Intercooler Conundrum

[anokabball24]

Every night, laying in bed, after having this cross my mind for the last 3 years of my life...

I have decided I must see what others think...

I hear a lot of people say go with an NPR intercooler or a Powerstroke cooler. I always see people with vans getting pointed in this direction. However, I'm not sure if it's the best option.

Take an NPR cooler for example, an NPR truck is probably running around 50 pounds of boost give or take . . . I don't know the exact amount, this is an assumption. Along with the big strokers . . . so basically, we'll just say more boost than any of our cars can make. Now don't you think running an intercooler designed specifically for huge boost applications would be improper for our applications? How is a 2 X 3 foot intercooler going to be efficient for a car running 15 pounds of boost? Yes it will make the air much more dense, but won't that 15 psi loose a ton of it's pressure because it's spanning such a large volume? I don't think bigger is better, take the Spearco coolers, not large, nice and compact, but with huge runners, thus, keeping pressure we'll, but also allowing for maximum cooling....

I'm sure this topic has been discussed a bazillion times, but I felt like posting it again.


Tony

[DomChassis]

you must be an engineer.

You can try both. I'm certain, regardless which one has more volume, which ever one is more efficient at cooling an flow will make more power. With better drivability. It is a little different than hydraulics. It will take a little more volume of compressed air to raise the pressure in the larger unit. Benefits far outweigh the cons.

[anonymous_user]

I disagree.

20 psi is 20 psi no matter what size container it is in.

It may take more time (lag) to pressurize that giant intercooler.

[GLHNSLHT2]

the time difference is so short you'll never notice it. The difference in flow makes up for it. Powerjokes have very poorly designed end tanks and don't flow all that well. The newer NPR's have much better end tanks than their older pieces and the other pieces were nicer than the PJ's. Not sure how much the NPR's run but a PJ only runs like 15-20psi. Their max modded is only 25 due to wimpy rods. The Chevy Duramax diesel is made by Isuzu and has aluminum heads and smaller rods. Not sure how alike the NPR and Duramax are but I'd bet the boost isn't that high. A stock Dodge Cummins runs 30psi off the show room floor, but the rods are much much beefier.

[altered7151]

Tony I think you're definintally travelling down the right path. I have been thinking the same thing for a few years now. Even though the big diesel intercoolers are designed to cool well and hold alot of boost, they are also designed for low rpm diesel motors that dont have to live at high rpms. So even though you're getting good heat transfer through the intercooler. It may be choking the flow due to it design. Thats one of the things I'd really like to test when I get my flowbench built, flow testing some of the common intercoolers.

[GLHNSLHT2]

diesels flow massive amounts of air even at low rpms. going from a stock T2 i/c to a 1st gen cummins allows 300rpm higher shift points at the track with my 2.5.

[russ jerome]

Small NPR's (12-16" tall) are for the 235ci fours, they run
20-25psi max but 10-15 usualy. There max RPM is around 2700.

Bigger NPR's (16-19" tall) are for 396ci Sixes and I would imagine
have same RPM/boost rating.

I look at EVERY Isuzu,Iveco,Mitz,ect IC that comes thru our shop, every
one is made by Tokyo Radiator and share exact same style end tanks
and fin count. Never seen a difference since they first intercooled them
until brand new trucks today.

Old school thought was turbo's are HIGH VOLUME low pressure pumps
and they do in fact get pressurized in a fraction of a second. New school
thoughts from the UK to the East and back to the states is there is
apreciable lag caused by the sheer volume of fins needed to overcome
by air flow (more restrictions less flow).

Modern race coolers are going over to tube and fin(isuzu) as aposed to bar
and plate (Spearco) for less drag over turbulators (fins in cores).

Every debate I have read cops out, they all say it depends on what the
application is. Some say used truck coolers are the root of all evel while
others say they are NASA spec above aftermarket. I sure dont know

[xrattiracer]

the only things to worry about with an intercooler are that it flows enough for the given application (which is claculated without boost being in the picture), that it is reasonably efficient (which depends on design more than anything), and that it has enough cooling capacity for the application (the easiest way to define this is the maximum horespower output of the engine it should be used on).
notice that boost doesnt figure into any of those calculations? the most it should be used for is calculating the intercooler inlet temperature to help with efficiency calculations, but thats getting much further into the math than most need to.
so to help with all three of those items theres just one rule: bigger is better.

[puppet]

What I find most lacking in these types of debates is some hard and fast flow numbers. Even the math to calculate a given IC's flow isn't straight forward. The design of the channels, tanks, fins, the core entry ... all play a part in the equations. Saying that bigger is better works great in the fast food industry. I'm not so sure about intercoolers though.

[TurboMinivan]

Hi, gang. I'm gonna reply to each message individually.

Quote:

Originally Posted by anokabball24 I hear a lot of people say go with an NPR intercooler or a Powerstroke cooler. I always see people with vans getting pointed in this direction. However, I'm not sure if it's the best option.

Let me assure you: it isn't the best option. This is why I removed the PowerStroke intercooler from my van and sold it.

Quote:

Originally Posted by anokabball24 Now don't you think running an intercooler designed specifically for huge boost applications would be improper for our applications?

Maybe so; maybe not. As others have said, the boost pressure itself isn't the primary issue. It has more to do with total airflow, which is expressed in cfm rather than psi.

Quote:

Originally Posted by anokabball24 How is a 2 X 3 foot intercooler going to be efficient for a car running 15 pounds of boost?

