Thursday, May 11, 2017

mini love - part 6

With the engine out, all the modifications that I planned for the engine/drivetrain should be relative easy to install, and so I thought.

I start the day early as the afternoon sun have been merciless especially working under the sky on a concrete driveway.

starting with the easiest task - replacing the supercharger pulley with a 15% diameter reduction - hence the supercharger will spin 15% faster

A little bit is good, and a lot rarely is good. In the early years of the first generation modern Mini a lot of owners installed 17%, 19%. Some went as far as swapping the crank pulley with a 2% increase in conjunction with a 19% reduction pulley, giving net result of 21% increase of supercharger rpm. The problem is huge rise of charged air temperature which quickly diminishes the benefit of increase boost. With a decade of cumulative experiences the current wisdom is 15% is ideal for a stock engine and only go smaller if there are significant modifications to the cylinder head, exhaust, fuel injectors and ECU re-mapping.

For me 15% pulley is low hanging fruit while maintain excellent engine and drivetrain longevity.

I replaced the belt tensioner even though the existing one is in excellent condition

I bought an AC Delco brand for less than 1/2 the cost of Mini brand but the part is identical except with the Mini branding and part market grounded off; they both are made by Litens; the miniature damper on them is made by Stabilus in Germany

a special purpose-made pulley puller is required to remove the existing pulley without causing damage to the supercharger input shaft; it is interference fit so it took a lot of torque applying to the pulley extractor to extract it

I added a hose clamp to secure the puller from slipping as failure is not an option with this step

I chosen the Craven Speed stainless steel pulley over the Alta's aluminum for longevity

this is the special tool requires to release the belt tensioner for this job

more steel brackets; note that only the B+ cable to the starter from the car needs to be disconnected for engine removal

this is a steel bracket that supports two small diameter coolant steel lines

there is this crescent moon shape steel cover behind the starter

the next task is to separate the transmission from the engine

I am glad that I chose not to try separate the transmission from the engine with the engine in the car

Most owner who go to the trouble like me to install a limited slip differential will want to replace the clutch and flywheel no matter what condition they are in. I have formed a good habit of very easy on the clutches and I expect mine to be in excellent condition.  This will be the moment of truth if my expectation is true. The proof is in the condition of the wearable parts of the clutch system.

I did a lot of research on which after market replacement clutch kit to buy. I was leaning towards one of street level 2 kit from South Bend that cost about $1,000. As I think of the difference between a utility clutch kit and the performance kit, I came to the conclusion that I don't want to spend that much for the little differences. Soon I begin to want to take a path less traveled. Instead of going with the Valeo kit which is almost a standard answer on Mini forums I wanted to take a chance with a kit by Exede. The cost of both kit is very close at about $350.

the factory flywheel (left) and the new single mass Exedy flywheel (right); about 27.5 lb versus 18.5 lb giving a weight reduction of 33%

you can still see the machining marks on the clutch surface of the flywheel - so the flywheel has virtually no wear; the same is true with the pressure plate

this is the Exedy single mass flywheel

my neighbor lent me a flywheel holding tool which make installing the new flywheel really easy

compared to the factory friction plate the friction liners on the Exedy clutch is very similar with high metal content

I measured the thickness of the friction plates. The factory one (with 42,000 miles of service) comes to 7.58mm while the new plate measured 8.04mm. I only worn down the friction plate by 0.42mm driving 42,000 miles, assuming a nominal thickness of 8.00mm when new.

factory disc (top) and the new Exedy disc (bottom)

both discs are 8.5 inch diameter; the difference is the shock absorbing springs on the single mass clutch kit with the single mass flywheel

there is no oil residue in the bell housing; just clutch dust and soot from the road

the new Exedy clutch mounted on the new flywheel

the existing release bearing and the collar it slides on are in excellent shape; I am also very easy on release bearing by only depressing the clutch to get into gear when the traffic light changes; I replace the release bearing with the one included in the Exedy clutch kit; it is identical to the factory one with identical part markings - made in France

I installed a new release bearing

there are two momentum weights on the gear shift lever to help slam into and out of gear

With the new clutch installed, the next task is to install the Quaife LSD. I credit my planning that I already have the two supporting bearings pressed onto the Quaife LSD by the fine folk at Napa Auto Parts near me without charge.

unlike a rear wheel drive car the differential does not need side lash shims as there is no worm gear; the final drive are just helical cut gears

The Getrag gear box is in pristine condition. The magnet that collects all the steel particles in the gear oil has very little metal particles and the gear oil that I drained is clear.

this is the top half of the gear box housing you want to lift off

I used a small hammer to tap loose the ring gear from the existing open-differential after removing all the machine bolts. The ring gear is then transfer to the Quaife LSD and the bolts re-installed.

