Garth S

Just catching up on this cool mod ...
The S4 water pump has the same dimensions as the 16v pump IIRC, for the impeller pulley, cam gears, crank and oil pump must remain in the same plane - what did happen is that the S4 tensioner moved out ~8mm to place its centerline into that plane ( and minimize the twist imposed on the carrier arm pivot by the TB). That move required a little bulge in the S4 center cover ....

SharkSkin

No air pump = not an option for me. Interesting project, though...

BC

Newer cats create enough heat to not need the air pump. Is there another reason you can't use the air pump? SOme S4 fans would really clean things up. Or aftermarket fans.

PorKen

The air pump bracket is a bolt-on accessory, jeez.

Looking objectively - even if I didn't make the system - I'd say that is one of the most significant upgrades for the 928 engine, period! The other would be a working crankcase oil management system.

I'm a pretty calm guy, but I'm just bursting at the seams about this. Imagine never having to worry (as much) about belt tension again!

... phew, one too many espresso shots today!

Post 2,666!

F451

Ken,

I am with you on that. This sounds awesome. Please keeping us posted on your progress. I want one ('85 928S - 32v - btw). I'll will have to sneak the purchase into the family budget somehow, but this one sounds like a no - brainer.

I have been quietly freaking out about this interference motor with its 7' long timing belt - even before I bought one, so it sure would be nice to know the belt is being automatically tensioned while I'm bombing around in it.

And it doesn't mean I wouldn't check the tension on it now and then, but I think it will provide a much higher level of reliability to the motor vs the stock setup.

Keep on keeping on Ken.

Ed

Andrew Schauer

to Ken, for this and all his other useful inventions.

SharkSkin

Sorry to leave such a terse response, I was in a hurry. AFAIK I will always have to bring my car to a test-only station, and while I've found a guy that's a bit flexible, I don't know how long he's going to be around. California seems to be insisting that all 928s fit the gross polluter profile -- It seems that everyone I talk to who's due for smog has to go to a test-only station. They cannot always be reasoned with, so my thinking is that it will be a lot easier to just keep the smog equipment working. I don't need a cat, or I would get one of the high-flow units that doesn't need the air pump -- but IIRC part of the reason that the air injection goes to the head/exhaust ports is to keep them somewhat cool. All in all, with the limited free time I have, especially this month, my initial reaction to re-engineering systems that work perfectly OK is that it's not worth the trouble. I'll lighten up once I get this move under my belt and get my workshop rebuilt, and get caught up on my backlog of 928(and other) projects.

I in no way meant to disparage your efforts, Ken! The variable timing setup is definitely a more interesting project, especially if you don't live in the land of the smog *****.

PorKen

Actually, it makes it hotter, as unburned gas is afterburned in the exhaust port. I don't know about the 78-79's, but I've heard euros have stainless steel inserts to protect the heads.

The stock tensioner works, mostly, but I consider it an afterthought by the engineers. Too many places it can go bad. Shoulder bolt, plastic bushings, pulley bearing, low to no dampening, and inflexible tensioning.

SharkSkin

Interesting... sounds like I may have been misinformed on that....

No argument from me on the failings of the tensioner design -- What I was getting at is, I'm not about to screw with a perfectly good cat at this point, or mess with an air injection system that not only works just fine, but keeps smog checks from being a hassle. Whenever it comes time to replace the cat I will get a higher-flow modern cat. If/when things change and I no longer have people snooping under my hood the EGR will go and I will be shopping for headers that don't prevent clutch access. And so on....

BC

first, there are no headers for early cars that make it easy - since, you know, only one guys makes them, MSDS, and they are cheap (450 uncoated directly from him).

Secondly, CA now has simply said that the date of smog is NOT rolling - its static:

Beginning April 1, 2005, the 30-year rolling exemption will be repealed. Instead, vehicles 1975 model-year and older will be exempt. Therefore, 1976 model-year and newer vehicles will continue to be subject to biennial inspection indefinitely.

So unless Porsche has some prototypes from 1975 that I we can get Vins from, then we will ALWAYS have the 78s under the smog check.

I think a good relationship with the smog test-only station is required these days.

PorKen

Dave,

Maybe you were thinking of EGR, which does cool the combustion temps.
...

Looks like I won't need a bracket for the PKVVTS (PorKen Variable Valve Timing System); had one in my basement.



Instead of flat bar, I'm going to use pipe, with an arm off it, for leverage. I'm thinking I'll use a bicycle shifter, or a choke cable, to set the retard<->advance, until I can think of an automatic system...

(PKVVTS thread)

dr bob

Going to vary both the intake and exhaust timing together? Memory is that the 968 system does only the intakes.

I wonder if the load/RPM signalused to move the flappy on the S4+ cars would be close to right for a transfer of valve timing? Maybe get rid of that annoying power drop-off that signals the impending rev-limiter action?

SharkSkin

Brendan, I'm aware of those issues, but a number of things may happen to change the situation:

1) We may go back to rolling exemptions -- Arnie's out soon and it's possible that changes will be made in this area.
2) The rules for classic/historical registration may change -- Right now the mileage constraints don't fit with the way I use the shark. If I could register this way without the 5K mi/yr limitation I'd consider it.
3) In the next few years I may be moving to a zipcode that is exempt

I do have a good relationship with the test-only guy nearby. Last time, he only looked under the hood long enough to get the inductor on the coil wire. Hopefully he sticks around for years to come; all the other test-only shops around here seem to be suffering from an epidemic of cranial rectalits.

Regarding the headers, I would either modify the MSDS (think removable collectors like the headers Mark A had made recently) or settle for manifolds off of a later car.

Meanwhile, this car is a daily driver and while I may eventually find myself removing a blower every 2 years, I don't want to have to add exhaust manifolds etc. to the mix. If I have a blower I probably won't be too worried about the incremental gains from significant exhaust mods. None of this is even half-baked yet, I'm just trying to avoid causing myself grief down the road.

Ken, I know EGR cools cylinder temps, I can't remember where I read that the air inj. cools the exhaust ports -- only that it was somewhere on Rennlist. Regardless, IMHO it's in my best interests at the moment to keep all of the emissions systems working.

Bob, if you can think of a way to independently vary intake & exhaust timing on the 16V cars I'm sure lots of folks will be interested.

BC

I do hope we return to rolling emmissions, but I am not hopefull because of whom is on either side of 1975

H2

I have a 968 with that type of belt tensioner and it's great. I would love to have something like this on my 928.

Note: It's my hard learned opinion that the GREAT Kempf tension gauge reads a bit higher in the "window" for 32V cars than 16 valve cars. For serious belt tension work, you must use the P9201 gauge. Perhaps you do but I saw the Kempf gauge mentioned.

I recommend Both Kempf and Porsche 9201 guages where possible, particularly for serious work. That said, I can't live without my Kempf gauge. It's really quick and easy to use and I use it first to set tension, then double check with the P9201 (which is a PITA to use, BTW). If I only had one gauge, I'd use the P9201...but have it calibrated to the proper setting using someone's P9201. On my Kempf gauge (I've had two because I questioned the setting on the first one) I used a file to permantly mark the gauge setting for my car. It's about 1/16" of an inch above the window notch. Great tool.

The good thing about PorKen's new idea for a tensioner is that you'd not need to use a ension gauge very often since it's auto tensioning to the right tension all the time, year in and year out, until the tensioner wears out. Great development. Don't know why Porsche didn't use this on the 928 since they had the autotensioner on the 968 in 1992 and the S2 also (I think). Cost savings to not retool to the better system I guess.

Harvey