brian6speed

iTrader: (5)

Decided to order the 13" by 21" panels. Think it looks better, fits hood better, and should function better. Will return the panels not used. Ordered new panels in semi-gloss black. Can always change color later.

Will just cover holes in hood with tape for my track day this week.

Should I have 2 panels touching like in the pics or leave small gap in middle between panels?

brian6speed

iTrader: (5)

Took car out on highway yesterday and had vibration over 65 mph. Adjusted the bump stops and drove home. No vibration after adjusting bump stops. Will still probably install hood pins.


Cut out the small damaged section from side of hood. Cleaned up the edges and went over edge with touch-up paint.



Have this sheet of aluminum mesh from Mcmaster.



Cut out a section with tin snips and painted it.



Used silicone sealant to attach it to underside of hood.





There are 3 options:

Option 1 : Leave as is.

Option 2 : Add a lip or one louver to front to keep air from being sucked into engine bay.

Option 3 : Use louver panels instead. Can always have mesh underneath louvers but not necessary.

Tough Decision. Opinions welcome.

mattcl-s

maybe before cutting one giant hole in the hood in the middle split the vent into two sort of like a supra(orange one from first fast n furious) style hood with the 4 vents that would looks pretty sick IMO

brian6speed

iTrader: (5)

Canceled my track day and autocross last week since my dog passed away.

No other events scheduled for this year.

Started working on hood again and can post some progress pics later.

skd2k1

iTrader: (1)

sorry to hear about your dog. they're family members.

brian6speed

iTrader: (5)

Thanks for the kind words, appreciate it.

brian6speed

iTrader: (5)

Aerocatch Hood Pins & Louver Panel Install

Overview:

Made the mistake of installing one hood pin at a time instead of marking both up at the same time. Because of this they are a few millimeters off from each other placement wise. Still will function perfectly, but something to bug me since I'm perfectionist.

Removed hood latch and noticed with hood pins latched down, there is some flex/movement in grill area. Drove at 80 mph on highway and seemed fine. Will test it more later.

Not sure if I will leave hood latch removed. Could also add 2 more hood pins near center of hood, just not sure with how much curve the panel has there.

Enough babbling, onto the pics.

Only installed one louver panel so far. I kind of like the one panel asymmetric look. Assuming most ppl will say install both panels.

Hood masked and marked for cutting.



Panel Cut Out









Decided to use 41 Stainless M4 Button Head Bolts, 82 washers, and 41 lock nuts to install the one louver panel.

Would recommend just using rivets provided. Bolts cost more, weigh more, and requires 2 ppl to install. I obviously like making things hard on myself.

Panel Installed







Hood Pin Cutting/Install









Finished Product

brian6speed

iTrader: (5)

Decided against using the smaller louver panels purchased for the side vents.

Ordered these APR CF Universal Narrow Hood Vents. They are rather pricey, but should look great. Found them online for 280 shipped which is still really expensive.

The vents are 4.5" x 20". That size should work nicely.

Universal Hood Vents Narrow (pair)

Made a quick template to test fit.

brian6speed

iTrader: (5)

Here is a good article on how to aero test your car.

AutoSpeed - Aero Testing - Part 1

http://www.autospeed.com/cms/article.html?&A=108674

http://www.autospeed.com/cms/article.html?&A=108675

http://www.autospeed.com/cms/article.html?&A=108676

http://www.autospeed.com/cms/article.html?&A=108677

You basically tape wool tuft strips to the car, drive at speed, and have someone photograph the car.

Then you can use the pictures to judge what needs to be done to improve aero based on where there is turbulent air.

This is best option outside of a wind tunnel which is not an option for me.

m_rgaan

I freaking love it.

yungone501

iTrader: (4)

Mind me asking what you used to cut the hood with and when you cut out the diamond shapes where the hood pin locks would mount, how did you round those corners out so perfectly? Very impressive work....and looks might I add. Loving it! I'm not sure why but I've never read your thread before and will have to take some time next weekend to do so because you have some very creative/interesting stuff in here. Keep up the good work.

brian6speed

iTrader: (5)

Thanks. My tools are rather basic. Would you believe me if I said everything was done with just a dremel?

Used dremel with metal cutting disc to cut out diamond shape.

Used the dremel sanding attachment to round out the corners(attachment is round which helps).

Went over edges with 80 grit sandpaper by hand to get it smoother.

Even used the dremel with drill bit and grinding bits to make bolt holes.

Not the best or fastest way to do it, but it gets the job done.

My trusty dremel has been used on almost every project so far.

rush

iTrader: (1)

Add another to complete it

Marcelechka

^ +1

With all of the deductions you've made since your last weight-in, what are you at now?

