Air box or not
Discussion
Anyone seen a speed six with short trumpets on the throttle bodies? I don't like the air intake from under the car and notice what a poor quality item the standard air filter box is. It is even loose on the throttle bodies and no doubt lets in unfiltered air.
I have found 2" i/d trumpets and drawn up some adaptor sleeves with matching i/d. These will cost about 200 quid to get made, plus the trumpets and filter socks....re map and whatever else I need to do.
It will be tight but I am sure it will miss the bonnet.
ta J
I have found 2" i/d trumpets and drawn up some adaptor sleeves with matching i/d. These will cost about 200 quid to get made, plus the trumpets and filter socks....re map and whatever else I need to do.
It will be tight but I am sure it will miss the bonnet.
ta J
Not entirely convinced by that inlet manifold design. It looks far too small to be able to flow sufficient volumes for a 4ltr NA engine. I'd imagine that cylinders 5 and 6 would suffer from air starvation.
Also, airbox tuning and resonance is very important for high performance NA engine. Something that looks to have been ignored with that design.
Also, airbox tuning and resonance is very important for high performance NA engine. Something that looks to have been ignored with that design.
The original is a good shape. Shame about the quality. What started this was me noticing how poorly the original fits to the throttle bodies. Then I see how poorly finished inside it is. Then I where the air comes in...I know if I take air from under the lid it will be warm so I fancy cutting...yes cut my Sagi..to allow a sensible air intake from somewhere else...not sure yet...so no jig saw in hand.
The photo is neat but in line with comments above I am concerend about pots 5 and 6.
Cheers for the responses though,
J
The photo is neat but in line with comments above I am concerend about pots 5 and 6.
Cheers for the responses though,
J
Sagi Badger said:
The original is a good shape. Then where the air comes in...I know if I take air from under the lid it will be warm so I fancy cutting...yes cut my Sagi..to allow a sensible air intake from somewhere else...not sure yet...so no jig saw in hand.
J
Not done this but, was considering when last in bits:J
Move expansion header tank to right of engine
Turn the power steer pump around
Cut aditional hole in front of air-box
Pipe to OS light air intake
G
Jig saw getting ready... Just not sure about why the original took air from under the car. Seems like worse possible place. So now I am looking at bespoke air box, trumpets etc and a bit of cutting. Any one any good with carbon fibre? Worth mentioning is that I have fitted a larger oil filter. The original looks so undersized. It has a PRV fitted and no doubt at full flow it probably opens and allows unfiltered oil through. I have increased filter area by 50%ish. So now the air intake pipe is lying on the floor with no place to go.
cheers,
J
cheers,
J
Sagi Badger said:
Jig saw getting ready... Just not sure about why the original took air from under the car.
J
OK, always applaud someone willing to make improvements but...J
I spoke to the factory about this when new, and have researched it with an engineer; it was a convenient location with a short hose (inc.low cost) and performance-wise took cool air from under the car in a pretty impressive volume (compare cross-sectional area to inlet for a V8 for example). Engineers will confirm that a much longer duct to the front can lose more than it gains due to flow-dynamics and heat-soak, and the space for a similarly large duct is unlikely.
On the dyno last month the standard duct to an ACT carbon airbox was not a restriction even on my modified 4-litre, which breathes very healthily at peak revs.
As Ceejay says, it could become an issue if you close off the air supply under the front of the car. If a higher intake could be arranged with no disadvantages it would be better for hot days as the temp close to the road/track surface is always many degrees hotter than a foot abpove it. But as it stands I think you're more likely to cause restrictions than benefits unfortunately.
Paul, I agree on the dyno the standard air intake shouldn't really be restrictive. My concern is when the car is at speed where the high pressure air potentially passes over the open end of the duct causing a possible partial vacuum or at very best turbulent flow. It's basically how some spray guns pick up paint. We have a large aperture in the middle of the car which ducts air to the rad. I think we can pick up air from one of the standard T350 front ducts to the air box. We'll see how it works out.
ceejay said:
P, I agree on the dyno the standard air intake shouldn't really be restrictive. My concern is when the car is at speed where the high pressure air potentially passes over the open end of the duct causing a possible partial vacuum or at very best turbulent flow. It's basically how some spray guns pick up paint. We have a large aperture in the middle of the car which ducts air to the rad. I think we can pick up air from one of the standard T350 front ducts to the air box. We'll see how it works out.
Hi Cliff, yes there is that aspect, but I'm not convinced that it would be a problem even at 150mph due to the engine intake vacuum being so overhwhelmingly great in comparison ie. the same reason any ram-effect on an intake is actually so little in practice unless there's a really huge collector - but for your racer I'm sure you're right that one of the T350's intakes would do nicely now it's not needed for cooling. 
Edited by tail slide on Sunday 20th April 17:53
I don`t think you will have a great vaacum in the inlet at full throttle , if you have you must be loosing power somewhere .If you take the air from under the car which must work like a venturi you must loose power compared to taking it from a high pressure area . It would be good to find out how much .
Wow, what have started here? I have a road car. I can't afford to race despite working every hour God provides daylight. My experience is with A series engines in minis a long time ago when air filters and air intakes didn't matter so much, you just squeezed it in and when for a quick blast. What you guys are talking about interests and educates me at the same time but...I won't be doing 150 MPH in Essex, not for long periods of time anyway.
What started all this for me was the air box being loose. Whilst off I notice the small oil filter. What is important for me is clean air, keeping the bigger oil filter, cos I am concerned about the PRV being open on the small one, and it not costing too much. The real scary bit is sucking water off the road or next doors cat up the air intake and firing it out the side shooter in a ball of soot and flames. Whilst good sport it could clog it up.
I am now set on modifying the existing and cutting one hole. The duct will be as big as I can make it and insulated.
Cheers,
J
What started all this for me was the air box being loose. Whilst off I notice the small oil filter. What is important for me is clean air, keeping the bigger oil filter, cos I am concerned about the PRV being open on the small one, and it not costing too much. The real scary bit is sucking water off the road or next doors cat up the air intake and firing it out the side shooter in a ball of soot and flames. Whilst good sport it could clog it up.
I am now set on modifying the existing and cutting one hole. The duct will be as big as I can make it and insulated.
Cheers,
J
Sagi Badger said:
......... or next doors cat up the air intake and firing it out the side shooter in a ball of soot and flames.
Now I know why ours keeps her distance.The little extra air hole in the back of the airbox is there to avoid enough of a vacuum forming to suck water up in a flood, as long as the engine's running slowly of course. But your mod will probably be fine, just not noticeably better than standard for road use, in my humble opinion.
You touched on an area several of us had been thinking about! PH is great for this kind of thing
S5TVR - unfortunately we didn't have chance to do before & after with airbox, and it has a higher-flow cylinder head etc. compared to a Sagaris/TuscanS. Hopefully someone will do a back-to-back test soon...
Edited by tail slide on Monday 21st April 18:48
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