There are two things that I have found that kills the TL's performance: Underhood ambient heat and weight. Although my emphasis has been on the weight aspect (Putting the TL on a diet (link)), I have never lost sight of the "underhood ambient heat" aspect. Up to this point, I have been satisfied with my heat management mods. My previous cooling mods were -

Removed plastic panels (top side, under side, under trans, fiber mat from backside of hood).
Removed weather stripping along the cowl.
Outlaw Engineering Thermoblock Spacer.
Custom CAI Insulation (link).
Throttle Body Coolant Bypass (link).

But after adding a performance J-pipe, I immediately noticed that the Texas heatwave (100 degree temps) was stealing much of the J-pipe's punch during the evening commute going home. So, it was time to up-the-ante on my heat management mods. The plan was to drastically increase the underhood airflow to sweep out the pent-up heated air from the engine compartment.

Our TL is *not* overheating because the coolant temps are too high . Our oem radiator and fans appear to be superb. The coolant temp is not the problem. On the contrary, the coolant should remain at oem spec'ed temps. The ECU needs to see these oem coolant temps to derive the correct trim mapping.

The problem is the underhood ambient temps. If you can keep the underhood temps down, power will stay up.

The conventional cooling mods, Outlaw Engineering Thermoblock Spacer and P2R TB spacer, are moot. That is, these conventional cooling mods prevent heat from migrating from the engine block, to the intake runners, and into the manifold. The premise here is that the heat source is the engine block. But, I propose that the real heat source is the high ambient temps under the hood (from those hot primary cats). Thus, the conventional cooling mods are ineffective because they are attacking the wrong problem.

Even with all of the plastic panels (prior to this mod) removed from my TL, the underhood temps were still too high for my liking. Why did my underhood temps stay high (although much cooler than the oem "oven") even with the panels removed ? Lack of an air exit. Remember, we need airflow. And, air will not flow if the air has no place to exit. The little airflow that is present flows from the radiator and exits from under the vehicle (the only available exit). There is *no* flow along the upper half of the engine compartment. And to compound the problem, hot air rises!

The hot air under the hood collects and stagnates along the upper half of the engine compartment. Why ? Because there is no outlet for the air to exit in that area, and nothing to promote meaningful air currents to flush away the pent-up (pooled) hot air. Hummm, sounds like the definition of "oven". It is no wonder that we have threads on our forum such as these -

Please HELP !!...Car sluggish or Flies (link)
109 octane unleaded = 5mpg increase... (link)
Engine Heat-Soaking issue (ink)


The Ultimate Cooling Mod is to remove the plastic cowl along the wiper blades. This leaves a huge 3-inch gap between the hood and firewall/windshield, along the width of the hood, for the heated air to escape. This is where an air exit is needed the most. Plus, even at a standstill with no ram airflow, the natural convection of hot air to rise will now work to our advantage.

The Ultimate Cooling Mod is not for everyone. It makes the car look ugly when standing next to the windshield, and butt-ugly when viewed from under the hood. But, boy does it ever work! It works like a miracle for keeping the underhood temps to nearly ambient weather temps. I am in Houston with a heatwave and my underhood temp is nearly ambient weather temps with this mod.




Pic below shows the plastic cowl that was removed.




Pic below shows the huge 3 inch gap.




Pic below shows the huge 3 inch gap.




Pic below shows how the car looks when standing next to the windshield.




Pic below shows how the car looks when viewed from under the hood.




Pic below shows how the car looks when viewed from under the hood.






Removing the cowl did the trick! My throttle response and power does not diminish even after commuting in rush-hour traffic in 100 degree weather.

Before the mod, I was able to hold my hand on the hood for less than 1/4 second and touch the intake manifold for 0.0 seconds. After the mod, I can *comfortable* hold my hand on both indefinitely.

After commuting for 75 minutes (completely heatsoaked) in rush-hour traffic in 100 degree weather, I can open the hood and *comfortably* hold the intake manifold indefinitely. Yes, this is the aluminum metal of the intake manifold, not the plastic engine panel. When I place my hand on the hood surface, I can't tell that the car was driven because the hood is the same temp as the trunk lid. All of this is if I feel it immediately as I pull into my driveway. After I turn off the engine and without the benefit of having the fresh ram airflow from the vehicle moving for several minutes, the hood still stays cool enough to hold indefinitely and the IM becomes UNcomfortable to hold after holding it a few seconds. This is a huge difference than before removing the cowling. And compared to oem... forget it, how do you compare night to day?

