Another 4.0L Supercharger Kit

[RedHeep]

$1,500 is about the price for a do it yourself stroker that can easily get a 60 horsepower increase. Which ends up being cheaper in the end due to not requiring extra electronics to run the setup.

That kit looks ridiculous. The manifold looks like it has the minimal amount of engineering into it with essentially a box connected to some box like tubes. The $5,000 cost is rather high as well considering the last of the Sprintex kits are being sold off for $3,150 plus around $500 of additional electronics the buyer has to supply.

Adding a supercharger is for those that really do not want to manage doing a drive train swap and keeping a list of what parts get replaced from what models of vehicles. I had to make a cheat sheet for my Comanche that lists all the vehicles that custom parts came from.

I was very interested in putting a turbo on my heep, but I can't fabricate an exhaust header and the one that was available was too pricey for me. If someone could come up with the parts and get a header that works, $1500 is a reasonable goal.

Of course, you still have to deal with engine management, but if it was easy, everyone would be doing it. The problem with all of these companies developing kits is that they're doing it for a very small consumer market and dealing with very high startup costs. It's just not beneficial to make money.

 

[GSequoia]

No photos on the site, just renderings. R&D consists of digital mockup, you get to pay $5k for an unproven product since you're the first one ever made.

 

[Talyn]

That kit looks ridiculous. The manifold looks like it has the minimal amount of engineering into it with essentially a box connected to some box like tubes. The $5,000 cost is rather high as well considering the last of the Sprintex kits are being sold off for $3,150 plus around $500 of additional electronics the buyer has to supply.

There is not much you can do with the room provided in an XJ. Longer runners would be nice, but at least it has a large plenum. Would be nice if it has a MP90. However, the price is ridiculous. One other thing is them mention the increase size of their fuel rail... however, the injectors on the fuel rail are not working any harder than stock and don't need the extra volume provided by a larger fuel rail due to the two extra injectors. $5k will buy you a very nice stroker.

 

[O-Gauge Steamer]

I do not see any reason for the fuel rail to be changed. I run the stock rail and have somewhat less than zero fueling issues. Bigger injectors do not require a bigger fuel rail. Spend that money on heat abatement material such as a header blanket and insulation for the underside of the manifold.

The lack of available real estate under the bonnet of an XJ is well known. If the compressor is to fit under said bonnet, then compromises must be made. This is one of the basic hardships of mounting a compressor in the XJ.

Can be done though, and done cleanly. See SolarBell's thread as he progresses with his installation of an M90. That fits under the bonnet.

Whereas I agree that a stroked engine can be purchased and installed for the same monies, the Heep does have to go into the shop for a number of days (weeks) to get the work done. A properly designed supercharger system can be installed in a matter of a few short hours. And is easily transferable to another vehicle should something catastrophic (roll over?) happen.

Ideally, the manifold that is on the discharge side of the compressor would have an internal volume equal to the displacement of the engine to which it is connected. We do not live in an ideal world. It is for this reason that I recommend that folk building their own systems to use a modified late model intake manifold. Greater volume. The smoother runners help under non boosted engine operation but are not at all required when under boost...

When I installed my system, I had thoughts of building an E85 fueled vehicle. Unfortunately, I ran into issues with offsetting the O2 sensor (9.6 for E85 vs 14.7 for gas) signal to the PCM which caused me to drop the project. But, as E85 was the goal when the injectors were purchased, I installed a set of 40 pound injectors.

At this point in time, you would be amazed at how sort the duty cycle is. Even under 8 pounds of boost near red line...

My recommendation for those looking to supercharge an early H.O. engine (think '93ish here) is to eliminate the variable pressure fuel rail and install a late model rail with a GM pressure regulator. It is near impossible to tune an engine that varies the fuel pressure...

Leastways, the '93 YJ I installed had this configuration. Can only assume all do in the model year range.

 

[MoparManiac]

If you have a vacuum referenced FPR on a MAP based EFI system, why can't you use it?

 

[O-Gauge Steamer]

With the fuel pressure constantly changing, adjusting the pulse width of the injector becomes extremely difficult to get correct. The aftermarket fuel and ignition controllers, are only capable of so much. Keeping the fuel pressure at a constant level makes it possible to tune easily. Worth the small monies involved.

