Renesis Rotors
12-27-2003, 01:25 PM
#41
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Originally Posted by kahren' date='Dec 26 2003, 02:13 PM
it will blow if u really ping it hard under load
12-27-2003, 02:15 PM
#42
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Originally Posted by TheAntiChrice' date='Dec 27 2003, 02:25 PM
Ohh.. Okay.. then you learn something new everyday... I'm just going by what I've read and heard about rotaries that a good ping will pop a seal. So wait.. how resilient are these motors anyways and what would the ideal CR be for pump gas and moderate boost?
04-29-2004, 03:45 AM
#43
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Had to bring this subject back 
This is the way I see it. I think using the Renesis rotors in a boosted application could be very beneficial provided with good tuning. Here's an example:
Lets build 2 Fd engines to produce 400hp. Both engines will have the exact same setup(same upgraded twins everything). One will use it's stock rotors while the other will use the higher compression Renesis rotors. To make the 400 hp, theoretically both engines will experiance the same pressures and tempuratures inside the combustion chamber. Lets say that the engine with stock rotors makes its hp at 17psi. With the added leverage the higher compression rotors of the other engine, this engine should make that same hp but at a lower boost (14psi just guessing). That psi differance alone means the turbos are more in their efficiancy range. And we all know that a turbo running in it's efficiancy range mean that it's not heating the air like crazy. Also the less the air is heat decreases the chance of detination. I personally think this would be an excellent advantage of running the higher compression rotors in the older turbo engines. Overall drivability should be improved.
Lets build 2 Fd engines to produce 400hp. Both engines will have the exact same setup(same upgraded twins everything). One will use it's stock rotors while the other will use the higher compression Renesis rotors. To make the 400 hp, theoretically both engines will experiance the same pressures and tempuratures inside the combustion chamber. Lets say that the engine with stock rotors makes its hp at 17psi. With the added leverage the higher compression rotors of the other engine, this engine should make that same hp but at a lower boost (14psi just guessing). That psi differance alone means the turbos are more in their efficiancy range. And we all know that a turbo running in it's efficiancy range mean that it's not heating the air like crazy. Also the less the air is heat decreases the chance of detination. I personally think this would be an excellent advantage of running the higher compression rotors in the older turbo engines. Overall drivability should be improved.
04-29-2004, 03:57 AM
#44
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Join Date: Jun 2003
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Cept higher compression makes for detonation because the air is allready twice a dense at 15psi, you then compress it down 9:1 and its effectivly 18:1, ren rotors would be like 20:1,.. just my impression of it,.. may be wrong. On the other hand on the aus rotary forum and the rx8 forum I have heard of someone running stock rx8 seals in a PP motor in austrilia without problems,..
04-29-2004, 10:12 AM
#45
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Youre forgetting that increasing the compression will increase the VE, and spool a large turbo faster than lower compression, while having better off boost response.
Drago, your math on the chamber pressures is way off. You need to use absolute pressure. 2 engines both at sea level and 90% VE, one running 9.0 CR and one running 10.0. 14.7 PSI on the 9.0 CR motor will have the same chamber pressure as the 10.0 CR motor running 10.5 psi.
Drago, your math on the chamber pressures is way off. You need to use absolute pressure. 2 engines both at sea level and 90% VE, one running 9.0 CR and one running 10.0. 14.7 PSI on the 9.0 CR motor will have the same chamber pressure as the 10.0 CR motor running 10.5 psi.
04-29-2004, 04:28 PM
#48
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Originally Posted by mazdaspeed7' date='Apr 29 2004, 07:12 AM
Youre forgetting that increasing the compression will increase the VE, and spool a large turbo faster than lower compression, while having better off boost response.
Drago, your math on the chamber pressures is way off. You need to use absolute pressure. 2 engines both at sea level and 90% VE, one running 9.0 CR and one running 10.0. 14.7 PSI on the 9.0 CR motor will have the same chamber pressure as the 10.0 CR motor running 10.5 psi.
Drago, your math on the chamber pressures is way off. You need to use absolute pressure. 2 engines both at sea level and 90% VE, one running 9.0 CR and one running 10.0. 14.7 PSI on the 9.0 CR motor will have the same chamber pressure as the 10.0 CR motor running 10.5 psi.
Yep I forgot to mention those benefits as well
Ronin Fc, Don't get the impression thats it's not possible. Overall unless someone experiments with this we may never really know how well the engine performs in the long run. Thats why I'm keeping a very close eye on the turbo and supercharged Rx8's that are in development on the Rx8forum. Remember low compression is always refered on a factory boosted car because it leaves just enough of a safety blanket for those people who choose to use a lower octaine gas. Low compression is more user friendly for the average Joe. Thats doesn't mean that it's better than high compression for someone who can tune it properly(which should be done anyways).
04-29-2004, 04:47 PM
#49
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Here is a really excellent post form the Rx8forum about this subject:
Also keep in mind guys if the 3rd gen if felt stock it will easily go over 100k miles with its poor factory setup. Mine has 79k with original vac lines and runs damn near perfect. I'll give Rotorygod much props for the above info.
With lower compression, you have the ability to run greater timing advance as well as the ability to get away with lower octanes easier than you can with higher compression. On higher compression engines you need to run less timing. There is always a tradeoff. Everything is tuning based. Manufacturers know that not everybody treats their cars as they should. They go for performance numbers that are very conservative. They will also do this with the biggest margin of error that they can get. They understand that some people will use the cheapest gas they can find that has the least resistance to knock. When you are upgrading the performance of your vehicle, it is just assumed that you are accounting for this. When the '87 Turbo II RX-7 came out, Mazda claimed that they could not run any more boost or higher compression due to the risk of detonation. Then in '89 they upped the compression and the boost which totally countered their previous statement. In '93 they redesigned the engine to flow more air, slapped 2 pathetic little turbos on the car, made the coolant system less efficient, raised the boost, and still gained power. When do the reasons to do something stop? It really comes down to margin of safety vs their tuning abilities. With the stock Renesis tuning and it's frequent updates, do you trust Mazda with forced induction on this engine?
FWIW: Rotary Performance has used the 9.7:1 compression rotors in streetported single turbo 3rd gen RX-7's and put out over 400 rwhp. It is all in the tuning. Don't try it on your stock ecu. There does come a point in forced induction where you really do want to run lower compression since the higher compression engine will need so much timing retard that it is no longer gaining in power. This number is quite high though and realistically out of the range of a street driven car. Use the high compression. Just tune it.[/B]
FWIW: Rotary Performance has used the 9.7:1 compression rotors in streetported single turbo 3rd gen RX-7's and put out over 400 rwhp. It is all in the tuning. Don't try it on your stock ecu. There does come a point in forced induction where you really do want to run lower compression since the higher compression engine will need so much timing retard that it is no longer gaining in power. This number is quite high though and realistically out of the range of a street driven car. Use the high compression. Just tune it.[/B]
Also keep in mind guys if the 3rd gen if felt stock it will easily go over 100k miles with its poor factory setup. Mine has 79k with original vac lines and runs damn near perfect. I'll give Rotorygod much props for the above info.
04-29-2004, 07:00 PM
#50
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Originally Posted by The Ultimate 7' date='Apr 29 2004, 05:47 PM
I'll give Rotorygod much props for the above info.