Bob Prosser

I have a question about evaluating pre-existing boost / fuel / exhaust modifications:

I am looking for a stock or near stock 3.3L Turbo to use as a daily driver (looking for dark exterior/light interior '89 - '92). Eventually, I would upgrade its power in a sensible manner, maintaining both CARB emissions and engine life. However, a majority of the cars I find have already been upgraded, so to widen my available choices, I need to start considering those too.

Of course, every owner says the mods were done "professionally," but I'd like to find a way to determine that for myself. I have seen more than a few low-mileage cars that have had the cases split, now sporting "upgraded cam, larger pistons, etc." This was especially true on eBay a few months ago. Now I wasn’t born yesterday, and I am sure some of these upgrades were more like rebuilds after a holed piston caused by poorly matched bolt-ons, causing a lean condition and pushed too far during hard driving, track days, etc.

It's a little disconcerting when a car is being sold soon after one of these rebuilds. Makes me wonder why and if they cut a few corners to save the financial outlay. With two kids going to college and a wife that wants a second story on our house, I unfortunately don't have the time or extra coin to be constantly working on this car. I need something as close to bullet-proof as possible.

I have past hands-on experience with a 914/6, 3.2 Carrera, 964 Cabriolet, 993 Targa, and for a few months, a 996TT Tip. But I am not a tuning guru -- especially with Turbos. So how can I quantify these modifications? How can I tell if the engine is at-risk? No question I'd commission a PPI including a close inspection of the plugs and compression / leak-down test, but is that enough with a modified Turbo? I assume not since the plugs may be fresh and these tests can only indicate the condition of valve seats, valve guides and piston rings.

- Is there any advantage to asking for a "scoped" exhaust gas analysis? Even though the engine is not under load or on boost?

- Has anyone ever used a Fiberscope to inspect each piston's crown, looking for old damage? Fiberscopes aren't expensive. I can rent one or buy one.

Any advice or techniques would be appreciated. Thanks.

PorschePhD

It is hard to tell what has been done right and what has not. I would suggest asking for a list of the parts and who built the motor. Give them a call and chat with them. You have been doing this long enough to know what key questions to ask and what will throw up a red flag. The second thing I would do is a leak down and a compression test. Also scoping the crown would help a little. Lastly if is has been modified a lot a would request a dyno with a full AFR. This will tell you where the car is.. Once again it is clear what is safe and what isn't. Pull the plugs and check for signs of prior detonation. Small pilling or ***** are a sure sign of running the edge.

Hope some of this helps. It can sometimes be difficult to weed out the bad ones. It can be done though.

Bob Prosser

Stephen, I hoped you would add your dos centavos. Thanks. Okay, so scoping the crown is not an over-the-top request. Good, I hate to look too ****. You mentioned a dyno with full AFR (air fuel ratio) -- that's what I was asking about. Of course, such data is meaningless to me so I'd have to enlist the services of someone like you to make sense of it. Would that data also reveal emission compliance? I am in San Diego and it seems a majority of the low-mile cars are in the East, and unfortunately, many of them have aftermarket exhaust. I need a car that passes California emissions criteria without drama. I know that upgraded turbos and exhaust systems must be matched -- and there's the issue: If I have to put the OE exhaust back on, and the car has a larger turbo and upgraded fuel management, etc, does that throw everything out of balance? I'd assume so.

As for receipts, well, a lot of these cars seem to have an inordinate number of previous owners -- more it seems than NA cars. Some have a clouded past: VIN checks that don't go back year one; or upgrades done by the owner's previous owner, with records missing or; dealers selling nice low-mile cars, then upon research, I find has had a LOT of track time, the mods were pulled-off and the engine/trans is tired.

But that's part of the game. As the Latin-speaking Porsche guys say, "caveat empturbo."

JBH

You are correct...a rebuild on a low mileage engine (<70K miles) is likely due to abuse either from running too lean (that breaks rings or holes a piston) or overrevving the engine (bent valves). I would look for a car that was modified for purpose of achieving higher HP. Rebuild is an automatic red flag.

