Preparation for the STILLEN supercharger

RCZ

You can do it with less than 10psi.

You are getting mixed up with spooling time vs. size of a turbo charger when looking at that graph. A sc's size has nothing to do with when it spools, it is mechanically driven, so what you want to talk about is power delivery and the ramp effect of the gearing within the scharger.

Easily explains it? The similarities with a turbo is in the way power is delivered. Since it is a compressor wheel, it will compress more air the faster it spins, like a turbo would as it spools up. That's about where the similarities end though because there is no hotside wheel that needs to be spun and spooled by exhaust gas...There is no lag, there is only RPM/Size/Gearing/wheel design.

stormcrow

So, then why not tout the PSI? What is the big secret? BTW, I don't see getting a 10psi kit past CARB. Vortech has already done it with some of their T-trim blowers, IIRC.

Really, what are we looking at here? More or less than 8psi? This question can be answered without giving away the 'trade secret'.

Are you kidding? Of course an SC's size has to do when it spools. Bigger compressor wheel, less CFM at lower RPM. Hence the reason why you can change either the pulley size that drives it OR the compressor size, itself, to change key aspects of air delivery. It really doesn't matter if drive is coming from a belt or from exhaust. Key physics do not change.

Analogy - A bike wheel spun by a chain and crank. The larger the wheel, the slower its rotation at a given speed of crank spin. Change to a smaller wheel and what do you get? Faster spinning wheel. Now imagine these wheels are compressor fans...which is going to produce more CFM at a constant lower speed or as the RPMs ramp up? The truth is, it takes the larger Vortech more RPMs to push the same CFM as the smaller compressor of the Rotrex at lower RPMs. It's not a huge amount, but definitely significant enough to show the differences in torque. The plus side of this? More power to be had when running higher boost as the larger blower will not run out of steam as quickly.

And, I don't think anyone at Stillen would disagree.

RCZ

Hmm, You change the pulley to change the multiplier effect of the gear size differences and therefore the speed at which the compressor wheel is moving. Higher speed will yield more boost as long as the turbine wheel is within its efficiency range.

Changing the housing would be like getting a different trim and thats the same as getting a whole different supercharger.

You made your post sound like you were talking about spooling when you said "full spool". I don't know if you know this, but spooling refers to the amount of time it takes air exiting your engine to spin up (spool up) the exhaust turbine on a turbo. You are talking about a supercharger spooling? It doesnt spool, it spins up and down with engine speed. That engine speed + gear ratios between the crank pulley and the sc's pulley is what creates a certain speed in the compressor wheel. You are right about one thing though, the housing does affect the way power is delivered because different sized compressor wheels have different effects, speed being the same, with relation to their size. I didnt say it didnt, I said it doesnt have a difference on the "spool" of it because it is belt driven.

The size of the compressor wheel has no bearing on its speed. OK yea the tips of the blades are spinning faster because they are traveling more distance in the same rotation, but thats not what we are talking about here. Whether the compressor wheel is 2 inches in diameter or 4, its still spinning at a certain RPM that is produced by the gearing size differences in the pulleys. A bigger wheel should in theory move more air at the same RPM as a smaller wheel, granted I think each size probably has a different peak efficiency speed, I don't know, I didnt study turbines or fluid dynamics in college. Remember we arent changing the compressor wheel size when you upgrade, you usually change the pulley size to increase the multiplier effect and speed up the compressor per a given RPM and therefore making more boost. That is why bigger housings make more power, because they can move more air per rpm than the smaller housing. In other words they make more boost per rpm. You would only move up in housing when you have maxed out the efficiency zone/speed of the smaller housing.

You even brought up turbos and you are confusing the size thing with the SC. The turbo's are the ones that will produce boost quicker when they are smaller, but thats not because of the smaller compressor housing, its because of the smaller size of the hotside that needs to be filled up and spun up with exhaust air. The smaller that is the quicker the shaft spins up the quicker the compressor builds boost.

stormcrow

I actually think we are both speaking about the same thing here. By "spool" i meant reaching optimum RPMs to produce Xpsi. Granted the word is more befitting the turbo application, but SCs do spool. Given it is by motor RPM and not exhaust.

My point is that given the pulley and compressor size differences between the Vortech blower and the Rotrex of the two competing kits, the torque curve differential is explanable by the amount of CFM moved at lower RPM ranges by each. Again, no one from Stillen has responded stating that I am incorrect.

