Underbonnet ventilation, can this work

[tvr4ever]

(Please bear in mind I'm Dutch so some of the more technical terms may sound a bit odd and I may have them wrong.)

While looking at options to improve airflow under the bonnet I had an idea. My question is can this work. On top of the bulkhead there is a box, this box contains the wipermechanisme, and maybe more, I dunno. Is it possible to dril holes in this box, below the bonnet, and on top of the box around the wipers underneath the mesh that is on top of the box. You then have a way the hot air can escape from underneat the bonnet through the box and out on top just in front of the windscreen. I guess people allready would have done this if it could be done unfortunatly a search on PH came up empty. I have no idea what else is in the box, maybe the hot air would just be blown into the cabin making that even hotter...

So please let me know if this is just a weird idea or that it can be done.

Cheers Fred

[2 sheds]

Fred
I believe that this is a high pressure area (whilst moving fast) i don't think much air would escape, the serious modders Steve Heath & Peter Humphries would probably be able to give you more info as they have been "down this road" a few times.
The front vent (front top of bonnet) should extract the air. if you are talking about cooling during slow moving & stationary then the vents at the bulkhead would work.
Tim

[tvr4ever]

Tim,

I think that during slow moving and stationary, for example waiting for a traffic light, venting air that way would lower the underbonnet temp greatly. However I don't know what's inside the box, maybe you can drill holes, maybe that's a bad idea. So therefore my question, can you drill holes without destroying something else ?
For all I know water will leak into the cabin...
The other option would be to make holes at he end of the bonnet, the part that's vertical (about 1 inch)right in front of the windscreen, however making the holes in the box would look better, in an ideal world you would not even see them through the mesh that's on top of the box (wiper arms sticking through there)

So please, does anyone have any idea if my idea is just mad, or can it be done ?

Fred

[steve290353]

Fred
i have just been looking under my bonnet and it looks as if you could be onto something here ,the problem maybe that no one else has done it before and its one of those ideas that looks just to simple to work as Tim from ACT said you would think one of the experts would have some idea about it and that would be good, but i am thinking that just because it has not been done does not mean it cannot work regards Steve.

[Heliox]

Hi Fred,

I take it that your car is an early version as the later cars had this modification which included the bulkhead being sculpted out to allow air venting through the mesh grille, Griffith evolution.

regards

H

[simpo two]

I guess it depends on whether you want to lose heat when the car is stationary, or moving - this is not clear.

[tvr4ever]

Thanks guys for the info so far. Mine is a 1993 4.3 with cat. I have no idea if the later cars are different from mine. Maybe if someone has a photo of how the newer Griffiths have this sorted they could email it to me, or show it here. The cars I have seen so far (not that many in our Dutch club..) all had the same "box" thingy like mine. I didn't realise but a lot of people will have gone to Le-Mans I guess. So maybe after the weekend someone could tell me if it's ok to drill holes in the "box". At least the fact that people don't say right away it's a mad idea gives me hope, maybe it can be done.

Fred

[david beer]

Here is a "wacky" idea. A water stat that opens at say, 72,means that when the fans are on it fans the underbonnet with at least 72c air ! What if the water stat was a 88 which meant it was open, close,open close etc. There is no way the engine can run at 72(unless its winter when it not required). If the water stat was to control the engine temp, you could actually fan the engine bay with cold air, as the water stat has closed! Its so wacky i have been doing it for 3 yrs, just like my Rangie. However, if you were to remove the 1 inch lip of the bonnet it would help with stationary cooling. Its not rocket stuff, most cars have the water stat control the temperature, you just have to accept that a RV8 without the huge cooling fan(Rangie), has to have some fan cooling.You most certainly could not just pop a 88 stat in without having some cooling fans earlier. I have completely variable fan speed, depending on temperature, but its slightly "OTT".

[tvr4ever]

By now everyone should be back from Le-Mans. Is there anyone who can tell me what's in the box and if you can drill holes in it.
Please fellow PH people, everybody I asked over here had no clue if my idea can work.

Cheers Fred

[GreenV8S]

You'd need to confirm what's behind the panel you're talking about, but I guess its similar to the S and if you did that on an S you'd basically be connecting the engine bay to the cabin, which is a big . If you want to get rid of the hot air from the engine bay, putting a big hole in the bonnet is the simplest way. I've just done this on my V8S and the impact is phenomenal, I also remember seeing a very nicely modified Griff at Zolder with a big TVR logo cut into the bonnet. You going to be at Zolder this year?

