rx7_turbo2

Yes it might be working great, but with a front mount it could be working alot better and producing even more power.

HWO

lets start with the basic rule of heat

HEAT RISES

Now if you have an intercooler sitting merely a couple of inches) at the largest gap point above a motor which has coolant passing thru it at 90 degrees celcius, oil which is around 130+ degrees celcius and exhuast gas which is well over 500 degrees in temp.

WHERE THE HELL DO YOU THINKALOT OF THE HEAT BEING DISPERSED FROM THE MOTOR IS GOING??????

Straight UP into the INTERCOOLER

vaughnc

RETED,

Hey thanks for chiming in

So in summary:

FMIC:
- If you want 450HP (stage III / IV ugprades)
- If you just like the look (screw the purist crap)

OEM TMIC:
- If you only want stage I and II upgrades (ie maxing the OEM fuel system, larger secondaries) for 260HP

Upgraded TMIC:
- If you want to push no more than 350HP/10-12PSI boost (stage II/III)
- If your a purist and:
- dont' want to cut/mod/move anything (bolt on)
- keep the 50/50 balance

Seems like a plan to me

Wankel7

Let me throw this in What about a water/air IC? I remember reading some old stuff on Cartech. They did all that stuff to a second gen. One which was a water/air IC. They had good results with it. So, get two stock tmic weld them togethere and make it water/air. Assuming you don't buy a kit for your fmic it will a chalenge to fit it. It would be a chalange to fit a water/air IC. So which chalange would one prefer?

James

dcamcoTII

from BNR:
2nd Generation Supercooler-
This intercooler kit is still in its design stage. Development is being made to make the biggest core fit in between the hood and the engine. An accessory kit will be offered along with the Top Mount Intercooler (TMIC) kit. Accessories such as electric cooling fans and a misting kit. These items help alter heat soak while standing still. Price for the TMIC w/ an HKS bypass valve kit, will be around $1000-$1100. Pictures will be available soon!

My question is: would the fans be on the IC, or are they rad fans? And would the misting offset the affects of a poor location??

I don't understand why for the same prics you wouldnt go with a fmic, unless it is an INCERDIBLE amount easier to install. and even still, I can't see why.

dcamcoTII

Unless....
My 87T2 dosen't seem as if there would be anough open area in the front of my car to efficiently accomodate an fmic. Does the size of the mouth make a difference, or is most of the cold air coming up from under the car?

vaughnc

dcamcoTII,

You got it - much easier to install, no modding/cutting/etc.., good for ~350HP/10-12PSI, less turbo lag, etc..

dcamcoTII,

The FMIC will fit, but there is modifying involved and you'd definitly want an upgraded radiator.

-- vaughnc

RETed

That's basically it!



-Ted

RETed

I don't recommend them for daily driver, especially if you're doing long distance driving.

1) Think about it - the cooling liquid is going to slowly heat up to the same temps as the incoming heated intake charge from the turbo - we're talking close to boiling temps here!
2) You're adding more complexity into the system - namely the electric pump that has to circulate the cooling liquid - these things will FAIL.

Air-to-water IC's are mainly for racing with very limited run times.&nbsp These are especially effective on drag cars and road race cars that do short "sprint races".



-Ted

BLUE TII

iTrader: (9)

He probably meant air to liquid to air. These do cool back to ambient air temp after soaking heat from intake charge, but it takes longer than air to air because of the less efficient thermal transfer. But, they will take much longer to rise in temp because of the huge amount of material intake heat is transfering to- IC core in liquid, all the liquid and the liquid's "radiator." A slower reacting, heavier system; however usually considered BETTER for daily driving where periods of on boost are short w/ comparitively long periods between. At least that is my understanding...

vaughnc

I'd rather use a compressed air cooling system (-40 degrees farenheight). When you run out, just go buy another can

Wankel7

Blue TII. Yeah, that is what I ment. The water would soak the heat off the IC. Then the water would go to its own heat exchanger.

