Fuel Injectors

Fuel Injection Info


Companies like "TPI Tech" in CT. can balance injectors, they charge $8 per injector and claim to get a set to +-1% or each other or std. This is done by dissassembling the injectors and changing pintles and springs. Not for the home mechanic.

From: Curt Martin

You may remember several weeks ago I mentioned that I was sending a set of fuel injectors off for blueprinting. That has been accomplished, and the results are very interesting.

Since I wanted to avoid loosing the use of my car for a week or more, I sent a set of spare injectors from an 85 V6 Fiero with 70,000 miles on the engine. These injectors are the same as those used in my 1988.

On the advice of several on my Motor Sport Club members, I choose Marren Motorsports at 500 Newhaven Ave in Derby, CT to do the work. Their phone number is (203) 732-4565. These club members have all raved about how much better their engines run with blueprinted injectors - and since they are original and "stock", they are legal in SCCA classes.

Marren actually rebuilds the injectors, ultrasonically cleans them and guarantees no more than a 2% differential between injectors. The price is $23.75 per injector. Not all injectors can be refurbished. If an injector fails they will supply one that matches the others. Of course, you have to pay for the new injector. I was lucky, all of mine could be refurbished.

The injectors I sent to them showed the following flow rates per minute with a test pressure of 43 PSI and a test pulse of 6.0 MS when they were received.

Cylinder Number ->  1     2     3     4     5     6
Flow in cc         42.1  39.8  44.0  44.0  38.9  41.2

The spray pattern test showed injectors 2,3,5 & 6 as being extremely poor.

The differential average was 13% - or 7cc from the poorest to the best injector after refurbishing. Wow, that is almost an ounce of fuel every four minutes!

The refurbished injectors showed a flow rate ranging from a low of 44.9 cc per minute to a high of 45.8 cc per minute, well within the 2% tolerance. The spray pattern was near perfect and there was no leakage.

The total bill was less than $150. Keep in mind NEW injectors are $75-$100 EACH, and remanufactured ones $40 - 70 each. They may not have the same flow differential.

I commented to the technician when he called that they were a lot cheaper than a new set of Tomco Disk Injectors. He replied that the Tomco injectors did not work as well as they were advertised to do and I was much better off with these. The Tomco injectors generally fell short in the upper RPM range.

Based on his calculations, the engine these injectors came out of should see an ESTIMATED boost of 20-25 HP with drastically improved mid range torque and upper end response. Since they did not come out of my engine, my results could be different. But, since they both have the same mileage, I would imagine similar results. Please note, this is not all NEW power, but mostly RESTORED power lost to dirty injectors. There may be some new HP gain due to more efficient balancing of the fuel delivered, enhanced flow and improved spray pattern.

I asked how often this should be done. He recommended every 30-40 thousand miles. He also said replace your fuel filter often, use quality gas and avoid excessive use of injector cleaner additives. His opinion is that over use of cleaning additives strip the insulation off of the injector pulse windings. He also said that pressure cleaning may reduce fouling but does nothing to improve leakage and balance and can also damage the injector coils.

He convinced me.

From: Randy Agee

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