OK I’ll do an update, might just need to edit it later to add some stuff that’s missing. I’ve been waiting for some dyno graphs to post up, I neglected to take any copies whilst there so Dan is going to send me some over next time he’s in the dynocell… not nagged him because he’s a busy boy 
I was booked in to see Dan “first thing” Monday, which was a bloody stupid idea. M1 on Monday morning in an Exige, in the rain… pretty miserable!
Arrived and Dan wasted no time getting the kettle on whilst we got the car ready for geo.
As expected/hoped it wasn’t a million miles out - I’d not touched toe/camber at the rear so it was just a case of sorting front toe out and ride heights. Even the ride height didn’t need much adjustment, but Dan did notice that my NS Front was carrying a bit too much camber (as OS Front was maxed out with no shims) so we added a shim back into the NS to even them out at approx 1.3 deg.
The overall car weight was a pleasant surprise. This was before adjustment so only the headline figure is really relevant:
I calculated the net gain of the charge cooler being 13kg so to think this car was a sub-900kg car stock is nice to know. I’ve been assuming it was close to the wikipedia figure of 930kg (since I do have carpets, AC and pig iron wheels) but I can only assume that’s for a black dash car with all the extra gubbins in it.
It’s good to know that I’m a set of forged wheels away from being sub 900 again, but I’ve decided in the meantime I need to lose 3kg bodyweight to get it back under a tonne with me inside. Anybody know where I can find a carbon fibre burger? 
Once the suspension was sorted, it was Dyno time. As said I don’t have the graphs for this yet and my memory on the figures is starting to haze over, so might have to retro-edit later.
After warming the car up, we did three “power runs” and a “test the charge cooler” run in which the car was held at highish RPM for a bit before doing a WOT pull right at the end. The results can be summarised as follows:
- All runs within 1bhp of each other
- IAT’s didn’t exceed 26 degrees and recovered back to their 16 degree tick-over temp very quickly each time
- AFRs bang on the money
- Headline figure 255bhp ATF / 216bhpish ATW. Torque I’ve forgotton.
My biggest regret of the winter is not getting a dyno run done before I took the car apart. You can probably ignore any of the following comparisons if you’re a true scientist, but working with what I’ve got I can make some conclusions.
First up, the headline figure. I did not expect any power gains from the charge cooler, I was told by a few people that the 260 map responded really well to intercooling/charge cooling upgrades and that I could maybe make a bit of peak power out of it - but I never really expected it. I have however seen dyno readouts from other 260 cars that have made comfortably into the 270s, I’m not dismissing those or diminishing their numbers I’m just aware that all cars, dynos and days are different. I’ll talk more about the headline figure and my next objectives later.
Second up IATs, they were amazing! Again I’ve got no dyno comparison but I do have a road comparison from some tests I did last year.
Dyno pulls: 8degree ambient
(first run is warmup, second run is the “abuse the CC” run, third and fourth are power runs with the final power run missing because I took the phone to make a video)
Peak average around 25degrees, settling very quickly each time down to the 16 degree “baseline” for tickover.
Road pulls: 12 degree ambient:
Peaking over 40 degrees, never really settling down to the original “baseline” of 21/22 degrees for off-boost driving
I think it’s fair to say the charge cooler is a bit of a monster, and that those gains are excellent. The heat soak element is only half of the story, the fact that peak temps are almost halved is just crazy, this should reduce the parasitic losses on the supercharger nicely as it’ll be so much easier to meet the boost target. Really looking forward to logging a trackday too.
I may need to edit this section later, but we were able to compare my graphs against a legit 260 cup car that was on the standard intercooler. Obviously different day, different car but still yielded some interesting comparisons. This particular car made 268bhp(something like that) but when we overlaid the curves, mine was making more power all the way through the range and only got pipped in the final 500 rpm or so. The torque graph showed even bigger gains (to my car) in the mid range. Oh, the 260 Cup car also lost 5-10 bhp PER RUN when doing back to backs!
I’m really happy with how the day went, the car feels very quick to me currently - so if it is “only” making 255bhp then that does give me a bit more ceiling for cheap-ish improvements. If I’d have dyno’d at 280bhp (for example) I’d be at my ceiling already, and I’d take no pleasure from the higher figure.
Whilst spending the day messing around with the ODB reader and logging the various info, I came across something. When at WOT, my Throttle Opening % (at the manifold) is reading 78%. This initially meant nothing to me (who’s to say the ECU is even measuring a linear 0-100% scale?!), but then I stumbled across an old post on forum with this information in it about the Exige S maps:
220 = run on 315 injectors with throttle percentage of 67%
240 = run on 440 injectors with a throttle percentage of 78%
260 = also runs on 440 injectors with a fully opening throttle 100%
Suddenly that 78% figure started to seem a little bit coincidental, no?
I don’t for a moment thing that I’m running the 240 map on my car, the 255bhp figure should be evidence of that alone but I’ve also spent plenty of time on track with 260 Cup cars and I’ve had no issue holding straight line pace with them, I know that’s hardly scientific - but the car just feels too quick for that.
There’s also the 255 map that is floating around, I don’t know what the throttle limits were for that though and I’m struggling to find any info on it other than it was apparently crap.
I’m fairly certain I’ve got the 260 ECU and that the 78% thing is just an anomoly, but I need to confirm it one way or the other so I’ve asked for some of the 260 owners that I know to take some similar readings, but none are currently armed with an ODB device. Alterntively Oakmere Lotus have told me they can plug in and tell me one way or the other, but that’s another day off work and ~200 mile journey I can do without this month!
If there are any readers/lurkers here with a 260 ECU (or 220 or 240 tbh, it would be good to compare notes) then please feel free to contribute
Once I put that to bed, I’ve got a couple of options for trying to untap a bit more power:
- If I don’t have a 260 ECU, then I should certainly try and source one… might be easier said then done…
- If I do have 260 and still want a bit more, then it’s time to go aftermarket. Really liking the look of the EMU Black ECU that a few people have fitted recently.
Happy days anyway, car is now fully ready for use - time to get some track days booked I think.
Oh, and to add - Dan @ HPE is great, a fantastic contribution to our ‘community’ and is certainly somebody I will use more of. His Honda work is well known/established but there’s not much he doesn’t know about the Lotus cars and engine tuning in general - so well worth a chat if you’re considering some outside help with a project.
