benimpreza

Hello

Could some one help me please would upgrading myuk 98 intercooler to a sti unit be much benefit

Thanks

Ben

[Davey]

From what I can see the only difference is the colour

hivis

iTrader: (1)

Hi the only thing that makes a bit of a difference is the sti metal hard pipe that flows a lot better than the rubbish small plastic pipe. Also i was told the black ones soak up a lot more heat than the sti ones due to being black dont no how true hope this helps

rigga

iTrader: (4)

core is different inside too........ also why the sti version is more efficient

STI Craig

a bigger intercooler is only of large benefit, if you want to run higher levels of boost.

the are betta mods u can do for the money.....a decat is gives a impresive benefit

silent running

I asked this a little while ago and didn't get a definitive answer. Without having the two in front of me to compare, I'd say the 98 WRX/Turbo 2000 IC and the STi one are identical except the colour. They look the same dimensions. The main difference is in the Y pipe underneath. The STi one has a metal bigger bore Y, that the hoses connect to. The WRX/Turbo one has a plastic bendy corrugated Y which is obviously crap.

Remember even though a black IC soaks up heat quicker, it also radiates heat better as well. Considering this is the primary function of an IC, I'd rather have a black one, any day. I can't see why Subaru would make a LESS efficient version of the STi IC that was exactly the same size. Nor can I see how they could get the standard WRX IC body and try and pack more tubes and fins into it without restricting flow.

Unless someone convincingly shows me the dimensions of an STi which look a lot different to the same year's WRX IC, my money's on them being identical, bar the paint job and the Y pipe underneath.

rentonone

iTrader: (1)

they are not identical, as martin (rigga) said, the core is different for better cooling and holds boost better.

911

Exactly.
If you changing the TMIC fit the biggest one you can get, and that is really a big aftermatket one, or an Sti v8.
There is more to it than just bolting it on!
Graham

silent running

So tell me how exactly the core is different? Is the STi version using bar and plate construction instead of tube and fine? Is it wider or deeper? Are the end tanks different at all? Not trying to say martin doesn't know what he's talking about, but I am an inquisitive fellow, and I want to know exactly why does the STi one have 'better cooling' or 'holds boost better'. I know how an IC works. It's not complicated. For one IC to be substantially better than another with what look like the same dimensions, it's got to be one hell of a better design.

Convince me! If you can show me or explain why the STi one - in the 98 model year - is better, then I'll get one from a scrappies and stick my 98 WRX one on ebay.

silent running

So has ANYONE really got the proper specs of these different intercoolers or have we hit the brick wall again where there's a lot of pub talk about this IC and that IC but when it comes to it there's no hard data? :-) I'll go first, give me a few minutes and I'll measure my 98 WRX one.

rigga

iTrader: (4)

Have you looked inside an sti version and compared the cores to a standard wrx one? as you are well aware of how an intercooler works,it should be clear what the differences are..... but as i think you are so scepticle to the advantage of an sti one over a wrx of the same year its going to be hard to convince you otherwise..... sti's with their better internals and higher rev limits and therfore extra power ( documented as so ) will naturally produce more heat than the lesser wrx, would sti with all the r+d they have just slap a standard but painted i/c on to combat this extra heat? outside dimensions might well be the same due to the packaging constriants of the engine bay... internally they are not

silent running

OK...so this is a MY98 WRX I/C. All dimensions rounded down to the nearest cm and this is the actual working CORE that is exposed to airflow, not the whole body /frame of the thing which is substantially bigger.

37 cm across (30 rows of fins)
14 cm front to back
7 cm deep
Black finish

So that's 3626 cc's of core 'volume' (not really volume as this is made up of tubes and fins which do different jobs, but it's a useful measurement just the same). Let's hear the STi spec then...anyone got a Version 4 that they don't mind measuring up? Pretty sure the version 5 is the same size but just with the different dump valve connector, but can't be certain.

rigga

iTrader: (4)

your talking external dimensions of the core..... not the differences iternally to allow the core to flow better and thus lower the inlet temperature of the compressed charge air

silent running

I'm not trying to take the **** or anything and I am not trying to get into some kind of argument here - well only in the academic sense - so don't get me wrong :-) But I'm tired of listening to people on here simply repeating what they've heard from others on SN.

