Any Pettit Racing Supercharger news?
02-26-2005, 01:21 PM
#51
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Originally Posted by carguy425
I regards to what zoom zoom said; does anyone know for sure with the Greddy turbo where the boost starts kicking in? It seems to me (from the video) that you get full boost almost instantly but it doesn't come on 'til about 5k. I can only imagine that the SC peaking at 220 rwhp has got to be pretty equal to the greddy putting out 240rwhp, at least in the 1/4, and probably even better if you are talking stoplight to stoplight. Any backup on this theory?
02-26-2005, 02:51 PM
#53
Oh boy, Fanman, I noticed you were sure to put in "most of the time." I could go into a lecture here but I just had a phone conversation yesterday with Rotarygod, and we agreed to both give up explaining these things. There are more productive things to do. 
Maybe someone else will want to pick up the load on this?
Maybe someone else will want to pick up the load on this?
02-26-2005, 04:51 PM
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Yeah, I did preface that with most of the time. In general if you look at the power a turbo is putting out (peak hp figures) vs. a roots type blower, many people would assume the turbo will kill a roots unit, but they go about things in very different ways. The curves will look very different from a roots-type blower, vs. turbo vs. a centrifugal unit. You have to determine which unit fits best for your driving style.
I guess the centrifugal unit from Sunflower kind've went by the wayside.
I guess the centrifugal unit from Sunflower kind've went by the wayside.
02-27-2005, 12:03 AM
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Originally Posted by Richard Paul
...I could go into a lecture here but I just had a phone conversation yesterday with Rotarygod, and we agreed to both give up explaining these things....
02-27-2005, 11:29 AM
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I emailed them last year about this and they said they had come up with a way to keep the stock brace. Not sure if it's still true.
Originally Posted by Nemesis8
And what about the Mazdaspeed strut tower brace? Will the Pettit kit install with this brace in place?
02-27-2005, 11:44 PM
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Ok, now here's a question for all you FI gurus...
I'm pretty sure I'm going to wind up with the Hymee or Pettit twin-screw type supercharger. Either unit will be limited to 6-8 Lbs of boost to protect the otherwise stock Renesis. But down the road a bit, I plan to yank the engine and have it built up stronger to take more boost with an eventual goal of 400-500 WHP. My question is, will either of these units be able to be made to make more boost, and if so, how? Is it as simple as changing the S/C drive wheel and retuning, or what all is involved? And what is the theoretical limit of boost either of these units can make?
I'm pretty sure I'm going to wind up with the Hymee or Pettit twin-screw type supercharger. Either unit will be limited to 6-8 Lbs of boost to protect the otherwise stock Renesis. But down the road a bit, I plan to yank the engine and have it built up stronger to take more boost with an eventual goal of 400-500 WHP. My question is, will either of these units be able to be made to make more boost, and if so, how? Is it as simple as changing the S/C drive wheel and retuning, or what all is involved? And what is the theoretical limit of boost either of these units can make?
02-28-2005, 12:07 AM
#62
You should ask me that on my thread 
The theoretical limit for the blower I am using, and it's max RPM limits etc is about 12 PSI. According to Autorotor literature I have, this blower is good for about 400 odd HP. The smaller blower obviously cant go that high.
Interestingly, and you need to think about that - is that both blowers can operate up to 15PSI. The problem is that is dependant on the airflow requirements of the engine. The smaller Pettit blower is rated to about 300HP. It pumps about 0.87 or 1.1 litres of air per revolution (depending on the exact model, which I don't know). The larger unit I am using pumps about 1.33 litres of air per rev. The renesis consumes 1.3 litres of air per revolution. The ratio between the engine's air requirements and the blowers output give you the manifold pressure that is developed (the "boost").
I don't think the boost level itself is a problem. I guess I'll have to explain myself about that another time, but it has to do with the rotors and shafts used in 6 and 7 second, 1000HP plus drag racers.
Anyway - the wait on this is killing me as well!
Cheers,
Hymee.
The theoretical limit for the blower I am using, and it's max RPM limits etc is about 12 PSI. According to Autorotor literature I have, this blower is good for about 400 odd HP. The smaller blower obviously cant go that high.
Interestingly, and you need to think about that - is that both blowers can operate up to 15PSI. The problem is that is dependant on the airflow requirements of the engine. The smaller Pettit blower is rated to about 300HP. It pumps about 0.87 or 1.1 litres of air per revolution (depending on the exact model, which I don't know). The larger unit I am using pumps about 1.33 litres of air per rev. The renesis consumes 1.3 litres of air per revolution. The ratio between the engine's air requirements and the blowers output give you the manifold pressure that is developed (the "boost").
I don't think the boost level itself is a problem. I guess I'll have to explain myself about that another time, but it has to do with the rotors and shafts used in 6 and 7 second, 1000HP plus drag racers.
Anyway - the wait on this is killing me as well!
Cheers,
Hymee.
Last edited by Hymee; 02-28-2005 at 12:13 AM.
02-28-2005, 12:51 AM
#64
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A more important thing to remember is that a piston engine on average makes about 10 hp per pound of air (not boost btw) whereas a rotary makes about 7 hp per pound of air.
02-28-2005, 03:18 AM
#65
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Originally Posted by rotarygod
A more important thing to remember is that a piston engine on average makes about 10 hp per pound of air (not boost btw) whereas a rotary makes about 7 hp per pound of air.
02-28-2005, 07:50 PM
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[QUOTE]Can you explain that to me please? Or is there a typo?? 55% RPM doesn't seem "instantly" to me, in a car with such a wide useful RPM range.
