Fourtraxjay Posted June 1, 2011 Report Share Posted June 1, 2011 Is this possible? A good idea? A bad idea? Thougths please. Can I use the EFI live scan tool DVT tab to command the fans 'on' prior to a 1/4 mile run to suck as much air through the rad/ intercooler while | am lining up to run, then switch them off right before it is my turn? I assume alternator drag with them commanded on is high enough to lower e.t and you would want them off for the run. I am also assuming that once switched off, the battery level will not have dropped and the alternator will not be working to recharge the battery and its drag on the engine would be nil. Is this a common practice? or Am I way out to lunch with this idea? thanks in advance for any input. Jay Quote Link to comment Share on other sites More sharing options...
sprayed99 Posted June 1, 2011 Report Share Posted June 1, 2011 Is this possible? A good idea? A bad idea? Thougths please. Can I use the EFI live scan tool DVT tab to command the fans 'on' prior to a 1/4 mile run to suck as much air through the rad/ intercooler while | am lining up to run, then switch them off right before it is my turn? I assume alternator drag with them commanded on is high enough to lower e.t and you would want them off for the run. I am also assuming that once switched off, the battery level will not have dropped and the alternator will not be working to recharge the battery and its drag on the engine would be nil. Is this a common practice? or Am I way out to lunch with this idea? thanks in advance for any input. Jay Not a bad idea however I believe your thought about drag is a simple misconception. The alternator is not like a AC compressor where it actually changes the load required to turn the pulley. I don't thing you will see a difference with the fans on or off during your pass. using the fans to cool down the radiator and heat exchanger/intercooler is what a lot of people do. Quote Link to comment Share on other sites More sharing options...
Krambo Posted June 1, 2011 Report Share Posted June 1, 2011 A high current demand will increase the power needed to turn the alternator. However, I highly doubt you will see an improvement in E.T. Back in my competitcar audio days, when we hit the button the belt would squeel and smoke trying to turn our dual 300 amp alts. Some guys actually used a chain drive! Quote Link to comment Share on other sites More sharing options...
misterp Posted June 1, 2011 Report Share Posted June 1, 2011 (edited) Yes it's a good idea, on a Radix-equipped truck it's critical. The issue is that after each run you need to cool the water in the Radix heat exchanger; the ideal thing to do would be after each run to have the efan and Radix H/E pump running for a couple minutes, to get the heat out of the supercharger - that's even more important than getting the motor cold again (you want super-low IATs). AFA disabling the efans during a run, I would not advise that, plus in real life if you manage your staging time correctly it's not necessary - you make a run, park the truck and let it cool (hood up, fans & pump on), then when in the staging lane you run the engine as little as possible and you should be able to keep the engine temps low enough that by the time you have to line-up again the fans will still be off; after the run when the truck comes down below 45-MPH the fans will come on again as you are driving back to your pit area. Stock efans on low speed will make the alternator pull about 2-3 hp (my WAG) that's not a lot IMO. Mr. P. Edited June 1, 2011 by Mr. P. (see edit history) Quote Link to comment Share on other sites More sharing options...
zippy Posted June 6, 2011 Report Share Posted June 6, 2011 The alternator certainly does pull plenty of power to turn with accessories running such as e-fans. I would say not to run them. I have tried this and odd enough really didn't find any better numbers from it. I later figured out why when running stuff on the dyno alot. When the fans kick on and the air has no place to go all that heat that the radiator was pretty well holding and slowly dissipating is now being sucked out of the radiator and blown directly in the engine bay. Any heat in the engine bay will wind up in the intake. On a vehicle with a ram air system or an open cowl hood (to release the hot air) I would say go for it and run the fans right until you are about to trip the second beam. Quote Link to comment Share on other sites More sharing options...
misterp Posted June 6, 2011 Report Share Posted June 6, 2011 +1. I have always wished our hoods had heat extractors, like the hood on the Saleen truck. Quote Link to comment Share on other sites More sharing options...
zippy Posted June 8, 2011 Report Share Posted June 8, 2011 It's pretty cool (lol, odd choice of words) if you put your hand behind the exit of the cowl hood on a truck with the Goodmark cowl hood that is open. If you have a truck that is running hot because of just plain too much underhood heat have them put on the cowl hood and it is just amazing how much heat will be removed from it. It's enough that I've considered opening the rear of my 06' truck hood up with small holes just as the Goodmark hood is. The 06' hood when you really look at it is almost just like a really big cowl hood. Some good old heat extractors like you mentioned Steve on the sides of the hood would be awsome. If you run a temperature probe under the hood and drive around town you'd be amazed at just how much heat stays under there and even worse how bad it is when the e-fans are on. Quote Link to comment Share on other sites More sharing options...
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