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Injectors?

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BgBlock69

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What injectors are used in the 89 without LT 1 motor?

1. Pressure?

2. Will later model fit?

3. If I put in a higher pressure what will be the difference in performance?

4. Will the Computer recognize the change?
 

vigman

Motor head!!!!
Joined
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Messages
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Location
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88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Answers

What injectors are used in the 89 without LT 1 motor?

LT-1 was not offered in 89......

1. Pressure?
Rail pressure was 40.5 psi ( from factory )
Stock injectors are #22 or 22 gallons per hour..I forgot the flow rating.... maybe somebody will chime in and straighten this out.

2. Will later model fit?
Dunno..never tried..but I'm guessing so.

3. If I put in a higher pressure what will be the difference in performance?
You mean a higher FLOW injector.. the pressure is controlled by the regulator & the pump the flow is controlled by the ECM & the Injector..... What other things are you doing to the motor?

4. Will the Computer recognize the change? Yes the O2 sensor will see the mix change.. but if you put in TO LARGE of an injector you might be out of range for the ECM.


Why do you think you need NEW injectors?


Vig!
 

Ken

Gone but not forgotten
Joined
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Messages
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Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
Re: Answers

The flow is rated in pounds-per-hour. The Brake Specific Fuel Consumption (BSFC) is simply how many pounds of fuel it takes to make 1 hp for 1 hour. BSFC will be about 0.45 for most street injection set ups. The formula for pounds of fuel per hour is: BSFC × Peak HP = lbs/hr

The computer controls the duty cycle. If you run too large of an injector you're simply wasting your money; the computer will keep it closed until fuel is needed. On the other hand, if you run an injector that is too small, the computer will be cycling it open much more often to try and meet the demand for more fuel, which of course, the injector can't deliver.

Injectors will work best if they don't exceed more than 85 duty cycle. An injector that flows 26.5 lbs/hr will be at an 85% duty cycle when flowing 22.5 lbs/hr, but you may not find an injector that flows exactly what you need. The formula for injector sizing is: lbs/hr = (BHP × BSFC) ÷ (No. of Injectors × DC)

Where:
BHP = Peak Brake Horsepower
BSFC = Brake Specific Fuel Consumption
DC = Injector Duty Cycle


You can figure how much hp your injectors can support with the following formula: HP = (lbs/hr × No. of injectors × DC) ÷ BSFC

Using a 0.45 BSFC is good for normally aspirated engines, but if blower, turbo, or dry nitrous system is being used, a 0.5 BSFC is better.

If you are using 1 injector per cylinder in a normally aspirated engine, you can used the following formula to estimate the size of the injector by air flow: Injector size = (CFM × 0.44298) ÷ (No. of cylinders)

And just for the heck of it: ;) There are two basic types of injectors; saturated (high impedance), and peak and hold (low impedance).

Saturated injectors are more common and draw less amperage form the ECU. Saturated injectors also create less heat because the have less amperage. A saturated injector will have an impedance of about 12 ohms, this means that at 12 volts it take 1 amp to hold the injector open. Peak and hold injectors will have an impedance closer to 2 ohms and draw about 6 amps. Most ECM's cannot handle the amperage and using peak and hold injectors will harm the them. If you desire peak and hold injectors a separate aftermarket injector controller or aftermarket ECM may be required. Peak and hold injectors use high current to open the injector very quickly and precisely, then they draw less to hold the injector open. For high horsepower and flow rates, the peak and hold injectors are much more precise, but they are more venerable because of the heat they make. If it is a street engine that will be daily driven, saturated injectors are more reliable for long term use. Peak and hold are better for high horse power and competition use.

_ken :w
 

vigman

Motor head!!!!
Joined
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Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Woah KEN

Big math there... I'm impressed... all great info.



Vig!
 

KANE

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Mar 2, 2002
Messages
3,244
Location
KY
Corvette
Dark Blue 1982 Trans Am(s): Polo Green 1995 MN6
Here are some thoughts based upon my experience from building my 1978's TPI system-

STOCK STYLE SYSTEMS (250-400hp / MAF or MAP)
1.) Use LT4 injectors (they are a better design) or a Lucas disc type
2.) Run with GM spec fuel pressure.

The GM system will easily support engines up to 400hp. However the stock runners and throttle body won't. Allegedly, you can run 5.0L Chevy injectorson a 350- but you need to up the rail pressure. I just say to stay away from 5.0L injectors period- no confusion then.

What you have to watch for is changes in the cam from factory specs if you have a MAP system. MAF can compensate for most cam changes. But anything crazy will ALWAYS require a chip change.

The key to performance isn't the injectors as much as its getting through the restrictive performance generated by the stock runner, base plate, and throttle body. Curiously, the 305 uses the same system (minus injectors and regulator) from base plate to throttle body. Theoretically, a 305 runs with the same set up as a 383. Hmmmm. An engine can only make as much power as it can efficiently take in. The GM design makes great low end torque but not the high end power. Remember, this is a leap (a big one) in the evolution of the crossfire system that debuted in 1982.

There is always the Mini-ram system. It looks like an LT1 manifold for an L-98. Its great if your engine produces power at a 6k red line. Most of us don't and we wouldn't realize the gains anyway because our mills don't make 450hp+.

I have a friend who runs a Fast Burn 385 with an ACCEL TPI system. It runs excellently through its powerband. He had 36lb injectors that were accidentaly included in his package. Needless to say... it ran awful until he got 24lb injectors.

If you are noticing diminished performance, take out your injectors and have them cleaned and bench tested for flow. You may have one that is sticking or leaking. You'll get lousy performance but the idiot light will never trip.
 
T

tom_85_vet

Guest
Ken
Your the man!!!!
You must be an engineer.
Just to add my $00.02, I have the adjustable fuel pressure and turned it too high.
The eng went into a race condition, I guess the ECM was trying to adjust the duty cycle and exceeded the limit. My suggestion, unless the car is used for racing go stock.
tom
 

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