Stock Fuel Rails, why they don’t keep up

[16GoManGoHC2]

Ready to ROCK!! Now I just have to wait until later as it’s 96° outside. I ain’t going out in this shit no matter how much I want to hear it scream lol

 

[2fast4u]

Looks like a little over enthusiasm on the top right, hope it doesn't introduce much turbulence when it hits the lip...

 

[16GoManGoHC2]

Looks like a little over enthusiasm on the top right, hope it doesn't introduce much turbulence when it hits the lip...

The over enthusiasm was to open it up enough to take a 108 which will be the next dyno test

 

[2fast4u]

^^ understood that, just noticed the over removal right at the edge where it mates to the billet plate. Right top appears to be maybe a 32 further than perfect mating...saying it could cause turbulence in an otherwise smooth stream.

 

[DavidKFla]

I was told with my baby tune that the fuel rails are sufficient for my use. I'm right around 780-790 to the rear wheels. This is on the stock single pump.

 

[fumanchu182]

20HP is probably right. It's a small gain and lines up with a 5mm change in TB size IMO.

If this is the third Litens that has failed, something is going on. I know you're super detailed, but have you made sure the pulley is properly spaced from the snout? The snouts are cast and can have some variance. I've heard of some of these pulleys dragging on the snout and it kills them. Outside of that, it sounds like the 10% lower may just be putting too much stress on the pulley. I'm a huge fan of the decoupler Litens pulleys for these IHI blowers due to the gear set setup we've talked about before, but your pushing some boundaries and need another solution assuming everything is setup correctly. You're not running an additional idler or anything right? That's said to kill these Litens pullleys as well.

I think this is an understatement. After seeing about 23 PSI from a 2.70 and a 10% lower the car was just not right. Bypass valve closed, running out of fuel, etc. Here is a post from Jokerz about combo pulleys meant to help the community.

Hellcat superchargers and pulley combos.
I have to start off with saying this is not modding advice or guidance and is Not applicable to all set ups. Please consult your shop, tuner , or supercharger guy for their perspective. This is our perspective on the situation at hand.
The hellcat platform has been led down the path of modifying cars in the wrong fashion. The platform started off with small uppers (2.4-2.6 uppers) and 8-10% lowers. What followed were exploding superchargers taking out lids and blowing holes in blower bases. The generalized consensus was bearings. That was completely wrong and the generalized consensus has stuck. We are going to change this. We willl be informative and we will share this post over and over until the community wraps there head around it.

The issue
Lets start off with whats going on. The supercharger rotors are made of a casting material that can not take the forces you guys are subjecting them to. There is not a solution to the failure other then just being smart. Heat, rpm, and load are putting stress on the rotor. As you spin the rotors to the brink the rpm creates heat causing the rotors to deform. Yes I said that right when you have your rotor that weights roughly 30 lbs spinning inside your motor at 30,000 plus revolutions per minute. Thats 500 revolution per second. This puts stress on the material make up of the rotors. When it reaches a point of failure it releases the casting from shaft of the rotor causing the rotors to touch and then BOOM. Thats when all the destruction happens. Chunks of rotors go flying and its like pulling a pin on a grenade.

The fix
How do we solve this? We slow the blower speed down or we change the shift point working with the combo at hand. Using the stock shift point of 6500 rpm it is on a chart saying a 2.75 10% is the limit. We recommend you rule on the side of caution with a 2.85 and 10% on a 2.4 ihi and 3.1 10% on a 2.7 ihi. This gives you room for error when your out having fun. Please use perspective on how your applying your hp you make to your intent with the car. If your going to do burnouts run a 3.17 hellraiser. Keep some stress off the supercharger. You dont need 1000 hp pulley combo to smoke tires. Use that 1000 hp combo for the drag strip. It takes all of 15 min to change a pulley. If you dont want to change a pulley then probably best you sacrifice 20-30 hp for

Longevity and reliability. Be smart not reckless.

How to figure your blower speed

Take the size of your upper and divide it by the lower size. Multiply that number by your shift rpm. That will give you your drive rotor speed. Then multiply that number by 1.6 and that will give you the non drive rotor speed.

Community advice.
When you hear someone recommend more pulley then what is suggested above make sure whoever your quoting or referencing signs a legal document backing your decisions financially. You will see how long that advice stays strong. Ill let you know a secret. They never will back it.

