I was wondering what is Tuned Port Injection? They have that technology on the 305 and 350 Camaro's of 80's and early 90's. i was wondering what the diff. between TPI and a regular 305 or 350 of its time. Thanks

 

a computer and a few more HP. sick

 

TPI gets its name from the equal lenght runners on the intake manifold. Supposedly they were the proper lenghth to create a ram effect at low RPM and increase low end torque. Each port has its own fuel injector, and the injectors are fired in batch mode, one bank at a time. Other engines used either carburators or TBI (Throttle body injectors). The TBI throttle body was similiar to a carburator's throttle body, and used a similiar intake manifold. Two or four large injectors dispensed fuel directly into the throttle body, but they also restricted the flow of air into the throttle body, which lowered the power output.

 

In reality, the real restriction there is the tiny inlets the TBI had to deal with. 1 11/16 of an inch does not allow for much airflow. But the whole setup was flawed, and really got a worse rep than it really should have, had it been milked for all it's worth.

 

If I upgrade to a 350 with tpi from a 305 with tbi what is the hp difference and will I need to add a computer mod

 

You're goping from like 170 HP's to about 245 HP's, if memory servres correct. Also, bumping up from 255 TQ to around 300 TQ.

You will need to "add a computer mod"... as in getting the computer and harness that goes with the TPI 350 you are theoretically (at this point) swapping in.

 

This to Z28 pete The injectors on a tpi do not go off as a batch per bank as stated, each injector gets an electrial signal from the computer and that is how the fuel is released to each cylinder when needed.

 

^ No sir the TPI's were bank fire, the LT1 and LS1 are individual fire

 

z28pete If you are ever next to a tpi that is running just listen to the injectors pop. You can hear them pop separately. You really need to read up injection. Find out why they put the injectors right above the intake valve and why a clean and balanced [each injector in a set of 8 releases the same amount fuel in the proper spray pattern to atomize the fuel for the best explosion]. The way you say it works would put a puddle of fuel on top of the valves. Just what part of engine operation do you think the computer does? And why do you think they moved the injectors from the center of the engine to putting them right above the valves.

 

Apparently you have never looked at the wiring from the PCM to the injectors on a TPI engine, or you don't know the difference between TPI (Tuned Port Injection) and SMFI (Sequential Multiport Fuel Injection). GM changed to timed, AKA sequential injection, on small blocks when the LT1 engine was introduced in the early 90's. All early injection systems, except for a few cases and diesels, were continuous flow such as Bosch CIS, or batch fire. All car companies eventually went to timed injection systems, similiar to the GM SMFI to get better pollution control & economy. Performance wise there is little difference from a properly set up system, wether it be timed injectors, batch fire, CIS, or carburator. I suggest you read your books more thoroughly, or take a factory course on engine & powertrain management systems.
Next time you look at a TPI engine attach a set of NOID lites & see how the injectors fire.