LPT to FPT. Is b202 good enough?

[joulupukki]

Moro Saab addicts,

We all know that the 900 engines are reliable. Now the question is, are they good enough to survive a LPT to FPT conversion after ~400 tkm.

My engine is in OK condition currently. Does not eat oil and the engine runs smoothly (idle is not as stable as I'd like to see). No noises from the gearbox. It is equipped with factory default intercooler.

Many sources state that the LPT engines are 100% identical to FPT models on the net. Is this really true?

The conversion seems to be pretty straightforward. Especially because I do not need the pressure gauge in the front panel. Send me PM if you have a cheap APC for sale including the connector .

So Gurus, whats your verdict, am I gonna kill my Saab?

[jcarlson]

Slightly unstable idle is a feature in Lucas EFI equipped 900s, so nothing to worry about.

LPT engines are exactly the same (pistons, rods, head, camshafts etc.), only differences are the intercooler, fuel chip inside Lucas ECU, APC and boost gauge. Also gearbox primary drive is often #7 in FPT's whereas LPT's have #6 but this will just give you better acceleration than a true FPT actually.

So absolutely nothing to worry about if you have an IC, correct fuel chip and a correctly installed APC.

You can contact me with a PM if you need a fuel chip.

[joulupukki]

Today I'll get the APC+solenoid valve+knock sensor. However this fuel chip stared to worry me.

How do I know if mine will not cut at 0.6 bar? Where is it located?

Car was first registered in 03-90.

[jcarlson]

The chip is inside the Lucas EFI ECU, passenger side footwell. 3/90 registered car with green injectors will have the fuel cut and the chip should be replaced.

[joulupukki]

Hi,

I have checked the part no. for the ECU:

8789661
Date Code: 0790
Made in UK
80105F

I'd like to avoid spending $$$ on a new unit, so could anyone clarify that this one will cut at 0.6 bar?

If so, is there a "workaround" to avoid this?

I tried to search the web on this topic. There seems to be some info in Swedish saab forums, but I can not understand anything.

http://www.900klubben.com/phpbb2/viewto ... b37d238d5d


Regards

[jcarlson]

Yes, that is a M90 CU14 Lucas which will have the fuel cut. But you do not need a full new ECU! Just the memory chip inside it, which will cost 30€.

[joulupukki]

Hi Guys,

Few questions regarding to LTP->FPT mod.

Where do I need to connect the "Pin 25: RPM in" from the APC box?

Is the polarity important for the knock sensor or I just need to connect the two wires to pin 16/17 regardless of the order?

I was hoping that I will not need a pressure transducer. Unfortunately one needs to be connected to pin 10/23 on the APC unit. What would be the simplest fix? Do I need any special gauge, or is it ok if I buy the cheapest one in the local store?

No. of my APC unit is 7524127. I am trying to get the cabling right following the pin layout here: http://forums.turbobricks.com/archive/i ... 29715.html

Thanks,

[jcarlson]

RPM Input is connected to the wire that goes from the ignition amplifier to the ECU.

Knock sensor polarity doesn't matter.

You do need the pressure transducer for proper APC operation and boost control.

[joulupukki]

One last question

I am following this guide:

http://900aero.com/main/diy_main_lpt.htm

and having trouble with this step:

"3. Blue/red to the blue wire under the TSI socket (funny round 6 pin socket at the front of the fuse box)"

Which pin is the blue/red wire exactly? I am having some difficulty to identify this one because my APC connector does not have standard coloured cables..

It seems that I have forgotten to get a pressure transducer.... so my car will stay LPT for a few more days now

[jcarlson]

Blue/red refers to the RPM input (pin 25), as the RPM signal can be obtained from the TSI terminal.

[joulupukki]

I found an ECU unit, a pressure transducer and a overpressure switch from a scrap yard. Paid 30 Eur for these.

ECU no is 0280000521 which is supposed to be a 16V FPT unit. I guess I just need replace the LPT version with this one and forget about the fuel cut issue.

I could not remove the lower dash fascia completely First I removed the center console and then three more screws, but something still holds it in the middle. Any idea what I missed?

