Hey Guys, am looking for some opinions on how I should approach fuel. Admittedly, fuel is one of my biggest areas of weakness when it comes to knowledge of modifying the corvette. Was hoping a veteran of fuel could bring me up to speed on some considerations.

Background: Currently running an A&A kit v3 vortech with 3.6 pulley on 6 rib. I have forged rods and pistons with ultra low 8.6:1 compression also have fast 92 intake, ls2 tb, flp headers, ghl catted exhaust, ported 243 heads. I'm running on pump gas 91octane with an LPE 255lph in tank fuel pump with a boost-a-pump and 60lb injectors. Made 600whp/535wtq on my build.

On my current setup I was at 90% injector duty cycle, fuel pressure stays constant at 58psi during pulls.

Goal: I picked up a 3.4 pulley and anticipate I would be adding 1-2 psi. However I don't want IDCs to be at 100%, ideally would like a little headroom and be able to stay on pump gas at 91 octane.

Questions: For starters am I overthinking this, should my current fuel setup be enough? What is the cheapest option for me to hit my goal? Could I upgrade to 72lb injectors on my current pump? I anticipate by pulleying down, and installing new design air bridge which flows a hair more than my current air bridge power will increase to 635-650whp. Thanks for your help.

 

Upgrade injectors to 72 or even 80 lb/hr and go from there! Either way you're going to need injectors most likely, might as well just do 1 step at a time and see how it does. Edit: definitely just go for 80s... that should put you 75 ish duty cycle so that's perfect. I run 80s, runs and idles perfect.

 

Just for my own education and trouble shooting.... confirm you're not spraying methanol or anything?

 

Am not spraying methanol and don't want to in lieu of having a previous methanol failure earlier that contributed to blowing a motor.

What fuel pump and power are you running on your setup? My concern over upgrading to 72 or 80lb injectors is that my LPE in tank 255lph fuel pump will not be able to supply enough pressure.

I don't foresee upgrading the car's power level beyond the 3.4 for the next couple of years, not needing to account for headroom with further upgrades.

 

Yeah I ran WMI for about a year and the pump failed. I was troubleshooting issues the whole time so it got very little run time... I took it off.

I have a C6 style fuel system and at 4300' ASL so might not sync up exactly for your setup. Lingenfelter pump which is supposed to be walbro 450, and 80lb deka injectors. I have a BAP also.

I'm super conservative on timing still so my setup is probably not very power vs fuel efficient. But it's around 700whp corrected or 600-mid 600s uncorrected now.

Around 80 duty cycle, my biggest issue is fuel pressure drops to 52-54 by redline. If I could hold a steady 58-60 I could get quite a bit more out of this setup. Not sure if if it's losses in the fuel lines or BAP isn't activating or what.

In your case I see no reason to go crazy yet.... 80lb injectors, monitor fuel pressure and go from there.

I saw racetronix released a new single drop in high flow pump for your style fuel system. That could be a good plan B if your pump can't keep up.

 

Based off of what I've read (not seen or done personally), I would think you'd be ok only adding another ~20-40whp with the current fuel system. But if you don't want to run the injectors too hard, I'd personally jump to the 80s over 72s.

 

Get a set of 80’s to be safe. I have a used ECS stage 1 fuel system sitting around for the 97-02 C5’s

 

Hadn't looked up the ecs stage 1 system, sounds like it's in tank and good to 800whp. That coupled with some bigger injectors might be the cheapest path to enlightenment. I have an 01, so the kit should be compatible.

 

The ECS kits are external secondary pumps, mounted outside the tank that come on under boost. Proven to work and greatly increase the flow capacity. On an earlier C5 like yours no cutting of the tank too which is nice.

IMO it's still a little bit of a weird setup because you still have the fuel pressure regulator in the tank/stock pump...ideally you'd run a return line and put the regulator after the rail, but that adds more effort and cost.

If your pump isn't enough, something I'd look at is the new racetronix pump that's rated for 325lph @ 60psi. Your 255 is only rated to about 225 lph @ 60psi. It's a direct fit replacement. I think it's relatively new so you won't see many comments about it on here:

https://www.racetronix.biz/customkit...sp?kc=rfpk-052

 

Thanks for the suggestion, that looks like a really enticing option. This thread and other research has convinced me there is no way I can safely pulley down on my setup without making fuel changes. I'm at 1000ASL, when I was at 5600ASL in denver probably could have gotten away with my current fuel.

Famous last words... Am not planning on ever pushing my power level beyond the additional 2lbs of boost and power mods I have.

Would like minimal viable product in terms of cost to safely support the additional 2lbs and possibly running e85 on that configuration. Thoughts on if 80lbs injectors and this racetronix pump would support that, can't imagine hitting beyond 700whp? If the fuel upgrade costs went from 500-700 to 1500-2000 would likely forego looking into e85. Thanks again!

 

When I had my 04z with their stage 1 kit, my rail pressure would be at 60 since the pump was after the internal regulator

 

Sorry for late reply, been meaning to but kept getting sidetracked! I'm kinda in the same boat, I am at 4300' elevation and my fueling is OK, but I know if I descend too much I'm gonna have a bad time, plus I would love to run about an E30 blend to some extra knock protection.

80 lb injectors could support around 700whp, but only if it maintains pressure really well. And remember as you increase power... boost goes up, which effectively lowers the flow rate of the injectors. And for a given pump that is regulated at the tank, fuel pressure tends to also go down slightly as you start flowing more fuel. So you get to a point where your fuel pressure is a little lower than you'd like and higher boost pressure and suddenly your injectors can't flow enough. That's basically the scenario I'm in right now.

You can install a regulator at the rail and return line and now fuel pressure rises with boost and injector limits are much easier to predict. But raising fuel pressure will reduce the amount of fuel the pump can support....double edged sword.

E10 to E85 requires around 40 percent more fuel which is a ton. So you'd definitely be looking at external secondary pump, return line/regulator. Big price jump.

E30 is pretty common and gets you a lot of the benefits of E85 without massive fuel system requirements, or cold start issues etc....good compromise. E10->E30 is about 9 percent increase of fuel requirement.

In your shoes I would step 1.) get 80lb injectors. If you can maintain pressure, that gives you 33% more fuel flow should support 700whp again if you can maintain decent rail pressure.

step 2.) if fuel pressure starts to drop more than you'd like, get the racetronix pump and that should be enough for your goals, minus straight E85. Straight E85 you're gonna have to build a fuel system from the ground up basically.

Lots of options for us which is a good thing! You just need to decide if you want to keep your goals modest and go for the easiest/most straight forward path, or spend extra and give yourself a little more headroom just in case for later.

 

btw my personal thoughts on in tank replacement vs external secondary tank. I like in tank when possible-- external tank is going to be more susceptible to fuel sloshing around and not running lean in such conditions. Not a huge issue on C5s since its dual tank and even at 1/4 tank the left tank is still 1/2 full. But.... the bucket is the best for keeping a solid fuel supply. External adds a certain amount of complexity to the system but also makes it easy to add return lines etc. And of course you reach a certain point where an in tank pump just can't support what you need. The baller multi in tank pump setups are neat but get pricey quick. I'm going to stick with biggest in tank pump I can find and hope it's enough--it should be in my case.

 

I'd start with 80lb injectors and go from there. If you get a pressure drop I'd upgrade to a external pump at that point. We have some options for you at a great price.