James

nathandarby67

People mis-interperet that pressure diagram of the 2nd gen. They see the pressure vectors on top of the hood and think "the hood is on a low pressure area, so no air could get through the hood scoop" You have to realize that the PRESSURE represented by those vectors in the diagram is not the only force controlling the movement of air over the hood. If ther car was sitting still and those forces were working on the air around the car, you would have a valid argument. The vector arrows on that pressure diagram that everyone talks about are a result of laminar air flow going faster over the top of the car than under it. It is exactly like an airplane wing, the air has to flow faster over the top of the car becasue it is rounded, and faster flowing air creates an area of lower pressure. THAT is what is represented by the arrows on the diagram. Do you think if you put a scoop on top of a 747 wing that it wouldnt get any air fed in to it? That is what you are saying when you say no air flows through the TII hood scoop. Just becasue the ambiant pressure at the location of the scoop is lower than atmospheric pressure does not mean that there isnt any air flowing over the car or into the scoop. there is a sheet of laminar flow over the surface of the hood, and this is what the scoop picks up and forces through the intercooler. If you dont believe me go tape some litle 2 inch tufts of yarn all over your hood and drive. This is how they visualized air flow in the days before computers. If anyone sees the yarn pointing out of their intercooler opening please video tape it becasue you have just done the impossible. There is a stream of air moving towards that hood scoop at whatever speed you are driving, and it takes a lot more that a slight negative pressure to not allow it into the scoop. Air has mass and thus has momentum, and that is what pushes the air through the intercooler. Sorry for the long post, but I'm just trying to clear up some misconceptions. And yes, regardless of air flow, a tmic will always heat soak much worse than a fmic.

Wankel7

Well hell yea! That was a good post. I might use that in teaching my private pilots

James

Evil Aviator

Yes, but low-pressure air has less mass, and thus less momentum, as well as less cooling capability. Also, if you look at how close the stock TMIC is to the engine, you will notice that the air doesn't have much room to flow past the engine block, which I'm sure greatly hinders the airflow through the core. The small amount of hot, expanded air which does make it through the core must exit through the bottom of the TMIC, flowing directly against gravity, once again hindering it's flow. I think that someone else also pointed out the heat radiation problem from the engine, so basically the TMIC has a disadvantage in all three forms of heat transfer - conduction, convection, and radiation. Yes, the stock TMIC is fine for a lot of cases, but I see no point in spending 1K+ on an aftermarket TMIC.

The Spearco 2-248 FMIC retails for $990 less plumbing, and at 390cfm and 20psi boost, the core experiences about 0.5psi pressure drop and 88% efficiency with a 10mph ambient face side velocity. How does the BNR TMIC core compare to this?

I'm just thinking out loud here, but why doesn't BNR make something useful, such as a TII plumbing kit for the 2-248?

I hope that you also teach them about air density and its relationship to performance. Just because you have air velocity over your wings doesn't mean that you can fly.

Megaspeed7

I'll toss my .02 in as well.

Great response from a well-educated point of view, I couldn't have said it better myself. Kudos. I think more people should be required to take fluid mechanics, its quite interesting as well as applicable in this field.

I presonally like FMIC kits. The new Greddy V spec is undisputably the best intercooler kit I have ever seen for an RX-7. It took me close to 5 hours to make my intake plenum (on throttle body) to route my piping the same way, and not to mention prices on a core alone of that size are in the 700.00 - 800.00 range. I just think it is an unbeatable price for an intercooler that will flow 500 hp with ease and take little to no fabrication to bolt on.

As far as TIMC kits, I think they will work great if you put a fan on top of it with correct ducting under it. Which is what Bryan is trying to tell you guys. Seems that the main argument is "When I sit still, the hot air is gonna come up from the motor heat soak my intercooler" which indeed will happen if all the air sits still. Now if a fan were installed up top and was constantly sucking cool air from outside and blowing through the intercooler, then none of this hot air would be able to get to the core to heat soak now would it? I would also instill some insualtion below to reduce convection and conduction through the cooler. Thus the only true disadvantages of a TMIC is that the capacity is limited to spacing under the hood (pretty limited). One MAIN advantage of a TMIC is that its REALLY EASY to just stick a bag of ice on it while waiting your run at the track. It makes one HELL of a difference to start out with a freezing intercooler.

