S/C Efficiency at 5psi...

Somebody is going to have to explain to me why 5 lbs of boost from one kind of S/C is different than 5 lbs of boost from another. Let's forget about lag due to piping.

Why?

Why is it different?

 

Centrifiguls have a lag down low. The make more power up top cause the impellers are at maximum rotation pushing air through the plumping...

Roots/Twin Screw have ZERO lag. The are Torque monsters and give you power NOW! No plumbing to mess with and are combined with the intake for better fuel flow...

I may be wrong or have not included ALL of the information. I will let someone with a better brain than mine chime in.

 

Ok, I read that link that Hal posted in the other thread. You got to spin up a centrifigul (like 3000?) before you get boost. That makes it behave a lot like a turbo (ick - twin screw for me please).

So I'm still wondering if 5lbs boost at low RPM is more stressful than 5lbs of boost at higher rpms?

 

Yes....Yes, Adam explained that the longer duration of boost throughout the rpm range causes more stress on ?????. Hope that makes sense! LOL

 

Kind of what JMatt proved to us that with his 3 stage N2O 275 shot. Some motors couldn't handler 150. He was able to add N2O as the RPM's increased because of less back pressure created by volume. The motor can push thru much more volume the higher the RPM, so the 5lbs of boost low is creating more cylinder pressure because it's pushing against less volume and slower moving air. I'm not sure I can explain this properly. So at lower RPM the supercharger is helping push the air thru. There is more resistance because the heads are not flowing enough air, thus allowing a strong push to artificially push more air into the cylinders, so we've crammed more air in creating more cylinder pressure which creates a heavier push on the power stroke which really is creating more torque.

At higher RPM there is more air moving, so the 5lbs of boost adds little to the faster moving air, or very little boost to the cylinder pressure. Kind of like a fart in a windstorm. LOL

I just confused myself.

 

It's pushing harder at lower RPM. That would be where the added stress would be because of the added cylinder pressure. I would think at higher RPM there would be less stress. Look at your torque curve, the higher the torque, the higher the stress.

 

Ah Dave you always ask the simpliest questions that require days to answer LOL

Now the basic answer is boost is boost, 5 lbs is 5 lbs whether a snail or a rotor blower produces it. (14.7 PSI atmosphereic plus 5 PSI =19.7 PSI, standard day 15 degrees C 59 degrees F 29.92 Baro)

Now comes the differences........

Snails traditionally make boost higher in the RPM band as stated above (centrificals just by their design get more efficient the faster they spin until captivation) or you spin them faster down below and relieve the excess pressure with a valve........

Rotors or Lobe blowers make boost as stated above (to a point that can be varied by pulley size and whether the blower is underdriven or over driven)

What lots of people fail to discuss and plan for (or even have a good engine design and understanding) is the amount of static and dynamic compression the engine has and the effect on the camshaft design verses boost level to make a huge difference in engine design and power output.

For instance a well designed blower engine will make better power (HP and Torque) at 4 PSI than a lousy designed engine will on 12 PSI

So is 5lbs stressful at Low rpms verses high RPMs'??

It ALL depends on WHEN the intake valve closes, thats when Dynamic Compression starts. ( I could go on for days on every engine if it runs pump gas can't go over 12.5-1 dynamic compression

I think alot of what we are seeing are big blower numbers on the dyno but the overall tuneability of the vehicle still suffers badly on the Chrysler stuff

Jeff

 

And that's EXACTLY what we wanted to know, or me at least, how much faster the Vortech kit made your car, or Jason's car that is. Nice guys!!

As for everyone saying get a better tune and such, eh, sure that's an option but you guys have basically reported before/after out-of-the-box results for the Vortech kit, thanks! I agree with Jason, 6K is an aweful lot for 1 car. As I said before, good write up guys!

 

Here is the issue with comparing Ricks to Jasons. Rick has a pro tune. You have to consider that in order to add the kit Jason gave up an aggressive tune, better shifts, and a lot of timing. These kits are tuned with safety as the #1 priority. Once this kit is tuned this will be a better comparison.

For example When we go WOT our timing is pulled down to about 3 degrees, then comes back to a max of 13. Now My car with a B&G pred tune was about 19-21. With timing comes power. Now Lance hit the nail on the head for a tune that when compared to a stock car makes 75-80 or so at the wheels more and will last the avg driver a long long time. However I dont think they were able ( due to CARB restrictions) to adjust the torque management, shifts, or anything extra.

