Question: I just had my Fuel Injectors serviced/rebuilt and flow rated.

They came back as flowing 520cc, all four injectors @ 43.5 psi.

***Is this right?

I've always read that they are 550cc for all RX7 turbos 86-91 regardless of HI or LOW IMP.

Did a couple searches but unable to find anything. Just want to make sure before installing them back in.

Any information would be great.

 

they are supposed to flow 550cc @38psi.

who did the test? their machine is probably somewhat off calibration as i have seen with a local injector shop also.

 

Our Denso fuel injectors are rated at 550cc/min @ 2.5bar (about 36psi). In theory, that calculates to about 602cc/min @ 3bar (43.5psi).

Your results of 520cc/min @ 3bar calculate to about 475cc/min @ 2.5bar, which is not within the factory service manual standard of 532-568cc/min. Therefore, your injectors should have failed their test. Maybe they screwed up the test?

 

check the numbers on the side.. s5t is 195500-2020 and s4 is 19500- 1370

if you have 195500 - 1350 or 195500 -2010
then you have s4 or s5 NA 460 cc injectors and they are flowing about right

 

my injectors are 19500-1370, s4, color purple; came out of a s4 TII 1988.

So your stating that 460cc flowing 520cc (+70cc) is about right....

And 550cc that are flowing 520cc (-30cc) is wrong....

???

Can somebody please explain this?

 

Okay, will call my buddy and double check the PSI he used and see when the last time his test bench was Calibrated. Also, can somebody point me to where I can find the Specs on these injectors, so I can print them out for my buddy who hooked me up, thanks again.

 

the issue lays in what pressure was used in the original mazda litterature for the injectors

mazda FC fuel pressure is 38 psi
and IF the injectors are rated at 550 cc at this pressure
and IF you have likely tested at 43.5 .. then the net difference of 5.5 psi .. is nearly 15 %

while this doesnt translate 100 % directly proportional as fuel flow
( due to injector latency changes with unseating the pintle at higher pressures )
it would account to a 460 cc injector flowing almost 529 cc
.. take a few for the changes in latency ... making 520 cc bang on the money


following this same train of thought ..
if you have 550 injectors,, and they test to only 520 at a higher base pressure .. then there is a problem.. expecting 550 to flow as much as 625 cc when at 43.5 psi


however.. if you go to witchunter injectors and search with those numbers you will see they rate them as 550 cc at 43.5 psi
your injectors are underperforming .. but not so badly as would appear if the flow of 550 was achieved in the original stats with only 38 psi

 

Okay, Lost In Translation!

Went back to my buddy's shop to see what he was talking about cuz over the phone was like trying to understand Quantum Physics by braille.

Turns our my injectors are right on!

The PSI is set to 35.5 PSI, not 43.5 PSI.

He was reading his output on the test bench as 52.33 LBS/HR! (I misunderstood this for 520)

52.33 LBS/HR translates to 550 CC/MIN.

Installing tomorrow, thanks everybody for the huge amount of INFO and Calculations. Very much appreciated.