Inliners International Forums General Discussion Hi Performance EFI in a 250

Hello everybody!

Does anybody here know any EFI project for a 250 Chevy?
I´ve been searching for it and all I can find was websites like the MegaSquirt and Hilborn parts.
If anyone knows something like that, please send me!
Thanks

You could pull a factory TBI system off a 4.3L V6. They're 262ci, so the fuel requirements will be just about the same. You could make an adapter for the TBI unit to fit a 4bbl intake, and then just swap over the rest of the fuel and electronics for the system.

Thanks Blue

But I was thinking something beyond that. You must know the Santucci´s book, don´t you?
Well, in this book there are some Fuel Injections that are closely to what I´m thinking about. It´s something like one throttle for each intake port(siamesed) with one or two injectors per port.
I´ve saw the MegaSquirt System and it looks really good but there´s a lot of things, like laptop, programmer, MegaView and Stimulator that in my opinion, and case, is unnecessary.
I´m looking for an EFI simillar to the Mechanical ones.

Thanks a lot!

Seis Canecos 74

You have a few decisions to make:

1) do you want to run straight mechanical fuel injection or EFI.

If you choose mechanical then look a hilborn or tom's flying toilet.

If you choose EFI then you need to choose:
a) an OEM ECU and wiring (like the ford EEC IV used on the 300 straight six).

or

b) aftermarket (More $$$$$)

or

c) Megasquirt.

If you think you will need to be able to tune the fuel curves yourself its hard to beat megasquirt.

At first the system look difficult to assemble and configure ( it does take some effort to read and understand the available information) BUT and this is a big BUT the tunning tools that are available FREE are world class stuff. They are setting the standard to which all other aftermarket tuning tools are being compared against.

If wires and computers are not your thing then stay with mechanical fuel injection abeit you lose the ease of tuning.

Does Cliffords offer a complete turn key fuel injection kit if you have the money?

John C.

I don´t know about Clifford´s products. But I´m sure that its not cheaper than the Whole MegaSquirt thing.
Now I´d like to know some informations about which cam do I have to use.

I´m using a 278º Isky, 478 lift and 108 lobe center.
I know that the lobe center must be smaller, something arround 112º. But can I still using this cam if I put the MegaSquirt?

Thanks

Why would you need to change the cam to run fuel injection? Sometimes a large cam can create low end problems but there's fairly easy ways around those. You can install a buffer for MAP sensors and then theres hybrid throttle position / speed density tuning. This is how I understand it anyways.

The cam will be fine, like the other person mentioned you may have to put a restriction in line with the MAP sensor.

What kinda restriction?
Does the MAP sensor works fine with large lobe center cams?

Here is another site with good info (lots of it) and custom systems at what appears to be decent prices. Information alone is worht a look IMHO.
http://www.customefis.com/

Thanks Twe56

This site helps a lot!

But there are some questions that isn´t clear enough for me.
Like:
Does MegaSquirt control the timing? If not, what is the right timing to use?
How about the idle?

The basic orginal megasquirt does not control timing, it does control a on/off fast idle valve or solenoid. That said people have modified the s/w to do timing control with the orginal hardware.

What is being worked on right now is the 2nd generation megasquit that will do a) fuel, b) timing control and c) variable fast idle just like the OEM's do it.

If this is your first time using EFI I strongly urge you to tackle either the fuel OR timing control don't do both at the same time.

Meagsquirt will run just fine doing one or the other. Suggest you start with the fuel side and run a distributor. After the fuel tuning is done you can then lock out the ditributor mechanical and vacumm advance and tune the timing control.

Hope this helps.

Can the MegaSquirt be use with a throtlle system like those in the Sissells(www.sissellsautomotive.com) page, in the Complete Engine Catalog section??
Or do we have to make some kind of plenum?

Short answer is yes.

The only requirements are that you install a TPS and common all the runners together downstream of the throttle blades with a 3/16" to 1/4" solid line for the MAP signal.

Sycronizing all the throttle blades is going to be a challange. Remember EFI in more picky in this regard then a carb. With a carb if one hole is flowing more air the carb adds the right amount of fuel for the air flow since the fuel flow is related to the signal applied to the venturi.

EFI can't sense this since you have only 1 MAP sensor for the entire engine.

It would be a lot less headache though to fabricate a plenum and run 1 throttle body.

OK Efi! I agree with the headache thing, but I don´t mind. If I won´t headaches I wouldn´t change the carb set up, which is working good.

What is a TPS?

Do you mean that I should weld a kind of pipe to comunicate the tree throtlles to use only one MAP sensor? Can I use more than one?

I burn alcohol and I have a water heated intake, which without that the engine simply doesn´t work.
Another doubt is if I have to do some heater in the intakes to still runing in alcohol. And how can I do that?

TPS = throttle position sensor.

No you can use only 1 MAP sensor for the entire engine and it must have a manifold pressure signal from all cylinders. If you use 1 throttle body then its easy. There is no real adavantage in running individual throttle blades.

