jp0863
1/2 ton status
Looking at having to rebuild the tbi unit and new injectors. Was contemplating a bored out tbi unit, new injectors, etc... But on a stock motor, is it worth it? Any power gains? Seems like 470cfm is rather small for a 350.
CK5
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Bored tbi on stock motor?
- Thread starter jp0863
- Start date
No use in a bored TBI unit unless you have a bored intake manifold as well.
jp0863
1/2 ton status
So lets say I add an edelbrock manifold or bore the openings in the stock manifold, what kind of gains can I expect. I would like to do what I can without having to "need" a burned chip. I still need it to pass a smog test, so i'm looking to keep it fairly stock, but add power where I can without going overboard...
Or should I just keep it stock to avoid any emission hassles
Or should I just keep it stock to avoid any emission hassles
My opinion is, if it works, and you don't NEED to make mods, don't. Almost always lead to problems.
Mark will probably chime in, but TBI works off of volumetric efficiency. ANY change in airflow to the engine changes VE, which skews the calculations the TBI uses to fuel the motor, which would most certainly affects how it runs, and most likely emissions as well. Obviously though, the amount of the effect and how well the converter mitigates some of those issues is a variable.
My take is, if you make a modification that doesn't respond better with a chip modified to take the most advantage of it, the modification was worthless.
Mark will probably chime in, but TBI works off of volumetric efficiency. ANY change in airflow to the engine changes VE, which skews the calculations the TBI uses to fuel the motor, which would most certainly affects how it runs, and most likely emissions as well. Obviously though, the amount of the effect and how well the converter mitigates some of those issues is a variable.
My take is, if you make a modification that doesn't respond better with a chip modified to take the most advantage of it, the modification was worthless.
For the money not much? It will all be a WOT high RPM, right where this motor dies! Now if you changed cam, heads, headers and exhaust, the extra airflow would help a bunch at WOT.
And all parts used need to be CARB certified or you fail emmissions even if emmissions pass...
Bored Throttle body and intake or intake change with adapter or spacer changes amount of air available over stock and needs more AE (Accelerator Enrichement) to compensate, without it = bog or slow response, with more AE = snappy throttle and quick response.
With all the BS mail order snake oil chips for sale I can't blame guys for not wanting to do chips! But if you do engine mods without adjusting the chip it's a waste of time.
2 weeks ago I raced a guy who swore he picked up 100 HP with ultimate TBI mods, salad bowl, adjustable regulater to 15 PSI, long tube headers and true dual exhaust on a 1990 Chevy truck against my stock 1990 Suburban (except chip) both rigs had 3;73 gears, 5.7L engine and auto trans I beat him by 5 car lengths! Man was he pissed!
After a tune he beat me by 5 car lengths!
WOT on wideband O2 sensor was 10 to 1 AFR with mods and fuel pressure? How does that help? Stock is usually to low to keep cat cool anyway. When done we had it dialed in to 12.6 AFR WOT.
After tune his MPG were the same? 10 MPG? I asked how much time skinny pedal was on the floor? He said a lot! So next tank he drove nice for fuel economy and was at 16 MPG! He was getting 13 before the mods... 10 MPG after mods and 16 MPG after tune! This was without Lean Cruise enabled. I get 18 to 19 with it.
