Sprintex Extra Injector Setup

[Alexia]

I am reading the prototype instructions that were sent to me for this thing before I get started. I learned about the extra injector bit before buying and thought I would at least look into before going the route of just using larger injectors.

Using an extra injector to add fuel is not unheard of and Toyota TRD owners frequently do it with their setups. It is a nice setup since the little bit of air charge cooling it provides helps with intake temperatures. If anyone happens to know the difference the injected fuel creates in temperatures versus methanol/water please say something. Trying to search for that information on Google is impossible.

The directions say to only tap into the signal for the #1 injector. Which means the extra injector will fire only when the #1 injector does. Not when the rest of the injectors fire. So how exactly was that ever supposed to work correctly or efficiently?

If I really wanted to get into using that extra injector I could build a simple circuit with some diodes, tap into all six injectors, and have the extra injector firing with every cylinder. Though, that might over work the injector in the high RPM ranges.

 

[cruiser54]

There's a guy in Phoenix named Tom that supercharges Miatas and has worked extensively with the extra injector. Called a 5th injector. Since the injector is only gonna get energized when there's boost, I'm thinking it just needs a "duty cycle" signal from a factory injector. Fast Forward Superchargers. I just searched it.

 

[O-Gauge Steamer]

All Righty Then.

For what it is worth, here is my take on the "extra" injector concept.

In theory, there is absolutely nothing wrong with the idea provided that the injector pulses along with every other injector. The original Fuel and Ignition Controller that Sprintex provided with the kit was made by Perfect Power and used the extra injector. It was the preferred fuel delivery method by Sprintex.

There were issues with this controller. A list:
1) Only the Crankshaft Position Sensor signal was delayed.
2) The Camshaft Position Sensor was left alone.
3) The Throttle Position Sensor signal was hacked.
4) No provision made for the end user to alter the ignition timing.

What was right with the controller was that it fired measured amounts of fuel in a fashion that was not tied to any of the stock injectors. Long bursts instead of short ones which is what you get from being tied to a single injector trigger.

Let's look at what was wrong:
By only delaying the Crankshaft Position Sensor's signal, the engine would "hiccup" at any engine speed when the manifold transitioned from partial to positive pressure. This problem was resolved by replacing the controller with one that delays both the Crank and Cam Position Sensor signals keeping them in sync with each other. The TPS was hacked in order to "force the engine into Open Loop" operation. In truth, our systems are only in closed loop at idle or when the throttle is in stead state i.e. neither accelerating nor decelerating. The lack of being able to retard the timing is an obvious flaw. The only way to control detonation was to add fuel...

Intake charge cooling by the addition of fuel to the compressor's intake. IMO, this is a non starting idea as not enough fuel is added to make a significant difference in the discharge temperatures. Better to use the injector to add water/methanol. And at that, it is not the charge that gets cooled, it is the combustion chamber that gets cooled when the mixture flashes into steam. The steam not only helps to control detonation, it provides an increase in power. Don't take my word for it, look it up... Better to add an intercooler to reduce the discharge temperatures. Which is what all OEMs do.

When I replaced the Perfect Power Controller with the AEM F/IC8, I took a good, hard look at keeping the "extra injector" to add the required fuel as it would, quite frankly, contain costs. I was not then, nor am I now, convinced that sending a relatively large slug of fuel into the system and then hoping the mixture will be even across all 6 cylinders is a chase down a rabbit hole.

I was not willing to risk my engine to this method of fuel delivery. As it turned out, a full set of injectors turned out to be rather reasonably priced on Amazon.

Keep in mind that my installation is the second longest one in the CONUS. I work with the good folk at Sprintex to help develop markets and to provide ongoing data on the performance of my system. I regard these people as my friends and as such, I am biased towards their products.

I have found issues as well as opportunities for improvement. The issues they resolved and the opportunities they are considering implementing.

To my mind, the system is an easy installation and the tuning is completely dependent on the controller selected. Timing is best set with a knock sensor installed for tuning as the engine will be in detonation long before you can hear it.

 

[old_man]

If your injectors are sized appropriately, you can probably get by with adjusting the MAP signal. It is an easy to alter the ratio. I can dial mine wherever I want. If the engine starts running hot, I just crank it up a bit. At high altitudes, I can dial it back a bit. The ECU and MAP normally handle altitude just fine, but they were never designed to work at 14k ft.

 

[O-Gauge Steamer]

No reason to mess with the Factory MAP signal as the OP has an AEM F/IC installed that has it's own MAP Sensor capable of reading boost. He just needs to get the fuel and ignition tables correct.

