KOU Motorsports FWD Update Options

[KOU In3]

You need a heat exchanger for the a2w to work correctly on the street.

That's what gives it a consistent temprature below ambiant temp and what makes it better than an a2a ic.

Actually a heat exchanger will never get you below ambient. The best it could do would be to come very close to ambient temps while having the more efficient medium (water) for heat transfer. Although you're right that the heat exchanger (possibly an extra oil cooler) will prevent heat soaking or boiling the water.

Adding ice water or some other supercooled mixture (planned) will be neccessary to go below ambient.

[natedogg]

We have kicked around the idea of giving the intercooler it's own radiator, and have talked about various possible mixtures to achieve the coldest intake air.

Sorry if this sounds kind of blunt but isn't that essential to any a2w intercooler? Unless you want to keep draining and refilling a tank full of ice water. Which I suppose is feasible for the strip, but not very practical or consistent for the street.

And as far as badbu's comment that a2w is 'better' than an a2a on the street, I beg to differ. I can't remember what mag I was reading, but they did a study on this very subject. They found that even with a pull-through fan for the heat exchanger, the a2w ended up heat soaking the air during prolonged traffic driving. The a2w is perfect and undoubtedly better than the a2a for what J plans to do with it at the strip, but I wouldn't be so quick to say its better for driving on the street, especially when sitting in traffic is an inevitability as it is in Peoria these days.

[natedogg]

You need a heat exchanger for the a2w to work correctly on the street.

That's what gives it a consistent temprature below ambiant temp and what makes it better than an a2a ic.

Actually a heat exchanger will never get you below ambient. The best it could do would be to come very close to ambient temps while having the more efficient medium (water) for heat transfer. Although you're right that the heat exchanger (possibly an extra oil cooler) will prevent heat soaking or boiling the water.

Adding ice water or some other supercooled mixture (planned) will be neccessary to go below ambient.

Ahh, you posted while I was typing.

That's kind of what I was thinking you guys were aiming for, for drag strip competition. Definitely makes sense in that situation.

[KOU In3]

It's looking like the AC condensor can be modified to suit this purpose pretty well actually. We'll see after a few minutes with the bandsaw on a spare one.

I don't think sitting in traffic will heat soak the a2W much more than say a topmount on the Subies as the water won't really go above underhood (not engine) temps. A few minutes at 30mph driving with air moving through a heat exhanger should cure the heat soak issue.

You're right though, the real reason for the a2w was for the option of a supercooled intake charge at the strip. I'm tempted to start a separate thread on heat exchange properties vs. low temp on the various possible recipes there.

[badbu68]

I don't trust magazine reports very much but in response without seeing the article, you have to properly size the heat exchanger, water pump, and resevoir so that you're transfering enough heat, just like a radiator has to be properly sized.

[awd4kicks]

This may be obvious but I haven't seen it stated yet.

The a2w intercooler/tank set up will mearly average out the temperatures between the hot IC and the liquid tank untill they are at nearly the same temperature. This can very well be over ambient temperature with the high temps of the IC cooked by a 20+psi 14b. Obviously ice or some other supercooler will increase the differences between the two heat extremes slowing down the averaging of tempeartures, but the long term dynamic is still the same. An additional heat exchanger will help this situation but I think it will need good surface area to keep the tank cool while the IC is pumping hot water into it. I know the other day after about 20 minutes of semi regular driving the tank ended up with roughly 90 degree water in it...very warm to the touch.

This all has to do more with longer term street driving rather then all out drag racing. Ice in the tank will last through a couple 1/4 mile passes bringing the IC temps well below ambient giving the 14b the best chance it will ever have to produce power above it's efficiency range. I think the potential here is enormous for the strip.

[natedogg]

I agree. Even with a near perfect heat exchanger, on a 90 degree day the water is never going to get below 90 degrees (most likely even hotter) assuming no ice or other chilled substance. This assumes there is always air running across it as well. With no air running across it the heat exchanger will be far less efficient. Not that it would be any less efficient than an a2a. I'm just thinking out loud.

If you guys are planning on using a pump and a heat exchanger, have you given thought to water flow through the IC fins. Cavitation would be unforunate.

If you wanted to get really fancy with it you could even make it thermostatically controlled. Help keep the water in the heat exchanger longer for better efficiency.

[KOU In3]

  With no air running across it the heat exchanger will be far less efficient.  Not that it would be any less efficient than an a2a.  I'm just thinking out loud.

The other thing to think about though is that even at suboptimal temperatures, the a2w is going to be more efficient at bringing the temp of the intake charge as close to that of the IC as possible.