In closing, I have not and will not discuss high pressure/low pressure as it theoretically relates to airflow thru the engine compartment. To me, it is a fruitless discussion. I did place paper streamers under my wiper blades to see the airflow vector (direction and magnitude) and the airflow was coming out of (*not* entering) the cowl opening with a healthy volume. But foremost, my empirical data tells the tale. I was after lowing my underhood temps and I got my underhood temps down to nearly ambient weather temps. I don't care about the theoretical aspects. Here is a forum thread where the theoretical high pressure/low pressure is discussion until your eyes become crossed: Mazda RX8 Forum - Hood Ventilation Ideas (ink). In this RX8 thread, the OP got tired of this fruitless discussion of theoretical high pressure/low pressure and made the following comment, which I agree with.



---------------------------------------------------------------------
PLEASE NOTE THAT THE FOLLOWING BELOW IS *NOT* A KEY COMPONENT OF THE ULTIMATE COOLING MOD.
It was with the oem grill that I had the outstanding cooling results described above.
---------------------------------------------------------------------

My saying is "anything worth doing is worth overdoing!" The following mods to the grill were made just to "Gild the lily".


Introducing................................... "The Shark Mouth"




This Shark Mouth is *not* a key component of the Ultimate Cooling Mod. I had done the Ultimate Cooling Mod before doing the Shark Mouth. It was with the oem grill that I had the outstanding cooling results.

No mesh or screen was installed. Mesh will allow less than 60% (maybe less than 50%) of the air to flow thru it. I am wanting all of the airflow that I can get to reduce my under hood temperature.

Without a mesh, I am taking a change with foreign objects hitting the AC condenser. It happens, but it is a rare occurrence. A person loses either way (pick your poison).


Pic below shows the oem open grill of the Nissan Titan





Many cars/trucks come oem with very open grills. One example is the Nissan Titan (see pic above). I searched the Nissan Titan Forum (www.titantalk.com) and was unable to find a single instance of a damaged ac condenser, nor any issues at all with the wide-open lower grill. Also, I checked a few motorcycle forums discussing their exposed radiators. The motorcycles do experience a few problems because their front tires will kick-up road debris and their radiator is directly in-line with the front tire.

Several items were removed to further expose some surface area.


Pic below shows oem items that where removed.





The lower front air ducts (ie, faux air ducts) were made fully functional by removing the obstructions. You say "air diverter", I say "obstruction" . There is sufficient nooks-and-crannies for the air to flow from these side ducts to enter the engine compartment and to flow out from the open hood cowl.



Pic below shows obstruction that was removed.




Pic below shows obstruction that was removed.











Stay cool

 

Wow. You truly are a pioneer. I don't know if I will ever have the balls to do this but this is an amazing find. The interesting thing is everyone here dynos when the car is cool and with a large fan blowing in front. What no one ever does is dyno on a hot day after the engine has already been running to see how much power is really lost on your average day. I know how bad heat soak kills power, but I wonder if instead of removing it completely if you could just cut some of the plastic out to increase some of the air flow. Either way, great writeup!!

 

wow

 

nicely done.... im afraid id have to create some heating means for the winter, as it gets pretty cold up here in NYC, so my motor doesnt freeze while driving on the highway. lol

all jokes aside though... i dont have the least amount of dissagreements.. one question...as many others might bring up...how well is the windshield sealed under that plastic...the plastic overlaps the windshield, so u cant tell without removing it...and also... will the water be affecting anything when it rains, since the plastic acted somewhat like a gutter for the water....again, mostly questions that might arise from other members.

 

for a second I thought it was a good idea to expose the CAI filter, but that means u have to clean it more often due to dirt and bugs smashing into it..

good idea tho..but might do it a little diffrently

edit:::that looks like a oem coolant cap..have u looked into a aftermarket one? should help with ur cooling

 

i was also thinking the same... as usually that cowl collects and directs water away, where does the water go now???

 

My dyno runs were done on an almost 90 degree day with 50% humidity, because I wanted to go for a worst case senario with my pulls. Really great ideas though. I like the insulation on the CAI. I did that with mine as well. Made a big difference in the perforence of the car after it got to operating temp. Great post, and ideas.

