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453 Posts
Discussion Starter · #1 ·
OK, I have a T16S which I wish to breathe on a little in the coming months.

However, it is my daily driver, so it must remain 100% reliable, and drivable day to day.

Suspension/handling - given that the ride is already pretty hard and I find myself grounding the middle box on speed bumps frequently
, I don't want to go stiffer or lower, but is there anything that needs doing to tighten up the handling? Perhaps some sort of brace across the boot to stop it flexing? (although I don't want it turning into an oversteering monster!!)

Performance - I'm very aware of the c900's gearbox weaknesses and I don't want to kill mine.

My options seem to be

- APC twiddling
- swap out APC with that of tuning company

Also, filter and exhaust (inc. 3" downpipe)

I have chatted at length with Matt Faulks ( ), and his stage 1 kit looks very interesting. ( - APC + filter) My car is decatted already, so it looks like for 300ukp and half an hour's work I could have a reliable 205bhp.

What do people think? Would it be worth getting a bigger downpipe and exhaust? Where from?

Would be interested to know about people running tuned c900s as daily drivers!

762 Posts
as mine is a T8 some thing might be a bit different (only vales )

I use it as a daily driver, so far mods are.....

1.ITG airfilter
2.modified airbox
3.straight pipes on exhaust(no middle box)
4.Tweeked APC unit(settings just under type "M")
5.Heuschmid camshaft
6.silicone vacuum hose`s & APC hose`s

as a daily driver its fine, only down side is 20mpg
next mods will be......

1. 9K FMIC
2. baily or forge dump valve
3. -40mm lowering springs
4. 3" exhaust
just to name a few....

but its booked in at Watton RR just to see if everything is OK....

Hope this helps Paul

293 Posts
My LPT is now putting out 40 bhp more than stock using an MBC and a 900 intercooler, running about 1 bar boost normally. It makes it much more exciting to drive but is still very controlled and does not feel stressed - you can drive it smoothly but power is there when you need it. It is my daily driver and I live in rural Suffolk with very bad roads, so I did not want to lower it, but to improve handling I fitted heavy duty rear springs of the stock turbo height and stiffer shocks. The ride now is firm but not too harsh, and there is less understeer. I removed the cat and fitted a straight pipe. Also have a Forge dump valve and silicon hoses. The exhaust is a bit of a bottleneck on them and at some point I would like a larger downpipe - also an upgraded intercooler, maybe the Volvo 760 one.

2,599 Posts

Have you or anyone else got the APC settings (resistance of the three pots) for the M-spec and other APCs. There was a page on the web with them on but I understand the guy who owned the page got fed up of people saying his values and method of tuning was wrong, so he removed the page. Unfortunately I never got round to recording the details

1,676 Posts
Originally posted by Adrian:

Have you or anyone else got the APC settings (resistance of the three pots) for the M-spec and other APCs. There was a page on the web with them on but I understand the guy who owned the page got fed up of people saying his values and method of tuning was wrong, so he removed the page. Unfortunately I never got round to recording the details       [/qb][/b]
I've still got printouts from the original tv41mxa/tweakyourapc site - including the specs for the 'red box' and 'type M' APC's. If the owner of the now-defunct site (I think it was Marko Alatalo) has no objections I'd be happy to put photocopies in an envelope for anyone who desires them...

More APC information and backgrounds can be found on and .

661 Posts
£300gbp is alot of money for a tweaked apc and air filter imho
At least part of that money could go towards the JT downpipe and removal of the centre silencer/cat.
There is information availalbe as Eric has pointed out that will allow anyone handy with a soldering iron to make a box up that will hold around 14psi provided the car is capable.
Spend your hard earned on other areas if i were you.


1,676 Posts
Must say that I agree with Tandino's comment - at this level your money is better spent at hardware than on an APC upgrade, as a) an APC upgrade tends to make the car stronger where it's already very good (midrange acceleration) and does little to strenghten the weak links (low down response and power fading towards the top end), B) tweaking the APC only has its limits because you have no means of controlling fuel delivery and ignition timing to match, therefore you cannot hope to achieve comparable results as with 'chip tuning' the integrated engine management systems of later cars (frankly, as the APC controller is nothing but a box of resistors and stuff an upgrade should be a mere fraction of the price of a DI/Trionic upgrae anyways) and c) there is some flexibility in the APC you already have - changing the values of R42 and R138 and retrimming the pots as per aforementioned sources would be sufficient for it to cope with any other modifications at this basic stage.

My personal starting point from an engine point of view would be self tweaked APC + air filter element + exhaust downpipe + removal of front muffler.

