OKINAWA080

Considering Pedro's Underdrive Pulley Kit but read that IMS Bearing Replacement should be done before because of the need to shave down the "boss" or Top Dead Center bolt receiver/holder/whatever (not sure of technical term).

Can someone elaborate on why shaving down the "boss" may make this more difficult?

Can enough of the "hole" be left intact to use it as a TDC guide?

Any other problems experienced as a result of an Underdrive Pulley Kit?Recommend any other kit over Pedro's and why?

Thanks in advance.

Macster

Can't help you with the shaving the "boss" question.

I can offer that I'm not a fan of underdrive pulley setups. While one can get away with spinning the power steering pump and possibly the alternator at slower speeds, the last thing a hard working Boxster engine needs to slower flowing coolant.

You can see why for yourself: Get a flat bottom stove top pot and put in around an inch of water and place on the stove at high heat. After a while notice bubbles start to form. Gently move the pot in a circular fashion to swish the water around. Notice how the moving water dislodges the bubbles?

Let the water get hotter. The bubbles form faster now and are larger in size. One finds he has to move the pan with more vigor to remove the bubbles.

This is essentially what is happening in the Boxster's cooling system. The coolant needs to be circulated at a high rate of speed to help prevent the formation of those bubbles, pockets of steam, preventing them from getting too large.

If they are not removed where they form gets even hotter -- and they form at the hottest areas already -- and the bubbles/pockets of steam prevent coolant from contacting the hot spots and carrying away the heat. As a result localized overheating (and damage) can occur.

There are tubes cast in the head water passages to act a tiny jets to direct/aim coolant directly at the hottest spots to increase the velocity and force the coolant has to ensure no bubbles form and remain in place.

Slowing down the flow of coolant is the wrong way to go and for just a piddly amount of "HP" gain.

Far and away if one is tracking his car the biggest benefit in cutting lap times and increasing speed is not by making mods to the car -- other than those intended to help the car sustain the ravages of tracking (mods like better oiling) -- but in improving one's driving skill with expert guidance and counsel from a highly regarding driving instructor.

Not only does this make the driver a faster driver but a smoother driver which is not only safer for everyone involved but reduces the stress on the car and its subsystems.

OKINAWA080

Macster - Thanks for taking time to reply with a great lesson.

You must be a teacher of some sort.

I had been on the fence about the UD pulley, not understanding why so many praise the easy mod and yet Porsche engineers made the conscious decision not to use a smaller pulley.

Your explanation has not only helped me better understand the Porsche engineering behind the OEM design choice but has also given me the education I need to conclude that I do not want to install a UD pulley kit. I figure the less I mess with the original engine design, the less it is likely to mess with me (and my wallet).

I bought the car because of the Porsche engineering and not for the available aftermarket modifications that one might impose upon an already excellently engineered automobile.

Now if I raced, or even tracked the car on a regular basis, I would consider increasing performance through some aftermarket modifications or the use of "upgraded" Porsche parts; but, for my almost exclusive street use, I plan to keep the engine components stock Boxster S.

Thanks again!

Respectfully,
Mitchell

GVA-SFO

Hello Okinawa080,

Well, if you run on "high rpm", or let's say, not in "grand Ma style", I would recommend doing the UD pulley.
In my case, I did wait too long, and have leak problem on my power steering. And this is a real mess to fix !
(The M96 engine seems to have this known problem, as the power steering tend to have too much pressure if you "push RPM".)
Clearly it is not good driving to be to high on RPM, (but, ..I do not pretend to be a great driver either !!)
I think being often at good 5 to 6k rpm (on track) is good enough to have "986 steering pump problem".

If you look on my post, (see https://rennlist.com/forums/boxster-...l#post13067853) you will see what it means to "shave" the "bossage". Not a big deal, but not so fun to do. I finally used a small wireless reciprocating saw (a small Milwaukee) to make it.
(Trying with a Dremel goes nowhere !)

Also some good M96 specialists says that having the water pump running a bit slowly should create less water turbulences (on "good rpm" !!) and it could be even a benefit for the cooling !
(Note that I changed my thermostat against a "low temp" one.)

Good luck, and if more questions, ..do not hesitate, just ask !

Ah, forgot to mention, the ISB is not at this end of the engine, it is on the other side, i.e.: where the clutch is !
So, no connection of doing UD pulley before or after changing the ISB. (That one, I did not DIYed it, had a mechanic making it !!)

