One of your statements is correct, the other is not. I bolded the correct one for you.
The official 1HDT Intercooler thread (3 Viewers)
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One of your statements is correct, the other is not. I bolded the correct one for you.
CFM = Cubic Feet per Minute
You can't put more volume into a fixed space. You can compress the air to get more molecules in there but the volume doesn't change (unless it's stretchy like a balloon
)
CFM downstream of the compressor is determined by engine air requirements = Displacement x 0.5 x VE x RPM. Make sure your intercooler is rated for more that much and is rated for low pressure drop.
Factor in the desired boost and you can figure out what everything upstream and including the compressor inlet have to flow (includes snorkle, air box).
Boosted CFM = engine required CFM x pressure ratio, where pressure ratio = (atmospheric pressure + boosted pressure) / atmospheric pressure
At sea level, that's P.R.=((14.7+boosted pressure)/14.7).
As mentioned before, if your boost gauge shows 14.7psi your pressure ratio is actually 2:1. That means for every full cycle of your 4.2L engine (which is 2 revolutions of the crank and 1 revolution of the camshaft) your intake needs to be able to flow 8.4L of atmospheric pressure air.
You can't put more volume into a fixed space. You can compress the air to get more molecules in there but the volume doesn't change (unless it's stretchy like a balloon
)CFM downstream of the compressor is determined by engine air requirements = Displacement x 0.5 x VE x RPM. Make sure your intercooler is rated for more that much and is rated for low pressure drop.
Factor in the desired boost and you can figure out what everything upstream and including the compressor inlet have to flow (includes snorkle, air box).
Boosted CFM = engine required CFM x pressure ratio, where pressure ratio = (atmospheric pressure + boosted pressure) / atmospheric pressure
At sea level, that's P.R.=((14.7+boosted pressure)/14.7).
As mentioned before, if your boost gauge shows 14.7psi your pressure ratio is actually 2:1. That means for every full cycle of your 4.2L engine (which is 2 revolutions of the crank and 1 revolution of the camshaft) your intake needs to be able to flow 8.4L of atmospheric pressure air.
^I think we all agree with that adam. The part Gerg is confusing about is cfm ratings for intercooler sizing. I've since found out that bell (the intercooler in question) rate their cfm ratings at 10psi. Meaning if you want to run 20 psi and your engine cfm is 220. A 220 rated core won't do it.
I assume that means their testing is done at 10psi. They should also be stating what the pressure drop is. The CFM rating isn't a brick wall that you can't get past. You can flow more, you'll just experience more pressure drop.
Of course if you're trying to get oxygen molecules into your engine then pressure drop is undesirable.
Of course if you're trying to get oxygen molecules into your engine then pressure drop is undesirable.
Am I confused... sometimes. Is pressure drop avoidable... no. Can it be minimised...yes. Do you need a core that flows twice the cfm if you double the boost... no.
Tapage
Club 4X4 Panamá
then we aren't became to talk about intake manifold too .. ?
Yeah I know we are just seen the IC picture right now .. but to me it's always the hole view. You can focus on the perfect IC then reach the unperfect intake manifold ..
mudgudgeon
Resident galah
Mark,
have you done direct comparisons with say a 24x12x3 core vs a 24x12x4 core and measured air charge temps at inlet and outlet?
without measuring outlet temps this ^^^^ reads as a blanket statement.
Everything we do modifying cars has compromises. IMO run the largest core you can package successfully in the space you have with regard to intake piping, manifold etc as a whole package as Tapage has said.
for the sake of some very basic comparisons of dimensions (I know this is far from the whole picture)
a 24x12x3" core dimensions
volume =864cubic inches
frontal area =288sq inches
cross sectional area = 36sq inches
a 18x12x4" core dimensions
Volume = 864cubic inches
frontal area = 216sq inches
Cross sectional area = 48sq inches
the first should have more ambientair pass through it, the second has a larger cross sectional area for Intake charge air to pass through.
both have the same surface area along the length and width of the individual cores for heat transfer to occur.