IMO, the actual pressure is not critical. Most anything will do as long as it stays consistent and the injectors can flow enough fuel. Keep in mind that all injectors flow ratings are specified at a specific fuel pressure. Deviate from the specification and the actual flow will vary. This is, IMO, the issue with variable pressure and supercharger tuning.

Easy to tune with a constant supply, near impossible else wise. This opinion is based upon the issues encountered with the aforementioned '93 YJ. We were only able to get things under control once the variable pressure supply was replaced.

Can tuning be accomplished without a constant pressure supply? Maybe. But why fight it when it is an easy issue to resolve.

 

[MoparManiac]

Maybe I'm missing something but at high manifold vacuum, wouldn't you not need as much pressure to get the same amount of fuel as if there was low or no manifold vacuum? Assuming identical pulse widths.

To me it seems like the opposite of what you stated. It would be harder to tune without one since you now have to figure out what the engine needs at each load/rpm along with the different pressure heads.

 

[O-Gauge Steamer]

Well, let's take a look at that. In a normally aspirated engine under WOT conditions, the intake manifold has the air charge under atmospheric pressure which is elevation dependent. It is not, under "vacuum" at any point in time. The manifold always is pressurized to greater or lesser degrees. Unless, that is, you manage to launch your Cherokee into space...

For the sake of argument, let us assume sea level conditions (I am at 6,500' so things are different here...) The atmospheric norm is defined as 1 bar or, 14.7 PSIa where a = absolute pressure.

The fuel injector is then injecting the fuel into the intake port at the fuel pressure of the rail which in the late models is 339 kPa +/- 34 kPa (49.2 psig +/- 5 PSIg) Where g = gauge pressure. (Pressure values obtained from FSM for a '98)

Under boost then, the manifold absolute pressure is current atmospheric plus the boost which is to say that 8 pounds PSIg of boost is 22.7 PSIa on a "standard" 1 bar pressure day.

So then, even at relatively high boost pressures, the fuel rail pressure does not need to increase until and unless the manifold absolute pressure meets or exceeds rail pressure. In our example here, that would be 34.5 PSIg of boost to overcome the injector. Trust me on this one, you will have other, bigger, issues to tend with than fuel pressure...

The point you make about figuring the different "pressure heads" is, in fact, why the fuel pressure needs be a constant. Adjusting the pulse width of the injector cycle is easy IF the fuel pressure is a constant. You can see where it would be an issue else wise.

Personally, I use an AEM F/IC8 for my fuel/ignition controller and I program under the "percent" method. IMO, easier as one can prepare a simple chart by which to make the fueling corrections. I.E. the AFR (air fuel ratio) reads 15 then a correction of 2% to get to 14.7 is required. If, in this example, the cell in the FUEL MAP has a value of - 30% (fuel corrections are ALWAYS negative in value) then the new value for the cell is 30.2%

The F/IC is programmed in Manifold Absolute Pressure, not "boost" pressure.

With the fuel pressure changing, the correction values would have to float along with the pressure which is beyond the capabilities of any F/IC out there. Keep in mind here, the Factory eliminated this variable fuel pressure idea as it proved to be impossible to control emissions.

The Cherokee MAP sensor takes a snapshot of the current Absolute Pressure at Ignition On, Zero RPM. This lets the PCM know where in the fuel and ignition maps it need to start. It also defines shift points for the automatic. For those that do not know, the AW4 up here shifts differently than it does at sea level. Owing to the reduced power production, the transmission shifts at higher engine speeds to compensate for the loss.

Why is the fuel correction always negative? The norm is to install increased flow injectors. Therefore, one must shorten the duty cycle to get the amount of fuel injected back to stock. The only time more fuel is required is under boost conditions. Hence, the corrections will always be negative. If you think about it, it is easier to shorten the pulse width than it is to lengthen it. If it were possible to increase the pulse width, then the replacement injectors may not be required.

In absolute terms, this means that the fuel charge delivered is delayed, in time, from stock. Fortunately, given how slow things operate, this is not an issue at all.

So, in a nut shell, a correction value of -30% is only valid at a given fuel pressure. Change the pressure and the value must change. The Cherokee does not monitor the fuel pressure. It is assumed to be a constant. Which is why when the pump fails, no MIL (CEL) codes are set.

