Best Mods To Do First [Archive] - SaabCentral Forums

: Best Mods To Do First

9th May 2002, 07:12 AM
Hello All,

I'm looking for some ideas for the first mods to do on my Saab. I'd like to keep it as close to factory reliability as possible but a little extra umph never hurt. Plans so far are an induction kit, stainless exhaust, a tinker with the APC, Rising rate fuel pressure regulator and a bailey dump valve.

Any good guides? How much should I tweek the P and F pots by? Whats the best induction kit, RRFPR etc. What BHP and 0-60 do you reckon I could get with the above tweeks?

All opinions and suggestions gratefully recieved. I've never modified a Saab before. Its a 1991 900 T16S with 78K on it.

Thanks All.

9th May 2002, 08:12 AM
<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>1991 900 T16S with 78K on it. </BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>

I'd be careful that's not even run in yet :grin:

I've done similar mods to the ones your planning to the same model of car (with about double the mileage).

It feels like I've got a comfortable 200bhp but this is just a guess.

I've put the P &amp; F pots on the dash to fiddle with them so I never know exactly what they're set to.

And be prepared for some gearbox agro!

<font size=-1>[ This Message was edited by: Keith on May 9, 2002 1:13pm ]</font>

9th May 2002, 08:38 AM
Yeh it is low.

I don't want to sacrifice a large amount of reliability. But I don't light the fronts up in every gear possible so I can't see another 30 - 40bhp hurting. How much boost can a T16 run in a reasonably standard setup? 15psi? Their about 7 as standard aren't they?


9th May 2002, 09:02 AM
Standard boost for your car is 12psi I think.
Mine will produce a boost spike at 25psi if I wind the pots right round, but that is not very useful! It seems happy with about 17psi at high revs.

Marko A
9th May 2002, 09:28 AM

You have T16S ī91 and you live in UK, so very likely your 900 is equipped with Lucas fuel injection control (you can verify this from the airmass meter on the airbox).

If itīs Lucas, instead of RRFPR, Iīd recommend you to get reprogrammed chip in the Lucas ECU.
Check out,
Correct amount of fuel with no need to do any adjustments, ie a bit more richer mixture under acceleration.

And like Keith said, best way to adjust APC is to get pots inside the cabin, permanently or not.

I have T16Sī91 too and gearbox gave up @ 155Kmiles :eek: otherwise still going stronger every day!

Marko Alatalo
SAAB 900 TurboS


<font size=-1>[ This Message was edited by: Marko A on May 9, 2002 2:32pm ]</font>

Johann F
9th May 2002, 11:16 AM
I found a RRFPR really improved the drivability on my 91T16 - not an increase in absolute power but better pick up and smoother power pregression. The fuel chip does the same thing and is perhaps the 'correct' solution when you want a bit more fuel but you can adjust an RRFPR to suit your particular engine by changing the base fuel setting. As you have a 91 and not a 92 you can get rid of the CAT - don't put in a non-cat downpipe as this will still interfere with flow but sleeve on a straight section after you have cut away the flanges. You will need to do either the fuel chip or RRFPR with this mod as you are going to need some more fuel to compensate for the better breathing of the engine - this should give you much better high rev power. Induction kits and cone filters are a bit of icing on the cake - don't expect big power gains. APC mods - yes do them but I would disable or modify the cutout overpressure switch as sudden engine power loss under load is no fun and no way to treat your gearbox and engine mounts. Another good mod is to change the basic timing from 16 to 18-20 deg - you will get better off boost performance - at the same time bend the limit tab on the vacuum capsule arm to alow it to retard to the same level as before.Getting peaks of boost for surges of power is easy via turning up the P but this sudden loading is not good for the box - that's why the APC limits not only the level of boost but also how fast it rises. I'm trying to keep the rate of rise to a minimum to prevent such spikes while alowing it to sustain a practical 1bar-ish max.

Marko A
9th May 2002, 01:58 PM
I know many have had good experiences with RRFPR, but some of the dyno sheets (with A/F ratio) has shown some problems with highboost@highrpm -> lean mixture.

Hereīs what "Dr Boost", the guy who works for Saab engine management systems, said about RRFPRīs on bulletin board:

First, so that thera are no misunderstandings, I do not like RRFPR.
The reason is simple:
The RRFPR will give you too much fuel in the low/mid rev-range where the fuel delivery vs. fuel need is OK, at least more or less OK.
The engine will run overrich, to a degree where power decreases, do we want that ?
Another problem is that the oilfilm on the cylinderwalls will be washed away.
And we donīt like that either, do we ?

So, back to the basic problem, when fuel delivery vs. fuel needs doesīnt match in the lean direction.
This happens generally when youīre running the engine at high rpm and hi load.
The fuel injectors are too small, or the fuelmap in the ECM is "too small".
So, to get the correct A/F ratio at high rpm, normally the fuelpressure is too high at low/mid revs under boost condition.

The best thing would be to fit an EEPROM, "chip", that will give the engine more juice, or if the injectors are too small install fuel injectors that matches the fuelneeds AND an EEPROM designed for these new bigger injectors.

