allegro Posted October 10, 2001 Share Posted October 10, 2001 I've seen many sevens with the cutout for the air intake, although the air filter does not protrude through the hole. In particular on the Ks with TBs. Is there any advantage in having the cutout and does it improve air flow to the engine question.gif Andy Mac teeth.gifOut of Control RED SLR teeth.gif Link to comment Share on other sites More sharing options...
Jason Plato Posted October 10, 2001 Share Posted October 10, 2001 Allegro - I've cut a hole in my bonnet ( k series ,DHTB ,ITG filter ) following some tests I did , it was posted a while ago here. I believe the throttle response is now better . Dave Link to comment Share on other sites More sharing options...
allegro Posted October 10, 2001 Author Share Posted October 10, 2001 Thanks very much Dave. Does anybody know where I can get a hole accurately put in my bonnet question.gif I will then get an F3 air filter and hopefully will give me cooler intake of fresh air and a little ram effect. Andy Mac teeth.gifOut of Control RED SLR teeth.gif Link to comment Share on other sites More sharing options...
EFA Posted October 10, 2001 Share Posted October 10, 2001 This idea works until you get to somewhere in the region of 125mph. Then, the headlamp/front wheel causes a -ve pressure where the filter is exposed and power drops. A bit faster and normal service resumes.... I'm going to develop a ram air system for Jenvey SF throttle bodies on a VX 2.0 XE if anyone wants to be party to this paticular project. Fat Arn The NOW PROVEN R500 Eaterid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
murph7355 Posted October 10, 2001 Share Posted October 10, 2001 If you altered the air flow that much wouldn't you need to remap the engine? Wouldn't you need to anyway to see any gains? Link to comment Share on other sites More sharing options...
EFA Posted October 11, 2001 Share Posted October 11, 2001 Most race engines are mapped sufficiently rich at the top end to compensate for the increased air pressure. Fat Arn The NOW PROVEN R500 Eaterid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
allegro Posted October 11, 2001 Author Share Posted October 11, 2001 Dave Did you cut the hole yourself question.gif Andy Mac teeth.gifOut of Control RED SLR teeth.gif Link to comment Share on other sites More sharing options...
Peter Carmichael Posted October 11, 2001 Share Posted October 11, 2001 Andy, You are talking about mapping against road speed rather than engine speed. Just bung in the extra fuel and hope it doesn't end up lean and grenade. Link to comment Share on other sites More sharing options...
AMMO Posted October 11, 2001 Share Posted October 11, 2001 I'm not so sure about this ram air business. I think it would be better described as a cold air system. You must try to guarantee the air into the induction system is not picking up too much engine heat by taking air from a high pressure area of the vehicle. Air in the induction system of a well sorted engine running fairly hot cams travels at around 280 /300 ft per second if I remember correctly. Someone help me with the maths, but I think you would have to be travelling very fast to get any supercharge effect, if this is what you mean by ram air. What I've seen of datalogging from pressure sensors in airboxes on bikes and cars and the pressure never goes very positive. Regarding running lean at the top end if you have a pressure sensor plumbed in to the airbox you can let the adders in the software take care of fuelling. It is also possible for a lambda probe or UEGO sensor to run closed loop only on the top line of the map when the engine is on wide open throttle. I have a very accurate wide band NTK UEGO sensor with a 5 volt analog output which could be used to check what is happening with the fuelling at high speed if anyone is interested in linking it to their data loggers. AMMO Link to comment Share on other sites More sharing options...
Jason Plato Posted October 11, 2001 Share Posted October 11, 2001 Allegro - yeah , I cut the hole my self . Simply measured up where the bottom and leading edge of the ITG 150 filter was in relation to the top of the chassis , covered the entire area in masking tape. Drilled a hole in the area that I thought was the middle of the filter ( after about 5 fags in nervousness !! ) and then cut the hole out with a jigsaw using a fine blade . Re-fitted filter , bonnet , trimmed with a flap wheel , re-fitted bonnet , trimmed etc etc . I'm very happy with the result although I will add a thin rubber strip around the cut out just to make it look as if it was meant to be . All in all took less than 2 hours . The filter now protrudes - not as much as Arnies due to the lenght of the trumpet , engine position etc , but it looks real good teeth.gif and sounds great . I will fit a carbon blanking plate for "quite" trackdays and revert to the 50mm filter to keep the noise down . Dave Link to comment Share on other sites More sharing options...
murph7355 Posted October 11, 2001 Share Posted October 11, 2001 Oh yes. Link to comment Share on other sites More sharing options...
