P/S Pump Delete

[03whitegsr]

Has anybody removed the P/S pump and know which length belt to use?

I did some quick research and took a few measurements. The stock belt is 65" in length and it looks like a 57.5" belt would be about right to bypass the P/S pulley and go straight from the crank to the alternator.

Can anybody verify this is the correct length?

[rochey6957]

Whats the reason behind removing the power steering? just curios... Weight reduction?

[spidertri]

I haven't done it but you could use a piece of string to mock up the new belt and then measure that length.

[03whitegsr]

I've got an electric pump I'm going to replace the engine driven one with. I imagine it's about the same weight overall, maybe even slightly more heavy. The reasons though:

1. Mounting it in the back of the car, ~10 pounds off the front and ~10 more pounds on the back to help get it to 50/50.
2. Less drag on the engine.
3. One less thing to deal with on a future engine swap.

One more question, realoem has the pressure line marked as a 14x1.5mm on the fitting but only gives the diameter (16mm) for the return side. Anybody know the thread pitch?

[BimmerBum]

Originally Posted by 03whitegsr

I've got an electric pump I'm going to replace the engine driven one with. I imagine it's about the same weight overall, maybe even slightly more heavy. The reasons though:

1. Mounting it in the back of the car, ~10 pounds off the front and ~10 more pounds on the back to help get it to 50/50.
2. Less drag on the engine.
3. One less thing to deal with on a future engine swap.

I understand wanting to reduce drag on the engine but I don't follow you on any weight reduction or balance improvement. The stock pump weighs less than 5 lbs even if you factor in the pulley and the few inches more belt you need to operate the pump. If you mount your electric pump at the rear of the car you will need to run lines to it (weight) and you will need to fill those lines with fluid (more weight) and you will need to secure those lines with fasteners (even more weight). So where does the weight savings come in?

If you are worried about power steering complications down the line when you do a swap... don't. All you will need to do is replace your existing lines with E36 6 cylinder lines.

[03whitegsr]

I said above it likely weighs more overall and it's more a matter of where the weight goes.
Also, I won't be putting an I6 in it.

To each their own. I figure with the goal weight I have in mind, this change could actually amount to about 0.5% weight balance improvement.

Is "5lb" an accurate measurement or an estimate? The P/S system on my EVO is 13 pounds once you add in the reservoir, cooler loop, lines, and hardware. That car was built to be fairly light so 5 lbs seems awfully optimistic for the BMW.

[BimmerBum]

Originally Posted by 03whitegsr

I won't be putting an I6 in it.

Hey, to each their own. Figure with the goal weight I have in mind, this change could actually amount to about 0.5% weight balance improvement.

Is "5lb" an accurate measurement or an estimate?

The P/S system on my EVO is 13 pounds. That car was built to be fairly light...

It makes a little more sense if you are not doing the standard I6 twin cam swap but I would leave the electric pump in the engine bay, keeping the lines and fluid to a minimum.

My 'less than 5 lbs' statement was a guess but an educated one, I have handled my fair share of power steering pumps for 318's and BMW's in general. The pump on the ti is tiny and I would be surprised if it weighed 4 lbs.

I see your set up adding weight and the .5% weight balance improvement not happening as you will be adding weight almost the entire length of the wheelbase. A balance improvement that minimal is easily achieved with a set of coil overs and a corner balance.

Not trying to be down on your idea... I actually really like the idea of the electric pump, just not the placement you are thinking of.

The pump is almost removed from my Club Sport and I don't mind weighing it for you. How much does the electric pump weigh? How much does a foot of line weigh? How many additional feet will you need? How much more fluid that stock will your system hold? What's the weight of the additional fluid? The answers to these questions will tell you where to place your pump.

[spidertri]

Dang, Bimmerbum nailed it, 4.019lbs for the ZF pump and 3.876lbs for the LUK.
http://bmwfans.info/parts/catalog/E3...pump_mounting/

[BimmerBum]

Originally Posted by spidertri

Dang, Bimmerbum nailed it, 4.019lbs for the ZF pump and 3.876lbs for the LUK.
http://bmwfans.info/parts/catalog/E3...pump_mounting/

What's my prize!?

[03whitegsr]

Adding everything up there, I come up with 7.9 pounds. Admitedly, that is suprisingly light and will mean the new pump is a few pounds more heavy, defintiely not what I had hoped for.

For the sake of discusion though, the hose I will be using is 0.15 lb/ft and fluid weight per foot in the tube is 0.042 lb/ft. 20 ft of tube would add 3.8 pounds where the stock line are 2.25 lb without fluid. Doing some quick estimate-math, let's say the line is split F/R on the new line, new pump is 100% rear and OEM stuff is 100% front. Net results, it adds 6 pounds overall (definitely not the goal) but does produce a 0.4% weight shift to the rear of the car.

I have yet to weigh the MR2 pump, the MS3 pump was a hair over 10 pounds. I expect the MR2 pump to be very similar. I'll get a weight when it shows up.

