O.k so this may be a dumb question but I'm going to ask it anyway. What is the best way to lift my bonnet up at the rear to create a little gap? I was just thinking to add a few washers in at the rear bolt on the hinge between the bonnet and bracket and lift it up that way. This won't exactly be very pretty tho so thought I'd ask how other ppl have done it.
Whats the general sort of height ppl lift them? Just wanting to get rid of some of that hot air thats trapped in the bay.
Cheers,
Spacing Bonnet
Started by
_MAWLER_
, Apr 26 2006 03:43 PM
33 replies to this topic
#2
_torana_
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Posted 26 April 2006 - 03:49 PM
the dumb question is the one you dont ask
I think you can move the bonnet hinge brackets up and down a fair bit. Loosen one side and move that corner the height you want , and then do the other corner.
Anyone else?
I think you can move the bonnet hinge brackets up and down a fair bit. Loosen one side and move that corner the height you want , and then do the other corner.
Anyone else?
#3
FastEHHolden
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Posted 26 April 2006 - 04:55 PM
zoom did an article a while ago...they chopped up some square tube and fitted it between bonnet and hinge for a 25 mm lift.
#4
Tiny
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Posted 26 April 2006 - 05:50 PM
I agree with Torana, THe hinges move around HEAPS. If youve seen pics of my car, that bonet lift is just done on the hinges.
I've gotto re-route the lines so i can close that gap up.. looks a bit silly at times!
I've gotto re-route the lines so i can close that gap up.. looks a bit silly at times!
#5
_brett_32i_
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Posted 26 April 2006 - 11:00 PM
the torry bonnets sit high when the hinges are all the way down as it is. and i think you have about 1/2" you can raise the hinge.
#6
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Posted 27 April 2006 - 09:10 AM
Sweet, thanks guys. I'll try moving up the hinge like you say, that is a much better way of doing it. The gap on your Q looks plenty enough for me Tiny, so if you've only moved the hinges then I think it'll be the way to go.
Cheers,
Cheers,
#7
_devilsadvocate_
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Posted 27 April 2006 - 09:20 AM
Have you removed the rubber seal on the rear edge of the bonnet itself , makes a fair difference if you pull it out.
#8
_Bomber Watson_
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Posted 01 May 2006 - 07:06 PM
remember, for some reason it seems to work backward. move the hinge up and the bonnet sits lower, so i assume moving it down would bring the back of the bonent up.
the reason for that little rant is cause if your having troulbe making it sit higher....just try it the other way around
the reason for that little rant is cause if your having troulbe making it sit higher....just try it the other way around
#9
_TORANR AMORE_
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Posted 01 May 2006 - 07:20 PM
If you've got those stone guard things fitted inside the front engine bay area, then take them off, It'll allow a lot more air to enter the engine bay from underneath and from the sides. This helps reduce heat in the engine bay.
As for the Bonnet, yeah it works like Tiny and torana said, to 'tilt' the bonnet.
Anyway, givus a yell if you need help.
As for the Bonnet, yeah it works like Tiny and torana said, to 'tilt' the bonnet.
Anyway, givus a yell if you need help.
Edited by TORANR AMORE, 01 May 2006 - 07:25 PM.
#10
_HatchmanSS76_
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Posted 02 May 2006 - 08:01 PM
I wouldn't recomend pulling that out.Have you removed the rubber seal on the rear edge of the bonnet itself , makes a fair difference if you pull it out.
Mine was missing in the Hatch and didn't think anything of it. When I put the MSD dizzy in, it alowed water to run down and into the dizzy. Made a absolute mess of an expensive bit of gear. Another few weeks and the whole thing would have been junk as well as the water would have started getting into the block.
#11
_devilsadvocate_
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Posted 02 May 2006 - 09:40 PM
Neither would I!.(Would get hot air running down the plenum chamber and out the vents. But raising the back edge of the bonnet by a cm is going to make the seal superflous anyway, so why not achieve the same difference by just taking out the seal if removing hot air is the aim?I wouldn't recomend pulling that out.Have you removed the rubber seal on the rear edge of the bonnet itself , makes a fair difference if you pull it out.
Edited by devilsadvocate, 02 May 2006 - 09:41 PM.