[rolfe]

I reckon this mod has real potential for my 4.3BV. I have also looked at my mates 5oo and this modification has been done by TVR to this series.You can actually see a picture of the vents on the 500 in the steve heath book under wiper mechanisms. Having looked at my own car modifying the back return of the bonnet seems to be by far the easiest route.

[Guillotine]

mines a '94 500 and it already has a small hole (20mm) in this box to access the wiper mechanism. as is said previously, this box connects to the blower system and if the hole is left open you get fumes in the cabin!
so it won't work on my griff which is of a similar age to yours being one of the early 500's.

[also thought about this mod earlier ]

[tvr4ever]

Peter,

Unfortunatly I can't make it to Zolder. Having read the answers I reckon I'm just going to make small holes in the end return of the bonnet as Rolfe suggested. I did see the German (I think) Griffith with the TVR logo in the bonnet, personally I thought it looked awfull, to much kitcar to my likings. It ruined the beatifull clean line of the car.
I'm not the most handy person in the world ,and should after drilling the holes it turn out that it was a big mistake, I won't be able to mend it propperly.
So thanks everyone for their thoughts and suggestions, now it's time to make holes in the return of the bonnet. The only thing I'm looking for now is some nice material to finish the holes I'm going to make. Maybe something like the Leven windscreen air vents, makes the holes look a bit better. (matter of opinion offcourse..)

Cheers all

Fred

[david beer]

Try running with the bonnet up one inch, you will see a big difference. It might give you confidance to remove parts of the rear lip, it would only be visable from inside the car. Also make sure the rad is completely sealed to the body, thats to say no air can creep around the side etc.

[Heliox]

Fred,

I seriously looked into every possible way of removing or keeping stable the high engine/ bay temps on the early type bodyshell without having to do the bulkhead modification and few worked, although a few exceptions like exit fan ducts that pump hot air out the front arches at slow speeds,waterweter,the Modwise fan kit and the best one is GET THE ROOF OFF!!!lol

if you do want to still cut the bulk head then get some advice locally on how to repair the GRP properly as the early bodyshell used this bulkhead for the screen demist and it needs to be sealed, its a lot of work too.

h

[2 sheds]

Yes removing part of the rear bonnet lip would probably be the best idea, agree with david about lifting it a tad first 1/2" would do, just to see the difference.
Tim

[Boosted Ls1]

I tested a TR8 with wool tufts and found that in the centre of the bonnet lip it was a high pressure region and air would enter into the engine bay. However, there was low pressure as you moved outwards. So you could probably extract hot air quite successfully just by removing some of the outboard rear lip or rubber sealant (if you have any). Tufting will tell you exactly what's happening and allow an informed decision to be made. You can do this with splitters and bumpers as well

[Guillotine]

also thought of the rear lip on the bonnet.

this forms a MAJOR part of the rigidity of the bonnet.as the bonnet is only fixed at one side point, and considering the pressure differencial, see boostedlsi post, that the likelyhood was that the bonnet would split

so when removing the strip you also need to add a brace to the lower edge. wood/steel glassed into it is the usual course for this, but i think a job for the professionals. ££££££££££££££'s

a possibility on front end respray but other wise i doubt it.

i heard of a guy who drilled equally spaced hole across the lip...made no difference.

cheers

BTW if you come up with a way...i'm listening.
Zertec F40 scoops would work (they've done it on a cerby) but don't quite work IMHO

>> Edited by Guillotine on Tuesday 15th June 22:06

[tvr4ever]

Great, more reactions, I love PH. I have decided to make slits in the back return of the bonnet. I'm thinking of making them about 18 x 65 mm. about 4 or 5 of them would fit. It leaves enough of the stability of the bonnet intact and should help vent the hot air. I allready have David's excellent 2 speed fan mod and waterwetter, wrapping my manifolds as we speak. All of these measures should keep me trouble free during our holiday to Italy. Last year Davids (heatresistant)controlbox melted, he replaced it free of charge for an aly one, this year after all my mods things will be different.
A mate of mine has a car repair firm (bodyshop ??) and he has agreed to help me, maybe this weekend. I will keep everyone posted.


Thanks guys for all your reactions.

Fred

>> Edited by tvr4ever on Tuesday 15th June 22:31

[Boosted Ls1]

Fred, I haven't seen a TVR bonnet so don't know how strong or weak it is but before you slot it, it would be easy to 'tuft' it with wool and get the slots in the right place. Otherwise you may make them to big Anywhere towards the outside corner/edge will probably be good.