XFI: how to set crank ref angle and supercharging questions ?

[Iroc]

Hello.
First time engine project questions. I am trying to learn and do as much as I can for myself.
Have patience with my technical english, Will try to be as clear as possible

I have recently built a 383 TPI chevy engine here in Sweden, and installed a XFI ecu, but now I just have some questions on some things.

The idea of this motor is to have one tune for supercharging, and one tune for natural aspirated or what its called..
I have a supercharger with electromagnetic clutch from a Volvo Penta marine diesel engine that I will try to play with.
It is easy to turn it on and off, and tune economic without supercharger, and with supercharger it will be tuned for max power for streetracing.
Will use E85 for fuel.

Question 1: Now I mounted a comp cam supercharging cam, don`t have specs right now, but I can check tomorrow. Is it possible to have it run a little bit ok,even if the supercharger is disconnected or will the cam mess things up with bad vacuum?
The idea of two tune modes maybe not good..

Question 2: The ignition is flashing at 6¤ BTDC at the ignition mark at the crank, and the computer says 16¤ degrees BTDC when cranking with injectors disconnected.
Have set the crank ref angel in C-com to 6 degrees according to instructions for the standard GM HEI ignition.
What have I done wrong that make the ignition don`t match ?

Question 3: I`ve tried to start and engine idled at 1200 rpm, and the A/F ratio was very rich, something like 8:1 if I remember correct, but that must be because the ignition don`t match or what ??

Didn`t run like that more than 30 seconds, later an experienced tuner will tune the car at his workshop, but first I want the ignition to be correct, so I can test so the gearbox works so the tuner can drive the car on his rolling highway or what it`s called.

Maybe my stupid plans are not good, but I will try to make it as good as possible .

Don`t know what more info to add, this will be to long soon
I use map TPI from corvette 1991, with headers, forged pistons, crank and rods, electrical waterpump and electric steering servopump

All thoughts and tips are welcome
Thanks


Markku /

sweden

[TurboNova]

1 not sure what you are asking here but you can do this with only one tune.

2 if the timing does not match easy just loosen the distributor and move it until the timing does match.

3 if you are using a map sensor off a 91 tpi engine then it is the wrong one. You will need either a 2 bar gm sensor for up to 14psi or a 3 bar for up to 30psi. That is part of your rich problem. The other could be without the rotors moving you might be choking the air supply from the engine.

[Iroc]

Hello Brian and thanks for answer.
I have read your answers at a lot of different sites, and you seems to know what you are doing

1. With my first question I meant that the motor is now without a supercharger, just like a regular TPI engine. And now I want a good economic cruise tune for that, if the supercharging cam durations don`t make things bad if you understand.

2. The ignitions shows 6 degrees at the harmonic balancer, and if I turn distributor then the ignition at the balancer will change or is it just in C-com the ignition changes ?
I will try to turn distributor right away and hope it is that easy.

Where can I read more about crank ref angles ?? I have read XFI manual, but that don`t make me smarter. It maybe will be simple and just my brain that mess things up with thinking right.
If i set a different crank ref angle in c-com, will it still be at 6¤ at the harmonic balancer, or what will change when you do what ?

3. Jaaa, så klart, as you say in swedish. Yeees, Of course I need to mount the 2 bars Map sensor right away and tune with that for more easy operating and switching with and without supercharging..
But thats not the problem as I have the motor like a regular TPI right now and no supercharger choking the air.

Sorry for all my newbies question, but it is really fun to begin to understand "all" about how it works and I want to understand as much as possible

[TurboNova]

1 running an engine with a blower cam and no blower will not be a problem to tune.

2 it is just that easy, if you are using an HEI you need to use the recommended crank reference angle. If the timing does not match the all you have to do is turn the distributor until it does.

3 I would suggest using the correct map sensor for the blower so you will only have to tune the NA area once.

[Iroc]

Thanks again for clearing things out.
I will in a few days, take the car to a swedish rally/tuning company , and let them clear out the rest and hopefully tune it with sucess..

Have a nice day over there