[Biginboca]

So tetsuo111 had this idea which he had seen on other platforms, replacing the serpentine belt driven power steering pump with an electric pump. Porsche has this for some of their GT cars and its popular on Honda’s and a few other platforms. It frees up somewhere between 6 and 10hp, and puts a less than 1hp added draw on the alternator (5-40amps depending on steering load). So maybe some free HP there to uncork.

Of course once he shared it I got obsessed lol. Doing a lot of reading and research I discovered that there was one N52 car sold in the US which had the 3 stage and wasn’t rated to 255hp. The Z4 3.0si had 261hp and coincidentally also had an electric rack with no power steering pump.

Normal 330/328 N52 on top and Z4 N52 on bottom:



So that kind of led me to believe the Z4 probably got it’s extra 6hp from the deleting of the PS pump. Seeing that makes this very much worth exploring to me. I also found exactly one other N52 car in Wikipedia rated at 261hp and browsing realoem showed it also had an available electric steering rack:



Seeing all this gave me enough encouragement to explore this hypothesis a bit and I ordered a Z4 serpentine belt to try on my car. I want to take a few dragy runs bypassing the hydraulic steering pump and then immediately swap back and take a few with the normal serpentine belt and see how they compare. Dragy gives me a resolution of about 2-3hp from experience so if it shows any gains then this might be worth exploring more to me.

The way this would work would be to look for an electric powered hydraulic steering pump and keep the existing rack. So with this you would keep your hydraulic steering feel and gain some HP at the same time. This is a popular mod with hot rod and track car builders.

There are a few pumps available, a Mini Cooper pump, a Porsche/Mercedes A class pump, TRW pump for many platforms, and the one I’m considering is a Toyota pump from the 2000-2005 MR2 spyder. It’s an all in one unit with integrated reservoir and sensors to control the amount of assistance based on pressure. From the research I’ve done the Toyota looks the most compact and reliable. (This would not be the first Toyota parts I’ve installed on my car btw lol)



So the easy way to hook it up is power/ground/and accessory (turn on with ignition).

So once I do some initial testing with the Z4 serpentine belt (and if this looks worthwhile) the challenges will be:

1: Mounting Location and Bracket
2: High Pressure Line to mate Pump to Rack
3: Accessory On lead under hood to trigger pump turn on. Ideally this would be a wire that only gets hot when the engine is running. Maybe something from the alternator?

I’m putting this on the forum because I want to open discussion about the viability of this swap and also solving the challenges. I’m thinking to mount the Toyota pump where the OEM reservoir goes. The pressure line can be fabricated easily I’m sure.

But I have no idea where to pick up a trigger wire. Is there such a thing as a lead that only gets active when the engine is running, preferably under hood? Not just accessory on, but only hot when the motor is actually running?

[Biginboca]

Originally Posted by freedomfries

Have you driven a Z4 with EPS? I would personally never give up the E9x steering feel for "maybe" 6 bhp but still interested to see where this goes!

You would give up no feel. You keep your rack. You only swap your pump.

[bluewater328]

Well water pump is on during accessory 1 but it takes a trigger to make it cycle. Maybe somewhere in that realm of wiring?

[HydroxFrost]

I feel like its definitely worth a shot if you can find the part for a good price and have the time to fabricate this. For the average DIYer though probably not worth it as you don't net much to the wheels, but for someone trying to squeeze out every last bit of power for an NA build I'd say go for it. I might even be interested in doing this myself.

[Biginboca]

Originally Posted by HydroxFrost

I feel like its definitely worth a shot if you can find the part for a good price and have the time to fabricate this. For the average DIYer though probably not worth it as you don't net much to the wheels, but for someone trying to squeeze out every last bit of power for an NA build I'd say go for it. I might even be interested in doing this myself.

Yes that’s where I’m at. N/A hp is hard to come by and the low hanging fruit on the N52 are long gone for me so I’m looking into this.

