What I'm saying is that the ported 99+ L67 TB...on top of all the other mods on the '98 LeSabre...gave me a calculated +17hp at 5200 rpm (it was actually more at higher rpm, but I'm only making comparisons at stock peak rpm points right now). I suspect that without things such as the ported LIM, et.al., the gain wouldn't have been as much. Also, to reiterate, these numbers have not yet been confirmed by a dyno.

What I primarily had to tune for was the 99+ MAF...I started from a base MAF table imported from a newer PCM .bin file; however, because of the TB porting, even that stock 99+ L67 MAF table was way off...so far off that the method PowrTuner teaches for re-calibrating the MAF wasn't enough, and I had to develop my own method.

#25 GM injectors

I think Casper used to have a FPR but I can't find it online. I know a few on this site use it or something similar.


Ed

Yeah Andrew, I've been running the 25# injectors for over a year now and they work great. So you think an L36 with an L67 TB might be close to correct fueling if you simply switch to 25# injectors? Sounds like it could work... how did you do the calculations to figure that out?

Across the entire MAF range from 2000-9000 Hz, the 97-98 L36 MAF table is a fairly consistent 21-25% lower g/sec air at a given Hz compared to the 99+ L67 MAF table.

Example: if my stock 98 L36 PCM reads 7500 Hz on its stock L36 TB/MAF (that'* about when PE kicks in at the stock setting), it'* sucking 84.22 g/sec air. If it reads the same Hz on a 99+ L67 MAF (in a stock, non-ported L67 TB), it still THINKS its sucking 84.22 g/sec air, but it'* REALLY sucking 102.04 g/sec air (21% more, "unmetered" air...this is where the extreme leanness caution comes from).
At 2000 Hz (about idle), that'* 2.96 g/sec L36 vs. 3.24 g/sec L67, or 24% lean; at 4000 Hz (typical highway cruise), that'* 15.27 g/sec L36 vs. 17.42 g/sec L67, or 25% lean.

(Now, port that L67 TB and the difference grows larger, as discussed below)

There is no way your stock L36 PCM can adjust fuel trims for this much leanness. However, if you were flowing 21-25% more fuel on the same length IPW (upon recalculating, I guess that'* actually 26-28 lb/hr injectors versus stock 22 lb/hr), you'd be "close enough" that your fuel trims could fix the difference. Is 25 lb/hr "close enough"? IDK :?

For reference, when I got done with the MAF table on the ported 99+ L67 TB, it was about 25-28% higher versus the 98 L36 table (as opposed to 21-25% for the stock L67 MAF table, as stated earlier). This difference (from the porting) was enough to peg the trims lean and throw the car into severe lean-out spasms at high rpm under WOT when trying to use the initially imported, stock L67 MAF table, so imagine what being 21-25% off would do; however, it also suggests that the L67 TB even without porting would have gotten me 75%+ of the gain I saw, and with alot less headache

One other thing about the porting; unless you are a CNC expert, every porting job is going to be different, and probably unpredictable in its result; thus I would certainly not suggest porting unless you have a Tuner or AFC device.

(Heck, I'm not necesarily suggesting anyone go stick an L67 TB on their L36...just throwing the idea out there :P )

Now, big_news_1, why did you put in 25 lb/hr injectors? Did you make any other changes (e.g., reduce fuel pressure) to get the A/F back in balance? If not, do you run rich all the time? I suppose your fuel trims might be able to adjust for those injectors...but surely they are high negatives most or all the time?

I switched to the 25# injectors when I did my cam, heads, and LIM. The engine was sucking quite a bit more air, and the LTFT was pegged lean. I used an AFC for a while with the stock injectors, but then I had a bit of injector trouble and switched to a used set of matched 25# injectors. They compensated a little too much for the fueling and made me too rich, but Intense fixed the problem when I went out there for my dyno tune in April 2006.