Big Brother Posted October 11, 2001 Share Posted October 11, 2001 Recently cut a hole in my bonnet to allow for larger filters. I used a Dremmel..not quick but fairly neat. Finished off the hole with rubber trim used to "trim" Mini wheel arches. Its VERY flexible, easy to fit, follows the contours of the hole and costs about £3 per metre. Oh..it also looks pretty good too and comes in a variety of colours! Steve cool.gifScream...if you want to go faster!!!id=limegreen> cool.gif Link to comment Share on other sites More sharing options...
Mike Bees Posted October 12, 2001 Share Posted October 12, 2001 The "ram air" effect is, surprisingly, very small. Remember when the F1 powers-that-be dicated that airboxes had to have holes cut in the back to negate any performance benefit? They dropped the ruling after they found it made next to no difference - and that's at F1 speeds... Mike Link to comment Share on other sites More sharing options...
Stijn LUYCK 1 Posted October 12, 2001 Share Posted October 12, 2001 But they still talk about ram-effect with motorbikes and the difficulties of not having the effect when testing them on RR's ... Guess that is a sales thingy as well then? Link to comment Share on other sites More sharing options...
AMMO Posted October 12, 2001 Share Posted October 12, 2001 Mike Exactly my point. I think you have to be travelling in excess of 200 mph to gain any benefit. I think having an airbox is a good idea. I want to make one for my car at some point as I can't stand the induction noise on long journeys. 90 dba inside the car at 4,000 rpm. Most of the noise is from the induction system. I wear earplugs all the time. I doubt an airbox will give any other benefits apart from silencing. Stijn Motorcycle journalists always get dyno figures for a bike and add an extra few bhp for "ram-effect at high speed"!!! All front running bike and car race teams run exhaust sensors and datalogging to set their fuelling as it cannot be done on a dyno. You can get it very close, but not perfect. When racing every little bit helps. On twin cylinder bikes it is normal to datalog each cylinder individually and have a map for each cylinder as they run considerably different due to all sorts of reasons. AMMO Link to comment Share on other sites More sharing options...
Chelspeed Posted October 12, 2001 Share Posted October 12, 2001 The MBE 941 ECU already has a barometric pressure sensor which is used to correct the fuelling for changes in ambient air pressure. If you connect this by a small bit of plastic tube to the inside of the ram effect air box then it will automatically add the correct amount of fuel for the ram effect. No need for any mapping changes. Whether it would give a significant increase in power is another issue. As a by-produce any sort of box around the air intake should give a big reduction in drive-by noise from the intake so it would be of interest to me if only for that reason. Link to comment Share on other sites More sharing options...
Morls Posted October 13, 2001 Share Posted October 13, 2001 While very high speeds are required to give a significantly positive pressure, the gains claimed for most ram air systems are more likely to be due to changing from a layout which originaly tried to draw from low pressure areas. Most motorcycles pre-ram air tried to draw fresh air from gaps in the bodywork parrallel to the direction of travel. The velocity of the 150mph breeze down the sides of the bike would make anything inside the fairing a lower pressure than atmospheric. The relevance to sevens is that so many variants have used the air filters on the side of the car, an area of high speed moving air, where the pressure decreased with an increase in car velocity. All current motorcycle thinking seems to start with a large volume air box, over 10 x engine capacity, fed from an area that is at least not low pressure at high speed. Honda tried to get around the changes in fueling with increased speed by some sort of solenoid to reduce intake area at low speed, but I think this may have been pure gimmick. For those with trottle bodies operating in a still airbox, telesopic trumpets would surely increase the width of the powerband. I do not know if these have been tried already on sevens. For anyone as sad as me, and actually interested in such theory, the late John Robinson's books on Motorcycle chassis and engine design contain huge amounts of info that applies equally to four wheels, particularly a four wheel motorcycle. Mark Link to comment Share on other sites More sharing options...
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