Along the horizontal mount note, I also have done some research on this and if you strategically place one of the hood scoops from this page ( http://www.roadraceengineering.com/rock/tunerpods.htm ) you could run a wicked intercooler over the top of the fan shroud while looking "Straight Pimp" with your carbon fiber as well. Have any of you guys seen the Supra intercooler in the intro of GT3 for PS2?? Hmm...racecar with a horizontal mount?? I would say lose the plastic fan shroud, angle the radiator a little, remake a fan shroud to match the new position, then make intercooler duting, and install an intercooler fan. it would neat to have (unique) but just a little less piping as a FMIC setup. Then again guys, go buy the Greddy kit, none of them are cheap. And that one rocks the house. Just will it fit an 87-88????

Later,
Patrick

nathandarby67

If the air was flowing out the BOTTOM of the TMIC, would it not be flowing with gravity? Last time I checked, gravity pulls things down. Like down through a TMIC and out the bottom

Don't get me wrong here, I wasn' saying that a TMIC is better or even equal to a FMIC in terms of cooling air flowing through it, I was just correcting a few people after several posts on this thread incorrectly suggested that little or no air will flow through the hood scoop on a TII just becasue it is in an area of low pressure. I think people look at that force diagram of the airflow over an FC and assume since the vector arrows are pointing up and away from the car that that is the direction air flows. The arrows are vector symbols showing the FORCE PRODUCED ON THE SURFACE OF THE CAR by the moving air flowing over it. the force is pulling against the hood of the car in the direction of the arrows, the arrows thus have NOTHING to do with the direction of airflow over the car or through the hood scoop. It can just be surmised that since there is a force pulling up on the car that it must be an area of low pressure since that is how lift is produced in the first place, but this DOES NOT mean that no air is flowing through the hood scoop.

BLUE TII

iTrader: (9)

Thanks for posting that link Megaspeed7! I was wondering how I was going to vent the horizontal IC I want to run. That will CF vent will look great right behind the headlight cut outs on my spare NA hood.

NZConvertible

Ted, I have to disagree with you on water-to-air intercoolers. It's the thermal properties of water that make this system so much more suited to a street car than a race car. The water should never be even near boiling, because water can absorb so much more heat than air hold per kg. You're right that they're more complex than air-to-air, but they're pretty simple really. A good quality pump (and why would you use anything else?) should run for thousands of hours quite happily. Long distance driving would have no effect on a water-to-air system because so little boost is used. Several manufacturers have fitted them, so they can't have had an issue with long distances. Race cars running at constant high speeds are more suited to air-to-air intercoolers, simply because they're more able to take advantage of the "free" cooling provided by high speed airflow through the core. Not so for the street car about to accelerate from the lights.
Here's an extract from the article I linked to earlier that explain it further:

"In my high-boost Mira Turbo I ran a water/air intercooling system. The water/air heat exchanger comprised a highly modified ex-boat multi-tube copper heat exchanger, with a few litres of water in it. An electric pump circulated the water through a separate front-mounted cooling core. Intake air temp was measured using a thermistor and a dedicated LCD fast-response meter.
In normal point-and-squirt urban driving, the intake air temp remained the same with the intercooler pump switched either on or off! Why? Because when the car was on boost, the heat was being dumped into the copper-tube-and-water heatsink, and when the car was off-boost, this heat was fed back into the (now cooler) intake air flow. Of course, if I was climbing a long hill (ie on boost for perhaps more than 15 seconds) the pump needed to be operating to give the lowest intake air temps. But even in that tiny car, 15 seconds of constant full boost would achieve over 160 km/h from a standstill...
The latter shows why water/air intercooling in road cars is so successful - but why most race cars use air/air intercooling. Water has a very high thermal mass, so easily absorbing the temp spikes caused by a road car's on/off boost driving. However, race-style boost (say on full boost for 70 per cent of the time) means that the system has to start working far more as a real-time heat transfer mechanism - which is best done by very large air/air intercoolers.
The key point is that typical road car air/air and water/air intercooling systems act as heat sinks during boost periods at least as much as they act as heat transfer mechanisms."

