Wheeler Posted January 12, 2009 Share Posted January 12, 2009 I'm looking to relocate my battery for a LS1 install for better weight distribution and to remove items from the engine bay. Anyway I'm going to relocate to behind the passenger seat. I want to use as small of a battery as possible but dont want to go too small... I saw some light weight racing batteries that are very small and light that would fit nice but they only have about 350 amps. Is this enough for starting the LS1 temps above 40 degrees? Any thoughts guys? Quote Link to comment Share on other sites More sharing options...
sundance Posted January 12, 2009 Share Posted January 12, 2009 Hi Wheeler: I'am running a Odyssey dry cell battery PC680 behind passenger seat.Turns over 355 small block with 10-1 compression with no problems at all. The battery is 15 lbs. 7" wide x 6.5" tall x 3" thick. With the battery inside just make sure it's a dry cell or a sealed battery.Hope this helps: Gary Quote Link to comment Share on other sites More sharing options...
Wheeler Posted January 12, 2009 Author Share Posted January 12, 2009 Thanks Gary for the info, that helps alot, that is one of the batteries I was looking at. Did you fab a bracket to mount or did you buy it? Also welcome to Hybridz. Thanks again Quote Link to comment Share on other sites More sharing options...
mobythevan Posted January 12, 2009 Share Posted January 12, 2009 I am using that same odyssey battery on my 5.3 LSx setup in the rx7. It cranks it over just fine, I have started it at colder temps like 20 degrees. Quote Link to comment Share on other sites More sharing options...
sundance Posted January 13, 2009 Share Posted January 13, 2009 Thanks Gary for the info, that helps alot, that is one of the batteries I was looking at. Did you fab a bracket to mount or did you buy it? Also welcome to Hybridz. Thanks again Hi Wheeler thanks for the welcome!! Been a lurker for a few months. I'am new to Zs but not to hot rods. This is a GREAT site for information. I bought there bracket it is well made and fits perfect on the riser behind seat. Thanks Gary Quote Link to comment Share on other sites More sharing options...
Phantom Posted February 1, 2009 Share Posted February 1, 2009 What are you looking for in the way of weight distribution? Have you weighed your car as it is? The LS motor is lighter than the L28. My '77 280Z was 1400/1400 front/rear before my conversion. After converting to the LS1/T56 it was 1400/1430 front/rear - with the battery still in it's original postion. Additonal work on the car - sound proofing, stereo system, roll bar and strut bars boosted it to 1440/1560 front rear - with the battery still in the front. Why move the battery? If you are looking for that 50/50 weight distribution you will be moving the wrong way. Quote Link to comment Share on other sites More sharing options...
MoNkEyT88 Posted February 1, 2009 Share Posted February 1, 2009 From what I gather, he's going to have a stripped interior. My LQ9/T56 has a stripped interior and weighs 2560lbs. I weighed it myself, and I was told it has 50/50 distribution, but I've never had it on corner scales. If he's losing all the weight from the interior, the battery certainly can be moved. Mine is way back by the fuel cell. I'd rather not have it behind the rear axle. When I finish my 260z chassis, and swap everything over, it will go behind the passenger seat. Quote Link to comment Share on other sites More sharing options...
Wheeler Posted February 1, 2009 Author Share Posted February 1, 2009 Well a couple of reasons really to consider moving the battery. 1) As mentioned weight distribution, now per some conversations here, I agree this may or may not improve things as the weight distribution of these cars seems to be pretty good. 2) Moving it will free up room in the engine area that I think I need to mount the ECU 3) Maybe this is the biggest reason (and most hard to understand) but moving heavy items like a battery as close to the center of the car reduces the car's polar moment of inertia, which intern makes it easier for an object (car) to rotate about a vertical axis through its CG (turn). I took the below quote from this site http://www.siu.edu/~ritzel/courses/302s/vehicle/vehicledynamics.htm. It might explain better the concept. "A very important handling concept, which dictates the willingness of a car to change directional position if called Polar Moment of Inertia. “Poles of inertia” are just another way of saying “center of weight concentration”. The “moment” in this concept is determined by the front-to-rear location of the center of gravity. The car turns (changes direction) about its center of gravity in a corner so the further away the centers of weight concentration are located from the center of gravity (which is their common center), the bigger the “moment”. A high polar moment of inertia is present when the weight concentrations are heavy and are far apart. The low polar moment of inertia is found when weight concentrations are light and are close together. In other words, it is easier to steer a vehicle with a low polar moment of inertia. A vehicle with a low polar moment of inertia gives a quick response to steering commands. A vehicle with a high polar moment has high directional stability (meaning it resists changing its direction). " Quote Link to comment Share on other sites More sharing options...
Phantom Posted February 1, 2009 Share Posted February 1, 2009 I fully understand PMI principles. My real point is that you need to know where you are to correctly determine what you need to do to get to where you want to be. If you're truly worried about PMI then why move the battery which is not all that far from the cars center and leave the fuel tank/cell out behind the rear wheels? I was able to get my car corner weighed while the transplant was underway and the JCI kit components were being designed. That is one of the reasons the JCI motormounts shift the engine slightly toward the passenger side. It allows room for exhaust and steering on the driver's side plus helps offset the driver's weight. The ECU can be easily mounted in the battery area or under the dash near the heater blower. Mine is in the latter because it gets it inside the cabin and reduces it's exposure to the elements - especially the heat of the engine bay. The T56 is a monster transmission compared to the Datsun T5 that was originally in the car. It is significantly heavier and, because of it's size and location, it shifts the cars weight bias toward the rear. Also be advised that about 70% of the driver's weight will be carried by the rear wheels. This was another fact I discovered by weighing the car multiple times. Of my 240 lbs, 180 went to the rear wheels and 60 to the front. A shorter, person who would have the seat farther forward would have less weight bias toward the rear. Lots of variables if you're building a track car. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted February 2, 2009 Share Posted February 2, 2009 My LS1 240 is about 51-52% nose heavy with a full size battery behind the passenger seat. Me engine fore/aft is about the same as Johns Cars and I wish I would have pushed it back further when I made the mounts. Cameron Quote Link to comment Share on other sites More sharing options...
Wheeler Posted February 2, 2009 Author Share Posted February 2, 2009 Ok, not to derail this thread any further (as it is about battery rating / size...), but I wanted to add that with respect to PMI and vertical CG location, I don’t think you need to know where you are at before you make changes. In both cases you want them reduced / lowered, I have not heard of a case where some one had a car with too low of a CG or to low of a PMI - so, at least in theory and regardless of where your car is currently it makes sense to pursue reducing these. Now anyone can argue that the difference made by relocating a battery from the stock location to behind the pass seat will not make any noticeable difference - but lowering the CG and reducing PMI certainly won’t hurt. As far as moving the fuel tank forward I agree that would help but I have to ask how would you do that, safely and reasonably (allowing a passenger seat and not raising the CG)? My real point is that you need to know where you are to correctly determine what you need to do to get to where you want to be. If you're truly worried about PMI then why move the battery which is not all that far from the cars center and leave the fuel tank/cell out behind the rear wheels? . Phantom, your point about weight distribution is well taken, however. One really should have an idea of where you are at prior to making changes.[/size] Quote Link to comment Share on other sites More sharing options...
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