I would like to have a technical discussion on superchargers. More specifically, I would like to entertain a discussion on kits, more than the blowers themselves.

I'm not interested in discussing the merits of going forced induction, or comparing superchargers to turbochargers. Nor am I interested in comparing a roots kit versus a centrifugal kit; for the purposes of this discussion, let's assume we're talking about centrifugal blowers. Lastly, the purpose of this thread is not to compare existing kits on the market; let's not compare ATI versus Vortech. Let's just assume that there aren't any kits on the market, and we must construct our own.

So - let's start at the beginning: the blower. I recently received literature from ATI. I happen to prefer ATI headunits to the vortechs just because a buddy of mine ran one on his 2000 Mustang GT for a number of years, and I like the fact that most of the ATI units are self-contained.

The ATI specs table is available here: http://www.procharger.com/models.shtml. The unit that ATI uses for its G35 kit is the C2. The headunit included in the kits for the 3 valve Ford 4.6's is the P-1SCx. Months ago I jokingly suggested to my friend that he sell me his headunit when he took it off his car. He stated that it wouldn't be a good match for the VQ35 because of flow and the required power to drive the unit. On the surface, this makes sense. However, the same headunit is included in ATI's kits for ford's 3.8 liter v6 mustangs.

Why is the C2 used in the G35 kit instead of the P1SC? Is the C2 simply a better mate for smaller displacement engines? Is it a question of the efficiency range of the blowers versus the redline of the target engine? Which unit would be best suited for the 7500rpm redline of the new HR motors?

Let's stay with the build-it-yourself theme. Assume we've selected a blower. What's left? A mounting bracket must be measured, fitted, and fabricated. Then one must cut the piping and select an intercooler. Somewhere one must decide on the pulleys and belts to use. What about a bypass valve? I know the Vortech kit includes a BOV. What purpose does it serve in a S/C kit? Is it included to prevent compressor surge? What would be an alternative; i.e., how can the problem of compressor surge be solved without the use of a BOV?

That about fuel management? Let's assume we don't have any kind of piggyback or tuning; we can't pull timing or adjust MAF offset. Where does that leave us? One could upgrade the fuel pump. What else?

What exactly is the FMU included in the current ATI or Vortech kits? I don't mean the split second box; it's my understanding that the SS box is a discreet part from the FMU. Is the FMU just some sort of rising-rage pressure regulator?

It's this last aspect in which I'm most interested. Fuel. At what point is an upgraded pump necessary? At what point are larger injectors necessary? At what point is tuning necessary(timing and MAF offset)? If one runs a sufficiently large pulley for low boost, at what point does timing and fuel become a concern?

 

I would think it is all about packaging. The P series is 2 inches in diameter larger than the C series. And what do you get for the two inches? The C series can boost up to 24psi, the P up to 30, but MOST stock block G's don't go over 8 or 9 pounds. The stock compression ratio is too high. A 3.5 liter V6 will almost never push the limits of either blower.

I guess one advantage of the larger P series is that you could run a larger pully on it and spin it slower since it can move more air. Maybe make less heat. Not sure if it would be worth the effort.

This also explaines why the ford V8 and V6 use the same blower. The V6 isn't too small for it and the effort required to make a new mount for the smaller blower was not worth it. Space isn't a problem under a V6 mustang hood.

JH

 

In the Vortech application, the SS box pulls timing and controls fuel. ATI got a bad rep with the VQ in the early years due to no timing solution. A lot of guys tried running the kit without any timing retard.

 

If you are thinking of taking the blower from your friends mustang and building a kit from scratch . I would think it would be cheaper to by a used ATI kit from some one and modify it to be safe by adding a fuel system and a EMS . To build it from scratch will be costly .

 

Sounds about right.



You need to vent that additional boosted section of pipe or risk going lean and compressor surge. You can go without it at your own risk.
The other popular option is doing a recirculation valve.

What is your issue with the BOV? Sound? Looks? You can somewhat hide one and then run a flex tube down under the car so it is not too loud.



Yes the Vortech uses an FMU and a spit second box. The stock pump should get you to ~350whp, maybe more but why risk going lean for $100 part. The stock injectors can be maxed somewhere around 400whp but it's not safe to run them at 100% duity cycle when you can just put in some RC 440's.

