Lancer033

What advantage does one have over the other?

i.e. - justify spending $2394.95 for mechanical pumps vs. $1248 for electric pumps?


note: prices from:
http://www.lgmotorsports.com/catalog...oducts_id=1080
http://www.dougrippie.com/

wtknght1

Anything mechanical draws (takes) power from the driveline...so you essentially don't have as much power going to the wheels. Electric pumps don't have that issue because they aren't driven by the driveline.

It's the same issue as having a 'normal' power steering or water pump that is driven by the fan belt. That takes power...power from the engine...power that could be used to propel you down the track faster. The same thing can be said for the fans too. That's why more and more things on racing cars are driven by electric motors that don't take energy away from the engine - fans, pumps, etc. Those electric motors are powered by the battery...and alternator. See??

The DR pumps are electrical. LG's stuff is mechanical. I don't know that one is any more reliable than the other, but for the record, the T1 legal tranny cooler uses an electric pump and I've had no issues with it.

The only other thing in this equation is legality if you run a racing series. LG's coolers aren't legal in T1...to the best of my knowledge. So, if you plan on racing in a specific series, you need to check their rules to see which one (or both) is legal. NASA, SCCA, etc all have their own specs as to what you can and can't do to your cars.

0Randy@DRM

I'm pretty bias on this subject, so I will let others answer. But if you have any questions about our setup, I will be here.

Randy

gonzalezfj

Chris, not to start a war here, but ultimately all power used in the car comes from the engine. Where does the alternator get the power it needs to generate electricity. The battery just stores the stuff.

The advantage of electric motor-driven accessories vs. engine-driven is that engine-driven accessories usually take too much power from the engine at high RPM (as when you are pushing the car to the max). Electric-driven pumps, fans, etc. always take the same power to operate regardless of what RPM the engine is running.

Remember the flex fans that after-market manufacturers use to sell? The vanes flexed so the fan used less power at high RPM.

At any rate, you are correct in recommending electric-driven pumps and whatnot. It is a simpler solution that has proven to be very reliable in racing applications.

Frank Gonzalez

73-84 IMSA Widebody

The alternator is mechaniaclly driven, as long its and the batteries output and capacity are adequate I would go electrical, particularly when comparing cost. I've had a few issues with maintaining adequate battery charge because I use a relatively high electrical load and usually run the car for short periods of time often not adequately charging the battery vs load, i've offset that with a trickle charger.
If you are doing at least some "normal" driving this should not be an issue for you.
From the previous post, biased opinions are welcome, particulaly if you admit some bias up front, I can certainly learn from others and thier experiences................

freefall

Do you drive on the street at all? If so, in cool weather the mechanical could prevent the fluid from heating up, where you can just turn off the electrical pumps.

I'll guess the electric pumps weigh significantly more than the mechanical unit though. Also, at high speeds it is desirable to have the pump turn faster, which the mechanical does.

wtknght1

No doubt. I was going to put that on there, but I figured only somebody REALLY **** retentive and nit picky would bring it up or even think about it (like me!!). ha ha ha

The alternator just uses less than the rest.

I've actually heard of folks using systems that only turned the alternator on when the brake lights were on. That way, you save all the engine power you can for acceleration. Racers are sick!

freefall

You guys aren't the only ones that thought about the alternator power - the more load placed on it, the more power it will sapp. From memory, about 1hp is sapped for each 25amps.

ghoffman

745 watts/HP, so assuming 14 volts, that would be 53 amps not including power factor, losses etc. Frank is correct, but some guys put a switch on the alternator that turns off the field coils under WOT conditions, or only turn it on under braking (me). That means that when you are idling, braking or otherwise not full throttle, it is charging the battery and does not cost you anything in performance terms. Also, an electrical system can have a thermostatic switch for faster warm-up. A purely mechanical system that runs all the time will cost you HP all the time, whether it is driven off of the drive line or engine. Even if you have pressure bypass valves in it, you still have pumping losses. If you break a gear tooth and it gets into the pumps, the electrical pump would die and not cause any collateral damage like a mechanical driven might. Possible advantages of a mechanical system is it might be lighter, quieter and easier to package.