How different is the atmosphere here? My "standard" atmospheric pressure is 12.5 PSIa owing to the air density at 6,500'. The 8 pounds of boost I make here would be 9.6 pounds at sea level.

Hope that this clarifies things and does not muddy the water more than it is.

Cheers!

 

[MoparManiac]

Thanks for the response.

I was speaking more generally not specific to the 4.0 or boosted engines.

The megasquirt controlling my 440 reads a fuel map based on MAP readings on the fly and you plot the volumetric efficiency of the motor for that load/rpm. You can turn on or off the O2 correction which uses a separate AFR table to make small tweaks to reach the AFR you want for that load/rpm.

I can see what you're saying. Still not quite sure I understand it but I think I'm battling the flu so I'll check back later

 

[jeeperjohn]

Why does almost every supercharger kit out there use the roots type supercharger? Is it just that it is that common and therefore cheaper than a twin screw type? It seems to me the screw type would be far better for efficiency and cooler intake charge.

 

[RedHeep]

Whereas I agree that a stroked engine can be purchased and installed for the same monies, the Heep does have to go into the shop for a number of days (weeks) to get the work done. A properly designed supercharger system can be installed in a matter of a few short hours. And is easily transferable to another vehicle should something catastrophic (roll over?) happen.

I did my first engine swap in my driveway with no idea what I was doing, what tools I needed or how to get it out and put it back in on a Saturday.

While I agree that it might be more work, if you have the engine built and sitting on a stand, especially with how cheap a rebuildable core is, you can swap over to a stroker for about 3 more hours than what it takes to take the manifolds off and figure out how to bolt that mess up to the head. It's an engine replacement. Get yourself a few friends and you'd probably be done in a few short hours.

I'd rather do an engine swap on a saturday than I would bolt a supercharger to my stock engine and figure out how to make it work right every weekend for the next 3 months.

 

[SolarBell]

Why does almost every supercharger kit out there use the roots type supercharger? Is it just that it is that common and therefore cheaper than a twin screw type? It seems to me the screw type would be far better for efficiency and cooler intake charge.

Yes the twin screw runs cooler and with better efficiency. But the roots type are way cheaper and easier to find which runs typical for the XJ crowd.

I did my first engine swap in my driveway with no idea what I was doing, what tools I needed or how to get it out and put it back in on a Saturday.

While I agree that it might be more work, if you have the engine built and sitting on a stand, especially with how cheap a rebuildable core is, you can swap over to a stroker for about 3 more hours than what it takes to take the manifolds off and figure out how to bolt that mess up to the head. It's an engine replacement. Get yourself a few friends and you'd probably be done in a few short hours.

I'd rather do an engine swap on a saturday than I would bolt a supercharger to my stock engine and figure out how to make it work right every weekend for the next 3 months.

And after doing the math I'd rather bolt in a supercharger. I think it comes down to personal preference.

 

[jeeperjohn]

In a perfect world I would build for lots of boost and very high RPM. I would also use a crossflow head with a rotary tube valve setup. This is of course assuming I had been the one winner of the $600M lotto!

 

[kastein]

LS swap and / or stroker are cheaper for the power. The blower kit, though, is a Saturday project. Start with your morning coffee, have fun all night, buy new tires Sunday.

5 grand... You could get a full 5.3 / 4L60E & transfer case for 2000, say. Add 1200 for Novak's radiator, mounts & headers, 500 for gauges, we are at 3700 without driveshafts and only the obvious parts figured in. Then all the incidentals like getting the 4L60E & tcase to shift, the throttle cable or pedal install, the $75 worth of fluids (at least) and small parts... Not hard to drop a full 5K on the LS swap, I imagine, and you won't get it done on a weekend. So if it's your DD... No LS for you. Live in California? Going to be tricky to get that LS past CARB. They could ding you for anything from the gas tank to the cats to the air intake, fuel system plumbing, etc.

Stroker is a "well, maybe" - you could build / buy, get in under 5K (not hard) and install in a weekend.

Yeah, that blower kit is looking pretty damn good for the Jeep, much as I'd love to stuff a LS in there - 5000 for a Saturday project, especially with CARB stickers, is rad.

