s3 intercooler heat soak..

[ald1717]

temps have been getting into the low 20s over the last few days and i am experiencing heat soak after some thrashing, a minute of driving off boost seems to alleviate this, is this normal for stage 2 cars even with the s3 intercooler?
should i also think about adding a twintercooler, or is it just not worth it for the few weeks of hot weather we get here?

[ROH ECHT]

That doesn't seem normal...need to also be suspicious of the IAT sensor reports. If reporting inaccurately, then this could be causing some timing pull when not necessary.

An S3 and Forge Twin-cooler does a very good job. So I'll post the following for your review.

This is just water flow testing results (not many coolers included)...it is not a cooling test, and note the Forge is done with the std GTI cooler. Also shows some that flow worse than the stock GTI cooler:



This data is mine, first log on this day in September, with both S3 and Forge FMTwinC...showing IAT in column 'N':



I have another log done just after ↑that↑ one, and the temps start at 25°C, go up to 27°C between 3k and 3200 rpm, but then drops to 24°C by 4k rpm and holds there to redline.

[ald1717]

thank you, do you know how much a iat sensor is? 

[JoshB]

Oh, when I was messing the other week I was getting IAT’s around 35degrees. I just assumed it was normal given it was 20 outside… I’m on a stock intercooler though. Should I be expecting lower?

[pudding]

10-15 above atmosphere is normal and acceptable once the car is up to temperature. You won't get much lower than that with air-air intercooling. ECU doesn't start pulling timing until 45 deg C IAT.

The IAT sensor being in the middle of the intake will report higher than expected temps at idle/part throttle, but once the throttle is opened up again, the temps should drop right down again.  I would only pay attention to the temperatures in a VCDS log before, during and after a WOT pull.  That will give you an indication of how hot the intercooler is getting and also it's recovery rate.

The S3's recovery rate is a lot better than the GTI's.  You don't need anything bigger than that on a road car.

[ald1717]

thanks guys

[ROH ECHT]

thank you, do you know how much a iat sensor is?

Not sure what it would cost you...I'm in the U.S.. A genuine VW IAT sensor here can cost near $90usd and an aftermarket near $20 U.S.. And yes, know the IAT is reporting inaccurately before replacing when there's no need to do so.

[ald1717]

i have seen febi bilstein ones for £10 but i know that the pcv febi makes dont work correctly so could be the same for other parts, just thought if it was only £20 or so i would just stick one in to see, but the car is being given to my brother in a week so i think i will get him an ultra gauge or something similar and then i can see what the iat is as well as fueling boost ect

[pandaman]

An S3 and Forge Twin-cooler does a very good job.

Just butting in, did the pipes on the forge twin fmic fit the S3 intercooler as is? Thinking about getting one but I'm unsure of how the pipes would fit.

Thanks

[rich83]

An S3 cooler and twintercooler is gonna set you back about  £750 minimum in parts.

Plus additional volume meaning more lag.

[pudding]

Yup. Lag is a big consideration when upgrading intercoolers.  No one really talks about that, but I noticed a slight increase in lag when switching from GTI to S3.  Probably why the S3 has different mapping and cams to the GTI/ED30.

[ROH ECHT]

Just butting in, did the pipes on the forge twin fmic fit the S3 intercooler as is? Thinking about getting one but I'm unsure of how the pipes would fit.

Thanks

You need to specify you need the Forge S3 hoses when ordered. The S3 inlet and outlet ports are a smaller diameter than the couplers fitting the stock OE fmic.



Regarding lag...they say this ↓ , but not sure if they are being honest or if this is a political statement:



I didn't notice a LAG feel with mine...but I added the S3 and Forge the same time as the K04.
I do know its actual boost will match its target/specified within 600 to 700 rpm when doing a data log run, starting the run from 2k or 2.5k rpm.

[pudding]

When I say lag, I don't mean nothing, nothing, boom, but rather a slight loss of crispness to the onset of boost.....if that makes sense.

[ROH ECHT]

Yes, I imagine a bit of a nearly impossible to feel delay...or a less immediate, snap-to-life feel? Yeah...I get it. When I saw the Forge response...I too thought they're not going to come out and admit something of the sort. And I had nothing to compare it to...having done all mine at the same time.

[pudding]

Yep, exactly that. Likely an immeasurable difference between GTI and S3 as VAG will have done their homework, but all the same, behind the steering wheel in the real world.....a slight feeling of less urgency when spooling up. Obviously once into the meat of the boost, all good 

I did initially put it down to my swap to a MK6 gearbox possibly having taller gearing, but thinking back, it was the same with the stock trans as well.

Well, Forge are naturally going to say there's no lag with their twintercooler, but basic physics and facts would disagree. I guess some of it comes down to mapping. Kick the turbo in earlier to compensate for the bigger space it has to fill. I'm pretty sure that's what VAG did with the 6R/S3 by way of more intake cam lift/duration and more N75 lower down.  Dunno, just a hunch.  They do feel very alert and punchy low down compared to an OEM K04 GTI.