Hymee, what I meant is that it spools up very quickly (to full boost almost instantly) but from what I observed, it didn't seem to make any boost until 5k.
Hymee, what I meant is that it spools up very quickly (to full boost almost instantly) but from what I observed, it didn't seem to make any boost until 5k.
02-28-2005, 08:29 PM
#68
aoshi, This is a lesson I had to learn the hard way. I built the first SC for the Rx8 thinking that it needed the same CFM for a target HP that other engines use. I had to build a whole new one when we found this out, which was when we put it on the dyno.
The clue should have been the gas milage. For this much power it uses to much fuel. That can only be blamed on inefficency.
As for your speculation as to development of the rotary being behind. well it only takes about 10 other manufacturers doing intence development on rotarys for about another 50 years. The problem is that there is only one very small company working on this project. It will take a lot more diverse thinkers, meaning other brain trusts at other companys to find new ideas in the basic envolope of rotarydum.
I don't see this happening in the forseable future. If there is something that they would work on besides these silly hybrids it should be a small inexpensive turbine. They need to work out the throttle response problem which might not be solvable.
There are tons of ideas out there that might or might not work out. It is just that the Otto cycle engine in it's current piston configuration is so well developed and the parts are cheap. Everyone knows how they work and they do not want to give it up. Anything else is going to be expensive until it has been around for many years. In my lifetime I don't have to worry about having to work on anything else.
It remains to be seen about you. But I wouldn't miss the opportunity to learn about current engines thinking it's similar to wooden wagon wheels.
The clue should have been the gas milage. For this much power it uses to much fuel. That can only be blamed on inefficency.
As for your speculation as to development of the rotary being behind. well it only takes about 10 other manufacturers doing intence development on rotarys for about another 50 years. The problem is that there is only one very small company working on this project. It will take a lot more diverse thinkers, meaning other brain trusts at other companys to find new ideas in the basic envolope of rotarydum.
I don't see this happening in the forseable future. If there is something that they would work on besides these silly hybrids it should be a small inexpensive turbine. They need to work out the throttle response problem which might not be solvable.
There are tons of ideas out there that might or might not work out. It is just that the Otto cycle engine in it's current piston configuration is so well developed and the parts are cheap. Everyone knows how they work and they do not want to give it up. Anything else is going to be expensive until it has been around for many years. In my lifetime I don't have to worry about having to work on anything else.
It remains to be seen about you. But I wouldn't miss the opportunity to learn about current engines thinking it's similar to wooden wagon wheels.
02-28-2005, 08:33 PM
#70
[QUOTE=carguy425]
HUH?
Can you explain that to me please? Or is there a typo?? 55% RPM doesn't seem "instantly" to me, in a car with such a wide useful RPM range.
Hymee, what I meant is that it spools up very quickly (to full boost almost instantly) but from what I observed, it didn't seem to make any boost until 5k.
Hymee, what I meant is that it spools up very quickly (to full boost almost instantly) but from what I observed, it didn't seem to make any boost until 5k.
HUH?
02-28-2005, 10:06 PM
#71
Kaiten Kenbu Rokuren
Originally Posted by Richard Paul
aoshi, This is a lesson I had to learn the hard way. I built the first SC for the Rx8 thinking that it needed the same CFM for a target HP that other engines use. I had to build a whole new one when we found this out, which was when we put it on the dyno.
The clue should have been the gas milage. For this much power it uses to much fuel. That can only be blamed on inefficency.
As for your speculation as to development of the rotary being behind. well it only takes about 10 other manufacturers doing intence development on rotarys for about another 50 years. The problem is that there is only one very small company working on this project. It will take a lot more diverse thinkers, meaning other brain trusts at other companys to find new ideas in the basic envolope of rotarydum.
I don't see this happening in the forseable future. If there is something that they would work on besides these silly hybrids it should be a small inexpensive turbine. They need to work out the throttle response problem which might not be solvable.
There are tons of ideas out there that might or might not work out. It is just that the Otto cycle engine in it's current piston configuration is so well developed and the parts are cheap. Everyone knows how they work and they do not want to give it up. Anything else is going to be expensive until it has been around for many years. In my lifetime I don't have to worry about having to work on anything else.
It remains to be seen about you. But I wouldn't miss the opportunity to learn about current engines thinking it's similar to wooden wagon wheels.
The clue should have been the gas milage. For this much power it uses to much fuel. That can only be blamed on inefficency.
As for your speculation as to development of the rotary being behind. well it only takes about 10 other manufacturers doing intence development on rotarys for about another 50 years. The problem is that there is only one very small company working on this project. It will take a lot more diverse thinkers, meaning other brain trusts at other companys to find new ideas in the basic envolope of rotarydum.
I don't see this happening in the forseable future. If there is something that they would work on besides these silly hybrids it should be a small inexpensive turbine. They need to work out the throttle response problem which might not be solvable.
There are tons of ideas out there that might or might not work out. It is just that the Otto cycle engine in it's current piston configuration is so well developed and the parts are cheap. Everyone knows how they work and they do not want to give it up. Anything else is going to be expensive until it has been around for many years. In my lifetime I don't have to worry about having to work on anything else.
It remains to be seen about you. But I wouldn't miss the opportunity to learn about current engines thinking it's similar to wooden wagon wheels.
Thanks Richard. I've been reading as much as time allows me the last few months trying to learn what I can. To be truthful, it's been this forum that has taught me the most. Between your axial flow thread, RG's 3859489485 pages posts about all sorts of different things, Hymee's posts and all the other gurus out there. I appreciate all the interesting stuff I've learned. Thanks again guys. *Tear* :p
