efi. What are my options ?
 

Every time i browse the engine rebuild board im always drawn towards the efi stuff and with my engine build nearly underway (don't get excited, its gonna take me forever the way im going!!) I can't help but think that I should really try to run efi and probably (seeing as the budget is so out of the window) twin plug. Can anyone give me a basic introduction into the wonderfull world of efi? altough im going on about no budget i would like to try and do it as cheap as possible. how does it work and what are my options? Iv asked some questions before on efi but i think i need a better understanding of how it works before i go any further with my project. My engine spec list is 79 3.3 with up to 8.5-1 comp (depending on how much i shim), ARP hardware, balanced shot peened rods, sc cams, up to 1bar (depending on how much comp I run!) my target is 400 hp which I think that I will get with CIS but im thinking that I may want more......


Andy

I'd suggest searching theTurbo911 site. There are several people on the site that have done efi on their turbos.

I just got the book "Building & Tuning High-Performance Electronic Fuel Injection: Custom Engine Management Systems" by Ben Strader. It's the best EFI book I've seen and I've seen quite a few in the last few weeks as I'm trying to decide which system to get.

Another good source of info is http://www.efi101.com .

Hi

Also browse the megasquirt site, it has some great explainations about EFI which are useful even if you don't use their controller

HTH

Neven

thanks blokes, the book sounds interesting. ive seen people talking about the megasquirt system, it sounds like quite a nice system thats sensible in the wallet dept too.

ANdy

Motec, DTA, Electromotive, Tbitz's kit on this board. What do you want, how much do you want to spend, yada yada yada.

In excellence I see an ad for 911 turbo injector blocks all the time. The parts look pretty nice. Also, do you want to keep your dizzy? Go crank fired? Datalogging capability?

Keep looking, then look some more.

Andy:

I converted my 930 to EFI this summer during my engine rebuild. To sum it up, I'd do it again. I have 431 RWHP and that is with a conservative tune in the computer.

You need to decide now though because if you go EFI, you need to increase the size of your intake ports to match the 3.2 intake.

I went with Electromotive. Bought all of my stuff from Clewett Engineering, which makes it very easy.

Whether you go with DTA, Electromotive, Autronic, or Motec, you will be happy.

Pics of my rebuild are at:
http://www.competitioncustompaint.com/rebuild/rebuild.html

My first session out on the track after the rebuild I improved my lap times by almost 2.5 seconds. My car doesn't idle well yet until its warm, but it doesn't bother me that much yet. I'm still playing with the computer to try to get it to idle better.

Brian

Brian, are you using an Idle Air Controller? I'm still trying to decide if I'm going to use one or not.

Yes, I am using one.

But I'm using 72lb injectors and its pretty rich when it idles. I think that is what the problem really is.

Brian

I'm planning to use 55lb injectors. What's your maximum duty cycle and fuel pressure?

I'm running 55psi of pressure (I think, if that is the stock fuel pressure regulated by the carrera fp regulator).

I'll look through my datalogs from the track and let you know what the max duty cycle is.

Brian

I am using an idle air control. Mine is a two wire VDO which is actually a Volvo part. It took a while to get a decent idle and actually when bone cold I have to keep my foot on the throttle for 10 seconds before the IAC can take over. I think I need a bit more warm up enrichment.

125Shifter: I looked at my data logs and my duty cycle tops out at 69%.

cheers for the info blokes but whats duty duty cycle? air idle control? im sort of familiar with the idea of being able to control the amount of fuel at any given point through the rev range with efi but can someone give me a quick run down of exatcly how efi works and what sensors are used/what they do/how you adjust them/why you adjust them?!!!!? i know thats a bit of a tall order but i would really appreciate a quick overview so i know what i would be letting myself into and whether or not i have the brains to install and operate/modify it!

Thanks for peoples time

Andy

Idle Air control is a small electric motor that is an air bypass between the air source and the intake. It bypasses the throttle and provides air to the engine when the throttle is closed. The ECU will recognize the closed throttle through the throttle position sensor (TPS) and in the ECU you program how you want the idle air control motor to behave. It basically opens and closes to allow air past the throttle body.

MAP - manifold air pressure, normally used in place of a Mass Air Flow sensor, measures load on the engine by measuring air pressure entering the intake.

Crank Sensor / Trigger wheel - used to let the computer know where the engine is in relation to TDC on #1.

CLT - coolant sensor - for us - an oil temp sensor

MAT - Manifold Air Temp - an air temp sensor as close to the intake as possible and the computer makes fuel adjustments, adds more fuel, etc.

Cam Sensor - magnetic sensor that can be used if you want to go full sequential injection.

WBO2 - I have mine wired into my ECU, but only for datalogging purposes, the computer does nothing with the data in my case.

All sensors are calibrated/adjusted within the ECU. You also tell the ECU how you want it to react to the output values of the sensors.

I think that's about all that I use. TPS, MAP, CLT, Crank, Idle Air Control, MAT, and WB02.


Brian

Duty cycle is the % of time that the injectors are open.

Brian

Andy,

With EFI you can control timing and fuel throughout the RPM range. You can compensate for different conditions with the sensors. Basically the base fuel and timing maps are adjusted based on input from the sensors. For example when the engine is cold you can add some fuel enrichment. When there is boost pressure you can increase the fuel and retard the timing at the top end.
Sensors needed are a CRANK sensor (timing), Oil Temp, Air Temp, Manifold Pressure, Throttle and optionally a CAM sensor for sequential injection.
Duty cycle is how long and often an electronic item is open or closed. An injector is usually rated at lbs per hour at 80% duty cycle at a particular pressure.
An Idle air valve controls the idle speed by varying the amount of air. It also has a controllable duty cycle but uses other factors such as how often to check for a change in idle speed.

Since you are in the UK you might want to check out the DTA P8 engine management. You can download their manual and learn a lot about all this stuff.

Andy

If you go to http://www.megasquirt.info/ and look under "How megasquirt works" it gives you a pretty good description of EFI and the function of everything mentioned here

HTH

Neven

Accel Gen 7 is the system I would use
Eric Hood

nice one brian/magic/neven/eric! i hate to ask such basic questions but if i don't know then......! do all the different ecu's require their own designated sensors or are they more or less the same? (i.e. just wired in as switches/variables)

Thanks again,

Andy

Most ECU's use basically same sensors...same MAP's, same Idle Motors, same temp sensors, same lambdas (except those few ones that accept Wide Band Lambdas, but those can often use narrow band as well).