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Discussion Starter · #1 ·
Just picked up a 900 Turbo and am thinking about a little mroe power, bnot insane amounts but a little mroe than stock. I thought about an 85 or newer intercooler. Also i plan on doing the typical, better flowing exhaust, better intake ( i am a magician at fabbing up true cool air intakes) and MSD ignition. But where boost comes into play, im new, i know little about turbos but not enough to dive in head first. What can i do for boost? Being mech FI are DV or BOV out of the question? What upout wastegates? any performance there? I would like to swap to a 16V turbo engine but for now i jsut want a little more pep. Any ideas?\

Thanks,
Patrick
 

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I believe you can upgrade your APC. Im not totally sure on that, so Delorean, Rhich or Burnsside can probably give you more info.
 

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Unless your current equipment is damaged, you won't see any performance increase from BOV/BPV/DV (all the same thing pretty much) upgrades or wastegate upgrades.

The most common power increase for c900's is a tweaked APC box. The APC is the ECU that controls the wastegate solenoid, and thus the boost levels. It's free and is definitely a big jump in power. Although I'm only familiar with doing that on 16v engines - I've never tweaked an 8v turbo.
 

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The main limiting factor in your 8 valve motor is the Bosch K-Jet Fuel distributor, It's ancient technology that saab stopped using in 1984 on turbo models. Sure, VW kept using it till the mid 90's on their cheaper cars, but there is a good reason saab did away with it. The fuel metering is controlled by a air-flap. As more air goes past the flap into the engine, the flap opens more and adds more fuel to the injectors. The main problem here is once the flap is open 100% (this happens around 12-13 PSI) the engine will start to lean out and cause extremely high combustion chamber temps. This can lead to a melted engine. This is not to say you can't tweak the car, you can. Stock I doubt you are pushing 8 PSI. There are APC tweaks that you can find here for your 8 valve APC -- www.900aero.com and other stuff as well. before you tweak anything, I highly suggest you make sure the engine is in top running shape. One thing about the 8V-T's is the injectors sometimes like to clog with carbon and sludge, then melt a single piston. this is a major problem on VW's as well up till about 1995... Be sure they are all clean and firing properly. check everything ignition related. make sure it's in top shape. After you KNOW the engine is in good running shape, get an AFR gauge that you can tie into your oxygen sensor (to make sure you are not leaning out) and a boost gauge. these are some things every car with K-jet car should have... After you are all set in that respect, you can start tweaking your APC to get more power. Now, if you start to lean out under full boost at that point there are upgrades you can do for the fuel distributor. we can discuss that when you are at that point.
 

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DeLorean said:
VW kept using it till the mid 90's on their cheaper cars,
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this is a major problem on VW's as well up till about 1995....
The Fox was the last VW to use CIS in the states, and it last used it in MY1990. Other models had ceased using it after MY1989, replacing it with either Bosch Motronic or VW's proprietary Digifant injection systems.

CIS is indeed ainchient tech, but it's one of my personal favorite fueling systems - at least from a nerdy point of view. It's practically a mechanical computer, running off pressures instead of electrical voltages.

Plus, sooooo many cars from different manufacturers used it for so long, it's easy to tune by swapping in OEM parts from other marques.
 

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This is compleetly off topic, but

The Fox was the last VW to use CIS in the states, and it last used it in MY1990. Other models had ceased using it after MY1989, replacing it with either Bosch Motronic or VW's proprietary Digifant injection systems.
Check your dates on that. I know that there was a VW model running that system till 1995, but I forget which one. Just off hand, I know for FACT that the VW A2 16 valve MkII up to 1992 had CIS, so no, the fox was NOT the last VW to use K-jet injection.
 

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DeLorean said:
Check your dates on that. I know that there was a VW model running that system till 1995, but I forget which one. Just off hand, I know for FACT that the VW A2 16 valve MkII up to 1992 had CIS, so no, the fox was NOT the last VW to use K-jet injection.
We're both wrong. :!: The 16v Passat was the last, in 1993. The B4 Passat (1994+) didn't have a 16v engine available, and both the ABA and Vr6 were Motronic.

MkII ended in 1992, so it couldn't have been the model that had it in 1995.

The only VW's availabe in the US that weren't Passats or A platform (Jetta, Golf, Cabrio) were Vans and Foxes - Foxes switched after 1990, and Vanagons stopped production in 1992. Eurovans were 5 cylinder motronic engines in the mid 90's.

All A platform N/A 8v models switched after 1989 as I stated above. Honestly, I'd forgotten about 16v when I made that post!
 

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Discussion Starter · #9 ·
thanks for the info. I dont plan on doing anyhting yet till i do tune up and replace worn parts first. How do i go about tweaking the APC. Sweadish performance has a "Red Top" APC but for $300(i think) i could probably get a 16V and rebuild it myself. One thing i do love about the CIS systems is that they are very very reliable. I owned an 87 VW Quatum GL5 2.2L 5 cyl with 278k miles on it and ran top notch. Never had a problem with the engine, the suspension on the other hand, was a different story, Rear shock and trailing arm broke. but yeah, thanks for the info, and thanks ahead of time because i know im going ot be visiting this board alot. I can seriuosly say im hooked to Saabs now.
 

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Turkey, don't buy an APC box. You can create nearly the same result by popping it open and fiddling with it yourself and pocket the cash.

And DeLorean - I'm sorry I got us off topic. But I was taken aback by your comments towards VW, which made it seem like they were all plagued by CIS until the mid 90's, when in fact most of the models had done away with it years before that. It would be like me saying Saabs sucked until the mid 90's because of 8v engines. ;)

Turkey - was your Quantum a Syncro? Those are incredibly hard to find suspension parts for! And ya know, there are a whole variety of very powerful inline 5's from Audi that'll drop right in to that chassis - it could be quite the sleeper!
 

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Discussion Starter · #11 ·
no it wasnt a synchro, i wish it was though, i would have kept it then. did know that any audi/VW engines would bolt in. will have to keep that in mind. I figure im going to do the exhaust first 'cause this morning, the thing fell off. The previous over had nex exhaust from the cat back, but i did notice it was factory and that the hump that goes over the rear axle was kinked from the suspension hitting it. well the part where it connects to the cat broke off. either from to much back pressure and rust, or improperly hung, but whatever it was i have a nice clean break right after the cat so im going to replace the down pipe and the rest of the exhaust. I was thinking about a custom side exit in front of the rear tire, and think about making a custom tube header with made 2 inch primarys, think it would flow too much? cause some turbo problems?
 

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Off topic again...

And DeLorean - I'm sorry I got us off topic. But I was taken aback by your comments towards VW, which made it seem like they were all plagued by CIS until the mid 90's, when in fact most of the models had done away with it years before that. It would be like me saying Saabs sucked until the mid 90's because of 8v engines.
My POINT to that was that VW was using K-jet injection for several years after saab quit using it. The last saabs to come with CIS was the base model 1988 saab 900, and they probably sold about 50 of those :roll: last turbo model that had it was the 1984 900 turbo. WW used this system for many years after saab quit using it, and that was my point. I guess it's a good thing though, cause the fuel distributor in the early 90's Passats are easy as cake to find in the junk yards, and they make a fantastic upgrade for my 1978 saab 99.

Back on topic,

Check the site I posted, look over it. I can't post a direct link to the article because of the lay out of the site, but you can find info on how to mod your 8 valve's APC right there, and it's not even very hard to do. If you start really boosting high though, you are probably going to get lean out and are going to need to swap fuel distributors. Like I said, come back if you get to that point, and I can recommend some cars to look out for in the junk yards that you can find a better fuel distributor in.
 

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DeLorean, ever use Volvo fuel distributors? I know VW people that have upgraded to those from the one you're talking about. I think people take the dist off a v6 and use it on an i4 with 2 of the ports blocked off.
 

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I have personally not looked too far into it, but from what I understand there are a large variety of things you can do with the fuel distributors from different makes and models all the way up to adding a 5th injector that's boost activated. I am not going to take it this far with my 99, so I am probably not the one to talk to about this subject. I know what others have done with their saab fuel distributors to get past 18 PSI, but I have little first hand experiance once you are really pumping out power using K-jet. John W from saab central has an 8 valve K-ket 900 that's pushing 230HP, so he's obviously the one to talk to about fuel distributors. I doubt I am going to push my 99 much past the stock fuel distributors maximum limits, but I already have the upgraded unit for that (along with a 1980 saab 900 EMS cam) so if I want to up the boost, the car and the fueling system could take it in *in theory* ;)
 

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DeLorean said:
all the way up to adding a 5th injector that's boost activated.
That's one of the cooler OEM "upgrades" I've seen.

There's definitely a dizzying array of possible configurations. Ever heard of the "super rare" gold injectors? :D

The two turbo CIS VW's I'm most familiar with are both running aftermarket injection so I've also got limited firsthand knowledge.
 

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Discussion Starter · #18 ·
i think that the 8v already has a 5th injector but it isnt boost activated, it is throttle activated with a micro switch by the throttle cable cam. I thought i read about it in the shop manual. I know my VW had it.
 

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NightTurkey said:
i think that the 8v already has a 5th injector but it isnt boost activated, it is throttle activated with a micro switch by the throttle cable cam. I thought i read about it in the shop manual. I know my VW had it.
All the 5-cylinder VAG motors have a fifth injector. . . on the fifth cylinder! bah-dum-dum ching :lol:

Those 5-cylinders came in up to 300 hp configuration from the factory. Pretty stout motors. MC2's from the later 10vt Audi's are cheap in junkyards and make well over 200 hp with about $65 in mods.
 

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Discussion Starter · #20 ·
ok ok by bad, for the 5 cyl i meant had a 6th injector, and the 8v 2.0 has a 5th injector. the differnce is that the 5 cyl had a real switch activated injector AND a cold start valve, the 8v 2.0 only has the cold start valve (5th injector) but can be modded to open on command. sorry for the miss information
 
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