Anyway, I managed to locate the overpressure switch and the vacuum/pressure pipe. (Yeah, my head was banging against the break pedal... not fun)

Does the polarity matter for the pressure transducer? I measured its resistance with cables on and engine on, it was 8.0 Ohm. What is the correct wiring for the over pressure switch? I tried to connect it the same way as the old one was, hope I did not screw it up in the dark (lower dash fascia on... )

So that's all for now. I'll connect the whole stuff together tomorrow.

[jcarlson]

I found an ECU unit, a pressure transducer and a overpressure switch from a scrap yard. Paid 30 Eur for these.

ECU no is 0280000521 which is supposed to be a 16V FPT unit. I guess I just need replace the LPT version with this one and forget about the fuel cut issue.

This ECU will absolutely NOT work. You've bought a Bosch LH 2.2 EFI unit from 1984-1985 which is completely different from the Lucas CU14.0/14.1 system that 1990-1993 900 T16/S has. And no, you cannot make it work with the Lucas system at all, which has a lambda sensor, catalytic converter, different airflow meter, completely different injectors etc.

Why is it so hard to swap the fuel chip in your current ECU for one that will work?

I could not remove the lower dash fascia completely First I removed the center console and then three more screws, but something still holds it in the middle. Any idea what I missed?

There's a bolt behind the ashtray (actually it also functions as the nut that the ashtray itself bolts onto).

Does the polarity matter for the pressure transducer? I measured its resistance with cables on and engine on, it was 8.0 Ohm. What is the correct wiring for the over pressure switch? I tried to connect it the same way as the old one was, hope I did not screw it up in the dark (lower dash fascia on... )

So that's all for now. I'll connect the whole stuff together tomorrow.

Should not matter for the pressure transducer either if I remember correctly at all. Overpressure switch just connects the fuel pump wiring and switches it off in case of overboost so it's easy to connect as well.

[joulupukki]

Hi,

I spent my whole morning under the car. I still could not remove the lower dash fascia, even though I removed all the visible screws. (even the one behind the ashtray) Something holds it back in the middle.

Anyway, I managed to mount the new overpressure switch + pressure transducer.

Does the pressure switch have only two connector connected? I can see three pads on the unit, but one of them was not connected in my car.

It was a pain to get the knock sensor into position. The trick was to hold the screw with a thin wire from above.

... And hopefully this is the last issue I have...

I could not connect the R pipe of the solenoid switch. As I understood it should go somewhere on the pipe from the airbox (AMM) to turbo. The pipe I have in my car does not have a connector for it. Do I need to get a different pipe or I just missed it?

When the engine is running and I increase the RPM to say 3000, I can see that there is some pressure building up from the solenoid's R terminal. Does it mean that the system is working (besides the open R pipe?) When I turn the key on (engine not running) I can barely hear a ticking noise from the solenoid when I put my ears on it . If I remove the connectors from the pressure transducer then there is a laud clicking noise from the solenoid valve.

Can I drive the car with open R pipe without any damage to engine?

Thanks for clarifying that I purchased the wrong ECU unit.

Does anyone need it?

Regards,

[jcarlson]

Pressure switch only has 2 connectors in use, yes.

There should probably be a blocked off connector in the plastic pipe between the AMM and the turbo inlet. Possibly not in an 900, but in 9000's at least. If not, you could just drill a hole and install a threaded hose connector somewhere in the pipe. Or get a pipe that has it already.

The operation does sounds correct so it probably does work yes.

You can drive the car with an open R hose, it should work otherwise pretty much correctly but you will just have a small air leak from it. Lucas CU14 is pretty good at hiding air leaks so you might not notice any change in drivability because of it.

[joulupukki]

I took the car for a test drive.

The engine pulls better which is sweet.

What is not so sweet when I floor it, sometimes the engine stalls for a second.

This happens especially in 3rd gear (I don't dare to floor it in 1-2 gear, after all this is a 21 year old car...).

All in all, do I have the issue now with the fuel cut?