Intercooler changes and exhaust modifications, while they produce higher HP, are not likely to be modifications that will produce a problem. The 1 bar or higher wastegate spring is where one starts to run into issues of predetonation.

I bought a turbo that was rebuilt after a holed piston. The guy had all the repair records which verified the parts ordered and installed. He also had the car dynoed and produced a healthy 390 rwhp. That convinced me that it was a decent rebuild. Still after owning it several years, several things were discovered that were not done right - not big issues, just poor workmanship or inexperience with rebuilds.

With the header/muffler change, my car would not meet emission specs without leaning out the A/F ratio. What a pain to have to do that every year. Fortunately, I moved to a state w/o inspections. I suppose if I had stayed, I would have fabricated a mod that allowed swapping of a catalyst and bypass.

C2 Turbo

Bob,
If you want to be absolute sure that the car's engine is close to 100% factory spec then your best bet would be to buy a very low mileage car ( as close to 0 miles as possible) making sure that the car was always garaged and it got to be a one owner car.
You just have to look around and be patient and you will find your dream car.However remember one thing that such a car won't be cheap though and if you leave your contact number with dealerships like " Premier Motorsports" they will find you exactly what you are looking for,remember you gotta pay to play This way atleast you won't be worrying about things like fibreoptic scoping,compression/leakdown numbers,what grade fuel did the owner use,how long did he warm up the car before driving off and stuff like that.
These are great cars and you won't be disppointed.Hope it helps.

Bob Prosser

Yasir, I appreciate what you are saying, but don't misunderstand me. Factory spec is not the issue. I don't mind mods, but I hate poor attention to detail, sloppy workmanship or cut corners. And I know these exists -- thanks to my dad, I have been around Ferrari, Aston Martin and Porsche since I was a kid (now in my 40s) and I've seen plenty of rolling hand grenades.

And from my experience, buying a car from a boutique dealer assures me of nothing. In fact, there was a time I worked at one -- Symbolic Motors to be exact. I would much rather talk to the previous owner than a used car salesman, if you get my meaning.

Bottom line: I know I get what I pay for ... I just don't want to pay for what I get.

C2 Turbo

Bob,
If i was you i would rather be looking for a low mileage,one owner car and be done with all the concerns.Now don't forget these cars are 13-14 years old and regardless of how complete a PPI is there could still be things that PPI didn't pick'em up,so for you the simple answer is buy a " One owner,low mileage car,period" and trust me they are out there,just be patient
Btw i think if a compression & a leakdown test comes back good then i don't think you need to worry too much about the condition of the engine.Btw it's very important for you to consider who you buy the car from as that should be able to tell you how he had taken care of the car,if you know what i mean .Good luck

JBH

The advantage of buying a car with mods is the savings on those things that you might do if you were upgrading a stock vehicle. The best anyone can hope for is $0.25 on the dollars invested. If you can find a car that has the right mods done by the right people, it can make a very good purchase.

I suggest shopping for cars with guys that do the mods for a living and never cut corners - those that race successfully: TRG, G&W, Brumos, VP. I would expect each of these organizations to stand firmly behind their work. I suppose buying from from a private individual, that had the mods done by one of these groups might be ok, but you won't get the same support if something goes wrong.

Good luck, let us know how the search goes.

Really? Symbolic Motors did/does shoddy work?

Bob Prosser

Symbolic does fine work in their service shop, which includes Lotus, Ferrari, Rolls, Bentley and probably Lambo. But that is not what I am referring to. What I mean to say is, when it comes to buying a previously owned car, I'd much rather deal directly with the car's owner, so I get a "read" on the person's personality. Can't do that with someone once or twice removed who is on commission.

Steve Weiner-Rennsport Systems

Hi Bob:

Might I add my two bits?

