Fitted a thermocouple into TB inlet today, what sort of figures should I be looking at (ie over ambient)..?

Steady driving it was same as ambient, giving it some boost ~+4 deg. Yet to try sustained hard driving..

Standing in traffic 2-3 mins ~ 12 deg, dropped to ambient within 10 seconds of moving off again.

Interestingly (sp?) as soon as engine is shut off temps soon fly to 40-50c, but again drop within 30 sec or so to ambient.

Just a bit of research really..

05 WRX TD04 usual ecutek mods and STI 8 TMIC and scoop.

Cheers,
Jason

 

I'm not talking specifically about Scoobs here, but in general about turbocharged road cars, so bear that in mind. When I say chargecooling I mean air/air OR water/air cooling of the inlet charge.

But anyway, your aim in chargecooling is to keep the inlet temp (at the TB where you have correctly measured it) at ambient. In practice this is very difficult to achieve without any compromises but you can get very close with a well designed chargecooling circuit.

As far as actual temps go, I'd always worked on the rule that no more than 10 degrees over ambient temp was a very good result. That is usually achievable under mild load - part throttle, decent gaps between using boost etc. The real test is if you take it for a proper blast, really hammering it around the back roads of your private test track, or even on a track day where it's relentless full throttle/full boost over and over again. I think if you try that, you'll find a different story: the charge temp will be 'ratcheting' up, each time adding a bit more temp and the I/C will be unable to dump the extra heat quickly enough before the next pile of boost comes through.

To get an idea of it, find a bit of straight and really go for it, a full bore straight line acceleration, up to the redline in every gear. See what happens to your charge temp. I'd be surprised if you weren't running pretty hot.

I think the thing about shutting off the engine and the temps shooting up (as I'd expect) then back down again, shows that contrary to what a lot of armchair experts think, the Subaru TMIC isn't THAT bad a design. OK the fundamental idea of top mount instead of front-mount IS a major flaw, but if we can accept that it's simply a case of how best to 'package' the engine bay then it makes sense for a road car.

The engine block is away to the front of the TMIC and at standstill there's not a huge amount of heat right under the I/C. There's plenty of clear space between the underneath of the I/C and the gearbox housing which itself is in a fairly cool location. The main heat source around there, regrettably is the turbo, which without a heatshield is a little too close, but then again it is off to one side and the exhaust system in general is pretty well out of the way.

I think this is why Scoobs tend to be able to get away with retaining the TMIC whereas on other cars equipped with a TMIC, virtually your first job is to dump it and go front mounted.

The bonnet vent serves a dual purpose in that it also allows heat to convect up from the TMIC and the turbo at standstill, whilst reversing its role once on the move. Exactly the same concept as on a Clio 16v/Williams bonnet scoop.

Keep the results coming. I'm glad there's someone out there who's actually trying stuff out just for the hell of it. Once mine's mapped and running properly, I'm going to be doing pressure testing all over (and under) the bonnet to see what the front end airflow is doing at different speeds, especially flow through the scoop at high speed.

 

I'm just naturally inquisitive (sp?)..

I've still not given it any stick yet (might go out for a blast in a mo although excessively cold ambients may effect result) but normal driving I'm getting ambient charge temps, just need to find out what I'm getting during heavy boost sessions..

LOL, I did some airflow testing a few months ago and found that airflow over scoop was consistent upto 120 (didn't go any higher,ran out of runway..!). Infact I was going to repeat and video it, which I'll try and do when weather improves.

Where would we be without a bit of R&D..

 

Well I've just fitted a scoop splitter so hopefully that will help.