 

No matter what fancy steps you take reduce heat soak and loss of power in hot summer temps, the TRUE underlying reason why power diminishes in the warmer temps is a thing called density altitude or DA. In a nutshell, hot air is less dense than cold air. The more humid the air, the less available O2. The lower the barometric pressure, the less o2 that naturally gets pushed into the motor. On a humid (50%) 90 degree day in Kansas City (1100' above sea level) with 29.9 baro pressure (typical), the density altitude conditions are in the 4000' range or essentially sucking out about 10% of the available power compared to "standard conditions" at sea level. On a dry (30% humidity) and cold (40 degree) day, the DA is right around sea conditions (ie negating the true elevation of Kansas City).

DA is out of your control. You can wrap your intake pipes, add silly plastic spacers to your intake manifolds, ice the intake manifold, but the reality is the motor is going to heat soak in stop and go traffic. You can't stop heat soak in warm weather. You can slow down the heat soak process by a few minutes, but that's the best you're going to get. If you're on the highway, heat soak won't be as much as issue because a lot of air is moving through the engine bay. Hook up an OBDII datalogger and read the air intake sensor values. You'll see what I'm talking about. Also, hot compression chambers (ie block/heads) with a cold air charge create the most power and are the most efficent. Not a cool engine with hot summer air.

Yanking and cutting all these parts off the car really hasn't improved the motors ability to shed heat and has most likely increased drag. Those lower bumper ducts are designed to funnel air to the raditator, tranny cooler, and AC cooler. Apparently you didn't know that. Now you've made a setup that makes the incoming air turbulent and not directed towards probably the most critcal components of a car. I'd strongly reconsider this modification.

These fenderwell CAIs are silly as well. Do you guys not realize that ambient temps at near street surfaces approach 130+ degrees on 90+ degree days? Expose the filter like Inaccurate did and now you open up the potential for all sort of debris to pummel and lodge itself in the filter media. The OEM intakes on your cars, while quiet, are very efficent and become pressurized at speed due to the location and the way the ducting is shaped. More importantly, the air brought in is ambient and not as influenced by street temps. I have yet to see anyone post a 3rd party dyno of a CAI either. From what I can tell, everyone is apparently buying these things based on what the aftermarket companies say and the incorrect notion that the OEM intake is restrictive because it's "ugly". It's so far from the truth.

I'm all for Shade Tree mods, but sometimes you need to step back and research and understand why highly paid engineers do the things they do.

 

Innacurate all I am going to say is "wow".

When I get my turbo you and I need to head to the track

 

TheChamp531,

We need to run before you get the turbo. My car ain't THAT light! When you get the turbo, you will be the champ for sure.

 

i doubt i have the balls to take such a drastic step....my hat goes off to you

 

Filters I can easily purchase. Beating a base auto C5 corvette is priceless !

 

... speechless....

i can only IMAGINE the difference in response /feel with that much breathing power under the hood...

i could never do that with DD in NY weather.... rain, wind, leaves, snow in the winter, corrosion from the elements etc...

 

Haha want to help me install it?

Anyways what part of Houston are you at? I'm in Katy and I rarely see any TLs from Acurazine (or modded besides spoiler) in Houston and I'm always going to N,W,SW,S Houston.

 

The pep, response, and pull is identical from leaving home in the mornings (75 degrees at 5:30 AM) to getting home at 6:00 PM after commuting in rush hour traffic for 75 minutes in 100 degree weather. My MID was reading 102 yesterday and my MID is fairly accurate.

 

It sure does look ugly under there but it makes sense.

What next? cut some holes in the hood and install some functional hood scoops

 

Haha. That is the nice thing about being an "old guy". I have no freinds to impress. The mod is not really noticable unless you walk next to the car, standing next to the windshield. Function over form. With this mod, I am happy to show other drivers my taillights. That is the impression that I enjoy making.

Ok, now you are giving me some ideas...

 

you have no worries of someone popping your hood and stealing engine parts? possibly disabling the battery and stealing the car?

 

^^^ROFL... I knew I should have kept my thoughts to myself...

Old Guy... I don't think so. Just a guy using his mind. Its better then sitting at home watching TV and not doing anything. Oh shit, thats what I am doing. I suck!!!

 

Not bad. I actually don't think it looks that bad, either. It's how cars used to look (cowlless). The grille looks ok, too. I do think it would look better with mesh, but I know your reasoning. And let's be honest, losing the cowl, grille, and deflectors shaved a little more weight ...yeah, you know you love it.

