Let me start by saying that i have a 98 k1500 383, with ported heads and intake, 30lbs injectors, long tubes,and a 500 lift cam. I have hptuners and I am trying to tune this myself but I am a novice when it comes to tuning. I have it running great under 30% throttle and less than 2500rmps but if goes any higher it instantly pulls timing & fuel. I have scoured the interwebs for information on the pcm is mapped but I can't find any useful info. I think there is a limit to the math the computer will allow. Can anyone with some experience with these computers chime in and help a rookie learn the ropes? I think I may be able to halve everything to keep the computer within it's limits but I am not sure what it's limits are. I am not even sure what units the VE tables are in, but i do know it's not a percentage. Any advice other than go to an online/local tuner or go carbureted would help tremendously thanks in advance. PS I am considering carbureting.

 

You've most likely exceeded the capabilities of the SFI injectors. I've never seen anybody use the stock fuel injection successfully on a stroker motor, let alone one with a big cam and good heads.

 

oh I forgot to mention it's multiport injection now. i ripped out that sfi junk. I am using the stealth ram intake and 30lbs injectors.
it's running in batch fire mode by default with a modified mechanical distributor so no cam sensor or sequential fire. I still have the ignition module hooked up so I can change the timing through the computer though.

 

I'm not familiar with that setup, nor do I know if it integrates well with HPT. Are you tuning the MAF and VE with a wideband?

 

yeah I am using a wideband

 

post up your tune. black box ecms have a limit on rpms and where you can tune it alot of guys do the 0411 swap go to efigearhead.com alot of L31 black box ecm guys there. and the ve table units are imperial units at least when i use tunercats on them

 

There is only a limit on the rev limit which is 6000rpm. You can tune anything naturally aspirated you wish with the blackbox.

Why not run a Vortec dist or at least a GM distributer that can read the cmp sensor?

peace
Hog

 

Why did you do away with the std vortec distributor.

The pcm is more than capable of controlling this combination. If you leave it mass air and 100% stock configuration and run it in SFI mode like it was from the factory it will run fine once tuned. The pcm will control your separate injectors just as it would if the SFI spider were intact. All the pcm needs is correct cam signal, crank signal IAT,ECT,TPS,O2S and IAC and it will run. Without correct inputs it's lost and will run like crap.

If this is your first attempt at tuning I highly suggest taking it to a shop to get it done and watch them. Stock vehicles with minor mods are the place to get your feet wet with tuning and then work your way up to this combo.

 

The most output using the stock CSFI on a 383 was 330rwhp/381 rwtq that I have seen with a dyno printout as confirmation. .

STock
-CSFI spider
-L31 intake manifold
-fuel pressure regulator
-truck fuel lines and filter
-stock L31 Vortec 350 t-body
-blackbox PCM (Fastchip calibration)
-stock Vortec 350 heads (home ported&polished)

Non-Stock
-LT headers
-exhaust
-K&N air intake
-LT4 hotcam kit
-Precision Industries "Vigilante" with a 3000rpm

All totaled make 330rwhp/381 rwtq.

Then added VMaxx plenum spacer with some other small trincketand ran a 13.1@ over 100mph with a 1.70 60ft time in an extended cab 2wd truck with 4.30:1 gears with M&H 390/40/17 drag radials. Which is decent for a GEN 1E Vortec engine.
The PCM calibration was a mail order tune, so he had a local guy to some touchups via Tunercats 2 as it was running a little rich.

I think the naturally aspirated rough max. power on stock CSFI parts is about 390-400hp at the crank. Less obviously with super or turbochargers as it takes more fuel per horsepower, so you will run out of injector at much less than N/A.

Even with high flow poppets like the Wester's Garage Black Widow poppets, the stock fuel system cant keep up at around 350rwhp, then an updated pump is necessary as the pressure begins to drop as the blown revs increase. The stock LT1 and Vortec 350 pumps are recommended for Ramjet 350(350hp-350cid), Ramjet 502(502hp) and Ramjet ZL1 (510hp 454).

peace
Hog

 

So I finally figured it out. The computer has a math ceiling similar to the 411's. I am not sure exactly where the ceiling is, but I cut all of my math in half and it's runs great now. As for the dizzy the stock one wouldn't fit with the stealth ram intake. I couldn't find a replacement with the hull sensor that sent the exact same signal. I did find some 400$+ potential distributor but I couldn't get any specific data on the signal that it would send and 30$ for a mechanical that will work just fine..... I couldn't resist. Also the computer defaults to batch fire mode which is what most of the gm car/trucks run anyway so turning off a sensor isn't going to kill the it or anything. Realistically with the rough tune I have in it now it runs very close to stock just a whole faster. I need to iron out a few small things around the shifts and start wot tuning. Thanks for all the info though.