[jeremyfrost]

On a NA engine, conventional tuning wisdom suggests that you head port & change cams. I know that Abbott sell a big valve head, but what of cams on Saabs? I am led to believe that cams will add torque and 10bhp on my 1.8K Series engine. Will it do the same on a turbocharged 9000?

 

[aeropilot]

Radical cam changes are not usually associated with turbo tuning, and Maptun don't offer a cam change until opting for their monster 440hp Stage 6 conversion......

 

[Eric van Spelde]

That's just because it's so easy to whack up the boost and forget about the rest of the driveline

. Looking at the power graphs of most modified turbo cars, especially those running stock hardware, the hp gains in the midrange are much bigger than at the top end.
IMO beyond a certain amount of midrange torque, any more (and any more brutally produced) will only lead to virtually uncontrollable wheelspin, torque steer and broken gearboxes. Extending the torque curve further up the rev range also gives you more revs to play with at the track, so you can avoid upshifts where they would interrupt proceedings.

According to Dr. from the TSN board (Trionic developer at Saab) the standard Saab cams are all quite mild. There's definitely scope for improvement here.

 

[Damo9K]

Agree with Eric + If you go for longer duration / high lift cams you ARE looking at pushing the torque/power curve much further up the rev range. The problem being you then really need a billit lightened crank and so on to get the engine revving more. Plus you need to adapt the turbo and management system so that everything is coming on song at the same time, else you get a real mess ie big turbo cossy

Damo

 

[Eric van Spelde]

Depends on how far you want/need to go. The Saab EV-1 concept car of 1985 (which was entirely based on c900 running gear) peaked at 285 hp @ 6,500 rpm, where the T16 normally reaches peak power at 5,300. That 1,200 rpm difference alone makes for 20+ % more power at the same torque level (Peak torque on the EV-1 came at 3,500 rpm and was an entirely reasonable 246 lb/ft or 334 Nm - even the 1985 Saab 900 5-speed installed would have a fighting chance to survive at that level!).
Apart from strenghtened rods, bigger intake ports, and low compression pistons, the engine consisted out of stock parts. Crankshaft, camshafts, valves, valve springs and the castings were all factory standard.

The hydraulic valve lifters in a Saab 16v engine are good up to 7,200 rpm. At that level, balancing the rotating assembly and shot peening the con rods as well as the crank are all that's needed to cope. Billet cranks will only be needed when aiming for 400+ hp, and at about 600 the cylinder head bolts will have to run all through the block as per Per Eklund's car...

The turbo is rated for a certain efficiency (about 70% is generally accepted to be within limits, the rest is being converted into heat) at a certain amount of airflow (say 20-40 cfm) which corrsponds to an attainable hp level within a defined efficiency range. Whether this airflow (for a given capacity and volumetric efficiency of the engine) will be reached by a combination of low rpm and high boost, or the other way round, it doesn't care. It will still provide the same efficiency at the same power output.

 

[Damo9K]

I sort of disagree with you Eric on some of those points

Yes it does depend on how far you want to go, but you only really have two choices: go to a very mild upgrade on the cam with very little benefit (maybe a bit better midrange power) or you go fairly wild and end up with a race spec engine that is a nightmare to drive off cam.

Apart from strenghtened rods, bigger intake ports, and low compression pistons, the engine consisted out of stock parts. Crankshaft, camshafts, valves, valve springs and the castings were all factory standard.[/b]

Yeah but that's not really a std engine, low compression pistons alone sugest's higher boost levels required to attain those power figures.

The turbo is rated for a certain efficiency (about 70% is generally accepted to be within limits, the rest is being converted into heat) at a certain amount of airflow (say 20-40 cfm) which corrsponds to an attainable hp level within a defined efficiency range. Whether this airflow (for a given capacity and volumetric efficiency of the engine) will be reached by a combination of low rpm and high boost, or the other way round, it doesn't care. It will still provide the same efficiency at the same power output.  [/b]

I understand the theory but apart from my hybrid TD04 Mitsi Turbo most other turbo's ie std TD04's and T2's fitted to 9k's that ive driven start to struggle at the higher engine rpm and tail off, so there is very little point changing the engine characteristics with cams if the turbo isn't up to the job - hence my orriginal point that you will only really benefit if you get a bigger,higher A/R Turbo to match, and at that point you will then need the management remapped or your going to bu66er something with a lean mixture.

I think the point is unless you want to go fairly mad, it just isn't worth messing with cams on a turbo car that's designed to have a low to middle power band.

Damian

 

[Eric van Spelde]

I understand the theory but apart from my hybrid TD04 Mitsi Turbo most other turbo's ie std TD04's and T2's fitted to 9k's that ive driven start to struggle at the higher engine rpm and tail off,[/b]

That's because they run out of airflow in that given situation. All else being equal and fuel/ignition mapping correctly adapted to either situation, with less boost the same turbo might give close to the same hp at the top end of the ramge - only now it would be gradually building to that level of torque tather than tailing off. Put otherwise, that same T25 in your 2.3 litre 9000 could be bolted to a motorcycle engine and give peak efficiency at say, 13,000 rpm...

 

[Eric van Spelde]

The boost on the EV-1 was a fairly modest 16 psi or 1.1 bar. In an interview with Road & Track's technical editor, the EV-1 project leader conceded that given more time they would have tried higher compression pistons than the 7.2:1 they used, as 'the 16 valve engine has demontrated tremendous resistance against knocking'.

I think the point is, that for instance in the case of the Classic 900 Turbo, a fairly basic conversion like for instance Trent Saab's Stage 1 (220 bhp) gives about all the torque the transmission and front wheels can handle over a wide variety of road conditions, yet it still kind of runs out of puff towards the higher rpm when compared to say, an M3. So IMO any further development should go towards extending the torque curve towards higher rpm's - the EV-1 being a prime example of that. No way you could have hadled that kind of power with stock c900 running gear when it would be produced at the same 5,300 rpm of the standard engine. And yes, that means adapting fueling and ignition (turbo would have to be changed anyways for it doesn't care whether it's asked to produce 280 hp at 5,000 rpm or at 7,000 - too much is too much), but the same goes when significantly raising cylinder pressures for more torque (power) at a given rpm.

Saabine's engine is quite literally a 'race spec engine' and built with an extended redline in mind, but I think Bill J can attest that it's not much of a hardship in traffic. It idles smoothly and behaves quite well at low road speeds, and it's quite rewarding to have an engine that goes up and down the rev range that much quicker on demand. My experience from the former engine with the same Crower cams is that the engine equipped with them is compliant and quick enough at lower revs, before really taking off at 3,500-4,000 rpm...

 

[billj]

Originally posted by Eric van Spelde:
[qb]I think Bill J can attest that it's not much of a hardship in traffic.[/qb][/b]

It was very easy to drive in traffic, except when sitting in queues, like when leaving the show on Saturday, when the sport clutch was a little awkward. However, I'm used to the same thing in my Aero and in fact, your clutch was rather better than mine under those conditions.

Engine-wise, it was very easy to drive like a granny (which is how I drove it ).

 

[John Vaughan]

If this is strictly for a T25 turbo 9000 application you may want to check out this site.

http://www.saabperformanceparts.com/item212.htm

The timing on the exhaust valves is actually shortened to provide additional boost pressure early. From the explaination they sound like a winner to me.

 

[gundam_007]

does anyone agree that the red apc is worth the 350 dollars to invest in... and if anyone has does it really affect your daily driving?
was thinking of getting it after i sort through other "fixes" i have to do to the "RAG DOLL"

 

[John Vaughan]

Hi all,
If you are referring to the red APC chip from Swedish Dynamics; I have the red chip installed and the waste actuator shortened per their instructions. Does it make a difference?

Oh Yeah!! I would suggest though that you purchase the fuel controller chip at the same time to insure no lean conditions with the added boost.

 

[jeremyfrost]

Some interesting threads - thanks, guys. Tuning NA engines cetainly seems to be a different, but more expensive art than tuning a turbochaged engine. From my experience, it is a lot more costly, too!

 

[Eric van Spelde]

Some interesting threads - thanks, guys. Tuning NA engines cetainly seems to be a different, but more expensive art than tuning a turbochaged engine. From my experience, it is a lot more costly, too!
--------------------------------------------------------------------------------
 [/b]

Those who race Saabs, though, say that for driveability on the track you want to tune the Saab turbo engine more like if it was a normally aspirated one. From my experience, going beyond a certain level on the road it's much the same. I am certain a lot of what we see as handling problems with our FWD cars comes from the way the power is produced (throttle response with a certain delay - which makes you initially depress the loud pedal harder - and tending towards being on/off, lots and fairly brutally produced low/midrange torque), or at least compounded by it.
That, and at least with the Classic 900, it's easier and more cost effective to build a low(ish) inertia, high revving engine of which the power cuve smoothly builds to its high end peak than to make a 'bulletproof' gearbox (eur. 15.000 for a non-synchromesh dog box)....

 

[ylee coyote]

you are right ..
I have seen what excessive torque does to the c900 box

interestingly enough it seems to be the casing itself that splits...