#12
Dr Terry
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Posted 03 May 2006 - 10:13 AM
Hi Guys.
You blokes have got this backwards. If you lift the rear of the bonnet to create an air gap, air will travel INTO the underbonnet area at speed, not out of it.
Have a look at an A9X bonnet scoop, it is to supply air to the carby, not let air out from under the bonnet. That area just in front of the windscreen, is the highest pressure point, at speed. So if you lift the bonnet at the rear, air will exit at low speeds (10-30 km/h), because of the action of the engine fan, but as you build up speed, the pressure will increase & air will ENTER the underbonnet area.
This is not good either, because it is most disirable to get as much air as possible thru the radiator, not underneath or around it.
If you want a good example of that, just remove the undertray from an LC/LJ Torana & see how much warmer it runs at speed. The air that goes in underneath is now not going thru the radiator.
Dr Terry.
You blokes have got this backwards. If you lift the rear of the bonnet to create an air gap, air will travel INTO the underbonnet area at speed, not out of it.
Have a look at an A9X bonnet scoop, it is to supply air to the carby, not let air out from under the bonnet. That area just in front of the windscreen, is the highest pressure point, at speed. So if you lift the bonnet at the rear, air will exit at low speeds (10-30 km/h), because of the action of the engine fan, but as you build up speed, the pressure will increase & air will ENTER the underbonnet area.
This is not good either, because it is most disirable to get as much air as possible thru the radiator, not underneath or around it.
If you want a good example of that, just remove the undertray from an LC/LJ Torana & see how much warmer it runs at speed. The air that goes in underneath is now not going thru the radiator.
Dr Terry.
#13
_MAWLER_
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Posted 03 May 2006 - 01:06 PM
Interesting what you are saying Dr Terry, and I do agree. The aim was to allow an escape point for the all that hot air at slower speeds while sitting in traffic etc. when I want to keep it as cool as possible. My other thought was, yes, considering the A9x scoops were to provide air to the filter, wouldn't this also have the same affect of getting colder air in and around the engine bay and therefore the intake, again a plus.
How will this affect the flow of air through the radiator, surely the same air will be going through the front, this just scavenges the air that was going over the roof? If it was detrimental to the cooling of the car, then surely they wouldn't have done it with the A9x?
As for what you guys are saying with the rubber, fair point, its not something I would have thought of Hatchman. The rubber is missing from the car so it doesn't matter anyway, hehe.
Anyway, I spent a few mintues fiddling around and gave it a gap of about 1/2-3/4 of an inch. Had to play around a bit to get the bonnet to sit down nicely again because the hinges are a bit nackered but I think its o.k now.
Cheers,
How will this affect the flow of air through the radiator, surely the same air will be going through the front, this just scavenges the air that was going over the roof? If it was detrimental to the cooling of the car, then surely they wouldn't have done it with the A9x?
As for what you guys are saying with the rubber, fair point, its not something I would have thought of Hatchman. The rubber is missing from the car so it doesn't matter anyway, hehe.
Anyway, I spent a few mintues fiddling around and gave it a gap of about 1/2-3/4 of an inch. Had to play around a bit to get the bonnet to sit down nicely again because the hinges are a bit nackered but I think its o.k now.
Cheers,
#14
_devilsadvocate_
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Posted 03 May 2006 - 01:34 PM
Interesting points ^ Dr Terry.So if you lift the bonnet at the rear, air will exit at low speeds (10-30 km/h), because of the action of the engine fan, but as you build up speed, the pressure will increase & air will ENTER the underbonnet area.
The aerodynamics of whats happening is obviously tricky depending on speed, fan and airflow.
On my own vehicle(with clutch fan) the rubber strip was missing(spray painter didnt put it back!) and I was getting very hot air out the vents at suburban speeds, up to 60kmh, a thermometer placed in the plenum chamber revealed underhood air was definitely flowing out. I didnt actually see what was happening at higher speeds b4 the prob was fixed.
#15
Dr Terry
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Posted 03 May 2006 - 02:43 PM
Hi Again.
The A9X is a good example of what has been done by the factory.
