does the 305 tpi and the 305 tbi get the same gas mileage?

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Dan
100% stock 1990 RS 3.1L
and VERY slow

 

Overall a TPI will get better gas mileage than a TBI engine.

If you have a TPI 305 with a standard and a TBI 305 with a standard (both with same gears in rear and in tranny) the TPI should get better gas mileage. However, when my 88 305 TBI was stock and I had 3.08 gears I could get 19-20 with my foot in it most of the time. I even got as high as 30mpg on 2 different occasions. One was on the interstate at 70-80mph going to the mountains. It all depends on the gears, transmission, hp the engine has and even the body style of the f-body. The TA's tend to get better due to there better aerodynamics. If you put the exact same motor in a TA and a Camaro (same drivetrain also) the TA will tend to run up to 5mph faster on top end.



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1988 TA 300+hp 350 w/ TBI and Holley TB unit, Holley projection intake,
WC T-5, 3.42 gears w/ Auburn posi. MSD 6A, edelbrock TES headers, dynomax 3" cat and cat-back system, ACCEL coil, polyurethane bushings all around, aluminum driveshaft, Mr. Gasket open air cleaner.

1993 S-10 w/ 4.3L V6 TBI, slightly bigger cam, Mild polish job and 3 angle valve job on heads, Edlebrock TES headers, Dynomax cat back, MSD 6A, ADS chip

2000 Kawasaki KX 125

 

Stock, I belive the 305 tbi makes 17/26mpg and the 305 tpi got 17/24mpg according to cars.com Personally I get 18mpg city and I don't know highway. I think its because of the wires,plugs,headers,cat,spacer. But the gears aren't helping me so thats probably why its only 1.5 gallons above stock.

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Eric Natzke
91 Firebird 305 TBI (dropping in a 355 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-Accel Cap & Rotor
-Rapidfire Plugs-Pablo's Free Mods-265/50/R15 Tires-Emmison's all Gone

http://hometown.aol.com/J007Golden/index2.html

 

With the following mods I get 19.8 mpg on average from week to week.
Edelbrock Performer TBI intake and TES 6872 headers
No cat
SLP catback
Jet stage 2 chip
180 degree thermostat
TCI shift kit
84 T/A cold air induction with K&N filter
Richmond 3.73 gears
Since the rest is chassis/suspension I'll leave that for another post


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Mongoose-NCTGA-1990 Pontiac Formula/305 TBI-700R4 with Edelbrock Performer TBI intake,TES headers,and STB,K&N,MSD-6AL,Holley laser shot coil,Accel Extreme 9000 wires,Jet Stage 2 chip,TCI shift kit with corvette servo,Richmond 3.73 gear with Auburn 3 series posi,no cat,SLP 3" cat back,Eibach sportline springs,Energy Suspension poly throughout,Lakewood LCA and adjustable panhard bar package,SSM subframe connectors,IROC wonder bar,Tokico 5 way adjustable struts and shocks,Autometer electric fuel pressure gauge,Alpine,JL Audio,MB Quart,92 GTA taillights,92 GTA aero wing and hatch,Steve Spohn LCA relocater kit,MacEwen White face gauges,84 T/A cold air induction air cleaner.

 

thanks guys

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Dan
100% stock 1990 RS 3.1L
and VERY slow

 

Remember our tank is a 15.5 gallon tank when doing your calculations.

When I first got mine from 3/4 tank (10.85) I got 246 miles on a trip to NJ. That comes out to 22.7mpg

Now that I fixed this and replaced that from 1/2 tank (7.75) I got 250 miles. That comes out to 32.3mpg.

It's amazing what a 3.08 rear and a .63 overdrive can do.

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1989 Camaro RS LO3 WCT5
http://350.StreetRacing.org
ICQ: 61342629 AOL IM: BlackSunshineZ28

 

I agree and most people will never believe you about the gas mileage we can get with the 305 TBI engines. I think the TPI's get worse b/c of the increase in hp over our TBI engines and the gears are normally lower.

TBI is easier to work on but I love the looks of a TPI.



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1988 TA 300+hp 350 w/ TBI and Holley TB unit, Holley projection intake,
WC T-5, 3.42 gears w/ Auburn posi. MSD 6A, edelbrock TES headers, dynomax 3" cat and cat-back system, ACCEL coil, polyurethane bushings all around, aluminum driveshaft, Mr. Gasket open air cleaner.

1993 S-10 w/ 4.3L V6 TBI, slightly bigger cam, Mild polish job and 3 angle valve job on heads, Edlebrock TES headers, Dynomax cat back, MSD 6A, ADS chip

2000 Kawasaki KX 125

 

badbird, you are so right. when my 3.1L craps out i want to get a 305/5 speed but i don't know wheather to go simple(tbi) or complex(tpi).



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Dan
100% stock 1990 RS 3.1L
and VERY slow

 

GB, I wouldnt go by that calculation thats very innacurate, the gas gauge is not linear at all, and I would say, the F mark represents only about 2/3 of actual fuel tank capacity

the best way to calculate mpg is to fill your tank till the gas pump clicks indicating its full
then reset your trip odometer
drive around till the gas gets low, write down the mileage, and write down how many gallons of gas it takes to fill the tank as before

 

Yeah the factory fuel gauge is pretty inaccurate.
FWIW I filled it to full at the pump before the 1/2 trip one. Then came to the pump and it was just on the 1/2 marker. I think it look about 6.5 gallons to bring it back to full again...
But 3/4 tank one was only close to full, but not totally full plus I was beating on it that day since I ran it at Atco.


Since we're talking about gas etc. On my last Camaro when it got bellow 1/4 around turns it would fuel starve around 90* turns. Yet with my RS I was almost exactly at E and took the same exact turns without any fuel starving. Now I know only LE1's got baffled tanks so what's up with this?

[This message has been edited by Get Blown ? (edited October 06, 2000).]

 

Hey, guys! What's wrong with the way TBI looks??? OEM is pretty week for sure, but I just bolted up a TBI unit to my Holley Strip Dominator on the floor of the shop (w/adapter, of curse). There's pretty much no way that doesn't look good! Gonna start programming when someone finds me a 2" Rochester OEM TBI unit. Looks good on the floor, though!!!

 

back from vacation...

I think they look good also, I was just saying I would love to have a TPI under my hood instead of a TBI sometimes. I'll probably think differently when I have a problem with the TPI though !