Somebody please explain intercoolers to me…

[breeze]

My rough understanding,

OEM - Fine for stage 1 tunes on a K03
S3 - Default choice to around 350 bhp / 350 lbft on a K04
THS - I don’t see these anymore but Darkside appears to sell a copy, as does Pumaspeed on eBay. Perhaps more like 400 bhp / 400 lbft, so a not too expensive step up on the S3 cooler.
Wagner etc big money coolers - High end builds / trackdays and so on.

Is the above correct?

Yes, I know I have made the cardinal sin of not talking about charge temps. I do realise that ICs are more about repeated pulls and ambient temperature. If it helps, overlay UK weather but with the potential for the odd track day.

K03 car, just trying to understand the options longer term.

[breeze]

I am thinking a THS clone for a K04 car that does the odd track day feels like a good compromise.

[rich83]

OEM with plastic ends is fine up to about 320bhp so plenty good enough for a a stage 1 ko3

[breeze]

Thanks for that.

I wasn’t that clear - longer term would be a K04 swap!

[pudding]

S3.  Don't need any more than that.  I've done extensive data logging and not seen any weaknesses on a predominantly road car.

Those big Wagners and the like are more suited to hybrid/big turbo builds and 1/4 mile action.

You forgot about the 'Welly cooler' option, which is basically just a (really) cheap ebay clone IC, but obviously you will be aware of the relationship between IC volume and lag.

Stock GTI one is OK, but it heatsoaks easily with remaps.......which is the main problem, because too many maps push the turbo way out of it's efficiency zone, which essentially just turns it into a giant hair dryer, doubling the thermal load on the IC.

[breeze]

S3.  Don't need any more than that.  I've done extensive data logging and not seen any weaknesses on a predominantly road car.

Those big Wagners and the like are more suited to hybrid/big turbo builds and 1/4 mile action.

You forgot about the 'Welly cooler' option, which is basically just a (really) cheap ebay clone IC, but obviously you will be aware of the relationship between IC volume and lag.

Stock GTI one is OK, but it heatsoaks easily with remaps.......which is the main problem, because too many maps push the turbo way out of it's efficiency zone, which essentially just turns it into a giant hair dryer, doubling the thermal load on the IC.

Thanks for that.

So what was the excitement around THS intercoolers a few years ago all about? I would like to be able to do the odd track day from time to time, hence the interest in what is effectively a basic and generally still quite affordable upgrade on the S3 cooler.

Feels like 350/350 is about the safe realistic limit for future modifications. At that power level on a track day I do wonder whether the S3 would cope.

[pudding]

I must have missed that excitement but its the usual aftermarket lure of bigger = better. 

The ECU doesn't start pulling timing until 45 deg intake temps, so there's quite a bit of headroom in the OEM intercoolers. The S3 one seems to hold a flat temperature curve of 10-15 deg above atmosphere over spring/summer, and around 5-10 above over winter.  On hot summer track days, an aftermarket one would probably work out better but it depends on the  boost pressure I guess.  I paid £260 for the S3 one from an Audi dealer, so they're not that expensive.  That was about 6 years ago though!

Yeah 350 is about right.  That is the number the CDL engines used to run in the championship race cars, although Borg Warner only rate the K04 to 330hp max, so there may have been some engine tweaks on the race engines, such as different cams, intakes, exhausts etc as to not require as much boost pressure.