Air Box - New Holes ??

[R C Cola]

Work my truck hard and am always looking for low cost power. Have noticed many suggest drilling additional holes in the factory air box to allow more air to the air filter. Easy to do but, ... The reason for the intercooler is to keep the temp of incoming air down. The air inside my engine cavity is a lot hotter than outside air therefore not producing as much power. Is there truly a good gain from allowing this extra air (Hot) in to the system. If some of you have had experience maybe there is a way to get more cool air into the air box? Right now the size of the factory air intake is somewhat small but it is outside cool air. Thanks R C

 

[WashingtonFLHTRider]

Anytime you can get more air your going to gain. Your net gain would be much better if you were able to make the gain in cold air as opposed to hot air. Just my 2cents.

 

[cerberusiam]

Several members ran some tests on under hood temps in different areas and at different speeds. The conclusion was unless you are are in slow stop and go traffic the underhood temps are not much higher than the outside air. There is enough flow thru the radiator, rad support, and around the bottom of the engine compartment you need not worry about underhood temps when considering filter placement.



Opening up the stock air box exposes the filter to more air intake surface and it will breathe better but the filter is small and if you start pushing over 20 psi of boost it will still be a problem. A BHAF with an Outerwears prefilter mounted/hung in the same place as the stock air box is an excellent upgrade and will provide plenty of air.



If you want more outside air under the hood you can enlarge the hole in the rad support where the stock duct resides. I have mine enlarged to about 4 times the original size and the jack removed. Some quick fabrication with sheet metal could produce a better routing effect and increase the clean air quite a bit.

 

[JLEONARD]

I have the factory airbox and a K & N filter that fits inside.

My K & N is about the same size as the BHAF.

I also have drilled 6 2 1/4 inch dia holes into the airbox. (that was the largest hole saw I had at the time).

I never noticed any appreciable difference in EGT.

However, now the filter has dirty spots where each of the holes are. That tells me that I am getting more air into the airbox.

Don't know if this is a help or not, just explaining my experience.

Jay

 

[dpuckett]

I cut a bigger hole in the airbox of Mom's pickup when I owned it- no gauges, and saw several TDR members had done it. I have since traded airboxes to my pickup (which still had the stock box with the duct from the outside), and ran with each one for about a month, same K&N filter. No appreciable difference in cruise EGTs or boost. The bigger hole might have given me a psi or two of boost on the top end; no noticeable difference in EGTs. This was with 35psi peak boost. Unless you tow a lot, or run a lot of boost a lot of the time (i. e. have a real heavy foot), I wouldnt mess with it, personally. I now have a BHAF with no box (filter is BIGGER than the box), and dropped 50deg cruise EGT, dropped maybe 75deg peak EGT. No boost difference that I could tell- still around 37-38.



Daniel

 

[R C Cola]

Great feedback more ???

Based on this info. I tow very heavy all the time. 20 to 26K gross. AFE installed in factory air box. Should I go up to a larger !! filter and with what results. Presently considering large hood scoop to reduce underhood temp and/or pressurize air intake... ... . R C

 

[dpuckett]

RC-

Unless you drastically relocate your filter, a hood scoop wouldnt help with the pressurized air, and someone said the underhood temps arent that much hotter than the outside air when moving, esp in the corner where the air filter is (though the fan can heat that area up- more on that in a bit). With an AFE, even in the stock box, with the HP in your sig, you should be fine. I can understand wanting every inch per gallon possible, but you may just be spitting in the wind with the scoop. Plus, you can buy a lot of fuel for the cost of one of them. Is your truck intercooled or not? If so, keep an eye out for a used PDR HX35 or some other hybrid HX35, or even a stock HX35 would be an upgrade from the H1C.



You could also block off the area on top of and to the engine side of the airfilter box, forcing more cool air into the filter, and blocking the hotter air from the blowing fan at the same time. I had a piece of cardboard on my pickup doing that, with the BHAF, I just have it hanging there in the open. Havent noticed any groundshaking difference in MPGs, EGTs, or boost, but it cant hurt.



-DP

 

["Mad Max"]

... on the hood scoop - I think the benefits might be that you might be able to remove some of the heat, verses actually allowing in cooler air. While the trucks are moving at highway speeds there is actually a partial vacuum created on the top of the hood, same for the sides of the fenders. The cowl area can get a pressurized effect but I'm not sure you'd see it with a truck.

I'm doing three things for my rig to aid the 'air in' - one is a 3" body lift (this will allow three inches of additional clearance between the entire drivetrain and the body, specifically the firewall and hood, second is I'm going with an old-school 6-pak hood scoop but I'm going to reverse it so the opening is in the back - this will allow hot air to theoretically flow out the top of the hood, and third is the air intake for my particular set up will be a custom made vent style opening grafted into the side of the fender - it'll be vented down and back so that rain/moisture can't get in, plus when moving there won't be any water intake (because of the air wave around the front of the truck) and lots of outside air, which is almost always cooler than the inside but not by too much, especially when driving highway speeds, but it all adds up.

Not sure if any of that babble helps, but some ideas if nothing else.

- Sam

 

[cerberusiam]

A larger filter will give you better air not neccessarily more air. The volume you intake will dependent on the boost your making and to a lesser degree the amount of restriction in the air filter. You may or may not see a difference in boost or EGT. Too much is dependent on how you fuel system is configured and how you drive it to come up with a hard and fast rule. Better air should lower EGT's and may kower boost numbers also but it is not set in stone.



A hood scoop would be a good way to route outside air directly to the filter but pressurizing may run you into some problems. A lot will depend on the cross sectional area of the plumbing and the CFM it will flow. If you completely enclose the filter box with the intake ducting and it is not capapble of flowing the CFM needed you could suffer the same effect as the stock air box.



