Exhaust Heat to Turbo

[esinger]

I was reading posts and talking to people about the placement of my wideband O2 sensor and protecting from extreme exhaust heat when it occurred to me that us Hotair cars have more piping from the PS header to the turbo than the 86/87 cars.

For some crazy reason I had been thinking our turbos see more exhaust heat than 86/87 cars, but it seems that it should be the other way around. Our cars should see less exhaust heat to the turbo becuase of the up-pipe.

Am I correct?

 

[BRAD_PADGETT]

I put my wideband O2 sensor on the testpipe right after the downpipe. I ran the wires through the tran shifter cable and into the console. You need to be at least 12 inches past the turbo. Good luck. Brad

 

[esinger]

Hi Brad,

Thanks, but I've already installed the wideband O2 a couple of weeks ago. Found a nice stop about 2 feet down from the turbo.

The thing I was trying to bring up is that I think our turbos should run relatively cooler than the 86/87 location because of the extra piping.

 

[novaderrik]

but you want that heat to make it to the turbo- heat=energy. if it cools down too much, it loses it's velocity thru the pipe, and as such, will turn the turbo with less energy. this is why header and exhaust pipe coatings and wrap can add some power- the heat is kept in the pipe.
in a "perfect" turbocharged application, the exhaust heat at the turbo inlet would be the same as it is when it gets pushed out past the exhaust valve, and would be at ambient air temp when it leaves the turbo after using up all of it's excess energy to turn the impeller. well, actually, in this theoretical "perfect" world, there would be no need to use a turocharger since all the heat created in the combustion chamber would be converted into piston movement, and the exhaust leaving the motor would already be at ambient temp.
but we don't live in anything resembling a "perfect" world, so things like turbochargers are used to harness some of that wasted heat energy and put it back into the combustion process.

 

[esinger]

Thanks for the reply! So because of the lost exhaust heat our cars will not spin the turbo at the same rate as a 86/87 setup giving everything is equal.

So to me that means that on an equal setup (84/85 vs 86/87), we'd have to turn more RPMs to make up for that loss to spin at the same rate. Correct?

 

[Jerryl]

Thanks for the reply! So because of the lost exhaust heat our cars will not spin the turbo at the same rate as a 86/87 setup giving everything is equal.

So to me that means that on an equal setup (84/85 vs 86/87), we'd have to turn more RPMs to make up for that loss to spin at the same rate. Correct?

Correct.
There is also less "energy" resulting from the elevated charge temps.
Look at it this way ............. You add "energy" (Not sure if this is the correct term) with NOS to help spool a big turbo.
So you get the compounded effect of lowered exhaust temps and less "energy" and, you now need RPM's and some high VE number.
Based on some really really rough calcs, you can expect 5hp/1000 rpm.

So you have a WB to monitor AFR, and add an EGT to adjust timing ...... I think