henry21p Posted July 10, 2010 Share Posted July 10, 2010 The 21's underbonnet temperatures are causing the mems to adjust the ignition by -5.5 degrees at full load and even -3.9 at light throttle openings.... With bonnet open the figures are more like -0.2 at 36 degrees. Looks like with the rbtb's I need to duct in some cooler air. The engine bay is underskinned and that lovely bonnet keeps all the air in, with only the two bonnet nostrils letting it out. The 21 has an extra strut running across the top of the current sausage filter. The filter also "rests" on the brake master cylinder which is in a different location to the 7. I think I really need a "Y" shape with the inlet coming from the driver's sidepod which is open to the air (and where the standard supersport engined 21's duct their air to the plenum) Anyone here have any experience of creating bespoke airboxes that might be able to lend me a hand? Also - I probably could do with putting a few louvres in the undertray to improve airflow into/out of the engine bay when running. As i understand, there is negative pressure under the car so they need to be "out" rather than "in". Anyhoo. Link to comment Share on other sites More sharing options...
henry21p Posted July 11, 2010 Author Share Posted July 11, 2010 tumbleweed....... I HAVE had an email from one of the original team who worked on the 21 and i think we agree that i want to duct from sidepod. Any other contributions Link to comment Share on other sites More sharing options...
henry21p Posted July 12, 2010 Author Share Posted July 12, 2010 one more email suggesting a custom job from reverie - i may give them a call! owt else? Link to comment Share on other sites More sharing options...
Jason Plato Posted July 12, 2010 Share Posted July 12, 2010 what's the space avaiable ? any pics ? here is my Duratec R .... C7 TOP Taffia AO Link to comment Share on other sites More sharing options...
Doug phillips Posted July 12, 2010 Share Posted July 12, 2010 Thinking out loud here Dave, but have you ever seen a snorkel kit for a Land Rover (the type that up the outside of the windscreen to stop water getting into the carbs) . As the V8 has twin carbs, there is a ready made Y piece with flexible piping, may worth a look . Su77on Se7ener Link to comment Share on other sites More sharing options...
Powderpuff Posted July 12, 2010 Share Posted July 12, 2010 David, Is this a place to start here? I run a Reverie airbox in the 7 similar to Mr F who has additional ducting in the SV to pull in cold air from under the nose of the car....if you can get an airbox on the 21 then ducting to the nose scoop might work more easily than using the side pod...possibly? G The name's Puff, Powder Puff N7XTC Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted July 12, 2010 Area Representative Share Posted July 12, 2010 David Whatever the problems don't follow this example! Stick to the side pod, big ducting. I'll talk to Rob on my return (23 July) if you haven't sorted it... Democratic dissent is not disloyalty, it is a positive civic duty. Link to comment Share on other sites More sharing options...
OliverSedlacek Posted July 13, 2010 Share Posted July 13, 2010 I've been musing about airboxes recently, trying to come up with a solution that is quiet enough for track use but doesn't lose power. The one we tried dropped the power of a 1.9K from 234BHP down to 216BHP, so a 7.7% loss. It had a volume of about 10 litres, which means that it's more than 5 times the engine swept volume. The guidlines I've read recommend 7 times the engine swept volume, so I'm looking for another 3.3 litres. Link to comment Share on other sites More sharing options...
mav Posted July 13, 2010 Share Posted July 13, 2010 I can post some pics later if D21P doesn't mind, as the car is currently in Cheshire 😬 Link to comment Share on other sites More sharing options...
fred_gustafsson Posted July 13, 2010 Share Posted July 13, 2010 How come you lose power with an airbox? Aren't they supposed to increasing the pressure of the incoming air and therefor increase the power output? Link to comment Share on other sites More sharing options...
henry21p Posted July 13, 2010 Author Share Posted July 13, 2010 yes please mav! nocando on ducting from the front - too many chassis rails and bits and bobs in the way. advice from techie people 'in the know' is that i want a 'still' airbox rather than anything that might have pressure in it related to movement. the other thing is to reduce the underbonnet temps anyway - louvres in the undertray might be an idea without affecting the handling at high speed. the 'fake' air intakes in the lower bonnet area are an idea for getting cooler air in, however i suspect that the problem is retention of warm air as the only 'out' is around the seams or the two bonnet holes. i was considering venting the front edge of the bonnet up where it meets the screen maybe. i can't interefere with the channels that prevent water washing down onto the electrics from the windscreen, but there is a 'lip on the underside of the bonnet that i might be able to vent. mav - if you're being a happy snapper with the camera, could you post a piccie of that edge too please? Link to comment Share on other sites More sharing options...