MitchAlsup

Let us take this as a starting point.

1HP is 745.6Watts

25 A at 12V is 300 Watts So, the overall efficiency is around 300/745.6 = 40% through the alternator.
25 A at 14V is 350 Watts So, the overall efficiency is around 350/745.6 = 45% through the alternator.

And this is before you consider the pumping losses (similar* for both setups) and the electric motor drive losses (for the electric pump case). Really good electric motors operate in the 50% efficiency ranges.

But the real issue for race track cars, is what happens when the electrical system is dieing (say from a bad battery) and you happen to be in the chase. A) mechanical pump--you continue running B) electrical pump--do you or do you not continue running?
[*] it is true that the electric pump consumes rather constant HP as it moves transmission oil through the transmission and associated cooler(s). And it is true that the mechanical pump has higher HP consumption at higher driveline RPMs. I will argue that it is at these higher HP levels where you really do want the higher flow rates the mechanical pump provides (and the associated consumptioni this entails). The higher flow rate being used to move more heat from the Transmission.

{However, if the transmission cooler is already disipating its maximum amount of heat, the added flow of oil through it does not help.}

wtknght1

And sometimes, faster flowing fluid thru a cooler isn't better. For example, the thermostat is in the car for three primary reasons.

1. To stay closed until the engine heats up.
2. To open at a certain temp to begin cooling the engine.
3. To actually slow the water flow! That allows the water to stay in the radiator long enough to cool it off. Without the thermostat, the water flows too fast and doesn't stay in the radiator long enough to cool. Believe it or not!

Most of the electrical pumps are pre-calibrated to flow at the correct rate to allow good cooling.

Miaugi

John Shiels

if the alternator is running all the time and the battery is charged how does it take power away from the engine?

wtknght1

Drag.

John Shiels

is the drag not the same on the alternator all the time?

MitchAlsup

The input to the field coil in the alternator is regulated so that the output voltage in the car remains steady. There is a device called the voltage regulator that controls the input to the field coil of the alternator. When the voltage dips, more current is added to the field coil, and more output is generated by the alternator. All of the electrical power produced by the alternator comes from the engine itself (after considering the efficiency of the conversion from rotational power to electrical power).

So if the electrical demand is low, the output of the alternator is low and little power is consumed. On the other hand, if the electrical demand is high, the output of the alternator is high, and so is the power consumption.

The optimal use of the battery is that of a large capacitor, with the alternator producing all of the electrical power used by the totality of electrical consumers inside the vehicle. Ever come to a stop (say at a stop light) and listen to the motor, then take you feet off the brakes and listen to the motor become smoother? The only differece is the power used to run the brake lights! This comes from the alternator and at least on my vehicles is audible.

ghoffman

The alternator's current output is not constant, it depends on the electrical load. When the load (demand) is high, the field coils are energized more and it requires more shaft HP to turn it. If you take an alternator and spin it when it is off of the car it has very little resistance. If you were to try to spin it with your hand when the field coils are energized, you cannot turn it with all of your strength. That is why having a on-off alternator switching system that works off the brake light switch on a race car that has alot of braking areas saves HP. On a big superspeedway that you are WFO all the time, this scheme won't work!

Basically same as above....

96CollectorSport

I've seen both set-ups and installed 3 of the LG coolers. The LG kit is a really cool set-up and looks really trick, does that make it worth the $$ probably not. The LG kit is quieter than electric pumps but I still don't think that makes it worth it. Also getting all of the parts from LG was a hastle all 3 kits I installed were missing pieces which delayed the install, plus they don't have a place for you to mount the coolers, I had to fabricate my own bracket to mount the coolers. All in all I'm happy with the kits but there was a PITA factor working with that particular set-up.

I've seen the DRM set-up and it seems to be as good for $1k less, although I haven't installed one the install also looks like it would be "interesting" as well.

Also if I'm not mistaken you really only need to cool the diff, since the diff is where the heat is coming from (friction from the clutch packs), so the tranny cooler really isn't necassary. Or at least that is what I've heard.

That's just my opinion, I could be wrong (Dennis Miller)

RAFTRACER

BE CAREFUL................

ghoffman

Of what?