Twins guys-- why no intercooling between stages?

[Hohn]

I don't think it would be that hard to do. PLumbing the output of the large charger through an CAC before it hit the small turbo should be doable, right?

Heck, even making the plumbing out of copper would be helpful for dumping heat, I'd think!

There HAVE to be appreciable gains to be had in cooling the air between stages.

If an intercooler is a good idea with a small stock turbo and moderate boost, then the benefits would be multiplied imo with cooling before and after the small charger.


Whose done it? Why isn't it done more often? There's no excuse imo for not doing it, and I consider this an essential part of doing twins "right".

Anyone have something to add?

 

[Partyat33]

Not the expert but, the air you get from the Big Turbo is pretty cold already. So I don't think there is that much to gain. Have not measured it yet, but someday I will. Also i think the plumbing would be a nightmare !

 

[Sled Puller]

Cost and effort to do it right I suppose.

 

[swankmetal]

good q, hohn. that's one of the projects on the top of my list. i've got a two channel intake temp gauge in route. once that installed and some good baseline #'s have been taken down, i'm going to put a small ic between the turbos and see what happens. this is the only pic of an underhood set up i've seen. quite a bit more than what i'm thinking (i'm not going to have TWO ex. gates). somebody over on dtr added a full size ic in a place i would put a skid plate a while ago. don't remember hearing any updates lately.



i do KNOW that it will be a good thing too. sometimes the piping is so hot that even i can't hold onto them. i want to add some ic chillers as well. keep the metal cool, and the air will follow, right?



dave

 

[Diesel Freak]

There is not enough room for a air to air cooler... . and then you would need to put a scoop on the hood to direct air into it.



Best bet would be a water to air cooler with the water heat exchanger mounted behind the bumer in place of the plastic pieces the fog lights sit in.

 

[Diesel Freak]

Or you gould ditch the stock CAC for a bigger better badder custom built CAC... . but expect to pay close to $1500 for a decent one.

 

[Jim Fulmer]

Not the expert but, the air you get from the Big Turbo is pretty cold already.



It's actually quite hot, it's not unusual to see temps to 400 degrees in the cold pipe.



I have a plan for the project, it intails an intercooler that the same place as that mess in the pic that didn't work, then have a holding tank in the bed with a scirocco radiator mounted under the bed and a continuous running pump. When you were at the track or dyno, drain water off to make room for ice then your set.



Problem is you have to run water through it all the time so it doesn't make since on a daily driver, that's why I scrapped the idea.



Jim

 

[swankmetal]

Best bet would be a water to air cooler with the water heat exchanger mounted behind the bumer in place of the plastic pieces the fog lights sit in.

is that what's in the pic? i've looked, but can't really tell.

 

[Diesel Freak]

it looks that way... or they could just be ice boxes where you just replace the ice and water after each run down the track.

 

[swankmetal]

jim and cliff, have you seen any cac chillers on trucks? the water sprayer types? seems to me that they'd work well on anything over 212*, no?

 

[Diesel Freak]

actually they would work well on anything over ambient.

 

[metal tech]

Jim is right. An Air-Water intercooler is great for short duration use, but the added tank,plumbing, and heat exchanger makes it impracticle for daily use. This is why you rarely see endurance turbo'd race cars with Air-Water intercoolers. The intercoolers in that pic are Air-Water versions, you can barely make out the water connections on the back one. Just a thought, DEI makes a "bulb" that goes into an intake tube that is chilled with CO2. The bulb chills the air as it passes by. This is also a short duration solution.

 

[Partyat33]

Jim, I will take you word on it being hot. I have yet to put a gauge on it. I will do it pretty soon. I still think its a lot cooler than you get with pushing a single beyond its MAP !

 

[Hohn]

I still think its a lot cooler than you get with pushing a single beyond its MAP !

True, but you take air at up to 400° in the cold pipe THEN compress it another 3 times or so?

You can easily have discharge temps up to 900° in the hat (without any CAC at all), and THIS is why it's useful to have TWO CACs.

900° just simply overwhelms the stock cooler, and I'd suspect most aftermarket coolers. They just aren't designed to handle that. Dividing the workload up between stages is more efficient, just like twin turbos are.


I don't consider air-water to be a practical setup at all for a street truck. A slick air-water setup like Banks used on the Sidewinder is sweet, but impractical.


What I was conceiving was actually something that was air-air based. I was thinking that you could use copper piping, and plumb a loop of it into the intake tract.

For example, air comes out of the big charger and enters a 3" copper pipe that would tuck under the truck, loop to the back, and then come back to the hood and into the small charger.

I'd think that the pressure loss from the extra plumbing would be more than offset by the cooling effect of the the copper piping. You could increase the cooling efficiency of the piping by using a bunch of those "cool collar" oil filter cooling gimmicks, or something along those lines.


Or, you could just plumb in a small air/air cooler back by the spare tire locations, and plumb it with copper-- this could get temps down substantially between stages.


Before you dismiss the idea of a "loop cooler" that's just a section of thermally conductive tubing, it's used quite a bit-- often as a transmission cooler or PS fluid cooler-- by the OEMs.

Moreover, the ductility of copper piping would make fabrication a snap. Heat it, bend it, then braze your connections on. Sounds simple enough-- in THEORY anyway!


There's a LOT to be gained imo from an intermediate CAC in a twins setup.

 

[nickleinonen]

For example, air comes out of the big charger and enters a 3" copper pipe that would tuck under the truck, loop to the back, and then come back to the hood and into the small charger.

that would cool the air, but how much extra lag would that net you???

 

[JasonCzerak]

that would cool the air, but how much extra lag would that net you???

Exactly.



Why not just 2 or 4 water jets between stages. And a nice tank in the back. And one HUGE IC to finish things off. This is a longer duration solution the rest, but not a long long term deal.

 

[JasonCzerak]

Exactly.



Why not just 2 or 4 water jets between stages. And a nice tank in the back. And one HUGE IC to finish things off. This is a longer duration solution the rest, but not a long long term deal.

Better yet. There is plenty of room under the hood if you put a Subaru WRX STI version of a scoop there (big one!). That line of cars dose use that scoop for the IC (as does the mini copper-S). This would make piping short for the first IC. Keep the second IC in the stock location.



Short of comming up with a mount and hood design, this should be easy to pipe.

 

[RustyJC]

From a theoretical perspective, interstage cooling is certainly desirable. We utilize it on our plant air multistage centrifugal compressors - the air is cooled after each stage of compression. Interstage cooling improves air density going into the next stage and, thus, the compressor efficiency of that next stage. Challenges in automotive applications are space, complexity, cost and additional piping volume (lag).



Rusty

 

[Diesel Freak]

The WRX scoop idea would be the best bet. Just replace the standard cold pipe with a custom built air to air intercooler.

 

[Diesel Freak]

I'm not a huge fan of injecting water into the intake stream to cool things off. While it does raise the VE of the engine, it does nothing to promote a cleaner burn, and with the way the EPA is heading, we need to ditch the smoke.



Interstage cooling could bump charge density quite a bit without having to raise boost pressure. Having air going into the second stage <150F would be sweeet... . and obtainable without the use of water injection