[Nitrowolf]

Larger thermal mass is a huge part of the equation. Increased airflow is the other. Either alone will have some benefits, combined is shown to have the best results.

Larger thermal mass really doesn't have anything to do with it, if it's heat soaked. It just means you have a few seconds or minutes longer before soaking.

Increased airflow is the number one priority and given the limited options to work with inside the engine bay, unless you are moving the IC on to the top of your vehicle or using a Air/Water IC, a larger thermal mass isn't going to help in most situations. The only place it will help is on the ragged edge of heat soak where you'd have already heat soaked the stock IC but not the larger IC... and that window is pretty small and honestly if you're in the window, you're not being very efficient anyway.

A more important test for the RLS is how well air flows through it... how closely spaced are the fins and how good is the heat transfer from the fins to the tubing? If the fins are too tightly packed, you won't have optimal airflow, same goes for if they are too far apart. You could adjust the fins on a stock IC and probably get better performance from the same IC.

But again, it's all about the airflow at this point, given the constraints we are working in. If you maximize the airflow, then it's time to look at changing out the IC.

 

[IamBatman]

The benefit of a larger thermal mass IC is that it keeps the temperature more steady. If you measure temp of the IC during acceleration from stand still, starting when your entire car is cold and where there is little cooling air though IC but lots of hot intake air, you'd see more of a rise in temperature in a stock IC. (And in this case I think its much cheaper and probably more effective to add a couple of fans.) In our case of the Exige mail slot design, improving the air flow makes much bigger difference. Especially if you factor in an IC is $1000+ and a shroud and duct is several hundred.:shrug:

 

[shay2nak]

All i know is that the RLS intercooler with 3 inlet shroud and heatshield have shown by my monitoring to operate at lower IAT than stock and recovers quite fast after hard accelerations. And I gained +10whp/+10wtq when I first installed the intercooler and doesn't heatsoak nearly as bad as the stock unit.

 

[IamBatman]

not knocking their product, they make awesome stuff. That IC is pretty sweet as well. My point is that 3 chamber shroud gets you the biggest benefit in that kit, without it, you wouldn't be able to get much benefit out of that super trick IC.

 

[Nitrowolf]

not knocking their product, they make awesome stuff. That IC is pretty sweet as well. My point is that 3 chamber shroud gets you the biggest benefit in that kit, without it, you wouldn't be able to get much benefit out of that super trick IC.

Yes, this exactly.

With regards to your quote about the hot air intake and heat soak while standing... yes you'll see some benefit, but just because you have a higher thermal load ability before it's maxed out doesn't mean you're going to see a much higher benefit.

By that, I mean if your stock IC is heat soaked while standing and your RLS is on the threshold of being heat soaked, your IAT is going to be within a few degrees of the stock IC's heat soaked IC, yielding very little performance difference.

Just because an object can absorb more heat before becoming a radiator instead of a sink doesn't mean it's going to lower your IAT my a meaningful amount. I would be very interested to know how much heat the stock IC can absorb compared to the RLS IC.

Airflow, airflow, airflow.

 

[West oz loti]

Guys,

You are on the money! I have researched this to death, as I had a SC elise previously and don't want to have an exige that drops performance below my older car due to heatsoak.

I have watched videos where the tempretures are live whilst drivers are circulating the track and temps mimic the acceleration (temp goes up), deceleration (temp goes down). The ability of the IC to recover is critical as even with our mods the IC really still doesn't recieve enough air. Having a greater thermal mass just prevents the IC from shedding the heat quickly when decelerating (which isn't that long in a track situation). This is the only time the IC has time to recover.

Therefore why the stock IC preformed so well. It is surprising and it has nothing to do with quality. It is all to do with the poor location and lack of airflow to the intercooler.

Hence my path of trying to get as much air to my IC as possible.

Some more reading ;
http://www.exiges.com/bb/viewtopic.php?f=12&t=15406

The 2-eleven mod will be my go to mod as it has been proven to be most effective. If I can improve on this I may try my new idea. Although if HKfever can make a 2-eleven shroud out of CF I will be very tempted.

 

[forkmeupscotty]

Ultimately, we need this setup.

It's just that it's tad impractical.

It all depends on the track and how much time you spend at WOT, but in my experience on a warm day, stock S240 IC at a racetrack will hit 70C+ by the end of the first lap, 85 by 3rd lap and it only gets worse.

 

[HKFEVER]

This is only a draft.....

4" = 101.6mm is very large :crazyeyes

Can you find 4" air dust?

 

[forkmeupscotty]

This is only a draft.....

4" = 101.6mm is very large :crazyeyes

Can you find 4" air dust?

Well, yeah. At 4", it ain't gonna fit.
I have a spare stock intercooler/shroud that I bought specifically to make a hole for side ducts sitting on my lap right now, and total shroud 'depth' is 3.5".

Stock intercooler's 'lip' that sticks out for the shroud attachment is about 3/4", and the shroud 'lip' that attaches to the bellow is another 3/4". If you're going to work with stock dimensions, you only have about 2" on the side to work with.

Of course if you're going to change the dimensions and come up with an original design, you can fit however big ducts you want. But if you're going to work with stock dimensions, 4" duct is going to take a lot of work....

 

[West oz loti]

This is only a draft.....

4" = 101.6mm is very large :crazyeyes

Can you find 4" air dust?

Yep!

4 inch piping is available in silicon and neoprene through specialised performance outlets on the net. If you want to be a cheap skate you can also use ally AC duct, 100mm. Available from a hardware store.

