^ I think you will enjoy this site and the smart members contributions. It is a great reference for some of the more technical aspects of car ownership. I’ve learned quite a few things here and am thankful. Not to say that I haven’t pciked up other useful information on other forums, I just happen to like the collection of shared info here.
Here is an older article that logged fuel cut on an '08 below 8100 rpm.
http://www.europeancarweb.com/tech/proven/epcp_1002_2008_audi_rs4_b7/
[quote]Last, although the car is advertised to have an 8250-rpm rev limit from the factory, the dyno showed fuel cuts out just under 8100 rpm.
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It would be interesting to see just what the code actually says. I haven’t tried bouncing the rev limiter in mine (still intimidated by the lofty redline, and the lofty engine price).
Thanks! (I appreciate the qualifier, LOL!)
Cant share much technical info but i remember driving an S2000 for a few weeks…
I felt like i was riding a bike. It felt like each gear kept going and going and at first you really do think your going to blow the engine. The noise is so different up top that it feels like something is wrong… but it isnt.
It would be interesting to see just what the code actually says. I haven’t tried bouncing the rev limiter in mine (still intimidated by the lofty redline, and the lofty engine price).
Thanks! (I appreciate the qualifier, LOL!)
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Nice find.
Would like to hear from count vohn n this topic. He works at the performance division of ford, SVT
looks like sherlock is on the case and he’s uncovered a few “facts”…
[quote] Originally Posted by mickf29
Got to ride in one of the AMD high pressure kits car tonight. Wow. Unbelievable. I also learned a few more things. Like the reason the JHM centrifugal systems are running 8k redline is because the blower will nuke itself above that. Love how the debate was pointed at how unreliable the AMD kit will be at 8500rpm redline, when in fact the real issue is the centrifugal blower on JHM car that limits at 8000. So of course the fanboi section twisted the info to make the lowered redline a positive, and the higher redline a negative, when in fact engineering designs are limiting the centrifugal supercharger from turning faster safely. Also the AMD kit make sa ton of boost at all RPM ranges. The centrifugal does not. This AMD car is going to be a 10.x car on pump gas. The issue they are working now is the traction down low. Its really difficult to launch this without clutch feathering to keep the wheels in traction.
“The biggest drawback of the centrifugal supercharger is it’s inability to make high levels of boost at low engine rpms. Typically, a centrifugal supercharger will make it’s maximum (quoted) boost at the engine’s redline rpm and nearly nothing at 1500-2000 engine rpm. Boost builds exponentially with engine rpm, meaning that boost comes on very quickly in the upper half of the powerband. While this normally isn’t a problem for lighter cars with manual transmissions, it poses a significant problem to heavier vehicles, towing vehicles, or vehicles with automatic transmissions.”
Funny how idiots here will make crap up just to reinforce their allegiance to a specific manufacturer. Just be honest about the data, instead of going jspellingbee on us and making more crap up that pretty much everyone here sees right through.
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:o :o :o
What is he talking about lol.
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How would he know what Jhm is spinning the Vortech to?
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He said he got a ride in one of the amd hp cars? There’s only one lol.
Mick just loves to prove he is a Jhm hater who knows very little about any of this. I’m so glad he sold his rs4 and downgraded.
Didn’t know we need a lot of power at 1500 rpm. Whenever I’m racing my RPMs are never below 5k unless I launch which I launch at 3k.
Yeah, Mick is
a) not so smart
b) being fed bad information
c) fat
This is a great article…
http://www.vortechsuperchargers.com/page.php?id=749
Look at some of the points they bring up about how roots type systems claim they are a better setup.
[quote]Some manufacturers will attempt to mislead or confuse shoppers by using the term volumetric efficiency instead of adiabatic
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[quote]Some are eager to point out that the roots type supercharger will make boost [pressure] at very low engine RPM1. This is true; they make more boost than a centrifugal at low speed and less at high speed, but this feature is much less helpful than it would first appear.
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…and this quote at the bottom of the article sums up my argument with Mick’s dumb ass!
[quote]So, when choosing a supercharger system: Do you want power, or do you want a decoration?
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Let’s have a look here.
First, the supercharger is driven by the RS4 4.2 FSI engine. A belt wraps the crank pulley, and also wraps the supercharger pulley. The smaller the supercharger pulley, the higher the RPMs the supercharger reaches. If the pulley was 1:1 size wise with the crank pulley, the supercharger would spin to whatever RPM the engine spun to. At redline in the RS4, that is 8000 RPM. If the pulley ratio was 2 to 1, the supercharger would spin to 16,000 RPM while the engine spun to 8000, but that is before the internal gearing step up of the supercharger. Makes sense?
The stock crank pulley vs. the JHM SC pulley (S4 shown). It’s really not a small pulley. They are using a large pulley to keep the RPMs and boost down on the kit. This pulley makes 6 PSI of boost on the S4 kit. The RS4 kit makes 8 PSI.
http://jhmotorsports-sucks.com/wp-content/uploads/2011/03/XGuQN-550x366.jpg
Simply put it’s not anything crazy small. It’s big. Apparently the RS4 pulley is just about the same as that one, according to a couple of people who have seen it. Hopefully JHM chimes in at some point.