However, the whole time I've been doing mods I've had a stock L36 throttle body (which is still on the car). Who knows how much fuel adjustment I'll need when I finally install the L67 TB that Doug sent home with me in March? I think your studies have proven that the TB is a sizable restriction on a modded L36, so I need to switch mine out. My 25# injectors won't be enough to compensate for the TB with stock fuel tables because of my cam and porting, but hopefully with modified tables I'll be able to dial it in.

My car needs a massive amount of tuning... I just haven't been to see Thomas (PDXGTP) in a while. Our previous attempts have been shots in the dark to some extent, but hopefully we can get it dialed in. Andy, what would it take for you to do some tuning on my engine if I can make it out to San Diego for the tentative meet in August?

Boy do I need some tuning software of my own :?

This is very interesting.

I wonder if they reduced your fuel pressure...maybe all you have to do is increase it back to where it was (or higher)?

Is that L67 TB you have ported or modded? What year is it from?
BTW, what is your complete mod list? (use PM if it'* "Need to Know" only )

The PowrTuner has been opened up to include the '97 model year, so in theory, yes some tuning could be done; however, there'* only so much that can be done in a single day (or even a few days)...are we talking late August for the meet? I'm gonna PM you with more details on the tuning (and availability of my Tuner). BTW, do you have the 4T60 or 4T65E tranny?

Here'* my mod list:

-Reground stock cam with almost exact specs of ZZP GT1 (mine has a bit less lift)
-Hand ported heads shaved .040" (to make up for the material taken off the cam)
-LIM matched to heads
-UIM with stock length runners
-Stock '97 L36 throttle body
-Crappy (and I do mean CRAPPY) intake tube with K&N cone (no heatshield... yeah, it sucks)
-25# injectors
-Homemade ported exhaust manifolds
-Stock downpipe
-Magnaflow cat
-Straight shot 2.5" exhaust with Magnaflow resonator and Thrush glass pack
-Custom tuned computer (which isn't tuned for my current cam timing)
-4T60E tranny with upgraded clutches, rebuilt stock differential, 3.73 final drive, 2800 stall converter, and shift kit

When we installed the cam in November '05, we realized something had happened during the regrind that somehow retarded the cam timing when the stock timing marks were lined up. The car had power, but it was all up in the upper RPM range. So I bought a Rollmaster adjustable timing set and we advanced the cam timing 6 degrees from stock. This gave me an appreciable shift in the powerband to the lower RPMs, and this is the configuration that I had tuned at Intense to make 190whp.

Fast forward to January of this year when we installed the new tranny. Doug (MyLittleBlackBird... he built the tranny) suggested I retard the timing 6 degrees back to stock in order to offset the 3.73 gears and higher stall TC, so I did. This threw off the Intense tune, which Thomas and I tried to correct with his HP Tuners suite. We have never put much time into it, but he has a wideband O2 sensor we were going to use to tune my fuel trims really well. I have never gotten back to his place to do more tuning, and the car runs decently right now (15.05 in the 1/4 mile). Still, I'm sure it isn't as good as it could be because we've done very little tuning, and the PCM still isn't programmed to make the car shift quite right. If I do a bunch of tuning along with the addition of the L67 TB, I'm sure this thing will get into the 14s easily.

There.... I'm done

Damn. You give us L36 guys some hope! A L36 that runs better than a stock L67. Sweet.

OK, I have researched this further.
The idea of simply slapping an L67 TB/MAF on your L36 and "matching up" fueling with bigger injectors or higher fuel pressure is a bust...unless perhaps you are running 100+ octane race gas.

The reason is this: while you may be matching up A/F ratio by doing the above, you are still telling the PCM that you are filling the cylinders 20-25% less than you really are...this will cause the spark table lookup to hit the wrong cells, leading to erroneously high base spark advance being called, particularly at high rpm / high load. This will cause potentially catastrophic knock.

Now then, if some EE-minded person out there can develop a small, low-cost, frequency multiplier "dongle" to go between the MAF and the harness--something to increase the frequency the PCM reads by some 20-25%--the spark table issue would not be a problem, and this idea might work.