What are some of your opinions about overspinning a centri head unit a few thousand rpms on the impeller speed? Pros, cons, or personal experiences? Thanks!
with a Vortech Si, a 3.6 @ 7000 rpms will be pretty much maxing it out RPM wise.
maybe a 3.4 if you kept it under 6500rpms
-carl
3.6, 7K rpm and 7.33 crank = 51310 rpms...
3.4, 7K rpm and 7.33 crank = 54328 rpms...
I say 3.4. People have been overspinning these bad boys since day one. And the numbers they publish are always conservative. and you'll only be at 7000 rpm for a quick second...
But then again I may be under some sort of obligation to only quote manufacturers specs.
3.6, 7K rpm and 7.33 crank = 51310 rpms...
3.4, 7K rpm and 7.33 crank = 54328 rpms...
I say 3.4. People have been overspinning these bad boys since day one. And the numbers they publish are always conservative. and you'll only be at 7000 rpm for a quick second...
But then again I may be under some sort of obligation to only quote manufacturers specs.
The 7.33 is stock crank pulley size Steve? I thought it was 7.5 inches?
52000 RPM appears to be the published OEM maximum operating speed for the V3Si SC. This is very different from the critical maximum speed.
In most industrial applications (gas turbines, steam turbines, internally geared air compressors, etc...) a critical overspeed limit is set 10% above the maximum operating speed. This well within the safety factor of the machine. 110% max speed for the V3Si is 57200 RPM.
In a internally geared machine, the main issue running at overspeed is the dynamic oil wedge thickness between leading gear edges upon contact. As the speed of the gears increase, the force contact between the gears increases and this oil wedge becomes thinner. The smaller oil wedge increases the probability for metal to metal contact (damage) or any particles in the oil to cause FOD (foreign object damage) on the gear faces. This type of damage will initially show up as a high gear mesh frequencies and eventually escalate in to an audible gear whine.
The oil seals in these compressors are similar to PD oil deflectors. The only thing that will cause an issues (leaking) with them is run out of the shaft that will causes their fits to increase. Slight bumps over the maximum operating speed should not have had any effect on these.
In summary, I would only worry about it if you were going to run your SC at overspeed (<=57200) for an extended amount of time. In an automotive application I would not be concerned.
One of the most important factor about overspinning a unit is the heat generating from overspin, it may seem as overspinning the unit makes more power but after checking the ATI it tence to make less power with the heat factor, its better to use a bigger unit and spin it less than to try and spin a small unit max, the unit generate less heat and makes it more efficient with more power. I also try spinning a D1SC head unit over the max and it did damaged the popellers inside the unit by hitting the housing. So the theory for HP are to spin a big unit about 80% to max than to try and spin a small unit 110%. Now in TX427 case, he wanted max HP and he had no choice to spin a F1R to 110% but the intercooler has to be big and he will still loose some power because of heat. Remedy for his application will be to increase the unit but he will have to do the whole system over because his intercooler could be at the max flow with a F1R.
One of the most important factor about overspinning a unit is the heat generating from overspin, it may seem as overspinning the unit makes more power but after checking the ATI it tence to make less power with the heat factor, its better to use a bigger unit and spin it less than to try and spin a small unit max, the unit generate less heat and makes it more efficient with more power. I also try spinning a D1SC head unit over the max and it did damaged the popellers inside the unit by hitting the housing. So the theory for HP are to spin a big unit about 80% to max than to try and spin a small unit 110%. Now in TX427 case, he wanted max HP and he had no choice to spin a F1R to 110% but the intercooler has to be big and he will still loose some power because of heat. Remedy for his application will be to increase the unit but he will have to do the whole system over because his intercooler could be at the max flow with a F1R.
Making power with a larger unit is more efficient than running a smaller unit at higher speeds. It will definatley lower your IATs.
Pulley down one size like that will net you around 1.5 - 2lb increase in boost. So probably 30-50rwhp, but that's depends on your other mods, and the flow efficiency of the motor.
Quote:
Originally Posted by BigMay60
So what happended, Brian? Did one of your oil seals start to leak this year? Did you ever run with the unit overfilled?
No, nothings wrong with the V3, none at all. This was a conversation piece that's come up before, and I did a search and didn't find much on it. So I figured I'd see what other opinions were on it. I may look at spinning it up a couple thousand over the max rated speed one day. Just looking at opinions.
I've never really "overfilled" the unit. But the 4oz bottles they give you is just a little more than what you need in the unit. I've only change the oil once in it. Drained it all out, and then put the whole 4oz in. It would burp a little (on the vent plug, not everywhere) the first few weeks/month, then would stop after a certain point. But it did this from the beginning, so apparently even Vortech "overfilled" it a little too.
The answer to your question depends on the application beeing used, are you going to use the same size motor you had before, are you using the same size heads you had before, same size valves, same size cam? now those are the answers you will have to consider first, then if not, there will be alot of other things to think about, if the heads are flowing better and the cubic inch are the same, the boost gage might read the same as before but the motor will be gaining more power, the boost is a restriction to the motor, the more the motor is restricted, the more boost you see, therefore it is not the restricted boost that makes the power but the CFM that applied to the motor. Now if your heads are flowing better and you down size the pulleys, you might have the same reading on your boost gauge and could be making over 80 to 90 more RWHP.
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Impeller speeds
