SaabCentral Forums banner
1 - 7 of 7 Posts

·
Registered
Joined
·
1,446 Posts
Discussion Starter · #1 ·
I might be in a need to change out the low pressure turbo engine currently in the car (no oil pressure, have run (at iddle) this engine for experiments for some time - so perhaps it`s damaged already) with n/a (have access to good 16v n/a engine).

What would you say if I swap the engine like that (without opening up and changing the pistons) and hook it back to the low pressure turbo system (turbo, ECU etc. ...) and run it on low boost (eventually maybe adding APC system for safety reasons)?
Would high compression engine not be happy going around at low pressure turbo settings (0,4 bar IIRC)?

This might be easier, might give better low-end performance and be OK for my needs (I`m not after big turbo power).

As far as I understand this would involve only taping the oil supply tubing for the turbo.

If this is likely to make knocking problems I eventually could open it up and change pistons.

Thank`s for your input.
 

·
Registered
Joined
·
7,034 Posts
Its all been done with success before. I think you might want to swap the exhaust cam as well.
 

·
Registered
Joined
·
1,446 Posts
Discussion Starter · #3 ·
Its all been done with success before. I think you might want to swap the exhaust cam as well.

you mean no worries about high compression pistons + lpt?
camshafts are easy compared to pistons.

Thank`s!
 

·
Registered
Joined
·
7,034 Posts
Well I didn't say no worries, but its certainly possible to low pressure an NA engine. Going full boost not a fantastic idea, but you seem to be realistic about that. There's certainly pitfalls and caveats and you have to do it right, but its doable.
 

·
Registered
Joined
·
1,446 Posts
Discussion Starter · #5 ·
I understand well that lower compression is meant for fpt.
In this case I just want to go easiest route and swap n/a without changing the pistons / or having to open and repair original fpt engine (which I at this moment yet don`t know is shot but it has been run at iddle without any oil pressure).

certainly, if installing n/a will be keeping lpt specs and perhaps install APC just to see if/where/when it knocks.
 

·
Registered
Joined
·
7,034 Posts
I think I would start first by doing some more investigation to establish why you have no oil pressure on the existing engine. Replacing an oil pump for instance is much, much easier then pulling engines etc.
 

·
Registered
Joined
·
1,190 Posts
If you install an N/A engine, just keep the boost at 5psi max to go along with premium fuel only and you'll likely never knock. I speak from experience as my 8 valve sedan has been an N/A turbo for around 2000 miles now. I originally also planned to use APC, but have since discovered that it is pretty much pointless. In my opinion, anything over 5 psi, whether it is possible or not, is just too much for the N/A if you intend to get any kind of longevity out of it. At 5psi and less, I'd expect the engine to wear quite normally. At 5psi, you'll also have enough boost for some reasonable passing on the freeway or for climbing mountain passes at high altitude. The performance will be peppy, but not earth shattering. Really, for a daily driver I actually think that a 10:1 compression (N/A) engine with 5psi max turbo is more practical than a full pressure turbo. It provides more than enough power for those commuting and daily driving conditions while also being a little better on fuel economy than both an N/A without turbo and a FPT in real world conditions (from my initial observations anyways).

If I was in your position, I'd do the swap, set the wastegate to 5psi (verify with an actual boost gauge) and keep it topped with premium fuel. :)
 
1 - 7 of 7 Posts
Top