flat4

i've seen excellent temp readings from my TMIC at all speeds and nothing to make me think i need to go front mount, 500bhp is the cutoff point for using a top mount as you'll be flowing enough air to fill the pipework to remove any lag.

i've read that Jap Per. test, wouldn't read too much into temp readings on a rolling road, not very representative of road use as you'll be getting heak soak when you wouldn't be on the road



i've been known to be wrong in the past though

DaveD

iTrader: (2)

I guess the original intention was to keep the volume of pipework between the turbo and the cylinder heads as short as possible. This probably explains why there is also an inverted U-bend in the exhaust pipe with the turbo at the top.
The early cars had large turbos (for Gp A homoligation) and adding miles of pipework to route air to a FMIC and back to the inlet manifold with lots of 90 degree bends would only increase turbo lag even more.

Just imagine how much effort it takes to compress the air in the volume of a front mount vs a top mount intercooler set up. Each time you lift off or change gear, that volume of air gets vented by the dump valve, and then has to be built up again when you re-apply the gas.

The flat 4 set-up neatly allows the intercooler to sit on top of the engine - not ideal at low speeds, but with some forward motion the scoop on the bonnet does a reasonable job.


The Evo, (along with most other modern cars) is an in-line, 4 cylinder, transverse engine set-up, and lends itself to having a front mounted intercooler. The induction pipework from the turbo to the inlet manifold has to go from the front round to the back of the engine and the difference in length of a TMIC vs FMIC would be negligible.

The modern Subaru rally cars use an FMIC, but the effects of turbo lag are now greatly reduced (eliminated?!) with anti-lag systems and gearboxes that allow for full throttle gearchanges.

I guess Subaru could have mounted the turbo closer to the front of the car, but this would have probably required a complicated exhaust system around the engine for negligible gain.

The Chief

There is always one Smart a**e

NIce one Dave

Shark Man

Alot of cars have TMICs, especially diesels. It depends if you think the gains of a FMIC are significant enough to outweigh the negatives aspects. Bluntly speaking, if it does the job, why faf about with it?

Shark Man

Crikey, you need to do some reading up.

The engine block alone has gone through 3 re-designs, from closed deck, open deck, and semi-closed deck.

Then the umpteen different pistons (slappety slap ), cranks, cams and not to forget SOHC 8valves heads, SOHC 16valves heads and DOHC 16 valve heads, and not to mention variable valve timing.

Yes it's still a flat 4, but its like comparing a small block chevy engine to an LS1 engine, Yes they have the same physical similarities and interchangability but the latter is 30years ahead in design.

cookstar

iTrader: (6)

TBH i think a lot of people are swayed toward the front mount option due to cosmetic value, rather than pure performance gains.

frayz

iTrader: (7)

90% of the aftermarket sh1te bought by people is for this reason mate lol

Ive data logged a few different coolers now and the STI7 onwards TMIC is about as efficient cooler as you will get ever.

Its ONLY flew is some minor heatsoak at standstill, although due to its effeicient design this heatsoak is quickly cooled once moving. Unlike cheap aftermarket topmounts that once hot, stay hot and get even hotter.

Im willing to put my sti topmount up against any cheap FMIC setup and datalog it.. we'll see whats more efficient.

What these "experts" dont know is that as you get a bigger turbo, more air is flowed in volume, therefore the turbo is not working as hard to compress it/

The turbo not working as hard and being more efficient means less heat is produced. Therefore explaining why my ACTs are now lower with a 20g working efficiently than with my stock VF35 screaming its nuts off.

As said by the few people with more than 2 brain cells, the STI topmount is easily capable of 400bhp

cookstar

iTrader: (6)

I will however be interested to know more about the front mounts you were talking about deleloping alongside Zak.

frayz

iTrader: (7)

We will be developing one mate but only when we feel it is required.

Nothing will be rushed i promise you.

cookstar

iTrader: (6)

I am in no rush, like you say my STI8 top mount is man enough for 400, and iwont be knocking on that door for quite some time

prana

twinscroll as well as a much more aggressive tune apart from other things

CrisPDuk

A scoob may have a shorter crank than an in-line four, but it's also installed longitudinally, ahead of the gearbox, and thus ahead of the front wheels. In an Evo (or any FWD car for that matter) the engine is transverse and alongside the gearbox. Thus even though both engines are ahead of the front wheels, an in-line four is only half as wide as a flat four is long, obviously the evo is better suited to the a front mount application.