Remember that a stock road going A9X should have a plate to block off the air hole. These plates were introduced after the cars left the factory, when the problem was found. I think from memory they used the excuse of water entry. If it just has a standard air cleaner & the hole is left open, you most certainly will an overheating issue at speed.
When the scoop & hole are utilised on the track, a cold air box if fitted around the carby & sealed to the underbonnet with foam. This way only cold air enters the carb & the air flow thru the radiator is not reduced.
It's amazing how increasing the air pressure under the bonnet has such a huge effect on the radiator air flow. Undertray & spoiler & radiator air intake design is one of those areas that has improved greatly on late model cars
Dr Terry.
The A9X is a good example of what has been done by the factory.
Remember that a stock road going A9X should have a plate to block off the air hole. These plates were introduced after the cars left the factory, when the problem was found. I think from memory they used the excuse of water entry. If it just has a standard air cleaner & the hole is left open, you most certainly will an overheating issue at speed.
When the scoop & hole are utilised on the track, a cold air box if fitted around the carby & sealed to the underbonnet with foam. This way only cold air enters the carb & the air flow thru the radiator is not reduced.
It's amazing how increasing the air pressure under the bonnet has such a huge effect on the radiator air flow. Undertray & spoiler & radiator air intake design is one of those areas that has improved greatly on late model cars
Dr Terry.
#16
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Posted 05 May 2006 - 06:06 PM
So what are you saying Doc, that the gaps doing more harm than good and I should put it back down?
If thats the case, seems a lot of ppl are driving round with something that is pointless.
Peace,
If thats the case, seems a lot of ppl are driving round with something that is pointless.
Peace,
#17
_brett_32i_
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Posted 05 May 2006 - 06:35 PM
i was thinking that these would be best left on, and have a sheet metal tray joining both of these flashings, to the bottom of radiator and top of crossmember, so it keeps the area behind the radiator as a low pressure area??If you've got those stone guard things fitted inside the front engine bay area, then take them off, It'll allow a lot more air to enter the engine bay from underneath and from the sides. This helps reduce heat in the engine bay.
does this sound right doc?
#18
_jabba_
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Posted 05 May 2006 - 10:07 PM
Over time the gap at the back of my bonet has creaped up, id say this is the case with alot of peoples cars and maybe they dont know to adjust them or it doesnt bother them?
#19
Dr Terry
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Posted 06 May 2006 - 08:49 AM
Hi Guys.
Liam said
"So what are you saying Doc, that the gaps doing more harm than good and I should put it back down?
If thats the case, seems a lot of ppl are driving round with something that is pointless.
Peace, "
Absolutely correct Liam.
There was an article in AMC a few issues back about a guy drag racing a 351 XW or XY in the early 70s. I think Fife was his surname, anyway his car was one of the front runners, so when he tried something new, a lot of people noticed & a lot copied him. He went to one particular meeting with the rear of the bonnet jacked-up 2" or 3", which he (admittedly) did for the heck of it, no improvement, no scientific reasoning, no testing, nothing. People thought 'what's this ? better underbonnet airflow, better aerodynamics' he had them all thinking. But he just did it because he thought it looked good or maybe different or just for the 'stir'. His times were no better, it ran no cooler, but even in those days he was still only running the motor for a few minutes per run. The car didn't really run for long enough to tell if it was any better (or worse) in this area. Next meeting every 2nd car had their bonnet jacked, they all thought if it worked for Fife it will be good on my car too.
Unfortunately this is how a lot of mods are done. If you ask an owner why he fitted something this way or that way, or why did he change it to this, their answer is usually because they thought it would look could or a bloke at work (or the pub) said that's how it's done. The manufacturers spend millions doing testing on every part of the car, sure they don't get everything perfect, especially in the early years, but many modifications you see, dont make the car go any better, but they usually make the owner/driver feel a lot better.
Dr Terry.
Liam said
"So what are you saying Doc, that the gaps doing more harm than good and I should put it back down?
If thats the case, seems a lot of ppl are driving round with something that is pointless.
Peace, "
Absolutely correct Liam.
