Is anyone intercooling between stages on twins? I have read many posts saying it would be benificial but can't find any post where someone has done it. I was looking at some of the air to water intercoolers, and thought this may be the way to go they are more compact. If i would go this route I would set it up with its own radiator and water pump. Anyway I am just tossing ideas around for now as i don't really have the funds to do this right now. I just like to think of projects to do to the truck. Feel free to throw out your opinions, or experiance.
Joe

 

The best place to take heat out of the air charge is at its hottest point, the biggest differential in temps. It does help and work bewteen stageg or anywhere for that matter, but I suspect you would see a bigger temp drop if post both turbos.

Liquids of course work great.

 

I was throwing around the idea of running a liquid to air intercooler between a set of twins just to see how it would work, the only downside is it would increase turbo laggyness. The next issue is where you put it.

 

What if you wrapped flexible 1/4 to 1/8" copper around the cold pipe in one tight continuous coil between stages and ran ice water through the tube with a small electric 12v pump and a small tank in the bed, maybe setup with a radiator if used on the street. I would think that this would chill the pipe and thus air inside and help out with the temps with negligable difference in spool up.

 

The temp decrease from this wouldn't be enough to justify the hassle of the setup.

I'm not so sure that just because the CAC works best with high temps means that we shouldn't be trying to cool it down before then.

Dropping the temps before the CAC is something I'd consider worthwhile. First, you end up with much lower pressure in the system, because it takes less pressure to deliver the same mass when temps are lower. If you can get the same massflow at 25psi as you were getting at 30, then you've made a substantial improvement.

Lower temps also reduce stress on the top charger a lot. The impeller blades on the top compressor are NOT designed to continuously inhale air at 300-400 degrees. The result of sustained operation at high temp and pressure is wheel fatigue and potential explosion.

Here's another thought: the amount of drive pressure in a system is directly related to how much shaft HP the turbine must try to generate. The more boost the turbo has to make, the more shaft power must be generated, and thus the more drive pressure will be required.

In other words, by trying to make 25psi from the primary nice and cool instead of cranking it up to 30psi or more to get the same amount of mass, we can reduce drive pressure on the hot side and potentially improve power output even with the same amount of oxygen available.

A water-to-air unit between stages would be good at holding a lot of heat, but probably a hassle to package for benefits that aren't staggering. Remember that if you are plumbing engine coolant here, it will actually WARM the inlet air until the discharge temp of the primary is hotter than engine coolant-- which will increase lag and reduce performance overall. Not a good thing, imo.

Even a small air-to-air unit between stages would help the cooling and be easy to package. You'd see benefits just from the convective cooling of the intercooler, though probably quite mild.

For sheer convenience and effectiveness, I suspect a water injection setup into the crosstube might be the way to go. Of course, it's something I'd like to test. For maximum effectiveness, chill your water tank with icewater. Injecting 32º water into a hot flowstream will probably cool it down a good bit.

Justin

 

The CAC in our trucks is actually an after coller because its after the pressure stages. Now what about a true intercooler colling the air befor it goes ito the first turbo. Use the aforementioned ice water but put the intercooler where the air box is.

 

Actually, a true intercooler is BETWEEN stages, as we've discussed here.

There's not much benefit to pre-cooling unpressurized atmospheric air, nor is it practical.

jmo

 

I was actually thinking of using a complete seperate cooling system small radiator and water pump for an air to water setup. The reason i liked the idea of the air to water units is they are more compact and could be mounted anywhere, whereas a air to air unit would have to be mounted somewhere it could get airflow. This is just an idea I am kicking around I saw a small air to water setup used on superchargers and thought it might work, but again this won't be till funds allow. Thanks for the ideas.
Joe

 

If you are considering an isolated water-based coolant system, then I'd say it could be very effective. If using icewater, then you only have so much heat capacity and your system is no longer effective.

Another option is using a closed water system with another air/water heat exchanger mounted in the bed or somewhere else where it can get good airflow. In this setup, you're basically using an air-to-air system with an air/water stage in the middle.

So the thermal energy flow goes like this: hot primary discharge air->air/water HE-> water/air HE-> ambient airflow.

With enough capacity, a system like this could theoretically achieve darn near ambient temps into the secondary turbo.

If you can double the pressure and dump off all the heat rise, then you've really increased the HP! For example, if your normal pressure increase raises temps by 30% and you can dump that heat and get back to initial temp (at higher pressure), then you've just increased your HP support by that same 30%!!

How important is temp drop? If you run your twins with each turbo at 2:1PR (about 15psi boost) and have no cooling at all, let's say you have enogh air for 200hp at low rpm. (intake temps 465°).

That SAME amount of boost with temps down at 100° will now support 340hp with the same EGT!

In other words, achieving "ideal" temp will raise our hp supported number by 85%! This is with the turbos only running at 2:1.


If you crank the boost up higher, running each turbo at 3:1 instead, achieving ideal temps (iow, scrubbing off all the added heat) will give you staggering results. For example, you'd need 110psi of uncooled boost to support what "ideal" boost could support at only 43psi! In HP numbers, that's 770hp with the same cold boost pressures as 342hp of hot boost.

Every degree you can cool the incoming air charge will help everywhere downstream.

 

Its do able as there room for an water to air intercooler between the primary and secondard, just sitting there on top your passager fenderwell. I just don't know what would happen with your truck spool-up, my guess is that its gonna take longer to get everything moving. You boost pressure will be decreased by dropping some of your discharge temperature, mass flow remains constant. Your gains will had from your secondary as it will take less power (drive pressure) to move and compressor the cooler air.
If your careful about your tubing size, it probably be ok and tweak your wasteages some. I think that its worth a try and its cheaper than the spearco that I got.