Around here I can pick up an LM7 w/ tranny and tcase for well under 600 all-in. Accessories, manifolds, ECU, all wiring, you name it.

Hell, I could have gotten an LQ4 for that a few weeks ago, if I hadn't been very short on both time and money at the junkyard.

That being said, I think turbo/supercharged 4.0s are pretty cool... not sure I like those SC intake manifold designs the renderings show, but I'm far from an expert.

edit: oh yeah, chevy tcases are passenger drop on some years. Make sure you have that included in your plans if you are thinking about a 5.3/5.7/6.0 swap instead of a supercharged 4.0 :spin1:

 

[yossarian19]

Around here I can pick up an LM7 w/ tranny and tcase for well under 600 all-in. Accessories, manifolds, ECU, all wiring, you name it.

Y'know, I was in Mass just this last November. I knew I liked the place and all, but damn... I've never seen a GEN III motor in a junkyard, much less a $600 LM7 w/ trans. That's awesome.
Around CA... $6-700 will get you a naked motor from the yards or maybe a dressed one with super high miles. More like 1000 dressed. I got a *score* on my 4L60E at $500, most were like 750.

As cheap as parts are in Mass, I can't imagine going forced induction, stroker or even a replacement long block for a 4.0. Used motor or LS swap, at those prices...

 

[CobraMarty]

Fuel injectors will flow fuel based on the 'pressure differential' at the tip of the injector.

A 20 pound/hr injector at 43psi will flow 20 pounds of fuel/hour when exposed to atmosphere. Vacuum (-psi) will increase the effective psi and flow more fuel and boost (+psi) will decrease the effective psi and flow less fuel.

With a static FPR, (constant fuel pressure) an injector in the intake manifold in a running engine, at idle with 16 inches of vacuum (= to about -8 pounds of vac) will see a pressure differential at the tip of 43psi - -8psi(vac) = effective 51psi and will flow more than 20 pounds/hr fuel at idle. At 0 vacuum(0psi) 43psi -0psi =43psi and it will flow 20 pounds/hr and at 8 pounds boost (43psi - +8psi(boost)=effective 34psi will flow less than 20 pounds/hr of fuel. So with the same 1 ms pulse width, a 20lb/hr injector will flow a different amount of fuel at idle, 0 vacuum, 8pounds boost with a static FPR.

With an intake manifold vacuum/boost referenced FPR which varies the fuel pressure-
an injector in the intake manifold in a running engine, at idle with 16 inches of vacuum (= to about -8 pounds of vac) will see a pressure differential at the tip of 43-8FPRpsi - -8psi(vac) = 43psi and will flow 20 pounds/hr fuel at idle. At 0 vacuum(0psi) it will flow 43psi-0FPRpsi -0psi = 43psi and flow 20 pounds/hr and at 8 pounds boost (43psi+8FPRpsi - +8psi(boost) = effective 43psi and will flow 20 pounds/hr of fuel. So the same 1 ms pulse width, a 20lb/hr injector will flow the exact same amount of fuel at idle, 0 vacuum, 8pounds boost with a vac/boost referenced FPR.

And yes a 20 pound/hour at 43psi injector will flow 0 fuel at 43 pounds of boost (43psi- +43psi boost= 0 effective psi).

 

[kastein]

Y'know, I was in Mass just this last November. I knew I liked the place and all, but damn... I've never seen a GEN III motor in a junkyard, much less a $600 LM7 w/ trans. That's awesome.
Around CA... $6-700 will get you a naked motor from the yards or maybe a dressed one with super high miles. More like 1000 dressed. I got a *score* on my 4L60E at $500, most were like 750.

As cheap as parts are in Mass, I can't imagine going forced induction, stroker or even a replacement long block for a 4.0. Used motor or LS swap, at those prices...

That's even probably overstated... one of the guys up here just got an LM7 w/ all accessories wiring and the stock trans (no tcase) for $370 iirc. It may have been $270, I don't remember. I learned a long time ago that the junkyard change their prices month to month on a whim though, so "under 600" is something I feel I can guarantee when telling people what they should expect to pay no matter what, with the actual price being a pleasant surprise most of the time.

It's a consolation prize for the fact that all our sheetmetal rots out in 10 years. We have so many good drivetrain donors with falling apart bodies/frames...