Truth be told, tuning the supercharged 4 Litre is a walk in the park provided the injectors are sized correctly. The OP would need to visit the Gauges Window to see what the duty cycle is for the currently installed injectors. From there, the decision can be made on the need to go bigger and by how much. All depends on how much room is left for the injector to drive.

IMO that is...

 

[bpas328xii]

The TPS was hacked in order to "force the engine into Open Loop" operation. In truth, our systems are only in closed loop at idle or when the throttle is in stead state i.e. neither accelerating nor decelerating. The lack of being able to retard the timing is an obvious flaw. The only way to control detonation was to add fuel...

I've played with my XJ a lot both before and after the S/C install... From what I've found, the TPS does not override closed loop. Why Sprintex tried to modify it is beyond me.

I did find, however, that the MAP sensor overrides closed loop and immediately snaps the ECU into open loop when provided a voltage that corresponds to about 0psi vac.

Keep in mind that my installation is the second longest one in the CONUS. I work with the good folk at Sprintex to help develop markets and to provide ongoing data on the performance of my system. I regard these people as my friends and as such, I am biased towards their products.

Who's the first? Haha.

I have about 15,000 miles on my Sprintex install and haven't had a single problem with it. I agree, they made a great hardware kit.

I am reading the prototype instructions that were sent to me for this thing before I get started. I learned about the extra injector bit before buying and thought I would at least look into before going the route of just using larger injectors.

Using an extra injector to add fuel is not unheard of and Toyota TRD owners frequently do it with their setups. It is a nice setup since the little bit of air charge cooling it provides helps with intake temperatures. If anyone happens to know the difference the injected fuel creates in temperatures versus methanol/water please say something. Trying to search for that information on Google is impossible.

The directions say to only tap into the signal for the #1 injector. Which means the extra injector will fire only when the #1 injector does. Not when the rest of the injectors fire. So how exactly was that ever supposed to work correctly or efficiently?

If I really wanted to get into using that extra injector I could build a simple circuit with some diodes, tap into all six injectors, and have the extra injector firing with every cylinder. Though, that might over work the injector in the high RPM ranges.

If you're going to use the 7th injector, I recommend you use the plug-and-play FTC from Split Second that I use. Works flawlessly and pulses the 7th injector 6 times per engine cycle.

 

[O-Gauge Steamer]

The first installation was into the Boostec Shop Jeep. I removed the original prototype and installed the current version. In the original version, the compressor sat dead vertical (as opposed to the angle it now sits) and the notches at the bottom of the manifold, used to clear ratchet extensions, were not there. That version of the manifold was a bear to install. The current version is easier than the stock manifold to install...

As Boostec is no longer associated, in any way, shape or form, with Sprintex the installation status of that compressor is problematical at best. Last I heard, RR was attempting to sell of the Jeep. For way too much money given the condition. I know for a fact that it was repeatedly overheated. Apparently, RR believes that as long as the coolant is not boiling out onto the ground, it is not overheating. Well, that is one way to look at it...

bpas. You are correct in that the TPS has nothing to do with the engine being in open/closed loop. You are also correct in that the MAP sensor will cause the engine to go into open loop when atmospheric pressure is detected.

Note that I do not say 0"Hg. At engine start, ignition on zero RPM, the PCM takes a snapshot of the MAP Sensor voltage to determine a couple of things. Firstly, the starting altitude which is needed for the ignition and fuel tables and to set the voltage at which the PCM will go open loop during acceleration.

The PCM works in PSIA or Pounds per Square Inch, Absolute. Thusly, the average manifold pressure that the PCM uses to go open loop, here, is 11.5PSIa owing to the altitude at which the car lives. Me too now that I think on it a bit... As a comparison, at sea level, it would be 14.7 PSIa or, 101 kPa.

A good friend of mine worked for Chrysler and it was he who clued me in on how the PCM works.

Sprintex was relying on Perfect Power for the fuel and Ignition control so used PP opinion on how to control open/closed loop. What neither companies realized was the the PCM goes open during acceleration. Modifying the TPS signal only confused the issue...

Good to know that the Split Second will trigger the extra injector the proper number of times. Had I known, could have save a couple of bucks on my installation...

For those with the Sprintex compressors, please remember to change to oil every 30,000 miles at the latest. As my compressor was off during the 68mm TB installation, so I changed to oil then.

 

[SolarBell]

For those with the Sprintex compressors, please remember to change to oil every 30,000 miles at the latest.

I'd guess that is a good recommendation regardless of the make of supercharger.

