My motor is a 421 CID and uses a lot of air so I've had to increase the scalars in tables 1 thru 3. All's well in tables 2 & 3, but I have a question about table 1. The stock ARAP bin shows point #2 at 3.23 GPS (see pic) and there's no way in heck I can use that point and maintain any kind of linear graph, so I've bumped it up to 4.31 and think I'm gonna have to go a bit more before it's over......maybe closer to 5 GPS.

That got me to thinking.....I don't know that I've ever seen my motor use that small amount of airflow.....are the first 3 or 4 points in that table only used for starting the motor? And if so, am I going to need to keep this in consideration if I experience a longer cranking time? In previous tunes I've always addressed long crank times in the Crank Fuel PW Multiplier table.

Thanks for any input!

 

Bueller?

 

...Frye...Frye?

As you have already pointed out, anything in the sub-12 gm/sec range is likely to be less flow than your 421 will ever see in normal running at idle (unless the sensor signal is shorted to ground, or the sensor is unpowered due to a bad relay, etc). I'd be tempted to just flatten it below 0.91 volts.

This should ensure that you should have enough fuel to keep it running if the signal is compromised and may provide some anti-stall protection.

During crank, you're likely to see 23 gm/sec, so this should not be a concern. (limited by the max maf flow vs rpm table point at 0 rpm), since the MAF signal is typically still being pulled up to 5 volts during crank and is being limited vs rpm.

 

Anyone? Anyone? Great movie......I still laugh like heck whenever I watch it!

Thanks for the input, this should give me a lot of freedom and maybe even keep me from having to bump the scalar up another notch. I'll play with these lower points and see what happens........thanx tequilaboy!

I wonder what the General's theory was in putting them there in the first place........?

 

IIRC, the cranking fuel is all PW based. Doesn't use the MAF until the engine is running.

Unless the MAF was modified the stock ARAP tables are decent. You will probably need to change the small PW and PW vs battery tables for the non-stock injectors. This makes a lot of difference in the idle and small PW areas.

RBob.

 

Thx for the add'l info RBob, I'll need to search those tables......man there's a lot to learn!

 

I'm normally one of the guys that defends MAF tuning. I'm running MAF on my 383 and it works well. But I gotta say, for an engine that large, I'm surprised you're sticking with it. That rascal has to be maxing out the MAF at or below 3000rpm leaving you very little resolution for a seemingly large part of your rpm range in PE. Also the fact that the engine is sucking through that one sensor has to be a restriction on an engine that big. Let us know how it runs and what power you're making. That is the largest engine running a thirdgen MAF I've ever heard of.

 

I know what you mean, but this is a smog legal build and I don't want to push the envelope or hassle it. The car actually ran pretty good on a previous tune.....dyno'd over 500 RWTQ & 385 RWHP but now I want to play with it and learn on my own if I can. I built it for torque anyway just so I could keep it legal, but it's a lot of fun stop lite to stop lite.

Thanks 1MeanZ!