This site contains car modification and auto upgrade information specifically for the turbo import Toyota JZX90 MarkII TourerV, however the principles applied here can be mostly utilised regardless of the make or model of motor vehicle.
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Bonnet Venting 18/3/2005
The purpose of venting a bonnet is obviously to release the hot air from the engine compartment, so the larger the vent is, the more effective it is likely to be. I have seen plenty of tacky little vents around but I wanted something substantial, and Jetspeed came to the rescue with this fine specimen you see here.
The first thing to do after getting it home and admiring it, is to test fit it to the bonnet. Now since this vent actually recesses into the bonnet we can't get an exact idea of whether it will sit perfectly flush or not, but usually there is a bit of flex in fibreglass so that is not a problem. This particular vent is designed for a Nissan Silvia S15, but it seems to fit quite nicely on the MarkII bonnet.
It is important to ensure that the vent is placed correctly as its prime purpose is to release the hot air from the radiator. It is necessary, therefore, to lift the bonnet and measure the distance back to where you think is most appropriate for the venting to start. In my case the vent sits a little further forward than it perhaps would on an S15. Mark out the placement of the vent with a permanant marker. I used a red CD pen but since the paint colour is very dark it was hard to see. Some sort of permanant white marker would have been ideal.
Then remove the bonnet (in my car I have a spare bonnet so removal was uneccessary at this stage), and place the vent in the position that you marked out prior to bonnet removal. Measure the distances of the vent from all sides of the bonnet. There is nothing worse that finishing the job and realising that the vent is slightly askew.
Once you are certain the bonnet vent is perfectly placed, trace its outline with your marker pen. Then remove the vent and mark another outline a reasonable distance inside this line. This distance will depend on how much level surface there is on the vent before it begins to recess. In my case 40mm was a good distance. You wouldn't want to reduce this by much more than this.
Cut out the metal using and angle grinder with a metal cutting disc. Dont be too agressive with this step as it is easy to heat the metal too much and warp the bonnet. I took three passes to cut through, allowing it to cool in between by beginning on other sections of the bonnet. You will notice from the picture here that I didn't cut all the way through the supports. I did this in order to provide more support for the vent if it turns out the bonnet becomes too weak and flexible. Once the hole is cut out, ensure that the vent fits without fouling anywhere. I had to trim the supports in a few places to enable the venting to drop in completely.
Once you are certain the vent fits nicely, it is time to drill some holes for screwing it down. Alternatively if you are planning to immediately graft the vent in, some appropriate adhesive would be used. The vent I have already has holes so I just drilled through the bonnet with the vent as a template and then used self-tapping screws to hold the vent in place. It is probably advisable to trim off all the dags and burrs in the metal of the bonnet before screwing down, but I was too lazy (or hasty) on this day and neglected to do it. For a firm fit, use Sikaflex or equivalent to provide some adhesive blobs around the underside of the vent where it will come in contact with the bonnet. Use plentifully in the gaps between the vent and the supports. This will help considerably in remain bonnet rigidity.
Use a can of paint that matches your car colour to touch up the spots
where there is bare metal showing. I just used some flat black acrylic
paint and also painted the whole underside of the vent at the same time.
Place bonnet back on your car and admire the handiwork.
In the next picture if you look closely you can see some gaps between the vent and the bonnet. These can be closed up by slightly elongating the holes in the vent, allowing the vent to sit completely flat. Initially I drilled the same diameter hole throught the vent and bonnet, and it is very difficult to be precise as the drill bit can move very marginally and the effect is what you see in this picture. Using a slightly bigger hole for the vent, or and slightly elongating it will resolve this.
My initial testing surprised me a little. I generally run underbonnet temperatures in the 60-80 degrees celsius range (once the car is up to temperature), and on a hot day, or with spirited driving (read "drifting on an Initial Drift day") the temperature can rise to above 90 degrees! This temperature is measured by a temperature probe that is mounted just above the inlet manifold.
On my test day the temperature was reading 34 degrees. As I drove off, I surprisingly noticed the temperature DROP considerably to 22 degrees in a short few moments. After warming the engine up and then subjecting it to a series of aggressive accelerations the temperature did not rise much above 40 degrees. So the benefit is in the vicinity of 40 degrees cooler under bonnet temperatures. This has clearly been a very worthwhile mod. And it also looks mean to boot.
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RECENT MODS CHRONOLOGY
5-Jan-2007
Turbo pages and Headlights
I have recently added a new page about my single turbo conversion. There is a second page yet to come, but page one outlines some of the supporting components needed as well as the turbo itself.
Page 2 will be forthcoming where I detail the fitment of the turbo, manifold and wastegate.
I have also added a page for modifications to my headlights that should be very useful for owners of import vehicles.
25-Jan-2007
Site Revamp
Wow, it has been a very long time since I worked on the site, but now I
am in the process of redesigning it so stay tuned as I add some more content
and attempt to bring this project up to date.
18-Mar-2006
Car Changes
Lots has happened since my last update on upgrades to the car. For instance
the car is now running a 2JZ bottom end and the gearbox has been completely
rebuilt with a stage 1.5 shift kit, beefier clutches and a 2800 rpm stall convertor.
To say that this has transformed the car is an understatement. The car is now
torque heaven, and is an absolute pleasure to drive. The lag that was sadly
felt with the 2.5L motor is now completely gone with the 3L and the stally.
When I can find time to update the site with the process I went through I will
do so. I have many hundreds of pictures to add.
Whatever your vehicle is, whether it is a turbo car or NA or a Toyota or other manufacturer, I hope that the automotive information on this page is of benefit to you as you take the path of modification and upgrade on your car.
Toyota JZX90 MarkII TourerV.