mecman

iTrader: (11)

I have the PFS intake and IC set-up and like it. It was easy to install and did not need the battery relocation. I can't comment on the performance improvement because I did several things at the same time. Overall I like the change.

clayne

One thing to also consider is that even though a larger IC may have a larger "volume" the fin density is not just kept the same as the OEM IC.
Anyways, I've quoted GNTType before and I will again, because they know what they're doing.



Currently it looks like their website is being moved, but this is what you need to know:

http://web.archive.org/web/200304140...tercooler.html

Written by John Estill

The first equation describes the overall heat transfer that occurs.
Q = U x A x DTlm


Q is the amount of energy that is transferred.
U is called the heat transfer coefficient. It is a measure of how well the exchanger transfers heat. The bigger the number, the better the transfer.
A is the heat transfer area, or the surface area of the intercooler tubes and fins that is exposed to the outside air.
DTlm is called the log mean temperature difference. It is an indication of the "driving force", or the overall average difference in temperature between the hot and cold fluids. The equation for this is:

DTlm = (DT1-DT2) * F
ln(DT1/DT2)


where DT1 = turbo air temperature in - outside air temperature out
DT2 = turbo air temperature out - outside air temperature in
F = a correction factor, see below

[paragraphs of examples removed]

So, now that we've got these equations, what do they REALLY tell us?

1. Heat transfer goes really well when there is a large temperature difference, or driving force, between the two fluids. This is shown in equation 1 as a large DTlm. It doesn't go as well when there is a small temperature difference between the two fluids (small DTlm). The closer you get the intercooler outlet temperature to the outside air temperature the smaller DTlm gets, which makes the heat transfer tougher.


2. The difference between the intercooler outlet temperature and the outside air temperature is called the approach. If it is 100 degrees outside and your intercooler cools the air going into the intake manifold down to 140 degrees, then you have an approach of 40 degrees (140 - 100 = 40). To get a better (smaller) approach you have to have more area or a better U, but there is a problem with diminshing returns. Lets rearrange the first equation to Q/DTlm = U x A. Every time DTlm goes down (get a better temperature approach) then Q goes up (transfer more heat, get a colder outlet temperature), and dividing Q by DTlm gets bigger a lot faster than U x A does. The upshot of that is we have a situation of diminishing returns; for every degree of a better approach you need more and more U x A to get there. Start with a 30 deg approach and go to 20 and you have to improve U x A by some amount, to go from 20 to 10 you need to increase U x A by an even bigger amount.


3. I would consider an approach of 20 degrees to be pretty good. In industrial heat exchangers it starts to get uneconomical to do better somewhere around there, the exchanger starts to get too big to justify the added expense. The one time I checked my car (stock turbo, stock IC, ported heads, bigger cam) I had an approach of about 60 deg. The only practical way of making the DTlm bigger on an existing intercooler is to only drive on cold days; if you buy a better intercooler you naturally get a better DTlm.


4. You can transfer more heat (and have cooler outlet temps) with more heat transfer area. That means buying a new intercooler with more tubes, more fins, longer tubes, or all three. This is what most aftermarket intercoolers strive for. Big front mounts, intercooler and a half, etc... are all increasing the area.

A practical consideration is the fin count. The area of the fins is included in the heat transfer area; more fins means more area. If you try to pack too many fins into the intercooler the heat transfer area does go up, which is good, but the cooling air flow over the fins goes down, which is bad. Looking at the 2nd equation, Q = m * Cp * DT, when the fin count is too high then the air flow ("m") drops. For a given Q that you are trying to reach then you have to have a bigger DT, which means you have to heat up that air more. Then THAT affects the DTlm in the first equation, making it smaller, and lowering the overall heat transfer. So there is an optimum to be found. Starting off with bare tubes you add fins and the heat transfer goes up because you're increasing the area, and you keep adding fins until the it starts to choke off the cooling air flow and heat transfer starts going back down. At that point you have to add more tubes or make them longer to get more heat transfer out of the increased area.


5. Make U go up. You can increase the U by adding or improving "turbulators" inside the tubes. These are fins inside the tubes which cause the air to swirl inside the tube and makes it transfer its heat to the tube more efficiently. Our intercoolers have these, but I understand that more efficient designs are now available. One of the best ways to increase the U is to clean the tubes out! Oil film (from a bad turbo seal or from the stock valve cover breather) inside the tubes acts as an insulator or thermal barrier. It keeps heat from moving from the air to the tube wall. This is expressed in our equation as a lower U. Lower U means lower Qs which mean hotter turbo air temperatures coming out of the intercooler.