That said, I am still waiting for Stillen to respond to the PSI levels and why it's so important to keep them from the masses until a "Press Release." This is a bit confusing. I am also waiting for a response on whether or not Vortech has ever released a kit running 10psi or better that was CARB legal. (I already know the answer to this one)

Kyle@STILLEN

We will release our boost number, in our press release. It's not like we think we have some magic amazing boost number. Obviously it's above 4 pounds and below 10. We just prefer to announce that number in our press release.

To be honest, I have absolutely no idea how much boost Vortech has used in some of their previous kits. That would be a question for Vortech. Keep in mind this is not a Vortech kit...This is a Stillen kit utilizing a Vortech compressor. All of the engineering, testing, and development has been done by Stillen.

G Fo12ce

No magic number, no sale. Every Stillen S/C should include a magic # in the box!

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G37Sam

Nice, we're getting there.. is it above 7 and below 9?

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G Fo12ce

FAIL lol. He can still get you with decimal points, now he can answer with between 7.1 & 8.9.

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stormcrow

Kyle, as much as I appreciate your candor, I still cannot grasp the reasoning behind not stating the actual PSI used to reach 422whp. I, as probably does everyone else reading this thread, understand that the boost level used to reach this number may change with the release of the kit. Whether it goes up or down in the production kit isn't as important to me as knowing what PSI was utilized to create the dyno posted in this thread. Again, I cannot fathom any legitimate reason (but, I can certainly think of plenty of illegitimate ones) why this number has not been posted. It truly does leave those of us (well, at least myself...I hate to speak for others) on the fence about which kit to utilize wondering what Stillen has to hide.

If you can give me a logical reason for waiting for the press release to state PSI after having posted a dyno chart, I will be satiated. Until then, I will probably continue to pose the same question over and over again.

And I understand this is a Stillen kit. But, you quoted another member here on their reasoning behind why 10psi would not = CARB legal. I see this as you insinuating that this is the reason why 10psi or better was not used to reach the horsepower shown in the posted dyno. I am not comparing your kit to the Vortech kit. I am merely stating that 10psi can pass CARB and I honestly do not buy that your dyno pull posted was done on anything less. It it was less, it was certainly more than 8psi.

The reason I am so verbose in my questioning is due to having been promised the world by Stillen salesmen when I researched and purchased one of your SC kits for my now sold Pathfinder. What I was sold and what I received were two completely separate items. Not physically, but in quality and performance. Having been in this game for quite some time, I am looking for complete transparency from vendors.

Speaking of tranparency, keep in mind that whatever PSI is posted in the 'Press Release' will have to reproduce 422whp all day long or people will feel duped.

Kyle@STILLEN

There are a few reasons why we have not released what PSI that test was at. The primary reason for releasing the dyno without boost numbers to follow was simply to show the capabilities of this kit without even pushing it hard. I assure you, that dyno was performed at less than 10 psi.

The main reason we do not want to release a horsepower figure in relation to a boost level is because the car we were testing on (G37 auto trans. with large 20" show wheels) was less than ideal. We are currently in the process of switching the kit to the manual gearbox 370Z with stock wheels which should be improved due to its more efficient drivetrain. It is very possible that running less boost on our Z will produce the same numbers that we saw on the G and people would say but wait...the horsepower is the same but your boost is lower...So, rather than having any confusion at all, we are switching to the more efficient car and from here on out will stay with the Z.

Also, that was a prototype run...Look at the date on the dyno, that was back on the 19th. Since then we've changed our prototype charge pipe and a few other pieces.

All we wanted to do was show the early development of the supercharger to show that it has more potential than the VQ35 supercharger did. Again, we were running less than 10 psi, and we are doing all of our tuning on 91 octane pump gas.

When we have our finished production kit we will have a finalized dyno showing the horsepower of the kit and of course we will list what psi we are running. Right now, it's too early to confuse everything until the kit is completed.

In regards to running 10 psi on other Vortech kits. I don't know why Vortech chooses to run 10 psi. I assume it's because they feel that the engines can handle it pretty safely. Perhaps it's because the compression ratio on the Mustang GT is only 9.8:1 which is significantly lower than the compression ratio of the VQ37 at 11:1

I agree with you completely. The percentage gain between the base test and the final test after installation of a supercharger should be the same as the manufacturer's after taking everything into consideration. To say that the final rear wheel number should be at least identical I can't really agree with because there are a lot of things that need to be considered such as elevation, air temperature, transmission, wheels...But yes, the percentage of horsepower gain between baselines should be relatively similar.

Phimosis

I know it has been suggested by others on this forum before, but Stormcrow, can you please stop being offensive with every post, or just don't post at all?

Thanks,

-Phim