If you compare a 24x12x3" core vs a 24x12x4" core, then you have almost 30% more surface are along the individual cores for heat transfer to occur.
I appreciate that as ambient air passes the the back of a 4" core, it will be hotter as it approaches the back of the core, but by the same token, as intake charge air approaches the outlet, it has had more opportunity to shed heat and is getting progressively cooler.
I find it hard to see there would be no benefit from running a thicker core. It would be interesting to see some real data on which is most effective.
No doubt there is +ve and -ve with both.
Yep. It's all give and take, and finding a happy medium. A single row/core 40mm radiator cooled better than a 60mm 2 row/core radiator. its the surface area directly exposed to ambient that matter. Then you get into the different fin/louver designs. More internal area on the possitive pressure side reduces pressure drop. But increased temps. So no real benefit. Yet increasing the surface area exposed to ambient reduced pressure drop while maintaining the same temps. If it where possible, is have a fairly thin core with a huge surface area . And obviously a good plenum design to make sure each tube is getting close to the same flow.
. And obviously a good plenum design to make sure each tube is getting close to the same flow."Now that we have the Internal Flow Area, the depth, and the width of our intercooler. Remember that a 2 inch thick core intercooler will require a wider intercooler to achieve the same Charge Air Face Area. Also, a 2 inch thick core will offer better cooling (if our Internal Flow Area stays the same) due to the increased Frontal Face Area’s (in2) access to pure, undisturbed cool air."
"There are two ways to finding a suitable Internal Flow Area, one of which is using this graph. You’lll be needing your Turbo Airflow Rate (cfm) or you Desired Bhp (Hp)"
"There are two ways to finding a suitable Internal Flow Area, one of which is using this graph. You’lll be needing your Turbo Airflow Rate (cfm) or you Desired Bhp (Hp)"
Can't see a graph.....
mudgudgeon
Resident galah
Mark, got a link to the source of those quotes?
I understand what gerg is saying, as Ive heard it before. I still dissagree with it (when it comes to intercooler sizing). And would like to get a 100% conclusion to this. The fact that intercooler sizing relates back to the desired HP or turbo cfm says its not soley chosen by the engines cfm requirements. 1 size doesnt fit all 0-50psi. All manufacturers give their own cfm ratings, some give it at atmoshere and some give it under a boost pressure. Some just give hp figures which simply dont add up. 1000hp rated core does not mean its good for 1000hp. I know during all my testing I had to simply go trial and error, all different size cores and see who/what was being qouted, was indeed correct. But wta is different again. Ive tested alot of ata's. But they are mostly standard sizes, and its usually just what fits.
Thanks for the link. iI still havnet gone completley through it yet. You have much more testing under your belt than I do it seems. I must admit that I understand that density and temperature will affect the internal flow of a cooler, but to what extent I dont really know. I too am very interested in learning more about this. I too dont like coolers that state hp ratings or erronious things like that. CFM combined with boost pressure with amibent temps and air speed over the core with pressure drop shouldnt be that hard for a company to test and provide an effeciency number. Providing that info sure wount help you sell a s*** cooler though.
So i bit the bullet and I am going to test out that Ebay Kit.
I am going to run it for awhile do some tests for overall efficiency.
I may mod it after when time permits and do the enlarged plenum thing.
Bought a Racecomposites STI scoop that I plan on modding (has a 3.5 inch tall opening)
Planning on making a louver/splitter to distribute air over the core nicely.
Stay tuned.
I am going to run it for awhile do some tests for overall efficiency.
I may mod it after when time permits and do the enlarged plenum thing.
Bought a Racecomposites STI scoop that I plan on modding (has a 3.5 inch tall opening)
Planning on making a louver/splitter to distribute air over the core nicely.
Stay tuned.
mudgudgeon
Resident galah
That's right. Why do things always have to be so hard? And confusing? I knew from the very start I would publish all to see. Efficiency, pressure drop, and temps - both water pre/post and air pre/post. The part I had not counted on is people asking me if that's good or not? As no one else posts comparative figures. Lol