6. Air-to-water. If we use water as the cooling medium instead of outside air, we can see a big improvement for several reasons: Water can absorb more energy with a lower temperature rise. This improves our DTlm, makes it bigger, which makes Q go up and outlet temps go down. A well designed water cooled exchanger also has a much bigger U, which also helps Q go up. And since both DTlm and U went up, you can make the area A smaller which makes it easier to fit the intercooler in the engine compartment. Of course, there are some practical drawbacks. The need for a water circulation system is one. A big one is cooling the water down after it is heated (which means another radiator). This leads to another problem: You heat the water, and cool it down with outside air like the Syclone/Typhoon. You can't get it as cool as the outside air, but maybe you can get it within 20 degrees of it. Now you are cooling the turbo air with water that is 20 hotter than the outside air, and you can only get within 15 degrees of that temperature so coming out of the intercooler you have turbo air that is 35 degrees hotter than outside! (turbo air is 15 deg over water temp which is 20 deg over outside temp). You could have easily done that with an air to air intercooler! But... if you put ice water in your holding tank and circulate that... Then maybe the air temp coming out of the intercooler is 15 deg above that or 45 to 50 deg. Hang on! But after the water warms up, you're back to the hot air again. So, great for racing, not as good for the street.


7. Lower the inlet temperature. The less hard the turbo has to work to compress the air then the lower the temperature the air coming out of the turbo is. This actually hurts the DTlm, but still if it's cooler going in it will be cooler coming out. You can work the turbo less hard by running less boost, by improving the pressure drop between the air filter and the turbo, or by having a more efficient compressor wheel. You can also reduce the pressure drop in the intercooler, which allows you to run the same amount of boost in the intake manifold while having a lower turbo discharge pressure. More on this later. If you can drop the turbo outlet pressure by 2 psi, or raise the turbo inlet pressure by 1 psi, that will drop the turbo discharge temperature about 16 degrees (depending on the compression efficiency and boost level). If the turbo air is going into the intercooler 16 degrees colder then it may come out only 10 degrees colder than before, but that is still better than what it was.


Pressure Drop

Another aspect of intercoolers to be considered is pressure drop. The pressure read by a boost gauge is the pressure in the intake manifold. It is not the same as the pressure that the turbocharger itself puts out. To get a fluid, such as air, to flow there must be a difference in pressure from one end to the other. Consider a straw that is sitting on the table. It doesn't having anything moving through it until you pick it up, stick it in your mouth, and change the pressure at one end (either by blowing or sucking). In the same way the turbo outlet pressure is higher than the intake manifold pressure, and will always be higher than the intake pressure, because there must be a pressure difference for the air to move.

The difference in pressure required for a given amount of air to move from turbo to intake manifold is an indication of the hydraulic restriction of the intercooler, the up pipe, and the throttle body. Let's say you are trying to move 255 gram/sec of air through a stock intercooler, up pipe, and throttle body and there is a 4 psi difference that is pushing it along (I'm just making up numbers here). If your boost gauge reads 15 psi, that means the turbo is actually putting up 19 psi. Now you buy a PT-70 and slap on some Champion heads. Now you are moving 450 gm/sec of air. At 15 psi boost in the intake manifold the turbo now has to put up 23 psi, because the pressure drop required to get the higher air flow is now 8 psi instead of the 4 that we had before. More flow with the same equipment means higher pressure drop. So we put on a new front mount intercooler. It has a lower pressure drop, pressure drop is now 4 psi, so the turbo is putting up 19 psi again. Now we add the 65 mm throttle body and the pressure drop is now 3 psi. Then we add the 2.5" up pipe, and it drops to 2.5 psi. Now to make 15 psi boost the turbo only has to put up 17.5 psi. The difference in turbo outlet temperature between 23 psi and 17.5 psi is about 40 deg (assuming a constant efficiency)! So you can see how just by reducing the pressure drop we can lower the temperatures while still running the same amount of boost.

I have seen some misunderstandings regarding intercooler pressure drop and how it relates to heat transfer. For example, one vendor's catalog implies that if you had little or no pressure drop then you would have no heat transfer. This is incorrect. Pressure drop and heat transfer are relatively independent, you can have good heat transfer in an intercooler that has a small pressure drop if it is designed correctly. It is easier to have good heat transfer when there is a larger pressure drop because the fluid's turbulence helps the heat transfer coefficient (U), but I have seen industrial coolers that are designed to have less than 0.2 psi of drop while flowing a heck of a lot more air, so it is certainly feasible.

