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3point8 Performance
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Discussion Starter #1
So I've been playing with Torque doing some data logging to see what kind of info I could find out about my 3.8. One of the things I started with was the IAT (intake air temperature) vs AT (ambient temperature outside). Why is this important? Well, the hotter your IAT, the less power you can make. Plain and simple. When it comes to N/A setups, timing is how you get power and the warmer the IAT's, the less timing you can run.

Some might say, "You're talking about minimal differences in power" and you may or may not be right. I'm not here to talk about power gains from colder air, but which setup provides the coolest average intake temperatures which will reduces power loss due to high IAT's when driving hard. It's not always about making maximum power, but preventing loss of the power you have.

Please note that this thread is specifically for 3.8 motors. When it comes to TC or SC applications, the IAT's are not as significant due to the use of an intercooler.

Basically what I did was test various intake setups to see how they performed and how they managed the difference between IAT and AT. Here are somethings I want to cover

1. You're wasting money on your CAI/SRI
2. Heat soak
3. Dyno results are worthless
4. Get the SRI noise for free
5. Stock air box
6. Stock air box with shroud delete
7. Stock air box with shroud delete and vent plugged
8. SRI no shield
9. SRI with shield
10. CAI in fender
11. Conclusion


My testing conditions: I did all of these tests with very similar conditions. Early morning cold temps 50-55* side street driving, then 50 miles fwy driving with temps getting up to 75*. Then another 50 miles FWY in 80-85* temps in medium traffic. Oil temps between 195 - 220 and coolant temps between 185 - 210.

Tooling and instrumentation: What I used to monitor the temperatures was Torque Pro. Why? First because it's what is available to me. Second, it's simply reading data from the car's sensors which the car uses anyway, so it's going to be as accurate as you can get. During testing of the various setups, I had the IAT sensor in roughly the same spot as the stock airbox.

1. You're wasting money on your CAI/SRI
A lot of you are spending upwards of $350 for "CAI" for your 3.8. $350 is a lot of money. The promise of HP gains is tempting though. Everyone says the intake adds power and the car is better overall, but here is what is really happening - the design of the intake is indeed better for flow than the stock air box. It provides better throttle response and adds noise. This gives the impression of performance. It's true, the CAI/SRI setups do make the car feel snappier, but that's only temporary. What do I mean? Every thing is fine until heat soak.

2. What is heat soak?
When you're driving, your coolant temperatures and your oil temperatures will rise. It just happens. Add the sun and the heat coming from the road. This causes the temperatures under the hood to rise. The intake components are saturated with this heat. This is especially significant when the car is stopped at a light or in stop and go traffic when the air isn't moving a lot. Heat soaks into everything. The metal parts of your intake will absorb the heat too. This means that as air passes through the intake ducting, it will take some of that heat with it causing the intake air temperatures to rise.

Back to the CAI/SRI, your heat shield is only delaying the inevitable and does not keep the heat out. So at some point, you're just sucking in hot air. Bad for performance.

"But I had gains on the dyno" you say. Keep reading...

3. Dyno results are worthless
The problem with dynos is that they are not mimicking real world conditions. On a dyno, the hood is up so the heat from the engine bay can escape freely. Not only that, there is a fan blowing high speed air across the front of the car which is only helping the heat to escape and also to prevent heat from reaching the intake filter. So, gains on the dyno mean nothing unless you have that hood closed.

4. Get the SRI noise for free
Some of you (including me) like and want the noise an SRI provides. Well good news, you can get that noise for free. In the bottom half of the stock air box, there are a bunch of vertical fins. Delete these fins and enjoy. You can also get added noise by porting your TB and your intake manifolds (which will yield more benefits other than sound).

5. Stock air box
Ok, so on to the stock air box. In reality, this thing is pretty damn good. Please note that I dynoed 321hp/290tq with stock airbox. There are a few issues with the setup though, first off, there is a shroud that sits in front of the intake snorkel (the intake mouth you see on top of the radiator when you open the hood). For all the potential volume of the stock air box, this shroud cuts that down. Not only that, it helps let heat in. Why? Well, in the side of the lower half of the air box (under the filter), there is a square hole in the side of the box facing the wheel well. Why this is there can only be assumed at this point. I believe it's there for emissions and to increase MPGs, but that is only my guess. It may also be there to help low end throttle response.

When sucking air, of course it'll be easier to get it from that hole since there is no restriction in front of it. This hole leads right into the engine bay. This means that IATs will rise significantly as under the hood temps rise. Even when driving on the fwy, this things is sucking hot air through that hole.

Results: Best I could get was a 25* difference between AT and IAT at highway speeds in a head wind with an average of 30* difference on the fwy. In low speed/stop and go traffic, it would heat soak and I'd see upwards of a 60* difference. Wow. Recovery took quite a while. Recovery is how long it takes to get back to the average difference.

6. Stock air box with shroud delete
I removed the shroud and I saw a noticeable difference, though not a significant one. Best I could do was 18* in a head wind and average was 25* difference on the fwy. Heat soak had the same issue, upwards of 60* difference. Recovery was slightly better, but still slow. This is a mod meant for moving air only.

