100 Proof - I see you remember your Chemistry classes well

 

hey good job on the detail 100proof. Thats exactly what's behind my thoughts -- I just didn't go to that level of detail, but I figured that the exhaust side would be around 4-5 times the CFM of the intake side.

But your numbers show that we need a little more CFM on the intake side than I thought. If the 5.9 is to exhaust at 2000 CFM (that is really extreeme) then we need every bit of that AFE PG7 and torque tube. looking at it another way, if the AFE is to provide 623 CFM, then it will present a restriction of about 2" water.

and the other thing we are ignoring here (of course) is the fact that the gas exiting the exhaust is not the same gas as enters the intake!

 

that is where 100proof let "n" be a constant for simplicity. this gets tricky pretty quick trying to figure the number of mols of your "gas"....and this will have a large effect.

what value did you use for "n" 100Proof?

JKE

 

I didn't use a value. I just assumed the simple case where n is equal on both sides of the equation and cancels out. Again, a gross simplification.

There is also another thermodynamic effect I haven't mentioned going on in the intercooler. I haven't put alot of thought into how that affects the mix yet.

100 Proof

 

I'm a little lost on all these intake CFM calculations. Seems to me the easiest way to calculate it would be based on the cubic displacement of the engine, rpms, and the pounds of boost. I'll use 3500 rpm and 35 psi boost for my calculation:

5.9L = 0.21 cubic ft displacement
4 stroke engine : 0.21/4 = 0.052 cubic ft/revolution
3500 rpms : 0.052 * 3500 = 183 cfm (no boost)
35 psi boost means intake air is at about 3.4 atmospheres
3.4*183 cfm = 622 cfm needed at front side of filter

This is, of course, approximate since intake air temperature is higher in the intake manifold than at the filter. But higher intake manifold air temperature would result in less dense air and therefore require lower airflow across the filter than the calculation above determines.


Side note: Google has a great conversion calculator. In the Google search box type something like "5.9L in cubic feet" (no quotes) and it provides the answer. It even works on a calculation like "35 psi + 1 atmosphere in atmospheres".

 

I just took the easy way out and looked up engine data in the Nelson catalog. The Cummins ISB model 275 engine at 400 HP exausts at 1613 CFM and requires 608 CFM on the intake. thats at 2500 RPM.

so good job badunit.

Add I think we've sufficiently established that we need a minimum of 600 CFM on the intake for even moderately bombed trucks. We've attacked it from pretty much all angles and come up with a similar answer -- 600 CFM. The question is at what restriction? less is better...

 

when ya'll figure all this mess out, somebody send me an e-mail or p.m. and let me know what filter to go with!!
later, dustin

 

well if you ask me, the AFE needs to be evaluated against its claims. it certainly claims to meet the flow requirement, but whether or not it does so with an acceptable restriction after it filters any dirt may be another story! oh, the need for standardized testing...

 

It would seem that even the stock filter at 14 in of water isn't all that restrictive. 14" of water is about 0.5 psi which is a loss of about 3% over no filter at all (difference of 14.2 psi to 14.7 psi). However, I have no idea how much effect 3% (or so) more air has on reducing EGTs.

I'm more concerned about the measurement that was made of a 10" Hg drop with the factory airbox and filter. That is about 7 psi and is a significant drop; the density of the air being compressed would be nearly halved and you should certainly notice this on your boost gauge.

 

After following this thread to the end, Doug do you give the thumbs up on the AFE system? I have one that just arrived and if this is a smoking gun and does not really work the return shipping seems to be a bargin. Thanks for the physics lesson You must agree there is a lot of talent on this site

 

I'd like to add something, I'm not sure it means much but it has to do with the filter minder. When I was modding my stroke I built a homebrew open air filter set-up. As I researched on how to go about it, I found that the filter minders are calibrated to the filter set-up, not universal.

A guy named Dale Isley of Tymar perfomance has done a lot of research into the open air set-ups and might be a good place to get some info from. If I remember correctly, the Donaldson filters out flow any other aftermarket filter set-up. He also has differerently calibrated filter minders for use with the open air set-ups.

