2002 Celica Modification (Grill Block)

[aerohead]

Originally Posted by aardvarcus

Thank you for your comments Aerohead; I am sure you have realized that I am getting most of my ideas from you. Currently my fully open grill sizes are 230 in^2 lower and 100 in^2 upper. (Ignoring the side grills and reducing for the aluminum angles the grills mount to. These are “blocked” with 40% open mesh, resulting in net open area of 92 in^2 lower and 40 in^2 upper. Assuming a vena contracta of 0.64 for the sharp orifice, this nets effective grill area of 59 in^2 lower and 24 in^2 upper or roughly a 3/4ths block. In the winter I ran additional partial lexan blocks behind the grill mesh, resulting in net effective of 30 in^2 lower and 4 in^2 upper, or roughly a 7/8ths block.

I would like to use aluminum for anything I add to my grill. I have looked, but been unable to locate a trash can lid of the proper shape and size. I have also searched for pots, pans, vases, bowls, funnels, etcetera but have not located the proper shape and size. What I have found that are aluminum and the correct shape are velocity stacks for cold air intakes and carburetors. The carb ones are approximately 8.5” inlet and 5.13” outlet, and the cold air ones are a 7” bell with a 3” to 4” outlet. If I were to use the carburetor one, what figure would be best used to compare the amount of air it will flow to what I currently have? Calculating the area based on the inlet would produce 57 in^2, but using the outlet would be only 21 in^2.

I am assuming there is a flow advantage to using the streamlined intake shape as compared to the adjusted area of all the little holes I presently have, but I don’t think that fact is enough to make up for the further reduced area I will have unless I use multiple of the smaller intakes. The only other option I can think of is to make one, however I think I would end up with a wider rectangular type of shape with rounded edges, not an ideal 3d spherical form. I had also considered getting one of the smaller ones, cutting it in half, welding a curved top and bottom piece in that matched the profile, and turning it into a rounded rectangle of sorts, but that would be a lot of expense.

Aerohead, another question I have is do you have any sort of ducting directing your intake air to your radiator? If so is it streamlined? I presently don’t have a duct, but I did block off most of the areas I didn’t want the air to go.

Lastly I am presently working on making some tire spats fore and aft of each of the wheels. I am basing my design loosely off of what they did on the ford probe, except making it out of conveyor belt type material, hopefully in a way that will stand up to rough roads.

Walter Korff of Lockheed Aircraft recommended using the dimensions of the radiator core as the basis for inlet design dimensions.
He advocated an opening which was as wide as the radiator,but only 1/6th as tall,into an airtight diverging duct which was as deep as the full height of the core.(All NASCAR teams use this inlet)
This would handle the full heat flux of the engine under full load.(Racing)
I choose my trashcan lid according to Korff's rule-of-thumb,but at Bonneville realized it was too large since I never actually got to full power,and was so indicated by the temp. gauge.
So I dumpster dived at the Dollar Store in Wendover for cardboard boxes and taped up half of the opening.
I'm at 1/12th radiator area and I'd driven on to Carson City,Nevada,and back home with the cardboard,registering the highest mpg to date.
Once home I duplicated the block with sheet aluminum.
It's on the truck right now and will remain.
I'd let your radiator be your guide.
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There are aluminum and plastic Jello molds that might have some diameters of interest.Architectural supply houses can provide aluminum waste receptacle lids of many sizes.(Love Field in Dallas has amazing jet-turbine inlet trashcan lids in all the restrooms).
Also,some commercial rooftop exhaust fans have an inner fairing concealed within the main housing which has an ideal leading edge inlet.
The aluminum Jello molds you'll most likely find in antique shops.Thrift stores will have the plastic.
Go by the outlet diameter,this is your critical dimension.

[aardvarcus]

Once again, thanks to everyone for all the help and advice.

Ok, all the rest of the aluminum underbelly panels came off yesterday. They would vibrate going down the road, among other issues I was having with them. Version 2.0 will definitely be made of coroplast. I left a few of the aluminum angle pieces mounted to be used as mounting points for 2.0.

In other news the aluminum grill mesh and lexan covers are also slated for removal. I am now thinking of plain black grill blocks on all the openings, and I can incorporate an appropriate cooling air inlet in the one main one. I am out of the “make everything out of aluminum” phase, so some cheap plastic curved items are in my future. Black spray painted plastic is much more economical. I am thinking of starting with a block the radiator width and 1/6 the height and a real duct. I could then start blocking the width of the opening to fine tune the size.