I genuinely want to find out whether the MY98 WRX I/C really is different to the STi one of the same year. My whole POINT is that I have NOT looked inside an STi one, and I am not the sort of person who blindly believes things I am told. I want someone, like you, who presumably has actually looked at both different I/Cs side by side, to explain to me exactly what design features the STi one has that make it so much better. A photograph would be even better.

Every thread I've noticed on this subject seems to stop short of actually coming out with a detailed physical description of what's so great about the STi I/C. I can see what the obvious differences are - the colour and the Y-pipe. I think the Y-pipe arrangement on the STi would account for a great deal of the supposed performance difference, but I can't be sure because no-one will simply give me the information to work it out for myself. I'm too old to just take things on trust!

silent running

Quite right. As I've said the 'volume' I'm talking about is only a general indicator of IC performance, but it's a pretty good one, because an IC is basically a very simple machine.

There are only two fundamentally different core designs - bar and plate, or tube and fin. Within these two approaches, the only thing that makes a difference to the core performance is the physical size of the bars, plates, tubes or fins. End tank design contributes greatly to an ICs efficiency, but the STi end tanks look the same from pictures I've seen.

With all that in mind, unless the STi IC has some kind of ground-breaking, previously-unheard-of technical leap forward, what it looks like on the outside tells you what it will look like on the inside.

silent running

Seems to have gone quiet again...

911

Not really.
Some (me for one) do take other people's thoughts as correct, especially when they ARE experts (ie AndyF).

Sti fit a better TMIC to the Sti's not for bling, but to get a better performance.
The thermodynamics of the exchanger will be appanent if you could see a WRX alongside an Sti, but most accept that the Sti is the better unit.
What does that mean?

It cools the air faster, for longer because it has to to allow the engine to produce the power.
Sti will go further on their fast versions by adding water spray to the RA's/Sti RA's Type R's etc because owners expect the performance to be better.

I changed my Sti v3 TMIC to an Sti v8 TMIC which was huge when sitting side-by-side .
I did this (without question) as good people told me to do it and benefit from the mods along side it.
The engine gave 407 bhp.

After the RR runs (5 of them in succession) the TMIC was untouchable.
I have now gone to a bigger FMIC in the quest for more cool air for longer (I race my Impreza seriously).

There is no harm in listening to advice, and if it comes from an expert then that is a bonus.
The fact that some do not delve into the physics of the parts is not really an issue?

I would very much welcome someone to mathmatically compare a WRX to an Sti TMIC. Are you going to do that?

ps I have designed and worked with heat exchangers for 10 years in air to air systems but in gas fires/boiler systems.

Graham

silent running

OK now we're getting somewhere. I don't think there's anything wrong with wanting to learn things by working it out for yourself, and yes I am sceptical about most things. Five years ago everyone swore that open induction kits were the way forward on a particular NA engine and I could see that a simple panel filter or remote sealed IKwould give much better results. I argued with people for years over this, flying in the face of popular opinion, but in the end the specialists stopped pushing IKs and started looking at sealed alternatives and the orthodoxy was reversed. I'm not going to apologise for not bowing to the 'experts' - we all have different experiences and we all know a few things. Expertise doesn't just lie with a handful of people's 'say so'.

Now you are a hill climber. I've seen your video and I respect your opinion because competition sorts the men from the boys. Having been a quarter miler for a few years (not in a Scoob) I know that you find stuff that works and you stick with it, regardless of whether it's 'recommended' or not. You test things out for yourself. You do what makes sense and what brings you real results. What you do not do is simply accept things on faith. Philosophy rant over...