OliverSedlacek Posted July 13, 2010 Share Posted July 13, 2010 Air boxes are supposed to provide a reservoir of still air for the engine to breath from. If they are too small, one cylinder steals air from the next. If you are looking for ram effect, you need to be doing about 150 MPH before it's measureable. As for venting underbonnet air, you want the hot air outlet to be in a low pressure area where it will be sucked out. The base of the windscreen is usually a high pressure area, which is why it is a favoured location for engine air intakes or cockpit air intakes. Link to comment Share on other sites More sharing options...
mav Posted July 13, 2010 Share Posted July 13, 2010 Currently chucking it down... Will have to wait until it stops - later or tomorrow... Link to comment Share on other sites More sharing options...
Mavic82 Posted July 13, 2010 Share Posted July 13, 2010 As OS says most vents around the base of the windscreen will push air in not out. I would suspect that a good 'vent' would be to hole the front inner wheel arch liners to allow air to spill out. This will no doubt increase drag though and possibly front end lift? Guy Link to comment Share on other sites More sharing options...
henry21p Posted July 13, 2010 Author Share Posted July 13, 2010 given airflow over bonnet top and up across windscreen in a 21, would expect it to have a net effect of pulling air "out" rather than the opposite. I know that the undertray is there to create negative pressure under the car and help with handling at speed (or so says the result from the wind tunnel testing). Really there are only a few locations for in/out of airflow: 1. up airscoop and past rad = hot air 2. past exhaust manifold = hot air 3. bonnet holes "out" for hot air 4. driver's side sidepod - where the 1.6ss ducts air to the plenum from 5. the fake "air inlet" holes in the lower bonnet. the concern with these is that they would affect airflow into the rad or handling. it would be possible to use them to duct air "in" to the engine bay, but without somewhere else to let the hot air out, no idea what that would do I would think that creating a cold air "in" at front and "out" by upper edge of bonnet would create a flow through the engine bay. it may be that small changes however make a big difference - a net cooling effect rather than the steady high temps undfer bonnet. They aren't creeping higher - they stabilise at the high 50's. Link to comment Share on other sites More sharing options...
jackb_ms Posted July 14, 2010 Share Posted July 14, 2010 Hi Dave I have been aware of a heat issue under the bonnet since the DTH RB where fitted last year. My plan to reduce air temp under the bonnet was to open the driver side skin to replicate the passenger side and open the air intakes at the front. In my mind the area in front of the doors is a low pressure area and at least in motion under the bonnet is a high pressure area even with the two nostrils. So logically there should be some air movement. From the pic on caterham21.com it looks like one of the race 21 had some kind of cf airbox. That would have been plan B if plan A did not reduce under bonnet air temp. I would be interested in an airbox if you have one produce specialy Cheers Jack Emily, The Very Yellow 21 Link to comment Share on other sites More sharing options...
Irrelevant Posted July 14, 2010 Share Posted July 14, 2010 Get a plastic airbox . . . Cut and plastic weld to fit space . . . Duct from a hole in a dummy vent. Job done . . . Link to comment Share on other sites More sharing options...
myothercarsa2cv Posted July 14, 2010 Share Posted July 14, 2010 Could you not knock up something in glass fibre or similar that attaches to the dummy vent and goes direct to the airbox? If it was sealed from outside to the airbox you wouldn't need to allow the extra air in to escape as it will all go in the engine - a bit like the yankee ram airs? I've wondered about why Mini didn't do something similar on the cooper S. John _________________________ myothercarsa2cv Bugsy: '82 2cv6 😬 Talloulah '08 1.6K Classic Link to comment Share on other sites More sharing options...
henry21p Posted July 14, 2010 Author Share Posted July 14, 2010 If i end up with "ram air" going in, surely the change in inlet manifold air pressure would be picked up by the sensor and yet more adjustment to the fuelling take place by the mems. Thinking about it, it uses an adaptive map at under 3750 and uses the values from that over 3750 to adjust fuelling - with little ram air effect at pootling speeds, wouldn't I just run lean at higher speeds/revs then? Not comfy affecting the airflow in, just the temperature of it. Jack's idea of venting the engine bay to the driver's sidepod is actually quite a nifty one. Might consider that. Link to comment Share on other sites More sharing options...
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