Turbo

[THA_BAD_ONE-0]

This is what I was thinking but I am confused about a couple of things. I have a 4.3l TBI with a 700r4. I’ve got CPI heads and am getting the Holley intake The Holley part # is 300-79. I am going to turbo charge it. I need to know what the best way to fuel it. Because it is TBI, and I don’t have that providing the fuel I need to turbo it. Far .as I know I will need a computer also to control boost. If I get some runners drilled then what will control the injectors. What computer is needed and how much is this going to cost. Also what injectors will I need? I want to have all the main parts before I tear this thing apart. The motor has been rebuilt with forged pistons and bored .30 over!!



So please if you can tell me all that I will need a the right way to fuel it THANKS

[rat]

What is the expected horsepower and boost level?

A two bar map would be the way to go, but would require a remap of pretty much every table in the ecm.

[biglouie_underpressure]

you need to get with "Brock"

[Brock1949]

Alright,
First off if your planning on buying a intake and swapping heads, skip the cpi's and the holley intake and go straight for the gold, get yourself a set of 96+ true vortec heads or even the 2000-2001+ heads with factory semi roller rockers. Those heads will outflow the cpi heads all day long with the cpi heads ported and polished or not. I picked up both of my heads 2000 vortecs for 50 bucks they only had 15k miles or something stupid on them like that. I have mine completly reworked and all kinda work done on them but even in the stock forum they are amazing heads as far as Factory GM heads. Now if you go with the vortec heads your going to need the 2114 edelbrock intake and a holley 4 bolt square flange to 2 barrel TBI adapter. Combine cost you might have 50-100 more then putting those cpi heads on with the holley intake and it would be a MUCH MUCH better base for making some pretty good power.

If your interested in doing the vortec head swap with 2114 and holley adapter i can give you the run down, part numbers and stuff you will need to get the project going.

Now for fueling.. not a problem with TBI, takes a little more skill and time but will work out fine in the end. First off i ran 4lbs of boost on stock injectors with a stock chip in the computer and it learned enough over a couple days i never had lean problems or any problems with the truck running at all.

now for fueling my current boost and setup, 6lbs roughly on a mild built engine.
55Lb 5.7L injectors
Stock TBI body so far
Aeromotive fuel pressure regulator with 1:1 fmu (boost reference deal)
Walbro 190 low pressure pump (in progress)
TBI chips is working with me tunning it right now.

So first thing let me know what your planning on doing for boost as far as how much and if your set on a turbo. Now the other problem with a turbo is that they will make it a little harder to tune with a 1 bar map on a TBI injection setup. Only because the boost isn't a DIRECT byproduct of RPM.... if that makes sense. Basicaly lets say my truck makes 5lbs of boost at 4500rpm, then we know even time it hits 4500 rpm it will more than likley be at 5lbs of boost kinda making setting up the fuel tables a little easier. With a turbo, you could get random amounts of boost at random RPMS for the most part, where a map sensor that could actually see boost past 1lb would be a big help.

My setup basicaly says normal fuel table out of boost, (well its actualy a 350 fuel table out of boost) but then once the map sees 1 lbs of boost or it enter boost it goes to another table where it fuels 1lb of boost the same at 10lbs of boost it can't see the variation. So what i've done is setup a 1:1 fmu that when the truck enters boost as the boost goes up it slowly raises the fuel pressure 1lb for every lb of boost it sees then making it more variable and smoothing out the fueling of low boost to high boost.

So anyways kinda let me know some more details and what your thinking but as of right now the only problem i'm having with a TBI setup is leaking throttle shafts, which once i get a extra one or two from jesse i am going to try to machine tighter inserts or even sealed bearings...

[rat]

So first thing let me know what your planning on doing for boost as far as how much and if your set on a turbo. Now the other problem with a turbo is that they will make it a little harder to tune with a 1 bar map on a TBI injection setup. Only because the boost isn't a DIRECT byproduct of RPM.... if that makes sense. Basicaly lets say my truck makes 5lbs of boost at 4500rpm, then we know even time it hits 4500 rpm it will more than likley be at 5lbs of boost kinda making setting up the fuel tables a little easier. With a turbo, you could get random amounts of boost at random RPMS for the most part, where a map sensor that could actually see boost past 1lb would be a big help.

