We would like to take some time to show the heat exchanger system development we have had going on for the C6 Corvette ZR1 platform. We originally started looking at the platform while doing intercooler brick replacement design (which is still in testing), we noticed that the system as a whole had many shortcomings. We threw around some ideas and decided to go ahead and begin development of a complete turn-key HX solution. Looking at the OEM system, other aftermarket offerings, and speaking with ZR1 owners, we quickly came up with a list of design goals.

1. Design a more efficient heat exchanger setup for better cooling without sacrificing air flow to the radiator.
2. Increase fluid flow through the system.
3. Increase fluid capacity in the system.
4. Come up with an easier way to fill/check the system.
5. And of course we wanted to make the complete system of the highest quality of materials while keeping it as aesthetically pleasing as possible.

Some of the tools that we used during the R&D process included 3D modeling software, a 3D printer, a MoTeC C185 stand-alone logging system, MoTeC/RaceGrade K-type thermocouples and pressure sensors, as well as water flow and air speed meters. Data collection consisted of: bench testing, dyno testing, and in car track/street testing.

Some of the heat exchangers we had on hand to test for development were the factory GM HX, a Katech direct drop in HX, and a PWR or more commonly known as the Magnuson HX. Upon inspection of the factory HX, a large flaw was found immediately, there were no separators within the end tanks to force fluid through the core, allowing the potential for fluid to bypass the core and water tank. The heat exchanger also used a factory hose connection size of .464” ID for fluid entry which later proved to be a huge restriction in the system. The core itself has a very high fin density, and is a decent size with a frontal area of 142.62 sq in, at .875” thick, giving it a total core area of 124.79 cu in. and has a “tubes per square inch” ratio of 3.15.

Next we started looking at the Katech HX. This unit is a direct replacement for the OEM unit. It featured the same .464” ID fluid entries. This core was also missing the dividers in the end tanks. If you pour fluid in the top it runs out the bottom. The core frontal area was less than the OEM unit, bringing it to 130.50 sq in. The core thickness was right at 2.25” giving a total core area of 293.62 cu in. The fin density was less than OEM with a “tubes per square inch” ratio of 3.00. One thing we noticed is when the unit is installed, it pretty much blocks off all the condenser/radiator area above it. In hot climates like here in Houston Texas, this could be an issue.

We then evaluated the Magnuson HX, a sticker on the side showed it to be manufactured by PWR. This core was not a direct drop-in; it required custom brackets to be made for mounting in front of the condenser as well as line adaptions. It also had a very large frontal area at 320.62 sq in, but only had a thickness of .750” giving a total core area of 240.46. This core had a fin density close to the Katech with a “tube per square inch” ratio matching the OEM at 3.15. Fluid entries into this unit were a standard .750” with a .612” ID. We saw this as a definite improvement from the OEM entries. This unit was also built as a dual pass configuration which feeds from the bottom. There is a bleeder at the top and with the HX in the vehicle it is not accessible. It requires the HX to be lowered out of the air duct for bleeding.

After careful design and core selection, we built our HX with a frontal area of 194.06 sq in, with a thickness of 1.50”. This gave us a total area of 291.09 cu in with a “tubes per square inch” of 4.00. We were able to build it to fit the very front of the vehicle using the full width and height of the front opening, where 100% of the air would have to pass through it. The next step was to increase fluid flow through the system to help remove heat more quickly. We achieved this by reducing all restrictions in the fluid system (except the intercooler bricks themselves) and coupling this with the Stewart EMP pump in its reprogrammed (High Output) form. All lines and inlet/outlet sizes were increased to 1.00” ID to match the pumps ports and to lower total system pressure; thus maximizing the flow potential of the pump.




The largest restriction we had to tackle besides the intercooler core itself was the cast inlet log manifold that feeds the intercoolers. This uses the same connections as the OEM intercooler, again with the .464” ID, but feeding both intercoolers. We sat down and designed individual feed inlets for the intercoolers, with .625” .750”, and .875” O.D. Barbs. Next, we 3D printed the different versions with our in house 3D printer so we could bench test them. Bench testing consisted of pump differential pressure testing while running fluid through the stock inlets, and our different test pieces, using the OEM joiners that connect the inlets to the intercooler bricks and back out to the pump (isolated). Testing showed the least pressure running the .875” OD barb inlets (these are true .750” ID). Once that was taken into account we tested the complete OEM system, including the lines, HX, water tank, factory inlet log, and intercoolers, to get a baseline of pump differential pressures and water flow rates. We then installed our upgraded inlets and retested. Next we swapped over to the EMP pump and tested. Finally, we swapped in our heat exchanger, large line setup, and dual stage recovery tank system. We were able to see how much each of these components affected flow and by the end of our testing we were able to almost double fluid flow through our purpose built complete HX system.

The last set of bench tests we performed were to measure air flow loss through the heat exchangers themselves. This was an important test as too much air flow loss will reduce the cooling ability of the radiator. The first HX tested was the OEM unit with an air loss of 16%. Second, we tested the Katech with an air loss of 18%. Next was the Magnuson/PWR, as expected with it being so thin, it had a minimal airflow loss of 9%. Last, we tested our D3 HX. This gave us an air loss of 16%, which was dead on even with the OEM HX.

