This forum has plenty of tuning articles and advice, but I can't seem to find advice on how to set up an initial spark tune to get an engine running (like trying to run a 454 with a '165) in the first place. How can I estimate what the spark table should look like?

 

What are the specs on the 454, heads, cam, vehicle, transmission, gear ratio. Also are you running some form of Mass Air Flow run PFI on the 454?

 

The 454 was just an example. I'm planning a pretty serious maf turbo v6 build though, can't afford to mess up. I need an eqation or a link to a good tech article, something along those lines.

 

A stock timing map will usually get you running nice and safe and you can bump up from there. Get a bin from a turbo buick or turbo trans am and copy that curve.

 

With the V6 MAF, you'll run out of room pretty fast and I think there is still a 150 g/sec limit in the ECM. Might be better to go to SD. You may even be able to use a 165 and V8 MAF, but I'm not sure if the firing rate can be set in the memcal for a V6.

 

I would suggest SD as well, for this application.

I would also suggest a 7749 with $59 code, or if you want a purely stock GM bin to start from $58.

A stock bin will get you started. If you want safe on the ignition side you can reduce all points in the timing map above approximatly 1000 to 1200 RPM by about 5 or 10 degrees and then add more in as you tune, and watch for knock counts.

 

That was my original plan; the harness repin looked fairly straightforeward, I can program it for map or maf and I'm pretty sure I can reset the firing rate. The only thing I don't like about the '165 (w/ $6E) is that the spark table only goes up to 4800rpm, but I guess it's pretty much the same for all obd1 ecu's.

I'd like to stick with a maf setup, but even the v8 maf's are limited to 255g/sec which I'll blow past at about 4250rpm, but I doubt I'll ever reach that below full throttle. PE tables can be used to tune above the maf limit so that's not a prob. I'll copy a turbo buick spark map and retard it a little to get started. Thanks for the help.

 

I would be reluctant to use SA tables from a (possibly) different engine. I say possibly because the engine type hasn't been posted. I would look to the stock tables for the engine is question. Then figure out at what LV8 the engine is typically in boost. And lower the SA in the tables from that point on.

If you would like to stay MAF, consider using the 1227148 ECM. This is what is used in the '89 TTA (and Buick GN). It was also used in a lot of non-boosted Buicks, so it is rather easy to get. And, it is specifiy a 6-cyl sequential injection setup. The sequential mode really helps with the larger injectors.

If you do switch to the '148, there is an calibration airflow value that is the threshold for boost. Once that airfow is reached the boost tables come into affect. It is a decent setup for a MAF based boosted engine.

RBob.

 

It's a twin turbo 2.8, should've mentioned that from the start. I was comparing the spark tables from a GN 3.8 and a TGP 3.1 and the TGP looks like a better fit. The '148 looks like a much better ecm too, I'll copy the spark tables for the GTP to the '148. What's the 'calibration airflow value' listed as in tunerpro?

 

The flow for boost threshold is at $457 in the calibration. For an XDF file name I have no idea what it will be. It is just that the name and inclusion is up to the person that created the XDF.

RBob.

 

Interesting, I'll have to look into this ECM as well, simply for the possiblity of SFI.

Is there an xdf for this ECM/bin?

 

I was going to ask if someone had the harness pinouts, maybe I'll browse around on a turbo buick site for that though.

 

That is the best place to go for info on the '148. There is a ton of stuff out there, hac's, calibration table data (xls), pin-outs, then patches and stuff. The GN folks being addicted to boost have made a lot of information available regarding the $31 mask.

RBob.

 

Those where the ECMs that used the frequency/period based MAFs rather then the voltage based ones, no? If so, Id use an LS1 MAF and frequency translator rather then the junk stock ones. Not only that, but you can use this as a way to trick the computer into seeing more then 255 g/sec of flow, which I assume is a limit in those ECMs as well. You may need this if your making over 275 HP with your setup. That, and the LS1 MAFs are light years ahead of the old stuff.

Just out of curiosity, how much effort is it to adapt the cam sensor with those? Is it just one of those ones that drops in place of the dist.?

 

So I assume the maf is ahead of the turbo on the 3.8's since it's a frequency type. That would make intallation a little simpler for me. I'll be making well over 275 hp, I'm going to wring as much out of it with a pair of thunderbird turbos as the bottom end (with forgings and nitriding) will handle.

 

The Buick engine used a distributor stub for the cam sensor. Then a wheel to drive the DIS. Both of which are optional on the '148 ECM. It can drive a distributor along with fire in batch mode w/o the cam signal.

RBob.
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The stock MAF in this case (pun) is plastic, and will 'blow-up' under boost. Going to a later model LT1 or LSx MAF allows it to be placed in front of the TB (they have aluminum housings).

RBob.