Now, I am in no doubt that changing an STi 3 IC for an STi8 is an improvement. From what I can tell (and I've never physically had either in front of me, just seen pictures) it is bigger, logic would suggest that a much later design will have ironed out most of the flaws in the earlier one. I can accept that. You've said that STi fitted a water spray to improve the efficiency of their ICs. That I can also accept, I understand the principle and it's a good one when used correctly. There is no downside to using a water spray except perhaps in competition where you have to weigh up the charge temperature benefits vs. the additional mass of water you are carrying.

But I've still not heard from anyone on here who has gone beyond the basic argument that 'because it's STi, it must be better'. I cannot accept this. I don't believe that Tesco's Wheat Biscuits are any different to Weetabix. I don't believe that my electricity from Scottish Power is any worse than the electricity I used to get from Eastern Energy.

What I am trying to get to, and this is something which everyone keeps avoiding, is what are the specific physical differences between a MY98 WRX I/C and the equivalent year's Version 4 STi I/C? If there is a thread where Andy F (and yes I do respect his opinion, because again, he has proven results in competition) says that the STi 4 I/C is better than the 98 WRX, then point me to it and I will gladly accept it. If he explains that there are a higher density of turbulators within the tubes, or that the tube entrances have been ported or smoothed back, or that the core is physically larger, or that there are more rows of tubes, then great. But so far no-one has stated any of this.

Just saying that because the STi has more power or heat output therefore it's I/C must be better...sorry, one fact doesn't necessarily follow from the other. They look the same dimensions from photographs I've seen, and in that MY outputs were similar anyway. But no-one will seriously help me look into this!

harvey

iTrader: (48)

I don't have a WRX TMIC on hand to measure but I have two STi 3 MY 97.
The core dimensions are 370mm x 150mm x 70mm deep, basically as described by Silent Running. I have no idea how the core compares with a WRX but as far as I am concerned it is irrelevant.
If you seriously want to upgrade your performance, go for a proven FMIC as Graham has already described.

On the WRX, I do know that a number of people reported performance improvements by replacing the 'Y' piece with a silicon alternative which I think came from Samco.
The STi has an alloy 'Y' piece which I think will flow air better than the plastic WRX item.
Both intercoolers are for sale complete with 'Y' piece and one even has the red 90 degree connecting hose to the turbo. (STi in red must be another 50 bhp ) I have seen these put on version 1 and 2 cars as a performance upgrade but like I said above I could not be ar5ed with this mod and would just fit a front mount of proven design and ability.

banny sti

iTrader: (68)

Yes a proven fmic like the autobahn88 intercooler from the group buy a fantastic piece of kit is far superior to any tmic be it a wrx or sti intercooler.

911

The Sti unit i first used on my Sti v3 was fitted as it was 'simple' to do.
It kept the engine looking stock, but kept the pipe lengths short as possible too.

The difficulty in fitting it is underestimated, and it took just as long to fit the Harvey supplied Hybrid to the car as the V8 TMIC.
At the time,(18 months ago) the V8 cost £200, and FMIC's about £500+, justification at the time when so much else was happening with the engine.

The Matrix design on the hybrid is very different to the Sti v8 or the V3 before it, but to be honest I cannot be concerned to technically analyise the units.
The principle reason for my car is hill climbing as fast as I dare.
The wait to take your run can be ages, 5 mins or more, and you are constantly edging to the front car by car (just as in the 1.4 mile..I used to drag race too!) so the engine ticks over and over.
Heat soak was evil on the TMIC's.
I use ice cubes in the water spray just before the call to the line, drown the TMIC with cold water to quench the ic as much as possible (thick wall castings for the end caps on an Sti) and have the water spray (mist?) on right after leaving the start line for the full run of 60 secs on the longest climb i do.
That water must be at 5 deg C.
Even the short hills like Shelsley Walsh (33 second dash) has the TMIC hot!

I (pray) hope that the Hybrid will keep it's cool literally, still drowned with the spray.
I worry about heat soak now from the rad!

For me, the questions over the TMIC/FMIC design are interesting, but there are greater (more expensive) things for the car with far greater speed inducing effects...like a Zen 5 speeder box and Avon slicks; just spent £3500 saying that!

There is a lot to commend the STi swop as long as it is bigger than the WRX/STi unit you are taking off, but i do believe the FMIC is the best way from the start!