OKINAWA080

Thanks for all the information sharing.
My reply and UD Pulley decision posted on Rennlist here.
(https://rennlist.com/forums/boxster-...n-okinawa.html)

Macster

The power steering leak is not due to high RPM. Plenty of street only cars have experienced this. It is due to a pressure relief valve faling and directing too high of pressure to the system.

The other problem is the power steering system can run hot. Installing an UD pulley is not the answer. The answer is to either enage in shorter track sessions (the engine, transmission, and brakes will also benefit from this) or install a power steering fluid cooler. At least this addresses the power steering system.

The cooling system is intended to create a high volume flow of coolant through the system.

And some turbulence is desired to bring the cooler water in the center of the flow to the hot surfaces and let the hotter water get away from the hot surface before its temperature rises to the point it turns to steam even under the system's pressure.

Too slow of a flow has the heat load creating steam pockets. The high volume flow forces the coolant past these so they do not become larger and and block further coolant flow.

GVA-SFO

About the M96 engine, I consider that one of the most respected specialist of this engine is Mr. Jack Raby of FlatSix Innovations. (www.flat6innovations.com).
What he has done, created, designed to solve and correct the native design flaw of this engine is pretty impressive.
And :
Jake Raby love the underdrive pulley. Note that he often specify, “the ones with solid center”, as some of these have a “non solid” center (..i.e.: selling arguments to reduce mass) seems to all lead to failure.
See : https://rennlist.com/forums/996-foru...ml#post9869391


This been said, for me, running with an under drive pulley is logical, according to the fact that my Boxster is not a daily car, I do not drive it in the traffic, but I use it mostly on track (i.e.: more than 30% of miles).

So, instead of having a typical use of a car that can face low rpm average, city traffic, low rpm highway cruising, or driven with the goal of trying to get the lowest MPG, as, each of these scenario must have been taking care by design at the factory, my car is facing a kind of “opposite” situation, i.e.: a Sport usage, where the rpm is mostly seating on a much higher rpm average than a “normal” car.
(i.e.: another mod that I strongly recommend in these kind of case now, is the short shifting gear kit !)

So, by these above facts, my ancillary equipment before using an UDP, did run faster than originally “planned”, or designed for. I consider that the UDP kit in my case, ..just put back the ancillary usage into a kind of “normal usage”.

Now, as a side effect, having ancillary running slower, (ancillary equipment takes out a significant amount of the engine horsepower), I do have less horsepower used by the ancillary so, they goes to wheels instead !
Another small side effect, having these ancillary just on the back of the firewall, few centimeters on the back of your back ..and hears, you have less noise in the cockpit.
I should add, that in my case, this is not relevant, as I’m always in “convertible mode", (I removed my roof ! (to gain 18 kg !!)) and the air noise do cover this little noise gain !

Macster

Your comments do not make any sense.

It is illogical to under track conditions in which the engine is being called upon to deliver max power almost constantly, and along with this produce heat in copious amounts, to believe a slower turning water pump is a benefit? You elect to obtain a nominal HP advantage at the cost of reducing vital coolant flow through the hardworking and it follows a hot engine?

Like I said: Illogical.

Certainly fuel efficiency is important. But are we to believe that the factory has overlooked an UDP solution? A factory that has gone to the expense of developing 4-cylinder engines, turbo-charged engines, to help its CAFE numbers going forward and overlooked something as simple as fitting an UDP?

No.

The pulley size is what it is to spin the accessory drives at the proper speed to ensure sufficient circulation of coolant, adequate generation of electrical power, sufficient power steering boost, and A/C compressor operation.

The pulley size need not be any larger in diameter but it shouldn't be made any smaller in diameter either.

Just as I would not seek to spin the water pump slower on a car used for the track I would also not seek to spin the water pump slower on a street driven only car. My observation is street driving can have the coolant temperature quite high even on a mild day. High enough the fans come on which they do at 212F. I have even observed the coolant temperature climbing higher to the point the fans are switched to high speed operation which occurs at 216F.

For my work commute here's a common scenario: On the freeway at speed for some miles, then I encounter traffic congestion and am forced to reduce speed.