You can do a custom flash on the ECU to create a timing map for your install but again why not just go aftermarket with a SS, Unichip, UTEC, etc?



My UTEC kicks in at 3psi, below that it runs like stock. With how fast the twins spool up it is only under 3psi for a very small amout of time.

Remember the base JWT kit comes with stock injectors and I believe also uses the stock pump. With the right tune you can get a lot out of it.


IMO for whatever it's worth, go with a ATi or Vortech kit and call it done. By the time you do all the work, spend all the time and make all the parts you are going to have spent way more than a kit would have cost you.

 

Since the blades on the blower aren't variable, the blower will be sized/designed for maximum blade efficiency at a certain flow rate (boost @ engine rpm). In other words, you're going to want to pump the air you need for a certain amount of flow (boost) at a certain engine rpm jwith the fewest losses and without stall. Every compressor (blower) has a characteristic performance map that you'd use to tell you which is the right one for your application.

 

I'm not going to build a kit. I was just joking with my buddy when I made that suggestion. However, the suggestion did get me wondering about the components of a kit. This thread is more of an abstract discussion, anchored by examples of current real world kits.

 

I'm not opposed to a BOV. I was asking about alternatives merely because I'm inexperienced with FI kits. I assumed that a BOV was more functional than just being a sound piece.



I already mentioned in my response to booger that I'm not building a kit, and I'm also not buying a kit. This is more for my own edification than anything else. However, if I did, I'm covered on the timing front because I already have a utec.



At this point, I'm most interested in timing and fuel. I'm particularly interested in the fuel aspect. I see the term FMU thrown about, and I understand it's meaning as an acronym, but not an implementation. What exactly is an FMU? Is it a rising rate regulator, or is it a supplemental tool in the fuel system?

Let me put it this way. Cheryl get's her 07 the first week of May. At this point, there isn't any kind of piggyback solution. So, for the sake of argument, how would one go about constructing a kit for a platform as new as the 07 sedan? I'm not about to do so. I'm just trying to educate myself.

 

A FMU is a fuel management unit , it allows fuel preasure to rise with boost . It allows you to keep stock injectors and supply extra fuel . The BOV that Vortech uses is bybass BOV . ATI uses a recerculation valve .

 

An FMU measures vacuum. If you open your hymnal to chapter 'carburetor', you'll notice some had vacuum secondarys. Also a FMU. An engine creates a vacuum signal at idle, so many 'bar'. A measurement of air pressure. Just revving the engine doesn't change that signal, but when the engine revs under load, in gear, it does change. Thats how the secondarys in a carburetor or the FMU in a supercharger system know to add more fuel.

Since the ECU is reading the O2 sensors many times a second, if the FMU goes a little over/under board, the ECU fine tunes the fuel mixture it controls. The FMU is just a close guess, but the two work together without really knowing it.

Bonus answer. The old 'double pumper' carbs had mechanical secondarys. Imangine you put an extra fuel injector on your intake that started spraying fuel as soon as you passed 1/2 throttle no matter what. That would be a double pumper.

JH

 

http://www.vortechsuperchargers.com/...p=31&cat_key=5


here is the Vortech FMU...it is a seperate unit from the rest of the system

 

I dont know where you got your info from , you maybe talking about something totally diff. Or maybe the FMU that Vortech uses is diff. from what your talking about...lol dont know ?????

 

I've been wondering why I haven't seen any Z's or G's running a diverter valve. Is the ATI's recirculation valve the same thing then?

 

No, I'm talking about the Vortech FMU you linked to. There are three ports on it, fuel in and out on the bottom and a lone port on the top. That takes the vacuum signal from the engine. As vacuum is created, the fluorosilicone flapper or whatever it is opens up inside the FMU allowing more fuel (higher pressure) to flow to the injectors. The reclibration kits listed on the linked page are just different springs and flappers that change the fuel flow relative to the vacuum created by the engine.

It's a crude system but it works and nothing better has been developed.

JH

 

OK...but you are still a little off . The fuel preasure doesnt rise with vacuum . It rises with boost