If we all remember back to the pre predator days when Dave was getting 2-4 tenths from shifts and TQ management imagine what that equates to with the kit on. I know first hand my 2nd to 3rd shift takes what feels like 1-2 seconds. Its worse then stock. At the rates of speeds we are hitting on avg 1 tenth is about 3/4 of a car in a quarter mile. So if we gained back 2-4 tenths just from say tuning of TQ management and shifts well that could be 3 cars more. Now you dig into the fuel maps and timing...oh man im not going into that. Thats a tuners job

Also take a look at the 2 or 3 cars that have had the kits on and CMR tuned. I believe one maggy put down 550+ at the wheels. I would love to see the dyno sheet on that. I bet not only is his peek higher then mine or jason(the 2 so far from voretch with the best numbers) but I would bet that his curve comes up faster. I know rick is making more power earlier and this is causing Jason to have to play catch up. Catchup is only good on fries...I think, and please dont quote me, Ricks car made about 25-30 more then Ryans(he dynoed about 410 vs jasons 430 on a mustang) below 3000 or so. I didnt get to see both sheets from the day they tested.

So in conclusion to my longest post to date...Know that on a stock car these kits out of the box will put 75 more peak hp down and is warrantied for 3/36. Peak isnt all that its cracked up to be. Low to mid is where we spend 80% of our time. Once tuned for the way most of us will want it I think there will be a lot more then 1 car diff between these 2. Time will tell...

 

If seriously, the total commanded BTDC timing is only 3 degrees, and only 13 total IMHO that kit isn't even worth installing. That's deplorable for a supercharged engine.

Jeff

 

Ok all, I have taken some Q&A's out of MotherMopars Momo Vs Bud thread to

1) Clean it up

2) make sure that the GREAT knowledge does not get lost.

Thanks all.

 

Yeah the 13 degrees is low but consider this at 13 degrees its making 75hp more stock at peak. If tuned the possibilities are very interesting...once again give me some time and we will see what i can get from a pro tune

 

Here is my dyno graph...I have a twin screw SC..as ron had said the twin screw is a torque monster....of course this is a Viper engine so dont expect a Hemi to put out this much TQ (unless there are other mods) but it gives you an idea how the twin screw graphs....notice my truck never goes under 500FTLBs from 2K RPM to 6K RPM..

 

Regardless of pounds of boost, its all about CFM. How much air is the blower/turbo moving? A Paxton at 5lbs of boost will NOT be the same power as a Vortech at 5lbs of boost, everything else being equal. If they would give numbers in terms of CFM, that would be very helpful, but they really can't b/c when giving numbers in terms of CFM, pipe size and other factors come into play.

 

X2!!! I wouldn't spend that kind of money on a SC kit and only get those kind of results to get the 3/36 warranty out of it. A N/A stage II kit will give alot more bang for the buck IMO. Looks like all these guys with the Vortech's will need to get their cars CMR tuned to realize the potential of the SC and give up the 3/36 warranty.

 

John, once again, great post.

Enough said 'bout that!

Yeah, that's looking like the solution.

 

Lets not forget guys that this is CARB legal kit. So you'll be getting a CARB legal tune with it. I know that there are MANY who don't live in California, but for those of us that do the little yellow sticker (and passing tune) is essential for the long term.

The way I look at this kit is that you're buying hardware and smog-passing tune. If you're looking for maximum performance from the hardware, you should budget money for a CMR tune too.

This isn't a any different than when buying heads and cam. In that case, you're only paying for hardware (and maybe a base tune) and still need a CMR tune to get max performance from those parts.

To those who are upset about price. This is still a good deal. I paid 3500 or so for my heads and cam and got 75 RWHP. This kit costs roughly double that, but with a good tune you can also get double the horsepower. When you're talking motor hardware, nothing is cheap.

 

Totally agree John, I understand all that and agree, I'm not arguing any of that, lord knows I'm no expert on blowers. My point was Rick's and Jason's, what the difference would be after installing the Vortech kit on Jason's car. And now we know. Comparing to Rick's with the same mods Jason had BEFORE doing the Vortech kit is a good "real world" comparision and tells others of us out there with similar mods what we should expect "out of the box" with this Vortech kit. Seems almost like 2 steps forward, one step back to me, lol!

BUT I will say in Vortech's defense (not that they need it) Cali is Nazi-land when it comes to mods so for them to even attempt to get a supercharger CARB approved in this crazy GREEN state in this day and age is amazing! Cheers to Vortech!!



BTW RON, why'd you move my post (#8) to this thread? I didn't go off topic, I was complementing Jason and Rick for their "real world" test! I didn't go off topic at all. Hmmmm, punished for past crimes am I being?? Lol!

AND, your post on page 2 (#11) should be post #1 on this thread.

 

Oops. Sorry bout your post. lol

As for post 2 being post 1. Nope. As you can see in my post (#2 here) was quoting Quick. Quick was, in reality the one who began the questions. Not knocking Dave at all on the Off topic, just thought Dave started a GREAT discussion.

Rather than asking everyone to rewrite in a New thread, I made the feeble attempt to bring what was on the other thread to a new thread started by me. lol Make sense?

 

It also depends on charge air temperature. 5 lbs of boost at 77F charge temp is much better than 5 lbs of boost at 120F...all else being equal. Yes it is about CFM...but don't forget the density effect. The A/F numbers we all discuss are mass based.

Keith