LS430 simplification build

[freebeard]

Originally Posted by Logic

...without an aero mod in sight...

With the bare metal engine compartment have you thought about the aerodynamics of that compartment interior?

My thinking would be full bellypan with louvers at the rear corners of the hood, to throw hot air around the A-pillars.

[Macskyver]

Originally Posted by Logic

I assume we are talking 1 pipe back from 1 turbo, not 2 as in the pic?

Area of 3" circle = 7.07 square inches.
Area of 2" circle = 3.14 square inches X 2 = 6.28 square inches.
So somewhat of a restriction in the pipes yes, and turbos like backpressure even less than normally aspirated cars do.

But more important is the restriction in the mufflers.
Apparently mufflers worth the name come with a CFM rating.
For power, you want to divide that CFM # by the engine power (desired) and get a number above 2.2 (David Vizard)
Should be similar for economy unless you plan to dawdle around at nothing over 2000 rpm!

Also NB that a turbo does a pretty good job of silencing exhaust, so you can probably get away with one muffler per pipe.
IMHO two or three very free flow mufflers per pipe flow and sound better than one restrictive muffler. This is what BMW does.

I also NB that turbos send the exhaust down the pipe in a spiral.
Now a piece of string spiraled around the exhaust is much longer than the exhaust when straightened out.
That means that the spiral flow after a turbo is to be avoided and should be engineered out.


As you are not averse to swinging spanners at a car/engine, pgfpro's posts on running super high compression and super lean to get 50mpg (IIRC) without an aero mod in sight are well worth the read.
NB that in town driving: 68% of energy is used accelerating weight vs 14% overcoming aero drag.

You are correct, there would be one larger pipe coming from the turbo (on the passenger side) and then splitting toward the center. I have no idea what the CFM rating is on the factory LS430 mufflers. I imagine they are decent as the car had about 300 hp. That's also with the restrictive center section, which is under 2.5" diameter. Assuming it was the full 2.5", the cross section would be 4.9 square inches.

I like the idea of basically cutting everything off forward of the hangars (behind the resonators) and using something like this: https://www.borla.com/products/proxs...-muffler-40670 to split the 3" pipe to duals. I can run the factory rear mufflers and piping initially to see how it works and replace it at a later date if I find it to be insufficient. That would save me a ton of work as there's not a lot of space to snake the exhaust pipe around the IRS. It would also keep me from messing up the under body aero. I've had really good luck with those Borla pro xs mufflers. In my experience they are extremely quiet and free flowing. Just running that muffler by itself and deleting the factory mufflers would probably work great as well, especially considering the noise reduction of the turbo.

[Macskyver]

Originally Posted by freebeard

With the bare metal engine compartment have you thought about the aerodynamics of that compartment interior?

My thinking would be full bellypan with louvers at the rear corners of the hood, to throw hot air around the A-pillars.

I haven't really thought about that, but it's a good idea. I would do that just to get rid of the excess heat in the engine compartment. I am pretty sure that is a flaw with these cars. I think that is one reason why all the wire harness connectors in that area get super brittle. A big fat turbo under the hood will not help the under hood temperatures either.

Vents aimed at the A-pillars help with aero? How significant is the impact? Can you explain the theory a little bit?

[freebeard]

In the seventies, Morelli collaborated with Pininfarina's Fioravanti and Antonello Cogotti again to develop the CNR-PF, a four-seat passenger car with a drag coefficient of 0.172. The CNR-PF eventually became a Pininfarina Concept car in 1990

https://newatlas.com/1960-pininfarin...auction/35369/

This article is on another car. aerohead will have all the details, but those vents over the front wheelwells were sucking on the engine compartment.

[Logic]

Originally Posted by freebeard

With the bare metal engine compartment have you thought about the aerodynamics of that compartment interior?

My thinking would be full bellypan with louvers at the rear corners of the hood, to throw hot air around the A-pillars.

