STI7/8 Intercooler Undertray Measurement
 

Can someone do me a favour and give me the measurements of the rubber skirts from an STI 7 or 8 intercooler undertray. Specifically I’m looking for width and depth measurements allowing me to calculate the area (i.e. I want to know the size of the hole through which air can access the intercooler. Note I’m not talking about the size of the entire undertray – just the area defined by the rubber skirts.

Thanks,

Kenny

Heading down to the garage tonight?........take a tape measure :D:p

OK just been out to the car and it is 18" x 5" , that is for a STi8 scoop undertray which i have on my car now instead of the WRX one ;)

Baws! I've got an undertray from a UK300 and thought the skirt area was the same but it measures at 16.5" by 5". I'm wondering how much 1.5" matters ;) I could try and modify it a little I suppose. The skirts of the STI undertray must go right to the very edge of the intercooler then as the 'fin' are is only 18" accross.

I knwo that Subaru VER 7&8 WRX and STI use the same rubber.... even tho its a different undertray

Andy

WRX & STi can't use the same rubber as when i got the STi one it was longer than the WRX

The skirt length is sized according to the TMIC core size, regardless of being bug or blobeye.
Its the top part of the splitter that varies according to bug or blobeye/ WRX or STi scoop shape, as it has to fit into the space under the scoop.
In fact the blobeye WRX scoop has about the same volume under it as the bugeye STi scoop.
So why does the STi8/9 need such a big scoop? Is it just a big willie waving exercise or does the larger scoop mouth REALLY shift more air across the IC?

Nick

That can't be right though butty. Granby says his rubber skirts are 18" appart (width measurements) and the skirt from the UK300 is only 16.5". My undertray is from Gusthebus's car which is a blobeye for what its worth. My intercooler is the STI 7/8 jobbie and the area of fins is 18" wide. Is it worth trying to get a 18" sti undertray for that extra 1.5" or width or should I fit the one I have? I could perhaps try and modify the one I have to be slightly wider by borrowing rubbers from my soon to be defunct STI-5 undertray.

Well Subaru Say the part number is the same for both cars.... Inless they STI is streched more when fitting.

I was with you when i was looking but they say nope the rubber is the same part number

The 16.5" x 5" core/ skirt size is off a WRX IC.
A UK/JDM STi core/skirt is 18" x 7", not 18" x 5" - I wonder if that measurement is a US STi IC dimension?
Granby - where did you source the IC & undertray?

Saxo - your STi IC is not getting the full airflow over it because your using a WRX undertray. Only 65% of your IC is getting full air flow on it - so you may as well put the WRX IC back on.
If you want to keep the WRX scoop, buy an STi undertray and tweak the height of the duct (done this myself). You then have the stealth of a WRX scoop but it ensures that the STi IC is getting the full air flow over it to ensure best conditions for reducing the charge tmep.

Nick

WRX skirt is 43" long.
STi skirt is 47.5" long.

Problem with part no.s?

Nick

Intercooler was from someone on here, think it was a JDM
Undertray is a Zerosports item
Rubber skirt was from Subaru (part no 90817FE040) for a UK blobeye

I currently have an STI 8 intercooler and the standard STI-5 undertray and as such a lot of the intercooler isn't fed a flow of air. Gus the Bus was kind enough to give me the undertray from his UK300 and it measures 16.5" by 5". This would obviously be an improvement over the standard undertray I have now and by the looks of it, would be easy to fit with some simple adjustments. Would it really be worthwhile to get the full monty STI undertray and cut/bash that to fit or would the UK300 suffice?

FWIW I'm not looking for monster power here - just a safe 315-20bhp from an STI-5 with a full decat, STI 8 intercooler, Walbro and remap. Andy F commented that the existing standard undertay was particularly bad becase hot air would likely skip around the uncooled areas and mix with the cooled air thereby raising its temperature again. The UK300 skirt seems to give pretty good overall coverage so surely would reduce this to being negligable?

Saxo,
Your current UK300 undertray could have the opening widened by taking off the skirt and "peeling" the four support sides away to give a larger area.
A longer piece of skirt would then be needed (47.5").
This peeling would have to be done accurately so that it is in line with the IC core.
The skirt would also have to be deep enough so that there aren't any gaps between it and the IC core with the bonnet down, resulting in airflow problems like Andy has mentioned.

... or buy an STi 7/8 undertray. Again the std skirt depth may not be wide enough to give a snug fit, if the classic bonnet is higher than the newage one - the undertray is then further away from the IC core.

BTW - Did the UK300 undertray fit without any problems and line up OK over the IC?

Nick

I've not tried to fit it yet - I don't want to butcher Gus's tray until I'm 100% sure I'm going to use it. I have been considering peeling it to be bigger - I could retrofit some of the skirt from my old tray to 'fill' the gap.

How much is an Sti 7/8 undertray new ?

Pass, most people seem to want £60 odd for them 2nd hand though. So its Free vs £60.

You're making your own Kenny ? Where did you get the bits ?

Andy

I've got an undertray from a UK300 - its only slightly smaller than the STI item so may be modifiable to achieve good overall coverage. I'll worry about it as soon as I've figured out where I'm leaking coolant :rolleyes:

Cheers :thumb: