Well, the beastie runs & drives. After building one good engine out of two bad ones and more than a little creative merging of newer parts in an older car, the '78 99 Turbo I've been working on is driveable.
So, the inevitable questions. Where is the overboost sensor on this thing? It seems to be cutting out the ignition just as I get into the "red" on the turbo gauge, rather than up a ways as I would expect. Where is that beastie, and/or might it be something else like a stuck turbo bypass valve?
I still don't have a working alternator for it; can I use one from, say, a 96 or Sonett? Those, I have. Otherwise, can I use a later Saab 900 alternator, and which should I choose?
You could use a 95/96/97 alternator but those used in the US only go up to
35 Amp. Only from 1976 or so did they get a 55 Amp one. Both have an external voltage regulator. You'd be better off using a 99/900: 55, 65 or 70 Amp and a voltage regulator integrated in the brush holder. If you do not have many electrical accesories on at the same time (AC, heated seat, heated rear window, fog lights, spot lights...) 55 Amp is more than sufficient. Also, the 96 one rotates the other way round as a 99/900, so you also have to swap the cooling fan. One more difference is the double pulley on (some?)
900 alternators (like my 900T).
I installed a 900T engine in my 78 99 some years ago, but didn't get any such luxury as overboost protection -- still I did experience the symptom as you describe, I think it was the warm-up regulator that was stuck, leaving too little fuel at high loads.
If you haven't already, try to increase the fuel/air ratio by turning the adjustment screw 1/4 turn clockwise at a time and see what happens. Also check the so-called "control-pressure". If it is too high, as I said, the engine will run lean at high loads. more than 4 bar is too much. The Haynes manual for the 99 is quite informative on this part. When cold, it is approx. 1 bar, increasing steadily to around 4 when fully warm.
PS: Until you get the fuel mix mostly correct, you may find it convenient to use a set of "hotter" NGK-s than specified, I think I still use BCP6's, but then in Norway, continuous operation at highway speeds in hot summer days is soo rare!
Right, looks like I'll fix up one of the two bad ones with the car then. There's a Motorola that doesn't turn (but I'm comfortable rebuilding motors so this shouldn't be bad), and the other one which is I think the Bosch that seems to be missing parts - has the 3-blade connector on the back of it that looks like where a voltage regulator should go. Or, can I put a VR from a 96 onto those, with the right cable?
Let's see. 99 Turbo - manual windows, no AC, not sure about rear window defogger (I think yes), heated seat of course, no fog lights or spotlights. So 55 should be reasonable if that older Bosch just needs a VR.
Good to know. Surprising though, since both are at the 'front' of the engine?!?!?
About the Sonett ring & pinion set we were talking about, I looked in the other place I could think of for that ring&pinion, it's not there. The only other one I might have is still in the intact parts sonett, and it won't be coming out of there any time soon I'm afraid. I'll keep an eye out for them, but I wouldn't hold my breath.
It's a _very_ abrupt cutoff; maybe I'm just hitting the rev limiter. Need to try again tonight and see what RPM it's happening at; I was watching the boost gage rather than the tach.
Which adjustment screw, please? This is a CIS fuel injected system, does that change what you're saying?
Sounds like I need a Haynes for the 99T then. My 900 manuals are good for almost everything, but they're too new for some stuff, and my 99 manual is too old for the turbo stuff. Ah well.
I put BCP6s in there, which I think is as hot as I should go, yes?
The 99 fuel cutoff is really just the fuel-pump being switced off. I don't know how that feels since I don't have that feature, but I would think not quite as abrupt as total ignition misfire. The rev limiter is supposed to cut in at 6000 rpm and as far as I can tell from design, it will stay out until the rpms have dropped substatially. 6000 rpm is way beyond where I shift up and I have never experienced that. It is a simple spring-loaded centrifugal device in the distributor, quite easy to disable just for the sake of ruling out that possibility. It could be that the spring is getting old. Your original post indicates that it is boost related, not RPM.
It is the green one here displayed at this page:
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allen screw, buried deep inside the unit betwen the airflow meter and thefuel regulator. It is accessible from the top. You'd really need a toollike this:
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I have always used a long electronics-type screwdriver. Just remember to keep a record on how much you turn it. 1/4 of a turn is maximum between test drives. Also keep an eye on the spark plug deposits in the long run.
I'm sure the web is full of info on CIS / K-jetronic, it was/is used in every kind of vehicles from the Golf to the 911 turbo and Lamborghini Countach, Ferrari Mondial And that V- thing too...
No big deal, I can take some photos of selected pages, and cite some key figures if needed.
Yes, that should work, The 96 has a short (+/- 20 cm - 8") triple cable for that, also with a cable connection to the charge light spliced in - that HAS to be connected for the alt to work ok!
yes, but the front of a 99/900 engine is facing the rear...
This is the inductive sensor distributor, yes? I'm not actually sure if this is the right dizzy for the car, it was just the only 99/900 dizzy I could find with the right gear cog on it (course teeth rather than fine, to mesh with the older-style countershaft in the engine). I should look at numbers, and/or try another dizzy I think.
I thought it was just as it crossed over into the red boost, but it may have been also when I hit 6K RPM. I'll check tonight rather than second and third-guess my second-guessing.
Excellent. I've got pretty much that exact tool from my days as a biomedical electronics technician.
It's a delightfully elegantly simple solution. I'd love to refit one to a V4 Saab.
I am likely to take you up on that at some point. Right now things seem good aside from the above. I got a new cap for the expansion tank today, because the other one was very scary looking, so hopefully I can bring the system up to normal temperature and pressure to check for leaks. The oil system seems intact, and the turbo sounds good. Still haven't heard the bypass valve noise I remember, so I'm not sure what that's all about yet.
It's been a dozen years since I drove (a/this) 99 Turbo, until yesterday. The steering is a bit heavy, but it's a _very_ fast/responsive rack. Handles good, even on not so good tires. I plan to put on more than 3 miles tonight, but since it hasn't moved on it's own power in more than a decade, I'm going gently and cautiously.
...and it seems to have the VR built into it, would that be the best bet then do you think? I'm not intimidated at all by rebuilding it if it's worth using.
The annoying thing is, I know they're in the barn, but can't put my hands on 'em, as they're not on the shelf I'd expect.
Thats the one. In my car (taken from a 1980 or 1981 900 I think), the purely mechanical RPM limiter is built into the high voltage (secondary) circuit only and does not involve the low voltage parts at all.
As you may have noticed, the 99T has a quite unusual boost control system that actually senses and controls the exhaust manifold pressure via a rubber diaphragm regulator. At high RPM's, (max BHP is at 5000 remember), I would expect that the added back pressure from the exhaust system will keep the needle away from the red area. If the rubber diaphragm is in good order and the wastegate valve isn't stuck, that is;-)
I dont have a tachometer and only a self made digital boost pressure gauge, but my impression is that the torque while quite impressive at around 3000 rpm it rolls off quickly to just above adequate when I feel like it is time to shift up. This is quite good for the limited cooling capacity of the 99 and quite contrary to the 2.3i I must drive when I need AC;-)
And double-checking that the wastegate is operational before you go all the way could be a good idea. I am on my second tranny and third head! A bicycle-pump will help you in revealing any leaks and perhaps you can hear the shaft moving as well.
Volvo used a fuel pump overboost cutoff, at least on the 240 and 740 Turbo models. I've hit it before and it's very abrupt and unhealthy sounding as you describe this one. The boost was set too high after replacing a turbo, floored it and WHOOOSH *BANG* WHOOOSH *BANG* it's really amazing how quickly boost can build up, it's *very* difficult to regulate it with the accelerator pedal.
Must sound interresting, Should give you more high-end boost than most 99's, but I don't think that is the source of your problem.
Locate the tube going from the exhaust manifold near where the tranny dipstick is located to the aluminium top cover of the regulator housing. Disconnect it at the top cover, careful with the threads at the manifold side, they are likely to be rusted and brittle.
Now you can verify that the diaphragm is intact by gently applying compressed air onto the housing. There should not be significant leaks, as that would flood the regulator with hot exhaust all the time, no doubt with harmful results, I am not sure how much pressure is needed to crack open the valve, especially not one that has been sitting for a decade, so if say a moderate 10-15 psi is insufficient I would rather remove the four 4mm (5mm? (no 4!)) nuts and the lid, thus gaining mechanical access to the end of the valve shaft. Don't rotate it as that would destroy the expensive rubber-diaphragm instantly! Check that it can be pushed in and that it comes out again by itself.
BTW, the big, locked nut at the end of the shaft is of course the place to adjust the boost. Increased spring pretension results in more boost. You may want to go the other way at first. That will exersize the wastegate system a bit extra too.
Right, I see them (in my photos; I'm not near the car right now).
Ah, so this is how it measures the boost pressure, through that line. Pushes down on the diaphragm to open the bypass valve, yes? An elegant solution.
That's what I'm thinking. From the diagrams from my 79-80 c900 manuals, which should be the same enough for these purposes (yes?), it looks like, well, a valve valve. Could be stuck to the seat, could be stuck along the stem. Probably want to take the top off as you mention just to check that, being that head gaskets aren't cheap and all.
Will do. I have at least 3 spares, but I'd rather not start breaking things anyway.
So if I turn down the boost until I get a feel for everything, that'll make it travel more and un-sticky itself, in thory at least. Sounds reasonable.
Not very precise, but less prone to oscillations. I'm sure the fact that the valve opens in the upstream direction most likely contribute to the
99-engine's reputation for "ketchup-effect".
Some info from Heynes no. 247, p 246
------------------------------------------------- PSI Bar Turns in/out to obtain correct
12.5 .86 1 out
11.9 .82 3/4 out
11.3 .78 1/2 out
10.7 .74 1/4 out
10.15 .7 0 (Correct value)
9.6 5 .66 1/4 in
9.0 .62 1/2 in
8.4 .58 3/4 in
7.8 .54 1 in
-------------------------------------------------
Another thing just came to my mind: Back in the days when this was my only car, I reduced the pressure to .5 bar or so, since I ran out of spare heads. This resulted in an annoying noise that I chased for a year before I realized it was the wastegate valve hammering the seat almost from idle. Had a minor crack in the exhaust manifold removed and welded without any effect amongst other things!
I'll probably set the base boost (wups, boost I mean) to normal spec and leave it there. It should be zippy enough as it, I should think. What is the output of this engine, 160 Horsepower or so, right?
US model: 135 bhp @ 5500, 216 Nm @ 3500 rpm @ 0.5 bar, cat. yes? UK 145 bhp @ 5000, 235 Nm @ 3000 rpm @ 0.7 bar, no cat.
Compression ratio: 7.2:1 !
Note! Pressure switch actuating pressure: US0.7 bar, UK 0.9 bar.
FYI, I operate it at 0.8-0.9, unleaded 95 octane since mid-80's, no problems except wheelspin in rain when careless (short wheelbase). Rust is my main problem, so...
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