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anyone know how many cfm's the 6.5 flows. thinking of buying an intercooler and some of them on ebay list how many cfm they flow while others list how many rwhp they support. question is which one should i get. i probably don't need a king kong unit but doubt a morris mini would do the job. any pointers on what to look for would be appreciated. thanx
 

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I would base it on how big you can fit, the bigger the better.
 

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Ditto to D Cam's recommendation, bigger = cooler and reduced flow restriction
 

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I would buy it as big as would fit, some intercooling is better than no intercooling I would think.
 

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I wish i could type the noise lurch from the adams family makes, because it is very appropriate every time somebody who has never turned a knob on a flow bench pipes up about airflow.

just for reference 800 cfm on a gas engine is depending on test pressure is good for over 1600 hp in perfect conditions.

everybody spouts CFM numbers here without a clue as to what it takes to measure that amount of airflow............which is the pressure it takes to move that much air through a port, engine or whatever. Air doesn't fall through a port or engine under it's own weight, it is either blown or sucked through at a measured test pressure such as 28" of water, which is a very common test pressure in the automotive world.


everybody here tries to compute cubic inches to CFM because it seems simple..........but it isn't. Camshaft has a little bit to do with how much air goes through a particular engine.
 

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Grape,

Can you post one of your famous (or infamous :) ) plots for us regarding this subject? I have gone back through some of your posts and could not find the post I am thinking of, but I believe you had calculated right under 300 cfm, but I couldn't remember under what circumstances that figure applied. Basically.....do you have a plot or some data that will provide the cfm data for the 6.5 engine at different rpms or boost levels?

A calculation is only as good as the assumptions it is based on. I believe that in order to use the one-liner calculations, you have to make some assumptions that just aren't valid. I am very interested in this topic myself, because this is critical in the design of my intercooler. Thanks.
 

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it is either blown or sucked through at a measured test pressure such as 28" of water, which is a very common test pressure in the automotive world.quote]

But if you were testing a two barrel what would the inches of water be? Trick question relates only to carb. mfg. rating system.

800 CFM rating would be just fine for the 6.5L . Bigger is better if you can sacrifice a little lag on spool up. Going to run lots of boost, lots of hills, lots of high ambient temperatures, lots of load, get a bigger engine because your going to blow the 6.5L.
 

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I wish i could type the noise lurch from the adams family makes, because it is very appropriate every time somebody who has never turned a knob on a flow bench pipes up about airflow.

Its spelled, UUUNNNNnnnnnnngggghhhh


Your welcome.

Tim
 

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Diesel Pro, you misunderstood my question. I understand that 'brute force' engineering is always a surefire way to get a good, quick answer, but my question is what is really needed? Why stop at 800 CFM if you can fit one that can do 1200 CFM that would be even better. The real question is where do you start cutting into performance on the LOW END of the CFM. What if you can't fit an 800 CFM intercooler in a certain area - what can you go down to safely and what things need to be monitored? At 800 CFM you have CFM to spare, so I will take that number and make the following statement:

'If your IC can handle at least 800 CFM, you have no problems to worry about - fuggedaboutit - move on to the next piece'. I want to know where the minimum range rests. There is only a certain amount of air required to burn the diesel fuel and produce the stock 190 HP. Now there are losses from heat, pressure, and ducting that play into this number in a real world calculation, but how much CFM is necessary to acheive combustion in a 6.5L engine. I am certain there are certain assumptions that can be made THAT ARE VALID FOR THIS CALCULATION and using that/those assumptions, I am sure there is a relatively straightforward calculation that can calculate this required minimum CFM number. It would be easiest to look at the results on a graph, because as rpms go up - CFM required goes up. I don't believe I've seen 3000 rpms in my truck ever, and if I ever did, it would be only be for a split second. If the graph required 400 cfm at 3600 rpms, but only required 300 cfm at 2800 rpms, I can safely assume that I could use a 300 cfm intercooler since that will fit my needs 99.999% of the time.

I am asking this question for multiple reasons, but the biggest is my lack of experience in this area. I have researched this stuff for quite sometime and one thing that seems to remain constant is the following. On I/Cs that claim to handle 800+ cfm, the inlets are never smaller than 3 inches. On units with 2.5 tubing, the max cfm I have found is 600 cfm. Now our trucks come standard with 2.5 tubing - and not pretty thin wall IC tubing either. Our manifold input and turbo output pieces are cast and are rather thick so they actually have an ID closer the that of a standard 2.25 IC tube. Couple this with the fact that I know our turbos are pretty puny to begin with and I have a hard time believing our engines are using ANYWHERE near 800 CFM. I have seen people address this subject many times, but it never seems to go past the 'one-liner' calculations that simply don't do the real problem justice.

