Fuel System

Let’s talk about the fuel system. 

I’m going to start with the fuel system problems that I was looking to overcome.

The stock 2G fuel tank sucks for drag racing.  The pickup is toward the front, its plastic so you can’t weld a sump in it, there’s no drain and to top it all off, it’s a saddle tank with a siphon cross over that becomes a restriction at high flow.  Yes, I know there are Band-Aids for some of these things but they’re all Band-Aids. 

Next is type of fuel.  For Drag Week I need to drive 1000 miles on the street and race for 5 consecutive days.  93 octane pump gas isn’t going to get me to my goal.  E85 would certainly get me there but the route is not provided until the day of and E85 stations can be hard to come by.  It’s not practical to bring along enough E85 for 1000 miles plus racing, although some do it. 

Fuel tank size, for this much street driving, I wanted something in the 15-20 gallon range and putting a fuel cell in the trunk at that size is kind of crazy.  Then swapping fuels at the track with a tank that big could turn into a nightmare. 

Switching between 93 octane on the street and E85 at the track has its own set of challenges.  E85 requires quite a bit more fuel than 93 octane.  So I’d need very large fuel pumps and very large injectors to handle the E85 and they most likely wouldn’t drive all that spectacular on pump gas (although Fuel Injector Clinic 2150’s do decent on 93 considering how massive they are). 

Then there’s methanol injection (meth is a drug, methanol is fuel we use in race cars, this is a pet peeve of mine).  The conventional way of doing methanol injection is to use an irrigation pump never designed to be used with corrosive fuels, a crude solenoid and some irrigation nozzles.  I’ve tuned these systems plenty and they’re never consistent, can’t be tuned for all conditions because of the delay in the pump turning on, etc.  Sure, you can make power with them and some people have luck with them.  To me they just aren’t the proper way to do it though so I avoid it on my personal stuff and I avoid tuning cars with them for the most part. 

So no onto what I decided to do.  This is a fuel system I’ve wanted to do since like 2008 when I was tuning an Evo on Methanol injection regularly and dealing with the headaches above with inconsistencies and whatnot. 

Run an 8 injector setup, 4 primaries on 93 octane pump gas.  Then a set of 4 secondaries on a completely different fuel (in my case E98, although I might try methanol at some point, it’s just some scaling in Haltech to make a change). 

So how did I do this?   I kept the stock tank and all of its headaches.  I installed a Walbro 450 pump in the stock location.  This pump is overkill for what I’m doing but I decided to go 450 for head room in case I wanted to do something different in the future.  I have the rest of the fuel stuff (feed/return/filter/rail/etc) to support big flow so I might as well.  I installed the Walbro 450 in the tank and transitioned the stock sending unit to -8 AN line.  I installed Fuelab filter in the engine bay, then continued -8 AN to the rail.  In the rail I installed a new set of Fuel Injector Clinic 650cc high impedance injectors (PN: IS126-0650H).   These injectors can support just over 300 whp on pump gas at stock pressures.  They can be pushed further for sure but this is the safe area.   From there I went -8 AN to a Fuelab AFPR, then -6 AN back to the tank.  In the tank, I drilled out the siphon (I forget the exact size but I used information I found here on Tuners to decide). 

So that’s my primary fuel system.  93 octane, Walbro 450 and a set of 4 FIC 650cc hi-Z injectors.  Fairly normal and easy setup.  That’s going to make drivability of the car pretty awesome, but it’s not going to get me into the 8’s.  Probably not even the 11’s for that matter. 

So now onto the secondary fuel system.  I found a ~2 gallon fuel cell that fits next to my roll cage behind my drivers side rear wheel well and mounted that.  It has 2 -10 AN outlets on it standard, so I ran both of those to a pair of Bosch 044 pumps.  Those two pumps exit in a pair of -8 AN lines to a Y that also exits in a single -8 AN.  That goes to a fuel lab alcohol-based fuel safe fuel filter mounted under the car.  From there I continued the -8 right up to my secondary rail.  In the secondary rail I have a set of FIC 2150 Hi-Z injectors (PN: IS126-2150H).  FIC rates these at over 900 whp on E85 and 58 PSI fuel pressure.  From the secondary rail, I go to a second Fuelab fuel pressure regulator with -8 AN line.  Then from there I have a -6 AN return line all the way back to the top of the fuel cell in the back. 

In this system, I plan to run VP X98, which is just the most readily available E98 that I can get here.  I’d use any E98 I can get but I was having trouble finding anything and running out of time so VP X98 it is. 

