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Discussion Starter #1
I hear my S240 heatsoaks on track, but I was flying by a supercharged (water to air) elise and also there was a stock elise that was pretty close in the turns, but I clearly had more power on the straights. This was after an entire day of tracking, shouldn't I be back to NA power levels?

So give me an idea... when does the heat soak kick in? How many laps do I have to set a time before I can expect to lose power? How long do I wait to get full power back?
 

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2007 Lotus Exige S
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It depends on the temperature. The intercooler sitting on top of everything and with little air flow to it heatsoaks quickly, you might not even get a full lap before losing some power. I don’t think you will drop to NA levels but you will drop from full potential. I don’t have any data to confirm but if you have video you can look at speeds at similar locations on track if you are consistent enough.
 

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in my experience with two very good drivers at COTA on a 105 degree day by the 1st lap you are slower then an elise with a torque 200 tune on the straights. Basically instantly if it is hot enough.

If I had a stock exige of any flavor still I would at the VERY least get a tune that increases the IAT compensation limits so that the timing retard is much less aggressive.
 

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Also, just to be clear how stark the difference is the elise had a passenger and he thought I had lifted to let him by.
 

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I thought the side scoop mods made a pretty dramatic difference in the IAT, no?
No way you can keep IAT below the timing retard numbers without changing the tune. They start at like 140? I think the coldest I ever saw mine was in the 160s
 

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How to know? By logging the Intake Air Temperature.
Black Dash cars('08+) has IAT info available on the OBD.
RaceChrono, Torque Pro, Harry's Laptimer should be able to log the data very easily with a OBD2-to-Bluetooth/Wi-Fi dongle.

Stock ECU seems to start pulling about a degree for every 10C/18F increase starting from 30C/86F and goes fully retarded at 70C/158F.
According to my datalogs, you reach that IAT usually by lap 2 unless it's chilly out(below 55F/13C). Not much you can do when it's even slightly warm out.
Adding side ducts definitely helps(drops about 10C/18F), but it's still not enough on a stock intercooler, imo. I did 2x 2" ducts. Going larger might help marginally.
I published some data a while back, as well as a back-to-back-to-back runs a couple posts below.
You can see that while the IC sheds heat quite a bit when not accelerating, it is not able to shed enough and accumulates.
In my other datalog, it shows I lose about 5mph in top speed going uphilll between morning and afternoon runs.

I'm sure better intercooler helps significantly, but I didn't think it was significant enough.
I ended up going with a chargecooler setup, and the max IAT when it got super hot out at the track was 51C/124F.

Mind you, if you're just street/highway driving or even canyon driving, you won't notice the heatsoak. It seems the shear amount of time spent at WOT overwhelms the stock IC.

I think some aftermarket ECU tunes are less aggressive at pulling timing.
I've seen a stock Elise SC lose upto 15whp on the dyno just from heatsoak on the same day. It was done "just to see what happens" when heatsoaked.
 

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Discussion Starter #8
TBH, I generally can't tell how hard a car is pulling without a comparison. My '91 Miata feels fast unless I just stepped out of the Exige. That's why I was surprised wheb I had Elise's next to me to compare to, I thought we'd have the same power. Thanks for the OBD-II tip, I'll get a bluetooth reader and try that.

I sort of like the big intercooler up top, and in theory air-to-air is good. But sounds like it's not really usable in the Lotus packaging. I'd like to remedy my power loss, but I'm not sure what all my options are. If I'm going to spend $2000 getting my power back, maybe its time to step up to TVS1320. But then I lose the awesome overhead IC! I guess that discussion is out of scope for this topic ;)

I was just surprised I was easily pulling away from Elises even at the end of 30 min sessions! In reality I must have had like 200hp? Which would explain why all the Corvettes and Camaros and Mustangs were zipping by me in the straights.
 

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rereading that thread it looks like one of the guys with the RLS cooler and side ducts kept his IAT below 131/55 in at least one track video
 

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It would have to be like 50 for that to be possible. Feel more likely that he is driving way under the limit of the car or the data is off.
 

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2008 Lotus Exige-S 240
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I agree with Fork and Kevin, when its in the 80deg F+ outside the IAT is hot enough for the ECU to start backing out the timing. I have RLS intercooler and side scoops piped to the intercooler. All of my vids have that config and IAT displayed. The early vids my SOLO used to also tell the cabin temp but over the years AiM broke that but yet say they also never had it so later vids I no longer have it displayed. Not scientific answer but usually IAT is 40-50+deg F higher than ambient. At one of my frequent tracks it is easily 5MPH lost on the straights anytime it is above 80deg outside.
 

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How to know? By logging the Intake Air Temperature.
Black Dash cars('08+) has IAT info available on the OBD.
RaceChrono, Torque Pro, Harry's Laptimer should be able to log the data very easily with a OBD2-to-Bluetooth/Wi-Fi dongle.
Cars with the white dash can also log IAT through the Torque Pro etc. tools.
 

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I didnt think the white dash cars had that much, although the aim list isn't complete, I've logged IAT with torque pro as well (so any standard obdii stuff is available).

Channels received by AiM devices configured with "Lotus – Clusters 04-07” protocol are:
CHANNEL NAME FUNCTION
RPM RPM
SpeedVeh Vehicle speed
WaterTemp Water temperature
FuelIst Instant fuel consumption
Bitfield Includes the following warning lights: = 1 SFLight Shift light = 2 MILLight Malfunction indicator light = 3 OilLight Low oil pressurelight = 4 TCLight Traction control light

08 is more interesting:

Channels received by AiM devices configured with "Lotus – Clusters 08-09” protocol are:
CHANNEL NAME FUNCTION
RPM RPM
SpeedVeh Vehicle speed
WaterTemp Water temperature
IntakeAirTemp Intake air temperature
TPS Throttle position sensor
PPS Pedal position sensor
CuSelLTC Custom selection - traction control level
MAF Manifold air flow
FuelIst Instant fuel level
Bitfield1 Includes the following warning lights: = 1 SFLight1 Shift light 1 = 2 SFLight2 Shift light 2 = 3 SFLight3 Shift light 3 = 4 MILLight Malfunctioning indicator light = 5 OilLight Low oil pressurelight = 6 TCLight Traction control light
Bitfield2 Includes the following warning lights: = 1 ServLight Service light = 5 TH2OLight Water temperature light
FuelAver Average fuel leve
 

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No way you can keep IAT below the timing retard numbers without changing the tune. They start at like 140? I think the coldest I ever saw mine was in the 160s
Actually, believe it or not, with the stock tune, IAT/timing correction begins when IAT hits 86 degrees F. :eek:
1265614
 
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2008 Lotus Exige-S 240
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That was the point I wasn't so clear in making in my last post (#12). Basically every time I go out unless it is winter my IAT is above 85deg F (see the videos) so the timing is being adjusted to reduce power.
 

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I would be interested in knowing what Phil has set up for Torque 300 tune. I never tire of this conversation, especially the old ones that Thomasio and Forkmeupscotty penned on the topic.
 
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