Under Bonnet Insulation - its off again !!
Discussion
I thought I had sorted this one but no, its falling off again. Iv'e noticed also that where its down over the bonnet air intake, the throttle mechanism is rubbing a hole in it, not too clever if it jambs up.
How many other S owners have actually taken theirs off completely and have you noticed any difference?
Does your bonnet get much hotter and has it affected the paint finish in any way?
I read that this insulation is called "sound insulation" rather than heat - again any noticable sound difference?
Comments appreciated,
John Mac
How many other S owners have actually taken theirs off completely and have you noticed any difference?
Does your bonnet get much hotter and has it affected the paint finish in any way?
I read that this insulation is called "sound insulation" rather than heat - again any noticable sound difference?
Comments appreciated,
John Mac
Nope, me neither.
Could it have been added by a previous owner? I certainly wouldn't expect to find any inside the air intake bulge on the bonnet, as this would seriously affect the flow over the manifold and if it comes right to the trailing edge of the bonnet near the bulkhead then it will be stopping or reducing the hot air escaping from under the hood too. That said, in the right places it may have some effect on noise levels (if you can hear anything above the exhaust, that is)and you can get a foil coated version for high temp areas. I would be tempted to remove it all just to be safe.
Andy
Could it have been added by a previous owner? I certainly wouldn't expect to find any inside the air intake bulge on the bonnet, as this would seriously affect the flow over the manifold and if it comes right to the trailing edge of the bonnet near the bulkhead then it will be stopping or reducing the hot air escaping from under the hood too. That said, in the right places it may have some effect on noise levels (if you can hear anything above the exhaust, that is)and you can get a foil coated version for high temp areas. I would be tempted to remove it all just to be safe.
Andy
They originally had a sheet of sound insulation stuck to the underside of the bonnet as "standard" 
- meaning it's highly possible that a few never had it.
Anyhow, it usually starts to fall off, due to the heat that gets trapped there, and can jam the throttle open.
If it's falling off either fix it or (preferably) get rid of it.
The "air intake" on the bonnet bulge does nothing - there's nowhere for the air to exit! If you stop in traffic on a hot summer's day you'll find most of the hot air comes out of the wheel arches.
>> Edited by roy c on Tuesday 11th March 15:29
- meaning it's highly possible that a few never had it. Anyhow, it usually starts to fall off, due to the heat that gets trapped there, and can jam the throttle open.
If it's falling off either fix it or (preferably) get rid of it.
The "air intake" on the bonnet bulge does nothing - there's nowhere for the air to exit! If you stop in traffic on a hot summer's day you'll find most of the hot air comes out of the wheel arches.
>> Edited by roy c on Tuesday 11th March 15:29
roy c said: The "air intake" on the bonnet bulge does nothing - there's nowhere for the air to exit! If you stop in traffic on a hot summer's day you'll find most of the hot air comes out of the wheel arches.
>> Edited by roy c on Tuesday 11th March 15:29
Some of the air drawn in via the bulge and the nose exits between the trailing edge of the bonnet and the windscreen, there's about an inch gap. Of course this only applies if you are moving and it's meant to cool the intake manifold down a bit. So probably no use what so ever then.
Andy
andyf007 said:
Some of the air drawn in via the bulge and the nose exits between the trailing edge of the bonnet and the windscreen, there's about an inch gap. Of course this only applies if you are moving and it's meant to cool the intake manifold down a bit. So probably no use what so ever then.
Andy
As far as I`m aware, this inch gap shouldn`t be there, At least, on my S2 there is a rubber seal that I presume is to stop water running down the windscreen and into the engine compartment. I have to admit though this seal only just touches the body when the bonnet is closed and provides only minimal sealing.
Roy.
My bonnet rubber seal closes behind a moulded section on the body scuttle area, the seal stops well short left and right to allow air to exit but stops rainwater running onto distributor etc.
If anyone really thought that extra air via the bonnet bulge would be an advantage no doubt they would have replaced the existing fine mesh with a larger mesh or drilled holes in the existing to let extra air in (perhaps some have) the free area of the bonnet bulge section can only be about 80% of the cross sectional area which isn't really worth worrying about.IMHO.
Disconnecting the front fresh air inlet tubes and letting them "hang" is more likely to be productive in introducing under bonnet air and still catching air for the cockpit. Again IMHO
80% of the cross sectional area was meant to read - 20% of free air only- which aint much if you measure it - equal to a full open hole about 2 1/4" square having just measured it.
>> Edited by John Mac on Tuesday 11th March 17:30
If anyone really thought that extra air via the bonnet bulge would be an advantage no doubt they would have replaced the existing fine mesh with a larger mesh or drilled holes in the existing to let extra air in (perhaps some have) the free area of the bonnet bulge section can only be about 80% of the cross sectional area which isn't really worth worrying about.IMHO.
Disconnecting the front fresh air inlet tubes and letting them "hang" is more likely to be productive in introducing under bonnet air and still catching air for the cockpit. Again IMHO
80% of the cross sectional area was meant to read - 20% of free air only- which aint much if you measure it - equal to a full open hole about 2 1/4" square having just measured it.
>> Edited by John Mac on Tuesday 11th March 17:30
I had an S2 and originally had the same problem with the insulation falling off. Having stripped it off and glued it back with Evostik I had no more problems in 40,000 miles plus. Pity TVR can't find a decent adhesive for the interior trim too. The option of stripping this off is not as attractive !!
Sounds like the usual TVR variables at work.
Fitter - "We've run out of felt and rubber again"
Gaffer -
"Don't fit any then"
What John says about the bulge intake is correct IMO. The airflow is minimal through it, however that may be sufficient to cool the intake manifold to a degree and that fact should not be overlooked.
It was certainly never designed to be a high volume air intake, merely a necessary bulge in the bonnet which they designed to look like an air intake. A high volume intake would need to be either in the nose or mounted in the high pressure zone that occurs some 8 to 15 inches in front of the windscreen.
This morning the beads of water on the bonnet as I reached 50 flowed backwards and took a line around the intake, so it definitely offers some resistance to airflow at speed. To reduce the resistance you would assume that fitting a larger mesh would be the way to go, however this will also allow large quantities of water in when driving in rain and with the distributor mounted behind the manifold, it may not be such a good idea.
Andy
Fitter - "We've run out of felt and rubber again"
Gaffer -
"Don't fit any then" What John says about the bulge intake is correct IMO. The airflow is minimal through it, however that may be sufficient to cool the intake manifold to a degree and that fact should not be overlooked.
It was certainly never designed to be a high volume air intake, merely a necessary bulge in the bonnet which they designed to look like an air intake. A high volume intake would need to be either in the nose or mounted in the high pressure zone that occurs some 8 to 15 inches in front of the windscreen.
This morning the beads of water on the bonnet as I reached 50 flowed backwards and took a line around the intake, so it definitely offers some resistance to airflow at speed. To reduce the resistance you would assume that fitting a larger mesh would be the way to go, however this will also allow large quantities of water in when driving in rain and with the distributor mounted behind the manifold, it may not be such a good idea.
Andy
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