So, does anybody have a REAL WORLD graph of the minimum CFM required at different RPMS for the 6.5L. (assuming min losses in the tubing between the turbo and the manifold) I bet Grape does if he shows back up.
 

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JS I don't have a graph, I'll share with you swome history though, when working on mine I was told adequate size for mine was the Turbo Technology IC, plus being a K1500 it was all I could fit on mine in a prekitted form, The TT is adequate for a K1500 that doesn't tow big, it was also used successfully on 1st 300 Hp power project truck over on the Page, I sometimes tow big up to just under 24K when fully fueled & with spare cans of fuel, a full cab of gear & bodies and hooked up to my GN trailer loaded with the backhoe.

With the above scenario I went with the bigger is better mindset and don't regret it; so I made the JK/Spearco big IC fit, it provides 30deg delta between ambient and IAT supplied to the engine 100F day nets 130 IAT @ 10psi boost, if I were more adept with welding tools I'd be rigging mine for a DMAX IC, 2 psi drop across my IC at current size, thinwall steel tube is plenty for our boost levels, I don't know why GM went with thick wall aluminum, maybe because of casting thick vs thin is easier.

I see in your signature you have WMI, is that not working for you or are you towing so much that resupply of WMI tank is becoming an issue, what is your IAT at power levels you run at, from what I've seen reported unless towing WMI works for most folks out there.
 

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I knew some people wouldn't understand my sig - they only give you so many characters to work with. I bought the WMI from DPS-Performance, but never installed it - hence the "(not installed)" before the WMI. I would rather go WMI than air/air IC which is why I bought it, but I would rather have water/air IC over the WMI. At the time of purchase, the water/air units I had found did not produce enough of a temp drop to warrant the design, but since then I have found a unit and along with a vendor I am working with, I think I have found a good solution. Basically, I am going to sell my uninstalled WMI kit and go with the water/air IC. It may end up being a bad decision in the long run, but right now the numbers are coming back really good for the IC unit I am looking at.

Seeing as how this has been a hot point of discussion on this forum for over a year, I am setting my design up so that I can monitor the effects of the IC on the IATs and get some real world data. I plan on testing the stock setup, the stock setup with a cold air intake from ssd (another hot point of discussion), the l/a IC unit installed but not running, and finally the l/a IC unit installed and running normally. I have even worked out a deal with the vendor where he is going to let me test the 'bare bones' unit and then return it for the 'mack daddy' unit that will be my final setup. In conjunction with this, another forum member that contacted me via email is going to run an identical setup with an alternate l/a intercooler so that we can see how much difference there is between different l/a intercooler designs. Should be a pretty neat experiment that should help put some real world numbers to the l/a vs. a/a IC debate.

My issue is that most of the l/a units are rated for WAY under 800 CFM at ambient pressure. The larger units are rated for up to 1500 CFM, but the only way to get those units to plug and play is to step up to a 3-4 inch inlet/outlet. To stay in the 2.5 inch range, the cfm is limited to about 400. Now based on some of the calculations I have attempted and some of the discussions I have seen on here, that is no problem, but I still don't have a warm fuzzy. My total intake tubing run is going to be shorter than 24 inches with 2 90degree bends. It is simple and almost a straight shot, basically maintaining the same pipe ID that the stock setup uses. The pressure drop for the entire system is less than 1.5 psi, which is also phenominal when compared to the a/a units. If I were to go with the larger units which have 3-4 inch openings, the cfm capacity more than doubles, but so does the price. I don't want to add any additional cost to the system unless it is necessary, but I also don't want to limit the airflow that the system needs - hence my need for more than 'brute force' engineering. I believe, based on the HP ratings and the stock setup, that the 400 cfm unit should be more than adequate for the design, but I just want a little sanity check. In theory, 400 cfm at ambient is equivalent to 800 cfm at 2 bar (14.9 psig), so IN THEORY, I am fine. I just know that the assumptions I use to make that calculation work, don't hold up in the real world. How far off they are and what the motor REALLY needs for volume flow rate, I don't know how to tie all of the variables together to get a good number. That is why I am looking for a little feedback from some of you who do this type of calculation more than myself (which in this case 1 time would suffice).:) A graph would be best because that would show how the volumetric flow rate changes with rpm. In theory it should be linear, but due to the spooling of the turbo as well as temp changes, I almost think that it might be exponential. I just don't know for sure because I haven't ever done this calculation before.
 