There was an article in AMC a few issues back about a guy drag racing a 351 XW or XY in the early 70s. I think Fife was his surname, anyway his car was one of the front runners, so when he tried something new, a lot of people noticed & a lot copied him. He went to one particular meeting with the rear of the bonnet jacked-up 2" or 3", which he (admittedly) did for the heck of it, no improvement, no scientific reasoning, no testing, nothing. People thought 'what's this ? better underbonnet airflow, better aerodynamics' he had them all thinking. But he just did it because he thought it looked good or maybe different or just for the 'stir'. His times were no better, it ran no cooler, but even in those days he was still only running the motor for a few minutes per run. The car didn't really run for long enough to tell if it was any better (or worse) in this area. Next meeting every 2nd car had their bonnet jacked, they all thought if it worked for Fife it will be good on my car too.
Unfortunately this is how a lot of mods are done. If you ask an owner why he fitted something this way or that way, or why did he change it to this, their answer is usually because they thought it would look could or a bloke at work (or the pub) said that's how it's done. The manufacturers spend millions doing testing on every part of the car, sure they don't get everything perfect, especially in the early years, but many modifications you see, dont make the car go any better, but they usually make the owner/driver feel a lot better.
Dr Terry.
#20
_Keithy's_UC_
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Posted 06 May 2006 - 09:17 AM
Just noticed this thread guys...
I agree totally with Dr. Terry. A test performed on a R33 Skyline in Japan in late 1998 showed dramatic rises in engine temperatures and substantial increases in fuel consumption over a 300km period. Only a small thing can have such a huge effect!!
FYI, the skyline was worked and it was a Jap magazine my mate sent over to me. IIRC it went from an average of 10l/100km and average temp of 85degrees celcius to 11.25 (or thereabouts)l/100km and the temp went up by over 8degrees celcius.
I'll try and find the article!
If its power you want, its a proven fact that the hornet scoop is the most effective bonnet scoop you can buy.
If its a reduction in underbonnet temps, you need thermal wrapping or ceramic coatings...
If its aerodynamics your after - torana's are like bricks!! No hope there!
Keith
I agree totally with Dr. Terry. A test performed on a R33 Skyline in Japan in late 1998 showed dramatic rises in engine temperatures and substantial increases in fuel consumption over a 300km period. Only a small thing can have such a huge effect!!
FYI, the skyline was worked and it was a Jap magazine my mate sent over to me. IIRC it went from an average of 10l/100km and average temp of 85degrees celcius to 11.25 (or thereabouts)l/100km and the temp went up by over 8degrees celcius.
I'll try and find the article!
If its power you want, its a proven fact that the hornet scoop is the most effective bonnet scoop you can buy.
If its a reduction in underbonnet temps, you need thermal wrapping or ceramic coatings...
If its aerodynamics your after - torana's are like bricks!! No hope there!
Keith
#21
_devilsadvocate_
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Posted 06 May 2006 - 01:37 PM
Its quite easy to see what the gap on bonnet is helping or not at whatever speed you choose. Just put a thermometer close to the gap, if it goes above ambient, its helping, if stays same....most likely air is being drawn in as per Dr Terry's reasoning. As posted b4, I was getting a flow out at speeds up to 60kmh....but never tested beyond that.
#22
_EXLXSL_
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Posted 06 May 2006 - 04:58 PM
I'm with Jabba. Fitted a new bonnet lacing rubber when I changed from a chrome grill thingy between the windscreen and bonnet to a brown one (I mean Persian Sand) and it now sits maybe 25mm higher at the rear. Next time I feel the need for a tinker (sorry) I'll be setting it up flush again as I think it looks wrong. Just have to get around to it.Over time the gap at the back of my bonet has creaped up, id say this is the case with alot of peoples cars and maybe they dont know to adjust them or it doesnt bother them?
#23
_Aidan_
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Posted 07 May 2006 - 02:07 PM
i've never seen the bonnet rubber you guys are speaking of, does anyone have a picture of it?
#24
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Posted 07 May 2006 - 05:47 PM
Found a pic from chaotics post about trial fitting a Nissan V8 into a Torana. Black on green makes it stand out. It's the black strip where the squirters poke up towards the windscreen.
#25
_devilsadvocate_
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Posted 07 May 2006 - 05:56 PM
Yes, that's it. Notice it is only as wide as the plenum grill. It would appear to me its primary function is to stop hot air going down the plenum as i can testify to. Air can still move through the sides.
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