Hi Jenko
I had thought about the heating issue the same as you, my cat sits above the rear top rail and some of the pipework is very close to the fibreglass (well until the powerfile gets used anyway). I am considering vents in the top and back above the normal numberplate posistion. Another consideration was to get some cold air in for the t/bs but i didnt want to create "lift" in the lid so the cat holes would become more useful in allowing that channelled air to escape.
Car looks brill by the way.

Nick M

You're gonna need some kind of vent with the cat there Nick. Mines got reflective heat mat and a big vent which seems to do the trick. The cat is also wrapped. I reckon cold air into the TB's or air filter in my case has got to be a winner.

Paul

I have a Westfield exhaust with built in cat it sits parallel to top rail but some way down from the bodywork. It appears to get it's cooling from the forward looking side vents without further holes. It has a lot of ventilation below it as the J15 tub rises in this area. The major problem I had was from the exhaust manifold radiation I had to use reflective heat mat for that area. You just had to put your hand on the tub in that area to find the hot spots.

The GRP/gel coat does not instantly melt, you have lots of time to consider the optimal strategy for your build. Obviously if you do a track day immediately after passing iva then you might want to cut holes all over the place just in case but in reality you can adjust the design to suit the build without damaging the gel coat.

Thanks Fellas
Agree with all the observations and comments, my cat is the sylva one which sits higher and is fatter as well, i am in the process of cutting some of the fibreglass away as my bottem pipe on the left is literally mm away from the lower lip but because of its angle and height from the floor you would have to be lying down to notice it. Adding the strengthening fillets added 2 more pieces of fibreglass to get in the way as well.
Once it can fit where it should i may well have a think about Jenkos front hinged idea but am a bit worried about the strength of the centretub with double hoop cut outs.
I was also surprised at how purposeful and brutal it looks from the rear (in a good way) a few vent holes will be both practical and help the look !

Nick M

Like Paul & Prisoner, I've put in some reflective matting to keep the heat off the fibreglass. Only problem is this also insulates the engine bay and makes it harder for the heat to escape.

I think a vent either above or rear of the exhaust can only be a good thing....Which is what Paul AS has done...and what I'm planning to do also.

The inlet temp I think is also worth looking at, a). higher inlet temps means higher running temp, and b), cooler air is good for power. With the J15, it's most certainly an area worth looking at.

the bottom of the engine bay is fairly exposed, but I have an additional floor pannel on mine that is located just behind the rear bulk head, this was put there to help get some more flat floor area, and also goes some way to protecting the engine bay from road grime. Of course, it probably also limits to a small extent some air flow in the engine bay.

Hi
We all have similar thoughts, i did think of extending the floor at the front and rear for nice smooth air flow but the practicalities of working on the car stopped me, but then that is my reasoning for considering the hinge system that you have fitted. My original thought was to adapt the Sylva bracket so that the male end became a solid pin with a split pin to connect the remainder of the bracket to the the hollow tube - remove split pin then solid pin and remove the whole fibreglass piece but would still pivot on those 2 pins for not such big jobs.
With the winter on its way the question is do i crack on to get to IVA soonest or make those alterations that are bugging me but slows up the on the road time !

Nick M

No no no. Finish the car and then spend the next year redesigning it (like me and a few others I suspect) why be different at least you get to drive it between redesigns!

One duct now in place....Should be able to complete the other on the weekend...see blog. Have to say, They do look very nice, and I found the full real carbon ducts on kitcarsdirect for 64 quid (for two).