[135i2]

BEV Single Turbo


RHD Low Mount

Write-Up Contents

A) Background
B) So, why change a thing?
C) The Project – Stage One
D) The Project – Stage Two
E) So, why a big single you ask? …And a low mount one at that?
F) So, why not twin turbo or top mount single?
G) Summary


A) Background

Purchased my 135i Auto new in 2008. Modified in the first week of ownership and still going. First was a Procede, filters, full exhaust (super sprint) then meth and a whole lot of other bolt-on parts that were good for 300rwkw for a few years. The car was being returned to stock for sale until I decided that it couldn’t be replaced with anything fast enough I could realistically afford.

Then came the current mods for 422+rwkw:

All new serviceable bits – water pump, HPFP, coil packs, NGKs, boost solenoids, etc…
Lots of performance bolts-ons


B) So, why change a thing?

Well simple answer really. Unreliable hybrid twins that gave up after 2500kms!
I just don’t want to keep spending money on the latest a greatest twin solution multiple times over to maybe find a reliable setup.
Not a fan of, “….run them at 18-20psi or they’ll blow up!”

C) The Project – Stage One

After lots of research and discussion with JD75, I purchased a Motiv 900 kit as this would likely be the closest possible fit for RHD. Maybe.

THE BRIEF. Single Turbo on a standard block with all the bolt on parts that I already have. Let’s see how far a good-sized single turbo can go without destroying the engine and gearbox.

What bought on this current bout of madness?
More power disease perhaps, no such thing as too much, right?
How far can we push these cars? Maybe.
More likely it’s the desire to do things once, not twice or three times…and reliably.

So, a single turbo was always the logical choice and I got sick of waiting for someone else to do it to a high standard for RHD. And not in your face when you open the bonnet.

D) The Project – Stage Two

Stage two would be a full engine and gearbox build with all the latest performance offerings to push the envelope even further as there is no way my engine and box will survive a big single at full noise when pushing the power levels to the max.

One of the other issues is that many a punter is discovering the limitation of the N54 motor itself and let’s not forget the transmissions, no matter what your flavour. Auto, manual (if your name is Marty) and the DCT boys. We will no doubt learn of other, relative fragilities as our cars get older and more powerful.

Stage Two Parts:

Motiv closed deck block
Motiv ARP head studs
VAC stage 3 head
Schrick cams
PPM billet crankshaft
Carillo rods
CP-Carillo pistons
Carr rod bolts
MAD Auto Monster IC
Fab Factory Intake plenum
ATI Super Damper
Nizpro Box Upgraded & Tuned TCU


E) So, why a big single you ask? …And a low mount one at that?

Reliability! There are now numerous 400+rwkw cars on our roads. Many of these cars are now pushing towards 450rwkw as turbos, tunes and other bolt-on products are refined for the N54 platform. But, there have been a litany of hybrid failures that many have not talked about for a variety of reasons.

1. Reliability – Big ball-bearing singles are built to take big boost and make big power.
2. Removal and re-installation - Easy to remove and reinstall.
3. Cost effective to rebuild – Especially if using local Garrett products.
4. Low mount installation – offers stealth location away from prying eyes and less melted sensitive parts.
5. Variety of turbo selections & brands – So many choices to tailor spool and power to your needs.
6. Not dealing with overseas companies - Restrictive warranty policies and poor product support.
7. Shipping, GST & Duty – Sending stuff back to the turbo hot shop time after time = $

F) So, why not twin turbo or top mount single?

1. Hybrid Twin Reliability – Hybrid twins have proven to be less than completely reliable when pushing the power limits of the N54. Some brands are having greater success than others but there is a litany of unhappy campers that are on their second and third sets of hybrid twins. Cost, ouch! Go to #2.

My platform leading hybrids (at the time) lasted less than 2500kms, despite the manufacturer claiming they were built for high boost and push them as hard as you like.

2. Hybrid Twin Cost - Rebuilding and replacing hybrid twins is expensive when you factor in exchange rate, removal and reinstallation, and let’s not forget international shipping (there and back), GST and duty are also possible costs.

All this palaver two or three times over as you search for the “most reliable” option!! At $5000-7000 plus removal and reinstallation more than once becomes very, very expensive.

3. Hybrid Twin Add-Ons - Don’t forget to add all the performance extra goodies to make your hybrid or big twins fit, the numerous cold and hot side do-dads required to make these works well. Ah, the sounds of the cash register ringing. Again.

4. RHD Space - Well there is none. There is little room left in a RHD car due to the steering shaft, knuckle and rack. I suggest if you haven’t eyeballed the space we have left for any RHD turbo product, you should. Add to that, the water pump sits directly in front of that lot and the only room left is for a compact top mount (compared to LHD top mounts) or a low-slung bottom mount.

Manufacturing and fabricating anything with the extreme space limitations of our RHD cars also cost much more in comparison with producing solutions with more room and access. Simples.

It’s a little depressing given the plethora of new ball-bearing big twins and single turbo options available to LHD.

But it matters not because they won’t fit our cars. They are developed primarily for LHD cars and just won’t fit even with major modification!


5. Top Mount Single Turbo - Well this one is obvious, no? Our motoring authorities, along with the brave men and women that enforce the laws in this land of milk and honey, will turn you into a criminal for having such a depraved hobby and passion. Flaunting such obvious modifications in the face of “Junior RBT” could bring a whole world of hurt and pain, because citizen, you know that speed kills.

Ok, top mount. Great for a race car where you can toss out lots of stuff in the way or bits that melt. Not so good if you want to fly under the radar, without completely “engineering” your chariot, then still getting thrown off the road anyway.

You can no longer assume that you won’t be pulled over because you seem like a nice old, conservative and a respectable citizen driving your not so understated BMW. There is no way you'd void your warranty with an uncouth modification or make it look more "dope". Right?

It is however, tempting to squeeze a big EFR up top and go racing…. Bad dog!


G) Summary

Car development and modification takes time. The RHD big single has been no exception. The goal is to get this kit on my stock engine N54 early next year and see what kind of results are possible without pushing too far. Tuning will be a learning curve for Justin, initially. Stage two will come once I get to use my car for a while and there is a good understanding of the cars characteristics.