Heat management

Hi everyone -- I recently bought a '98 Berlinetta (I'll do a separate intro thread once I have it home) and one of the first things I'd like to tackle on this otherwise beautiful 355 is reducing engine compartment heat. It seems like it'd be pretty easy to mitigate the problem with heat blankets on the exhaust.

My car has stock headers and cats and a Fabspeed muffler (that I'd like to replace with a stock muffler, in case anyone wants the Fabspeed). I am probably going to replace the cats right away with aftermarket 200-cell metallic core cats (if you have a pair for sale, please PM me). While doing so my plan is to wrap the cats with 1/2" thick heat blankets and wrap the headers from the union with the cats back to the collector. I would think this alone will substantially reduce engine bay temps. I'm also fabricating heat shields for the trans mounts and improved CV boot shields.

This is the heat blanket I was planning on using -- $125 for a 1'x5' roll. It's not Iconel, but it's also not thousands of dollars, and it's pretty effective stuff.
https://www.amazon.com/Heatshield-Products-176005-Exhaust-Stainless/dp/B0051UPJIC/

I've been an air-cooled 911 guy for many years and do all my own mechanical work, and the F355 is a dream car, but having almost the entire exhaust system (including cats!) inside the unventilated engine compartment is just asking for trouble.

I've done a lot of searching in the archives but haven't seen much about heat mitigation -- would be grateful for any advice or comments from this group that I've learned so much from in reading the archives.

 

I don't, and prefer the non-grille look. Anyone know if there's been testing to see how much it lowers engine bay temps?

 

Interesting. Not nothing...but probably insufficient. Going from a (guessing here) 300F engine bay to 270F probably doesn't accomplish much. And it does nothing for the real problem, which is radiant heat coming off the exhaust. Heat blankets are very effective in this regard.

 

I'm sure it helps, although a passive ventilation device like that I suspect is much more effective in track driving (consistent high speeds and more air circulating in engine bay) than in street driving.

 

I don't have the car in my garage yet, getting the paperwork taken care of this week. It's in beautiful condition, and I want to put miles on it and not feel like I'm frying the engine bay. Plastics, rubber, wiring, and assemblies like alternators are subject to extremely high temps and heat cycling in a 355, and the factory heat shielding is pretty inadequate, so it seems to me that one could take a big step toward improving reliability by getting heat under control.

Yup, exactly. The way I look at it is there's 10 feet of exposed exhaust in the engine bay (call it 5 feet per side). If I can wrap the cats plus the collector section of the headers, that's probably 2-3 feet per side, or 4-6 feet total. So now half the exposed exhaust is blanketed, including the hottest part (cats). By my crude math, that's probably good for a 50% reduction in engine bay temps. I've got an IR thermometer and will be doing before and after tests.

 

One thought I had, purely a mental doodle, was that someone could replicate the heat exchanger design on air-cooled 911's, since the 355 headers/collectors already have tinwork surrounding the exhaust pipes, like a 911. On a 911, the header/tinwork is called a heater box since it's how you warm the cabin of the car. There's an opening in the rear of the heater box, air from the engine cooling fan is pumped in, and there's an opening at the front of the heater box where the hot air, which has now passed over the header pipes, exits and is either dumped out under the car or sent into the cabin.

On a 355 you could theoretically do something similar with a small electric fan at the front providing the airflow. And of course in this setup the air would exit at the back of the collector through the engine grille or below the engine. If a Singer-type company wanted to start redesigning a 355 this would be a cool thing (sorry, bad pun) to try.

 

Yes, good point. It's why I'm not wrapping the exhaust manifolds -- those need all the help they can get (mine are stock). But I figure the collector and cat sections are fine, and the heat that isn't radiated into the engine bay will stay inside the exhaust resulting in hotter exhaust gas temps, which exit where they should, through the tailpipe. Or so the theory goes. I'll know soon enough.

 

Thanks Bob -- am gonna do something like that when the time comes for aftermarket headers, but mine are still good. I'm leaving them alone for now and focusing downstream, as I figure putting blankets on the stock headers will rapidly accelerate them failing.