I know that you canīt always get what you want, so....well Iīll guess that this is the reason why itīs possible to sell products like RRFPRs.

and hereīs the link for the whole discussion:

Speedparts/BSR claims that Lucas injection system with stock injectors (though many other mods) is good for about 220-230bhp.

9th May 2002, 04:54 PM
For those of use the Bosch LH systems though, there doesn't seem to be much in the way of reprogrammed ECUs about though. And from what I understand of the way that it works at full throttle (it appears to ignore the mass meter completely and run from a fixed map) there isn't much in the way that it can be improved.

Its either a fully mapped 5th injector or junk the LH and go for an aftermarket system which would allow the ingnition timing to be fully sorted as well.

Jo K
9th May 2002, 07:09 PM
Stromqvist Racing don't seem to be mentioned too often here, perhaps because their website ( is in Swedish :smile:

However, it's not too difficult to work out what is going on (go to Webshop, click on Saab and then look at the various categories).

They do a fuel chip ("branslechip" from memory)and an APC mod for our cars for what looks like a very good price (no quoted HP though). You might want to check them out. They also do exhausts and other bits if you're really keen.

They've been mentioned over at Saabnet a couple of times but you'll need to check for first-hand experiences (I don't have any).

Best o' luck

Jo K
'85 Aero 195000kms

Johann F
10th May 2002, 06:31 AM
Overfueling is a problem that I have experienced when setting the Trent RRFPR at their recommended 3.2 bar on a Lucas system. I have set mine to the stock 3bar and it's sweet as a nut!. Lucas FI is quite different from the Bosch as it constantly computes new fuel maps from Lambda readings when at idle. As the vacuum is pulling the rate down by the same increased level ( 1:1.7) the fueling maps start from here (about 2bar fuel pressure at manifold idle vacuume) - the ECU thinks there is going to be a 1:1 rise in fuel pressure from this point (standard FPR)and it also thinks the actual fuel pressure is about 2.5 bar. However I also know that there is constant adjustment via the feedback from the Lambda sensor which will keep the fueling to standard levels if you accelerate gently and don't go over the limits of the closed loop into WOT. It's over these limits (I believe) that it uses the fuel maps it has calculated and that are now being overriden by the RRFPR. The result is more fueling only when you are putting your foot down. Similar ECU 'fooling' goes on when you fit one of those Ecotec devices - at idle the air leak fools the ECU into a higher fuel delivery when you are accelerating and the valve is shut - you don't want to run a RRFPR and an Ecotec at the same time on a Lucas FI car - it will not like it!

10th May 2002, 10:02 PM
There is a chip available for the LH in Australia.

I had the chip fitted in my last car and it worked really well during Australias problems with inconsistant fuel qualities.

However my new car runs on nothing but 98ron and the chip when i tried it caused loss in power due to over richness.
I now run a fifth injector to support 18psi boost levels. While this is ot perfectly setup on my car yet, it is a very good mod.

3rd August 2002, 04:56 PM
What is the chip for the Lucas system? Is it available in the UK?

Oh, and is it good? and worth it?


4th August 2002, 01:48 PM
Everyone on always talks about the Saab tranny not being able to handle over 200hp, but the newer Saabs (9-3's) must have a tranny that can handle more because the 9-3 SE has 210 and the 9-3 viggen has 230 so what can those tranny's handle???

4th August 2002, 05:03 PM

since yours is a '91 it has a mitsu te-05. this turbo has decent spool up speed, but it maxes out at around 18-20psi. theres a lot you can do with your car as far as mods go, but even stock boost levels are very hard on the archaic c900 tranny.
to safely run high boost levels you will need a trent saab rrfpr, 30# injectors, and a water injection system. a knock led light will also help.
further mods could be a front mount intercooler, switch to '85 cams as well. if you want 20psi+ you will need to get a TE03/04 ball bearing turbo. to run very high boost like that on LH 2.4 is very tricky and you WILL need dyno availability.

play with the pots in the APC and you will gain a few psi which may make all the difference for you.

Eric van Spelde
5th August 2002, 09:51 AM
A few remarks:

* The lean running at high revs/high loads (i.e. significantly higher than stock boost) is a documented feature of (at least) the Bosch LH 2.2 system. It switches from a map based on AMM input to a 'fixed' map at 4.5 or 5K rpm IIRC. The only proper way to overcome this -short of redoing the complete fuel map (including the 95% of times the stock map's entirely adequate) using an aftermarket engine management system- is via a programmable 5th fuel injector system.

* Apart from that, an RRFPR is a good aid in briniging back some of the throttle response we lost when going from twin Webers or Dellorto's to emmissions-driven developments on the EFI front. Yes, an RRFPR gives fair squirt of fuel when opening the throttle (as did the carbs) but that is only helpful when getting the engine out of it's low-rpm, no-boost canyon... Apart from that, it gives some control over fueling to account for small to middling modifications on the engine front. For what it costs, I found the Trent RRFPR a very worthwhile addition. But no, it can't replace more detailed modifications to the fuel system when running out of the fuel system's capabilities at the top end of things, and yes, it can/will work against you when flat out in the lower gears for most of the time, like on a racing track or the dyno...