It will be interesting to see how consistent this works out for you. I think it will depend on the weather, engine load, gear, and a ton of other factors as to weather you hit the given boost at a given rpm. This will in turn show in the air fuel ratio. Also, this depends that when you are in boost you are at wot. What if you are at 95% throttle when you go into boost? Then you may see say 1 lb less boost. The chance that you are gonig to use 95%(usualy you just use 100%) throttle is small, so it may work out ok.


My setup basicaly says normal fuel table out of boost, (well its actualy a 350 fuel table out of boost) but then once the map sees 1 lbs of boost or it enter boost it goes to another table where it fuels 1lb of boost the same at 10lbs of boost it can't see the variation. So what i've done is setup a 1:1 fmu that when the truck enters boost as the boost goes up it slowly raises the fuel pressure 1lb for every lb of boost it sees then making it more variable and smoothing out the fueling of low boost to high boost.

While your fuel pressure gauge says that you are getting more fuel pressure when you get into boost, your 1:1 ratio isn't giving you any more fuel pressure. It is only keeping the pressure constant. The boost tries to push the fuel back into the injector. So, if you don't raise pressure with boost it is equivelent to your fuel pressure dropping 1:1 with boost. Your regulator is only keeping the pressure constant with respect to intake bonnet pressure. This is why the fuel pressure drops 3-10psi on a multiport car where the injectors see vacum drops at idle.

Without a boost refferenced guage the actual fuel pressure vs gauge pressure would look something like this without the boost refference:

Boost---F/P Gauge reading---Actual pressure seen at injector
0-------13------------------13
2-------13------------------11
6-------13------------------7
13------13------------------0
At 13 psi of boost you won't get any fuel :eek:

Now, with your 1:1 rise
Boost---F/P Gauge reading---Actual pressure seen at injector
0-------13------------------13
2-------15------------------13
6-------19------------------13
13------26------------------13

Since your injectors are not behind the throttle plates you don't have to worry about vacum affecting the dynamic fuel pressure.

[Brock1949]

Ya there is alot of variable in the setup, its still alot easier to figure boost to rpm with a sc then a turbo, it just adds even more variables. However when you talk to the guy at tbi chips he acts like the map sensor going into boost is only to switch the fuel maps really past that the computer will still activly work on fueling it based on readings of other sensors that don't care what the boost are. The biggest problem comes in when the base programming isn't a close enough tune for the ecm to just be doing fine tuning, so if the boost comes on to strong to fast and the fuel map isn't in the ball park by the time the computer figures it out your going to have a pile of parts.

Also on that fuel pressure reg, it doesn't seem to be quite accurate on 1:1 if its only canceling out boost. When i have my truck set a little over 14lbs and rev it up to say 3000-3500rpm it will blow into the low 20's, with the stock fuel pump. So its kinda hard to tell that would mean at like 3000-3500 rpm the engine is seeing 5-8lbs of boost at pretty low rpms. So know knows until i get the new fuel pump in, boost gauge actually installed right so i know its all accurate and the laptop on the ecm then i will have some more accurate results.

[THA_BAD_ONE-0]

http://static.summitracing.com/global/images/prod/large/edl-2114_w.jpg
Whats the part number of the tbi adapter plate

[rat]

http://static.summitracing.com/global/images/prod/large/edl-2114_w.jpg
Whats the part number of the tbi adapter plate
This should be it: http://store.summitracing.com/default.asp?target=partdetail.asp&autofilter=1&part=HLY%2D17%2D45&N=115+400178&autoview=sku

17-45

[Brock1949]

My project is working out really well with the supercharger, its at roughly 5psi on a built motor and i'm at about 80% on standard 350 injectors.. so i am about out of fuel on those going to 59lb or 454 injectors soon though.. MAybe need to up the boost, install the alky injection and then see where i'm at.