If you like my placement idea or not doesn't matter for the sake of this thread though. I'm after belt length and thread pitch on the rack return line fitting!

Might not matter though, the only AN adapter fitting Fragola has is M16x1.5.

[BimmerBum]

Originally Posted by 03whitegsr

Adding everything up there, I come up with 7.9 pounds. Admitedly, that is suprisingly light and will mean the new pump is a few pounds more heavy, defintiely not what I had hoped for.

For the sake of discusion though, the hose I will be using is 0.15 lb/ft and fluid weight per foot in the tube is 0.042 lb/ft. 20 ft of tube would add 3.8 pounds where the stock line are 2.25 lb without fluid. Doing some quick estimate-math, let's say the line is split F/R on the new line, new pump is 100% rear and OEM stuff is 100% front. Net results, it adds 6 pounds overall (definitely not the goal) but does produce a 0.4% weight shift to the rear of the car.

Doing the math that way is easier but it misrepresents reality...

At best you are adding 10 lbs to the rear, removing 7.9 lbs from the front and adding 3.8 pounds to the entire length of the car with the lines and fluid... Your set up adds 7 lbs to the car.

As an aside... depending on the path you take to route the lines I think your 20 ft estimate may be shy of what you will actually need.

Anyway... I know you did not create this thread to have this discussion. Good luck with it an post some pics!

[03whitegsr]

There are some assupmtions that seem simple, but they are thought out and I have no doubt it would be within 10% of reality. FWIW, I'm a mechanical engineer in my professional life.

I don't mind the discussion if I can get the two answers I'm looking for as part of it.
Obviously I can figure it out as I go, but other then those two items, I have everything figured out and can order parts in advance instead of waiting until the car is apart then having to wait for stuff to show up.


A LOT of what I will do on this car will not make sense to many. Cars for me is about the journey, not the destination.

For example, I'm pretty sure I could reach my power goals with a turbo setup, I'm pretty well versed in making power on I4 turbo motors. But I'd rather have an N/A V8 with ITBs screaming at 9500 RPM, even if it cost 3x as much.

[BimmerBum]

No argument from me when it comes to N/A...

Proper belt length can be easily determined with a string... due to the range of motion in the tensioner you will have a small range of belt lengths that will work properly. That said you may very well run into an issue with the belt rubbing on itself at the underside of the tensioner pulley as the belt passes between the crank and the alternator.

[mohaughn]

Originally Posted by 03whitegsr

There are some assupmtions that seem simple, but they are thought out and I have no doubt it would be within 10% of reality. FWIW, I'm a mechanical engineer in my professional life.

I don't mind the discussion if I can get the two answers I'm looking for as part of it.
Obviously I can figure it out as I go, but other then those two items, I have everything figured out and can order parts in advance instead of waiting until the car is apart then having to wait for stuff to show up.


A LOT of what I will do on this car will not make sense to many. Cars for me is about the journey, not the destination.

For example, I'm pretty sure I could reach my power goals with a turbo setup, I'm pretty well versed in making power on I4 turbo motors. But I'd rather have an N/A V8 with ITBs screaming at 9500 RPM, even if it cost 3x as much.

Front to rear weight balance, aka 50/50 weight distribution is more of a marketting terms. I've not met any racers that scale their cars that are primarily worried about front to rear weight balance. They are typically more concerned about cross weight balance first, and then maybe front to rear balance if they are trying to correct a specific issue.

My advice to anybody that is making a performance car for track purposes is to think about your long term plans for the car, what group do you want to run with, what class, and what rules do those classes/groups have. Seems like a lot of money and effort on an electric fuel pump setup. The only cars I see running that kind of system at the track are the high end "unlimited" kind of cars that usually just have power/weight restrictions and can do anything else. The main purpose being removing parasitic drag on the motor or making more room in the engine bay for other mods. Typically the pump is put into the passenger side foot well to minimize pipe/tubing length.

A decent article that dispells some of the myths about 50/50 being the perfect weight balance. It really depends on the car, the driver, the course, tires, etc... http://www.circletrack.com/tipstrick...ion/index.html

[03whitegsr]

You can't move weight front to back with suspension height adjustments so looking at it on the scales while adjusting cross-weights is a waste of time. 50/50 weight balance is something you have to think of in the building stage. It's too late to worry about it once you are putting the car on scales to adjust cross weight.

Another big reason I'm doing it is simply to test it for application on my primary project car. I have a pump out of a Mazdaspeed 3 as well that has CAN bus for RPM, VSS, and TPS and I want to figure out the mechanical side of this pump and see how it works out before digging into the CAN side of things.

FWIW, the MR2 pump weighs in at 10.2 pounds.

Just a fun piece of info, this weekend auto-x had a new M3 in my class, built suspension, engine mods, and hoosier A6s. He beat me, but by 0.8 seconds on a 50 second course. I love driving the hell out of a POS car and running that close to $100k cars.