As for the suspension I would strongly recommend starting with shocks. A nice set of Koni's will transform the handling and probably help with your grounding prbolem at speed bumps, too. For everyday use, both Abbott and Trent Saab springs would represent and excellent compromise. The slight lowering these afford would be very likely offset by the reduction of brake dive and squat under aceleration (the front axle tramp on classic 900's when accelrerating is mostly a function of soft or tired rear springs).
I would get a 'performance' alignment to the following spec at the same time: 1-1.5 degrees negative camber at the front, 2.5-2.75 positive front castor and the smallest amount of toe in the shop can dial in without it actually being zero.
A favourite of mine is to remove the front anti-sway bar. I found understeer is all but eliminated and traction is dramatically improved with this measure. As for inducing lift-off oversteer, I Personally haven't experienced any more than a useful tightening of the line when going off the throttle. Lack of body control through less than perfect springs/dampers will however be shown up very quickly with this method, leading to vicious under/oversteer at either end of the envelope - but then again I had the same findings when running with the stock 900T set up with no torsion bars on either side.
The rear brace is a good idea also - I'll have hat one sorted as soon as I have my *&^%$#% turbo back...

54 Posts
As regards cost, and apologies if this is getting slightly commercial now. Bruntingthorpe is £70 p/h per car, you also need to get 3 suitable 900's together (Bosch, Lucas and Lucas Cat), mount wide band Lambda sensors, run a good deal of track time in all possible combinations of load and inlet temp, analyse the results and make changes accordingly, run them again to ensure the setup is sound etc. etc. Its not a quick and simple job and its been pointed out before these are not simply boxes with the pots turned up!


1,219 Posts
I self modded my APC (i have a 9000 Turbo with LH 2.2 and APC), modified the retard stop on the advance/retard capsule and now run 15psi al lthe way to redline, with a dash mount potentiometer for boost control. i removed the boost taper, and now it feels much better all the way to 6k rpm

11,343 Posts
Many thanks to Matt who is onto his website designer asking why he used one of my photos?
Seems like neither Matt nor I knew until today.

Meanwhile, back on the subject, I agree with Matt that the cost of developing something can be significant and needs to be factored in to the retail price - whatever the item may be.

2,599 Posts
Biggest problem I have is boost taper at higher rpm. Mid-range with tweaked APC (Lucas injection) and JR filter + Abbott exhaust (without first box) is great. Mid red level, but as the revs climb the boost drops back to the red/orange i.e. right at the start of the red section, stays there all the way to 5500rpm.

Any tips on how to stop this taper?

1,219 Posts
You can make your box to stay on a passive default duty cycle to red line and adjust boost only
with P pot - ....... and connect R41
and R101 together from the right side, when viewing textmarks right way.
This will give you a really smooth, directly adjustable with P, boost that
doesn´t dip or do any kinds of shaking when the boost/revs go higher......This means that boost pressure sensing circuit (F") has by-passed and
impuls dose, in other words P setting, controls only the boost
Got that from a no longer available APC tweaking site... works great too!

PS - change R42 to a straight wire to get faster spoolup of turbo

14 Posts
Jumping in, as I received the link to this thread...

I would start from the most BASIC of upgrades - getting the baseline. Change the rubber sleeves to something trustworthy (Silicone, if not SAMCO) to get the induction system tight and leak-free. Make sure all nipples/hoses are clean and tight. Clean the contacts in all elecrical parts. Refresh the earth points, if they look corroded at all (this has proven to be a great mod for my friends in Japan).

Before throwing a lot of money at your T16S, make sure the little things are taken care of.

Have you considered water injection? I'm toying with the idea, and it shouldn't take away from the reliability.

I'm looking at the following to come...

1. Downpipe with separate turbo/wastegate pipes (joins downstream)
2. Equal length headers
3. TE05 with 360* thrust bearing & larger compressor
4. Water injection
5. Dual IC or 9000FMIC
6. Bypass throttle-body coolant flow
7. "Boxed" front A-arm

I have the JT 3" turbo-back piping, but have found that the "elbow" immediately after the turbine is very restrictive, and causes quite a bit of wear on the turbine.

The suspension was greatly improved with an addition of Bilstiens, but as Eric says, Koni's would probably be better. ...just can't afford them I have Jamex springs, so my catalyzer (3" Catco SS unit) hits "speed-bumps" in the parking lot. A lot of zig-zagging to lessen the blow I can't push a box of cigarettes into the wheel well at the rear.

I am running about 1.24 bar with a atmospheric discharge blow-off valve (TurboXS RFL) with meager-to-acceptable results.

