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Discussion Starter · #1 ·
The question being the efficiency of the intercooler on an Exige S with three different top configurations.
1. Factory hardtop
2. Top removed
3. Canvas top from Elise
I've been wondering since I got my Exige S several months ago whether the intake scoop on the car really made much difference,so I set up a little experiment.
Note that when installing the canvas top the opening on the aft part of the scoop was fettled out,as shown in the photo,for better flow. The hardtop was replaced after doing the fettle job and before all these tests.
Using a differential (delta) thermometer which shows the change in temps between the two probes I made several 50 mph runs on an 80 degree day both into and with the wind. Each run was made after getting the engine temp stabilized at 190 degrees and attempting to eliminate variances in heat soak by driving a circular route for about 4 miles. The temperature drop was noted after 2 more miles in each direction.
Run one with the roof in place showed a drop of 12 degrees with the wind and 18 degrees against the wind.
Run two with no top showed 15 degrees drop with the wind and 19 against the wind.
Run three with the canvas top showed a 17 degree drop with the wind and 22 against the wind.
Maybe 50 mph isn't the best speed for these tests but seemed to me to be a good starting point. I will attempt to try again at different ambient temps and different speeds. I did note that at low speeds of about 25 mph the temps without the stock top seemed lower than with it in place but no real data was collected.
Fettle...good word.
 

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Glad to see your using an actual instrument to do measuring instead of guessing.

I went through extrensive work to get cooler radiator temps down on a Vette I roadraced. It's hard to argue that more air is better. Get all you can. If you're limited on available air, as the Vette radiator was, then you have to use what little you have as efficiently as possibly. That means finding the pathway of the airflow through the exchanger. At low pressure levels in front of the exchanger, tha air will take the path of least resistance. That means there will be dead spots. With a lot of effort you can find these with the thermocouple probed into various locations in the core. However, I think probing for air flow or pressure may be easier. The readings will be more consistant. You can make deflectors to direct air into the dead zones. I played around with the Lotus oil cooler for a few minutes. I rammed some air into the front of the clam opening with a gas leaf blower. I used a very low pressure gauge (indexed to inches of water column) and probed around the backside of the core and measured the pressure. You can make a slack tube manometer filled with water and save buying a gauge.

Maybe you can work a couple of small motorcycle fans behind the core. I got 2 at a wrecking yard, it was good for 10 degrees, these were low amp. Spa makes some small ones too. Get a few of these and you'll suck leaves off the trees as you drive by.
 

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Very nice. Can you provide the actual T1 (in) and T2 (out) temps? I've been curious about this same thing and would like to figure the IC efficiency using the formula below.

% Thermal Efficiency = 100 x (T1 - T2) / (T1 - Ambient)

Having that, see where improvements can be made and, probably more importantly, provide a baseline for dyno tests for the S. A lower efficiency should produce lower hp figures (sitting in a garage) while a higher efficiency (packing ice on the IC) should produce higher hp numbers. This should let us know if an hp change is a result of the tuning or a different IC efficiency on that day.

Also, I am far from an engineering person. Does this theory make sense to those who know better?
 

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Discussion Starter · #4 ·
Just made another run w/o top at 60 mph but the ambient temps were quite a bit higher. Inlet side on the core measured 132 and outlet 116. Wind was so gusty I ran parallel to it (perpendicular). I am actually amazed at the drop.
 

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shay2nak
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you mean the IC works best with the soft top on, then no top and lastly with the hardtop???
 

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Makes sense. The S air scoop is shorter with the softtop on (or no top) and should therefor have less friction which would deliver faster flowing air to the intercooler. The softtop probably assists in directing more air to the inlet than no top on.
 

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What was the ambient temp during your runs? If you have it from the MAF that's even better. 132 downstream of the SC isn't very high. MPH is kind of meaningless. What RPM were you runnning for the tests? By the low SC outlet temp it doesn't seem like you were running high rpms or doing much compression.
 

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this is a very interesting finding and discussion, i'm keeping my eye on this one... thanks.
 

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As someone mentions, unless the SC is on full song, the test is not that useful. What's most important is what are the temperatures after full throttle, as that's when the SC would be working hard and therefore the intercooler will be heating up.

BTW, slightly different topic bu removing the hardtop screws up the smooth airflow onto the rear wing. Not noticable on the road, but dire on the track.
 

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Next someone should try with a small fan pulling air past the intercooler.

I had a temperature probe on my SRT-4 that was right after the throttle body. So it was measuring temps after the turbo and the intercooler. I usually saw temps about 10-20*F above ambient. Since I had an oversized turbo, the temps would actually drop a couple degrees when I got on it because when I was just driving around regularly I was actually outside of the turbo's effeciency rating. Of course my intercooler was the size of my front bumper.
 

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Great work, thanks very much for taking the time to post it. Look forward to seeing more measurements with the car at full boost.
 

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What about getting a dremel tool and opening that air intake up a little bit? I saw it done on other threads. Would be interesting to take temps after opening and getting more air through the IC
 

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Dmbrown34 said:
What about getting a dremel tool and opening that air intake up a little bit? I saw it done on other threads. Would be interesting to take temps after opening and getting more air through the IC

when i installed the soft top i did cut the heavy lip off of the inlet so it is a nice smooth, uniform, unrestricted path.
 

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TJ ROOLS

That T.J. sure is a helluva tech.:clap:

He rocks. :up:

He is dedicated...he better buy me lunch for this plug:popcorn:

TJ keep up the great work

soon everyone will be coming in to have you fix their cars

NICE!!!!!
 
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