Ok, I need some help with fueling direction on my Paxton SN2000 on my 5.0 tpi. Mostly stock except for 3” catback, dyno don headers (soon) and water/meth injection with stage II progressive controller.
I having been reading thru posts on this site and other sites and I am thinking of four options and hoping some of you can provide input/suggestions. I haven't found a clear answer.
Option 1- Use existing 19lbs/hr injectors and use FMU with boost control to boost pressure from 43.5 to 63psi- to give 22.9lbs/hr (283 HP) =22.9*8*.85/0.55
Option 2- increase injector size to max size (maybe 27 lb/hr) that stock pump can handle (40gph*6 lbs/gal)/0.55BSFC=436 HP and new tune
Option 3- increase injector size to 30 lbs/hr and install new inline or intake pump and new tune 371HP=30*8*.85/0.55
Option 4- meth injection- can this compensate for fuel i.e. inject methanol at elevated boost levels- my current max boost is 7.54psi- if enough methanol is injected are larger injectors needed??
I would like to make the changes once and then get the engine tuned with correct air fuel ratio. I am confused why the people at Paxton did not recommend fuel upgrades when (not even fmu's) when they sold these kits. I would hope/expect that their experts would have done some research to ensure the engine did not not go lean under boost (and cause potential law suits). Feel free to correct me and I would appreciate more direction…….

 

Stock pump and injectors have no business being in the same sentence as "supercharger"

Several inexpensive upgrades are readily available, such as the ford color topped injectors and a walbro255 pump. A boost referenced AFPR should top off the system

While you can overcome fueling issues with methanol, you would be wise to build the fuel system to support your goals and use methanol as a safety net

 

First step is get a walbro 255 in tank fuel pump, this is more then enough for a stock.

If you're willing to learn how to burn your own proms 28lbs injectors are a good start and worked really well when my car was mostly stock with the procharger.

 

Is there anyone who can give any input on methanol injection as fueling supplement

I will purchase a racetronix walboro kit but I still don't see the issue for a stock pump from a theory perspective. Is just practical the no one has made a stock pump work?

I spoke to a tuner and he suggested 42# and walboro. The 42 seems like way overkill for my car-

Any suggestions are appreciated

 

Size your injectors based on projected power on the powertrain combo

 

How much BHP does it make now without the supercharger? How much boost will you run and what is max RPM?

 

Stock LB9 with headers and 3 catback so I am guessing 225 HP

The sc produces 7.54 psi at about 5000 rpm which will be my max rpm

 

I run basically the same setup. Stock LB9 with Ford 30#/hr red top injectors, stock GM TPI fuel pump, turbos with 10 PSI of boost. Running that setup for about 5 years in a truck.
It makes around 360 BHP on my setup.
215((10+14.7)/14.7) = 225*1.68 = 360 BHP at 4800 RPM
295((10+14.7)/14.7) = 225*1.68 = 495 ft-lb at 2800 RPM

225((8+14.7)/14.7) = 225*1.54 = 350 BHP.
stock GM TPI pump and 30#/hr injectors would do it at a minimum. All depends if you ever want to upgrade cam, heads, etc. If you upgrade then you need the Walbro 255 and 42#/hr injectors.

 

Do you have a custom chip?or is stock?

Any idle issues assuming you have stock ecm program

Thanks for your help

 

Works fantastic as long as distribution in intake is good and you dont run out of meth Soon as pump fails or runs dry, it goes boom. If distribution is not good, one or more cylinders will not be operating in a safe zone and you can have issues. Wont know unless you have monitors on all cylinders, ie o2's and EGT's, plug reading constantly....


IF you cant upgrade to a 2 bar map system like code $59 and burn your own chips, you will want to do an FMU. Need to size based on your hp potential. If you run 7.5 psi, I dont see you makin over 350 hp so possible 19 lb injectors can work here but your driving fuel pump hard. Not good for a stock pump, and a walbro 255 will handle way more hp than you will achieve so do the upgrade.

I'd look to find a cheap 24lb setup and FMU, tune from there. I dont like FMU's as I dont like having to jack up fuel pressure to provide fuel but they can work well enough. For you simpler setup, and lower boost, play with the FMU.

Also, you can kinda tune Power Enrichment vs RPM for centri chargers.... boost rise is pretty linear to a point so as boost comes up RPM's go up, fuel goes up. Pretty straight forward.