[jonwilli]

I did exactly the opposite of this

I have a 2007 E81 130i with EPAS that I converted to run HPAS with the E92 M3 steering rack. It was all a straight swap and no ECU codes with the EPAS unplugged and stored away next to the ABS pump. The serpentine belt will run fine too.

I did think about fitting a Mini or Toyota electric pump to simplify the install and then decided I wanted it to look and feel 100% OEM. I have to say I can't 'feel' any difference in power swapping from EPAS to HPAS so it will be interesting what your draggy times show.

M3 HPAS has got to be one of my favourite mods. I had the car just how I wanted it but jumping from HPAS cars into it always highlighted that the steering feel was a bit shit! I never noticed the EPAS was that bad until I was regularly driving an HPAS 130i and 135i.

[gT-BMW]

have you consider electric turbo? lol

[Biginboca]

Originally Posted by gT-BMW

have you consider electric turbo? lol

Not a fan of the electric turbo... plus it’s too pricey lol

[neilvan]

People have done this on Miatas(MR2 pumps) just to reduce the engine losses so im sure its doable to these

Most of europe, the LCI E90s had electric steering racks/pumps and those engines did not gain any HP(could be just not listed either).

I wonder if the z4 just had a better intake or exhaust to get the extra power. It is a different design and even the same designed one(N54) had a different lid.

That being said reducing losses, chances are you will get gains.

[4foothill]

Originally Posted by neilvan

People have done this on Miatas(MR2 pumps) just to reduce the engine losses so im sure its doable to these

Most of europe, the LCI E90s had electric steering racks/pumps and those engines did not gain any HP(could be just not listed either).

I wonder if the z4 just had a better intake or exhaust to get the extra power. It is a different design and even the same designed one(N54) had a different lid.

That being said reducing losses, chances are you will get gains.

The n53 has EPS and is rated at a slightly higher HP, but I think it does also run at a higher compression so it could be from that.

[neilvan]

Originally Posted by 4foothill

The n53 has EPS and is rated at a slightly higher HP, but I think it does also run at a higher compression so it could be from that.

N53 cars had higher HP with the electric steering vs hydraulic steering models?

Over here we never got the N53; Just know its the N52 w/n54 direct injection

[rjahl]

Originally Posted by neilvan

N53 cars had higher HP with the electric steering vs hydraulic steering models?

Over here we never got the N53; Just know its the N52 w/n54 direct injection

Go back a generation and look at the E85, the 3.0 SI had electronic steering and rated at the same 255HP.

The E89 had a better rating but it also had a better exhaust system.

[Biginboca]

Originally Posted by rjahl

Go back a generation and look at the E85, the 3.0 SI had electronic steering and rated at the same 255HP.

The E89 had a better rating but it also had a better exhaust system.

Looking at realoem the exhaust system looks no different from the other US n52 cars. I see crappy headers with poorly optimized 3 into 1 sections and a integrated catalyst, I see secondary catalyst, and I see a muffler.

I see all the same components the other cars have just laid out slightly different for what I assume is packaging constraints, and don’t see any differences that would seem to lend even 1hp. Also not even aftermarket exhaust companies with open mufflers claim 6hp gains for our cars. It’s well accepted that without deleting cats you are not going to increase power much with exhaust mods.

[Noir]

Biginboca the part numbers are universal for the exhaust piping between all the n52 applications? My pure speculation/guess would be that the piping would be shorter on the z4. But I also can't see the z4 being all that much shorter...

[Biginboca]

Originally Posted by Noir

Biginboca the part numbers are universal for the exhaust piping between all the n52 applications? My pure speculation/guess would be that the piping would be shorter on the z4. But I also can't see the z4 being all that much shorter...

Those parts are unique numbers to the Z4

[ornicar]

Originally Posted by Biginboca

Those parts are unique numbers to the Z4

i don't know on the Z4 but on 130i by example there were 2 differents headers design . the realoem drawing is Not up to date.