My “radiator duct” was a part of the aluminum pan which is now removed, so the air through the grill is once again going under the car not through the radiator. The airflow entering the grill is much less restricted since it isn’t going through the radiator and the car engine bay was a lot warmer driving to work this morning, so my MPG actually went up from the pan removal. The downside is that it will be hot all the way home, hopefully not to the point of overheating. It was already heating up and kicking the fans on this morning.

My “Aerodynamics of Road Vehicles: From Fluid Mechanics to Vehicle Engineering” got here last week, so I have been reading that with fascination. Thanks to that book, I will try to have better questions to ask.

[aardvarcus]

Alright I dreamed up another crazy idea. I have been studying the radiators section of Hucho’s book and several of the drawings posted on this site. In Hucho’s book, a radiator inlet low on the front of the car and exhaust up on the hood was stated as most efficient, but only practical for race cars. Most of the other opinions I have read are to dump cooling air out in the wheel wells or under the car at the rear of the engine bay.

Well I did some measuring, and this is what I came up with. My radiator is 14” tall and 25” wide mounted at an angle with the base about 10” from where the grill opening is. What if I did a duct at the front bottom that was actually under the current front of the car. It would be at the lowest point on the front bottom, but it would be out of view. A 2” opening 25” wide would get me close to the 1/6 ratio, and my duct would be 10”, or 71% of the 14” height. A picture is worth 1,000 words, to it is attached.

My way of thinking, this idea wouldn’t be that different than doing a 2” air dam and mounting the 2” opening just above the air splitter. The inlet side of the radiator would be sealed, and the outlet side would be semi sealed by belly pan/hood/etcetera and would dump the air out in the back of the engine bay, or maybe by the wheels.

Will this work? Do I need to radius the bottom lip of my inlet opening? Thoughts or ideas are welcome.

[jeff88]

How would this benefit more than just having a 2x25" opening in the bottom grill. I would think smoothing out the belly completely and just having a small opening in the front would be more beneficial, but you got the holy aero bible, so you would know better.

Although, you may benefit even more if you do what you say in your diagram, but instead of an opening with an angle (which creates a parachute), you could have a completely flat belly with NACA ducts. That is my plan for my belly pan, whenever I get around to it.

In your diagram, you have the air escaping out the bottom, but why can't you exhaust out the top, up and over the windsheild like Hucho mentions (other than having to cut the hood open)?

[aardvarcus]

Thanks for your comments.

How would this benefit more than just having a 2x25" opening in the bottom grill.

If I don’t do this, that is exactly what I will do. I don’t know that this would be better, just different. I already have my aluminum grill cover made, so if I put some lexan or black coroplast behind it I can have a decent looking (to me) 100% grill block with little effort. I have not yet thought of a good easy way to incorporate a 2”*25” radiused opening into the lower grill area without completely changing my design and starting over on all my grill blocks. (Yes, I care a little how it looks.) Anything I do under the car can look like whatever it wants, doesn’t have to be pretty if it is hidden.

Also after reading some about the airflow under the car, I thought it wouldn’t be a bad place to “rob” the cooling air from. My way of thinking it should give similar effects to having a small air dam.

I would think smoothing out the belly completely and just having a small opening in the front would be more beneficial, but you got the holy aero bible, so you would know better.

If I thought that I knew better, I wouldn’t be asking questions. Most things I have seen put the intakes low on the front nose of the car. My way of thinking about it, this intake would still be on the front of the car, and even on the nose of the car, it is just below where the other styling features of the car stop. It is almost like dropping the nose 2” (like an air dam) and then putting the inlet right on the bottom.

Also after previous experiences I won’t be smoothing the belly completely, just partially. I will leave the exhaust components out in the open.


Although, you may benefit even more if you do what you say in your diagram, but instead of an opening with an angle (which creates a parachute), you could have a completely flat belly with NACA ducts. That is my plan for my belly pan, whenever I get around to it.

I had considered making it NACA like, but you have to have smooth flow on a surface for the NACA to work properly, I don’t know I have smooth flow right there. I am thinking of my design more like a normal grill opening, utilizing the high pressure at the front of the car to ram the air in.

In your diagram, you have the air escaping out the bottom, but why can't you exhaust out the top, up and over the windsheild like Hucho mentions (other than having to cut the hood open)?