An example with some rough estimated numbers:

A2A numbers:
90 degree day. Turbo inlet temp ~110 (underhood). Turbo outlet temp. ~190 (pre-intercooler). Intercooler temp ~100 degrees (quality FMIC).

Post IC temp ~120 degrees (A quality FMIC is supposed to get within 20 degrees of ambient when cooling the intake charge).

Net change: 90 degree day. 120 degree intake charge temp.


A2W numbers on street with heat exchanger:
Same 90 degree day. Same 110degree turbo inlet temp. Same 190 degree turbo outlet temp. Intercooler temp same 100 degrees as the FMIC due to proximaty to the engine bay (heat exchanger in similair location as the FMIC).

The a2w offers a better medium for heat transfer though. Intake charge temp should be closer to 105 degrees

Difference on a street set-up would be 120 degree inlet temp vs. 105 degree intake temps with the a2w.

My understanding is that the a2w is able to take a lot more heat out of the intake charge and bring it very close the temperature of the water inside of it whereas the a2w at its best will only be able to bring you to within 20degrees of the IC temperature.

Overall, it would be a much more scientific arguement with 6 heat probe set-up to verify but...

[KOU In3]

If you guys are planning on using a pump and a heat exchanger, have you given thought to water flow through the IC fins. Cavitation would be unforunate.

There's already a pretty large pump in place that moves water across the fins. Boiling the entire 3 gal sump at this point seems a bit unlikely with the relatively small volume of air that the 14b is capable of moving (albeit a very hot small volume).

The pump should flow plenty where cavitation at just the IC is not likely. The entire sump would have to be on boil along with the volume in the sump.

Overall, the way it sits in place now is more of a stepping stone to its future street tune. It allows J to continue to drive the car daily while minimizing downtime for the next phase of the install. In its present state it does allow for drag runs. Just hobbled for street purposes pending the next step.

[JMoushon]

Thank you Travis for making that clarification. I never intended to leave it as it sits, but before I had the recirculating sump, I was basically running no intercooler at all.

It is the way it is because I needed to get someting put together that would allow me to put the car on the street, albeit if I want to push the car I have a roughly 20 minute window of opportunity.

The next phase is coming this weekend, I will update as soon as it's functional.

[The Iron Goat]

It's looking like the AC condensor can be modified to suit this purpose pretty well actually. We'll see after a few minutes with the bandsaw on a spare one.

I can't tell you the number of times that I've wondered if the AC could be used for chilling intake charges or even fuel rails on a car. In J's application, would you be using it to chill the a2w resevior? I think I missed that in the conversation.

[KOU In3]

I can't tell you the number of times that I've wondered if the AC could be used for chilling intake charges or even fuel rails on a car. In J's application, would you be using it to chill the a2w resevior? I think I missed that in the conversation.

Yes, we're thinking of using it to cool the water from the resevoir.

As to cooling actual intake charges, the in/outs as well as it's narrowness would make it horribly restrictive for good airflow. I'm hoping though to make that very restriction work for us by keeping the water in the condenser for long enough to cool it down effectively.

We'll see if it actually pans out that way though.

[wortdog]

My understanding is that the a2w is able to take a lot more heat out of the intake charge and bring it very close the temperature of the water inside of it whereas the a2w at its best will only be able to bring you to within 20degrees of the IC temperature.

Actually, the water can only take heat out of the intercooler, not directly from the air. You are still limited by the relatively poor heat conductivity between the air and the intercooler.

A good air to air intercooler, like the one on Frank, partially sits at ambient temperature all the time(1/2 to 1/4 of it at least). Part of it is also much warmer than ambient, so you have a gradient of cooling capability as the air flows through it. Its not uncommon to see only a 5-10 degree difference between IC outlet temps and ambient with a really good air to air, due to the large amount of surface area for both cooling interfaces(ambient air <-- intercooler, intercooler <-- charge air).

Most w2a have less internal surface area for the intercooler/charge air interface. I'd guess the a2a core on Frank has at least 6 times the internal area of the a2w core we're talking about. If only a 1/4 of the a2a core is at ambient temp still, that's still 1.5 times greater area than the a2w cooler, plus the other 3/4 of the a2a has already cooled the charge down quite a bit. The a2w can only outperform the a2a if you can get the IC temp well below ambient.

[The Iron Goat]

I can't tell you the number of times that I've wondered if the AC could be used for chilling intake charges or even fuel rails on a car.  In J's application, would you be using it to chill the a2w resevior?  I think I missed that in the conversation.

Yes, we're thinking of using it to cool the water from the resevoir.

