The Lotus Cars Community banner
1 - 10 of 10 Posts

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
The other thing that you guys are forgetting is the cooler design and charge air pressure drop.

The RLS cooler is a bar-plate cooler which are known to be extremely durable (most durable heat exchanger design to my knowledge) and have increased heat transfer over the tube & insert cooler design that the stock cooler has (at equal fin densities and sizes) due to increased surface area. The bar plate should also have less charge air pressure drop because there is more internal airflow area, meaning there will be a power increase from that alone. The RLS cooler is also larger than the stock cooler meaning more heat transfer area thus increased efficiency.

However, you guys are right on the thermal side that the bar-plate cooler is harder to cool off once hot because there is more thermal mass, but I feel the pressure drop decrease and increased efficiency ultimately improves performance over the stock IC.

The only time the RLS IC would be worse is if it gets so hot, that it can never be cooled down, yet the stock cooler can somehow be cooled...
 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
You guys are underestimating the bar and plate vs tube and fin design... Looks like all the cores tested in the referenced post were tube and fin.

Another thing, we all determined the Forged IC was a boat anchor like years ago. Might as well run stock Exige S part if you're thinking of the Forged IC (and it's like impossible to make power on the Exige S core). I have not seen the PA unit, but assumed the same about it as the forged based on its construction...

That said, the bar and plate unit that RLS sells is made by Bell. For those that don't know, bell (owned by Gerhard who designed coolers for F1 among ALMS and others. Quite the pedigree really) invested in the tools to make their own cores and not just make something work from china, or existing cores from the usual suppliers, etc like the others do.... the tube and fin design is FAR FAR inferior to the bar and plate (which the RLS cooler has for core) for cooling the charge.

-Phil
+1

Exactly what I was saying before. The only reason you don't see more bar plate coolers in the automotive world is because they are expensive to produce, unlike the tube-fin designs. Otherwise the bar-plate coolers will outperform a similarly sized cooler any day!
 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
INTERCOOLERS

You guys seem to be missing the point, no one is saying aftermarket intercoolers are rubbish, in fact it is the opposite. They maybe the gold standard, but without enough air ("air to air" heat exchanger) how do they cool?

They can't!

This is why I am suggesting to maximise volume of air. ALL intercoolers regardless of the brand WILL work better with more airflow.

IE, using bigger ducts.
I don't think we are missing the point! I think we can all agree the Exige doesn't have enough airflow! Hell I have a three chamber shroud on my Exige! More air flow the better, unless you start condensing your charge air, but that is a different story...

I am just trying to correct the popular sentiment that an aftermarket (specifically RLS) IC will be worse for the car than the cheap stock IC. That statement is false, granted I think the first thing people should be doing is finding a way to increase air flow, then upgrade the IC.

PS. that website you linked is a joke! Specifically this statement: "While aluminum is actually a very poor conductor of thermal energy". Seriously, only copper, gold, Beryllium, silver, and diamonds have higher thermal conductivity than aluminum! It is one of the best conductors actually.
 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
Sometimes I wonder if mid engine is worth all the packaging constraints. What a PITA!
You can blame Lotus sales & marketing... Trust me if the engineers had their way it would work perfectly, but you can tell they were on a tight budget!
 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
Also, this has been working wonders for me! I have been debating about adding cooling fans to the back of the IC, but haven't gotten around to it yet, and I don't know where to tap for power...

 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
I also believe fans must help, all manufacturers use them. The only comments I have read that make sense to me is that they don't nearly move enough air for whar the IC needs. This maybe true.
IC's require a lot of cooling air. That is why you see them in the front of cooling modules. In that location they get the coldest air.

I don't know if I have ever seen an OEM IC with fans attached directly to it, but I could easily be mistaken.
 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
I would imagine that if you swapped out the RLS IC for a stock IC and changed nothing else, you'd see a similar set of pulls.

You can't just get magic cooling benefits from hardware without some place for that heat to go. If there's no airflow, there's no cooling, besides passive radiation. Passive radiation provides virtually no cooling at all and is indistinguishable from the background given the surface area of any IC that would fit in the hatch in this type of scenario.
Wow... Umm that is completely wrong. I will GUARANTEE you will see better results from the RLS IC compared to the stock IC just for the fact that there will be less charged air pressure drop. Right there, that will give you a power bump.

On top of that, the RLS IC should have better heat transfer performance than the stock anyways since it is larger and has more surface area. This means that it has a greater effectiveness which in turn means it can transfer more energy even with the same amount of airflow as the stock IC.

Anyway you look at it the RLS IC will not hurt you, it should only help.

With that said, improving air flow will yield your biggest gain for sure and everyone's number one priority should be improving air flow, then improving the IC.
 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
Thanks for throwing the math out there. I was too tired to try to make a cogent post with math in it. :)

The thermal carrying capacity of the stock IC or even the RLS is very, very small in the grand scheme of things. It will reach equilibrium almost immediately on a dyno run. If there's no airflow, there's no cooling and you're heatsoaked.

Another point I'd like to make with dyno runs is that the fins on the RLS and on the stock IC are pretty dense, you need a lot of static pressure to get a good amount of air through them. Just blowing a fan in front of the car or even straight in front of the intake(s) is not going to yield a lot of airflow. If you really want to test the effects of an IC on a dyno, you need to put a high static pressure fan or fans on the IC itself, meaning you have to have a specific blade pitch on the fans designed to increase the SP and not the CFM. You can have all the CFM in the world, but if there's no pressure behind it, very little will make it through the IC itself, instead creating backpressure on the fan's airflow and robbing you of cooling.
I will agree that thermal capacitance is really overrated since it means you still need to cool it down again...

However I am still trying to understand why you are fixated on zero air flow conditions. I mean yes, the stock IC and RLS IC will perform identically if there is no air flow, but since in the real world there is air flow the larger cooler (RLS) will make more efficient use of the air flow and outperform the smaller cooler (stock) every time, as long as there are the same air flows. It is pretty simple.

With that said, I think we can all agree that increasing air flow is your biggest bang for the buck right?!

Also, if anyone wants a definitive answer, I have access to a wind tunnel that can replicate wind speeds up to 120 mph, solar radiation, ambient temps from -20F to 120F, and it has a 4 axle dyno. Will cost a pretty penny though!
 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
How much does the wind tunnel cost to operate? What kind of pennies are we talking about here?
Ummmm last I recall it was around $7,000/day, not including set-up costs... :crazyeyes

Needless to say you understand why I haven't just done this myself!
 

·
6.94915254 lbs/hp
Joined
·
2,104 Posts
Heatsoak is not a term that has any strict engineering context. In fact after hearing it for so many years I can't even think of a sensible interpretation.

If you mean to say the material condition is carrying alot of heat, the term "hot" or "higher temperature" is pretty ubiquitous here

Perhaps the context is the IC is nearing some portion of steady state full load conditions

or perhaps it implies delta temperatures across the IC are below a certain threashold

Its not a term that makes sence to discuss in the context of thermal science without a rigorous definition.

I certainly agree the thermal capacitance is a negligible factor here.
+1 ...Well said!
 
1 - 10 of 10 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top