Now that we have the basics out of the way, let's consider the APC mods, Stand-alone Fuel Management Systems, Nitrous IC cooler, etc, etc...

I'd love to hear what the folks on the "other" side of the water are doing


1,592 Posts
Hi Pesca 555,

I have been in the fortunate position to acquire my classic 900. I don't think you will find many with quite such an extensive list of mods, including:

1991 B234 head with 2.3 n/a cam,
B212 custom intake with 4 additional injector bosses and custom fuel rail,
Modified APC
EGR flap removed from exhaust manifold and egr removed from car,
MSD Boost timing master and inline check valve,
Stock retard defecated from distributor vac capsule
Passive mod APC system,
30lb/hr auxilary injectors controlled by:- ERL HMF2 auxilary injector driver
Mitsubishi TD04 15t-6 turbo with ported inlet and braided oil feed and return lines,
Garrett 0.5 bar actuator,
Bailey DV26 atmospheric dump valve,
ERL Aquamist 1S water injection system,
Volvo Front Mount Intercooler,
Battery relocated to passenger side for:-
JT 3" Downpipe with centre silencer removed - one rear box with Jetex twin rear pipes,
Aerospace quality check valve

When the ERL injector driver is mapped, I will put it on the rolling road. Should be interesting...

1,676 Posts
OK then, here's mine

'85 c900T8 ex-factory.

'91 B202 block
92 mm forged Sweedspeed/Cosworth pistons, weighted at 481.5 g
shot peened and weighted rods
shot peened and fully balanced crank
Piston oil cooling jets

T7 (9-5) 16v cylinder head, modified to fit B202 block
Gas flowed
Bigger valves
Stock B235E cams
Custom Sweedspeed intake manifold
EGR ridge removed from exhaust manifold

Sweedspeed full race modified T03 turbo; stock .48 A/R turbine, bigger compressor with 'angled' blades

Sweedspeed built air/liquid IC (converted from '85 all-alloy 900 IC)
Custom heat exchanger in front of engine coolant rad (54 x 15 x 3,9 cm core); Davies Craig electric water pump
Simota cone air filter; stock T16 AMM-turbo pipe; M89- 90T16 alloy turbo-IC pipe; custom IC- TB pipe

Trent Saab/FSE atmo dump valve, originally meant for Scooby WRX (classic shape) Group N rally car

Custom 3"downpipe, no front silencer; 2.5" Simons half system w/ twin tailpipe

LH 2.2, Eprom modified at Beek Auto Racing
346 cc 9000 2,3T injectors (Bosch 0 280 155 009)
Trent Saab/FSE rising rate fuel pressure regulator

M88 9000T DI system, Eprom modified by Beek Auto Racing
Black DI cassette

Blitz SBC i-D III sequential solenoid boost controller

Trent Saab/Norgren crankcase breather check valve

Lightened/balanced -M90 flywheel (9.0 kg -> 7.0 kg)
Sweedspeed/AP racing four puck copper clutch disc
Balanced pressure plate

M'91- gearbox, #6 primaries

Conversion to '88+ brake system (rear handbrake)
M90- 9000 front calipers and discs
Brembo discs/Ferodo DS3000 pads in front; OE discs/pads rear
Goodridge stainless steel braided brake lines

Merwede road/race springs
Koni shocks; SAS poly shock bushings
T16S rear sway bar; no sway bar up front

6.5 x 16" Aero wheels, Toyo Trampio R1R 205/50/16 road legal semi race tyres

Saab accessory fender flares, colourcoded
Colourcoded and wire-meshed grille
Debadged exterior

OE tan velour interior; side bolsters on front seats enhanced with 2 cm extra material & re-upholstered with biscuit leather
Leather door panels
Electric window lifters replaced by manual winders
Three spoke leather Saab/Momo steering wheel as per Carlsson
Custom carbon fibre dashboard
Saab accessory wooden gearlever knob
White instrument dials (Vincent Tong, Canada)
Aluminium panel on steering column with Shiner A/F gauge and starter button
Aluminium radio surround
Center console parts and sill covers sprayed Opel Rembrandt Silver
Carpeted part of center console deleted
Kenwood PS909 CD head unit; two Genesis SA30 amps for left and right stereo channels
Görlich VK 160 MkII midbass units and Vifa/Scan Speak 20 mm tweeters in custom fibreglass kickpanel builds; DLS cable
Optima Red Top battery relocated to boot
Spare tyre and jack replaced with foam can
Rear shelf deleted
Erik Carlsson's signature on right sunvisor

Currently awaiting turbo to return from 2nd rebuild - five weeks and counting...
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