Hmmm... there is no difference in the angle of the windscreen and hood in the prototype.
ie: No high pressure area just in front of the windscreen.
To me it looks as if that vent is in the area where the hood becomes parallel to the side/s.

The std nowadays is:


Based on:


ie: suck the radiator air out using the low pressure area on the nose at around the point where the bonnet becomes most parallel to airflow.


Then there's this study on how best to institute a bellypan so the exiting air is leaving under the bottom of the car parallel to airflow direction:
https://ecomodder.com/forum/showthread.php/cooling-air-flow-backward-rather-than-downward-41539.html

Also NB my extract air to vents in that low pressure area at the front of the roof, via the A pillars in the same thread linked above.

Then there's this exhaust exaction idea:
https://ecomodder.com/forum/showthre...ift-41537.html

[Macskyver]

Originally Posted by Logic

Hmmm... there is no difference in the angle of the windscreen and hood in the prototype.
ie: No high pressure area just in front of the windscreen.
To me it looks as if that vent is in the area where the hood becomes parallel to the side/s.

The std nowadays is:


Based on:


ie: suck the radiator air out using the low pressure area on the nose at around the point where the bonnet becomes most parallel to airflow.


Then there's this study on how best to institute a bellypan so the exiting air is leaving under the bottom of the car parallel to airflow direction:
https://ecomodder.com/forum/showthread.php/cooling-air-flow-backward-rather-than-downward-41539.html

Also NB my extract air to vents in that low pressure area at the front of the roof, via the A pillars in the same thread linked above.

Then there's this exhaust exaction idea:
https://ecomodder.com/forum/showthre...ift-41537.html

That's very interesting. The factory air intake on the car is right above the radiator in the center of the car. It's almost like the Lexus engineers knew what they were doing. I do know that they used the same wind tunnel to develop the LS430 as was used to develop the high speed bullet trains. There's definitely a lot of though already put into the aero of the car.

If I read that figure correctly it seems like I should use the factory air intake location, and that I can place hood vents really anywhere. One thing that gives me pause is that there is weatherstripping around the hood. I think the intention must have been for the air to travel underneath the car. The car has a lot of belly pan pieces from the factory, but they are pretty gnarly from oil leaks etc.

[freebeard]

Logic -- Half-bake brain f*rt?

the 'std' that you espouse removes radiator flow from the engine compartment.

Agreed, a flap controlling s Meredith Effect vent at the rear of the engine compartment bellypan is optimal. Not that front engine cars are optimal to begin with.

[Logic]

Originally Posted by freebeard

Logic -- Half-bake brain f*rt?

Your STD solution removes radiator flow from the engine compartment.

'My STD solution' is not my std solution: It's what most all modified saloon cars use...

IMHO what they are doing is redirecting most of the heated engine bay air to exit into an area of low pressure, (negating aero lift in the process) so that there is no longer any need to exhaust that large a volume of air under the car where it ads to drag and lift.

No doubt there are extra vents for the engine compartment itself, but as that air isn't pre-heated by the radiator, you can get away with much less of it.
That means much less air forced to exit under the car...
I would still use the 'air exits belly-pan directed backward' trick of the study, by implementing a somewhat longer, slightly lowered (and sprung) at the back belly-pan.
Then one might possibly look at the aero in that exit area.

Originally Posted by freebeard

Agreed, a flap controlling s Meredith Effect vent at the rear of the engine compartment bellypan is optimal. Not that front engine cars are optimal to begin with.

IMHO the trick to the Meredith effect is to have the area of largest volume/pressure just ahead of your heat source.
ie: Create a cool, high pressure area just ahead of a heat source, to act as a kind of one-way valve.
Then the heated/expanded air is in a convergent, ever faster moving / lower pressure area, adding thrust. (or at least some speed up of the exiting air, lowering drag/turbulence where it merges with the fast/er outside air)
That's how Ram Jets work too.

