wow... that seriously sucks for you guys at elevation...

 

Nitrous is your friend.

 

If your client needs that much boost, why not do a 10-rib? Combined with the FD2, you can support max pulley speed with any brand C6 head unit.

 

Sorry for not posting earlier. I was away for a week.

The 6 rib setup + flip drive is better than an 8 rib setup by itself. The only limit is the strength of the belt (standard NAPA/Gates), which we found to be in the neighborhood of 20 to 21 psi on a D1SC(105%) making 740+ rwhp through an unlocked converter on a 4l60e. This is substantially higher than we have seen on 8 rib setups of any type from any blower setup manufacturer. It is plain and simply just a more stable setup.

An 8 rib with a flip drive we have not found the limit yet, we have personally tested up to 24 to 25 psi on a on a F1R(101%) making 850+ through an unlocked converter on a 4l80e transmission (about 1200+ fwhp).

The big test isn't on the dyno, but rather on the track with logging. You may have a particular setup hold on the dyno, but when you spin up a stick shift car on the track or street and go through the gears the problem really tends to show itself there. The slip will tend to occur at the crank (for various design issues) on the subsequent pull (ie: after a gear change) because the deceleration of the engine and the mass of the blower wanting to remain at a constant speed (inertia) tends to cause the belt to unsettle/slip. So when you have a setup that is borderline on the dyno it will fail on track.

With the people that are going fast/making big power reliably you have two particular setups. Either a flip drive or a drag setup with no accessories (just alternator). They have the same thing in common... the belt routing is the same on both for the blower. The flip drive facilitates this superior belt routing without having to sacrifice what makes your car so enjoyable to drive.

Max

 

Nice information Max!!!

 

I dont have any clients. I only mod my car. I am not looking to add another 2000 bucks to get a few more HP.

I am a forum vendor solely to support St Judes Hospital with specific porting ventures.

I'll go 1000 bucks if it nets me 3 more PSI, otherwise I'll start using nitrous that I already have in the car. A 35 shot is 100+HP on a S/C car and would last for 50 hits.

I'm just bored. My car is insane now with permanant Mickey Thompsons and more power than I can get to the ground. I dont drive over 100mph and my car will not be faster 0-100 with another 100HP. If you get caught street racing here, the court orders your presence for the crushing of your car.

 

Thanks Max. You pretty much convered what I needed to know by PM also.

On a side note, I highlighted the part there in red because I was slammed by a few S/C newbies when I suggested this as a reason why so many FI cars dont run track results in proportion to the dyno numbers. They would state that 600hp is 600hp, yet the MPH at the track never supported this. Subfloor's run at less that 600rwhp netted a 9.95 run yet s/c cars with 600rwhp have issues with a mid 10 sec pass.

Thanks for the input.

 

No problem. I am happy to be able to contribute.

The other thing is that the boost coming back in between gears isn't 100% instant. In an automatic it's different, but for a stick once you purge the pipes you have to refill them. Not much, but it still occurs. It is another factor why stick shift cars that are SC'd don't quite perform as well as an NA version making the same HP given all other things equal. Not to mention that without a compressor map and knowing what the RPM of the compressor wheel is vs the boost pressure(I'm sure with some good data acquisition and plotting we can do it - but still no compressor map so what good is the work to get the info - plus data would vary for every different setup), we have no idea what is happening to the air (IE: compressor surge, etc). These centrifugal blowers are really no different than a turbo in some ways.

This isn't as bad as lets say a turbo (lag), but it is still there.

Lets say the condition last for .2 to .3 seconds with the severity of the boost loss being the greatest at the beginning of the .2 to .3 seconds and tapering off by the end to nothing. You multiply this by the number of gear changes and you have .6 to .9 seconds of less than "full normal boost" at that given RPM (with a varying degree of severity in boost loss over that time period).

Obviously the slower you shift the worse it gets.

NA cars have a recovery time as well, do to conditions within the engine, but it is far less than in a boosted application.

For comparison:
We have had some customers with about 640 to 650 RWHP in SC autos going 9.8X to 9.9X in the quarter. While to accomplish the same with NA power we have only required about 575 RWHP to accomplish the same. Not 100% apples to apples, but close enough (small differences in weight, 60ft, etc) to get the idea that the two different numbers on the dyno turn out to be something different on the track.

Disclaimer 1: dyno numbers vary from dyno to dyno.

Just some food for thought.

I am not knocking SC setups or even covering all versions, just putting my observations out there.

Disclaimer 2: Some of this is speculation without some cold hard data.

Max

 

Thanks.

 

I agree. I had a Camaro that made a little over 400rwhp through an aggressive drag setup, but ran low 10s all day, but I'm sure my 600+rwhp Vette wouldn't come close. Then the Camaro made mid 500s and ran low 9s, in my Vette's dreams, lol.

 

I have made my decision on the flip drive and will be on the phone this week Max...

 

Talk to you soon