Porting and its role
How does porting effect this. Well porting increases air flow into the rotors. This means rotors are compressing more air per revolution. This creates more psi. PSi is heat. If you now couple this with more blower speed you have put the blower into a higher load environment and are subject a higher probability of failure. If you slow blower down allow port to breath you can make more hp with a port and slower blower speeds then you can with a stock blower spinning the guts out of it. Our port work is making 900 plus wheel hp with a 3.1 upper and 10% lower and 975+ with a 2.8 and 10% on a 2.4 ihi. If your looking for more run at your own risk but we recommend if you want more magnuson and whipple make 1000 plus wheel superchargers for your needs and wants.
I hope this info reaches you well below are pictures of the results of to much blower speed.
Please be responsible with your decisions and who is advising

Since moving to the 2.85 the car has been stronger, yes I only finished the car yesterday but I put 150 miles on it and it feels way better. Have you ever thought about backing off the 2.72 and trying a 2.85? Clutched or unclutched imo doesnt matter.

 

[fumanchu182]

Also should be noted, I have a Kong 108mm tb with the 108mm snout matching and a full supercharger rebuild

 

[DavidKFla]

Also should be noted, I have a Kong 108mm tb with the 108mm snout matching and a full supercharger rebuild

You have a mega build.

 

[16GoManGoHC2]

I think this is an understatement. After seeing about 23 PSI from a 2.70 and a 10% lower the car was just not right. Bypass valve closed, running out of fuel, etc. Here is a post from Jokerz about combo pulleys meant to help the community.



Since moving to the 2.85 the car has been stronger, yes I only finished the car yesterday but I put 150 miles on it and it feels way better. Have you ever thought about backing off the 2.72 and trying a 2.85? Clutched or unclutched imo doesnt matter.

Excellent info from Brett and I agree with him 100%. 2.72 and +10 lower should be the extreme limit for a 2.4. I was originally running a 2.85 with the +10 lower until the 2.85 failed (moved back into the snout) and I had a 2.72 on hand so I used it. Was there a gain going to the 2.72? Slight, If I were to buy a new one I would probably buy a 285 being that these 272s aren’t lasting very long it’s just too much power transfer going through them.
This info is spot on HP wise, I’m making about 975 wheel with a 2.72 and +10 lower.





My savior is my killer chiller is still working great and keeps the IAT’s in check even in this 90F heat. The blower with the pulley combo would never survive long without it.

And she still performs well even in +3000 DA.



Notice the time on the HMI and the run time. These pictures taken right before and after the run.




The squiggly lines in the top of third just before the shift was the tires breaking loose at 100+, PURE FUN!!

Now if I could just get these pulleys to survive more than a month LOL

 

[Speedy!]

That's good info and lines up with what I'm being told from people that KNOW. Heat kills these superchargers and SDG also said it's never the bearings.

There's one typo in there I think, ir I'm reading it wrong but you divide crank pulley diameter by upper pulley diameter then multiply by shift rpm, then 1.6 to get the male rotor speed.

 

[vortecd]

That's good info and lines up with what I'm being told from people that KNOW. Heat kills these superchargers and SDG also said it's never the bearings.

There's one typo in there I think, ir I'm reading it wrong but you divide crank pulley diameter by upper pulley diameter then multiply by shift rpm, then 1.6 to get the male rotor speed.

SDG just posted the rotor speed with different pulleys set up on their facebook page this weekend. Shows green to red in speed

 

[vortecd]

They did both blowers also 2.7 and 2.4
We have a thread on that. I will add it to that thread

 

[Speedy!]

Tag me in that please I may have missed it.

 

[16GoManGoHC2]

They did both blowers also 2.7 and 2.4
We have a thread on that. I will add it to that thread

Post it in this thread to if you would please good information to have here as well

 

[vortecd]

 

[vortecd]

 

[jonx96]

Mine has been in the red…. When I bought it one of the shift points was at 6800. I wonder how long my blower will last. I have been debating if it’ll be best just to get a whipple. Or send it out for a blower plate and have it inspected. Unsure. Seeing those charts are scary. But mooo powa!! Spin it to win it!

 

[Speedy!]

My gut says it's cumulative. Spin it hard a few times and probably no big deal, but repeatedly and things start to go south. I also wonder how things like billet bearing plates and ported snouts effect the chart data.

 

[vortecd]

My gut says it's cumulative. Spin it hard a few times and probably no big deal, but repeatedly and things start to go south. I also wonder how things like billet bearing plates and ported snouts effect the chart data.

Neither should be you are still spinning it that many rpms

 

[Speedy!]

I'm reading it's a combination of RPM + Heat. More air = more pressure = more heat.