That makes the Meredith shape much easier to implement with a radiator than with a whole engine (and bay) of random shape of varying temperatures.
But yes; an adjustable, slightly swiveling, hinged in front belly-pan, sprung to 'bump up' if necessary, would allow one to find the optimal opening size.

The thing is to keep weight down while doing all this.

[freebeard]

'My STD solution' is not my std solution: It's what most all modified saloon cars use...

That was inappropriate and I apologize. I'll change it to ' the 'std' that you espouse.

So now I'm wondering what's the minimum viable Tesla one-way valve.

Coincidentally, JEGS sells a Chevy 350 ramjet crate engine.

[Logic]

Originally Posted by Macskyver

That's very interesting. The factory air intake on the car is right above the radiator in the center of the car. It's almost like the Lexus engineers knew what they were doing. I do know that they used the same wind tunnel to develop the LS430 as was used to develop the high speed bullet trains. There's definitely a lot of though already put into the aero of the car.

Yes; many performance orientated cars now have the engine intake going over the radiator to something of a forward facing Bell Mouth (Some small Ram Air effect) in the cool/denser air ahead of the radiator.

VW Golfs etc do this and this guy has tested a number of aftermarket intakes.
NB that while the engine still sucks more than the wind blows air into the intake, there is a decrease in the amount work the turbo/engine has to do at sucking in air.
Also NB that any sucking in air from the front somewhat decreases the frontal area and thus aero drag of the car...

Ideally you'd want 2 (Bell Mouthed) intakes with an automated valve:
One as above and ahead of the front grille too.
And another taking in hotter air from behind the radiator and somewhat close to the exhaust.
The hot air intake would be for economy, thx to better vaporization and something of an Atkinson compression stroke effect.
The cold ram air intake for when you want power.
Then some sort of control system based on temperatures, load, throttle position etc.

But that's the ideal and thx to the complex control system required; not something easy to DIY.
Besides all this ads weight (and complexity) and in urban driving; 68% of fuel is used accelerating mass, vs 14% overcoming aero drag, so light and simple wins out until some serious research is done by a car company.

Originally Posted by Macskyver

If I read that figure correctly it seems like I should use the factory air intake location, and that I can place hood vents really anywhere. One thing that gives me pause is that there is weatherstripping around the hood. I think the intention must have been for the air to travel underneath the car. The car has a lot of belly pan pieces from the factory, but they are pretty gnarly from oil leaks etc.

Looking at the figure; you'd definitely want this in and around that area of lowest pressure.
ie: that 1st downward spike in the graph.
IMHO that area on any car starts where the nose has just finished curving from vertical to however close to horizontal the hood ever gets and does not extend back very far at all...

Weatherstripping:
If you want to block (engine) noise; you go airtight, with as thick and dense a 'wall' as possible. (thick=impractical; heavy)
ie: While the weatherstripping may block some rain ingress, it's main purpose is to seal of any avenues of noise (sound waves) egress in areas close to and upwind of the driver's/ occupant's ears.
The venting of the engine compartment air below the car gets the sound wave avenue as far from and 'downwind' of said ears as possible and the whole car underside acts as something of a muffler.

If you were to build such a radiator vent; ideally you'd want the same weather-stripping sealing the gap from the vent, to around the (aero) slot in the hood when it's closed.
The radiator is not a vibrating etc noise source, fans excepted.
ie: The hood remains as noise and air/water tight as usual, except for the exit slot from the radiator/s.

A hood vent / (aero) slot in the right place, but without that below hood duct would work to minimize 'below the car exit flow' to a certain extent however.
Simple and light is good. And rain wont be going in against the airflow at anything above a couple of mph.
NB that as much or more rain is coming in the stock grille, through the radiator anyway and splashing up from below etc, so the under hood electrics should already be waterproofed enough.

(Then if you really want to go to the N'th degree; you vent the after radiator engine bay air to a slot in the roof (that 2nd low pressure downward spike in the graph) via the A-pillars!

That's just an idea of mine. At this time... but I expect it will eventually 'magically' appear in future rally etc cars. )