Okay, so, this might get pretty involved pretty quick. I'm looking at aftermarket intercoolers for my RS, however, they're all absurdly expensive and reasonably average across the board. I can only assume this is because the Mk1 RS is few in number so the costs going into manufacture aren't offset by massive sales. Anyway. I've got a GT2560LS G turbo on mine, as is stock, and I'm unlikely to upgrade that. However, with an air to air IC I've got no real knowledge on how to scale them to suit the turbo. 76mm cores seem common, but some people also fit hilariously large IC's, which I figure has to be bad for turbo lag, even with a relatively small turbo. The realistic space for airflow is basically a trapazoid, 820-830mm across the top and 700mm across the bottom with height of just under 300mm. I could buy an intercooler that fills that, with respective room for pipes, but that's probably overkill for such a small turbo. Does anyone have any advice on how to judge what size intercooler a turbo needs? I assume there's some equation involving airflow and temperature, but I'm a bit of a newbie when it comes to working this stuff out.
To size an intercooler you need to know a couple of things: The flow rate of air you're going to be needing, and the space you've got to fill. How much power are you aiming for? That directly affects what the maximum flow rate you'll need to size the intercooler and piping for. Too big and you lose efficiency and end up with crappy throttle response, too little and you'll lose a bit of power. To be honest I'd calculate the ideal size for everything and go a little smaller - something like an FRS a big pile of turbo lag is definitely undesirable!
As I understand it, intercooler oversizing shouldn't effect turbo lag, but it will affect throttle response and you may lose some boost. The two main issues with intercoolers, from what I've read, are the backpressure (so the turbo has to work harder) and packaging. You might be looking at a 3-5psi drop across a large intercooler, probably not worth it, particularly as I doubt the car will really run that much better at lower intake temps on the stock ECU. I haven't found a huge amount of lore on intercooler sizing, probably because it involves a lot of the dark art of fluid dynamics. Have a read about turbo sizing, that might give you some idea of what the best intercooler is.
You're right - turbo lag isn't what I meant in my post! A properly sized intercooler you should only lose 1-2psi in restriction - too big and the friction of trying to move the gas through is a runaway effect. The basic idea is to find an intercooler that will handle the required flow rate for the power, and size it appropriately. It is a bit of a dark art because, without wanting to sound like a massive douchebag, a lot of guys who modify their own cars won't necessarily be able to cope with fluid dynamics calcs.
The plan is to run a turbo timer, so hopefully I can deal with any lag that way, but my concern was going too big and buggering the turbo prematurely. Realistically I'm probably not going much more than 300 with the planned mods, so 85 bhp over stock. What I'm thinking is buy a Garrett intercooler core, get the ends and pipe work made up by a friend of a friends who does that sort of thing. I'm of the opinion that I fill the gap in the front bumper bar some little covers and air directors for the ends of the core. If that's not going to cripple the turbo then I'm thinking that'd be the best way forwards. Once all the work mod wise is done it'll be getting a love map put on to tie it all together. If at all possible ill be designing it on inventor and running it through simulator to try and get a grasp of potential losses without actually buying anything straight away.
First of all, a turbo timer is a device for keeping the engine running after the car has stopped so the turbo doesn't crack from cooling down too quickly. Do you mean an Anti-Lag System? Best way to reduce lag otherwise is just choosing the appropriate sized turbo. Do you know what boost you'll be running? I presume you'll have to up it quite a bit to meet your target horsepower. Also, if you aren't getting any noticeable lag right now, then I imagine your turbo is probably going to be too small when you bump up the boost. With your boost figure and swept volume (1.6l engine, so you'll have 800cc=0.8l per rev) you can calculate the total airflow that will be passing through the intercooler.
Reading up on the issue, the car already has a charge cooler in there, is it really worth the hassle of fitting an FMIC? A remap, tubular exhaust mani (you could even ceramic coat it for better heat insulation), high flow cat, exhaust and induction kit should see another 50hp without trouble, and keeps cost down as well as retaining decent throttle response. With a few figures based on 300hp, an IC big enough to fill the gap you dimensioned above will be much too big.
I do, I was typing through beer goggles last night. Most people seem to run around 17-22 PSI on the standard turbos quite happily, and with a few other mods and a good live map, see around 300 without a great deal of effort. Admittedly, up past 300 and the turbo does start to suffer. I'm not really chasing numbers with this car, I'd like to be able to return it to standard should the need ever arise to sell it, so I won't be going too crazy. The mappers I'll be taking it to know these cars inside and out (They're both owners/former owners) and routinely see crazy figures. I think they've screwed 350 out of a Mk1 with a decat, induction kit and an FMIC. They've certainly seen 500+, but that was an incredibly heavily modified car and engine. Guy's a lunatic if you ask me! The standard chargecooler fitted as standard is a problem for several reasons; 1: The box in the engine bay is prone to bursting - To repair that you'd need to cut the box open, so it's not really sensible to do it. 2: The pump fails. A lot. 3: The coolant return from the pump blocks itself up because, comparatively, it's really quite a small hose. 4: The cooler behind the bumper also seems to start leaking a lot these days. I guess being ten years old takes its toll I hate the tubular manifold looks, so I'll be sticking with the standard one for now I think there's only, really, a few different choices for a tubular manifold and they all look like a bunch of banana's. That's exactly what I thought - And really, that's what I was after confirming I'm tempted to go slightly larger than the standard radiator behind the bumper, but only because Garrett don't seem to sell one the same size..
Fair enough, FMIC it is! Can't believe you don't like tubi's, they're the start of every special build.
Have you seen the FRS tubulars? they look shat! http://i179.photobucket.com/albums/w298/NICKB148/bits003.jpg - Ford Motorsport manifold http://img.photobucket.com/albums/v655/morty1961/FRS/DSC00931.jpg - JEK copy of the Ford Motorsport http://i1062.photobucket.com/albums...EB025CB-3251-000003A725A9AD38_zps045a8894.jpg - Direnza "China" http://img24.imageshack.us/img24/3526/cheshireeast20120427000.jpg - Demon Performance Centre http://i137.photobucket.com/albums/q223/Imperial-blue-rs/IMG_4741_zps64fbfb62.jpg - Devil Developments There's a few more too, but they're all just as butt ugly.
The Ford Motorsports and Devil developments ones aren't great, the others look alright to me! Besides, it's not purely about looks, it's about appreciating for something as a performance enhancer too. Besides, I'd rather look at one of those than a horrid cast manifold or a piece of heat shield!