7. Stock air box with shroud delete and vent plugged
I plugged the hole in the side of the air box. This made a nice difference. Best was a 8* difference in a head wind and averaged about 12* difference on the fwy. With heat soak, I saw 40* difference. Recovery was no better. After a heat soak 84* AT and 220* Oil Temps, I was only able to get the IATs back to 25* difference after 10 miles of FWY driving.

Please note that it felt like throttle response took a hit down low, but it seems to be ok up high.

8. SRI no shield
Pure heat. IATs got up to 160* and recovery was almost non existent unless you were doing 80mph+.

9. SRI with shield
Best you can hope for is to match the stock air box with no modifications. The SRI I tried (I will not state the name) gave 35* difference at high speed with low oil temp. Recovery was slow. Average difference was 40*.

10. CAI in fender
This setup I built myself. I removed the washer fluid reservoir and stuck a cone filter in the fender area. I added foam to insulate the filter from the engine bay. There was a big gap left after removing the reservoir.

This by far has been the best setup. Average difference is 5* with 2* not being uncommon. Highest temps were 25* difference. Recovery is almost immediate (will depend on how long it was heat soaking, how hot the engine bay is, etc). As soon as you start moving the temps start to drop.

11. Conclusion
In conclusion, the available "CAI" options for the 3.8 BK2 are really just SRI's and what is an SRI? A hot air intake. Dyno gains might be seen with them, but once you close the hood, you're losing power.

Since there are no available options for BK2, you can either find one for a BK1 and make it work (probably works just fine), but these are still listed at $350 which is steep IMO. You can build your own, just don't use cheap plastic autozone parts. Or, just stick to the stock air box.

The best you can hope for is to match ambient temps outside. You can't get any colder without chemicals.

I do plan on trying other setups, one is to plug the hole on the side of the stock air box and then cut a new hole in the front and run ducting down into the fender. I think I'll see higher temps than the CAI I made, but it will still be better than all the other options. Another setup to keep the hole on the side of the box and try to foam off the box so that the hole will get air from the fender and not the engine bay.
 

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I'm broke lol
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Awesome write up! Could you post pics of the CAI? And is there a solution that would allow you to still have washer fluid? I would love to do this but I live in Canada and washer fluid is a must have
 

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"In the bottom half of the stock air box, there are a bunch of vertical fins. Delete these fins and enjoy."

Are you talking about the inside of the box underneath where the filter would sit? or underneath the box on the outside?

Great write up btw :D im still trying to figure out better ways to keep the heat out of the engine bay while running a cold air setup
 

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Nice! you went all mad scientist on this project haha, but nice work and good info....

So in your opinion,
let's just say I have 2 identical cars, one with an R2C SRI and the other with the OEM intake.... In exact operating and outside temps, bringing in exact equal IAT's to the motor.... Is there a benefit to having more AIR FLOW (R2C) vs. LESS AIR FLOW (OEM)? whether or not the air is hot air (of equal temps)....

You see, I am now trying to justify my purchase of the R2C, thanks alot you nerd! LOLZ seriously though, this is good information to chew on ;)
 

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Reader of many threads
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Great write up - I would love to see a comparative analysis against SRI/CAI/Stock Air Box with a Phenolic Spacer, just to see how much (if any) heat is isolated away from the intake & throttle body, or if those are a waste of money too :)
 

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3point8 Performance
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Discussion Starter #6
Awesome write up! Could you post pics of the CAI? And is there a solution that would allow you to still have washer fluid? I would love to do this but I live in Canada and washer fluid is a must have
Here you go. Before I added the IAT sensor hole and the vent tube.



"In the bottom half of the stock air box, there are a bunch of vertical fins. Delete these fins and enjoy."

Are you talking about the inside of the box underneath where the filter would sit? or underneath the box on the outside?

Great write up btw :D im still trying to figure out better ways to keep the heat out of the engine bay while running a cold air setup
Inside of the box there are fins. Open the box, remove filter and look inside, you'll see them. There are like 5 on each side of the box.

Nice! you went all mad scientist on this project haha, but nice work and good info....

So in your opinion,
let's just say I have 2 identical cars, one with an R2C SRI and the other with the OEM intake.... In exact operating and outside temps, bringing in exact equal IAT's to the motor.... Is there a benefit to having more AIR FLOW (R2C) vs. LESS AIR FLOW (OEM)? whether or not the air is hot air (of equal temps)....

You see, I am now trying to justify my purchase of the R2C, thanks alot you nerd! LOLZ seriously though, this is good information to chew on ;)

Well, I honestly don't know. The thing is, does the R2C flow better than the stock air box? Doubtful if you have the side hole open and the shroud removed (free mod). I think you only get better throttle response due to a shorter tube and less twists and turns it needs to take, but I'm going to bet the power levels will be within ~2hp of each other on the dyno which is insignificant. But I have no proof or data to back this up other than what I did on the dyno with stock airbox. However, that was with the hood open. Close the hood and you have to get air through the shroud (if it's there) and then the narrow space between the hood and the shroud. With the hood closed, and air temps being equal, I might assume the R2C would be better, but in reality it wouldn't be for long due to heat.
 

