Discussion
I have a '89 350i that obviously has the non vented bonnet. I'm in the process of sorting the cooling system out with new rad and stuff, would a vent help keep things cooler on a 350?
Who/how could put them in my bonnet or would trying to obtain an 400SE etc bonnet work?
>>> Edited by waynester on Thursday 9th October 14:33
Who/how could put them in my bonnet or would trying to obtain an 400SE etc bonnet work?
>>> Edited by waynester on Thursday 9th October 14:33
I don't know about all the 390s, but mine was originally fitted with a ventless bonnet (1985) but acquired a vented bonnet before 1991 whilst the factory had it.
One thing that the OS (top) vent does is let water in to sit on the battery tray until you turn right ... then all the water hits the exhaust manifold and clouds of steam erupt from everywhere. Most impressive! This was reported elsewhere, but happened to me last Tuesday and it was instant panic until I remembered! I still stopped to check though.
Streaky
One thing that the OS (top) vent does is let water in to sit on the battery tray until you turn right ... then all the water hits the exhaust manifold and clouds of steam erupt from everywhere. Most impressive! This was reported elsewhere, but happened to me last Tuesday and it was instant panic until I remembered! I still stopped to check though.
Streaky
The vents are supposed to serve three purposes that I know of: cool air to the air filter, a diagonal flow of cool air across the plenum and out at the rear vent to aid cooling and allowing more hot air to escape at the rear. I'm not sure how effective any of it is though. The 400s also have an oil cooler and I think that this is a more useful mod for a 350. The vented bonnets look good though...
The 520 in its 390 days only had the bottom vents actually cut through. Seen this on a lot of cars. The battery area still fills with water as it flows direct from the windscreen. The bonnet at the back had no where for the heat to go. Had to do some major work when the 520 engine went in so the bonnet got redesigned completely.
The 520's lightweight bonnet has a 3-4 inch gap at the back and a 30 inch wide scoop at the front (like the elise/Tuscan) which works very well with the 520 engine.
The early Tasmins had several different vents mainly at the back but these have dissapeared.
The 520's lightweight bonnet has a 3-4 inch gap at the back and a 30 inch wide scoop at the front (like the elise/Tuscan) which works very well with the 520 engine.
The early Tasmins had several different vents mainly at the back but these have dissapeared.
19560 said:My 390 has an oil cooler (NS and forward of rad at bottom) - Streaky
The vents are supposed to serve three purposes that I know of: cool air to the air filter, a diagonal flow of cool air across the plenum and out at the rear vent to aid cooling and allowing more hot air to escape at the rear. I'm not sure how effective any of it is though. The 400s also have an oil cooler and I think that this is a more useful mod for a 350. The vented bonnets look good though...
shpub said:
The 520 in its 390 days only had the bottom vents actually cut through. Seen this on a lot of cars. ...
My top vents are cut through and backed by metal gauze (as are the bottom vents). There is also a cutout in the bonnet return (ie. the bit that turns under at the windscreen edge) next to the windscreen wiper to allow air into a hole (again gauze covered) that I guess feeds the heater. This hole is roughly cut and unpainted on mine - so I guess another factory 'mod'
- Streaky >> Edited by streaky on Thursday 9th October 17:21
You can get a vented bonnet from Trevor Bee at TET Mouldings
www.b-link.co.uk/tet/
He will alsp sell you just the vents to fibre glass in.
www.b-link.co.uk/tet/
He will alsp sell you just the vents to fibre glass in.
When me and my missus went round the factory in the mid 80s we saw the factory 420 in preparation (the one that eventually got banned from racing for being too good). This had the prototype vents - half inch holes drilled straight through the bonnet. When the highly skilled mechanic had been drilling the holes he had managed to follow through into the inner wing and leave witness marks. I think that Jeff Statham's car still has those witness marks to this day.
I have found in the hot weather and the drivers window down that you get some serious hot air coming in from the top/offside vents when in traffic and the fan is running.
Personally Iprefer the shpub/jeff Stratham set up of vents to the leading and trailing edge and using a 350 style (complete bonnet).
GB
Just been out in the SEAC and notice I've got a vent in the back face (underside as seen from the drivers seat)of the bonnet which doesn't go anywhere underneath the bonnet
>> Edited by TaSmania on Friday 10th October 16:35
Personally Iprefer the shpub/jeff Stratham set up of vents to the leading and trailing edge and using a 350 style (complete bonnet).
GB
Just been out in the SEAC and notice I've got a vent in the back face (underside as seen from the drivers seat)of the bonnet which doesn't go anywhere underneath the bonnet
>> Edited by TaSmania on Friday 10th October 16:35
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