safemode

iTrader: (1)

Are there any modications possible internal to a 305 or 350 tbi that allows for higher efficiency to the order of measurable and noticable performance gains without simply throwing more fuel into the engine? I haven't seen much focus on such modifications and that's kind of odd. It seems that most people and sites will tell you to do modifications that simply throw more air and fuel into the engine to increase performance, but without addressing efficiency issues and shortfalls, you are wasting an increasing amount of fuel and thus money. So does anyone have perhaps a list or place describing how to tune a 305 or 350 to suck the absolute most energy out of the fuel it's given before giving it more than stock quantities?

I was thinking, perhaps there are better pistons or different cams. Basically, a thread listing only those modifications that improve performance without needing more fuel to burn. I'm sure there is room for improving a 305/350 v8, and resorting to the old addage of simply adding more fuel to get better performance.

ShiftyCapone

iTrader: (7)

The more power you make the more fuel you will need. The power comes from the fuel in essence (chemical energy). However, the beauty of fuel injection is that at part throttle and cruise speeds you can achieve great fuel economy numbers. At cruise speeds an engine only needs roughly 30 to 60 hp to keep you going down the road at 65mph. Precise fuel delivery with a closed loop feed back system allow for this. So basically what I am getting at is tuning. A stock LO3 can basically have the same fuel economy as a 300hp 350 TBI.

safemode

iTrader: (1)

So you're saying the amount of power an engine, such as a 305 or 350, can make from a given amount of fuel is static. I dont believe that. What i'm getting at is that there is unused energy in the fuel consumed by these engines that is not unused in other engines and that there must be some ways of tapping into it ... technology or different/new ways of doing things that other engines take advantage of. Better / different pistons or different fuel injectors that diffuse the fuel better or something. This thread probably isn't going to lead to any actual products so much as ideas. Since there is obviously a newer generation of efi that solves many tbi problems and gains some of that untapped power.

I was really looking for ways to "bring the tbi to the next level" without simplying making it bigger so it can suck more fuel and air. Making a better tbi 305/350 without changing how much fuel comes through the injectors.

Dewey316

thats the problem. The potential energy of X amount fuel is only so much. Subtract all the things that take away from that (bearing friction, heat absorbed into the heads, etc) and you end up with the final output. The basis behind making power, is finding ways to get more fuel/air into the system. That is why turbo-charged engines have extra injectors, or a way to raise fuel pressure under boost, etc. Its all about getting more fuel/air into the system. The newer EFI systems, use things like resonance tuning, and tricks like that to get more air into the system, then open the injectors to match that.

Now things like vortec heads do make the combustion process slightly more effeciant, but you are still bound by the laws of physics. There is no getting around that.

Ronny

iTrader: (1)

our tbi system is archaic. a stepabove computer controled carb. i was able to improve the atomization of my fuel by removing the xram and going to a holley dedicated TBI manifold. TBI has a bunch of issues. the inj is above the butterfly spraying onto it. the spray hits the plenum floor most likely with any manifold. when the BF's open the pressure drops and fuel condenses on manifold runner walls. my set up is really bad in that i have no exhaust heat to intake at all. yesterday at 40degg cold start i could not drive it. until coolant temps hit 160. it is what it is. sequential port injection is a better idea?

ShiftyCapone

iTrader: (7)

The next step up as far as fuel injection efficiency goes has already been developed. LT1, LS1, LS2 etc etc. The reasons why it does not perfrom the same as said set-ups are for the reasons Ronny outlined.

steve8586iroc

There are ways to improve the efficiency of an engine without having to add more fuel. Head design is one, vortec heads are more efficient than stock heads both in flow and combustion chamber design. Also raising your compression will make your engine more efficient. Ignition timing is also important and tuning the chip to make all this work together is the most important thing of all. As was said in the previous post there are a lot of things that make an engine efficient. It all boils down to how well you can put to use the heat or potential heat that a given amount of fuel can produce.

Steve

JPrevost

Some notes on how to build a great TBI engine:
Tune your own chips.
Injectors spaced up a 1/4".
Higher fuel pressure (get a walbro fuel pump).
Intake that heat soaks or has a coolant passage to quickly get the fuel vaporized off of the walls of the plenum.
Small intake runner volume and high low-mid lift air flow numbers (like AFR 180 and 190s or vortec).
Awesome combustion chamber design with central spark plug and high quench (again, vortec and aftermarkets do this very well.)
Flat top or domed pistons that have a quench height of like 30 thou, check out http://www.speedomotive.com/Building%20Tips.htm
They talk about quench and why it's important.
Next is to have AWESOME exhaust flow. Our first gen motor design has terrible exhaust port flow characteristics. (vortec still have rather poor exhaust ports)
The ideal headers would be long tubes with 1 5/8" for <300hp, 1 3/4" for >300hp.
A true dual 2.5" exhaust with balance pipe (h-pipe) into straight through perf tube mufflers.
That's how you build an engine. The next thing is freeing up horsepower that's otherwise spent on accelerating heavy parts like steel driveshafts, heavy wheels, large TC and flywheels, heavy cranks and poor oil flow, windage inside the crankcase, elimating blowby with gapless wrings and/or a vacuum pump (they work, really they do).
See where I'm going with this.... how much do you want to spend and the moral of the story is simple. TBI is NOT as big of a problem with holding back horsepower as many people think. I consider TBI to be nothing more than 2 injectors above the throttle body. The stock computer code and tuning leave a LOT to be desired. This is where you'll see the biggest gains in performance.

BMmonteSS

The effect of adding headers, intakes, and other mods of that sort is increased power across the power band. Your just freeing up power that was being wasted trying to force air through those restrictive passages. So in reality your engine is already making that power. Once it's freed up you can use it. If you have 20 more ft/lb of torque at 2000 rpm, you'll be able to cruise at the same speed with your foot much further out ot of the gas, which does wounders for fuel economy. A side effect of freeing up those restrictions is that you usually have to add more fuel to compensate. Power and efficiency is in giving the engine the precise amount of fuel it needs to completly burn the air it's pumping into it. You can't just throw fuel at the engine and make power. In fact most factory tunes are rich at WOT.

safemode

iTrader: (1)

increasing compression means i'll be using higher octane gas right? I have no problem with that just wondering if it was increasing compression or decreasing that required it.

Everyone i've talked to and read online says that all things equal, a single exhaust will perform better than dual exhaust. Especially if you're running two cats along with those two mufflers. It looks cool, but it's just not worth the added weight.

I was under the impression that long tube headers wouldn't fit in our cars unless there was subframe modifications. That we were stuck with shorties unless we wanted to do some major chassis work.

To get rid of gas condensing on the walls, I wonder if anyone has tried using 4 smaller injectors crammed near the pod. This would allow a finer misting of the fuel while still delivering the same volume in the same amount of time. I dont think you'd need to alter anything electronically just splice the fuel and wires and the 4 will act like 2. just an idea.

Dewey316

increased compression 'can' require higher octane fuel. But with the conservative timing, and compression in the LO3, i don't think you would be stuck with high octane, if you bumped it a bit.

What it really comes down to, is the dynamic compression, the static number is not all that important. you can run 14:1 compression, if you have a large enough cam, to keep the dynamic compression around 8:1