Hey dudes

I was wondering...

Is the TBI better than the TPI or whats teh deal here?
I thought more HP on a TBI while on a TPI more fuel effeicant.
??
correcto?

 

If you plan on keeping the 305 for a while, a TPI would be a good idea. If you plan on bigger than 305, TBI is VERY affordable to get pretty damn fast.

 

and TBI is actually the one that traditionally gets better mileage. tbi creates its torque at a much lower rpm that tpi, tpi will have a higher peak torque but usually a lower average torque across the entire power band.
tbiis cheap as hell to make quick. if you do a few simple mods a lot of people will think you have a tpi 305 and if you do more work people will think you have a 350. hehe

later
tim

 

If you're interested in buying a complete TPI, I have one for sale. Email me.

 

TPI is better than TBI, thats why GM made TPI the high performance option in Corvettes and F-Bodies.
My dad converted his stock TBI RS over to a stock TPI intake, and gained 17 horsepower and 70 torque at the rear wheels. Then he put in an LT1 cam, and gained another 12 horsepower at the wheels. His best 1/4 mile ET is 14.94 @ 92 MPH. Thats faster than the local TBI's that have headers, open element air cleaner, and cat-back exhaust! My dad's car is all stock parts! Lastly, his best MPG was 25-28 using TBI. Now he's getting 28-32 MPG using TPI. Which do you think is better now?

 

To be fair, you've admitted that the his TBI was never tuned to ideal TBI conditions anyway, same timing for both.

 

Both dyno runs with TBI and TPI were made with stock proms, and stock timing. Then we started playing with the TPI chip after putting in the cam.

 

17 hp from a complete conversion adn 70ft/lbs of torque is interestign since a guy on another board posted his dyno numbers and he gained 12 and 40 respectively.
also, comparing a motor that was developed for torque to be used in ful sizes and trucks to a motor that was developed as a "performance" option is very misleading.
your "performance" car also came equiped with a posi and much better gears(most z's got 3.23's) which woudl explain more than half of the differnce betwen the 16.0 that a stock 305tbi(commonly delivered with 2.73 peg leg) can run and the 15.4 that a stock 305tpi can run.
and what does "all stock parts" mean? an LT1 cam is hardly a stock part on a thirdgen. and a 14.92 is hardly impressive since i ran a dozen 15.0's when i still had a stock intake adn only ultimate tbi and a posi with 3.54 gears.
doesn't seem liek your dad's big gains add up to a whole bunch dude.
if you are gonna go for all out maximum power on any motor you are gonna need port injection and a fully programable timing and fuel computer(DFI). but if you wanna make respectable power on the cheap and easy you are gonna wanna keep the TBI on the car.

later
tim

 

I would like to convert to TPI, but it is SO SO SO much more expensive. Let's say, if you want to improve your air intake on you TBI car, just get an open element air cleaner ($30), do the ultimate TBI mods (FREE!), and buy an Edelbrock TBI intake ($200 or so) and thats it! You've improved it alot and spent less than $300. But if you want your TPI to take in more air, you have to buy the intake base ($400), intake runners (another $400), you might want to port the plenum ($not sure, but it aint cheap), and then you'll need to buy a new throttle body or all that other stuff you bought will be suffering trying to pull air into the stock unit. You, at this point, have already spent over $1000 on your intake system! TPI is nice, but it comes at a price. That's why I'm sticking with TBI. If you really want power, swap over your existing TBI stuff to a 350! It's still cheaper than modding a TPI system.

 

HAVE to? Since when? Have a 350, still have the stock runners, base, hell it was even running an unported plenum with stock TB and no airfoil and with crappy weather (over 100 degrees), no traction, and a bad driver the car ran a 14.2@98. EDIT:The car also weighs 3600+lbs. Corrected it was high 13's@102 IIRC. The car keeps up with new LS1's on the street just fine, showed the taillights to a brand new corvette with it. I dunno where this HAVE to stuff comes from, but its misconception IMO. Since then I siamesed the manifold and uncorked a whole bunch of power, and all that cost me was some time. So far, the TPI itself has been the least expensive part of the engine build by far.

And before Tim squabbles about poor ET's, the car isnt 100% tuned like yours, its about 70% at best and the suspension was so bad on that run its not funny. Due to it being lowered, the suspension was actually removing weight from the rear tires under acceleration. I was actually next to the car on that run and the tires were just starting to grab halfway between the 330 and 1/8 mark. Just imagine what it will do if its setup right someday...

TPI sucks.