So after letting the car idle for a few hours yesterday to make sure everything was OK on the fuel system before getting her off the lift, I decided to do it again once more today and gather some data.
(fuel system pics here: http://forums.corvetteforum.com/show....php?t=1403280 )

I gathered temperatures off the fuel rails, intake manifold, exhaust, fuel pump, braided stainless hose, gas tank, and coolant hose (not the coolant temperature as reported by the DIC, I wanted to get the radiant heat only). For an hour, I gathered these temps with the hood open every 5 minutes using an infrared, non-contact thermometer. It can take temperatures +- 4% in .5 seconds from up to 2 feet away, although it recommends 3-12 inches away. For the next hour, I gathered temperatures every 15 minutes (starting after sample 12) and had the hood closed. I did this in my garage with the garage doors open half way and fans blowing exhaust gas out the doors. Ambient temps were about 89 degrees when I started and about 95 degrees when I finished. There's a CO monitor in the garage.



I noted a few interesting things. First, the intake manifold gets a lot hotter than I thought it would. When the hood was closed, it's even hotter than the aluminum fuel rails which you would think would heat soak worse than the composite material the manifold is made out of. Yet, to the touch, the fuel rails feel hotter, faster. It is obvious if you keep your hand on the manifold that it "feels" hotter and hotter over time. Perhaps this is due to how well aluminum transfers heat vs. the composite material? To somebody who was not measuring this kind of stuff it would be easy to see how they'd think that an aluminum intake or metallic ducting could heat soak worse than the factory intake manifold, but based on the data I gathered the composite material heats just the same (or in some cases, worse) than metal.

It is also interesting to note that the primary heat generator for the gas tank appears to be fuel returning back to the tank. Notice how it only gradually heats up until sample 13 (the first 15 minutes of the hood being closed) where the gas tank starts to heat up significantly. I measured the temperature of the tank as the tank faces backward, at about the midpoint (where the fuel sender would be on a 2002 and earlier car). I guess this is not surprising since the tank is heat shielded from the exhaust but it's just interesting to see how quickly the tank heats up once the rails are no longer dissipating heat out of the engine bay. Based on these results, I will likely install a heat sink like these or some kind of cooler like an oil cooler for my fuel:
http://www.martelbrothers.com/catalo...-1-c-1719.html
I want to roadrace my Z06 once it's turbocharged so I am more concerned with the ability to keep cool over time rather than just keeping cool for 1/4 mile.

Also interesting is that the Bosch pump is very, very quiet until about 110 degrees F. Prior to that, you really couldn't hear it in the cockpit. After that it became fairly noisy, to the point that I am thinking about maybe making the second pump only activate at WOT or under boost. For now I will leave it be and test it on the road to determine if I really wanna screw around with that, as I'd likely have to deal with drainback issues between the pump running and then not running and then running again. We'll see. With the pump sitting in the driver rear wheel well, the only real contributor to its heat is the fuel. This is evidenced in the fact that the braided stainless on and around the pump tracked in lock step with pump temperature. Perhaps a fuel cooler would keep the pump quiet?

Anyway, I just thought I'd share some real world data for you guys who turn your own wrenches.

 

Very analytical work. But don't you know this is Memorial Day, and it is your civic duty to be barbecuing...not wrenching today.

 

Be caredul using an IR thermometer. They generally plan on an emmissivity of .95. Reading a shinning metal will give eroneous readings, as well as other items that do not have the emissivity that they were desinged to measure.

 

Thanks, good stuff.
I'd expect that due to the lower thermal conductivity of the plastic manifold versus aluminum, the temperature of the internal surfaces would be colder than aluminum even if the outside temperatures are the same from underhood heat.

 

Yes, I noticed that at odd angles or distances the readings would vary. So I always gathered several data points at varying ranges and angles and eliminated any outliers for any reading I took.

Also note that the control which indicates the thermometer is reading properly is that all components started off at 86 degrees, which was the ambient temperature in the garage.

 

Cooked New York strips yesterday, got some lemon pepper chicken hitting the grill today

 

Good data…

Just a few thoughts, IR and effect of absorbance (material) does change readings. Older units where off quite a bit when measuring stainless steel at emmisivity (spelling ?) set between 90-95% as an example. The newer dual wavelength units are allot better.

As far as heat soak, that to me is a term that doesn’t adequately describe amount of thermal transfer in BTU’s. Yes the Nylon (Nylon 66 I believe) intake does get warm but certainly does not transfer or exchange heat as easily as aluminum equivalent. Although hot, it’s thermal transfer coefficient is considerably lower then aluminum by order of magnitude if not more. So the amount of heat introduced to air is much lower.

Form memory, best to worst thermal conductors:

Silver
Copper
Aluminum alloys
Carbon steal
Stainless steal
..
Plastics
Wood

For fuel cooler maybe look at solid state heat pump (peltier effect). I’ve used them in industrial and instrumentation applications.


Mike

 

Got it. So this wasn't perfect scientific equipment, but all the readings/trends did make sense. So even if it's not numerically accurate I'd at least consider it to be directionally accurate. But point taken

That makes sense. Also the point above from Warp Factor makes sense as well, it's likely that the inside of the intake was much cooler than the outside.

Can you point me in the right direction on one of these? Are they expensive? I was thinking of mounting one of the linked heatsinks on the rear crossmember, kinda in the same area Z06GMAN's Magnafuel pump is. It would get plenty of airflow down there and wouldn't require any power to cool.

 

I’ll lookup various manufacturers of solid state heat exchangers tomorrow at work. You can do a simple small cooler on return line. The reason I looked at solid state heat pump is they can pull a temperature differential greater then ambient. As an example one side of plate can be at 120 (ambient) and other side at say 80 F (fuel side). Just remember a 10A+ draw can be present for a larger unit.

As far as cost i can’t remember, $100 and up depending on packaging and BTU capacity.

As far as fuel temperature goes you probably have data for worst case scenario i.e. two pumps going wide open with no load (engine at idle). This gets you allot of recirculation do to low demand and with every pass of fuel you add heat (fuel returning to tank). Under aggressive driving your temperature rise should be lower do to higher consumption and less return flow.


Mike

 

Hi Mike: Peltier effect devices are extremely inefficient, as a cooler. My memory says about 5% of the BTU's in can be used for cooling. if you do the calculations, that I am sure you can, you will probably find it is impractical.

 

Hi Glenn,

Although efficiency is nothing to write home about, they have come along way in recent years. I can’t remember published values and did mention 10 amps… I did however do a mass balance some time ago and BTU/hour where not bad to control temperature rise.

Incidentally there is a company that makes electric intercooler in a water-to-air configuration. They make some claims that I find hard to believe… I should have bookmarked website. Anyway they are using peltier effect or similar technology and designed for V8. I can’t remember current requirement but do recall 40 amps+ which can’t support their claims when doing a straight KW to BTU conversion regardless of efficiency.


Mike

 

The more I look at it, the more I like a heat sink near the rear crossmember.



It would be nice if it could fit on the "inside" near the leaf spring without rubbing or touching it since that puts it furthest away and shielded from the exhaust, but I suppose it could be mounted on the outside near the sway bar -- nothing a little exhaust wrap or other heat shielding couldn't fix, and the exhaust is real cool at that point, about a 40-50 degree difference than near the tunnel.

If placed before the pump, it could also help solve periodic fuel starvation by acting as a small surge tank. It would also sit lower than the gas tank which helps that effect. If placed on the return line it would get the fuel with the hottest temp delta and have the best opportunity to provide cooling against ambient.