Was having a bit of a blast yesterday and noticed when going above 130 that the bonnet looked like it wanted to tear itself off! Luckily I have pins holding it on but was a little concerned! It\'s a Scoot bonnet which was used on their high speed runs in New Zeland. Anybody else have similar experiences with vented bonnets?
I\'m going to adjust the rake on the rear wing to see what difference that makes as it\'s set about mid-way at present as when going over bumps the rear leaves the road for a brief moment! I think it\'s more down to the suspension though - currently on Zeal Function\'s with 8kg F and 6kg R which is more circuit orientated and standard roll bars although not that hard!
So anybody got any thoughts? I\'m looking into a suspension, geometry setup at a motorsport place for starters but anything I can do in the mean time?
Depends where you have the pins fitted? To the side or behind the headlights? I have mine behind them, and never had a problem with lift, whilst on a private runway. ;)
As for jumping when going over bumps, I would say that the suspension is set too hard. Try softening a little.
The rear wing will only push down at speed, below about 50-70 it doesnt make much difference. IMO.
Fish
my feed one does that with no pins once in the 3 figures & you can stick your hand in. Thats why I was asking about bonnet pins& mot\'s the other day
Moving this to the technical section :)
Sounds like you must be creating an area of low pressure behind the vents in the bonnet to me, that would make it want to lift. Also, what sort of panel gap do you have at the front of the bonnet?
Thanks for the feedback Fish, I have the pins behind the headlights too, but the lift occurs at the sides of the bonnet.Sorry should have been more specific!
Gerry, I\'d highly recommend you put the pins in as you risk too much relying on just the front latch!!! MOT is no probs as mine went thru with them on the last two times.
I tried taking the rain trays out and this solves the problem as it lets the air from the front intakes flow through more eaisly - reducing the front lift.
The rear is a little more probmatic as I personally feel the spring rates are too soft for the FD and I have way too much stroke for my liking too. I\'m going to go for harder springs but retain the OEM roll bars, then by reducing the amount of stroke it should lessen the distance the spring travels, which will stop me bottoming out and loosing the amount of traction over the big humps in the road. They aren\'t crashy in the slighest at the moment and it is very progessive, only when you have the big down, up humps that I have a problem.
Sh!t, imagine that popping up at that speed!!! Ive just had my Scoot style carbon one fitted, yet to fit the pins but I have ordered them. Its back to the bodyshop tomorrow where amongst other things have the bonnet adjusted so not worth putting pins in until that is done. My speeeo isnt working, just come back from a drive - got to about 5500 rpm in 4th (speedo not working so not sure of speed) and no lifting. All on a private stretch of road of course
Quote from: Gerry Mmy feed one does that with no pins once in the 3 figures & you can stick your hand in. Thats why I was asking about bonnet pins& mot\'s the other day
Gerry I have a selection of pins here,
http://www.rotaryart.uk.com/acatalog/Bonnet_accessories.html
have had 2 customers loose theres at speed, would recommend fitting.
I take it yours arent flush ones then ben?
I\'ve had a thought about this after looking at my bonnet, most aftermarket bonnets dont have the rubber sealing strip that a normal one would, which would block off some of the air getting under. I\'m going to see if i can get some square foam to do round the edge with as well as pins
Was on the Autobhan while i was over at the ring and i got scared that the bonnet was shakin that much so i eased off!! Knew i had the pins etc but was still a little dodge!!
Happened to a mate of mine with a carbon hood on his civic... Never got the pins and it flew open on him 1 day... He has them now!! And a new bonnet mind u!
Pins are a must!!!!
Im a bit confused.
Shouldnt there be less pressure in the engine bay since the bonnet\'s vented? Or is it other way round?
Andy, why was your bonnet shaking about even though you have pins?
Cheers guys
Quote from: J.j.Im a bit confused.
Shouldnt there be less pressure in the engine bay since the bonnet\'s vented? Or is it other way round?
Andy, why was your bonnet shaking about even though you have pins?
Cheers guys
Foot to the floor on the Autobhan so i can only assume thats y :)
And it will still shake as they flex alot... I notice if i pull in behind sum1 and draft it move alot...
Andy
No mine are your normal sparco bonnet pins, when I originally got the them I decided against the flush ones because I heard they break - although I don\'t think thats the case anymore.
There should be less pressure if it\'s vented, but I had rain trays fitted which blocked most of the airflow. I still have the plastic surrounds that sit behind the headlights just need a rubber strip to sit along the front edge, I know Blitz do this in Japan at the Autobacs stores, unfortunatly we only have crappy Halfords!!
I think the standard bonnet flexed far less at speed but did cause front end lift as the air flow becomes trapped.
Ben - mine\'s fibreglass and you\'ll always get some flex. Not sure how much bracing yours has ont he underside but we can comapre next pub meet if you like.
Mine flexes some at high speed along the sides - lift about 1". Nothing too scary though and I\'ve had it up to a verified 153 more than a few times @ Brinters and it was no problem. Will have to see how that\'s changed with the new i/c and rad though.
Not that much mate. ;) You\'ll just get there quicker. :D
Fish