

 

[Rhyscar]

Very cool. A bit of a blown wing situation going on there. Interesting that the feed comes from quite far back (probably restricted by diff position). Would be neat if it was ducted from directly behind the seats.. 

 

I guess aero gains are kinda split into two categories - bulk air flow redirecting/efficiency, and then the more fiddly details around flow separation and vortices. 

[Truenotch]

13 minutes ago, Rhyscar said:

(probably restricted by diff position)

That one's a FWD Civic (link), so I don't know why the duct starts so far back. The Evo I can't find had ducts starting from under the front seats.

[GARDRB]

On 11/05/2025 at 22:27, Roman said:

Turn your car into a donut for reduced cross sectional area. Haha

The cops would be alll over that one

[Roman]

Damn, sucks about the bonnet! 

I guess having some sort of "is bonnet shut" sensor or switch doesnt really help, because pins could still be out while the bonnet is sitting in its normal position. 

Seems inevitable to make this easy mistake eventually. 

Good work on the filter, I will award you max irony points if some swarf from making an air filter is what damages your motor finally. haha!

Did you manage to do any testing on other trumpet lengths?

[shrike]

 

 

1 hour ago, Roman said:

Damn, sucks about the bonnet! 

I guess having some sort of "is bonnet shut" sensor or switch doesnt really help, because pins could still be out while the bonnet is sitting in its normal position. 

Seems inevitable to make this easy mistake eventually. 

Good work on the filter, I will award you max irony points if some swarf from making an air filter is what damages your motor finally. haha!

Did you manage to do any testing on other trumpet lengths?

If you could insulate the pin so its only ground when it's in locked position and run a wire to an LED in the dash that turns on when the pins in

 ie use the pinlocks as a gnd switch that could work right?

[Roman]

I guess probably easier to just buy those hood pins that are visibly "up" when not locked. 

Ahh well all good in hindsight. Bet that was scary having bonnet up like that!