Mpfi upgrade reviews.

[L31MaxExpress]

A few months ago, this same topic was being discussed, so I specifically asked the question on the Acdelco site. I got the typical “Message Received” after hitting Send and it also said “Thank You, We Will Respond to You”. They seem to have ignored that particular question.

Does not surprise me because GM to my knowledge has not corrected any of the calibrations on these trucks for anything for years. Once they went out of warranty that was the end of GMs support and updates atleast with PCM tuning related issues. The only thing that would have required them to make any changes would have been something emissions related under the Federally mandated emissions warranty. Those emissions warranties are long expired and we are well past the designed life expectancy of these trucks now. So long story short GM does not care. If an old truck cannot pass smog, they don't care, buy a new one that can in their eyes.

 

[L31MaxExpress]

I saw a chart break down of the emissions stuff a while back that was written by GM in 1994. The Vortec trucks were only designed to meet the emissions requirements for like 70K miles and they predicted that 95% would have a 50% degredation from those design standards by 140K. At 140K miles GM predicted they would run too dirty to pass an actual emissions test and were thus considered at the end of life. Aka junk it and buy new. This was a writeup prepared for the EPA as well for part of the certification process for the 96 Vortec engines. As we now now some of these trucks just keep on going, I actually wonder how much emissions degredation a 350K mile truck has on it in real life.

 

[John DeWitt]

The newer style spider is actually 22.1 lb/hr in flow. The stock spider is 23.1 lbs/hr the PCM is calibrated to open the injectors based off that flow rating to deliver the correct amount of fuel. The newer style injectors also have a different amount of dead time. That is the time delay between the PCM sending voltage to the injector and the fuel actually starting to flow. That also makes a difference in the total volume of fuel injected. At lower rpm and load like idle a dead time calibration error can signifigantly throw off the fuel delivery. Then you throw E10 fuel into the mix. The system is still injecting 1 part fuel to 14.7 parts air although the new fuel has a stoichiometric air/fuel ratio of 1 part fuel to 14.1 parts air. When I read data with a scan tool my PCM was showing consistent fuel trims of +10-15%. That is close to setting lean fuel trim codes. When you hit that upper limit of adjustment the PCM can no longer add fuel for any real problem such as a small vacuum leak, weaker running fuel pump, plugging fuel filter that is causing reduced fuel pressure or a dirty MAF.

So....this may explain a things or 2 for me. Oh wise one, pray tell me....how does one obtain this proper elixir of fuel & air?

 

[L31MaxExpress]

So....this may explain a things or 2 for me. Oh wise one, pray tell me....how does one obtain this proper elixir of fuel & air?

Aftermarket PCM reprogram using the correct data. 96-97 is hard to find anyone that can tune it. 98+ is much easier.

 

[L31MaxExpress]

So....this may explain a things or 2 for me. Oh wise one, pray tell me....how does one obtain this proper elixir of fuel & air?

Seeing that you are in North Carolina from your profile, the most local guy I know that can tune a 1998+ GM EFI system is Alvin @ PCM of NC. He is in Mooresville, NC. He might be able to tune the 96-97 but do not know for sure.

 

[John DeWitt]

Aftermarket PCM reprogram using the correct data. 96-97 is hard to find anyone that can tune it. 98+ is much easier.

99 k1500 Suburban, so are we talking a performance shop that does custom tunes kinda thing or is this more/less complicated....as in, what should I specifically be looking for in terms of a location that can do this?
Also....thanks for bringing this attention yall.

 

[John DeWitt]

Seeing that you are in North Carolina from your profile, the most local guy I know that can tune a 1998+ GM EFI system is Alvin @ PCM of NC. He is in Mooresville, NC. He might be able to tune the 96-97 but do not know for sure.

Answered my question. I'm about 40min north of Mooresville. Thank you kindly sir!

 

[L31MaxExpress]

99 k1500 Suburban, so are we talking a performance shop that does custom tunes kinda thing or is this more/less complicated....as in, what should I specifically be looking for in terms of a location that can do this?
Also....thanks for bringing this attention yall.

Oh its a 99, contact Alvin @ PCM of NC. He is in Mooresville, NC.

 

[L31MaxExpress]

Answered my question. I'm about 40min north of Mooresville. Thank you kindly sir!

From chatting back in forth in the groups and having bought some stuff from his site Alvin seems like a good guy although I do not know him personally jusr from the various tuning circles over the years. If he cannot do it, I am sure he can tell you who can. But he frequents the HP Tuners boards making me believe he has HP Tuners. This HPT file I put together has the injector data from a stock tune file pull of a later 4.3L van that used these newer injectors from the factory.

Post in thread '12200411 PCM swap for 1996 to 2000 GMT400 trucks' https://www.gmt400.com/threads/12200411-pcm-swap-for-1996-to-2000-gmt400-trucks.9644/post-1391332

Alvin has a lot of tuning experience and well versed in SBC tunes. I bet a good tune from him would make that suburban get up and go and probably help the fuel mileage too. Definitely would clean up the way it runs compared to the factory tuning.

 

[98_SLE_98]

Yeah, because in SI for psb #00-06-04-003B which covers installation of the mpfi unit after unsuccessful cleaning. There is no mention of programming required neither in the listing in the GM parts catalogue which for that matter only shows the mpfi unit and no listing anymore for the original poppet injectors. Being in this for so many years, in the last couple of years you really see the "planned obsolescence" so obvious for vehicles. Newer VIP and Global A to a certain extend system makes for a great difficulty down the road when you can't get one of many replacement modules due to being discontinued, lifetime back order and can't swap modules between vehicles, i.e. put in a used one and program it