Christmas morning and I'm wondering about blower discharge temps!

I'm presently making just under 6 lbs with the stock 575SCI/Weiand 256 blower @ 5500rpm, fitted with the Whipple low pro intercooler. Going to replace the stock Merc units with a more stout blower this winter and wondering about blower size vs, discharge temps at 6 lbs.

I'd imagine a chart would be impossible given so many different engine configurations but how about some real world experience with blower discharge temps.

Any idea of discharge temps @ 6 lbs of the TBS 250 vs the 671 vs 871?

Thanks and hope you're all enjoying Christmas!

Kurt

...What got me thinking is Steve's post above, where he ditched the stock blowers and Whipple intercoolers for the 871's with NO intercooler. Could the larger, slower turning 871 make less intake heat than the 250 blower fitted with the Whipple intercooler?

Thanks,

Kurt

Good questions Kurt, I would also like to know!

Its known that compressing air in itself raises the air temperature. But, a 8-71 turning say 1:1 ratio, lets say 5500rpm, vs a 256 spinning 1.8:1, or 9900RPM, with a chiller underneath, which would have cooler IAT temps at 6psi of manifold boost?? And which setup would make more HP.

The consensus from what i've read, seems to be that adding a intercooler, rarely does anything for speed gains, unless you crank up the boost. But, does say swapping a 256 to a 8-71, gain mph with no other changes and equal boost psi.

My gut tells me the larger blower will win, but would like to see some actual results.

Hey Joe, Merry Christmas and thanks for your input!

I should have been more clear on this blower upgrade project, my main goal is reliability and detonation prevention on pump gas.

The 871 with no intercooler does interest me, the larger slower turning blower should make less heat at 6 lbs but will the intake charge temps be higher than the much smaller, faster spinning, 256 at 6 lbs intercooled?

Kurt

Same to you Kurt! Hope all is well.

All i know is, I have several buddies running non intercooled setups, without any detonation problems. I ran 7lbs on my 460CI alum headed 8.4:1 engines, 250 blower, no chiller. No detonation. I see no reason why I couldnt run a 871, at 7lbs, without a chiller with the same setup. There would probably be much less heat in the intake with the larger blower.

I think some of the variables consist of the overall setup. Aluminum heads or iron heads. Water thermostats or no stats. Sea water temp. Altitude. Jetting. Timing. quench. static compression. boost psi. Overpropped or underpropped.

For example, my buddies setup.
509CI
9:1 Static compression
Cast iron heads
871
Superchiller
8psi

A possible setup I may run
468CI
Aluminum heads
8:2 static compression
871
no chiller
7psi.

Which engine would be more likely to detonate first? the iron headed 9:1 intercooled at 8psi overdriven? Or the lower compression, alum headed, 7psi non intercooled with underdriven blower?

My guess, if your building a blower specific engine from scratch, proper dished pistons, alum heads, cam, quench, etc, and plan to run 6-7psi, should be fine without the chiller. But you have say a non blower specific engine, say like a HP500 merc, and want to bolt a blower on it, and run 6-7psi, you need the chiller. Or if you are going for big boost, big HP, even on a blower specific build, the chiller will allow you to crank up the boost even more, say 9,10, 11+psi to really make some nice power. Once again, just a guess.

Mild, how much total timing are you running with 5 lbs boost ? ?

Go to Eaton supercharger web site or MagnaCharger web site and look around. Under technical it is suggested to run the smallest sc for the best all around performance. The site also says that heat output is a function of Boyles Law and psi, and not how fast the screws are spinning. For each 10 degree F in air temp the Hp will decrease by 1%.

Under the hatch of a boat on a 90 degree summer day with a 140 degree thermostat will likely have 100 degree plus inlet air temp before it is squeezed

The question, what is the heat generated by a 70% efficient compressor @ 5 psi @ 8 psi etc...then compare to a unit with 80% efficiency etc...

A diesel air compressor for instance @ 750 cfm @ 120 psi will probably not make 10 x the heat of same size unit @ 12 psi

30* total with 7lbs was what i was running.

I dont run water thermostats, engine water temps at 100*. Open style race hatches with big flame arrestors woke the engines up.

Check out this web site for supercharger discharge temps. Information comes from Corkey Bells book of super charging

search lextreme.com intercooled Vs non intercooled

This should answer most of the questions about outlet temps of a supercharger and compressor type

Thanks James, I spent quite a bit of time there but did not find the info I'm looking for. Hopefully one of the builders here will chime in.

Kurt - you could call my dad (jetman), he doesn't frequent this site but I am sure he can answer your questions, he is quite knowledgeable on superchargers. PM me if you want his number?

...Jim