My 90 GTUs had its engine rebuilt and full bridgeported by the previous owner. He was told that the fuel system would need to be upgraded to tune the motor. So he took the cheaper route and got a 650cc carb. Now that I have it, I'd like to unleash some uptapped power by putting in a EFI system. I've searched the threads but nothing exactly what I need. Could somebody tell me all the parts I would need for this conversion and what size and brand EFI would be the most efficient?
Thanks
Matt

 

How about the stock one? Upgrade the ECU and tune it that way.

 

Stock intakes, 550 turbo II injectors and a air/fuel computer. You will probably have to put a stock engine harness back in the car along with the computer. Does it have a CAS or dizzy?

 

I believe the computer is still in the car, just unconnected. Which probably means the wiring harness is still there too. Would I not want bigger injectors than 550cc's?

 

Because you don't have a turbo that I know of, the stock injectors are 440's and I think they max out ~200hp. I think Kahren maxed them out on one of his 6 port motors.

 

why dont you stay n/a and put some kind of weber side carb on it? you can turbo those

 

stock injectors are 460cc.

 

He's not talking about turboing the motor, or swapping the carb. He asked about getting rid of the carb altogether so he could use EFI.

 

The most efficient setup would be Weber IDA type individual throttle bodies (ITB) and a standalone EMS. Examples:
http://www.tweakit.net/shop/product_...roducts_id=117
http://www.twminduction.com/Throttle...leBody-FR.html
http://www.twminduction.com/ThrottleBody/carb_vs_fi.pdf

Off the top of my head, you would need:
- Weber IDA type throttle body with fuel rails, bell mouth stacks, and other required hardwdare (recommend one that accepts 4 fuel injectors rather than only 2 fuel injectors)
- Throttle Position Sensor (The stock Mazda TPS is lousy)
- Fuel injectors (recommend four 550cc/min peak & hold Bosch, Siemens, or RC engineering brands)
- Weber IDA-compatible intake manifold
- Weber IDA type air filter and hardware
- EFI fuel pump and regulator (recommend SX or Aeromotive brands)
- 3/8" OD (A/N -6) fuel lines
- Standalone EMS (Haltech, Wolf, Electromotive, Autronic, Motec, etc., whichever brand has a LOCAL tuner in your location). With a bridgeport, try to get an EMS that can fire the injectors right before the exhaust port closes so you can avoid the reversion wave kicking the fuel back up the intake.

Be careful, the Mazda fuel injectors are rated at about 37psi +/-3psi, while most aftermarket fuel injectors are rated at 43.5psi. Therefore, the stock 13B NA fuel injectors which flow 444-472cc/min @ 34.1-39.8psi (averaged to 458cc/min @ 36.95psi) would flow a calculated 496cc/min @ 43.5psi when converted to the common aftermarket standard. Therefore, it is easy for the uninformed to underestimate the Mazda injectors or overestimate the aftermarket injectors.

As for sizing, you can use the Fuel Injection Worksheet at the RC Engineering website. Basically, four 550cc/min aftermarket fuel injectors are good for about 300bhp on a non-turbo engine with a 43.5psi fuel rail pressure, which should fit your application.
http://www.rceng.com/technical.aspx

 

well the reason I'm a lil confused about the size injectors I should get is bc the carb is a 600cc and you said "As for sizing, you can use the Fuel Injection Worksheet at the RC Engineering website. Basically, four 550cc/min aftermarket fuel injectors are good for about 300bhp on a non-turbo engine with a 43.5psi fuel rail pressure, which should fit your application."

My car is dyno'd at 285 rwhp so I'm already about there. And also expect more horses to come out with a EFI so I need more room for more HP.

 

yeah, just did the calculations and if I desired about 400 hp then my injectors would have to produce 661cc/min

 

So get 4 660 injectors, put on all the stock manifolds, and put in a rtek. Simplest way to go with it.

Just a warning, stay AWAY from venom injectors.

 

Carbs are rated at CFM (Cubic Feet per Minute) of air flow, while fuel injectors are measured at CC/Min (Cubic Centimeters per Minute) of fuel flow. The ratings are completely different, which could be why you are a 'lil confused', lol.

I think somebody has been bullshitting you on the dyno numbers. Normally a bridgeport 13B makes about 255bhp with a Holley 650. Before you spend a lot of time and money modifying your engine, you may want to put it on a dyno to see what it really produces as-is.

 

Well, it has a Full 2.5" free flow exhaust and was custom tuned. The exact dyno stats where: 287hp and 235 tq I will dyno it again for my own sake, but I'm pretty confident that it is what it is. As for your Carb and Injector comment. I don't know much about carbs and when I was talking to the guy about the car before I bought it, he said CC's in reference to the carb.