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I need to chime in here (I can't help myself because I do these calculations when "creating" a cam profile).

We first need to understand what airflow requirement is being requested. Airflow through an intercooler is essentially the airflow demand of the engine. There is also the airflow requirement into the turbo (from the air cleaner), but that is the only mention I will make of that here since a "different" airflow has been requested.

As it has been mentioned earlier, the cam profile, cylinder head flow(s), exhaust restriction, and other factors all influence how much air is ACTUALLY passing through an engine. This concept is easy to grasp, somewhat difficult to measure, and even more challenging to accurately model. GM, Ford, Navistar, etc have invested hundreds of thousands of dollars in software that can model the airflow accurately given the constraints. The best we can use is some "rough" numbers, build in a cushion, and go from there. The CFM to use when sizing a CAC (aka intercooler) is the engine inlet CFM, which can be approximated closely with the N/A airflow requirement. AND BEFORE SOME OF YOU GET STARTED...don't tell me that the airflow goes up when you turbo charge. That is plain WRONG! The engine is a positive displacement pump and turning at X speed, that "pump" will consume Y air VOLUME per unit time. That is AIRFLOW. What you are confusing is mass flow of air. When you turbocharge and turbo/intercool you are increasing the density of the unit volume of airflow into the engine. That is how you should "think" of forced induction. To me, with the exception of some tunnel ram intake effects, you will never have a "volumetric efficiency" of greater than 100%. What you do have is a density increase across the turbo/intercooler that "packs" more oxygen molecules into the chamber!

WHEW! For those of you still reading, here is a chart that I hope will be useful to someone. I made this some time back when I was looking at 6.5TD cam development. The four lines in this chart are N/A volumetric effiency, air cleaner flow of N/A engine, Air cleaner flow of stock turbo engine, and air cleaner flow of a turbo/intercooled engine (at 16PSI and 85% intercooler eff).

65td airflow chart.jpg

As you can see from the chart, if you intercool and raise the boost on a 6.5TD, you had better come up with a higher capacity air cleaner (than stock)!!!!

PS: I threw in the volumetric efficiency curve for the "naturally aspirated" 6.5TD (that is remove the turbo and see what you can draw) for reference.

See! We F_rd guys aren't that bad after all...):h
 

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every cup, busch, and truck engine have VE's over 120 percent from 7500 rpm to 9500 rpm, with a single carburetor and no ram air on the dyno. A busch and truck engine make over 700 hp through a 390 cfm holley, for you airflow guys figure that out then tell me it's not possible.
 

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every cup, busch, and truck engine have VE's over 120 percent from 7500 rpm to 9500 rpm, with a single carburetor and no ram air on the dyno. A busch and truck engine make over 700 hp through a 390 cfm holley, for you airflow guys figure that out then tell me it's not possible.
It would seem to me that vacuum is the answer to your question. A cup engine is running intake runners and such that could choke the average big block engine, so they're sucking the guts out of that 390(that happens to be fully ported and polished the last I seen of one). But you also have scavenging in the exhaust and spiraled intake runners that increase it's flow abilities.
 

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It would seem to me that vacuum is the answer to your question. A cup engine is running intake runners and such that could choke the average big block engine, so they're sucking the guts out of that 390(that happens to be fully ported and polished the last I seen of one). But you also have scavenging in the exhaust and spiraled intake runners that increase it's flow abilities.
Scavenging is the heart of HP in any NA motor, the ability to efficiently remove and replace bad air with fueled air. COMPLETELY different in the case of turbo engine.
 

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every cup, busch, and truck engine have VE's over 120 percent from 7500 rpm to 9500 rpm, with a single carburetor and no ram air on the dyno. A busch and truck engine make over 700 hp through a 390 cfm holley, for you airflow guys figure that out then tell me it's not possible.
Oh yes, it IS possible. It is called sympathetic or "resonant" tuning. That is the exception that I mention when I referenced no VE's over 100%. You cannot physically take X volume and cram it into .9*X volume without increasing density, so essentially the resonant tuning is a sort of "forced" induction. The mass (flow) is actually the most accurate technical term to reference in a forced induction application, since that accurately reflects an efficiency of NO MORE than 100%. My hang up on "no VE's over 100%" is really a matter of symantics. When I hear people reference those VE's over 100% in a forced induction application, it tells me that they do not have a grasp on what is actually happening inside that engine. It is just a pet peev...

Resonant tuning is a very valuable aspect to understand. It can make a torque curve very "peaky" or allow one to manipulate that curve to be very broad...
 