Why the sarcasm? It's been done. I forget the guys name, but he's in and has a SC'd TL...made a custom hood with functional vents.

 

Haven't had a chance to look at the car since I read this thread, but is it not feasible for others to actually cut the plastic piece to get the airflow, while not completely eliminating the cowl? This way you can create an airflow up and out the middle of the cowl area. I am going to look at it tonight and see what else could be done. I like this concept as it will force a LOT more air through the engine bay. Ideas, ideas!!

 

I agree that we need to investigate if this mod can be done without totally removing the entire plastic cowl. I think something could be done. Either some major cut-outs or some "cool" (pun intended) looking holes aligned in a row along the cowl.

I will look at the pieces over the weekend to see what might be possible. It would be nice if we could make this mod more palatable/acceptable. The TL Performance gang really needs this mod.

 

I figured it would only be a matter of time before this was done. By the way I like the look of the front without the grill, its a great aesthetic mod.

 

There is a huge gutter under the plastic cowl. Also notice the heavy bead of RTV sealant used along the bottom edge of the windshield. I have an arrow pointing to a huge blob that oozed-out. The dashed red line illustrates the flow of water thru the gutter.




There are several of these oozed-out blobs along the bottom edge of the windshield to clearly say that the windshield is very much sealed tight along the bottom edge.




The oem cowl does allow water to freely enter this area.




This gutter area is DESIGNED to handle free-flowing water. There are drainage holes on each side (driver and passenger). I do need to test what happens if these holes are plugged - Are these holes the only drainage route? If so, I must make sure they never become blocked.




I poured water into the gutter to see where the water drained out. It drains out in the fender wheel behind each front wheel. Remember, your oem car does this too ! All of this stuff is "as designed" by Acura. Your oem car allows water to enter this gutter, and your car drains water like this too.

DRIVER SIDE




PASSENGER SIDE






Here are some disadvantages -

Lose the windshield washer because the spray nozzles are incorporated into the plastic cowling. The washer will remain functional if we find a way to hack the cowl versus removing the cowl entirely.

Lose the fresh air intake for the climate control. I never use this feature. I always have my system on the recirculation. This feature would still be lost with a hacked cowl because there would be hot air from the engine compartment passing over the fresh air intake.

If you parked your car outside, leaves would become a huge problem. My car is always covered, even at work. Hopefully we can devise a hacked cowl to eliminate this problem.

 

Honestly, the only problem I saw was the washers. I'm sure you could fab something up to hold them in place.

 

The washer will remain functional if we find a way to hack the cowl versus removing the cowl entirely.

 

^True. Looking at the pic of the cowl, it doesn't look too complicated. Since I rarely use my washers, removal would be much easier (and as I said, I don't mind the look).

 

I forgot to add - Since having the cowl removed, I have driven thru one instance of moderate rain and have washed the car once. I encounter no problems.

For the car wash, I used a conventional water hose with conventional water nozzle, set to the "Shower" discharge pattern. There was no water found in the engine compartment or firewall immediately after the car wash.

 

Hood spacers would have worked but not a lot of people like that look.

 

x2

 

Here is the page from the Service Manual showing how to remove the cowl. Just in case someone wants to experiment this weekend.

 

ur hardcore...

BUT... you forgot one thing.. you didnt weigh all the plastic

ps. How much weight would you save if you deleted the winshield washerbottle and lines???

 

Haha, you know me much better than that! I promptly weight the items. It will be presented in an upcoming update of the TL Diet thread.

 

I did not want to discuss the following because it is just a wildass guess on my part. I was planning to keep it to myself. However, I feel compiled to share it with you to combat a valid argument being presented.

The argument is being presented that this mod is ineffective because the mod hopes to combat the low density of the hot air. All of us that hang out in the Performance sub-forum of Acurazine are fully aware that hot is less dense. This is why we have CAI’s.

BTW, the temp at ground level is not 130 degrees. My MID temp sensor is at the exact same level and almost same position as my CAI filter, and the MID is just a few degrees warmer than the weather report for my city. Before leaving work yesterday, the internet said that the temp in my part of Houston was 99 degrees, and out on the road my MID (same as CAI filter location) said 102. And, my MID is fairly accurate. I check it often against the reported temps for my area.

I know that my engine is ingesting the coolest air possible. I did not develop this cooling mod for this reason.

There is way too much empirical data that supports the notion that if our underhood temp rises, our power declines. And, I know it is not because of low density air being ingested. There is something else at play here.

