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01/02/94                        Revised 01/24/02

 

3.0       Fuel Injectors

 

Now that we have developed and selected the ideal fuel delivery system to meet our performance needs we must follow a similar selection process to decide on the size and type of injectors required to meet those goals.

 

One of the most significant improvements in Turbo-Regal performance over the past few years can be attributed directly to the advancement and availability of the wide variety of fuel injectors now available.  There are so many sizes, shapes, colors

and manufacturers marketed today it is hard to know where to start.  Hopefully, addressing the following questions will provide you with a systematic, objective approach to selecting the ideal injector for your performance requirements.  

 

1.         How much horsepower will we make?

2.         How much fuel is required to make that much horsepower.

3.         What size injectors are required to flow that much fuel?

4.         What are the electrical requirements of our computer?

5.         What options are available for increasing fuel flow.

 

After answering these five basic questions we will be able to establish how much fuel is required.  What injector size is required?  What are the electrical requirements of our computer system? And the type and size of injector required.

 

3.1       How Much Horsepower?

A bunch!!!  We want as much horsepower as possible but realize that this is dictated by heads, turbos, induction and exhaust.  

What do we know?   Our vehicle weighs 3450#.  We want to run 10.90's. 

The following equation can approximate the amount horsepower  required to attain this level of performance.

 

 

Example:       HP = 197.65  x  3450# / (10.90)^3 = 527 HP

 

3.2       How Much Fuel?

 

We now know that it takes about 527 HP to propel our 3450# vehicle to 10.90's.  The following equations will allow us to determine how much fuel is required to make our 527 HP and the size injectors required to flow that much fuel.

 

 

 

Fuel Req'd. =  Horsepower  x .6 #/hr.

 

Example:       Fuel Req'd. =  527 HP x .6 #/hr = 316 #/hr

 

 

3.3       What Size Injector?

 

 

Example:       Injector Size = 316#/hr / 6 = 52.7 #/hr

 

We have determined that it takes 316#/hr to generate 527 HP and that at least  53#/hr injectors are required to deliver that amount.

 

3.4       What Are The Computer Electrical Requirements?

Electrically there are two[2] classifications of injectors.  High impedance [12 - 16 ohms] and low impedance injectors [2 - 4 ohms].  The impedance can be determined by measuring the resistance of the coil in the injector.  i.e.  The resistance between the two electrical pins can be measured with a ohm meter.

 

 

The Buick ECM [Electronic Control Module] is set up to drive high impedance injectors. The stock injector’s impedance is 16 ohms.  [A high impedance injector.]

 

In the past low impedance injectors have been used, successfully with the stock ECM.  However, the [FP/INJ] fuse in the fuse box must be upgraded to a 20A fuse to handle the additional current load.

 

Low impedance injectors have two advantages.  There is a wider selection of high capacity injectors available.  Secondly, most aftermarket fuel management computers are set up for low impedance units.  This makes it highly desirable to select a driver or computer system that can utilize the low impedance injector.

 

However, our performance goal of 10.90's with the stock ECM is easily attainable.  The MDS/Multec 50# high impedance injector, the Bosch #803 low impedance injector and the Tomco #___910 low impedance all work well. 

 

 

 

The Fuel Injector Selection Guide Chart 3.0 is a listing of many of the more common injectors available today sorted by capacity.  It should prove useful in sorting out the magic surrounding injector applications.

 

Fuel Injector Selection Guide

Chart 3.0

 

#/HR	MFG.	P/N	IMPEDANCE	COMMENTS
27.5	Bosch	0-280-150-218	Hi
30.8	Bosch	0-280-150-756	Hi	[SuperCoupe "Red Top"]
30.8	[Ford]	E93Z9F593A
32	Tomco	15509	Hi
32	Lucas	5207009	/
33.5	Bosch	???	Lo	[TurboCoupe "Brn Top"]
33.5	[Ford]	???	/
35	Tomco	15508	Lo	[Green Stripe]
37	Bosch	0-280-150-803	Lo	[Green Top]
38	Multec/MSD	2018	Hi
39	Bosch	0-280-150-035	Lo
40	Tomco	15600	Hi	[Red Stripe]
42.5			Hi
46	Bosch	0-280-150-024	Lo
47	Tomco		Lo	[Special Tip]
49	Lucas	5208010	Lo
50	Multec/MSD		Hi
55
72	Multec/MSD		Lo
83	Seimens		Lo
84	Seimens		Lo
96	Multec/MSD		Lo
160	Multec/MSD		Lo

 

NOTE:  Conversion  [1 cc/min] of gasoline = .095895 #/hr.

3.5       Options available for increasing injector capacity.

 

In many cases the injector available will barely meet the performance requirement.  In our example the 50#/hr MSD needs to flow 53#/hr to make 527 HP.

The most common and easiest way to increase injector capacity is to raise the fuel pressure. The equation for figuring this out can be found in Chapter 2  but an easy rule of thumb is as follows:  

 

 

To increase the injector capacity from 50#/hr to 53#/hr the base fuel pressure should be increased about 6 pounds.  Note: This will enrich the entire rpm range from idle to max power.

 

This second option is kind of a fudge.  Adding an additional injector[s] is not exactly increasing the injector capacity but seven injectors can deliver more fuel than six.

 

Several manufacturers offer "Fuelers" or "Seventh Injector" options.  This application is not used as often now as in the past due to the wide assortment of aftermarket injectors and fuel management systems but is still a very serviceable system in the proper application.  The units are tunable and do offer drivability with good horsepower capability.

 

Remember that it takes fuel to make horsepower.  The proper injector selection is mandatory to making maximum, safe power efficiently.  Good luck.

 

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