Speaking as an engineer, I think the subaru turbo/intercooler installation is a masterpiece of design packaging

Besides, apart from he usual traffic light heroes and the muppets with way too much money who can afford to keep buying gearboxes, diffs and clutches, who really gives a **** about 0-60 times

CrisPDuk

Lamborghini - The engine in the Murcielago can trace it's roots right back over 40 years to the very first Miura

Datsun/Nissan - 240Z through to R34 Skyline - 30 years

Jaguar - Over 35 years separate the XK120 from the 6 cylinder Aston DB7

Cosworth - The DFV, the most successful engine in F1 history, from Jim Clark in the Lotus 25 to Michael Schumacher in the Benetton.

Volkswagen - The daddy of them all The same basic design lasted for over 60 years of continuous production, spanning 3 continents and 25+ million units

Need I say more

Evolution, not revolution. That's the name of the game

Prasius

iTrader: (1)

..and if you want to carry the "old engine" thing through to non-performance cars, you'll be hard pressed to find many blocks less than 20 years old which have simply had revised head after revised head slapped on them.

So - how many car manufacturers use the same basic engine design since 1992? Looking across each of their entire ranges I'd say all of them.

CrisPDuk

I forgot one

The UK market 1.3 Ford Ka has the same 3 bearing crossflow engine as the Mk1 Cortina

ReggieMY99

Agree with the above

CrisPDuk

Ford 2.0L OHC (Pinto) = DOHC 8V = RS2000 16V = 2.0L Zetec

Oh yeah, Cosworth made a posh head for the old Boat Anchor too

andythejock01wrx

Why are our UK Imprezas not fitted with twin scroll turbos ? Is it simply down to cost ? They allow quicker spool up. Do they have any disadvantages ?

prana

emmisions I'm led to believe

andythejock01wrx

You Ozzies all drive about in V8 Holdens - I'm surpised you worry about emmissions at all ! Went from Melbourne to Cairns last year over a couple of months - awesome place ! (Would you like to swap for a chilly Scottish day ?!).

MrRA

I think it's to do with EU type approval and the fact that it takes so long to get a change approved. That's why the JDM cars have progressed so much with better turbo designs, better cranks etc while the UK cars have stood still.

dynamix

iTrader: (3)

I believe that Subaru have listened to the enthusiasts saying how much they like the flat 4 burble too

GazTheHat

Does twin scroll automatically dictate equal length headers then?

Shark Man

Kind of, as you have two inlets on a twin scroll, the idea is the the exhaust pulses don't interfere with each other, which makes the turbo more responsive at lower revs.

The Trooper 1815

iTrader: (31)

The flat four as been around longer than 1992. Think VW Beetle's, Adolf Hitler and ole Ferdinand Porsche in the 1930's

Butty

iTrader: (2)

I couldn't agree with you more, but as yet, no one seems to be publishing how good the STi TMIC is from a really well designed definitive test.

There may be a case for classics to fit an FMIC at more modest HP levels, but the newage cars using an STi TMIC appear to have much more potential - but I wonder how much of this is down to the bonnet design in combination with the scoop shape and design of TMIC?
The bonnet shape may allow more air flow to enter the scoop than going over the top of it, especially at higher speeds?
With increase pressure on making cars more pedestrian crash "friendly", the TMIC may have to be changed to an FMIC instead - but that may academic if gas guzzlers start getting penalized more heavily or even outlawed.

Nick

New_scooby_04

iTrader: (4)

My MY 999 runs 320 bhp on the std intecooler for road use (I wouldn't like to push it on the track though) and all appears fine. I suspect the reason Subaru stick with them is becuase they are cheaper and perfectly adequate for most people.

Ns04

New_scooby_04

iTrader: (4)

I'm not sure if it's a pre-requsite for these turbos Andy, but all cars I know of with them fitted also have the equal length headers and that means no flat four burble!

Shark Man

Another point to note, is that I've never been very impressed with most FMIC conversions. Most look untidy and are somewhat of a bodge to fit, with the long lengths of pipework involved, its no wonder that benefits don't seem to be as apparent.

I really am amazed that no real company has set out to make a reversed inlet manifold conversion kit to accompany a FMIC. Perhaps they aren't brave enough? I know the likes of Andy have done it, but these are one off fabrications, and there are a few companied in teh USA that make/convert them, but nothing as a complete install. A relocated alternator, coolant header tank, delete PAS and A/C, reversed inlet manfiold, rotated turbo, and radiator mods would allow a much neater setup using only a fraction more pipework than a TMIC. What extra gains you'd get are questionable, but i'm sure Andy could comment on that. And alot of reverse setups I've seen are equally as messy

frayz

iTrader: (7)

I agree with you mate but the problem you have there is your market. How many people would do all of that to run a more efficient setup?

Most people arnt prepared to go to those lengths so the time, money and effort would not be cost effective IMO.

Its a shame though as i would love to run a setup like that