Sometimes I have to reduce speed quite a bit . In fact I can go from driving my car at 70mph or thereabouts to zero miles per hour in practically no time and sit stopped along with all the other vehicles until the congestion clears and traffic gets moving again. Sometimes, I can go from driving at 70mph to 0mph and after a delay can be going at 70mph again. (Traffic is crazy here.)

However, in those times when I have to slow from 70mph to a complete stop the engine was working pretty hard right up to the stop and has considerable heat load to shed. But now it must shed it at a suitable rate with the engine at idle and the water pump of course spinning much slower too.

But it does this, has done this, for uncountable times and has suffered not one bit in over 300K miles.

IOWs, there is no scenario, no usage I can think of in which I would choose to reduce the volume of coolant passing through the cooling system of my Boxster engine at any time. Given the dynamics involved it makes no sense and is contrary to what the engine needs.

OKINAWA080

Thank you for your replies.

Both LN and Pelican IMS Bearing Retrofit instructions state that one of the first procedures after draining and checking oil, filter, and sump for debris: Lock the pulley at Top Dead Center (TDC).

The "boss" that one must "shave" down in order to accommodate a smaller (undersized) pulley holds the bolt that goes through the OEM pulley to lock it at TDC.

I brought this up in my initial post so that someone might share their experience of having to lock the engine at TDC at the end opposite of the pulley since it would seemingly no longer be an option with the UD Pulley modification requirements.

Still wondering how much more difficult the Undersized Pulley mod makes an IMSB replacement/retrofit.


Did you have an IMSB replacement before you installed the UD pulley?

Thanks again.

GVA-SFO

I did the IMSB well before doing any other mods in my car.
I did it in a pure “preventive” mode, and this after checking that my oil was exempt of any potential debris, i.e.: removing oil filter, cut it and examine it deeply.

By the way, I did this important check twice, as it was one of my personal exams, ..before buying this car, was this “check”. And did it again, before calling for the install of the new ISB.

About the ISB, as with the series of my engine, it was impossible (info from Jake Raby) to be sure at 100% that I would have a single row OEM ISB, (I had very thin chances that I could have a rare, for this model, OEM double row ISB), we dismounted it before ordering the appropriate new kit.

After serious market analysis, I choice to get (new at that time) the IMS solution called “Single Row Pro”, that is the replacement of the original single row bearing, by a ceramic double row bearing.
And, yes, this was done well before the UDP.

If you expect to buy products (i.e.: ISB kit) from FlatSix Innovations, I would recommend you to contact Jake Raby, he is a VERY nice person, and I'm sure that he will provide you the most valued technical responses about this issue. (He used to be present on this Forum, so, he may chime in !)

Fyi, the kit that I selected is :



Btw, I do not think that the shaving of the TDC bossage in order to be able to install an UDP, makes the TDC bossage not usable anymore. You just have shave it a bit, not to suppress it.

OKINAWA080

From the hours of research I learned that because my 2000 S has an engine year manufacture date of 1998, it has the double row bearing with less than 1% failure rate. Another "Pro" that led to my lengthy decision to purchase the Boxster with 42,000 miles.

When the clutch needs replaced I plan to replace the IMS bearing as well.
Hopefully, by then, I'll have enough experience perform the task efficiently and with some finesse.
Currently, I need to decide upon keeping the stock tail lights or go with the OEM white over red that came a few model years later...

White over red looks more serious and clean but the orange gives it a distinctly European look.

My first car (a '75 VW Super Beetle) had orangish/yellow in the tail light so I think it has made my decision more difficult.

What do you think ...







Actually like both looks... <br/>Which do you prefer and why?




OEM Red over White Tail Light






Stock with Yellow/Orange over Red Tail Light


Thanks again.

GVA-SFO

..You have a left side driving car !!!!

I love your "anonymous" rear hood.

Beautiful car, kudos.

OKINAWA080

Yes, manufactured for Japan but a left sided driver. Thanks for the compliment. No opinion regarding tail lights?

GVA-SFO

It is very personal, almost like a color choice !

I would prefer the white/red solution. (Note that mine is red/orange, with the "white hole" in the middle !)

2RedPorsche

Great looking car Okinawa, love it with those wheels!
I would have expected to prefer the white/red lights but strangely enough I find I like the Orange/red one better. I've often thought I'd like to change mine on my Guards Red 2000 but maybe I'll leave it as is.
It is as GVA-SFO says, a personal preference and I don't think you can go wrong either way.