In stock form and running down the road you should have a low pressure area developed in th eunder hood area from the larger amount of air flowing under the truck and the restrictions of air flow into the engine bay. With the flow coming thru the radiator and rad support this will create a flow that is down and back in the engine compartment. Allowing too much air into the engine compartment, with hood scoops, side vents and such, could stop or disrupt the flow to the point where too much heat stays in rather than being drawn into the slipstream flow.



If you think a hood scoop would help probably the best way to see where the flow is would be to tape streamers at places on the hood and see exactly what direction that flow is and the best way to mount scoop. Aerodynamics is another whole science that has its own set of rules. I always thought lowering the tailgate should help aerodynamics and mileage. Now we are being told it actually hurts the slippery coefficient. Maybe thats only for th enewer vehicles not the boxcars like ours but who knows.

 

[DieselMinded]

I have the factory airbox and a K & N filter that fits inside.

My K & N is about the same size as the BHAF.

The BHAF is bigger than the whole air box so any filter that'll fit inside the factory air box would be smaller



The K&N coats the impelers and inside of the turbo with a sticky grime



The K&N only filters air on a level plane the BHAF filters 360* alot more surface area to filter



After about a 25 mile drive get out and touch your turbo..... it emits alot of heat and its right beside your air intake the HEATSHELD on one side will be warm and on the filter side itll be cold I also used the factory air deflector by cutting it in 1/2 and glueing it into the fender to deflect more cold air into the filtering chamber the plastic piece orginally went in between the interfender and the air box.



Regurdless if your idleing or driving the temps at the air intake are high when @ idle they emmit from the turbo housing and while driveing the air is heated when it passes threw the radiator I have no hard test to prove this theroy just rational thinking.



I have a K&N for the factory box and Id feal like a crook giving it away.



K&N's are great for gassers but they dont have no where near the vacuum going on that a diesels got ... . its so much that it'll suck all the oil off the k&N and pull it into the turbo..... Ive even tried a spectre air intake from the ricer crowd and at about 5 miles I collaped the filter like a wad of paper ... ... and thats was at stock.



I have the BHAF with a S/S heatshield and a outerwares IVE had a spectre intake and a K&N drop-in



Hope this helps

OPINION

DM

 

[boatpuller]

The BHAF is bigger than the whole air box so any filter that'll fit inside the factory air box would be smaller



The K&N coats the impelers and inside of the turbo with a sticky grime



The K&N only filters air on a level plane the BHAF filters 360* alot more surface area to filter

Dieselminded,

In a first gen the air filter is not flat, it is round and very simular in size to a BHAF.

It is also not next to the turbo like a second gen truck, it is forward right behind the headlight.

Some of us have run K+N air fliters for thousands of miles without coating the impellor and nside of the turbo with "sticky grime" don't over oil and they work fine.

 

[DPetrey]

If you look at every diesel that rools of the plants there are all equiped with Airsep filter which they buy from K & N everything from Detroit 8v 92 to Cats and even MTU, so there doing something right or all these manufacturer's would not use them.

 

[dpuckett]

The search isnt working for me right now, but I had a thread last spring about K&N's filtering ability, or definite lack thereof. Dust inside the intake hose- enough to write my name in- after 10Kmi. You cant tell me that isnt getting into the turbo and thus the engine. And this was stock- 17-18psi boost.



Just because construction and mining companies are using them doesnt make them the best out there- they have to look at cost per hour and return on investment; quality isnt always the end-all deciding factor. Look at all the Class 8 trucks that have the pyro probe in the pipe, post turbo. In our pickups, it is next to useless there. Plus, look at all the company trucks that are PSDs.



I'm not trying to start anything, and if anyone takes offense, that is not what I intended. I'm just calling it as I see it.

-DP

 

[DieselMinded]

Dieselminded,

In a first gen the air filter is not flat, it is round and very simular in size to a BHAF.

It is also not next to the turbo like a second gen truck, it is forward right behind the headlight.

Some of us have run K+N air fliters for thousands of miles without coating the impellor and nside of the turbo with "sticky grime" don't over oil and they work fine.

I didnt know that the 1st gens had a round filter...



I think the only way to oil the K&N to the perfect specks to acheive the best filtration W/O over oiling... ..... It Would have to be done with a machine. I just coated mine till it was slitly red all over and @ 500 miles I had gunk in my turbo I cleaned it and ran another 500 miles and guess what... . gunk in my turbo... . I threw the K&N over the hill and got the BHAF/Heatshied/outerwares Ill admit I have less turbo whisle with the BHAF then I had with the K&N so maybe the K&N was letting more air flow((( but maybe not )))... ... along with oil ..... And I also kept getting leaves on the bottom of my the K&N where it was sucking threw the hole where the sleave was that went in to the fender... ... also my K&N only got dirty where it was sucking air it wasnt even useing the whole filter for filtration it was just sucking like crazy in a 3x5 area... I figger thats why it was so loud.



Not starting a filter war here just communicating my expirences.



ID say K&N's are awesome for gassers alot of gain in throtle responce I even had my brother swap out the factory filter with a K&N on a gasser and I test drove each one W/O knowing whitch one was in there and I could Tell each and every time when the K&N was in there.



DM

 

[tugboatphil]

Filtering aside, has anyone on this forum tried one of those Honeycomb things that sits over the air inlet on the turbo? They've showcased them in the new products section of the magazine, and there was an article mention of them in the latest issue. I wish I could remember the name of it. It's supposed to redirect the airflow hitting the impellor for less turbulence. The article this issue was comparing the original item with an upgraded one.

 

[cerberusiam]

TAG = turbo air guide



No, been considering it when I have a baseline established. In theory it looks good. In practice is where you can tell if its a placebo part.