Lotus OEM will sell you a genuine 2-11 shroud and associated piping, but it is a pretty penny! The geniune shroud from lotus is made from ally and welded together, so it is pretty good quality.


By the way the 2-eleven shroud replaces the stock shroud and deletes the roof scoop! NOT added onto the stock shroud.

 

[forkmeupscotty]

Yep!

4 inch piping is available in silicon and neoprene through specialised performance outlets on the net. If you want to be a cheap skate you can also use ally AC duct, 100mm. Available from a hardware store.

Lotus OEM will sell you a genuine 2-11 shroud and associated piping, but it is a pretty penny! The geniune shroud from lotus is made from ally and welded together, so it is pretty good quality.

If you replace the stock shroud to 211, I assume you won't be making use of the 'mail slot'? Not that it matters too much. It's barely adequate anyway...

 

[West oz loti]

If you replace the stock shroud to 211, I assume you won't be making use of the 'mail slot'? Not that it matters too much. It's barely adequate anyway...

Correct.

To be honest, I am still considering buying the OEM 2-eleven shroud. At least it keeps the car (sort of) lotus original.

 

[HKFEVER]

1. I will mod the OEM Shroud to fit with the 4" dust and also with the mail slot.

2. 2 Curve Seperators in the Shroud to smooth out the flow.

3. Need to make 2 Side Inner Scoops 4" X 7" open with 4" dia elbow outlet that can house the 4" dust.

What do you think?

 

[West oz loti]

1. I will mod the OEM Shroud to fit with the 4" dust and also with the mail slot.

2. 2 Curve Seperators in the Shroud to smooth out the flow.

3. Need to make 2 Side Inner Scoops 4" X 7" open with 4" dia elbow outlet that can house the 4" dust.

What do you think?

This will be good as you have the volume of air from the 2 large 4inch pipes+the roof scoop. My only concern is making it fit.

Normally using the 2-eleven shroud you need to take the boot off going to the roof scoop as it needs this space.

I am all open to new ideas that increase volume of air, if you can make it work and it fits.

Cheers HK!

 

[forkmeupscotty]

1. I will mod the OEM Shroud to fit with the 4" dust and also with the mail slot.

2. 2 Curve Seperators in the Shroud to smooth out the flow.

3. Need to make 2 Side Inner Scoops 4" X 7" open with 4" dia elbow outlet that can house the 4" dust.

What do you think?

Not entirely sure if there's enough space for 4" inlet in the side scoop...
I personally might like to keep and utilize stock side scoops(because I'm weird...

Looking forward to what you can come up with! :up:

 

[West oz loti]

Not entirely sure if there's enough space for 4" inlet in the side scoop...
I personally might like to keep and utilize stock side scoops(because I'm weird...

Looking forward to what you can come up with! :up:

I am also weird and like the colour coded std side scoops.

You are right, from my reseach the std scoops need to find at least half an inch. I haven't picked up my car yet as it is on the other side of the country, ( that will be another thread) so can't do accurate measurements.

Some modding of the side scoops will probably be required to space them out slight.

I have seen pictures of 4 inch piping in the scoops with the cover off and I would imagine it is slightly squashed with the cover on.

Fitting 4inch ducts will be challenging, but I have a few ideas.???????

 

[HKFEVER]

I am also weird and like the colour coded std side scoops.

You are right, from my reseach the std scoops need to find at least half an inch. I haven't picked up my car yet as it is on the other side of the country, ( that will be another thread) so can't do accurate measurements.

Some modding of the side scoops will probably be required to space them out slight.

I have seen pictures of 4 inch piping in the scoops with the cover off and I would imagine it is slightly squashed with the cover on.

Fitting 4inch ducts will be challenging, but I have a few ideas.???????

Use wide scoops

 

[Thomasio]

Someone above said "the thermal capacitance doesn't matter." While that would be true if the intercooler were capable of shedding all of its heat instantly into the ambient airstream, that isn't the case with the Lotus.

Therefore, when the heat absorbed by the intercooler is > the heat shed by the ambient airflow, the heat will dump into the intake air which is exactly what we don't want.

That is where thermal capacitance comes in. The intercooler needs to be able to absorb this heat instead of dumping it into the intake air. The larger the thermal capacitance of the intercooler, the less often it will dump the heat into the intake air.

This has real world results.

 

[Thomasio]

P.S. To say that an intercooler is "heat soaked" means that it has absorbed all of the heat that it is capable of, and can no longer cool.

An intercooler with more aluminum mass will wick away more heat than one with less, and therefore you will almost never reach a situation where it is "heat soaked."

Lotus Cup cars w/ the RLS intercooler can run 20 minutes at full bore at the 4+ mile per lap Road America, pull off into the pits and the intercooler is only warm to the touch. That same car with an OEM intercooler will just about burn your hand.

What does that mean to the intake air temperatures? Of course thermal capacitance matters.

 

[HKFEVER]

P.S. To say that an intercooler is "heat soaked" means that it has absorbed all of the heat that it is capable of, and can no longer cool.

An intercooler with more aluminum mass will wick away more heat than one with less, and therefore you will almost never reach a situation where it is "heat soaked."

Lotus Cup cars w/ the RLS intercooler can run 20 minutes at full bore at the 4+ mile per lap Road America, pull off into the pits and the intercooler is only warm to the touch. That same car with an OEM intercooler will just about burn your hand.

What does that mean to the intake air temperatures? Of course thermal capacitance matters.

:up::up::up: