AdioSS

Would somebody compare and contrast the positives and negatives of the GM TBI system versus the GM TPI system? Thank you!

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~ Cheston Phillips ~ =Impalaitis ~ = tri9_SS
'96 BBB Impala SS "ADIOSS" & '91 white Caprice 'n0n 9c1' w/L03

Tas

ummm... TPI good for 305. Stock TPI bad for 350. mongo want bananna

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-Tas
'89 Formula WS-6

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

To be installed eventually far far far into the future: Yours if the price is right and I don't have to ship :
Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248), Catco 3" cat, and injector spacer.

Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options
AOL IM: superGRtaz

ZRATED

Yup that is exacly what I have heard. I am a tbi fan but I still think TPI still looks better and more mean under you hood!!

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One Tight Teal green 91 RS (my first car
All Rustangs suck!!!!
5.0 TBI with Auto trans
Z-28 wheels
K&n with dual snorkel intake
Tx Smog Pump Delete option
Valve cover breather
Rapid Fire plugs with Accel ignition wires,coil,cap and rotor
Flowtech headers with flowmaster and Half way cutout
B&M shift kit with trans cooler and hurst hotshift fulid
Hypertech thermomaster chip
96 LT1 cam with
New liffters and timing chain
All the free TBI mods

El Guapo

Both TBI and TPI are fuel injection.

Pros for TBI:
Simple to maintain
Easier to replace if needed
Cheaper to mod
More high end power potential

Cons for TBI:
Youre not guaranteed even distribution of fuel to all cylinders. During a sharp enough curve, you could reduce one side and enrichen the other momentarily.
Came stock on the lower output engines. (Not at fault itself, but it did give it a bad rap)


Pros for TPI:
Guaranteed even dist of fuel
Great low end torque
Came stock on higher output engines. (Through no doing of its own, it does mean that if you have an original TPI car, you have a better engine to start with.)
Lets just say it, coolness factor

Cons:
Expensive to mod
8 injectors (sometimes 9) to TBIs two or four
Limited top end in stock form (It dies at about 4500 IIRC)
A lot more can go wrong


Although the above was by no means an all inclusive list, l think l did hit the highspots. Im sure some will add to it.

Clayton

JPrevost

MAIN difference: TBI always speed density while TPI can be either MAF or speed density. This gives the TPI setups more freedom for small horsepower mods (not the speed density). TBI mods will need to either have fuel pressure tuned or a custom eprom with just simple mods like exhaust and intake! THAT is why TBI gets the bad wrap, it's not an EFI system that adapts well to free flow mods . This is why GM went back to MAF systems in all the new cars.
TBI is only good in stock form or mods with custom fuel curve!
I can't stress this point enough. You do mods, increase fuel with TBI!!!
TPI also has a faster baud speed (except in 85) so if you have a scanner like Diacom the data is logged faster and you can get some really good graphs, TBI is usually 160 baud on our cars (faster on the newer TBI trucks up until 95).
TPI is a great design because it's like having headers for your intake. Long small tubes = low torque and a velocity design. Short runner large tube = high end but that costs $$$.
TBI can use any carb intake and is a low fuel pressure EFI which is a good thing for reliabilty.
Since TBI can be bolted to just about any carb intake with a simple adaptor, it can be installed on vortec heads, single plane intakes for high end hp, just about any intake except a 2 barrel (who cares ).
TPI WAS designed for power but in stock form it works best with a 305. Even a mild 350 with stock TPI will probably be faster with a carb just because the TPI wasn't designed for the larger bore bigger displacement! The TBI WAS designed for both the 305 and the 350. It can be found on countless 350's so it's obviously easier to adapt but just like MAF systems, the injectors are in the way of air flow . You can see they are very different but nobody can say TPI doesn't look cool. I remember reading somewhere on the board that the TPI looked like a metalic spider humping your engine, lol.
A cool thing about TBI is that you can basically make a built engine look like a stock slow 305, hehe.

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, Jon (350 TBI!)
91 Red My website

pimpintheRS

i have seen this asked once every one or 2 mounths and you two that answered have given some good answers!!! probably broke it down the best...so jprevost when i put my cam intake and gears with posi should i ask someone to burn me a chip?

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....yeah my thirdgen.org name is gay but i've had it for a while.....

91 RS 5.0 TBI
14x3 open element.. i liked alot
160*stat... made my car run a lil cooler
msd coil and taylor wires ...not noticed
with ac delco plugs.. i like but not noticed
removed rear hood seal.. runs cooler i liked
accel cap and rotor..not a real mod
coming soon 3.42's with slp posi.. my first big mod!!!
lt1 cam shaft in the mail!! now 2 big mods to do!

Clarion cd player 2 planet audio 6x9's 2 tweeters and one MTX 10" sub in a bandpass all running off 2 separate 200w amps gotta love the f-body trunk, system hits!!!

Kevin91Z

iTrader: (1)

And if you asked this in the TPI forum, you'd see why there are a handful of 13 second TBI cars, and a buttload of 13 second and faster TPI cars.
That tells me which one makes the most power.

Here's a better comparison: My dad took his stock 305 TBI engine and put a stock TPI intake on it. He gained 17 horsepower and 70 torque at the rear wheels.

TBI is great for fuel economy, and reliability. But TPI is where the power is.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

V8Astro Captain

iTrader: (1)

Plus, TPI is a big pain in the a$$ to work on. I've had my fair share of messing with those goofy things. They liked to hide all the finicky stuff like EGR under the plenum so you would go crazy taking it on and off every three weeks.

On an application like mine where you can't get to all those stupid torx bolts from the side, TBI is a much better option.

And yes, I started burning PROM's and just a little bit more fuel made alot of difference.

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'92 Astro 350 TBI Edelbrock intake, MSD 6AL, 3.42's, 2.5" exhaust, Flowmaster 40 2 chamber, B&M 2nd stage shift kit, 255 60 R15 tires on AR-727's, Polished & Bored TBI, Custom EPROM in progress

Tas

There's only a handful of 13 second TBI cars because there was never a 350 under them from the factory like there was with TPI. Now that 305s are getting replaced, there are more all the time.

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-Tas
'89 Formula WS-6

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

To be installed eventually far far far into the future: Yours if the price is right and I don't have to ship :
Hooker 1-5/8" 50 state legal headers, Dynomax 3" I pipe (PN 44063 and 43248), Catco 3" cat, and injector spacer.

Super GRK_Taz World
F-Body Dual Exaust
EFI & Intake Options
AOL IM: superGRtaz

snflupigus

good think somebody asked this question, i dont think its ever been covered before.

please do searches.

[This message has been edited by snflupigus (edited September 22, 2001).]