As to cooling actual intake charges, the in/outs as well as it's narrowness would make it horribly restrictive for good airflow. I'm hoping though to make that very restriction work for us by keeping the water in the condenser for long enough to cool it down effectively.

We'll see if it actually pans out that way though.

Sounds awesome. And just to clarify, I didn't meat to run the intake charge through the condensor, but rather develop some sort of really whacked-out custom condensor that could serve as a "sleeve" around one of the IC pipes, or the fuel rail. Again, just a really drawn-out daydream I've been having. I think it would work best in a fuel cooling scenario similar to what you guys will be running with that resevoir.

[KOU In3]

You are still limited by the relatively poor heat conductivity between the air and the intercooler.


Most w2a have less internal surface area for the intercooler/charge air interface.

These were the two parts where you lost me a bit. My understanding has always been that there is a very good heat conductivity between the air (charge air) and the intercooler due the the fins and tubes being immersed in water.

I'd been under the impression that this was why the a2w was effective even with the relatively small core size.




note: Reading the part of my post you quoted I had at least one typo where a2w should have read a2a. Sorry for the confusion there.

[natedogg]

If you guys are planning on using a pump and a heat exchanger, have you given thought to water flow through the IC fins.  Cavitation would be unforunate. 

There's already a pretty large pump in place that moves water across the fins. Boiling the entire 3 gal sump at this point seems a bit unlikely with the relatively small volume of air that the 14b is capable of moving (albeit a very hot small volume).

The pump should flow plenty where cavitation at just the IC is not likely. The entire sump would have to be on boil along with the volume in the sump.

Overall, the way it sits in place now is more of a stepping stone to its future street tune. It allows J to continue to drive the car daily while minimizing downtime for the next phase of the install. In its present state it does allow for drag runs. Just hobbled for street purposes pending the next step.

My comment was aimed at cavitation inside the tank where the IC sits due to direction of water flow rather than pump capability. If the water is not flowing the through the fins but rather across them, the water between the fins will cavitate and stay just as hot as the rest of the intercooler. Keep in mind I haven't actually seen this setup yet, so I don't know how the tank and IC are designed and how they integrate with each other.

I might have an easier time with those estimated numbers if there were some equations to back them up theoretically. I might have to break out the old thermodynamics book when I get home. To be frank I don't think we know for sure that there will be a 15 degree difference in charge air between an a2a and a2w setup all else being equal. There may be no difference at all. Similar to what Wort was saying, even though you are giving the a2w setup a medium to transfer heat through, you are still just trying to bring it as close to ambient as you can. A good a2a can do that for you also.

The benefits that I do see are the ability to pack the a2w tank with ice water and the decreased pressure drop that comes from having less piping and a smaller core. These will undoubtedly help at the drag strip.

[JMoushon]

Update.


Went out to KOU last Friday, did some regular shop work, and decided we had some time to work on te "fun cars" (our personal/shop race cars). Christian pulls in the Spyrocket, I pull in the FWD. The goal for my car was originally high/mid 12s, with no more that bolt-ons and maybe an Evo3 16g. Riiiiiight. That idea is now nothing but something to look back on and laugh at. The goal Christian has for te Spyrocket (currently) is to make it a well-rounded auto-x performer. So we pull the cars in and "presto-chango" we drive them back out. Wait a tick, something feels different. Christian is complaining about top-end, and I'm trying to figure out why I can't get boost until about 3500. Oh, that's right, we switched turbos. Nevermind. So the Spyrocket is now ported 14b-powered, and the FWD is 20g/HKS wg powered. Nice.

As far as project completion is concerned, we still have a long way to go, but for now, the set-up is nice. Spools well with high compression, pulls hard, sounds insane. We will put a clutch in it this week, as where the stocker was getting weak on the 14b, it is now about useless for anything above 15psi.

Unfortunately, I'm officially out of excuses. The 14b was a built in excuse, that is now gone. As soon as we install a clutch that can hold the powAr, I have no reason left not to run good times. Dammit.

So the basic set-up is this...

BR20G (TD06)
HKS Gate
Ported and Extrude Honed 2g Manifold
3" to 3.5" TBE
A/W IC, 3" in/out
Denso 660s
MAF-T
Eprom/Wort chip
Kris144 Intake
KOU IC piping

There is more, but I think you get the idea. We were going for high 12s. I think we may be there...

[xian 1g]

swap the the clutch, get rid of the weight, no more excuses

[JMoushon]

Why do I speak?






Nice sig, Christian..... Mental note.... no more hanging out in CU...

[badbu68]

Have you got a heat exchanger yet? I'd either use a large tranny cooler like one from B&M or a motorcycle radiator.