So when we hear mick the fat fucking retard say things like this:
[quote=mickf29] I also learned a few more things. Like the reason the JHM centrifugal systems are running 8k redline is because the blower will nuke itself above that.
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Interesting. It seems that when he drove in woodi’s car (I believe there is only 1 AMD big boost supercharged car) Mick was in Seattle at AMD’s one man shop. Because Mick lives in Oregon, that’s kinda weird. But let’s pretend he was indeed. So he is getting information from Jason @ AMD about JHM’s kit, and then posting it in threads the next day? Nevermind that this is incredibly pathetic, but let’s break down his claims.
JHM is using a Vortech supercharger. If that RS4 pulley is a 1.33:1 ratio (looks like the SC pulley is about 75% of the size of the crank pulley)
at 8000 engine RPMs that means the blower is spinning at about 10,640 supercharger RPMs x the step up. The stock step up on the Vortech V3 Si is about 3.6. JHM uses a proprietary internal gearset though. So we’re just guessing now, but let’s guess with the stock numbers.
10,640 x 3.6 = 38,304
At 8500 engine RPMs, that would spin the supercharger in the JHM kit to about 40,698 supercharger RPMs.
At 9000 RPMs (why not) that would spin the JHM supercharger to 43,092 RPMs.
According to Mick, going beyond 8000 engine RPMs would ‘nuke’ the supercharger. Let’s see what Vortech has to say about Mick’s theory
Vortech posts max speed at 52,000 RPM and max boost at 22 PSI !!!
UH OH! Mick looks dumb again, and is caught in more lies.
The JHM kit on the RS4 wouldn’t even come anywhere near that at 8000 RPM unless their proprietary gearset creates a step up rate of 4.88 (it doesn’t) . It wouldn’t come near 52,000 RPM at 8500 engine RPM unless their internal gearset step up rate was 4.59 (it isn’t).
To put it another way, using the JHM pulleys and the stock Vortech V3 Si, JHM could spin the RS4 4.2 FSI engine to over 10,0000 RPMs before the blower was at Vortech’s maximum.
Anyone who says JHM is running the blower to it’s max at 8,000 engine RPMs and any higher would nuke it, needs to go and eat a shit and broken glass burrito. They’re just straight trollin’.
Mick is officially busted again for his campaign of lies and hate against JHM. What a disaster this guy is.
Don’t we already know that CV limits the throttle body on the Stage 1 S4 kit to make less power as the RPMs climb?
So for him to say things like this only make him look like more of a fool.
A guy like CV isn’t going to grenade anything by making a novice mistake, I’m sure if anyone understands this setup…it’s probably one of the guys that helped design it.
Mick is being force fed bullshit by AMD clowns…the only thing JHM will be grenade are the feelings of AMD supercharged cars.
The blower unit has an internal gear ratio as well (the blower pulley spins a gear which then spins another smaller gear, look at the offset between the pulley and the impeller shaft on the business side of the blower) so you can achieve proper impeller speeds without an excessively large engine:blower pulley ratio so the math isn’t as direct. Not to discredit your point, as I’m sure CV can do the math to ensure their is headroom for the blower. The point mick was trying to make sounds like classic hearsay from competitor.
http://www.aacorvette.com/performance/images/vortech_cutaway.jpg
I was lucky enough to help install one of the first prototype blowers with CV. He had to WAY detune the motor on the B6 to keep the motors together with this blower. If you look at the supercharger guys there throttle is closeing at 6000 to limit boost from the blower. I know he does other things to help kick out boost.
Justin does the kit use anything else to limit/set boost? Just curious since you have a lot more hands on experience with it
Ahh good point. I saw that on a discussion
Unless that gear up is close to 5 to 1…which it absolutely isn’t… the point still stands. If we can find what the gearing is I will edit my example. Along with actual pulley size.
EDIT: I added in the calculation for the STOCK step up for the internals of the Vortech V3 si blower, however JHM uses a proprietary gearset. Stock step up is 3.6: 1, which even at 9000 engine RPMs (lol) would only put the blower at about 43,000 RPMs, leaving another 10,000 RPMs on the table.
The thing is… the the blower was nearing its RPM limit at 8000 engine RPM, it would be really struggling to make much power at that point, the air would simply be way too hot. Don’t have a compressor map to compare, but I would imagine that you would be running along the surge line at max RPM as well.
This jhm stage 2 kit that went 11. 34 in early testing (they are nowhere near finished and have already made more passes) is probably making barely 500 whp. That blower will keep pulling like a train up to 650+ whp. This (current levels of 8psi and about 900 CFM) , is nowhere near the edge of efficiency.
Exactly… far from almost being “nuked”.
d) a and c
All the math adds up to what jhm has been saying… 8lbs of boost 900cfm is about 500whp a few jave mentioned jhm talking about the stage 3 is 13+lbs of boost that would put them at close if not over 600whp and close to 1200cfm… more empty talk and bs from amd…amd for tue record cant even get the specs for there kit right how in the hell are we suposed to listen to them about anyother kits. …