When to upgrade fuel system

**1998 T/A** · 02-12-2015, 01:30 PM

I'm going to be upgrading heads and cam, mods specifically are fast 92, pacesetter LT's and ORY, TSP 233/239 and 220cc as cast heads with 62cc chambers. I have read some debates that say the stock fuel system is good for low 400 rwhp, meaning injectos fuel rails and pump will be fine but will I gain from upgrading these areas? Also I did the air egr delete and the back of my fast has a tiny vacuum hookup I have no clue where it goes because from my understanding the delete got rid of all those small vacuum hookups on the back of intake. Car is 00 ws6

**0rion** · 02-12-2015, 02:11 PM

Don't you have to run different rails anyhow for the fast? I would say that you're going to be over on injectors too with that set up. I forget right off hand if '00 had 26's or 28's. I want to say they had 26's but even with the 28's you're going to over I believe. I have 28's in mine with a 228R cam and I'm right at the edge. If it were my car I would plan on doing it all including the pump.

That small line goes to the small line for the a/c vents inside the car.

**1998 T/A** · 02-12-2015, 05:19 PM

26# and the fuel rail hooks right up. I'll upgrade it just wasn't sure what the rule of thumb was.

***SMWS6TA*** · 02-12-2015, 05:24 PM

I had to use LS2 fuel rails

**0rion** · 02-12-2015, 05:29 PM

Originally Posted by SMWS6TA

I had to use LS2 fuel rails

that's kinda what I thought....I thought because of the height of the fast intakes you couldn't use the stock rails. I see now though he has the 92....maybe I'm thinking of the 102's like you have.

As far as your injectors you can use hptuners to check the duty cycle....you want it no more than 80% but with 26ers I can pretty much guarantee you that you're going to be well past that with that set up.

***SMWS6TA*** · 02-12-2015, 06:18 PM

Also it depends on the injector style. EV1's you need spacers and the new style you don't. It all comes down to how tall the injector is, FAST 90's aren't that much more bigger than the LS6 intake. What 5-10mm at the TB opening?

I have no idea what GM was thinking putting 26's on these cars.

That small vacuum port s for the HVAC system. You need to connect it if you want to use your AC/heater and be able to switch between defrost and vents.

**1998 T/A** · 02-12-2015, 07:00 PM

I got ya...I'll have to check out the fitment...new fuel rails will look good but if I don't have to spend the cash right now that'd be nice...all the install videos and other things I've seen the ls1 fuel rail fits right on the intake. I'll have to check it out on my next day off.

**pajeff02** · 02-13-2015, 03:06 AM

You won't necessarily "gain" anything as the engine only wants the amount of fuel the PCM commands (with the tune adjusted to accommodate your new components). However, as posted, you do not want to max out your stock injectors or exceed their duty cycle and risk having things go lean in the upper rev range. You have a Racetronix pump out back?

**35th-ANV-SS** · 02-13-2015, 05:16 AM

There is a pretty straight forward formula for calculating what size injector you need based on a few inputs.

**1998 T/A** · 02-13-2015, 06:15 AM

Originally Posted by pajeff02

You won't necessarily "gain" anything as the engine only wants the amount of fuel the PCM commands (with the tune adjusted to accommodate your new components). However, as posted, you do not want to max out your stock injectors or exceed their duty cycle and risk having things go lean in the upper rev range. You have a Racetronix pump out back?

Stock pump fuel rail and injectors...it seems like just upgrade it so I don't have to worry about it am I right?

- - - Updated - - -

Originally Posted by 35th-ANV-SS

There is a pretty straight forward formula for calculating what size injector you need based on a few inputs.

What's the formula??

***SMWS6TA*** · 02-13-2015, 08:11 AM

Injector Math: How to Calculate Optimum Fuel Injector Size - OnAllCylinders

cool I don't need to get new injectors

**pajeff02** · 02-14-2015, 04:36 AM

Over time the stock pump does get weak. Throw a pump and a hotwire kit in it and you'll be good. Not a bad idea to have a fuel pressure gauge plumbed into the rail as well. I run a fuel pressure gauge in the A-pillar pod.

**jb3golf** · 02-18-2015, 10:49 PM

1998 T/A for now and if you dont have the cash....just invest in a good fuel pump/wiring system....The sstock injectors in our 98' motors can handle a ton of fuel, but you gotta get that fuel to the rails. ..My 98 forged block with AFR 210 heads and LSL 227/231 cam +92 fast/ram air and full exhaust set up was tuned and the stock injectors were fine...my tuner shown they were around 92% duty cycle and were performing great throughout the Revband....and there were no changes either at 7,000rpms......is it the best scenario injector wise? No..but you should be good to go based on my experience and feedback from one of the best tuner's in AZ....hope this helps.

**jb3golf** · 02-18-2015, 10:52 PM

Originally Posted by 1998 T/A

I got ya...I'll have to check out the fitment...new fuel rails will look good but if I don't have to spend the cash right now that'd be nice...all the install videos and other things I've seen the ls1 fuel rail fits right on the intake. I'll have to check it out on my next day off.

Zero issues with stock fuel rails installed. ..nothing to worry about here....just make sure that hvac line is hooked up! Take care