First photo is the old design and second the new one.



the oldest have some harmonized pipes length. In my opinion that may explain the little difference in hp (258 vs 265) but who really know without doing a before after swap with Dyno measure .

[E92William]

Do all Z4s have the electric power steering pump? And by that I mean 3.0i vs 3.0si. We're doing a 3 stage manifold swap into a buddies z4 3.0i and flashing the bimmerlabs 3.0si tune on it, and he has another z4 an original 3.0si so if there was any difference it'll be noticeable.

Also which rating is correct? It seems numbers like 255 to 268 are thrown around all the time to rate the highest output N52 powered cars such as the z4 3.0si and the e70 x5 even sometimes. Hopefully the difference is the pump but that's some serious load if it takes 6 hp to run IMO. Also I think a lot of n52 cars have had the n53 euro version of them and it's output thrown on them here in the us. No way a bone stock car does 272hp as I've read in some websites.

[rjahl]

Originally Posted by E92William

Do all Z4s have the electric power steering pump? And by that I mean 3.0i vs 3.0si. We're doing a 3 stage manifold swap into a buddies z4 3.0i and flashing the bimmerlabs 3.0si tune on it, and he has another z4 an original 3.0si so if there was any difference it'll be noticeable.

Also which rating is correct? It seems numbers like 255 to 268 are thrown around all the time to rate the highest output N52 powered cars such as the z4 3.0si and the e70 x5 even sometimes. Hopefully the difference is the pump but that's some serious load if it takes 6 hp to run IMO. Also I think a lot of n52 cars have had the n53 euro version of them and it's output thrown on them here in the us. No way a bone stock car does 272hp as I've read in some websites.

All N52 versions of the E85 had power steering. The 3.0SI was rated at 255 HP, The same engine in the E89 with power steering was rated at 258 HP.

Too many people are getting the US ratting HP confused with PS used for the EU cars.

Then you had the direct injection N53 rated at 272 PS as it was only sold overseas.

[rjahl]

Originally Posted by rjahl

All N52 versions of the E85 had power steering. The 3.0SI was rated at 255 HP, The same engine in the E89 with power steering was rated at 258 HP.

Too many people are getting the US ratting HP confused with PS used for the EU cars.

Then you had the direct injection N53 rated at 272 PS as it was only sold overseas.

For giggles I dug up some of my old research and I can say today's internet information is now even worse than it was 6 years ago.

The best current data source I could find was

www.auto-brochures.com

Actual PDFs from BMW marketing materials. I'd consider BMW the best source available.

The SUVs did seem to have the highest rating at 260. They also had the least problems with space for the exhaust manifolds.

https://www.auto-brochures.com/makes...%20X3_2009.pdf

[200,000 club]

I might delete my A/C. It wasnt working when I got the car and it wasnt so bad. Maybe that will also give some gains

[CTinline-six]

Originally Posted by 200,000 club

I might delete my A/C. It wasnt working when I got the car and it wasnt so bad. Maybe that will also give some gains

It won't matter.

The only time it will make a difference is when you'd normally be running the A/C. All of the other times the compressor clutch is disengaged and freewheeling. If you are running the AC a lot then you'd probably want to keep it.

I'm also skeptical that switching to electric P/S will net a 6 hp gain. Even the mpg gain for most cars that have switched to completely electric racks is negligible. 1-2hp maybe, but not 6hp.

[200,000 club]

Originally Posted by CTinline-six

It won't matter.

The only time it will make a difference is when you'd normally be running the A/C. All of the other times the compressor clutch is disengaged and freewheeling. If you are running the AC a lot then you'd probably want to keep it.

I'm also skeptical that switching to electric P/S will net a 6 hp gain. Even the mpg gain for most cars that have switched to completely electric racks is negligible. 1-2hp maybe, but not 6hp.

Damn, maybe I'll find some more luck with a vanos delete