One thing that totally escaped me during planning. I didn't think of how to replace the outer bearing races with those of the new SKL BR35 bearings, nor did I procure the two axle seals. Inspecting them I think one has to remove and damage the end seals to be able to tap them out of the gearbox casing. I decided to take a calculated risk - reusing the existing outer bearing races with the new inner bearings. I decided it is low risk as they are the same brand of bearing and the existing bearing shows no signs of wear.

outer bearing race for the differential; it is so tempting to want to stick a flat blade screw driver into that slot on the casing to try prying it out; but I have my wits not to be tempted by the devil to wage the unneeded battle

installing the Quaife LSD into the transmission took about 1 hours being very careful

My neighbors were impressed seeing my major project. Let the truth be told. I tackled two broken manual gearboxes and an automatic transmission during high school, all self-taught from getting my hands onto every auto repair books from the city library. I bought a low mileage Fiat 124 Sports coupe at a big discount because one gear of the 5-speed gearbox will keep popping out of gear. I managed to repair the gearbox. Later I reground all the valves and seats and replaced the harden valve stem seals.

I opted not to fill the gearbox with oil until the engine/drivetrain is back on the car so not have to deal with oil rushing out of the two axle ports

button things up for the night

the transmission is ready to be reinstalled onto the engine the next morning

I have been a grease monkey for many days, and clean my body with Simple Green degreaser instead of body soap

another day of good weather and was the day to return the engine to the Mini

I use electrician's tape to hold the exhaust gasket to the header and a string to hold the heat shield in place

i protected the spines and seal contact surface of the axle while maneuver the engine into place

I also replace the o-ring on the crank position sensor; it has deformed to square cross section from engine heat and long term compression

I decided to remove the unnecessary secondary connector locking tab

I wanted to check that the clutch was install correctly; I use this wrench as lever to activate the clutch lever and it felt normal

more photo to document the engine anxilaries

 all the harnesses and hoses can only be routed one way

reverse light switch for the gearbox

note how clean is the trailing side of the transverse mounted engine; there is no sign of any oil leak from the cylinder head cover or oil pan gaskets

I tried to hoist the engine into the car by myself to no avail; and the engine is hoisted too high to go in this way. I could have done this all by myself have it not because of the very rough driveway pavement surface making maneuvering of the engine hoist a one person's job leaving him unable to guide the engine carefully into the tight Mini front end.

Once the engine is back into the engine mount the work ahead is hardly easy. Each reconnection took a lot of time and I have to double check the cable harnesses are routed properly. I had a couple of connectors that I could not determine where they go until long time later.

this one connector thew me into a spin as where it goes, but eventually I would realize it goes to the power steering cooling fan under the vehicle; what was it doing here on the right side of the engine?

the day is getting old trying to rush to a point to be able to start up the engine/drivetrain

the gear selector cables are very difficult to remove and reinstall without causing damage to the plastic bracket that keep them in position; to loose gear shift while driving is not something you want to occur

closeup of the plastic gear selector cable bracket that can easily be damage by a careless mechanic

the gear selector cables with the wire spring clips that engage and lock into the barbs of the cable bracket

this engine bay is jam packed

I am really glad that I made the decision to remove as little of the engine electrical harnesses, fuel, oil, and coolant lines as possible. A lot of these things are the the less disturbance the better for longevity.

eventually the radiator is back onto the car as is the AC evaporator

more steel brackets - this one is for the AMS

the infamous octopus wire harness of the engine which I didn't want to remove like most people do when removing the engine

the plastic clutch slave cylinder is return back into position

I took detail photo of the intake air filter enclosure - so that I can design a modification; I find most after market "cold air intake" poorly designed and made, especially the poorly fitted hoses

this smaller 1.5" diameter port sucks air from the driver side cowl

this 2 1/4" diameter port connects to the tuned ducting from the front of the car

I spent a lot of time examining the design of the stock air intake filter box. I think given the severe space constrains BMW had done an excellent job. I do not believe that the air box system suffers from inadequate fresh air input, or sucking hot air. There are two air inlets, one is a tuned duct on top but leading the radiator. The other is a 1.5 inch diameter hole that opens to the driver side cowl. I believe most aftermarket "cold air intake" products do little to improve the air filtration performance except deliver louder supercharged intake sound because most do away the sound muffling. At this point, my thought is if I want to slight increase the supercharged intake sound, I would keep the entire factory air intake filter system but modify it to use a cone/cylinder type filter element like the K&N.