 

[Talyn]

It is. I don't know what fluid the Sprintex uses but the stuff in the Eatons is some of the nastiest stuff I have smelled when its worn. Its worse than gear oil.

 

[Alexia]

I asked around some of my racing friends and others about fuel cooling the intake air charge. I was given some data to show if the fuel is injected right before the compressor intake it can cool the charge up to 25%. That is only the intake manifold air temperature though. Obviously methanol/water mix injection performs better due to its other effects inside the combustion chamber.

I did a bunch of calculations to estimate the discharge temperature after the compressor. The typical average discharge temperature at 6 PSI of boost should be around 178F at 110F intake temperature. At 145F intake the discharge is 227F. This is calculated using the stated 84% efficiency from Sprintex's data sheet. The 145F intake temperature was recorded on a hot Alabama day for my current setup while moving about 10MPH. Kenne Bell recommends no more than 280F discharge temperature.(See section labeled "HEAT".) Kenne Bell's 10F per 1 PSI of boost calculation is lower than stated with the Sprintex.

So as long the air box intake is not pointing at the exhaust and the intake manifold is properly shielded it is not a huge concern to get the initial air temperature down running the stock. It would be better off having an AEM F/IC setup controlling six larger injectors and utilize the extra injector in the intake manifold for methanol/water injection. That way the AEM can be setup in dual calibration mode easily to have the extra tune for methanol/water injection.

 

[O-Gauge Steamer]

Alexia,

Good summation. And I must say that I completely agree with your proposed methodology. Now, that could just be due to it is how I installed my setup...

Although the extra injector method of fuel delivery works OK, I feel that for the best in fuel delivery, larger injectors will be needed. What size injectors are in the engine now? Do you know what maximum duty cycle is? If it is low enough, you may get away without having the change the injectors.

If your intent is to only use the extra injector for water/methanol, I would like to suggest that you make a new fuel line to replace the Sprintex supplied one as the connection to the extra injector is neither required nor desired. This is something I need to do with mine, just have not gotten around to it.

It will be interesting to see how well your rig runs once the compressor is installed and alive.

Fair warning here...
You will be getting the occasional odd look from people due to the sounds the compressor makes. Especially from the Ricer Crowd. To my mind, the compressor makes a pleasant sound. The sound of power you might say.

 

[Alexia]

Unfortunately I can not edit my post.(Urgh!) Marty pointed out I made my calculations in the wrong units.

Using the correct calculations 110ºF intake would be 231ºF discharge and 145ºF intake would be 304ºF discharge.

Sprintex's data sheet shows nearly a consistent 151ºF(55ºC) temperature rise across the entire RPM range. With their official numbers that would make 110ºF intake be 261ºF discharge and 145ºF intake be 296ºF discharge.

So with the corrected calculations and able to actually get my hands on the proper data it actually shows that getting the air charge cooler would be important for power, but not necessarily for proper operation. The first item that I will be doing is to make sure cool air is coming from outside the engine bay.

The original photographs and designs for the Sprintex TJ kit actually had an extra injector in the discharge manifold. It did not provide any charge cooling by injecting fuel before the compressor intake. The release version does not have the hole drilled in the manifold and relies entirely on upgrading the injectors. To me that says the designers at Sprintex are not too worried about discharge temperatures.

 

[O-Gauge Steamer]

It all revolves around the expected boost levels. Sure, it would be very nice to be able to drop the discharge temperatures but keep in mid that, for the most part, the Sprintex kits are designed to deliver 6 pounds of boost or so.

At 6 pounds, you can get away with the discharge temperatures as they are.

What I can say is that were I to go for more boost than I am currently running (8 pounds at 6,500' about 9.6 pounds sea level) the Jeep would require an intercooler. This project is on hold for now but I do have some ideas bout how to stuff around 12 to 14 pounds of intecooled boost into the Heep...

Of course the Sprintex S5-210 compressor is incapable of providing that much boost when fitted to a 4 litre engine.

Alexia, contact your Sprintex Dealer and get a quote on a 54mm pulley. To install it, you will need a 0.064" shim to set between the pulley and the compressor drive. The spacer is needed to accommodate the two offsets involved. Sprintex has pulley shims in stock. I had mine made at a local machine shop for $10.00. The existing bolt can either be shortened or a new one sourced. I elected to shorten the bolt which means a replacement will have to be sources if the original 58mm pulley is ever to be installed.

With your stroker, you could use a bit more compressor.

I documented the 54mm installation on mine, the thread is here somewhere...