Evil Aviator

Sorry for the advanced thermodynamics. I know that you normally think of gravity's effect in the positive vector (down), but due to Newton's 3rd Law of Motion, there is also a negative vector for less-dense displaced mass. Let me try to explain. Gravity pulls denser mass towards the earth, which forces the less dense matter up away from the earth. The hotter, less dense exit air from the intercooler therefore will naturally want to rise (hot air rises - basic science) to seek equalibrium with the less dense air in the upper atmosphere. Since the air exits from the bottom of the TMIC, it is forced in the exact opposite direction of its natural convective flow which is the negative (up) vector. This is why it flows against gravity. Were there no gravity, this would not be a factor.

You are basically correct on the vectors in the RX-7 flow diagram. Low pressure does not necessarily indicate reversed flow or a complete absense of air.

RETed

I'm not going to quote, because I see this heading no where...

An air-water-air interchanger is stupid.&nbsp An air-air does the same thing minus the additional complexity of plumbing and a pump.&nbsp My K.I.S.S. principle keeps me away from such a system...

Yes, you're correct, pressure is not the same as flow.&nbsp Technically, that's true.&nbsp My point was the high pressure area in the front bumper was the highest pressure (and flowing) area on the car.&nbsp It's obvious from the pic (and just plain common sense) that the front bumper is the best place to put a heat exchanger.

I still stand by my experience with air-air intercoolers up front.&nbsp Water (or any liquid) is going to absorb heat (specific heat?&nbsp heat capacity?) unless the airflow is cooler than the water itself - at this point the heat exchange is reversed.&nbsp You might get superior cooling (due to superior heat exchange) up to a point, but once you hit a certain point, the water ends up as a heater.&nbsp If you manage to drop the intake charge under the temp of the air-water IC, then you get the reverse heat exchanged mentioned above.&nbsp Quite a round-about way of doing intercooling - an air-air IC is a more direct way of intercooling, IMO...



-Ted

NZConvertible

What you've described is NOT typical water-to-air IC behavior, it's what would happen in a poorly designed and built one. If the front-mounted condenser is sized correctly, it'll have no trouble removing all the heat from the core. Water can absorb four times as much heat energy that air for the same rise in temp. This is what makes it ideal as a heat transfer medium. It also means the core can be much smaller for the same cooling capacity and be kept in the engine bay for shorter and more direct pipe routes. Both systems have their pros and cons, but a properly designed water-to-air IC will have advantages over air-to-air on a street car. No offense, but calling it "stupid" is being a bit pig headed!

nathandarby67

Yeah, I agree with you on this one. I didn't think about the effect of convection becasue of the air being heated after passing through the intercooler. It's bee na few years since I had any thermo classes and I sure don't use it on a day to day basis anymore! Anyway, I guess your wording threw me off. Even though gravity causes convection currents, keep in mind that it is still pulling downward on that less dense, hot air that just came through the intercooler. It is just pulling down on it to a lesser extent than the cooler dense air around it, which is what casues convection currents, which wants to force that air upwards.

Lets consider a single molecule of air that has just passed through the intercooler. At a given instant in time, there are several forces acting on it. The sum of these forces determines which way it will flow. You have 2 downward force vectors acting on it. One from the force of the air being pushed through the hood scoop (determined by road speed), and one from the force of gravity on that molecule. There is one upward force acting on it, the force of convection we have been discussing. If I am leaving any forces out here, fill me in, but these are all I can think of. In a nutshell, while the car is moving down the road, the force from the air being pushed through the scoop is much stronger, so the air flows down through the intercooler, even if it is being resisted by friction and the convection forces. While the car is sitting, the convection takes over and HOT air goes back up through the intercooler. (unless maybe there's a really strong wind blowing through the scoop!) Anyway, I hope this covers it.

nathandarby67

I totally agree with you on this one, on a basis of airflow and cooling capacity, the front bumper if by far the best place to put it. But if Mazda put the intercooler up front, then us TII guys wouldn't get to have cool hood scoops on our cars!!

rx7_turbo2

Lets see if I can't sum this up.

Yada yada yada...TMIC works decent for stock or slightly above stock applications.

Yada yada yada...FMIC is tried, tested, and proven, and the ideal situation.

Yada yada yada...Upgraded TMIC is good only if the price is significantly less than a FMIC.

Yada yada yada...If you're running big boost a nice big FMIC is the way to go.

I don't even want to get into the air-water, water-air, glycol injection jazz.