Pressure drop is important because the higher the turbo discharge pressure is the higher the temperature of the turbo air. When we drop the turbo discharge pressure we also drop the temperature of the air coming out of the turbo. When we do that we also drop the intercooler outlet temperature, although not as much, but hey, every little bit helps. This lower pressure drop is part of the benefit offered by new, bigger front mount intercoolers; by the Duttweiler neck modification to stock location intercoolers; by bigger up pipes; and by bigger throttle bodies. You can also make the turbo work less hard by improving the inlet side to it. K&N air filters, free flowing MAF pipes, removing a screen from the MAF, removing the MAF itself when switching to an aftermarket fuel injection system, the upcoming 3" and 3.5" MAFs from Modern Muscle, these all reduce the pressure drop in the turbo inlet system which makes the compressor work less to produce the same boost which will reduce the turbo discharge temperature (among other, and probably greater, benefits).

rotaryextreme

iTrader: (2)

Actually you can see the difference of pressure drop on the boost gauge because the source of wastegate signal is before the IC.

Let's say if the wastegate spring is a 15 psi one and with a 2 psi pressure drop IC, you will see 13 psi on your boost gauge. If you switch to a 1 psi pressure drop IC, you will see 14 psi on the boost gauge. The turbo will not know how much your IC pressure drop is. It will just spin enough to keep the boost to 15 psi according to the signal source which is before the IC.

If you hook up your boost gauge before the IC, then it's a different story. But most people hook up the boost gauge from the manifold nipple which is after the IC.

So when you switch from a higher pressure drop IC (stock IC) to a lower pressure drop aftermarket one, you will see increase of boost.

Chuck Huang

FDNewbie

iTrader: (10)

HOLY (*&#(@*& LOL

If I got THAT MUCH info on every mod I was thinking about doing, I'd sell this baby and get a civic!! lol j/k

That's actually incredible how much good solid info you can learn on the forum...even from a simple question like this one.

Even tho I didn't ask it...thanks guys for all your input! Newbie is learning! haha

cruiser

I didnt see any difference on boost gauge when I installed my PFS IC & PFS intake.

I was previously running APEXi Power intakes.

clayne

Chuck you're describing a purely mechanical configuration with the compressor signal hardlined into the wastegate. Most of us aren't using that.

The only reason positive pressure at the intake manifold goes up, in a purely mechanical configuration as mentioned above, is because there are no inline solenoids regulating what the wastegate sees.

If one wants to retain the same level of positive pressure (say for instance 12 psi since they only have enough fuel for whatever CFM @ 8000 rpm that 12 psi will result in, or turbocharger limitations) with a mechanically controlled setup, then they're not going to be leaving the same wastegate spring in the wastegate or manual ball valve (if taking it one step further, mechanically) set at the previous value.

Given an electronically controlled system with MAP sensor providing input to a ECU which then regulates the wastegate solenoid, the intake manifold pressure will remain constant. Compared to a system using an IC with higher pressure drop, the turbine side will not be required to spin the compressor side as fast as before, to produce the same manifold pressure past the IC.

Yes, technically you could say: "Hey, if I was producing 16 psi pre-IC/12 psi post-IC before, why don't I just run 16 psi pre-IC/15 psi post-IC with my new kickass IC that has 1 psi of pressure drop? More boost without spinning the turbo faster, right?" Chances are, depending on your choice of TC (let's say Mazda OEM), you were pushing it out of it's efficiency range in the first place, generating exponentially higher heat and increased wear.

Don't get an upgraded IC to "jack up the boost." Get an upgraded IC to make more power @ lower turbine shaft speeds which will result in increased longevity of your turbocharger(s) and less TC compression needed to produce the same boost as before. Less TC compression = less heat. Less heat = more power.

