1972 Firenza "chassis swap"

[firenzaboxer]

Todays progress:

As most will know, Imprezas have a top mounted intercooler. Ideally I'd have converted it to a front mount, but I've barely got room for a radiator ahead of the engine (in fact, figuring out how to squeeze a sufficient rad in is the next job).

Some of you may have wondered about the U-shaped bonnet; the plan was always to have a bonnet scoop that stayed put when the bonnet was lifted:







I'm hopefully going to have a unique solution to avoid the usual top-mount heat soak and air flow issues...stay tuned

[Stiff]

I remember reading somewhere that even with a fmic the Impreza engine still needed the scoop to keep something else cool (might have been the turbo - not sure) so maybe keeping a scoop is a good idea. That fixed scoop is going to look great!
Ram air for the air feed?

[firenzaboxer]

I haven't worked out the air feed/filter location yet. I was going to stick the cone filter between the inner and outer front wing, but they're far tighter together than anticipated.

On my dads original Cresta (the jag xjr based one) he put a duct directly onto a enclosed cone filter (trying for a ram effect); weirdly it strangled the engine; removing the inlet tube, allowing the filter to draw from the engine bay, bought it back to life again.

I assume that, in his case, the engine simply wanted more air than the duct could flow. Still, Ram intakes seem to be something that are easy to get very wrong.

[jonomisfit]

Not sure if all imprezas had this but mine definitely had about a 1/4 of the scoop ducted down to the turbo. There was a little jacket round it with a mesh screen for cooling. It was one of the homollogation ones though so maybe not all had it.

Project is awesome looking forward to seeing it progress. Looks mean.

[fat-stig]

Great build, keep the pic's coming

[firenzaboxer]

I mentioned that my next job was to work out how to sqeeze in a sufficient radiator...today I've determined that it won't work...at least not in front of the engine...

There's enough space in front of the engine to (just about) fit a radiator in, but then there would be no space for fans. I could get a very small fan in on one side; but with only about 20% radiator coverage, cooling would be marginal (even before tuning the engine).

I already knew this was a likely issue (I've been avoiding facing into it tbh), so I already had plan B in mind...a rear mounted radiator.

Step 1: get air into the rear of the car. I'm thinking side scoops; having mocked these up today:








Thoughts?

[ChrisT]

Like the look of them, kind of a nod to Baby Bertha.

[peteh1969]

I do like the look of those scoops. you could also look at some ducting up and over the axle from the back of the floor pan on to one or two rads in the boot.

As a track/road car a little ground effect help would not go a miss.

[claymore]

I think I'd prefer to pick up some air from underneath the car

[Morris63]

Superb thread - epic fabrication skills; bookmarked obviously.

Regarding a rear mounted rad, this is what Andy Forrest said on 22B.com on a thread about fitting one to his Impreza:

"You don't want to exit on top of the boot, that is a high pressure area. I use that as my inlet, rad sits under the floor line for a lower CofG and at 45 degrees to back panel, air exits out the rear bumper area."

Don't know if that helps?

Steve (SORN'd Impreza owner!)

[grenade]

This car when finished? WANT. Great job.

[Stiff]

I think the scoops could look good but they may also ruin the lines of the car, I dunno. It depends on what kind of a look you're after.
I'd probably follow the advice of Andy F as mentioned by morris63 though, he really knows his stuff on these. Here's the link to the thread mentioned: bbs.22b.com/forums/showthread.php?36859-Rear-mounted-radiator
I've seen his car go and it's a rocket on rubber!!

[bmcnut]

Great looking car, will be awesome when finnished.
The scoops look good, add to the aggresivness of the car. Could the scoops be built into the rear arches more? And flow all the way down to meet the bottom of the side skirts so they look more 'built-in'?

[jonomisfit]

If you were lookimg to hide the intakes, With a suitable mesh filter in place could you take the air from the top of the inside face of the rear arch?

It should be high pressure and would pump the air through the radiator. It might suffer from brake dust etc. Coating the rad though.

I like the scoops. Very race car and purposeful.

[firenzaboxer]

Cheers for all the input, sorry for the lack of response...me and the wife have been ill through food poisoning from a dodgy curry...no beer involved (unfortunately)

Regarding picking up air from underneath the car: The impreza isn't ideal for this as the rear subframe is large, and has the fuel tank ahead of it; I doubt much air volume would be picked up unless the duct went lower than both, but then it'd probably ground out easily. I'm planning on putting a custom rad in the place the rear seat back would go (acting like a bulkhead, like at 25 seconds in this video: link); to duct from underneath I'd have to place the rad right at the back of the boot (so the pick up could be further back from the subframe), I don't want to lose all of the boot.

Regarding the exit point for the air: Cheers for the link, I intend to vent in a low pressure area; I'm not convinced the firenza will share the same aerodynamics as the Impreza (more pitch to the rear screen, meaning less air separation), so I'd aim to duct it to the rear (guaranteed low pressure) in the cut out under the number plate.

Regarding the shape of the scoops: I've toyed with blending them in more with the sills (rather than the mustang type ones I mocked up)...Here's a few (badly) photoshopped versions...I'm not convinced:





Any thoughts, ideas, challenges on any of the above please shout up...this is uncharted territory for me, so any input is greatly received!

[shielsy68]

lovely work what gauge of metal are you using 20 22 gauge 1mm ?

[peteh1969]

Agree with you for the ducting now having seen the video.

I thin the middle duct picture is the one for me it looks the best. 

[Stiff]

Something like this maybe?

[bmcnut]

I think the first one looks good, following the line of the door, and mabie flowing into the arch, instead of stopping just before it.

[eurogranada]

In the post with the photoshops my preference is the first one, the gentle curve to the sill area.