Interesting article in the March 2003 Family & Performance Boating Magazine on a test of the new Blower Shop intercooler for an 8-71 supercharger. It shows the basics of intercooling a positive displacement supercharger.

Here are the results:

1) No intercool , 1.02 overdrive, 840 HP @ 7.7 psi, 190F

2) Superchiller?, 1.04 overdrive, 870 HP @ 7.4 psi, 124F

3) Blower Shop, 1.09 overdrive, 900 HP @ 7.6 psi, 106F

The basic point of the article is that the Blower shop intercooler is better. It has a "denser core" (fins/inch?) that does more cooling at the expense of greater resistance to air flow than the "popular brand" (which I assume was Superchiller), which naturally has more resistance to air flow than no intercooler at all.

To keep the test fair, they had to increase the overdrive (change pulleys) to maintain a constant intake manifold pressure. Then air temperature alone determines the winner. The Blower Shop is the winner with a much lower temperature. But it is the pulley change that is responsible for the HP gain. If you look at the ratio of pulley overdrive, you can see it is very similar to the ratio of horsepower.

1.09/1.02 X 840 HP = 897 HP, very close to the 900 HP observed.

With positive displacement superchargers, CFM is proportional to RPM. If you want more power you must spin it faster.

Fun With Numbers

They did get the temperatures screwed up in the article somewhat. They say that the temperature after the blower is 190F, then they say that the temperature after the blower is 142F with the Superchiller. This is impossible since no cooling has taken place before the intercooler.

Anyway, using the 190F figure you can calculate compressor efficiency. Assuming an ambient temperature of 75F, the compressor was 58% efficient. But you have to remember that the air temperature after the blower would be higher if it wasn't for all the fuel dumped in and evaporated. I'm guessing that the temperature would be closer to 210 without fuel which brings the efficiency down to ~50%. This is a figure often quoted for Roots blowers.

You can also calculate the intercooler effectiveness with the temperatures in the article. The Superchiller drops air temperature from 190F to 124F using 78F water. The Blower Shop intercooler drops temperature from 200F to 106F using 78F water. (200F because they spin the blower faster and have 8psi in front of the intercooler as opposed to 7.6 psi). These numbers show 59% cooling effectiveness for the Superchiller and 77% cooling effectiveness for the Blower Shop.

This is a big improvement. Although they don't say in the article, they must have increased the fins/inch quite a bit.

Overall this change is only good for 30 HP, but that's not the point. At 106F the Blower Shop intercooler is going to be a lot safer and more reliable than the Superchiller at 124F.

Obviously, if you ran the Superchiller with the same 1.09 overdrive you would probably pick up the 30 HP difference, but the temperature would be even higher.

This is why Roots blowers need so much fuel; the fuel is needed as a coolant to avoid detonation. I'll bet the Blower Shop intercooler would allow a little less fuel consumption, as if that matters to anybody with a 900 HP engine.

Check out the pictures in the article. It's a killer 497 CID engine.

Tomcat

You're still looking at boost is boost avoid looking at drive ratio. Look at it this way if I take my engine with my 250 on it, at 6 lbs of boost, and just swap the blower to a 6.71 running the smae 6 lbs of boost your drive speed will be very different, but you'll be just about the same on power.
The blower speed shop only have small effect on the overall performance, the boost is the main importance.

Doug

I'm glad to see some results to support my tossing of a super chiller for a blower shop cooler

Tomcat, you are a pillar of knowledge on this board!

Tomcat,
The temp Number of 145 is correct. The air will hit the core and offer some cooling effect. The air circulates all over the place, through the cooler and back to the Blower. Remember it is under pressure.

Ambient temp that day was 90 degrees. The fin count is 19 per inch on the air side and 16 on the water side.

Thanks for keeping everyone that reads the boards informed.

Marv
The Blower Shop

Marv, Great #'s! Congratulations on a new product that gives us choices. It would be interesting to know if you have done any testing against Lee and Whipple. Include MSRP so we can find the "best bang for the buck" so to speak. Thanks, Todd

Boostdaddy- Glad to see you become a member.

The lower intake temperature allows for more boost without detonation. How much more boost could you run with intake temps of 70 degrees and how much more HP?

In reading the thread that TC had going about his testing with his intercooler. Jim V. (I think it was him) brought up the point that the test on the dyno is not long term & the engine has not had time to get heat soaked (right word ??). From what I gathered from that, was in a real world the motor might go in detonation and/or pre-ignition after a long run at WOT. With the blower shop intercooler the motor was not seeing any more boost, just denser air.

Boostdaddy - I did not realize that the air in front of the intercooler would be affected this way, good point. It's still OK to calculate cooling effectiveness the way I did, but compressor efficiency will be higher than I calculated if you were starting with 90F air.

Glad to have you on the board, and I am really glad to see someone testing their products and reporting the results. Good luck with the new intercooler.

Tom

How about stacking a 2nd intercooler on top of the 1st and repeating the test.