It is in my opinion, that this mod works because it keeps certain sensors cool. It is my theory (based on nothing but a hunch) that if the IAT (intake air temp) and transmission temp sensor reaches certain threshold temps, the ECU will curtail the power output. I think this would be primary via lower ignition timing.

Well, why not just relocate the IAT to the AEM “off road” position, where the IAT will be cooler? Because I tried that about two years ago. Complete failure. It screwed-up the ECU trim mapping causing the trim to be rich.

Again, I know from empirical data that if the underhood temp is kept low, the power will stay high. Therefore, I concentrated my efforts on this goal. And, it worked “in spades”.

In closing, I will paraphrase a quote found elsewhere in this thread:

 

washer bottle with attached motor, tubes, and mounting bolts = 1 Lb 9 oz (or, 1.6 Lbs.)

BTW, bottle was weighed dry, *no* water.

 

Pardom my acroynm ignorance, but what is a MID temp sensor. I don't exactly what this thing does, but I can assure that a concrete or asphalt surface on a hot day is excessive and far greater over true ambient temps. Don't believe me, here's a study of surface temps on concrete and asphalt. As you can see the temps can approach 170 at the surface. At 1 foot, you're still looking at 40 to 50 degrees over ambient. Is this really where you want to be pulling air from? http://www.pavements4life.com/QDs/En...HeatIsland.asp

These CAIs, like for any car, are rather funny. The claim is they pull in colder air temps, yet the filters are located in stagnent air areas in the bumper where air temps are greatly exceeding ambient because radient heat from the radiator and engine bay encompasses the area of the CAI. Then there's the fact that most CAIs use metal intake pipes which heat soak badly. Many times the IAT is mounted in this hot pipe too. The OEM intake pulls in air from outside the engine bay therefore it truely is a CAI. Has anyone actually put the OEM intake on the flow bench to see if it's actually a restriction.

As for these reduced underhood temps, do you have any actual data to support your claims? I'm talking about:

1) Datalogging IAT values for reduced intake temps
2) Datalogging timing, A/F ratios, and MAP/MAF voltage (ie higher MAF/MAP voltage means more power)
3) Recorded underhood temps at a stop, 35mph, and highway

With all modifying you do and the claims you make (ie beating low to mid 13-second C5s), I would think you'd have a simply $150 ODBII datalogger to verify what you're doing actually is working.

BTW, the purpose of that cowl piece is to:

1) Keep out debris, rain, and rodents
2) Help channel HVAC air
3) Improve aerodynamics

There is a high pressure area that occurs in the vicinity of the hood and windshield convergence. That's why it's an ideal place to pull air for the HVAC. I have a very hard time believing the much underhood air is actually being pushed out from this area because the pressure zone is so strong. Ever seen the true ram air systems on classic muscle cars? There's a reason why they're rear facing and at the back of the hood.

I'm really not trying to be a d!ck, but it sure seems to me from my readings, that you're going off hunches for these mods instead of applied science.

 

I can see what you are trying to say with the asphalt temps. It can be an issue in stop and go traffic, but when your moving constantly it should be fine. And I agree with most of your statements. I am wondering what the aerodynamics would provide with the removal of the lower grill. It seems to me it directs air directly into the condensor when I was underneath last time. I am thinking about converting that to ducting so it will help out with other things.

 

Mhmm a debate between dave and innacurate.

 

I think it's a question between the temp levels at the asphalt, or a few inches above (where the CAI is mounted) vs. underhood temps, where a typical SRI is mounted. Surely, air from outside the car would be cooler than air in the engine bay.

 

Dave, my experiences mirror yours with one exception. I've done this mod on my other car and I was well aware that the lower portion of the windshild is or can be a high pressure area. I log IATs. My filter is under the hood, no CAI with the sensor in the filter. I saw a drop in temps during around town driving. The only thing I can think of is the high pressure area doesn't become apparent until freeway speeds. During city driving it gives the air coming off the radiator a place to go.

Granted this was on a different car with much different aerodynamics than a TL but I think the principal applies.

I was worried about high speed stability and aerodynamics. The car traps in the mid to high 120s in the 1/4 and I didn't want to upset anything. I actually took it to 174mph after the mod and some of the noticable bowing in the hood at that speed seemed to be reduced. I don't pretend to know the mechanism in which this worked. That's why I don't recommend it to anyone else until I understand it.