Increase the boost limit when you have a turbocharger that has an efficiency range designed for it and the rest of the system's CFM requirements (engine, intake, manifold, downpipe, exhaust, etc.).

speeddemon7

im glad I started this thread.Its nice to see how much good info is being shared here.Before this thread I knew some things about intercoolers but now I know a whole lot more.Especially concerning pressure drop.
My main concern is of course pressure drop,fitment,cant forgett about price,and will it fit with my current intakes(blitz sus) with some modification to the intake hardpipes.
As far as which intercooler is best does anyone know anything about the blitz units? its a front mount but it has about 1 psi of pressure drop and its quite thick.Like I said before.I can pick up a blitz unit for about 1250 brand new.The asp is 1500 bucks and Most used pfs intercoolers run about 750 or so and 1100 brand new.
With the asp or pfs intercoolers its pretty much a straightforward setup.With the blitz theres the added instalation time and whatnot.
Who here knows any good info on the blitz fmic in comparisson to the asp intercooler that Kevin builds.I mean the piping of the blitz is much shorter than most of the other fmics out there which should in theory reduce the amount of lag gained with a larger intercooler.

rotaryextreme

iTrader: (2)

The stock ECU does not have a fuzzy learning mode that regulates the boost to a preset level. When you change the IC, the duty cycle of the solenoid stays the same and that's why when you use a lower pressure drop IC, you will see increase of boost. Of course, unless the IC you had before sucked big time, you will not detect the difference on the boost gauge.

On the contrary, if you use a boost controller which has fuzzy logic that will change the duty cycle of the solenoid to your preset level, the boost will stay the same regarless of the IC pressure drop.

We are talking about just swapping the IC with the rest of factors remained the same as before. I don't think I ever mentioned getting an IC to jack up the boost. I purely mentioned that you can see pressure drop difference between IC's on a boost gauge if the pressure drop difference is obvious.

Chuck Huang

clayne

First off, the charge pipes into the IC are coming out of the compressor manifold (y-pipe), not the intake pipes. Blitz intake or Scooby Doo intake will not matter.

Rotaries run HOT. Before additional power you should be placing cooling at a higher priority. FMIC location places intake charge cooling (and looks) at a higher priority than the air<->liquid (radiator) cooling system. That's all I'm going to offer on it as it has been debated endlessly in previous threads available in the search engine.

IMO, priorities for modications BEFORE cramming more air into the engine:

1. Outer cooling heat exchangers (radiator).
2. Inner cooling heat exchangers (oil coolers).
3. Flexible engine management (power fc for example).
4. Intercooler.

Ask yourself this: which rotor/housing fails more often, front or rear?

Majority = rear.

Which rotor/housing typically runs hottest?

Rear.

speeddemon7

good point clayne.so then really the best setups for our cars are either chucks v mounts or hmic setups right? and second would probably be the smic's with the ducting and of course a vented hood and a fan.

clayne

The only thing I will answer is this:

Fans won't do much at speed.
Vented hoods have more emphasis on downforce at the front of the car than they do cooling.

clayne

Chuck, the stock ECU will try and control boost using the MAP as input. You don't need any learning or fuzzy logic for that. The stock WG solenoid is not just a brainless switch. It doesn't go from 0% to 100% DC on the solenoid (it's even listed as 40-95% on accel. in the manual). It's the stock wastegate that causes creep.

That being said, I wouldn't use the stock ECU with all bolt-ons and an upgraded IC - CFM is increased, charge is cooler, etc., stock maps ARE brainless about that obviously.

rotaryextreme

iTrader: (2)

Using an stock map signal as input and then varies the solenoid duty cycle accordingly is different from varying the duty cycle based on a preset table.

What you described is a close loop boost control. Most aftermarket boost controller has this function which they call "Fuzzy Logic" but not the stock ECU.

Stock ECU does not run the boost control in closed loop. Otherwise, you will not have any increase of boost when you put on some aftermarket parts such as a lower pressure drop IC or a downpipe, etc. Boost creep happens when the exhaust needs to dumpped out to keep the the boost exceeds the wastegate flow capacity. Putting on a lower pressure drop IC will not make the wastegate flow capcity insufficient to cause boost creep. You get more boost because the solenoid duty cycle didn't change from before.

I don't know if you have Power FC. You can set the duty cycle of the solenoids on it. If you have an upgraded ECU which raises the boost over stock, it's done by changing the solenoid duty cycle, not by inputting a boost value and let the ECU calculate the correct solenoid duty cycle to keep the boost at that value.

Of course the WG solenoid does not just open or close totally. The % is a duty cycle, not how much it opens physically.

Can you tell me how the stock ECU controls boost has anything to do with your not going to use stock ecu for simple bolt on's.