Efficiency refers to heat transfer, and such a large intercooler will probably have wonderful thermal efficiency. Even at 24 psi, I could make a quarter mile pass and then immediately put my hand on the PowerStroke's outlet tank--it was virtually ambient temperature. But that still doesn't make it the best IC option.

When going for maximum power, your primary concern will be flow drag through the core, not heat transfer. Although heat transfer will probably come in second place.

[TurboMinivan]

Quote:

Originally Posted by DomChassis I'm certain, regardless which one has more volume, which ever one is more efficient at cooling an flow will make more power.

You must not be an engineer.

Total horsepower capability is defined by air flow (cfm) through the core, not thermal efficiency. As an example, my Spearco catalog lists two cores (part numbers 2-179 and 2-196 for those of you following along at home) which both flow 1000 cfm at 1.5 psi pressure drop. It's no surprise, then, that they are both rated at the same horsepower capacity: 670. But their core dimensions are very different:

2-179 is 19.7" W x 20.75" H x 4.5" deep
2-196 is 18.8" W x 8.375" H x 3.5" deep

In the flow chart and thermal efficiency diagrams listed for each core, the lines showing internal flow drag are virtually identical. The efficiency, however, is another story: core 2-179 obliterates the other one. No surprise, really, since it is more than twice as high and also thicker.

When it comes to making horsepower, thermal efficiency is bunk. It's all about the airflow, baby!

[TurboMinivan]

Quote:

Originally Posted by anonymous_user I disagree. 20 psi is 20 psi no matter what size container it is in.

I'm not sure what you're disagreeing with, anon, so I hope I'm not going against your intent.

Based on what the engineers and their testing tells us, X psi does not necessarily equal X psi! For example: 25 psi on a single stock Dodge IC will not end up making as much overall power as 25 psi on the same engine with a triple core IC. Here are two reasons why:

#1: flow drag. The stock IC will have lots of internal backpressure in this scenario, over 5 psi based on what Gary Donovan and others who have done back-to-back testing have found. This means car A (with the stock IC) will have to generate at least 30 psi at the turbo outlet in order to end up with 25 psi in the intake. Since it's turbo must work harder, its compressor must spin quite a bit faster. This means a greater percentage of car A's exhaust gas has to pass through the turbine--this increases exhaust drag and therefore costs top-end power. Car B's intercooler, on the other hand, has virtually no flow drag at this power level. As a result, car B's turbo only has to put out 25 psi in order to build 25 psi in the intake... so we end up with less exhaust restriction and thus more horsepower than car A.

#2: thermal efficiency. We now know car A's turbo has to push out extra boost to hit our desired target. The more you compress air, the hotter that air becomes. So now we end up with extra heat in the charge air. This puts an even greater burden on our already overworked IC, and it will heat soak faster than if there were no flow drag in the IC. As a result, we'll end up with higher charge temps, which will then reduce car A's total power production. Since car B's turbo is putting less heat in the charge air, its triple core intercooler will have less heat to remove. On top of that, it has three times the core volume to absorb heat before transfering it on to the engine. Because of this, car B will have a cooler charge temp and thus will make more horsepower than car A.

This is why running X psi does not necessarily equal any other setup which is also running X psi.

[TurboMinivan]

Quote:

Originally Posted by GLHNSLHT2 the time difference is so short you'll never notice it. The difference in flow makes up for it.

Agreed. In fact, if you upgrade to an IC with less flow drag than you had before, your throttle response will improve, even if your new core has more volume than your old one.

Quote:

Originally Posted by GLHNSLHT2 Powerjokes have very poorly designed end tanks and don't flow all that well.

Also true. While a visual inspection can offer clues as to flow rate, you cannot completely judge an intercooler's true value--it's airflow capacity--simply by looking at it.

[TurboMinivan]

Quote:

Originally Posted by GLHNSLHT2 diesels flow massive amounts of air even at low rpms.

They might; they might not. Either way, the engine's airflow doesn't tell us how much flow drag there is inside the intercooler.

Quote:

Originally Posted by GLHNSLHT2 going from a stock T2 i/c to a 1st gen cummins allows 300rpm higher shift points at the track with my 2.5.

Great--your experience suggests that the early Cummins supports a little more airflow than a stock IC. Hey, even the lousy PowerStroke intercooler outflows a single stock IC! What we really need to know is this: what cfm does that Cummins IC flow at 1.5 psi pressure drop? In other words, is it barely better than a stocker? Is it significantly better? Or is it way better? Only flowtesting will tell us for sure.

Food for thought: two of our stock intercoolers outflow the PS and thus will make more horsepower.

[mech1nxh]

Quote:

Originally Posted by altered7151 Tony I think you're definintally travelling down the right path. I have been thinking the same thing for a few years now. Even though the big diesel intercoolers are designed to cool well and hold alot of boost, they are also designed for low rpm diesel motors that dont have to live at high rpms. So even though you're getting good heat transfer through the intercooler. It may be choking the flow due to it design. Thats one of the things I'd really like to test when I get my flowbench built, flow testing some of the common intercoolers.

get that bench built I will ship you stuff to test, and renumerate you accordingly

not to offend ANYONE....excellent read...
but ever wonder why diesel i/c's are so huge???
the diesel combustion cycle STARTS at TDC and continues through 40-60 deg
ATDC.....the heat energy to the turbine is huge (and hence compressor temp rise) ... design restrictions are built in to promote heat transfer....
also most diesel aps run under boost 50-75% of engine "on" time...
the design parameters are vastly different , (diesel and gas) but the principals are the same.....i/c apps should be VERY carefully though out....
trust me here folks I do know.......just my .02$