I know many of you are steadfast in what you think is the best setup for a BHAF but I just have to ask, why must a box be built around one to keep hot air from going through it when our engine setups have an intercooler installed. I understand blocking off hot air would help, but would a BHAF with no heat shield still yield better results than a stock box and filter?
Just trying to wrap my hear around it. I appreciate any input.
I have been dicking around with my engine so I don't quite know where it will go just yet. ...let's just say for a stock setup, which one would you guys advise?
the cooler/denser charge to the compressor the better, regardless of the fact that the compressor causes the air to heat up (as that happens during and post compression)
Pretty much anything other than a factory panel filter is a gain. The BHAF (depending on the actual filter used) fan support alot of power, but you would obviously also gain from at last building a shield for it, better yet a sealed box.
Their is also nothing wrong with using an aftermarket filter in the stock box, the box itself will support a fairly warmed over setup
appreciate it ykdave. I assumed cooler would be better and more air would be better. Just didn't know where a BHAF stood compared to a stock setup. I'll just take what I've setup for myself and try to cool it down.
their have been a few studies that have proven the air flowing arround the engine compartment is not a heck of a lot hotter then the ambient air due to so much air flow through the compartment. something like 20 degrees or so?
I run a bhaf just hanging off the intake hose, no box or shield required. It works fine for me, though I might be leaving a little power on the table by not shielding it.
So if I, like several others, just have a BHAF hanging off the main intake hose I should build a shield around it to keep the hotter air away. Done and done. But should I also consider drilling that hole in the fire wall that many on here do to pull cool air from behind the firewall? Would this have an added benefit to a BHAF.
please don't reply telling me to search. I have and a hole in the firewall is used on closed systems or even connecting a stock air box to outside air. Would a free-flowing filter benefit?
I don't think you'll get much benefit from drilling this hole. You would need to build a sealed air box for your BHAF and duct it to the cutout in order to get the benefits.
That is what I had first assumed but after reading all the crap on a one degree difference playing so a role I figured I may just be wrong. Thanks Tom.
The top of the graph say intake temp. Is that where the filter itself takes in air (obviously a closed system would be cooler) or after it is cooled by the intercooler? Post-intercooler would be the only numbers that would interest me.
reflective, yes. equivalent, highly doubtful. True one may be colder than the other but you can't say that if a closed air system is 20 degrees cooler at the filter that it will be exactly 20 degrees post-intercooler.
Imagine two objects. One is 150 degrees and the other is 300 degrees. If they are put in a similar environment (intercooler at ambient temperatures) both will drop, that is understood. In the end, the one that started at a lower temp will in fact be lower but they will not drop at the same rate.
Newton's law of cooling states that he greater the difference between the temperature and ambient temperature (intercooler), the faster the rate of change in temperature.
I ramble in such a way to show that if the graph took measurement from the filter area and not post intercooler, than the temps prove nothing. The "hotter" BHAF may take in warmer air but it is possible (not very likely that it will be cooler than stock though) that the temps could be close enough to not make a viable difference post-intercooler.
So if the temp post-intercooler is only off by a few degrees, I will stick with a BHAF to allow air to move freely and enjoy the sound of the turbo.
I can tell you during the summer my PSM setup dropped my IAT's about 100 degrees. PSM's setup uses the factory air box with a silicone hose feeding air from the cowl. The engine also draws from the low pressure zone created in the cowl area. I seem to get better MPG than most numbers posted around. 18-19 during the winter, mid to upper 20's in the summer.
The "hotter" BHAF may take in warmer air but it is possible (not very likely that it will be cooler than stock though) that the temps could be close enough to not make a viable difference post-intercooler.
So if the temp post-intercooler is only off by a few degrees, I will stick with a BHAF to allow air to move freely and enjoy the sound of the turbo.
Illflem pointed out the temps were taken post IC so I can't argue that. But it's a law of physics that an object with a higher temp (compared to an identical object of a lower temp) has a larger drop towards ambient temperature. And with 17-18 degrees POST-IC, I don't consider that huge. My beginning argument was only that an object of a higher temp drops quicker, not lower overall, but quicker. Ergo,
Example, if you have 100* intake temps vs 150* intake temp the discharge of the IC will be 50* higher, respectively.
Illflem pointed out the temps were taken post IC so I can't argue that. But it's a law of physics that an object with a higher temp (compared to an identical object of a lower temp) has a larger drop towards ambient temperature. And with 17-18 degrees POST-IC, I don't consider that huge. My beginning argument was only that an object of a higher temp drops quicker, not lower overall, but quicker. Ergo, just isn't true.
A stock filter setup may have lower temps but it's not respective.
I don't dispute the law of which you are speaking about, however...
You are failing to see that a IC is less than 100% efficient. So if you have a 50* difference in compressor discharge temps you will see a >50* difference on the discharge side due to the inefficiency of the IC.
regardless of effectiveness of the IC it still applies.
say the IC is only 40 or 50 percent effective. The type of filter flowing into the IC doesn't matter. The IC still cools the same. But by using the law, A hotter air in-flow would cool more than a cooler air in-flow. Not saying a hotter filter would run cooler than a cool filter but the temperature drop from a hot filter would be a larger drop then a cool filter.
The cool one may run ice cold but the hotter filter dropped more degrees.
I'm thinking about getting a 12v freezer to rig up under the hood and run the intake tube out of that. ...or move to the north pole. Both would probably be really efficient.
It's still called a BHAF, Big Honkin Air Freezer, so it might get confusing talking about it with those of you running BHAFs.
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