TPS - Throttle Position Sensor

The problem with the MAP sensors is that most fuel injection setups cannot inject different amounts of fuel to different cylinders. So if you have one throttle blade that's not opening quite as much you get less air to that part of the manifold but the fuel level doesn't change -- you go rich. Or if one throttle is open further then you get more air and those cylinders go lean.

You could add more MAP sensors without a whole lot of trouble but the computer wouldn't be able to make use of the extra information. So what EFI proposed was just to make sure that the throttles were sycronized. That way even though the MAP only measures pressure in one intake section it doens't matter.

Guess I wasn't fast enough

And EFI, I'm pretty sure that there are advantages to running individual throttle blades; it's one way to increase air flow. But the extra work for the fuel injection may make it unworth your time.

OK! The throtlle thing I understand!
And what about use alcohol? What should I do?

The main reason that you need water heat for a carb/alcohol installation it to prevent fuel drop out (puddling) when the thottle is opened in the relatively long intake runners. With EFI the injectors are typically mounted very close to the intake valves (if it possible aim the injector at the back of the valve). This really reduces the distance for the fuel to puddle out of the air, so water heat may not be needed. What may be possible is to preheat the air to increase vapourization.

Greg,

Actually it is important to common up all the runners in a independent runner installation to generate as smooth a presuure signal as possible especially if a big cam is intalled, otherwise the MAP sensor will see the opening/closing of just the 1 clyinder and cause erratic idle.

This condition is identical to having an over 270@0.050" cam installed. At some point the MAP signal becomes unusable due to fluctuating manifold pressure.

Do you mean that I should weld a kind of pipe to comunicate the tree throtlles to use only one MAP sensor?

Yes.


Can I use more than one?

I do not know of any EFI systems that use more than 1 MAP sensor/engine.

Ok I understand what you're saying from that side of it. Yes, definetely. I was thinking just from an air flow point of view.

But in my case the cam is 248@0.050. What should I do with the MAP sensor? Use a restrictor? What kind of restrictor? Doesn´t the MegaSquirt correct this fluctuation in the manifold pressure?
And if I´ll use tree throtlles, should I use tree TPS to or just one?

straight 6 fuel injection and electronic ignition
noticed thes posts, i have adapted the 4.3 liter v6 chevy throttle body fuel injection and electronic ignition from 1 92 chevy truck to my 251 cube 47 fargo (dodge) flathead 6 and it is the best thing i could ever have done for the old girl. will share how to and photos with any one if they are interested.

John

John

I´m intrested in this project to see how it looks like. But I won´t use one throtlle body and I will use megasquirt system.
Where I can see the photos?

[QUOTE]Originally posted by seiscanecos74:
[QB] But in my case the cam is 248@0.050. What should I do with the MAP sensor? Use a restrictor?

If the line from the manifold to the MAP sensor is rubber put a peice of round aluminum in the hose so it is air tight and drill a 0.01" hole in it. You will have to expriment with the hole size.

The desired result is to get a stable pressure signal to the MAP sensor. If in the end you cannot achieve this, you can run megasquirt in "alpha-n" mode, but its harder to tune the motor.


Doesn´t the MegaSquirt correct this fluctuation in the manifold pressure?

No.

And if I´ll use tree throtlles, should I use tree TPS to or just one?

1 TPS is just fine. Megasquirt uses the TPS for 3 purposes:

1) clear flood mode
2) acclerator pump mode.
3) closed loop tuning

The MAP and tachometer input determine the engine load, the TPS determines driver demand.

The coolant and intake air temperature sensor "trim" the amount of fuel being added.

The O2 sensor give input to the closed loop tuning.

Thanks EFI

Helps me a alot. This type of information I couldn´t find anywhere.
About the restrictor you mean that as smaller as inside tube is, better the MAP will answer to the fluctuation manifold pressure? I´m thinking about an aluminum welded a pipe linking the 3 throtlles to put the MAP sensor. It has to be placed right in the midle of the tube??

I´he read something about TP sensors, or something like that. It was write that this sensing has much better working in race cams engines. Is that true?
How about use TP load sensing instead a MAP sensor?
What is the main difference between them?

I'm not the one to explain it. You might want to look it up more on megasquirt.info. I have some books with the definition too but I don't have them handy.

Basically there's 3 ways to calculate engine fuel required. We're worried about two:

Alpha-N : Based on RPM and throttle position. Throttle position doesn't fluxuate even if you have a crazy cam so this can deliver a good idle overwise not possible. I think the problem was resolution of the throttle position sensor. At some positions a very small change in throttle would change air flow a lot and the resolution wasn't good enough for good management.

Speed-Density : Based on RPM and intake pressure (density). This has good resolution and good performance so long as the intake manifold pressure is fairly stable. This is true almost all the time -- unless you're trying to idle an erratic cam and the vacuum is all over the place.

I'm not sure what it's current status was, but MS was working on hybrid configurations. You ran Alpha-N until a certain RPM or throttle position or something then the system switch to Speed-Density automatically and smoothly. Best of both worlds.

I hope I got the idea across. Greg

What about the injectors?
What type is better in this case?
Low or high impedance?

High impeadence injector are easier to get MS set up for. Running acohol you will need bigger injectors than if your running gas.