Engine/Transmission (1998.5 - 2002) Cold Air Intakes

[NoSeeUm]

I went with the BHAF mode and did some experimenting with it. I posted what I found out here. My focus is to get back a good cold air intake system with out sacrificing air flow.



The same thread lead me to rethinking this whole thing. Primarily it was Boondocker's (Niel) comments and I am just now getting around to reworking my set up. One of the things that has stuck with me was his comment that he replaced his BHAF with his stock air box. Commenting that the stock air box was good to about 350-400 Hp.



I am considering replacing my stock air box with some modifications. It sure has been nice working on the truck with how easy the BHAF comes out. I am also looking at some aftermarket cold air intakes. Primarily the non oiled types like the Bruteforce by AEM, but the system seems noisy and will be in the way as much as the stock air box(without modifications).



There are several "better BHAF" threads around I have looked at most of them. Nothing that I have found really focuses on cold air intake, just better filtration with less restriction.



In the end, I guess I am asking for suggestions on cold air intakes and wondering at what boost / RPM the stock air box becomes a noticeable restriction. I anticipate I will run at a maximum of 40 psi boost at around 2700 RPM, but currently my typical maximum is 35 psi boost at 2500 RPM. Most of the time, no where near any of that.



Thanks;

Jim

 

[Joe Mc]

Jim - Great post! Guys, make sure to click on the "here" in Jim's post and follow it through - there's a ton of data Jim listed with temps and speed + loads + OAT (outside ambient temps). Good stuff Jim - Thanks,

 

[Extreme1]

I've never measured air temp at the intake but I do have a Fleetguard filter installed in a Mallory Mount and a stainless turbo heat shield from Larry B. When towing our enclosed snowmobile trailer in the winter, I've pulled into the driveway, shut the truck off and unloaded a few things. When I got back into the truck to start it, the "Wait to Start" light would come on with air temps around 30F. I know that this is no precise measurement of intake air temp but it does imply that the air being drawn in is substantially cooler than the 55F that my heater triggers at.



That being said, I'm also on a quest for cooler air. I got one of these:



www.e-bodyparts.com/miva/merchant.m...&Category_Code=72-Dodge-Truck&Product_Count=0



I was disappointed with the fit along the fenders but other than that my bodyshop got it looking good. I'm in the process of finishing up a panel to close off the bottom (I did cut out the scoops) and I made a duct to dump inducted air onto my BHAF. I will have to trim my Mallory Mount down to allow the air to pass to the filter. This will also work with my PDR Street Twins when I get them on.



I also recently did a little testing with my BHAF. I had the original on for about 3 years (with an Outerwears) and I put the stock filter minder into the end of it. I went out and promptly pulled it down into the replace zone. I installed the stock air box with an Amsoil filter (I don't like cleaning oiled filters) that I brushed the big chunks off of (it needs cleaning) and it only moved a small amount. I drove that around for a few days then installed the new BHAF with the Filter minder and it hasn't moved.

 

[NoSeeUm]

Jim - Great post! Guys, make sure to click on the "here" in Jim's post and follow it through - there's a ton of data Jim listed with temps and speed + loads + OAT (outside ambient temps). Good stuff Jim - Thanks,

Thanks Joe. There is allot more that I don't understand about this than I do understand. I do know that lower intake temperature directly relates to lower exhaust temperature.



As far as air flow goes, I have a spread sheet that Diesel Freak helped me allot with. I can plug in the boost and RPM and it kicks out CFM. I am going to say I am accurate + or - 100 CFM.



But for discussion, have patience with me.



Taking a look at a stock configuration. Air flow for 23 psi boost and 3200 RPM is 860 CFM. This IMO should be an indication that the stock air box is good for around 900 CFM with a new filter element installed. My guess would be that even the OEM would throw some slop in there for a clogged filter element. How much I have no clue.



Taking a look at a modified configuration at a more usable RPM. Air flow for 35 psi boost and 2700 RPM is 950 CFM. For most people 2700 RPM would likely a the upper RPM for normal shifting with a manual transmission. So engine air flow would normally maximized near the 950 CFM level and only peaking there for an instant. I can see automatic transmissions hanging up there longer. For comparison, air flow for 35 psi boost and 2500 RPM is 880 CFM. Another example of a full power towing situation, air flow for 28 psi boost and 2200 RPM is 670 CFM.



Not too many places do I see anyone bragging about the stock air box flowing 1000 CFM, hence the BHAF. But from what I am thinking, Neil was right. The stock air box will work fairly well up into the high 300 Hp values as long as you keep the air filter clean and don't park your engine for long periods of time at high boost / 2500 RPM plus.



I appreciate your comments.



Thanks;

Jim

 

[NoSeeUm]

...

That being said, I'm also on a quest for cooler air. I got one of these:

www.e-bodyparts.com/miva/merchant.m...&Category_Code=72-Dodge-Truck&Product_Count=0

...