I would want to conduct air pressure test comparison before making any modification to the filter box system.

K&N filter element

I was able to reuse all the factory stainless steel air hose clamps using this improvised tool

If there is one tool that I wish I own it is a spring clamp pliers. I used Vice Grips, Channel Lok pliers, and general purpose pliers to remove and re-install countless factory spring clamps. With these awkward improvised tool the job took way too much time. I promise that I would be good to myself and invest in a set of hose clamp pliers after this project.

next is to re-fill the gearbox with gear oil; this synthetic oil has noticeable lower viscosity than the factory oil so I expect to result in lighter gear shift effort

next I want to install the factory fog light kit that I have since the car was new

Putting the modular front end back took me a lot of time for being inexperience. I have to recall which fasteners go where and also ensure the proper alignments of many interrelated pieces. I managed to carefully triple-checked everything. The car was ready to be started for the first time after the reassembling. Many things can go wrong that can spell disaster so one cannot perform checks too many time until one is certain all are good.

I planned to incrementally perform a number of test. First I want to test the clutch function as well as the transmission, and drive axles. As I had been pounding the drive axles trying to separate them from the wheel hubs, I was very worry that I may have damaged the wheel bearings. After putting the engine/tranny back onto the car but before reinstalling the front end, I tested the drivetrain while the Min was still up on the jack stands. I wanted check out the new clutch/flywheel, the LSD, and most important, the two axles and wheel bearings are not damaged. Guess what?

The front hubs/axles spun smoothly on 1st, 2nd, and 3rd gear. When I slowly and carefully increase the axle rpm in 4th gear, the driveline shakes! My heart sank and I thought I damaged the wheel bearing pounding with a 4lb hammer trying to drive the axle from the wheel hub. The other possibility is I did not align the right side axle which has a center supporting bearing.

I tried to keep a cool head, and pause for a moment to think instead of panic. The vibration is very periodic, and not very violent. I immediately suspect the DSC (Mini's driver safety assistant) doing strange things as only the front wheels are spinning during my spin test. The drivetrain computer was pulsing the disc brakes in the confusion. I switched off the DSC and sure enough, the drivelines were smooth as silk spinning with the car on jack stands without the front wheels. My neighbor and I breathed a big sign of relief.

Next I went around the block for a low speed test drive without the bumper and bumper cover. The car ran so smooth like new. This low speed test drive proved to be wise. The air conditioner did not work when I tested it. I remembered when I re-installed the compressor I was unsure about the proper routing of the single electrical contact AC compressor harness. It didn't register in my mind that I decided to only reconnected the plug into the receptacle halfway thinking that I would have to remove it. With the bumper and bumper cover still off the car checking this was extremely easy as you could see it looking up from under the front end. That was the single thing that required correction of this entire project.

I return home and installed the crash tubes, the bumper and bumper cover and reconnected all the lights and the ambient air temperature sensor. Until you have done this a few time it take a lot of time to figure out a systematic way of reassembling the front end so that all the fasteners return to the right places, and the pieces are properly aligned.

I then performed road test with incremental speeds to look for any sign of noise, vibration, smoke, fluid leak, while keeping a close eye on engine temperature. By early evening I felt comfortable to go for a spirited test drive on the twisties.

The modifications all together are transformational. The suspension is excellent and so precise and responsive now is the steering. The higher boost of the supercharger is very noticeable and it is now so easy to spin both front wheels. The clutch engagement is sharper because of the single mass flywheel. There is a slight rawness now with the drivetrain, but without pronounced vibration as the new 18.5 lb flywheel is still quite streetable. The Quaife LSD keeps both wheels rotate when the one tire try to slip. The car is so much faster and easier to drive fast, indeed very fast. What I didn't immediately realize the pleasure of the engine power delivery is how fast the rpm spools up. I was so mesmerized with the 15% supercharger pulley I forgot the effect of the now lighter flywheel. The car now is now sheer delight to drive fast or slow and feel well balanced on the whole.