Now you just need to control timing. 4-5 degs should be pulled atleast. Boost referenced ignition box timing retard function should be looked into if you dont go to a 2 bar map system. Mallary 685 type box or MSD equal would work well. Program 1 deg per lb boost as a starter.

 

It is a custom MAP chip.
Fuel and timing curve for turbochargers is much different than supercharger. My curve is very non-linear.

The best plan if you don't want to do a custom chip is to do what Orr mentioned. Replace fuel pump and install FMU. If your car is MAF then you can probably tune chip for boost because it is SC and not MAF CFM limited.

For timing either tune chip, install timing retard, or put in Cadillac HEI module with 10 timing retarded actived by hobbs/pressure switch.

 

the minute you switch out your injectors, your going to need a tune.. fmu or not, procharger usually supplies a walbro 255 inline to work with the stock pump when using an fmu, i use water/methanol injection to cool the intake charge, the methanol "fuel supplement" is a bonus.. i would not depend on it.

 

a SN2000 maxes out at 800cfm.

An inline boosted pump and FMU with stock injectors would be just fine for that small blower.

-- Joe

 

So im guessing this would be the same with my wifes 91 z28 350 tpi with a Paxton SN92 with about 6-7 psi..i do have a walbro high pressure boosted 255 lph..with a ATI adjustable FMU...which im waiting for the parts so I can rebuild it...she does have bosch-3's 22 lb injectors plus we added a south bay adjustable regulator too...I did install an AEM air fuel gauge..i also for quick check hooked up a autometer fuel pressure gauge mounted to the wiper..lol to see what psi I get with the FMU im looking for 11.5 A/F ratio.. hope this works.

 

I think it was High Performance Pontiac who put a procharger on an LB9 powered 'bird. Procharger tunes that system with an FMU. The stock injectors were shutting down before 10lbs of boost.

 

I'm sure. He doesn't have a procharger, he has an SN2000. Those blowers won't make 10psi on a ford 302. They are about the same as an old Vortech A-TRIM. They make a stock L98 put down around 400hp.

-- Joe

 

Thanks everyone for your input

I am going to try 30# injectors, walboro pump and a new chip from tpichips

 

I just did a high volume 255 lph walbro in tank pump...and a voretch FMU...with 22 lb injectors being its a 350 car...Air fuel is in the mid 11s with boost fuel pressure holds and is in the 80s...yes i know an FMU isnt the best way but for now its working...

 

haven't the injectors locked out- i read somewhere that max pressure is 72.5 psi and then the injectors lock out........

 

I think it would be more like 90-100 psi they would lock out...I have seen guys say they run up to 90 psi...im going to either swap out the disc to an 8-1 that should bring the fuel pressure down...And the Air fuel should still be decent....that's the main thing right now...

My wife just added that they aren't the stock injectors there Bosch 3s...so maybe they can take more pressure....

 

Update
I have my 30# injectors and chip from tuned performance

To get a baseline before I change the injectors I. Measured the AFR. I just want to make sure the baseline numbers make sense

1000rpm- 14.9
2000rpm- 15.2
3000rpm-15.3
4000rpm-16.7

All these numbers are under no load. Any input is appreciated

 

Were you in boost? if so that's not good...also even in no boost you should be at least in the low 13s to 12s in boost I would like to see mid 11s...at least.

 

Yes paxton was hooked up and running

 

How much boost are you making..i have my wifes car set up old school with an FMU and an adjustable Fuel pressure regulator and I have a walbro 255 lph fuel pump...made for boost. and when running boost my air fuels are in the low 11s on the rich side...im going to try to tune with meth injection next..i think I can get it better...

 

If your talking about just reving in your driveway then yeah they seem fine though a little better explanation on what you were doing would help.

 

Yes reving on the driveway in park- so do these afr's seem correct - I just want to make sure everything is properly before I change my. Injectors

 

i still think that's a little lean but that's stock injectors?...you didn't install the 30s yet ?

 

Correct 19's installed now. So the lean afr's seems correct for what is installed now? I am now afraid to drive under load assuming my afr will go leaner under load? 30,s will be installed in about a week

 

The 30s should help what fuel pump you using?....do you have an adjustable FPR too?....like I said I have my wifes car running 22 lb injectors and running a 255 lph fuel pump But I have the FMU uping the fuel pressure and AFs are good...actually spot on...is this the right way no does it work kinda...im going to tune with a snow performance stage 2 meth kit I think that will run better...