electric water pump?

Something's amiss here … my belt (using the stock water pump and Maxima alternator) measures 41 inches --- I measured it twice. The string going around just the crank pulley and Maxima alternator is ~31 inches. That was very carefully measured, as it will be my new belt's length. Both these measurements make sense, as to which is smaller. But this can be easily resolved, as you can simply measure the length of string around just your alternator and crank pulleys --- you needn't be that accurate, nor will you need to remove anything. A rough estimate is fine.

WELL, I measured with a string once to get my belt originall and measured 38", but when I got a 38" belt it was way too large. I then got a 32" belt and it fit with the tensioner nearly fully tightened :-

Stock belt for water pump, alternator and crank pulley is 41 inches.

It is possible I screwed up in remembering what I used, it was 2+ years ago I bought the belt…

Now all I have to do is find a 4-rib 14mm wide Micro-V belt ~30 inches (770mm) in total length.

Any ideas out there? … I've searched for numbers close to this and haven't had any hits.

I'm still positive I have a 32" belt.

The ribbed belt is 41". 84-86 NAs use 37" belts. If you run the V-belt setup with a passenger side mounted alternator, you need a shorter belt. I used 32", I just went out and remeasured it.

btw, FWIW my tensioner is pretty loose in its ~3" of travel to use the 32" belt, you could get it to the more normal position with a 34 or so I'm sure.

This is weird, as I'm positive of my measurements as well. And Zfast88Z said OEM belts are 41 inches, which is what I got off my belt for the crank, alternator and water pump combination. I have a turbo (passenger side alternator) and I think you do as well. The only difference might be the alternators, but 10 inches less in length ???? No way. OK … try measuring a hypothetical belt going from just your crank to the alternator and back --- a simple 2-pulley loop. Use a string and see what you come up with. I can't imagine it being much less than 31 inches.

PS: Are you using a stock crank pulley, or an underdrive unit?

[quote]NewJerseyZ wrote:

Originally posted by michaelp

I'm still positive I have a 32" belt.

The ribbed belt is 41". 84-86 NAs use 37" belts. If you run the V-belt setup with a passenger side mounted alternator, you need a shorter belt. I used 32", I just went out and remeasured it.
This is weird, as I'm positive of my measurements as well. And Zfast88Z

IDK, I have a V-belt setup from a NA though, with the alt mounted on the passenger side. Like I said, its possible my measurements came out wrong. The whole reason I had to measure and get a custom belt is because there wasn't one I could just order for the Z31 when using the v-belts and the alt on the passenger side. Ribbed belts have larger pulleys where the belt rides on though, which im sure makes up a few inches on its own.

OK then … you're not using the OEM belt which is defined as Micro-V, which is not a standard V-belt. You are using a V-belt. The OEM part for my car for that belt is 41 inches (1028mm). Courtesy Nissan confirms this. Pulley size and exact location may very well play a role as well in all this.

Well, all I can say is that if you do use an electric water pump, have a Maxima alternator and stock crank pulley, you'll need a Micro-V 4-rib belt about 30 to 31 inches in length. Anything other than that will have to be measured by the user.

:super I'll triple check my belt setup later to see for sure. I do remember my string ended up being the wrong size even though it fit around the pulleys perfectly, now that I think back more it may be that the string measured 31" but the belt size I needed was closer to 35 or 36, it was off by quite a few inches which didn't make sense to me at the time.

You're absolutely correct … there should not be that much of a difference. From the inner most portion of the belt to the outer most, the length difference is trivial. If you ran a belt around the entire Earth and compared its length to a similar one that was 1 foot above the surface (all the way around the planet), the difference would be ..... ~ 6 feet. For the alternator belt (assuming 3/16 inch total cross sectional height), we're talking ~ 1.2 inches.

OK … something of an update:

I spoke (e-mailed) with Brett Dempsey at BDE, who said that his pumps are now coming with modified vanes (curved) that are more efficient than straight ones. The motor is a brushed type from CSR that (according to technicians at CSR) should NOT be run with reduced voltage to regulate their speed. So my initial mention of using a variable voltage controller is a no-no. However, the controller form DC Control will be fine, as it uses PWM control, and is fine with brushed motors (agreed with by CSR as well). The model 50P35 seems like the best choice, since it will not only run the EWP, but electric fan as well (which will likely now be a necessity).

Also, I sized up an actual 31 inch 4-ribbed belt from the crank pulley to my Maxima 90 amp alternator (passenger side). It's the correct size --- but it might also work up to a full 32 inch belt as well due to the swing allowed from the pulley mount.

Further update ....

For those who are still interested in what is needed to go this route, let me say 2 things:

1) The electric CSR water pump modified by BDE will fit the VG30ET engine block. The adapter plate does seat properly against the water inlet/outlet channels with no interference from the pump vanes or body housing. However, this will only occur if the thermostat housing body (2 piece assembly) is raised 0.25 inches (1/4 inch) up from its original mounting location. Otherwise, it will obstruct the mounting adapter plate of the pump. This actually is easily accomplished in my second issue.

2) The thermostat housing assembly must be raised along its 2 (two) mounting bolts 0.25 inches. Loosening those two bolts enough to lift the housing (without actually removing them) will then allow the pump's adapter plate to bolt onto the engine block. The remaining thing to now do is have constructed a spacer plate (aluminum is perfect) to the outline of the thermostat housing gasket (this is not the thermostat gasket). I had a local machine shop fabricate one for me. But this piece has one little caveat, and that is that both mounting surfaces are not exactly parallel. Lifting the housing up 0.25 inches actually arcs the assembly somewhat due to it having a long tube connected to the back of it, which runs to the car's heater core. Don't worry, there is enough give in the tube to allow for such small movement. From measuring to where it's anchored near the engine's rear, I calculated a difference of ~1 degree offset between the surfaces. This may sound trivial, but trust me, I had this all done and everything mounts up flush --- a very OEM looking job.

The housing bolts must now be replaced with longer ones to allow for the spacer's thickness. And yes, there is ample space in the housing's bolt holes to still get a good tight assembly with straight bolts. The difference in the housing's location is so small that the hose connecting the thermostat's inlet will still connect to the metal suction tube that runs to the lower radiator hose. Also, one might have to cut a small amount off the recirculation hose due to the housing sitting a bit closer to the manifold outlet casting (the piece that contains the "radiator" cap).

I'll be glad to answer any questions anyone might have.

I don't know why you would rather spend all that money when you can get an off the shelf kit proven to work. the BDE kit is 600+

http://www.jegs.com/i/Moroso/710/63750/10002/-1