Saabscene Saab Forum - Saab Technical Information Resource banner

1 - 18 of 18 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
Hi All,

I've 1992 LPT which I'm looking to make some performance upgrades to - Limited budget of a few hundred pounds - so chargecoolers not on the shopping list. Options I've been looking at are intercooler, air filter, FSE boost valve, increasing boost pressure, dump valve etc. Where's the best place to start? Will an intercooler by itself make much of a difference to performance, or do you get the benefits by coupling with other mods, if so which ones? Where's the most BHP per ££ going to come from?


Any advice gratefully received

Thanks

Peter
 

·
Registered
Joined
·
5,925 Posts
I'd have thought you wouldn't be far off an ECU upgrade with a couple of hundred pounds. Perhaps not Abbott - but www.speedparts.com and www.elkparts.com may be worth a try.

Bleed valve / Dawes device would be one of the cheapest options, though not sure how these would perform on LPT's.

Welcome to the board by the way
 

·
Registered
Joined
·
1,935 Posts
Abbott are selling off T16 intercoolers for £50 right now (RRP £503) + the pipe work for £40 extra (Abbott Racing ) .This would make a heck of a difference to your LPT. A free flow filter (such as a JR from Elk Parts ) would also make a noticeable difference in throttle response. IIRC you’ve got a bit of leeway to manual adjust base boost by shortening the wastegate actuator rod but I wouldn’t try this without a calibrated boost gauge.

A rising rate fuel pressure regulator (FSE boost valve) would improve throttle response too. I can’t remember right now if LPT 900s had dump valves: if yes the I would leave it alone so long as it’s working OK (it should be fine at LPT boost pressures). If they don’t have them then I’d consider one: Forge are nice (elkparts again) but TBH the SAAB/Bosch original is easily good enough.

Don’t forget the handling side of things too: polyurethane bushes on the front shocks and the rear trailing link arms will sharpen things up for not much £££.

Oh and welcome to the board .
 

·
Registered
Joined
·
1,676 Posts
First thing to add would be an intercooler from a T16 or '86-on T8 model (Abbott still has them for 50 quid?) My next step would be either a rising rate fuel pressure regulator (Trent Saab, £ 85ish) and a manual bleed valve (Forge, same as Abbott uses, I paid 36 euro at local speed shop) or a kit from Speedparts/SQR consisting of a chip upgrade for the Lucas fuel computer and a bleed valve. SQR particularly looks excellent value at SEK 1,650 (www.sqr.nu).

I would NOT do either of these before installing an intercooler, though.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #8
Many thanks for your replies- I'll go for the intercooler 1st and take it from there. Is it fairy straight forward to fit?

Cheers
 

·
Registered
Joined
·
11 Posts
Discussion Starter #11
As a newcomer to tuning, excuse my ignorance, but what does the manual bleed valve do and where does it go ? - couldn't see any details about on forge site other than picture- looks abit like the ecotek valve?

cheers
 

·
Registered
Joined
·
1,935 Posts
 As a newcomer to tuning, excuse my ignorance, but what does the manual bleed valve do and where does it go ? - couldn't see any details about on forge site other than picture- looks abit like the ecotek valve?[/b]
It isn't an Ecotek valve: does a different thing. On FPT SAABS there is a solenoid (not there on LPT C900s: I’m sure I’ll be corrected if wrong) connected to the ECU (or APC) whose job it is to control boost pressure (dependent on knock &c.). The bleed valve replaces the solenoid and allows you to set the max boost pressure manually (but you loose knock detection &c.).

The idea of the bleed valve is you work out by trial and error (with calibrated boost gauge) what your max boost is and set your bleed valve accordingly. When that pressure is reached the wastegate opens just as it would with the APC solenoid.

With an LPT you have a certain amount of leeway before you hit fuel cut off so the trick is to tune your bleed valve to just below that point.

BTW all that is meant to sound cautious, not negative.
 

·
Registered
Joined
·
8,948 Posts
Another Norfolk bod, we will soon have a handful.

I think you can also fit the MBC between the APC solenoid (if you have one) and the wastegate, so that you retain most of the APC function, but help keep the wastegate closed when it would normally be beginning to creep open.

Someone help me out here.

Andrew
 

·
Registered
Joined
·
8,216 Posts
I've only ever heard of that configuration being used with a Dawes Device, which is a particular type of bleed valve that keeps the wastegate closed until the desired pressure, therefore avoiding the usual situation where the wastegate starts opening at very low pressures (called "wastegate creep"). It can also be used to increase boost, but in the configuration you describe, it doesn't increase boost at all but rather makes the pressure rise faster.
 

·
Registered
Joined
·
1,935 Posts
I think you can also fit the MBC between the APC solenoid (if you have one) and the wastegate[/b]
As BillJ says that works for the Dawes Device: a two way or straight through bleed valve. The one Forge/ Abbott sell is a three way valve and takes the place of the original solenoid (if you have one).

I must look up the 900 LPT specs again to see what is and isn't there...
 

·
Registered
Joined
·
1,925 Posts
Hi Peter, If you want a T16S intercooler, mine is going spare as I will be upgrading mine. You can have it for a lot less than Abbott want. Send me a PM if you're interested, I can come up to Norwich sometime next month, to visit, as I'm from there originally.

Neil
 

·
Registered
Joined
·
14,305 Posts
OK, since I've been there, done that on both, I'll expand...

The wastegate fitted to all turbos is a bypass function that diverts exhaust gases around rather than through the turbo when it opens. In the simplest set up, a pressure line is taken from the compressor side of the turbo to the actuator. Once a certain pressure is reached, this forces the actuator out, thus opening the wastegate and preventing the pressure rising any higher.

A bleed valve may be inserted in this airway, and basically introduces a "leak" into it, effectively meaning that you have to have higher boost to move the actuator sufficient distance to open the wastegate. The "leak" vents to the atmosphere.

The Saab APC solenoid is nothing more than an electronically controlled bleed valve. Unlike bleed valves, however, it has 3 ports and vents back in to the intake to avoid errors from the loss of already metered air. The 3 tubes connected to it are labelled:
W: feed to the Wastegate actuator
C: from the turbine Compressor
R: Return of air to intake system

Actuation of the valve is controlled by the APC system, based on feedback of parameters from the engine as noted above.

An MBC like Abbott sell connects to the same 3 hoses, but allows a fixed rate of bleed rather than the variable one controlled by APC. Your maxium boost is determined by how far open this valve is. Knock detection remains; however there's less that the engine management system can do to compensate for it, as it can only now work with ignition and possibly fuelling.

You can insert a bleed valve inbetween the APC solenoid and the actuator in the W hose. This will have the effect of raising base boost pressure and also increasing the maximum boost pressure. A bleed valve is basically the same constrution and operation as an MBC; it just doesn't have the stub on the bottom to push the R hose on to.

All of which neatly brings us to the Dawes device, which is not in fact a bleed valve at all. Inserted between compressor or APC solenoid and actuator, it remains sealed until a preset pressure is reached, then opens to allow activation of the wastegate.

Of the three options, the MBC and the Dawes device remove the most APC control. Fitting a bleed valve in the actuator line less so.

Must be time for bed now....
 
1 - 18 of 18 Posts
Top