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Esprit Bonnet Catches At High Speed! - Interior/Exterior/Lights/Glass/Alarms/ICE/HVAC - The Lotus Forums #ForTheOwners Jump to content


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Guys got an interesting question to post. What speeds are the Esprits tested too as ever since mine has had its engine modified at speeds hitting 170 (ish) on the GPS/ off the scale on the clock my bonnet suddenly pops open!!!

Scared the crap out of me the first time as one would think the the direction the bonnet opens it would stay down? I guess its to do with aerofoil basics and low pressure on the topside of the car that it opens? However my question being it is impossible to lift my bonnet open at standstill so what type of forces are acting on the car at these speeds and am I the only one to suffer this?

If anyone could shed some light it would be appreciated.

These speeds by the way were not done on the public highway, and I do not endorse speeding of any form....erm Southern hoon guys shut it!!!

Waynef

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Hiya Wayne

Same happened to me. First, when the bonnet starts to lift, the cabin light comes on, as the bonnet does not push down on the switch anymore.

It pops open on the right side at 220 Km/h

In my case it only happenes with the lights up.

Since I work in the aviation field and knowing about aerodynamics, I was able to identify the cause and you are spot on.

When you have the lights up, the laminar flow over the car creates a higher lift (suction effect) and the right side hook cannot hold the bonnet anymore.

This is caused by insufficient leverage of the long rod which works the right hand hook. This rod is too thin an it is twisted as you close the bonnet.

The holding force is not enough and the closing bar is litterally pulled out of the hook.

In my opinion there are only 2 solutions

1. Use a higher diametre rod which transmits a higher leverage or

2. Redesign the hook and give it more curvature which follows further behind of the closing bar.

I would prefer the 2nd option as it seems an easier mod.

For the moment I can live with it as it only happenes with the head lights up and I do not need to go faster than 220 at night, but I agree that it is very annoying and it scares the living shit out of you the first time it happens.

Cheers

Stefan

Edited by USAndretti42
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You are spot on.

Yes it is when the lights are up and always on the right hand side of the car. I guess Lotus somewhere must have a maximum speed then for pop up lights usage it would be interesting to know what this is.

Thanks for the info, I guess ALL ESPRITS do this then even the V8's?

Thanks

Waynef

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Same happends to me also....It scared the shit out of me also the first time....

Did happend above 200kmt with headlamps up.

I did adjust the hood and clamps.And after that it did not pop up anymore.

89 Lotus Esprit Turbo S

Very fast road and trackday car.

GT3076R+ a lot of other modifications.

http://lotusespritwo...inZzdningz.html

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LOL had that happen to me as well - the bonnet wasn't latched and at 50mph it flung open !

Que the brown pants !

There's plenty you can do to stop it - instead of the normal catch you could replace it with a sliding bolt, still use the same mechanism but remove the hooks and put a loop of metal in there, the lever would then operate a cam which slid the bold in and out. As long as it's onto the fibreglass well - it'll rip that out before breaking the bolt.

The other thing is have you looked at some of the remote locking devices poeple fit to things like Elises and Esprits for the rear boot incase the cable breaks ? That would give you a double locking mechanism and take the strain off the original.

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Hi John / hi all

No, I never had looked at this, but it seems to be an idea worth looking into.

I also had the bonnet adjusted, helped to treat the symptoms ab bit but never really removes the cause.

Since all Esprits seem to suffer from this, it would be worth a try to get one of the specialist garages or parts businesses invest in redesigned catches(hooks)

I would be even willing to ask a close friend who owns a CNC machine shop to do the redesign and we offer it through LEW ?!

What do you all think ?

Waiting for your comments

Stefan

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Once I was going 187 thousand miles per second, and I thought ..........just for a second..............I started to see the right side of the bonnet getting ready to unlatch...........but then I turned into pure energy.........anti matter so to speak.

WTF..............were are you guys going almost 200mph?

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Hey Kenco fair comment there by the way.....not on the road if thats what you think??? lol

Jonathan...i'm glad you have had it happen too as it really does take you by surprise. It would seem that the catch is likely to go at any speed above 110 mph (ish) with the lights up. I think I am going to look into having the catches re machined as Stephan has highlighted.

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Once I was going 187 thousand miles per second, and I thought ..........just for a second..............I started to see the right side of the bonnet getting ready to unlatch...........but then I turned into pure energy.........anti matter so to speak.

WTF..............were are you guys going almost 200mph?

Sorry for you mate, but this is not the US with a copper behind every tree to make you behave :-))))

This is Germany with still (fingers crossed) no general speed limit on motorways !!

