secondary removal how do you go......

[Maxlean]

Originally Posted by tpepmeie

There is nothing in the program to limit block learn cells when the port throttles are open. Whether PT open or not should have not effect on the block learn function.

Open port throttles does not mean power enrichment is active.

Todd

I'm gonna have to beg to differ. When driving around with the pt commanded open (setting them at a very low value) I would only use cells 16 17 and 18 (or something like that, I'd have to check my logs). When the pt were commanded closed, all cells were available (EXCEPT 18). I suspected that when the pt's are commanded open, the ecm assumes power mode (but not necessarily pe) and therefore really only needs one cell for that mode of operation. In other words cell 18 is dedicated to pt open mode (still closed loop), just as cell 16 is idle and 17 is decel. (disclaimer: the actual cell numbers may be different than these, memory ain't what it used to be!)
Scott

[tpepmeie]

Scott,
You are free to differ if you want. I have the source code. What model year, and I will review the code again tonight to be sure.

[threestar40]

This is a re post from 5/06 on that other site...the reason I still have my secondaries...and I hate extra complicated equipment as well, so I own a ZR1 I did do coil overs with an FX3 delete though...so I got that going for me.

When I read lingenfelters book on modifying small block chevy's, he talked a lot about intake velocity.

At the lower RPMs, smaller passages=more intake velocity thus making more power and torque and at the higher RPM's you want more volumetric area as the motor is pulling all the air it can and intake velocity for cylinder filling is not as much an issue.

I thought that was the idea behind how our stock throttle bodies' work as well. Have ya'll looked at how small that little primary butterfly is?

It's tiny...I think we need to keep our eye on the ball here.

Let me quote John.

"Intake runner length is one of the critical decisions in engine building since it contributes significantly to the shape of the power curve"

"Condensing this very complex subject down to it's basic concepts, increasing runner length tends to improve torque at the lower RPM levels while simultaneously lowering the peak torque RPM point"

Now I realize that he is speaking about a different motor, but there is knowledge to be gained here.

"The other half of the intake manifold design process, cross-sectional area of the port, also plays an important role. Generally a smaller runner area increases intake charge velocity, speeding up the inlet charge, which improves cylinder filling at lower RPM levels. Conversely, huge intake manifold port runners contribute to slowing the intake gas speed at lower RPM levels, hurting power below peak torque while contributing to improved cylinder filling at RPM levels closer to peak horsepower."

One more thing which I feel is a jewel should be mentioned here.

On a section titled "manifold destinies" (Love it, Every ZR1 owner should albeit bittersweet)

"As you can see, there are several intake tuning factors that remain constant...Intake runner size is perhaps the most important. Small runners generate great low speed torque but tend to limit top end power. Runners that are too large will be lazy at street engine speeds and contribute to exhaust dilution/reversion in the intake. Short length runners tend to emphasize top-end power while longer runners tend to increase mid-range torque at some sacrifice of top-end RPM power potential. This is about as concise as you can get yet there are plenty of questions still to be answered. The future of induction tuning will address all of these factors plus a dozen more." NOW THIS IS TH IMPORTANT PART. PAY ATTENTION "How about a variable-length, variable-diameter intake that could be long and small for good low-end power and short and fat for top end power? If that sounds too much like Buck Rogers, it's already happenend in Formula 1. Perhaps some enterprising Hot Rodder will someday build as practical and affordable and intake for the small block Chevy! Think about it."

The bastards should have designed it better so it doesn't break all the time.

Eyes on the ball.

Rick

[XfireZ51]

Originally Posted by Maxlean

I'm gonna have to beg to differ. When driving around with the pt commanded open (setting them at a very low value) I would only use cells 16 17 and 18 (or something like that, I'd have to check my logs). When the pt were commanded closed, all cells were available (EXCEPT 18). I suspected that when the pt's are commanded open, the ecm assumes power mode (but not necessarily pe) and therefore really only needs one cell for that mode of operation. In other words cell 18 is dedicated to pt open mode (still closed loop), just as cell 16 is idle and 17 is decel. (disclaimer: the actual cell numbers may be different than these, memory ain't what it used to be!)
Scott

Scott,

I have to agree with Todd. PT Open doesn't automatically mean the ECM is in PE mode. Several other parameters that define PE.

Rick,

What's the image you posted?

[threestar40]

Those images were just smilies from the other forum...I just cut and pasted.

Sorry.

It wasn't anything exciting.

Rick

[tomtom72]

I would just like to thank all of you guys for this disscussion.....I'm learning, and that's great.

Rick, thank you for reminding me to remember stuff I kind of "got" back in the early 70's.....on my LT-1 motor. This is just an observation from the peanut gallery...it seems to me that Mr. Lingenfelter was sort of describing the intake system on a LT5???


Tom

[Maxlean]

Originally Posted by XfireZ51

Scott,

I have to agree with Todd. PT Open doesn't automatically mean the ECM is in PE mode. Several other parameters that define PE.

Rick,

What's the image you posted?

Hold on. I'm not saying that it's pe mode at all. I'm saying that cell 18 is dedicated to pt open mode (still closed loop), just as there are other specialized cells such as 16 for idle mode and 17 for decel mode. While datalogging with the pt open, I was only using cell 18 durring normal driving. Durring decel 17 was used and at idle 16 was used. Setting it for normal opperation (pt closed durring normal driving), all the remaing cells were now being used. Try it yourself. BTW, this is '90 with the prom being based on the latest factory release.
Scott

[tpepmeie]

Do you have a copy of that datalog you could send me? Which diagnostic software?

I've looked again through the entire 90 source code (& others). No link whatsoever that I can find between the PT Open bit and the BLM cell. I have never, ever seen BL cell 18 in any of my logs. It is only a 16-byte table.

Todd

[Maxlean]

I'm using TTS Datamaster to log. I've got one I could email too you if your interested.
Scott

[tpepmeie]

All,
I have found the relevant section of code. It does not exist in all calibrations, and I had overlooked it before. Will write more later. Learned something new today....

Todd