timing vs. high compression rotor help
11-02-07, 12:04 PM
#1
timing vs. high compression rotor help
Hey guys, this would be my first time posting in the Rotary Performance section 
I've just graduated from the newb section after (with the help of Rx7_Nut) building a 6 port motor with the 5th/6th ports bridged and the 3/4th ports street ported, also the center iorn is a s4t2 (Frankenstein motor), s5 T2 intake (custom port matched) and a s4 turbo with a megasquirt controlling it all. So the rotors are S5 N/A rotors (9.7:1 i think) and I'm not sure what to do with the timing...
I've gotten some turbo - extended port and turbo - half bridge timing maps (my motor's somewhere in between) that i've been using for reference. I just don't know (when looking at a extended port/half bridge map) how much timing I should be pulling to compensate for the high compression rotors. I also have a wideband and got the AFR's where i want them, I just don't know what I should be doing with the timing right now.... I'm scared that i'm gunna blow it up so I'm running like 10-16 deg BTDC under boost.
Oh I also have Rotary Aviation apex seals... not that it really matters but they should take a beating.
Cliffs:
s5 N/A motor with a 1/3 bridge and a turbo... What to do with the timing ?
Thanks, Philip
I've just graduated from the newb section after (with the help of Rx7_Nut) building a 6 port motor with the 5th/6th ports bridged and the 3/4th ports street ported, also the center iorn is a s4t2 (Frankenstein motor), s5 T2 intake (custom port matched) and a s4 turbo with a megasquirt controlling it all. So the rotors are S5 N/A rotors (9.7:1 i think) and I'm not sure what to do with the timing...I've gotten some turbo - extended port and turbo - half bridge timing maps (my motor's somewhere in between) that i've been using for reference. I just don't know (when looking at a extended port/half bridge map) how much timing I should be pulling to compensate for the high compression rotors. I also have a wideband and got the AFR's where i want them, I just don't know what I should be doing with the timing right now.... I'm scared that i'm gunna blow it up so I'm running like 10-16 deg BTDC under boost.
Oh I also have Rotary Aviation apex seals... not that it really matters but they should take a beating.
Cliffs:
s5 N/A motor with a 1/3 bridge and a turbo... What to do with the timing ?
Thanks, Philip
11-03-07, 10:00 PM
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All I can say is that your "ideal" timing with the higher compression rotors is going to be less than with the lower compression rotors since there is less volume for the expanding gas to fill before it starts pushing the rotor.
BUT this will also change with how much boost your running. When you increase pressure you increase the speed of combustion (this also applies to higher compression ratio). So you will also need to retard timing as boost goes higher.
As for your aux bridge setup, you're going to need a fire extinguisher handy.
BUT this will also change with how much boost your running. When you increase pressure you increase the speed of combustion (this also applies to higher compression ratio). So you will also need to retard timing as boost goes higher.
As for your aux bridge setup, you're going to need a fire extinguisher handy.
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11-04-07, 09:50 AM
#10
Originally Posted by Kyrasis6;7480041[B
]All I can say is that your "ideal" timing with the higher compression rotors is going to be less than with the lower compression rotors since there is less volume for the expanding gas to fill before it starts pushing the rotor.[/B]
BUT this will also change with how much boost your running. When you increase pressure you increase the speed of combustion (this also applies to higher compression ratio). So you will also need to retard timing as boost goes higher.
As for your aux bridge setup, you're going to need a fire extinguisher handy.
BUT this will also change with how much boost your running. When you increase pressure you increase the speed of combustion (this also applies to higher compression ratio). So you will also need to retard timing as boost goes higher.
As for your aux bridge setup, you're going to need a fire extinguisher handy.
Really, ya'll aren't gunna hurt my feelings or anything.
Also, I know that^ it makes sense... I was hoping to get a feel for how much less timing though, maybe even a ballpark figure? like are we talking 1-2 degrees 12-15 degrees?
Has no one done a high compression turbo (and tuned it)? I know people get spacers and slap turbos on 6 port motors but i think there rarely tuned properly.
11-04-07, 02:13 PM
#11
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lol, the fire extinguisher comment was metaphorical. Typically anyone who even hints at an Aux Bridge instantly gets flammed repeatatively.