Whew, sorry for the rant guys, (but I'm sure this is more interesting than the F1 the wife is watching!!)
Graham


Inside of an Sti v8 TMIC!
http://tinypic.com/view/?pic=rsetrn
And the V8 side by side to the Hybrid FMIC. The depth of the Hybrid is far greater than the V8 I assure you.
http://tinypic.com/view/?pic=rsex45

silent running

Yes that's definitely a lot of common sense there - if you want to get serious go to a front mount. No doubt about that. But at least I've got confirmation now that the STi 3 I/C core is the same size as the v4 WRX one, and presumably the STi 4 one is the same as well unless someone knows otherwise.

Looking at that (very useful!) cutaway of the v8 TMIC the internal construction looks identical to my v4 WRX one. Rows of tubes stuffed with turbulators, all standing proud and interrupting flow. It could be improved by welding in half round sections between each pair of tubes and effectively 'bellmouthing' each one. This was what I thought could be about the only mod that STi might have done but from what I can see there the v8 STi I/C is better simply by its larger core size.

And as we know the pipework underneath is a lot better.

So the conclusion must be that if you can get virtually the same performance from a WRX 4 I/C as an STi 4 I/C just by using Samco pipework for £50...Beyond this, it's time to go to a much bigger TMIC or a front mount.

harvey

iTrader: (48)

banny sti : I have only fitted one "Autobahn" FMIC. The pipes were polished mild steel, not all clips and joiners were supplied, a couple of the pipes were badly bent and rippled and once fitted there was a whistling sound under boost. That was traced to a porous weld.
Unless the quality of these kits has undergone radical transformation there are problems ahead.

banny sti

iTrader: (68)

My pipes are aluminium, according to paul palmer who has just fitted one to his legacy no problems with any of the pipes or clips.

andy97

iTrader: (1)

Graham

It would be very interesting if you were to fit a temp sensor near the throttle body to monitor the charge inlet temps, may a dual spa temp kit for peak hold temperatures, ambient and charge?

This would then put to bed discussion over top mount, front mount, heat soak etc.

Andy

911

Yes, it would be a good thing to do, especially in the summer more so.
How is your car now?

Just read Le Mans (a hill climber in Guernsey) stating a FMIC is slower on the hills than anTMIC...not what I wanted to here!

Proof of everything is in the times!

Graham

andy97

iTrader: (1)

Hit a snag trying to aquire a apexi fc. Car has the 20g on it and new injectors now, but sadly no ecu to run it, i'm hoping it comes tomorrow. This is the third week its not been driven

Ive got other jobs booked to do, but it looks like I'll after to cancel and re-book the appointment with your sponsors, plus the SSC06 is rapidly arriving. I wanted to do the first event and have a go at the SSSO on the 21st may

Andy

911

That is the Loton meeting.
Hoping to do it myself, but may not do the Championship this year due to other racing dates.
Graham

silent running

I did a very simple version of this on my old car to try when fine tuning the airflow through my chargecooler rad. I figured that better airflow through the rad would show up as improvements to charge temps, and it did exactly that. I used a couple of digital temp readouts from Maplins, with remote probes stuck in the inlet tract and right before the throttle body. not the most accurate or fast running sensors in the world, but right for what I needed at the time.

What I found out was very interesting - well to me anyway...firstly any change in the intake air temp at the filter was almost perfectly mirrored at the throttle body. Lose 10 degrees at the beginning of the inlet tract and you maintain that same 10 degrees at the business end. So much for people who told me that underbonnet temps didn't matter too much because the intercooler/chargecooler should take care of it.

Second thing was that proper shrouding of both the front and rear of the chargecooler rad got me a consistent 5-10 degrees less intake temperature across the board, under any condition...I was driving around the 'Ring with bits of plastic sheet and gaffer tape replacing my radiator grille! Not the most professional looking installation but it worked.

I will try and do some more investigations myself when I get the time and equipment. A dual channel SPA temp meter would be ideal - one probe after the turbo and one in the throttle body.