Also, any decision on going F/I?

brian6speed

iTrader: (5)

Might add other louver panel in the future, not sure yet. From a function standpoint it is most likely not needed and would just be for looks. I am past the point of doing mods just for looks really.

Want to do more aero research first.

Ordered some tufted wool to test my cars aero efficiency. Want to do that before going any further.

Might also try measuring pressure differentials under hood and over hood. You want extraction vents in low pressure area(top of hood). If put in high pressure area of hood they will more likely suck in air then extract it.

One annoyance already is when washing car, water drops down on my polished plenums and creates water spots. Will need to cover vent when washing or polish my plenums a lot.

Another louver panel might get water on battery, etc. Not sure it is worth hassle just for looks.

Weight Loss

My car should be somewhere around 2750-2780 lbs with 1/2 tank of gas. Gas weighs probably 30 lbs. Have not been weighing everything though.

Will be removing hood latch cable and driver seat wiring soon.

F/I

No plan on going F/I. I prefer naturally aspirated engines, plus my other car is turbo.

Keep in mind the more power the car makes, the harder it will be to drive and get everything out of the car. This is more true for autocross, but also applies to track. With a lot of power you can never go full throttle and will end up spinning tires and over - driving more. In autocross more power probably equals same or slower times.

This is even more true for fwd cars with limited traction. I could use some more power, but not really wanting to add weight to get it.

Eventually might do a 3.5 or 3.6 N/A engine build.

Want to install stand alone ecu before any other power mods.

brian6speed

iTrader: (5)

IACV is acting up again, so just going to replace it.

Taped other louver panel to hood to get a visual of fitment and looks. It would definitely be mean looking.

Front picture came out blurry so this will do.

mattcl-s

now that would look pretty awesome not that it didn't already it just looks more proper

brian6speed

iTrader: (5)

Yea 2 looks better, but might create more turbulent airflow over hood.

If anyone has some worn down hood struts or a used oem CL front grill to sell PM me. Want to try gutting out oem grill.

brian6speed

iTrader: (5)

First Aero Test

Tried first aero test today. Saw some string in my garage so cut it into strips and taped it to hood. Mounted GoPro to the roof to get some video.

Didn't want to speed, so only was going 65 mph. There was also heavy wind today around 20 mph. There were heavy cross winds and swirling air which probably affected the test some.

Pics after taping strings to hood.





Pic after pulling back into garage.



Here is the video.


First, the string used is not ideal and strands had bends in them from being in ball. Ordered tufted wool, just gotta wait for it to arrive.

From the video you can see the flow over the hood is ideal and laminar.

The flow over the louver panel is harder to read. No strings were sucked into hood which is a positive, just not sure if air is being extracted or how much. The flow over the louver does seem more turbulent. Could that just be the air under hood mixing with air above? Not sure. Any opinions welcome.

Will do more testing. Want to test the driver hood section where panel would be and compare to passenger panel. Also want to test windshield and cowl area. Will test with cowl removed, then install and test again.

brian6speed

iTrader: (5)

Not really sure what the strands over the panel not really moving much means, unless airflow is going around the panel?

Maybe it means air is exiting vent and going over strings?

Strings near rear of vent seem to have some turbulent air. Not sure if that would be there without vent or not. Could be from removed cowl/windshield. This will be easy to test.

Will need to get instrument to test pressure differentials above and under hood to really figure it out.

Love this aero stuff, very fun and mentally stimulating.

Another theory could be that the engine air is getting pulled out under the car instead of out bonnet. Maybe a front splitter would change this some.

brian6speed

iTrader: (5)

Thinking that removing windshield cowl is a bad idea. Sure heat from engine can escape there when the car is sitting still, but when in motion that should be a higher pressure area than under the hood. Air moves from high to low pressure, so that should mean that gap is actually sucking air into the engine bay, not extracting it. That will negatively affect flow through the radiator and possibly my hood vents. I see no point removing cowl, especially when you have hood vents.

Will do some real world testing today and this weekend to see how this theory holds up.

gnuts

iTrader: (1)

Could you put string on the bottom of the windshield to see if it gets sucked down towards the bay?

brian6speed

iTrader: (5)

Yea I plan on doing that later today or this weekend. Will post results. Will install cowl then retest. Need to get more string.

brian6speed

iTrader: (5)

The cowl removed is definitely sucking air into engine bay, even at 20 mph. I will prove that the Ultimate Cooling Mod is total bullshit. It would only work when car is not in motion.

Much more detailed post to come with pics and video.

skd2k1

iTrader: (1)

is it possible that this is because of the vented hood? you should post your evidence in the ucm thread as well.

brian6speed

iTrader: (5)

No it is not because of the vent. The pressure on top of the hood is known to increase further back you go. If you want to vent hood the front area of hood is best. If you want air to be sucked into engine bay the rear is better. That is why most Induction scoops should be placed at rear of hood. That is why your a/c system has its Induction vent there.