So here’s how the controls work.  Haltech is setup on gasoline and the FIC Data Match data is plugged directly into the Haltech software for the 650’s.   I literally plugged this information in, guessed at some VE values for my combination at idle, set target lambda to 1.0 and the car fired and idled perfectly.  Data Match technology is awesome for that, you know exactly what you’re getting and if your software is advanced enough, you can plug that information right into it.  

The secondary injectors are a bit trickier.  Haltech (and most tuning software that I know of) don’t offer options for injecting multiple types of fuel at the same time, so I had to trick it.  93 octane stoich is 14.7:1.  VP X98 is 8.98:1.  I have the exact data match data for each injector and that’s what I used in Haltech but I’m going to simplify the math here and just do it for 2150 cc’s.  So now I multiply 2150 cc * 8.98 / 14.7 and that gets me the “effective” injector size for these injectors (1313 cc’s) for the Haltech Software.  This doesn’t mean the injectors are flowing 1313 cc/min. It means that Haltech thinks its injecting gasoline so it’s going to calculate fueling according to a stoichiometric ratio of 14.7:1, but it’s actually injecting pure ethanol.  I’m fooling the system into injecting more fuel (by the proper amount) to account for the stoichiometric difference between the two fuels. 

I could have done this opposite and set it up for E98 in the haltech software, then put the 2150cc Data Match Technology data right into haltech and setup the 650’s as:  650 * 14.7/8.98 = 1064.   This would have accomplished the same exact thing but I decided to do it the other way. 

I’m also running the 2150’s at 58 PSI of base pressure so I had to do this all for 58 PSI.  I have all of this data direct from FIC on the Data Match data sheet but if you need to do the math, it’s SQRT(New Pressure / Old Pressure) * Old Flow Rate = New Flow Rate.  2150’s flow about 2480 at 58 PSI for reference and then with my fuel type modifier, I entered about 1516 cc per injector. 

Okay, enough math, I didn’t actually describe how any of this is controlled yet.   The primary fuel pump (Walbro 450) and primary fuel injectors (FIC 650H) are all wired to the Haltech as a normal fuel system would be.  The 450 is on an output switch through a relay and setup as the primary fuel pump.  It primes at key on, turns on with the engine, etc.  The injectors are wired to the first 4 fuel injector outputs.  This part is as basic as it gets. 

The secondary fuel pumps are wired to another output through a high current relay (80 amp I believe to be safe).  This is setup in Haltech as a secondary fuel pump and I can customize how/when it turns on.  I haven’t messed with this too much yet, but I can turn it on based on fuel flow, load, etc.  It’s up to me.  My ultimate plan is to calculate at what injector flow rate I want the secondaries to turn on and enter a fuel flow number lower than this for the fuel pumps so that they are already on and primed before the secondaries turn on. 

The FIC 2150H’s are wired to the second 4 injector outputs.  These I have turned on when the primary injectors reach a set injector duty cycle.  I haven’t messed with these settings much yet but I can allow the primaries to get to say 50% duty cycle, then the secondaries will start phasing in.  In a split second the secondaries and primaries will match duty cycle and I’ll be injecting the same duty cycle worth of E98 and 93 octane. 

So, what’s that mean for fuel mixtures? It means that I’ve now mechanically defined my ethanol content by injector sizing.  At full fuel flow, I’m injecting approximately 650cc of gas and 2480cc of ethanol (per cylinder).  That means ~26% of my fuel (by volume) is gas and ~74% is ethanol.  AKA I’m running about E74 under boost. 

All of this means I can pull up at any gas station and fill with 93 octane and keep cruising.  I need to bring E98 with me, but I should use quite a bit less than half a gallon of E98 per run, meaning one 5 gallon pale of E98 will get me over 10 passes down the track.  It also means that the way I drive the car from track to track is exactly how its raced power wise.  If I was so inclined, I could roll into the power whenever I want and it’s all setup exactly as at the race track.  

Obviously, this is quite a bit more complicated than just adding an irrigation pump and a nozzle into my charge pipe, but I like the math and figuring it all out.  Plus, I like that I know exactly what is going on with the whole system and have full control over it, which is what this setup affords me.  I’ll probably mess with different fuels in the secondary injectors eventually.  It’s just simple injector scaling as I mentioned above for a fuel change.  Fairly straight forward. 

Okay, that was a lot of words, hopefully I answered most questions.  Feel free to ask away.  Let me show some pictures of this whole setup. 

Just some of the components as I get started
Twin Bosch 044’s Mounted
Secondary Fuel Cell Mocked Up
FIC 650H Primaries
FIC 2150H Secondaries
Fully installed and wired