 

the effect of a 3% loss would probably depend largely on the efficiency of the turbocharger. Check my thinking here, but in the very best case (turbo within its efficiency map), I would think a 3% loss of turbo inlet pressure would be reflected linearly across the compressor and appear as a 3% loss in Manifold Absolute Pressure. for example, if you are able to achieve 30 lbs of boost (44.7 lbs MAP) with no filter at all, adding the stock filter would reduce boost by about 1.5 lbs (3.4% of 44.7), such that your boost gauge would now read 28.5 lbs instead of 30. I used 3.4% because .5 psi is 3.4% of 14.7.

Oh, and those restriction numbers for any filter (AFE, stock, whatever) are no doubt specified when the media is new. we don't know how bad the restriction gets when dirt gets trapped

Anyway, AFE s claiming restrictions in the POINT ZERO SIX (.06) psi region (1.5" of water). even if we double that (and assuming we can, to estimate restriction at 600 CFM), we are still in the sub .1 psi region (due to filter restriction) and a net loss in boost (in the above example) of some small fraction of a psi that too small be meaningful. BTW, those restriction numbers are with the AFE torque tube. as it turns out there is a fair amount of restriction in the factory intake tube.

So I would look for about a 1 psi increase in boost when replacing the stock filter with the AFE + torque tube intake system. unless of course there are other limiting factors.

LRAmberson: My approach to the AFE intake system at this point is that its claims are attractive. we need the low restriction to obtain maximum boost and to minimize EGTs. Especially given the above, the very low claimed restriction of the AFE makes it like a pretty package on christmas morning -- we want to open it up and see what's inside. AFE is from all appearances a reputable company and is alone in the industry in high flow, low restriction filtration that claims to meet the efficiency standards of the stock paper filter. Thats an extraordinary claim; one that needs a deep dive investigation.

So I'd say go for it. But wait to install it until you change your oil -- then take your oil sample (100% used with the stock air filter) and get it analyzed. This has all been done before, but I'm saying this so that you can protect yourself in the event of a warranty dispute. Your oil analysis will show silica levels (dirt). What you want to show is that the new filter doesn't let any more dirt into the engine than the stock filter did. so let your existing oil go to the full drain interval as specified by the factory (silica levels rise with time and miles). change the oil and put on the new filter. then analyze again at the next drain interval.

If you have a lot of miles on your factory filter, your silica levels may be a little elevated. the best and most fair oil analysis test is to put on a new factory filter and change oil, go for 7,000 miles, then anyalize, then change oil again and put on the AFE, and run it for 7,000 miles. or do it in the reverse order. For example, if you are anxious to put on the AFE, then change oil right now, then run the AFE on new oil for 7,000 miles or whatever drain interval you are running. Always compare filters with the same number of miles on them.

Also note that this is only one data point and won't actually prove filtration effectiveness. you need a trend to establish any statistical significance. But this will get you into the ballpark. Once you have the AFE installed, have your oil analyzed at every change -- that will establish a trend.

My guess here is that frequent cleaning and proper oiling will optimize the AFE performance. AK's experience suggests that the filter isn't as good once you clean and re-oil, so we need to be watchful of that. maybe cleaning frequency has something to do with it. But any oiled filter would be subject to that problem, and there are many out there. AFE PG-7 just happens to be the only one claiming stock filtration effectiveness along with the high air flow.

 

Thank you Doug for your reply. I have just switched to AmsOil Synthetic with full bypass filteration. I am a kid at Christmas and do like new toys, I will follow your lead and have analysis done on a 7500 mi basis and see the results. I feel that AK's filter minder might be weak as in early 03 units and was changed to a stronger spring in late 03 (as per my service manager) I have over 15K on this truck and the filter minder has never moved. My air box is modified and why I would change to a more restrictive system, the BOMB bug and to have the efficiency of increased flow. I guess I will open the package it's only money.... I also went with the full replacement of the intake track with the torque tube. Still waiting for the Van Aken upgrade box & Piers Bomber lite. The next chapter in upgrades

 

excellent. The more guys we can get to do oil analysis the better - that will help establish trends. I'm about ready to bring in the AFE and do this myself. It will be interesting to see what your reaction is to the noise -- the torque tube is reported to be very loud!