And yes, we are going 150+ miles/h for as long as not bloody lorry pulls out to overtake and you are in the brakes until they glow :-((((((

cheers

Stefan

Hey Kenco fair comment there by the way.....not on the road if thats what you think??? lol

Jonathan...i'm glad you have had it happen too as it really does take you by surprise. It would seem that the catch is likely to go at any speed above 110 mph (ish) with the lights up. I think I am going to look into having the catches re machined as Stephan has highlighted.

Hiya Wanye

I will have a go at some redesigned catches and try to have some made for myself. Should they come out alright and work, I'll let you all know.

cheers

Stefan

Mind if I cut in ?

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200 mph

no problem in the netherlands either

on the open road at night

but with a little friend that makes sounds (to help me keep my drivers licence)

never had any problems with the bonnet releasing

rens

Edited by rens914

researche is something i do when i don't know what the hell i'm doing

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Are you sure your bonnet mechs aren't just old and worn and therefore not latching correctly?

I've Vmax'ed both of my V8s in the past (when they were new) neither showed any sign of lifting the bonnet even with the lamps up.

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Hi Graham

Its not worn its poor design!!! The bonnet catches are extremely strong its the catch mechanism. As I think Stephan said the only way round this is to use a larger diameter bar. The catch operated by the lever is only attached via a push fit which in this case is not strong enough for its purpose.

Stephan let me know how the catch goes also let me know if your up for the Nurburgring in September?

Be a good speed test plus fun day out.

Waynef

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Hi Graham

Its not worn its poor design!!! The bonnet catches are extremely strong its the catch mechanism. As I think Stephan said the only way round this is to use a larger diameter bar. The catch operated by the lever is only attached via a push fit which in this case is not strong enough for its purpose.

Stephan let me know how the catch goes also let me know if your up for the Nurburgring in September?

Be a good speed test plus fun day out.

Waynef

Hi Rens, glad to hear some continental response in terms of speed :-)))

Wayne, I try to make it to Nuerburgring in Sept. since it is only 1h drive away.

My main restriction is time, as I am travelling alot for my company.

When exactly will you be there ?

Hi all

As Wayne pointed out correctly it is the poor design of the catch not leading around the bar, but rather staying in a horizontal position, from where it is pushed back

to release, as soon as the bonnet starts to lift where the low leverage of the right side rodding can't hold it anymore.

I have done a course sketch so you know what we mean.

Stefan

Mind if I cut in ?

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I've heard from a knowledgeable source...

The Esprit has been tested at High Speed (Nardo) with the Headlamp Pods both in the Lowered and Raised positions.

This was done on the Nardo circuit at an average speed of 282 kph (175 MPH).

On parts of the circuit the vehicle speed is in excess of 290 kph (180 MPH).

The Bonnet and the catch adjustment is critical to ensure location of the bonnet at high speeds.

On various Models tested we found that the R/H catch on LHD (Airbag Option Interior) was the most sensitive to adjustment.

The catch rods are adjustable and the position of the Bonnet / Catches (fore and aft) is important to ensure correct location in the latch.

There was a running change to the design of the Latch Disc which was introduced in early 2002 to make the adjustment / catching better.

This is specified in the Esprit Service Parts List Section 10.09 The updated design is similar to the suggestion of Stefan Ertler (Fandango) who has posted his update.

The part number of the updated part is B082U7149F - this replaced the old part A082U7149F.

88 Esprit NA, 89 Esprit Turbo SE, Evora, Evora S, Evora IPS, Evora S IPS, Evora S IPS SR, Evora 400, Elise S1, Elise S1 111s, Evora GT410 Sport

Evora NA

For forum issues, please contact the Moderators. I will aim to respond to emails/PM's Mon-Fri 9-6 GMT. 

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Now there's service for you!

Possibly save your life. Check out this website.
http://everyman-campaign.org/

 

Distributor for 'Every Male' grooming products. (Discounts for any TLF members hairier than I am!)

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checked all the catches and all seem to be tight only thing I have noticed is the catch does not engage as far as i'd like it too.

Will look at getting in the footwell this weekend to sort it out.

Thanks for feedback guys but I still think I will need the newer or uprated catches.

Waynef

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checked all the catches and all seem to be tight only thing I have noticed is the catch does not engage as far as i'd like it too.

Will look at getting in the footwell this weekend to sort it out.

Thanks for feedback guys but I still think I will need the newer or uprated catches.

Waynef

Thanks Bibs, great research. I had my catches adjusted at least twice,but the problem remained.

I will take a look at the catches with the new part No and then decide wether I persue with my own ones or go for the updates ones

I'll let you know

cheers

Stefan

Mind if I cut in ?

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