Will post in the UCM thread, but have more testing to do first.

brian6speed

iTrader: (5)

Here are the coefficient of drag numbers for the 01-03 Acura CL.


First the formulas:

CdA = Cd * Frontal Area

Frontal Area(inches) = (Height/12) * (Width/12) * 0.84


Now the numbers:

Cd = 0.32

CdA = 7.05

Acura CL OEM Specs:

Height 55.5 in

Width 70.6

Got the numbers from this site:

Vehicle Coefficient of Drag List - EcoModder

brian6speed

iTrader: (5)

Really liking this site. Lots of useful articles to read.

AutoSpeed - Technology, Efficiency, Performance


Here is one on front undertrays and hood vents. These articles have real world applications and are not just for racecars.

AutoSpeed - Undertrays, Spoilers & Bonnet Vents, Part 1

AutoSpeed - Undertrays, Spoiler & Bonnet Vents, Part 2

AutoSpeed - Undertrays, Spoiler & Bonnet Vents, Part 3


It basically says that you need a pressure differential to have flow. The pressure in front of radiator needs to be higher than behind it. You need to relieve pressure in engine bay to increase flow. Closer to ambient pressure in the engine bay the better.

Some air can flow out under the engine and reduce some of the pressure under the hood, but it will still be higher than ambient.

Hood vents should help release pressure and increase flow through radiator if placed correctly(an area where pressure is higher under hood than it is over the hood).

Can use a Magnehelic Gauge to measure pressure differences between 2 areas. I purchased one so can do these tests later. You basically just attach tubes to the sensors and tape the tubes where you want pressure readings. You can leave one port open in the cabin with windows down to represent ambient, then tape other end of tube to an area above or below the hood to get reading. You can also use 2 tubes to get pressure differential between 2 areas.

Magnehelic gauge can also be used to test airflow restriction through the intake and filter. I plan on building a box around my filter with a tube funneled towards fog opening later on.

Article also shows that building a custom front undertray that slopes down with a bigger opening at rear for air to escape and closed off sides helped relieve pressure under hood in front area, but pressure in rear under hood stayed same. There are multiple tweaks that can be made.

brian6speed

iTrader: (5)

Aero Testing Part 2

Purchased a ball of yarn from discount basket at local Michaels for $2.50. Want something that has strands that will fray easily. The strands fraying shows that the air is turbulent.

Yarn strands taped on.



Before getting to after pics & video, here are my conclusions so far:

Not only is the cowl removed sucking air into engine bay, it also seems to be creating a lot of turbulence.

All the cars tested in aero test link I posted earlier were said to have laminar(attached flow) from hood to windshield. Mine is turbulent. Can only assume cowl being removed is causing this.

Think cowl being removed is reducing flow through the radiator and affecting the vent, not the other way around.

It is more turbulent at middle of windshield/cowl area and less towards the sides. Maybe leaving the sides a little open for fender venting might or might not work. Another thing to test.

Next step is to add cowl back and test again.

Here you can see where the yarn strands seperarted and it is turbulent. I also circled a strand that was sucked into engine bay. I taped that strand facing down into cowl area. Taped some yarn to bottom of the windshield so if it was flowing upwards I could see it from drivers seat. When driving I never saw those strands.














Here is the video:

gnuts

iTrader: (1)

Interesting stuff! You can really see the suction into the bay in the middle of the hood.

m_rgaan

Very interesting stuff indeed. Would be interesting to see the how the second vent would do. Have you considered battery relocation to the trunk? It's actually quite easy despite what people might say. I highly recommend considering you don't even need a kit and it would better perfect front/rear weight ratio.

brian6speed

iTrader: (5)

Will get to vents in later posts.

Not gonna relocate battery. Trunk would not be a better option, and my car is fwd so weight distribution is pointless besides for cross-weights.

brian6speed

iTrader: (5)

Aero Testing Part 3

Reinstalled Cowl and tested again yesterday. Keep in mind it was really windy and that could have affected test some.

Forgot to plug the hole for wiper motor wiring to engine bay. Holes where wiper arms go and venting in cowl was open.

It seemed to help some, but not as much as I hoped. Some air is getting sucked under cowl area(intended to for a/c vent).

Cowl Installed Video Here:



Next step was to tape the venting and holes in the cowl. I also plugged the hole to the engine bay. Not as windy today.

This seemed to help a good amount. Not much air at all getting sucked in.



Cowl Taped Video Here:



Noticed turbulence behind the hood vent. Decided to tape some yarn to bottom of vent and video tape it.