Man oh man, a hood scoop would be the ultimate. For me, the $ per Hp gained could probably be better spent. But in your case, a guy with twins, like a said before its the ultimate. Plus its a huge bling improvement.



Post some pictures when you get it done.



Jim

 

[NoSeeUm]

Anyone happen to know what the scale of the Filter Minder is?



Mine reads 0 to 100%.



Thanks;

Jim

 

[NoSeeUm]

OK I modified my spread sheet a little and ran some numbers. I wanted to compare different filter restrictions. Basically, in our case, the driver of the truck might reduce maximum usable Hp by lifting his foot as EGT's rise. At any rate, take a look.



Constants

T1 = 60 F (compressor inlet temperature)

Pamb = 14. 7 psia

DPic = 3 psi (pressure drop across intercooler)

CE = 70 % (compressor efficientcy)

IE = 73 % (intercooler efficientcy)

VE = 85 % (volumetric efficientcy)

RPM = 2500



Variables

DPf = air filter pressure drop

T2= temperature at compressor outlet

T3 = temperature at manifold (after the intercooler)

P3 = pressure at manifold

DR = Density Ratio

CFM = air flow at the compressor inlet



No air restriction

DPf = 0

P3 = 20

T2 = 269

T3 = 116

DR = 2. 13

CFM = 490



Example 1

DPf = . 5

P3 = 20

T2 = 280

T3 = 119

DR = 2. 20

CFM = 505



Example 2

DPf = 1. 0

P3 = 20

T2 = 287

T3 = 121

DR = 2. 27

CFM = 521



Example 3

DPf = 2. 0

P3 = 20

T2 = 306

T3 = 126

DR = 2. 42

CFM = 557



Example 4

DPf = 4. 0

P3 = 20

T2 = 352

T3 = 139

DR = 2. 82

CFM = 648



Notice how T2,T3, DR and CFM change. These conditions would be for a stock engine with the turbo running against the waste gate. A down side I see is the added heat rejected by the intercooler into the radiator. My guess is that EGT's would likely only rise a little. Lets raise the waste gate setting, but keep in mind that likely in the real world the CE would drop and I have not shown that here.



No air restriction

DPf = 0

P3 = 30

T2 = 329

T3 = 133

DR = 2. 67

CFM = 614



Example 1

DPf = . 5

P3 = 30

T2 = 339

T3 = 135

DR = 2. 75

CFM = 633



Example 2

DPf = 1. 0

P3 = 30

T2 = 349

T3 = 138

DR = 2. 84

CFM = 653



I think the stock air box is still good here, buts lets add a BHAF that adds 25 F to T1.



No air restriction

DPf = 0

P3 = 30

T2 = 367

T3 = 161

DR = 2. 67

CFM = 614



Example 1

DPf = . 5

P3 = 30

T2 = 377

T3 = 164

DR = 2. 75

CFM = 633



Example 2

DPf = 1. 0

P3 = 30

T2 = 387

T3 = 167

DR = 2. 84

CFM = 653



Notice that the DR and CFM do not change compared to the numbers above for the non-BHAF. This is because you have the same change in temperature, but overall those temperatures are higher. EGT's would be going higher also because T3 is going higher directly effecting EGT. For grins lets add a Banks Technicooler Intercooler, that improves over stock by 25%. I have not reflected a reduction in Intercooler Pressure Drop, but likely there would be 1 to 2 psi less.



Example 2

DPf = 1. 0

P3 = 30

T2 = 387

T3 = 112

DR = 3. 22

CFM = 740



Biggest thing to notice is the reduction in T3. But lets make things equal. We do this by reducing P2 by close to 4 psi and by raising CE by 5%. Here is what that looks like.



Example 2

DPf = 1. 0

P3 = 26

T2 = 343

T3 = 108

DR = 2. 85

CFM = 653







Jim

 

[NoSeeUm]

Lets try some different turbo's.





CE=55%

DPf = 0

P3 = 30

T2 = 403

T3 = 153

DR = 2. 58

CFM = 594



CE=70%

DPf = 0

P3 = 30

T2 = 329

T3 = 133

DR = 2. 67

CFM = 614



CE=85%

DPf = 0

P3 = 30

T2 = 282

T3 = 120

DR = 2. 73

CFM = 627



Notice that as CE goes up T3 drops and CFM increases. Now lets up the boost pressure.



CE=55%

DPf = 0

P3 = 40

T2 = 469

T3 = 171

DR = 3. 07

CFM = 706



CE=70%

DPf = 0

P3 = 40

T2 = 382

T3 = 147

DR = 3. 19

CFM = 734



CE=85%

DPf = 0

P3 = 40

T2 = 325

T3 = 132

DR = 3. 27

CFM = 753



Same deal except every number is higher.







Jim