 

The next step was on vehicle testing which we did on our loading dyno. The mods for the test vehicle used were 2.3 upper pulley, intake, headers, and a catless x-pipe with a custom dyno tune on C16 for added vehicle safety during testing. The goal was to subject the HX system to the most extreme conditions and see how well each core did. We did two test series per HX system. The first from dead cold (ambient) conditions, steady stating at 3000RPM to stabilize temps, then doing 3 back to back full pulls with heavy load on the dyno from 3000RPM to redline without any breaks in between. Then the vehicle was allowed to idle for 1-2 minutes to allow the cooling system to circulate (ECTs usually ended up in the 230F Range). Afterwards, we shut off the vehicle for 3-5 minutes, and then ran the same test again a second time starting with the elevated temps from the previous run. All dyno testing was performed on the same day. All temperature measurements were taken with thermocouples. We measured pre and post intercooler air temps, water temps in/out of the HX, water temps in/out of the intercooler bricks, as well as ambient air temp (in front of heat exchangers). We also logged Pre and Post intercooler manifold pressures.








First test performed was the complete OEM HX system. Within the first full rpm pull, pre intercooler temps were at 314 degrees and post intercooler was at 172 degrees showing a 46% cooling effectiveness. By the third and last pull, pre blower temp were at 394 degrees and post intercooler were at 217 degrees showing a 45% cooling effectiveness. Overall, it was not bad for a system not meant to be used on anything but a stock vehicle. Logs show spikes in post intercooler temps following the pre intercooler spikes.





The second test performed was done with the Katech direct drop in HX. The first full rpm pull pre intercooler temps were at 314 degrees and post intercooler temps were at 188 degrees, showing a 41% cooling effectiveness. By the third final pull pre intercooler temps were at 383 degrees with post intercooler temps at 231 degrees showing 40% cooling effectiveness. Post intercooler temp spikes were similar to the OEM. Testing also showed this HX to work less efficiently than the OEM it replaced.



Next to be tested was the Magnuson/PWR. The first full pull, pre intercooler temps were at 321 degrees with a post intercooler temp of 172 degrees, showing 47% cooling effectiveness. By the third final pull, pre intercooler temps were at 398 degrees with a post intercooler temp of 203 degrees, showing 49% cooling effectiveness. Post intercooler temp spiked again following the trend set by the other HX's but with a slightly better recovery between rpm pulls. Overall it had better post intercooler temps.



Our final test was performed with the complete D3 HX system (HX, pump, lines, dual stage recovery tank, and inlet manifolds). First full pull, pre intercooler temps were at 339 degree with a post intercooler temp of 142 degrees, showing 59% cooling effectiveness. By the third final pull, pre intercooler temps were at 383 degrees with post intercooler temps at 168 degrees, showing 58% cooling effectiveness. Compared to other HX system logs, our system did not have the same thermal spikes in the post intercooler temp. Overall, post intercooler temps were far lower than the other systems.

Color OEM - Black Katech overlay

Color OEM - Black Magnuson overlay

Color OEM - Black D3 overlay


RPM-GREY, PRE IC Air temp - Orange, Post IC Air temp - Teal





Next, the vehicle was taken home by the owner and daily driven the following week, reporting the lowest IAT's he has seen with very fast recovery times. He also attended a private track rental with us. Outside temps at the track that day were recorded at 98 degrees. He ran multiple hot lap passes with starting temps of 123-127 degrees before the burnout. The highest temp reported after a pass was 143 degrees. By the time he drove back around to the burnout box the temps were back down to low 120s again. During the Street Car Takeover roll race event, he performed 10-12 back to back 40mph to 1320ft runs in low 90 degree, very humid weather and had similar results. He also took it out and did some street runs in similar weather. Doing multiple back to back 5th gear runs with zero cool down time netting a max of 152 degrees. These temp readings were done using his Aeroforce OBD2 logger/gauge.

 

Overall our engineering team met every one of our goals for this project. IAT's and recovery time were greatly reduced. Airflow through the heat exchanger matched that of the OEM unit. Fluid flow through the system was almost doubled. System fill/bleed time was reduced to less than 2 minutes and did not require any special filling adapters. We were able to maintain an aesthetically pleasing look with the front mount HX and CNC’d intercooler inlet manifolds.

We will now be taking pre-orders on our complete HX package consisting of:
Small fin high density high flow front mount heat exchanger
CNC aluminum intercooler brick inlet manifolds
Stewart EMP pump in reprogrammed form
Dual stage non pressurized recovery/fill tank
Power steering cooler mounting brackets (these also double as OEM HX duct hole block offs)
Pump mounting bracket
Horn relocation bracket
CNC mandrel bent fluid tubes
All needed hoses, clamps, couplers, and hardware
Hand fabricated and tig welded in house in Houston, Texas

Retail is $2995.00 for the complete system ground shipped anywhere in the lower 48 states, wholesale available to qualifying businesses.

We are also under development of a Stage 2 (Intercooler brick upgrade) and Stage 3 (Upgraded supercharger top) add on to this system.

Finally, we would like to thank Jim Costco (JC13ZR1 on CorvetteForum.com) for originally bringing the problems with the ZR1 HX system to our attention. He provided feedback and data from his previous street and Texas Mile runs, and more importantly provided the vehicle with the different HX systems for testing!