Here is a picture of vent after driving. You can see some strands of yarn were pulled out of the engine bay. The front half of the vent is working, the rear half probably not so much.



In the video you can see the yarn hanging through the louvers if you look closely. There is some turbulence under the rear of the vent it seems.



Going to make a panel to bolt under the hood to block the rear section of the vent and test again.

If I do install other panel, will not cut the hole in the hood as far back and only really use front half of panel for venting.

brian6speed

iTrader: (5)

Rescheduled my missed track day for Oct. 14th.

APR Vents arrived today.

These are gonna look great. Will install them just behind hood pins. One vent weighs only 0.3 lbs so they will remove more weight also.

brian6speed

iTrader: (5)

Hood Latch Removal

Fairly simple to remove. Only annoying part is fishing cable through fender hole.

Weight is between 1.5 to 2 lbs. Didn't bother weighing cable. Left Latch on hood.

brian6speed

iTrader: (5)

Under-Car & Wheel Well Aero Brainstorming

Wheel Wells

Was thinking how having fender liners removed is detrimental to aero without other modifications.

Most sites I have read state that 15% of drag alone comes from front wheels/tires.

My aggressive wheel setup is a bad idea from aero perspective. The tires stick out far past bumper and without fender liners air going under car is also hitting front of tires.

Reinstalled parts of Fender Liners

Decided to grab the fender liners from storage. Wouldn't fit without modifying them, so cut them in half and removed part at top.



Front Piece



Rear Piece




This part helps deflect air away from tire and suspension parts. Could make custom ones later.



Can use bumper canards and defector plates that attach to rear of front bumper and front splitter. They would stick out past bumper blocking tire sticking out.

Noticed that at the top of the fenders there is a gap that goes to engine bay. Since wheel well builds up high pressure at the top and back, that air is most likely being sucked into engine bay.

Would blocking that gap with tape or fill with foam help aero? Would the side vents in the hood make it good to suck that air in and let it exit in a low pressure zone?

Gap Taped Below



Might consider fender vents.


Under-Car

Good article here.

AutoSpeed - Modifying Under-Car Airflow, Part 1

It lists a drag percentage breakdown for a Volvo. 35% of the drag is from under the car and wheels/tires.

Breaks down to:

Front Wheels 13.1%
Rear Wheels 6.9%
Floor 6.9%
Rear Axle 3.1%
Engine 3.1%
Front Suspension 1.4%
Exhaust 0.7%

Under-Car airflow can also affect radiator flow.

So for under-car aero start with front splitter. Will have it stick out 2-4" and go back roughly to axle line.

Custom suspension/tire deflectors.

Middle section of under body will be hard to improve with exhaust and bracing. Will make some panels to block off sections to smooth flow, but a full flat bottom is not really possible. This will be about lift and drag reduction mainly.

Finish off with a rear diffuser that draws air up, keeps flow straight and lessens the turbulent wake behind car.

brian6speed

iTrader: (5)

Fucked up my back big time. Can barely even move or get out of a chair. Should stop scheduling track events since something bad always happens to make me miss them.

Probably won't make track day or be able to work on car for awhile.

Went to sleep feeling fine, but woke up in pain unable to get out of bed and it isn't getting any better.

brian6speed

iTrader: (5)

Made it to track day today. Completed first session in intermediate group. I was faster than a 911 turbo. My car corners and brakes better. On the straights he can't really pull away from me.

Post later with video.

m_rgaan

It's good to hear you're feeling better already man!

Also, I was just researching this thread over again for the thousandth time and I was curious what spring rates you were running on your coilovers to maintain such meaty fitment. I was considering running 18 and 12 because I'm running 12 and 5 right now and it's just too little. I was originally running 24 and 18 and that was way to hefty for me.

brian6speed

iTrader: (5)

Thanks. Pain and muscle relaxer medicine helped just in time.

What setup are you running? 24 and 18? Holy hell. My 12 and 8 is so stiff can't imagine those springs even compressing. Would think 12 is fine for front. If not try 14. For rear you could try 8 or 10.

My coils have linear Swift springs, and rates are 12k front and 8k rear. Keep in mind that how much each corner of your car weighs makes a difference in what spring rates you want.

My car is so stiff that when riding on highway my knees bounce probably 6 inches like they are springs. Should get video of it, it is hilarious. In the track videos I post you might see times where it looks like I am bouncing in my seat.

To really get it right you need to know corner weight on all 4 corners. Then you can use some formulas to calculate frequencies. If you don't match front and rear right it will ride badly over bumps.

I got lucky. Purchased my coils used from a member on here. With my weight removal the rates seem to match up almost perfectly even though I haven't really tested other rates. If my car was stock weight they would not be stiff enough for my purpose.