I'd affirm the great advice here from everyone. I'll add that each and every car must be judged on its own merit, given the chronological ages of these cars. Its very tough to find a totally stock, low mileage example.

As Stephen said, the WHO of any modifications is more important than the WHAT,....

There are many people in this business more than willing to sell a Turbo owner anything they ask for (and much more) without a care about the potential consequences. I am always focused on who performed/installed any modifications and the configuration of this suite of upgrades. As you know, many things substantially shorten the lifespan of these things and the end costs can be very substantial (very!).

That said, Jeffery's comments about buying into things that you might do anyway (header/heat exchangers & better turbo come to mind) and its nice to have all those high-ticket items included.

I'd just offer that when I find 1 bar boost springs in these cars, I get PLENTY wary about what I will find. There is no substitute for a very thorough PPI done by competant, honest professionals who are not going to try to sell you service work & parts. Objectivity is VERY hard to come by anymore.

Bob Prosser

Thanks Steve. As usual, your two bits are worth much more than my two cents. Your last bit about 1 bar springs is very interesting. It affirms that there is no free lunch ... or free horsepower. Sooner or later, something has to give, or someone has to pay. I suspect the updated turbo and exhaust reduce the turbo lag more than add power? I plan to put 100,000 miles on the car I get. Loads of extra power is not as important to me as a solid engine that'll go the distance.

Steve Weiner-Rennsport Systems

Hi Bob:

Indeed, there are no free lunches anywhere and that REALLY applies to Turbo's. When I find 1 bar springs, I usually find broken rings (detonation) and worn out valves & guides.

You are SOOO right; someone will pay for the increase in HP sooner or later unless its done correctly & responsibly. Although its not cheap to do, one can get a very reliable 400 HP with all the proper components and sufficient oil cooling capacity.

The exhaust mods make a big difference in boost lag reduction and that makes it feel like it has more HP than it really does,....

For 100K mile durability, a stock (exhaust mods permitted) 930 with effective oil cooling can go the distance as long as it gets exceptional maintenance.

PorschePhD

Bob,
No problem....The answer to the AFR...No the will not tell us anything at idle. Your emissions testing will not be done with this type of metering. They will check the CO though. Something that can be adjusted at a moments notice with the right tool. Consider a Gastesterpro for such an approach. Also keep in mind that the AFR on the dyno will affirm a safe level. I have no issue with a 1 bar spring as long as all things are put into place. This means that there is a enough fuel, big enough intercooler etc. If the car is in a safe range then it is in a safe range. Nothing to worry about. If you click off a run and it shows 13+ you will have a car that is a time bomb.

Keep in mind that the headers alone will not hurt the emissions. They will still allow the factory cat/muffler to be bolted on when needed. The placement of the turbo to intercooler pipe can not be jeopardized and therefore allows you the choice of post turbo component.

Lastly, 100K is doable. Keep in mind that the cars still suffer from all the issues that any 911 does. Like the 3.2 and 993 the guides are an issue. Unadjusted valves beat the stems down. Cars that sit will leak a lot and so on. I can honestly say taking care of a car or getting a good one will allow for many happy miles. One major action will keep the car healthy....drive it!

m42racer

Bob,

I read your requirements and I think they are somewhat unrealistic. Any 930 that is stock and had a recent engine overhaul will be lucky to make 100K without some engine repairs. You should plan on a least some part replacements and an upper end rebuild. How long will it take you to log 100K mileage? This will be a huge factor. If you did that mileage in 3- 5 years you may make it. But if your yearly mileage is less, many of the original parts will fail for sure. You mention some some power upgrades retaining the emissions and engine life. Good luck. There is no such thing. You could add on some power bits, but they will only help with upper RPM power. Anything you want down low that makes any difference on the street will usually fail the smog test. You have to be very careful in CA now. You must pass the visual as well as the tail pipe test. Some places will fail you on the visual if they see an aftermarket set of pipes. I know from experience, that the State knows the cars that are typically hotrodded. Porsche 930's are on that list. I have my current car's original engine. Everything been done to the car presently is been done so that it can be refitted for the test. Those that live in CA really have the hardest time with smog testing. It is not uncommon to see roadside testing now.