I feel that my selections of the components proved to be well matched. It had been so easily to be tempted to go with highly touted performance components and ending in a poorly balanced car. To name a few common pitfalls:
Wheels too big. Tires too wide. Suspension spring rate too high. Ride height drop too radical. Dampers too strong or too weak. Sway bar too strong or too weak. Front racing camber plates that has no compliant material function as shock isolator. Clutch and flywheel too radical for road use.

I have been careful not to go hog wild with a big list of suspension modifications including swapping all the rubber bushings with polyurethane ones. Right now the steering is very responsive and tight so for the near future I do not foresee the desire to make the change. The Swift springs and the Koni Yellow dampers are good match. The Swift spring rates are 280 lb/in front and 308 lb/in rear. They are progressive rate design. The car has almost no lean when pushed to the limit of tire adhesion which puzzles me when I hand compressed the stock springs and the Swift springs. The Swift springs are definitely softer at free height. The answer must lie with the progressive rate design. When loaded with the corner weight of the car the Swift spring reaches the nominal published rate and the suspension is rock solid. It is one of the firmest suspension I've ever experienced. Looking into the front wheel well I could see that most of the spring windings are collapsed together. Only about 1 1/2 turns are left to be compressed further. It is so similar to the classic Mini (the classic Mini Coopers use rubber donuts as suspension springs). My Mini uses coil spring, in conjunction with the bump stops as suspension springs.

I have done quite well in planning and executing this project. I used all the parts that I order with the exception of the rear main crank oil seal. Inspected and found no trace of leak I decided to better leave the factory one alone instead of installing the Felco brand that I bought. My friend had similar engine/drivetrain modifications performed by a Mini specialist shop. The shop replaced this seal. After completing the job and return the Mini back to my friend, the new seal started to leak. This Mini specialist shop, which I won't name, have to take out the transmission again to install another new seal. I suspect the Mini specialty shop simply screwed up the first time around as engine oil seals OEM suppliers make these parts by the millions with few failures due to defects. I didn't not need even to go get a part or supply that I needed during the project, except to borrow a couple of hand tools from my good neighbor.

my significant modifications is now complete and the improvements far exceed my expectations

I completed these modifications on the driveway during the few days of dry spell. The following day begins a week the weather returns to the soggy May.

no sooner the rain started the next day

The Mini fills my childhood desire of a pure driver's car like the Ford Escort MKI RS1600. The fun part is I performed all the modification work myself. Since new, no one but myself has service it (it had never even returned to the dealer for the new car break-in inspections) except me.


  1. Wow Nicely done, not only the amount of work done in your driveway but documenting it all for others to see. I know you mentioned that the purchase of the GT3 was the inspiration to up the performance of the mini, just a little surprised that you were able to wait all those years. How is the LSD performing?
    Would like one in my 08 GTI. I purchased mine new in 08 and once I started on the forums it was hard to resist the appeal of a better performing car. I'm at the stage now of returning it to semi stock, your removal of the front end of your car makes the task of replacing my coilovers so much easier to think about now.

    1. When I bought the Mini in 04, I was planning to partake stock class autocross frequently. However I tried track days and found it much more fun. I would have done a lot of mods but in 05 I move to the current mid century modern. For the next few years renovation work left no time for tinkering with the Mini. In a way I am glad that I do these mods now as there is 12 year of accumulated wisdom of others on forums. The LSD is immediately noticeable, especially with the 15% pulley the supercharge kicks in boost much sooner. LSD should really be standard in all FWD cars.

  2. Just bought a pair of these for working on the Passat; they saved a lot of time and skinned knuckles:

    1. This comment has been removed by the author.

    2. That was my initial top choice. However when I consider all the possible tight confine of the hose clamp situations, I realize the cable type design can actually work to the detriment in many situations. I shopped more on Amazon and I am leaning towards this low cost knockoff at the major investment of $12.99 :-) The head pieces of these rotates. The real thing pair is about $50.

  3. Let me know if you are going to run at PIR, we can see how badly your super charger boost and suspension will beat my Mini. Impressed with your diving into the internals, I feel competent to work on pre '70 stuff, not the new stuff.