Can’t say I didn’t consider it, but I don’t really want to cut my hood open. Hucho also warned about the heated air going into the fresh air intake on the cabin. Others have warned about dirty water getting on the windshield. It would be interesting to test if I happened upon a spare hood.

[9646gt]

Just keep it clean with the mods Owned lots of Celicas and I can tell you that the percentage of GTS models and with a 6speed on top of that AND action package are not very common these days.

[aardvarcus]

It’s been a little while, so I figured I would give another update on my car. My large 10% oversized tires were wearing down (the front ones especially), so I decided to order another set. It was hard to take off from a stop with these 26.5” diameter 10% oversized tires without chirping them, which I believe is what wore them out so quickly.

These had already saved me more than enough fuel to justify their early replacement though, so I am not too worried about it. I decided to go in a slightly different direction this time, and purchased a set of 15” wheels off of a Prius and got Michelin Energy Savers in 195/65/15, or roughly 25” diameter, so more like 4% oversized. The obvious downside is my RPMs went up about 6% from where they were, but the advantages are that the car is lower to the ground and these wheels and tires are significantly lighter. Tire went from 22.8 to 18.4. Wheel went from around 21ish to around 14.5ish (lost my exact figures). This is pretty significant to lose 40+ lbs. of rotating weight on a 2500lbish car.

I have run three full tanks through it now and am most of the way through the fourth, and I have not noticed a significant change in fuel consumption positive or negative, so I think the rpm change was counteracted by the lowering and weight savings. The other advantage I have not yet attained is the ability to put my stock wheel well liners back on the car, so that should add additional advantages.

I am starting to work on version 3 of my grill blocks and version 2 of my belly pan, my truck transmission swap had been taking up most of my limited free time.

[aerohead]

Originally Posted by aardvarcus

Alright I dreamed up another crazy idea. I have been studying the radiators section of Hucho’s book and several of the drawings posted on this site. In Hucho’s book, a radiator inlet low on the front of the car and exhaust up on the hood was stated as most efficient, but only practical for race cars. Most of the other opinions I have read are to dump cooling air out in the wheel wells or under the car at the rear of the engine bay.

Well I did some measuring, and this is what I came up with. My radiator is 14” tall and 25” wide mounted at an angle with the base about 10” from where the grill opening is. What if I did a duct at the front bottom that was actually under the current front of the car. It would be at the lowest point on the front bottom, but it would be out of view. A 2” opening 25” wide would get me close to the 1/6 ratio, and my duct would be 10”, or 71% of the 14” height. A picture is worth 1,000 words, to it is attached.

My way of thinking, this idea wouldn’t be that different than doing a 2” air dam and mounting the 2” opening just above the air splitter. The inlet side of the radiator would be sealed, and the outlet side would be semi sealed by belly pan/hood/etcetera and would dump the air out in the back of the engine bay, or maybe by the wheels.

Will this work? Do I need to radius the bottom lip of my inlet opening? Thoughts or ideas are welcome.

If my memory worked,I think Korff was recommending 1/6th 'height' at full width for the actual inlet.If so,you'd want to add a smidgeon more opening for the worst-case-scenario day.
As to a radius for the bottom lip,yes,I think it would prevent any vena-contracta funny-business as the air attempts to enter.
You're creating a 'bottom-breather' which GM has used on Corvettes and Trans Am Firebirds and they relied on a lip spoiler below the inlet to create a stagnation zone right there.If you can locate one of these,you'll notice a modest radius atop the chin spoiler/airdam.
Just watch your 16-degree approach clearance so as not to rip that puppy off on a driveway ramp.
The actual drag data for the Trans Am is above at the mods data thread.I think it shaved 0.011 off the Cd.You'd want to verify that number.

[aardvarcus]

Thank you for your advice, unfortunately when I switched to my smaller tires it dropped the car back down 3/4”, and it would be too tight to still fit a 2+” opening and a radiused lip in within the remaining area without impacting my approach angles and ground clearance.

I updated my drawing, with my new plan of having my radiator intake at the very bottom of the grill opening, probably about 2.5-3” tall and 25” wide, so I will be close to the 1/6 “ideal” ratio. I picked up a flexible silicone baking mat, to actually form the seal between the front end “duct” and the radiator. I am still planning on using coroplast to make the duct, but I may reuse my aluminum front belly pan piece for the bottom, since I already have it made. (It is nowhere near exhaust….)

[aerohead]

Looks like you're good to go.