As for an approximation as to what you should run for timing I do not know, I've never built one or talked to any of the experts. I do know a lot of the physics involved though so I gave the best information I could based on that.
As for an approximation as to what you should run for timing I do not know, I've never built one or talked to any of the experts. I do know a lot of the physics involved though so I gave the best information I could based on that.
11-04-07, 02:36 PM
#12
How much boost and what fuel octane?
Once everything else tuning wise is correct using 9.7 rotors would not be a problem. Complety stock S5 setups with little fuel mods boost 7 psi. I've done them up to 15 psi on 93 octane and as high as the turbo will produce psi. wise on race fuel.
Timing around 12 degrees is a very good starting point.
Once everything else tuning wise is correct using 9.7 rotors would not be a problem. Complety stock S5 setups with little fuel mods boost 7 psi. I've done them up to 15 psi on 93 octane and as high as the turbo will produce psi. wise on race fuel.
Timing around 12 degrees is a very good starting point.
11-04-07, 07:02 PM
#13
How much boost and what fuel octane?
Once everything else tuning wise is correct using 9.7 rotors would not be a problem. Complety stock S5 setups with little fuel mods boost 7 psi. I've done them up to 15 psi on 93 octane and as high as the turbo will produce psi. wise on race fuel.
Timing around 12 degrees is a very good starting point.
Once everything else tuning wise is correct using 9.7 rotors would not be a problem. Complety stock S5 setups with little fuel mods boost 7 psi. I've done them up to 15 psi on 93 octane and as high as the turbo will produce psi. wise on race fuel.
Timing around 12 degrees is a very good starting point.
and I'm useing 93 octane pump gas.... How much boost do you think it would be safe to run before switching to higher than 93?
also, in case you guys are curious here are the port pics. This is not your typical 6 port.
and i had planned on useing the sleves at first, then I ditched the N/A intake later.
11-05-07, 02:04 AM
#14
lol, the fire extinguisher comment was metaphorical. Typically anyone who even hints at an Aux Bridge instantly gets flammed repeatatively.
As for an approximation as to what you should run for timing I do not know, I've never built one or talked to any of the experts. I do know a lot of the physics involved though so I gave the best information I could based on that.
As for an approximation as to what you should run for timing I do not know, I've never built one or talked to any of the experts. I do know a lot of the physics involved though so I gave the best information I could based on that.
11-05-07, 08:22 AM
#15
Usually people flame aux bridges on NA's, because people think they can get the drivability of a stock port, with the flow of a bridge port. We all know that just can't happen. Aux bridge turbo's, on the other hand, are very rare, interesting, and can be made to work well. Look at Aaron Cake's setup. It seems to be an aux bridge turbo and it looks like it works well.
11-06-07, 08:23 AM
#17
If you have a power goal that's somewhat low, you can run less boost than turbo rotors to make the same amount of power. Also, your power under the curve will be larger, and as a by product of less bost, less turbo lag. There are a lot of disadvantages though.
11-21-07, 01:02 AM
#22
I recommend getting something better than a megasquirts computer for your setup. And the s4 turbo is way to small. @ 9000 rpm full boost 14-15 lbs max with lots of 93 pump gas you should be around 10.0-12.0 degrees. 15 psi and up with 110 race gas @ 9000 rpm you want 6.5 to 8.5 degrees. It needs bigger turbo to really be what you what. You should post pics of your setup in the car.
11-21-07, 10:29 AM
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I recommend getting something better than a megasquirts computer for your setup. And the s4 turbo is way to small. @ 9000 rpm full boost 14-15 lbs max with lots of 93 pump gas you should be around 10.0-12.0 degrees. 15 psi and up with 110 race gas @ 9000 rpm you want 6.5 to 8.5 degrees. It needs bigger turbo to really be what you what. You should post pics of your setup in the car.
11-21-07, 12:48 PM
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I recommend getting something better than a megasquirts computer for your setup. And the s4 turbo is way to small. @ 9000 rpm full boost 14-15 lbs max with lots of 93 pump gas you should be around 10.0-12.0 degrees. 15 psi and up with 110 race gas @ 9000 rpm you want 6.5 to 8.5 degrees. It needs bigger turbo to really be what you what. You should post pics of your setup in the car.
.... whats so bad about megasquirt??