FiReBReTHa

k, well.
i have a 91 pont firebird 305 V-8 with TBI
and everyone speaks highly of TPI. i would like to changeover. but im new to fuel injection. so any info you guys can give. is highly appreciated. like whats needed. how hard, long, difficult, complicatsions. whats already there. thanx guys.

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91 FireBird 305 V-8
no true mods,
ghetto rigged cold air intake,
People dont have a soul, its just something parents made up to frighten little children, like the boogie man, or micheal jackson..."

GheTTo Riggers INC.
We Make Mcgyver look Like Crap

Vader

Fire,

Before you dive in head over heels into the TPI world, do a little research on the shortcomings of the system. TPI engines make great torque at low RPMs. The GM Powertrain guys wanted a torque engine for the heavy cars, and that's exactly what they succeeded in making. You can't dispute the low RPM torque advantages of the TPI over the other stock systems.

However, many TPI drivers would like to be able to exceed 4,500 RPM while still making the torque they get at 3,200 RPM. This is a pretty tough chore for the long-legged TPI. If you want a car that smokes the tires with a 2.73 rear gear ratio, TPI will fill the bill. If you want a screamer for 1,320-foot runs, you might want to find a different method.

The "lowly" TBI that you are so quick to sheepishly defend can provide some very good flows at higher RPMS - much better than the TPI. You can save the money you were holding for a used TPI, ECM, and all the goodies, and spend it on a torque converter or rear gears, a larger fuel pump, and some plumbing and linkages. Then trash your original TBI intake and install a twin- or triple-carb intake (like an Offenhauser Tri-Power or Weiand dual-quad manifold with 2bbl adapter plates). Mount two or three TBI 220s (your choice), connect the throttle linkages together, and use only one of the TPS sensors and IAC stepper motors to feed the engine at idle. The engine will idle and report to the ECM just like it always did, and the ECM will be very happy firing four or six injectors instead of just two (the same ECM fires eight injectors on the TPI system). Add a custom PROM with a fatter fuel curve on the lower end, and you should be set to go hunting.

You can probably get "cores" for the supplemental TBI units from other guys who are changing to TPI, and fabricate the necessary plumbing and linkage. We "old farts" used to do this all the time for tri-power and dual-quad setups, so I know you can do it, too.

If you want to get really goofy at the upper end of RPM, you can convert a dual quad Torker manifold to TBI, then make power all the way to 7,500 RPM if the bottom end will take it. If 7,500 get boring, you can get a Victor Ram, shorter crank, and appropriate valve train to take you beyond five-digit RPMs. Two TBI 220s should provide more than enough high-RPM flow to smoke a lot of TPI cars by the time you hit the traps. With the right gearing and torque converter, you won't fall very far behind at the line, either.

TPI isn't the answer to everything, you know...

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Later,
Vader
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"What a Day..."
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FiReBReTHa

wow. must say thanx for the responsive, gave me some new info.

but its a daily driver as well. i wan thinking about a new fuel pump. but couldnt find anything for tbi.

FiReBReTHa

hmm.. found a whole tpi setup for 185.
""removed from an 87 Pontiac Trans Am GTA. It is pretty much complete except for the ecm and distributor. Manifold, Fuel rails with injectors and regulator, ports, plenum, wiring harness, intake hose, and fuel lines and hoses. It has been off the car for a few months but the gas in the lines was still clean. The harness is good from the computer plug to the unit but where it turns back into the firewall to the fuse box it is cut. I don't think that is very hard to splice in. The unit itself is relatively clean.""

Grim Reaper

The poor TBI system is so quickly dismissed and underrated, and it is a real pity. TBI has a lot of advantages and can be readily tuned to meet the performance needs of most people.

With its short intake design, similar to a carb, I see no reason that a TBI cannot be made to meet and exceed the performance of a good old fashion carb. And say what you will about carbs, when it comes to performance, they out perform TPI on the track. This is why so many guys dump their TPI system and switch to carb.

Talk to Pablo and Fastbroker about making a TBI system perform. Scope out the TBI board. If I was in your shoes, I would invest my money in the prom burning equipment and work with the TBI system. To make TPI perform, it costs far to much money IMO. In fact, many times when I start to price out the amount of money I must spend on my TPI system to make it perform, I seriously consider TBI.

As Rodney Dangerfield say "Gets no respect".

PETE

iTrader: (1)

Keep the tbi i have tpi and am just getting the rpms ii've been searching for it would be a lot easier for you.go with a throttle body off of a 454ss truck they flow very well and should be a bolt on you will need to upgrade your pump and chip for the extra cfm going into the engine though

Guest

I dont think thats complete, there seems to be something missing that may or may not be there, sensors+relays. Before you spend, make sure he has them all, those can add up quick.

branz28

Ya know, and i still don't understand how my 2000 Z28 makes all that power, i hear that their runners are 13" or so (i haven't exactly measured them). But as far as a TPI conversion goes...bah...stick with what you got and beef it up...cause you know when a stang or ***** pulls up and says "What you got under the hood?" and you say "305 TBI" (or 350 whatever it may be) then he laughs and decides to race...when you pull past him and watch his head lights all of sudden fade into the past is when you will start to say "Yea, it was worth sticking with TBI..." of course that stanger will be pissed so make sure you keep the windows up and a club in the back

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Gutted cat
-!AIR