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3point8 Performance
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Discussion Starter #8
Great write up - I would love to see a comparative analysis against SRI/CAI/Stock Air Box with a Phenolic Spacer, just to see how much (if any) heat is isolated away from the intake & throttle body, or if those are a waste of money too :)
I have a phenolic spacer on the manifold and a coolant bypass on the TB, but the IAT's are measured before the TB, so it would not show on the data log. But, passing air through hot devices will increase the air temps. The phenolic spacer and the bypass keep thing frosty.

The IAT is so slow to react it is only good for averages.
True, which is why I tested on the FWY for long distances and why I took averages :)
 

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Here you go. Before I added the IAT sensor hole and the vent tube.





Inside of the box there are fins. Open the box, remove filter and look inside, you'll see them. There are like 5 on each side of the box.




Well, I honestly don't know. The thing is, does the R2C flow better than the stock air box? Doubtful if you have the side hole open and the shroud removed (free mod). I think you only get better throttle response due to a shorter tube and less twists and turns it needs to take, but I'm going to bet the power levels will be within ~2hp of each other on the dyno which is insignificant. But I have no proof or data to back this up other than what I did on the dyno with stock airbox. However, that was with the hood open. Close the hood and you have to get air through the shroud (if it's there) and then the narrow space between the hood and the shroud. With the hood closed, and air temps being equal, I might assume the R2C would be better, but in reality it wouldn't be for long due to heat.
Oh great, so now I have a 6 pound paperweight connected to my motor.... FML:crying:
 

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There a bunch of fins that produce pretty much a checkered pattern. So meaning, use like a dremel and cut through everyone one of those fins? Wouldn't that let more heal into the box though ? Just wanna clarify before I start cutting into this thing
 

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3point8 Performance
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Discussion Starter #12
Oh great, so now I have a 6 pound paperweight connected to my motor.... FML:crying:
If you already have it, I would delete the washer fluid reservoir to allow cooler air from the fender area and try to seal off the heat shield as much as you can.

Vacmurse gave me a good lead on a different reservoir, so I'm looking into it right now.
 

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Heat*
 

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If you have a picture of the fins that were deleted that would help alot
 

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3point8 Performance
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Discussion Starter #15
Going down the freeway is not much of a concern. It would be the short WOT runs where 'cold' air would make the difference.
The highest temps listed were in stop and go traffic (both fwy and side streets) with heat soak, so that would be ~worst case scenario if you wanted to do stop light to stop light runs. At speed, the temps will average what was listed so it's good to go. But the important part regardless is how the recovery is and what the temps get to both before and after the run. You'll want something that has both lower average temps and fast recovery since after the run the temps will shoot up.

Most of my WOT runs are on the FWY anyway :)

There a bunch of fins that produce pretty much a checkered pattern. So meaning, use like a dremel and cut through everyone one of those fins? Wouldn't that let more heal into the box though ? Just wanna clarify before I start cutting into this thing
Not the checker pattern, the fins protrude from the sides an inch or two. I used a dremel and a tiny hack saw and a razor blade. Be careful not to cut yourself. If you want to take a pic I can circle the fins. I'm not home to take a pic for you. If you don't have a K&N drop in filter (or equivalent) I'm not sure how much noise you'll get from this mod.
 

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eh i think im just gonna leave it alone lol, happy with the stock intake box with k&n drop in anyway.
 

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3point8 Performance
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Discussion Starter #17
eh i think im just gonna leave it alone lol, happy with the stock intake box with k&n drop in anyway.
I'll take a pic when I get home, but if you're happy, that's all that matters.
 

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Great write-up with some good info. Wish I had seen this b4 I installed my SRI, but it's never too late to remove the washer fluid res and go with your setup. Any concerns of hydro-lock with your intake pointed toward the wheel-well?
 

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2013 3.8 Track
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Nice writeup. I wonder what the results would be when combined with an oil cooler and hood vents. Hopefully the combo is helping. :)
 

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3point8 Performance
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Discussion Starter #20
Great write-up with some good info. Wish I had seen this b4 I installed my SRI, but it's never too late to remove the washer fluid res and go with your setup. Any concerns of hydro-lock with your intake pointed toward the wheel-well?
I am, but only a little. Been running my SRT4 with a CAI sitting about 3 inches from the ground for years with no issues, even driving in rain. BUT, since I don't like not having easy access to the air filter, I am going to modify the stock box to add a feed tube to the front and go back to the stock air box. This way I will have fresh air from the fender and if for some reason I hit enough water, i'll still be sucking in air from the normal vent.

Nice writeup. I wonder what the results would be when combined with an oil cooler and hood vents. Hopefully the combo is helping. :)
Hood vents would go a loooong way to improving the heat soak. I'm not overly concerned about water in the engine, so I might look into that and do some more logging. An oil cooler would help as well. The car seems to like the oil more on the hot side...at least mine does. My first dyno run stock I noticed as the car got hotter, I got more power. So who knows.
 
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