pgerst

GM Parts Direct has a 1LE elbow (pn 25147187) for $77.89. Works better (no heat transfer and better airflow) plus (imo) coolness factor of being a factory performance part.

slowride94z

I would vote this as the best route

calaban

I would as well. I'm not disputing the fact that a metal elbow will become heat soaked and then, because of this, will show a measurable difference when compared to a rubber elbow. I'm just asking how bad can it be?
I searched and could find no dyno comparisons between them and add in the fact at how long the air is actually in the elbow. I mean can there be so much heat absorbed by the metal elbow that the air speeding through it at such a speed would pick up enough heat to affect the air/fuel mixture in the cylinder. If it affects the IAT sensor then relocate it further away from the engine. Which goes back to how much negative effect can it have and is it the actual air charge being heated or the IAT becoming.g heat soaked as well, affecting the timing.

bw_hunter

How long is the air in the throttle body? A dyno test on WS6.com showed a 6 hp increase from a coolant bypass. This I'd what I meant by measurable. 6.3 rwhp is significant and directly attributtable to a cooler intake charge. The metal elbow has the same effect and it is heated by the air from the radiator.....160+Degrees. Anyway, I was just trying to bring up the short comings of the metal component...

By the way, the airfoil is worth 2 hp....same site.

calaban

That's cool, I checked it out today when I was poking around. I'd still like to see a direct comparison to see some actual numbers. I can't see it being as drastic as the throttlebody bypass though.

bw_hunter

I guess I don't know how to convince you. The dwell time in the elbow is slightly longer, the air has low mass and a low heat capacity meaning it picks up heat quickly. Heat the elbow to 160 and I'll wager you see similar results.....

calaban

I just can't see how the elbow, even sitting in the hot air from the radiator, can transfer enough heat to the air to cause a loss comparable to the air through a throttlebody that has coolant passing through it. I'd wager that the transfer of heat from the coolant filled throttlebody is much greater than it passing through the elbow. As Injuneer say, the air passing through keeps the elbow nice and cool. When you circulate coolant through the throttlebody the air can't draw the heat out as it passes through since the coolant filled throttlebody holds so much heat. Once the coolant is removed, the throttlebody body will be able to transfer all the heat it contains faster than it can build up causing the the throttlebody temp to drop which in turn keeps the intake air cooler. Which brings me to my point of, the metal elbow cannot absorb the engine bay heat fast enough to stay hot, much less transfer enough to heat up the charge passing through it. Once air starts passing through the elbow it basically cools it faster than it can pull heat from the air. This is why its cool to the touch immediately after driving. Turn off the car and check it 30 seconds later and it will be the same temp, or very close, to the underhood air temp.

Injuneer

Hot air is surrounding the outside of an aluminum pipe. There is cool air on the inside of the pipe. Aluminum is an EXCELLENT conductor of heat. The heat moves from the hot external surface to the cold internal surface, where it heats the air. There is a much larger surface area for heat transfer in the aluminum elbow than there is in the throttle body. Velocity is NOT the problem. Velocity/turbulence improves heat transfer from the wall to the air. It keeps the LMTD high, and that is the driving force for heat transfer.

For every one degree of temperature increase in the air entering the cylinder, you will lose about 0.19% density, meaning a 10* increase in air temp costs you almost 2% of the engine power.

Odd... when someone decides to add a throttle body air foil, people explain the gain is very small. And the answer is "well every little bit helps, because all the little things add up". But when someone suggests the aluminum elbow is hurting performance, the answer is "but its only a little loss".

I don't get it.

calaban

Thanks for that explanation. I figured it would be a tiny fraction of HP, but does sound like it could be more significant than I thought. Makes me wish I'd bought a rubber replacement instead of a cast aluminum piece. But it was a good deal cheaper than the stock or 1le replacement and I was, and still am, on a budget when it comes to modding.

NJ-LE

I looked at a Freescan file from last july and found these numbers.
This is with a 160°F thermo, TB hot water bypass and the IAT sensor mounted in a Trick Flow elbow.
The fan setting is 190°F on, 182°F off.
This is a mix of city and interstate driving with some idling time too.
(all the numbers are in °F)

avg max
--- ---
ambient = 83 83
IAT = 96 114
Coolant = 159 188

more contact area in the elbow but there would be a higher temp in the TB
It would be nice to see what the sensor in the rubber elbow numbers are with both a stock thermo and fan settings and with a 160°F thermo with reprogrammed fan.
sorry about the formatting

pgerst

Where does the PCM pick up ambient air temp? Surprised there is such a delta between IAT and ambient. Also wonder what the effect of the different CAIs would be? I.e., SLP has larger volume cross section and probably less restriction/turbulence than the molded ones (as is straight pipe)so it probably flows better but it is metal (stainless, I think) so it probably adds heat.

NJ-LE

Ambient was a thermocouple in the shade, outside my home! (I guess a second IAT sensor mounted on the air dam and connected to an unused PCM temp input (oil?) could be recorded via DataMaster) The max IAT was at the end of the session which finished with a 2 minute idle. There is the Powerdyne's contribution too. It's sitting there, soaking up underhood engine heat and the heat from the tempered air from the radiator. My inlet air is from inside the front of the fender so it started at ambient.
I looked at the data again and there is a section that was mostly 45-50 mph and the IAT looked stable at 102°f and the Coolant at 182°f.

pgerst

NJ-LE -- do you know how much of the heat rise is due to the compression itself versus heat soak?

Injuneer

Good point.... the blower heats the air up as it compresses it. Makes the data sort of difficult to compare to a normally aspirated setup.

NJ-LE

The log session was "well behaved" driving. I don't believe the PD contributes much compression heating during "adult" operation. It's centrifugal and the case has an open, internal bypass return to the inlet side cast in it. Lots of pumping slippage. There was one moderate "get quickly to highway speed" moment which only sent the MAF to 233 gms/sec and that showed a brief IAT increase of 8°f (104 to 112) which was back to 104 about 20 seconds later with the MAF back to 25-30 gms/sec. I think (hope) the earlier posted numbers represent something of a normal driving, worst case of metal elbow heat effects.