What do I need for injectors? '93 vette

**Jay72** · 05-09-2015, 11:16 PM

I'm really confused about what fuel injectors to get for my car. It has an LT4 hotcam, mostly stock otherwise.Email tune. I just want to change the injectors. It has the stock 17087325's which flow anywhere from 18 to 25 lbs. Depends on who you ask. I have a set of 17121068's that flow either 19.45 or 22.76 lbs. All at 43.5 psi. That info came from this site http://users.erols.com/srweiss/tableifc.htm And I have some blue top fords, and some orange bosch's off a ford. If they're rated at 32 psi, the 19's should flow 22.xx lbs at 43.5. Then theres the stock injector flow rate programmed at 23.80. Basically I want to replace the old original injectors. How do I know what size to get and what do I need to change in the tune? Thanks in advance for any info.

**Jayz28** · 05-10-2015, 12:23 AM

The stock injectors are fine for your setup. You won't need to upgrade injectors until you have modded your car to the point that it's starving for fuel.

Even with a tune, there won't be a horsepower increase.

With that said, a popular injector size for n/a engines is 36lbs.

**Jay72** · 05-10-2015, 08:54 AM

What if they're old and I just want to replace them. Theres a crack down the outer case on most of them. Sometimes it idles rough and the injectors are the only thing that hasn't been touched. I don't think I could even send these off to be cleaned and flow checked seeing how they're cracked.

***popo8*** · 05-10-2015, 09:31 AM

Honestly... if ur concerned... send em out to have em cleaned and tested. If ur planning more mods in the future ull have a reason to upgrade then. If u dont have plans... then buying bigger ones will require retuning to reduce their flow or else ir gonna run rich and have a good chance of washing and hurting ur motor.

**Jay72** · 05-10-2015, 09:48 AM

Originally Posted by popo8

Honestly... if ur concerned... send em out to have em cleaned and tested. If ur planning more mods in the future ull have a reason to upgrade then. If u dont have plans... then buying bigger ones will require retuning to reduce their flow or else ir gonna run rich and have a good chance of washing and hurting ur motor.

Thats kinda what I'm asking. I have bigger and better injectors just laying around. I have the tuning equipment. The only thing I don't have is the information on what the stock injectors actually flow. I have not seen two sources with the same information, everything I've seen gives different flow numbers for the same injector part number at 43.5 psi. People say the Multecs are garbage anyway, these have a crack down the side of almost every one, I can't see sending them out to get cleaned and tested. I guess sending them out to get flow tested would give me an answer on what to replace them with.

***popo8*** · 05-10-2015, 10:03 AM

Well if u have the money and just want to do it cause u do... then go for it... but please retune.
@MoeHorsePower is our resident tuner. Maybe he can give u advice.

**Jay72** · 05-10-2015, 10:47 AM

Ok, thanks.

**gmpowered** · 05-10-2015, 12:03 PM

92 93 vettes are "supposed" to be 22lbs. Your stock tune will tell you what they are.

You've done a good job looking at injector data and its effect of rail pressure. Use this to size your injectors. http://www.witchhunter.com/injectorcalc1.php

You DO NOT want to mod till the engine starves for fuel. You always want a good cushion. You do not want to exceed 80% duty cycle. The injector stops pulsing and hangs open at that point, killing efficiency and HP.
If you ever have a fuel delivery problem with small injectors at wot you are fubar'd.

Newer injectors have better spray patterns and atomize fuel better than most oldies. IMO factory injectors BLOW.

Running the factory injector data through the calc shows you should upgrade.

To upgrade injectors you need the data for them, you need the injector offset data and plug in injector size. Good data will be paramount in the tune. Its fairly straight forward in tunerpro(if thats what your using) although i haven't used it in a few years.

**Jay72** · 05-10-2015, 01:50 PM

The link in my first post lists the part number thats on my injectors (17087325) as 19.88 lbs at 50 psi. But I have the stock fuel pressure of 43.5 (+/- 1 psi) and that link says 18.54 lbs at that pressure. I do use TunerPro and it says the stock Injector Flow Rate is 23.80. The guy I had tune it for the cam left that stock. FWIW a WOT DataMaster log shows 91% DC but I have heard DM is on the high side. Heres one other thing I found while searching some site I forgot. The guy from FIC said this: "The 92 and 93 OEM injector was part # 17087325 a 22lb its grey. The 94 uses 17124248 a 24lb 12.8 ohm Black injector. I have found the 94 injector in many late 93's. Then in 95 gm used 17121068 black also and the same specs as the 248. 96 uses 17124251 again black with the same specs. So, who knows.. " I have a low mileage set of 17121068's too. In tunerpro the only thing I have for different injectors is the Flow Rate, and the injector pw correction vs battery voltage. Are those the only two things needed? Just find out the specs for whatever injectors I install and change those two things in the tune to match the different injectors specs? Thanks.

**gmpowered** · 05-10-2015, 05:17 PM

You should have a table for injector offset. (Low pulse width injector offset adder vs BPW.) Each injector has its own offset.
This table wont affect the tune as much as flow rate and PWvs voltage but is still important. It will change the VE fueling. "IF" the car was tuned correctly and you give the pcm the correct data that should be all you need to do.

http://www.lt1pcmtuning.com/tips/ He gives a snippet on it.

If you want to run a stock larger injector? That information should be easily attained with again a factory stock BIN.
If you want to run the ford injectors alot of injector sale shops will have them on hand. I know alot of that data is floating around as well.

Hope this helps.