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AND BEFORE SOME OF YOU GET STARTED...don't tell me that the airflow goes up when you turbo charge. That is plain WRONG! The engine is a positive displacement pump and turning at X speed, that "pump" will consume Y air VOLUME per unit time. That is AIRFLOW.
Goldburg, I have to disagree. I have considerable airflow measuring experience and what you are doing is confusing the volume of the container (engine displacement here) with the volume of air contained within it. In non-pressurized systems (or incompressible liquids) they are the same, but in pressurized systems they are not. Airflow through a pressurized system (be it ductwork or an engine) is always listed as if it were at a standard atmosphere of pressure. So while it is true that a 6.5L engine has 6.5 liters of physical volume, the volume of the air moved by this pressurized system is not the volume of the cylinders but the volume of air that is *drawn into the intake*. THAT'S the airflow through the engine. In a non-turbocharged system the intake air and the volume of the cylinders are essentially the same, but in a turbocharged system the amount of air pulled into the intake is significantly greater than the volume of the cylinders. For example, 6.5L of 2 ATM air in the cylinders requires 13 liters of 1 ATM air at the intake. That 13L at the intake is the airflow, not the 6.5L cylinder volume.

I also have a question about the chart you posted. It indicates that a NA 6.5L engine pulls 390 CFM of air at 1000 RPM. How can that be? The volume of a 6.5L engine is 6.5L and at 1000 RPM it pulls 6,500 LPM of intake air (6.5 L/revolution * 1000 Revolutions/minute = 6,500 LPM). That's only 230 CFM, not 390. Yes, there are various restrictions in the intake and exhaust systems that change this theoretical 230 CFM volume somewhat, but they would only reduce the amount of airflow even further. How do you account for the extra 160 CFM shown on the chart? At first I thought you must have been measuring a 7.5L, but no, that would still only be 265 CFM.

I'm not out to get you here! I think you made a mistake in one area, and I hope you can just explain the chart data.
 

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Goldburg, I have to disagree. I have considerable airflow measuring experience and what you are doing is confusing the volume of the container (engine displacement here) with the volume of air contained within it. In non-pressurized systems they are the same, but in pressurized systems they are not. Airflow through a pressurized system (be it ductwork or an engine) is always listed as if it were at one atmosphere of pressure. So while it is true that a 6.5L engine has 6.5 liters of physical volume, the volume of the air moved by this pressurized system is not the volume of the cylinders but the volume of air that is *drawn into the intake*. THAT'S the airflow through the engine. In a turbocharged system the amount of air pulled into the intake is significantly greater than the volume of the cylinders. For example, 6.5L of 30psi compressed air requires 13 liters of 15psi air (~ 1 atm) at the intake. That 13L at the intake is the airflow.

I also have a question about the chart you posted. It indicates that a NA 6.5L engine pulls 390 CFM of air at 1000 RPM. How can that be? The volume of a 6.5L engine is 6.5L and at 1000 RPM it pulls 6,500 LPM of intake air, which is only 230 CFM, not 390. Yes, there are various restrictions in the intake and exhaust systems that change this theoretical volume somewhat, but restrictions (including the indicated 28" W.G. pressure drop across the filter)only REDUCE the amount of airflow, not increase it. How do you account for the extra 130 CFM shown on the chart? At first I thought you must have been measuring a 7.5L, but no, that would still only be 265 CFM.

I'm not out to get you here! I think you made a mistake in one area, and I hope you can just explain the chart data.
I can explain what's happening: you're reading the chart wrong! The black line is NA volumetric efficiency, so look at the Y scale on the left (not right). According to the NA Air Cleaner flow line (the red one), the 6.5NA is only moving about 100CFM at 1000RPM. These calculations take into account the 6.5TD cam profile and an approximation of the restriction of the inlet and exhaust tracts.

With regards to your opinion on "airflow through the engine", what YOU are referencing is aiflow "through the air cleaner". The ONLY way that I would concede that you are correct, is IF you are referring to airflow in terms of mass, which most people do not. 99.9% of the people that I converse with, talk about airflow in terms of CFM. With regards to the volume flow (CFM), the engine only flows so much volume whether NA or turbo'ed. The density of that charge is what changes, not the volume flow. This is the whole crux of my pet peev, and you stepped right into it!

Not pickin' a fight or confused either...:eek: This is what I studied at Purdue! Also, I have done these calculations for other people for the last 10 years (or so)...

You don't see charts like this posted in Forums like these very often! They typically only lead to more confusion when people are "overloaded" with data...
 
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