Will open side pipes run cooler?

[grybrd123]

Hi:

In my never-ending quest to reduce engine compartment heat in SPC 123, I am considering opening up my side pipes. I have been running the H-pipes out the rear, but think that opening the side pipes should make the exhaust manifolds run cooler because of reduced back pressure. At least initially, I would just leave the H-pipes in place until it's convenient to remove them. On the other hand, could the manifolds run hotter owing to increased exhaust flow?

Opinions, advice? All ideas welcome ...

Cheers!
grybrd123

[Excaliber]

Might help some, but it's not going to do much. Do you have the engine bay area FAN that the Coupes usually come with? That helps a bunch!

Some of the Coupes did have a problem with a melting relay that turned that engine bay fan on and off. If your doesn't work, check the relay (30 amp if I recall).

[grybrd123]

Thanks for replying. Yes, I have the engine bay fans, and they have been reversed to blow up so they are operating in accordance with physical law (that is, hot air rises). I just want to make the engine bay (and engine temps) as cool as possible. I like the rear exit pipes, but all those bends, plus the extra pipe length, seem like they must increase exhaust back pressure and therefore heat.

grybrd123

[Excaliber]

Well plenty bend in that exhaust system alright!

In spite of the laws of physics regarding heat rises I would think forcing the air DOWN would still be better. The rising air may remain trapped under the hood and mostly recirculate through the fans. Unless there is some directive from SPF to do otherwise, I'd suck the air out and push it under the car myself.

[Rare Iron]

Chrysler tried running a Viper with straight pipes in their development & the engine ran about 30^ hotter & lost HP. They installed mufflers after the car cooled down & everything came back into operating range.

[rcweingart]

I changed from the rear exit H pipes to open side pipes and believe that my engine compartment is cooler although I do not have data one way or the other. I personally like the sound a lot more and do not find it to be much louder. Elimination of the rear exhaust allowed me to install an belly pan all the way to the end of the rear wheel compartment for increased aerodynamics if you're interested in pushing the speed envelope. As for my engine compartment fans, they came from the factory pushing the air up through the hood vents which is my understanding of how they work. Dennis Olthoff suggested, and I took his advice, to disconnect the engine compartment thermo switch compartment and simply use the dash switch to turn the fans on in traffic. Apparently they are not needed when the car is in motion. Others have relocated the switch to a much lower location to keep the fans from running on and on and on after the car is shut off - one of the other reasons Dennis disconnects the thermo switch.

[Excaliber]

Another reason for disconnecting the thermo switch is they tend to "melt", those fans pull a lot of amps and the switch overheats.

[Rick Parker]

Aren't they run through relays?

[rcweingart]

I've never heard of the thermo-switch melting; and, yes, as I understand it, the fans are run through a relay.

[Excaliber]

Let me clairify. It's the RELAY itself that tends to overheat and burn out. I believe it's a 30 amp rated unit and there not that easy to come by.

[Rick Parker]

Get a Relay capable of carrying more current......Auto electric 101! You can get practically any automotive electrcal part overnight at most major auto parts stores.

[PANAVIA]

There are AC relays that transmit 65-70A -- dont forget to increase the gauge of the wire.

These are found in lincolns and trucks as a Glow plug relay or various.



there are enough 50A to 70A applications that you should be able to find something that will work.

http://www.omega-usa.com/client/imag...y_Switches.pdf

Remember , anytime you are moving a buck-load of amperage you are creating heating elements at the same time.

be careful and make sure you have protection for the circuit.

better to have an temporarily overheated car than a wiring fire/meltdown.

Steve

[Alan G Davies]

I have an engine bay fan which operates manually with the second radiator cooling fan via a relay. It works well, it cools the car down in the pits after a run along with the elec water pump.
Alan

[rcweingart]

I run my engine bay fans (there are two of them) via a toggle switch on the dash and my relay doesn't melt. It is capable of handling the electrical load. The relay is switched by either the dash toggle switch or the engine bay thermo-switch so it is irrelevant how it is switched. Either way, the relay is adequate and doesn't melt. I might also point out that I ran my engine bay thermo switch in the circuit for a a year or so without relay or thermo switch problems before disconnecting the thermo switch because I was tired of the fans running for a long time after the engine was switched off.

[Excaliber]

There are several different factors that may cause a relay to overheat, depends on the car. Point is, those fan can suck up a lot amps so you need good clean tight connections at all times.

If that 30 amp breaker keeps tripping at your house would you pull it and stick in a 50 amp so it would stop tripping? I wouldn't recommend it.

[Woodz428]

Originally Posted by Excaliber

Well plenty bend in that exhaust system alright!

In spite of the laws of physics regarding heat rises I would think forcing the air DOWN would still be better. The rising air may remain trapped under the hood and mostly recirculate through the fans. Unless there is some directive from SPF to do otherwise, I'd suck the air out and push it under the car myself.

The only reason the fans were wired that way was to lessen the possibilty of picking up debris. That is all well and fine, however, you are attempting to pull the hot air down. What that creates in the way the Coupe is set up is the hot air is then pulled over the heat sensor and causes it to stay hot, while the engine is running the heat never subsides and it causes the thermo switch to stay on. That in turn causes more hot air to be pulled over it and ultimately melts the switch. Again, it defies the laws of physics, and very poorly I might add. I reversed mine when I realized that it was doing that, and they now cycle. Before, and I only have had them kick on a few times, the fans would continue to run until the engine had cooled off, opening the hood after shut down was the only way to shorten their run time.
As far as the side pipes, some people are running them open and I believe that SPF as well as BRE offer open side pipes. I can't speak with any first hand knowledge of those but doubt that (opening them) would lessen the underhood heat much with the factory pipes. The baffles, it would seem, are the big obstacles in the heat flow from the engine. So it seems unlikely that you could reduce the temp that much by just opening the stock pipes.

[rcweingart]

Here's Peter Brock's thoughts about the fans and open side pipes vs. rear exit exhaust:

The twin rad fans are designed to suck air through the radiator (in the same direction that the air naturally flows) In at the front and up and out over the hood. Having the fans reversed from the factory is a common quality problem that should have been caught by the installer. Note the skid plate fans are designed to blow air DOWN and suck the heat out of the engine compartment. If you reverse these to suck air UP (as one might think this the natural flow of hot, rising air) all you'll get is lots of dirt in the engine compartment and very poor cooling, as there's nowhere for the air to escape! Except the side and hood vents and they aren't hat efficient.especially with the screens in place.

(r)ear exit exhaust *** constricts the exhaust flow and keeps the heat up front. *** (Open) side exit exhaust *** get(s) rid of all the back pressure and heat caused by a tailpipe system that's poorly engineered. (not to mention the poor ground clearance) The "S" pipes that lead from the sides to the rear actually decrease in diameter which restricts flow and retains heat. A proper rear exit system could be devised but the cost to make a proper system, with constant area "S" pipes and larger tail pipes just isn't economically feasible. I've tested cars with rear and side exits and there is NO difference in DB levels once you are on the road. Start-up is louder with side exit as the pipes exit right under you window. But once moving ..no difference.