Chuck Huang

speeddemon7

heres the mods im running so far.Intake catback and downpipe with a greddy profec b spec 2.I figure the boost controller will control any excess boost above 10 psi and therefore keeping the air fuel ratio correct.Is this a correct assumption?

rotaryextreme

iTrader: (2)

If you use an aftermarket boost controller and you change anything on your car that will affect boost, you need to readjust the boost controller. Profec B does not have closed loop feedback. It's based on a preset solenoid valve duty cycle. So let's say when your car is completely stock, you hit 10 psi. After you put on the intake, catback, and a downpipe, the boost will increase to about 12 psi without touching the boost controller. If you still want to run 10 psi, you need to readjust the boost controller to reflect the changes you have made on your car.

Keep the a/f ratio correct has nothing to do with the boost controller. Boost controller just controls boost, it does not do anything about your fuel map. What kind of ECU are you using?

Chuck Huang

speeddemon7

no ecu moddifications just yet.What I meant to say that as long as I keep the boost at 10 psi there should be enough fuel for the air right? Provided I reprogram the profec to keep boost at 10 psi.

rotaryextreme

iTrader: (2)

That really depends. The best way to make sure will be using a wideband lambda and check for a/f ratio.

Since stock ECU only sends signal to the injectors based on the MAP sensor signal, it does not know all the other factors that will affect fuel requirement such as turbo condition, exhaust back pressure, compression of the motor, porting, etc.

The best way to make sure will be monitoring it with a wideband lambda.

Chuck Huang

Kevin T. Wyum

Re: boost control table, are you sure IAT isn't part of the table for duty cycle?

speeddemon7

thanx for the hijacked thread fellas.Just kidding.
Anyways.After carefull consideration I am still completely and utterly confused as to which setup im going to go with.But for the price I do like the blitz unit very much.I just dont know how much pressure drop it has across the core.Anyone have this info and how it compares to the asp intercoolers?

clayne

Chuck,

Without having just an aftermarket IC and stock ECU combination (I use a PFC) I cannot 100% tell you that the stock system is closed loop. But I will 99% tell you that it IS regulating duty cycle to WG solenoid based on PRESSURE seen at the map. In fact, about the only thing the PFC (without AVC-R BC setup) is doing is just upping the duty cycle above what a stock ECU would allow; but still using the exact same system the stock ECU uses: MAP + WG solenoid.

Let's consider something else:

Pressure is indirectly proportional to flow. Let's remove the flow restriction (which creates pressure increase pre-IC/loss post-IC) which is an IC w/ 4 psi PD. Assuming the WG can expel all excess exhaust the compressor side is not going to just produce 4 psi additional pressure. In fact, due to pressure being ind. prop. to flow, it won't be resulting in anymore additional pressure as long as the wastegate can dump the additional CFM.

Saying an IC will result in more boost is like saying a downpipe, exhaust, intake, and mid-pipe will produce more boost just because they reduce restriction. In the end, yes it will result in more boost, but ONLY because the stock WG cannot expel the additional CFM gained by the flow mods.

Kevin Wyum?
KevinK2?

Any thoughts?

overkill

I think it's safe to say that there are many, many people that favor the ASP/M2 intercoolers. If you decide to go front mount, there is the probability of modifying your car to make it fit. Also, keep in mind of the damage to the I.C.that WILL occur eventually when stones are directed into the I.C. cores. Just take a look at your oil cooler ! There may be cooling issues as well using a front mount. I have the ASP/M2 Medium, and I think it is great. The only possible replacement I.C. setup would be a v-mount, but I would like to see some data first.

tcb100

Speeddemon, the PFS intercooler is an easy install, looks great and works just fine. I ran 11.6 with the sequential stock twins (80,000 miles) & a cat. No lag, no fitment issues, no battery relocation, no ducting issues, and not too expensive on the used market

What's not to like? I suspect that the differences in the performances of the medium ICs is pretty minor but maybe Kevin can fill us in with some data, if he is still checking this thread.

speeddemon7

thanx tcb100 for the review of the pfs intercooler.Im still thinking everything through.I suppose a used pfs intercooler will probably be best for my setup.I dont want lag or the headache of installing a fmic.I also dont have 2500 bucks for a v mount setup.Even if I did have that kind of cash I would rather swap the car to a 5 speed or have the engine rebuilt.Much more important in my book.

KevinK2

The PFS core was upgraded in 98, for very low pressure drop .... less than 1 psi at about 900 cfm (~600 hp). Tight pipe bends likely add some drop.

Good SMIC. Best to eliminate the connector tube, and open up the filter box for alternate cold air supply. Room for an IC fan too.

cruiser

Actually, I was thinking of plumbing off that hole and bring fresh air to filter through some other passage. I think that hole takes away a decent amount of air that should be going THROUGH the IC. Instead it just turns left towards the filter.