As for the advise told so far, everything should be considered. It all has been very good. The only thing I can add is expect to rebuild. If you don't have to, then you beat the odds. These cars are very costly to run and maintain. Aircooled engines by design are expensive. As for checking the engine, do as the others have said. The leakdown, (hot) and a compression check will give some indication of the condition of the upper end. The oil if not new will show any signs of bearing material, but really nothing really can be seen that would indicate a failing BTM end. Oil pressure at normal running temps is an indication, but most often this will not show a problem unless it is very bad. Look for leaks. Older engines tend to leak as the seals and gaskets start to get hard. All very normal.

You ask about who did the upgrades and what they may be. This can help to some degree, but it really doesn't matter much. Even the best of them have their horror stories. Most of the upgrades offered are all catalog upgrades, where the same parts are repeatly sold and installed by many different tuners. Who did them really doesn't have any bearing on what you end up with. Most engines are assembled not built. A good indication of quality is how much of the work do they do themselves. Do they do their own machine work in house. If they do, its normally so they can control the quality. Not always, but thats the typical reason its done in house. Remember, every good engine starts with good machining. I have seen the difference first hand. The first 930 I had required the Heads to be rebuilt. The shop I was using sent them to a well known Sth CA Porsche machine shop. The engine was reassembled and many thousand dollars later, I was back on the road. The engine seemed to make better power, but it did not really seem that much better considering the leakdown numbers before. 3 were over 50% and the others were all over 20%. I sold the car but not because of this. It was when I upgraded the red 930 that I was to understand the difference between production machine work and precision. This engine had had the heads rebuilt at some. When the Valve seats were machined, they were machined lower than the Combustion chambers and the chamber was machined to give some sort of a match. I was shown just how much this effects the heads ability to flow. The flow was some 30 CFM down on what it should have been. Multiply that by 12 seats and you get to see just how much performance you lose. I'm told this is very common with many of the production machine shops. When the heads are shipped off to these places and come back assembled, your mechanic probably never see's this. He also would not know the differnce. I have been told by many in the past, "I've been doing it like this for years and never had a problem". How many reapir shops have Flow benches and can tell the difference. Doing seat work on hemi chambers is some of the hardest seat work there is. As soon as the seat is remachined, the Top angle must be changed to accept the lower position, or what normally done, the chamber is cut to give some bevel to the top angle. This new angle is very critical for flow. You may be worried about the Bearings. Most places don't even measure the clearances. They look at the ones coming out, and if they look like there is wear on them, off goes the case to the same machine shop for repair. Did the mechanic remeasure the Line bore upon getting it back. I would bet not. Even the dealer will shortcut the work. All the mechanics are flat rated, so your work is done as quickly as possible. There is way more to it than I have stated here, but I hope I have given you some small insight into what typically goes on. So who did any work is not really a factor. All you can hope for is the best.

Whats my point. Buy carefully with all of the advice already given, make a deal only if the car will pass the emissions test, and expect to do some engine repairs. At that time, be as wise with who does these repairs, including any machine work as you are with what car you buy now.

Bob Prosser

M42, thanks for the pragmatic advice. You mention 930s. I mentioned I am looking for a '89-'92, but I assume there is very little difference between these 3.3s, plus the advice is basically universal.

How quickly to reach 100K you ask? I drive about 15K a year, so yes, my next car will get plenty of regular use. Am I asking too much? Maybe I should be thinking of a NA car.

There was a time when I would replace parts for bi-annual emissions testing, but nowadays, I just want it to work. I have too much else to do.

From what I am reading, it seems that Turbos aren't quite as, um for the lack of a better word, reliable, as their NA counterparts. Turbos are engineered for the extra juice, so why not? More heat and the more hard driving nature of the owner?

Anyway, thanks all for the helpful advice.