 

Ya'll had to start this again, didn't you.

I've been do'n some research since we last left this discussion. From our conversation, when looking at published CFM ratings for filters, it would suggest that 1" of H20 restriction is more restriction than 10" H20. As an example, the Donaldson B105006 flows......

480 CFM at 6" H20
680 CFM at 10" H20

....suggesting that 6" H20 represents more restriction since the filter flows less at that level. This also indicates that 1" H20 is the most restriction you could possibly put on a filter. Not the case. We have it backwards and are not even on the right track with interpreting these numbers.….according to Fleetguard and Donaldson.

The following is what Donaldson has to say on the subject: What these numbers are showing you when looking at a filter manufacturer's CFM ratings is the amount of restriction present, created by the filter media as a result of volumetric efficiency, at the CFM requirements of a given engine based on RPM. Did you get that?.....volumetric efficiency?......Hhmmmmm.

Fleetguard added: When referring to H20 restriction on a new filter, it is an indication of how well the filter filters. The engine manufacturer picks a standard of H20 restriction for their engine based on how well they need the filter to function and how much it must flow at that level of restriction taking into consideration how well it will flow when ready to be changed. Their standard tells them that if a filter filters X CFM when new at X inches of H20, then it will flow X CFM at X inches of H20 when ready for changing. Most filter manufacturers will give you an air flow range. Generally, the range indicates it's best flow when new and its worst when the filter is ready to be changed. It is up to the engine manufacturer to also determine the maximum H20 limit, meaning the filter needs changing because it ain't flowing enough any more. The standard for all of this is already set. The filter manufacturer is just telling you which standard they meet by their published CFM and H20 numbers.

Again Donaldson followed with: Using B105006 as an example, 480 CFM at 6" H20 does not mean that the filter will only flow 480 CFM when 6" H20 restriction is present. It means that if an engine's maximum CFM requirement at maximum RPM is 480, then this particular filter will present 6" H20 restriction as the air flows across the filter at 480 CFM. If the engine's maximum CFM requirement is 680 CFM, then this filter will present a 10" H20 restriction as the air flows through the filter at 680 CFM. This allows you to pick a filter that most closely matches your engine's specifications. When an engine manufacturer sets a required CFM rating, the engine manufacturer also will set at what " H20 restriction level that CFM needs to be at.

Oh really……so I then talked to Cummins. Super cool folks there. Told them what I was doing and they pulled the spec sheet. Sure enough, they said the 5.9 standard SO in the 2003 Dodge requires 660 CFM for optimal performance. This CFM needs to be available with 10" H20 restriction on a new filter and the filter must be changed when it reaches 25" H20. I asked why 25" H20. He said that is the industry standard. Almost every filter must be changed somewhere between 20" and 30" H20. Very seldom will you see anything that needs to be changed more or less frequent than that. That explains why when I was looking at aftermarket semi filter minders, they are all calibrated to between 20" and 30" H20. So I asked "So, what if I were to double the horsepower of this engine, would that double the CFM requirements?"…and he said "Your going to double the horsepower of THAT engine?"…and I said…"Hypothetically speaking, of course."….and he said with a calmer voice that the formula for figuring that out wasn't quit that simple, but it would not double the CFM as 5.9 C.I.D will only hold so much air. Well, I'm think'n go from 23 lbs of boost stock to an HX40 and over 40 lbs....yeah, I can see us almost doubling what we shove in there.

So, a stock 250hp SO engine needs 660 CFM at 10" H20. Double the horsepower to 500, add one HX40 of your favorite variation, and a BHAF that flows 1200 CFM or better at 10" H20 and your set. All you High Output and 325/600 terds need to call Cummins and get your CFM ratings so you can pick you out a BHAF. I already got mine.