In my L36 modification threads, I’ve been making some estimates of torque and hp increases based on increased volumetric efficiency (VE):
http://www.bonnevilleclub.com/forum/...ic.php?t=72094
http://www.bonnevilleclub.com/forum/...ic.php?t=77479
http://www.bonnevilleclub.com/forum/...ic.php?t=77710

My VE numbers have been coming from the VE table in the PCM, after tuning for each mod with the PowrTuner. For awhile now—ever since these values started to exceed 1.00 (i.e., 100%) by a large margin—I’ve been thinking to myself, “these VE numbers just can’t be real.”

Well, they’re not. It turns out that the VE numbers in the PCM VE table are not “true” VE, nor “approximate” VE, nor, after a lot of analysis on my part, do I find that they are even directly proportional to actual VE in any predictable way. Ultimately, I do not know (nor does anyone at the tuner support site, apparently) exactly what these PCM VE numbers are. At best, I now consider them little more than a “marker,” in that increased VE in the PCM table (generally) means increased actual VE.

Anyway, to make a long story short(er), I went back through all my MAF-enabled scans at each mod level, and calculated VE the “old-fashioned” way:
http://www.installuniversity.com/ins...n_9.012000.htm

So, here’* the real—and much more defensible—story on VE versus my mods:


These VE values are much more within the "realm of possibility" than previously reported numbers; however, they do confirm that there have been improvements over stock throughout the entire rpm band above 2400 rpm—at least with the PLIM and PEM. (Not so much with the L67 TB…though I do notice improved throttle response with the TB, I have been unable to demonstrate it through any data analysis thus far; in any case, it doesn’t appear to be hurting me any, and may yet be helpful at future mod levels).

So what’* this mean as regards torque and horsepower increase? Well, to make an even longer story short: everyone knows that horsepower can be derived from torque; however, less well known is that torque is directly proportional to actual VE. So, assuming I haven’t made any significant changes in thermal efficiency or to the rpm of peak torque during my mods, here’* what I’m now calling as far as calculated incremental increases at each mod level:

Mod Level---Torque (@4200rpm)---HP (@5200 rpm)
Stock-----------+0 ft-lb--------------------+0 hp
PLIM------------+10 ft-lb-------------------+8 hp
PEM-------------+6 ft-lb--------------------+5 hp
L67TB----------+0 ft-lb--------------------+2 hp

For a total of about +16 ft-lb @4200 rpm and +15 hp @5200 rpm over stock.

This is a far cry from the more than 25-30+ hp I was calculating based on PCM VE table numbers, though still, to my mind, worth the $150 or so I spent on hard parts to get there. Sorry if I got everyone all worked up, but you know what they say about statistics and damn lies :o

On the bright side, if these measly 15 hp are making my “butt dyno” take notice, I can’t wait to see what rockers are gonna feel like

15hp for only $150 is quite the bang for your buck. That'* 15 easy hp all L36s here could pick up pretty quickly.

Ed

After your previous estimations, I was wondering if your car would actually dyno anywhere near those numbers. Good to see you were able to identify the error and recalculate more realistic numbers. 15hp sounds appropriate for the mods you've done, and makes me feel like less of a chump with my cam .

Still, keep up the good work! We all appreciate the R&D. I definitely bookmarked your VE link from above

If you really want to go cheap, assuming you already have a dremel tool, PLIM and PEM could be done for anywhere from near zero dollars (by modding the stock parts you already have--IF you've got a spare car to drive around for a few days AND really big cojones ) to however much it takes to get some stock spare parts shipped to you (LIM'* and EM'* are relatively cheap, and you could re-sell your old parts).

I forgot to mention: in the future, all VE numbers I report as they pertain to performance improvement, etc., will be calculated as in the link.

PEM'* with a dremel?

Good luck.

The VE table is a lookup table used as a MAF table modifier value and is also referenced in transitional fueling conditions.

Cheers,

Hey, so it'* like the n/a version of the */c die grinder...but don't be hatin' on the dremel

The dremel and some carbide cutting bits and silicon carbide grinding bits is what I used on my EM, and what I plan to use for some very minor porting on my spare heads.

That is a fancy way of calling the VE values in the PCM table a "marker" or "indicator," but I still don't know if there is any direct, consistent, mathematical relationship between "PCM VE" and actual VE.