My thoughts, looking for more experienced folks to comment. This could be used as a basic guide for folks & since the E55's biggest performance obstacle is controlling IAT's I figured it was worth a conversation:

1. Killer chiller (trunk or underhood tank) ~$??
2. Heat Exchanger ~$400
3. Split cooling (trunk tank) ~$??
4. Split cooling (underhood tank) ~$125
5. Methanol / water injection

Of course a pump is paramount but let's assume we have a fully operational one & does anyone have any measured results?

Not sure about the following:

1. Headers (they reduced IAT's a fair bit in other applications)
2. Porting supercharger (in Grand Prix's that used to net huge temp reductions!)
3. Bigger rad options?

You will need a tank with the KC, be it under hood tank or trunk tank.

updated, thanks

Constant on intercooler pump doesn't hurt

Not that I've ever measured, but coolant carryover between the two systems is minimal in my estimation. Therefore, a split system with only the little reservoir in the engine bay is probably a waste of time and money.
A split system with enhanced capacity, that's probably worth it. (either through big tank, or multiple radiators.)

You forgot Methanol (or water) injection.

And big money: custom (relocated) intercoolers

Water injection works. IMO with KC works best since you already start will low iats.

Have to agree here. It's no contest what water or meth injection will do to IATS.

1. Water or meth injections
2. The rest

How does water injection work? Does water get sprayed into the face of the HE?

Water/meth
KC
Trunk tank

That will solve and keep IATs in check.

No way!! A split system right off the bat drops temps down at least 30 deg.that I saw in my own. If your engine is running at 190 the inter cooler is already at that temperature so seperation from all that heat is a great plus right from the start even with a small tank....no?

If your (intercooler) pump is not running, then there is negligible crossover between the two systems. If the pump is always on, there will be some spillage, but there is no way your intercooler is always running at engine coolant temp. Not even close.
If you look at how the two systems are connected, then you'll understand.

Check out the highly detailed schematic I attached.
The top circle represents your engine cooling, with the square being a pump.
The bottom circle is your intercooling system.

I find water/meth injection to also carry a big risk factor. If they fail, it usually ends up pretty bad. Overall, I agree they do a fantastic job of reducing IAT's & increasing power by allowing more timing/boost.

^ That's if you tune for it and don't run failsafes.

If you want cooling options then nitrous should also be on the list lol

With nitrous, do you need to tune for it? Or, can you use it like water/meth...just for cooling?

If you use it to cool your heat exchanger with a nitrous ring no but as soon as you add into the motor yes it must be tuned for it

Depends on the shot. You may want to reduce timing. Wet shot you add fuel with nitrous and you control the ratio so you are determining afr

No, water is actually sprayed with the combustion. It goes inside the cylinder.

Weird. I thought water didn't compress?

I guess this runs a fine line between functioning well and hydrolock?

No , the minute amount of water sprayed evaporates instantly and actually steam cleans the internals as well.

Interesting

On my old car (3rd Gen rx7), I used water injection with great success... I used a mechanical pre-turbo injection kit. I haven't looked into whether it would work for a SC, but I don't see why not. In fact, it may work better since there's claims of pre-turbo WI damaging the compressor wheel... On a 55 SC, I wouldn't think that's an issue.

You can spray before the blower but will not make a huge difference. Post ic is the best place

I agree, the only benefit pre-blower is that you don't need a pump. The SC pressure is used to spray the water.

Not worth the headache, post ic is easier

Centerline (who has one of the faster 113K's) suggested an "always on" I/C pump set-up in this thread. Makes sense to me but no one seems to talk about this. Does anyone know anything about this?

PS, I am heading down the meth injection path this will just be some "icing on the cake".