Pettit Super Charger Owners
01-15-2012, 10:53 AM
#9351
yessir I did. The solenoid on the vaccum chamber itself was not working. The valve itself is fine--hold vacuum without a problem, smooth action and the self check event is working great.
I didnt do an airflow study as my seat of the pants diagnosed that. It was obvious.
I didnt do an airflow study as my seat of the pants diagnosed that. It was obvious.
01-20-2012, 09:51 AM
#9352
at the risk of fueling the flames of supercharger fanboi hatred, the cons are that small displacement, high rpm engines and superchargers do not a good couple make. First, the supposed lowend boost of an SC setup is totally false, it is just the opposite with today's turbo technology. Second, for the same engine stress level that you make an extra 70 HP on a Renesis with an SC equates to about an extra 110 HP with a turbo setup because of the power drain required to spin the SC at high speed. Further, with a high rpm engine then the higher you spin the engine the more power eaten up by the SC and in turn the more stress load that is placed on the engine for any given power increase at the rear wheels. The higher stress load is not just on the engine, but also all the supporting equipment such as radiator, oil coolers, exhaust sizing etc. They are also a lot harder to keep quiet since there is nothing damping the sound level coming directly out of the engine unimpeded into a high flow exhaust system.
The pro is that you can't just turn up the boost at the twist of a ****, which is where most turbo owners discover their destiny to fail.
The pro is that you can't just turn up the boost at the twist of a ****, which is where most turbo owners discover their destiny to fail.
01-20-2012, 10:26 AM
#9353
at the risk of fueling the flames of supercharger fanboi hatred, the cons are that small displacement, high rpm engines and superchargers do not a good couple make. First, the supposed lowend boost of an SC setup is totally false, it is just the opposite with today's turbo technology. Second, for the same engine stress level that you make an extra 70 HP on a Renesis with an SC equates to about an extra 110 HP with a turbo setup because of the power drain required to spin the SC at high speed. Further, with a high rpm engine then the higher you spin the engine the more power eaten up by the SC and in turn the more stress load that is placed on the engine for any given power increase at the rear wheels. The higher stress load is not just on the engine, but also all the supporting equipment such as radiator, oil coolers, exhaust sizing etc. They are also a lot harder to keep quiet since there is nothing damping the sound level coming directly out of the engine unimpeded into a high flow exhaust system.
Tuning and proper setup of the fuel system actually does mitigate this to a point. At least, you can go to 11, which is one more louder than 10.
01-20-2012, 11:23 AM
#9354
you know --one thing that kinda interests me is why are there not bigger differences between the rwhp of a sc set up versus a turbo set up with approx the same amount of air flow? Now i realize it is hard, if not impossible, to get an apple to apple comparason but shouldnt there be at least some basic simalarities?
I mean if both systems are showing 365g/sec air flow for example and all other " predictors" of power are in the same ballpark---why isnt the rwhp much greater for the turbo? If the SC is a 40 hp parasite then why arent more turbo's showing 330-340 rwhp numbers?
Turbos ARE showing a good deal more TQ numbers but as expected the Tq band is different.
Just an honest question---no turbo/sc war meant.
I mean if both systems are showing 365g/sec air flow for example and all other " predictors" of power are in the same ballpark---why isnt the rwhp much greater for the turbo? If the SC is a 40 hp parasite then why arent more turbo's showing 330-340 rwhp numbers?
Turbos ARE showing a good deal more TQ numbers but as expected the Tq band is different.
Just an honest question---no turbo/sc war meant.
01-20-2012, 01:40 PM
#9355
At ~380g/sec, the SC cars put down about 260 - 280 HP while the TC cars make 300 - 320 on medium-sized turbos.
The torque curve isn't really even comparable.
01-20-2012, 02:40 PM
#9356
A turbo is free to spool up as the dynamics of the system allow it to, but the SC is directly tied to the engine rpm change. So the SC is only capable of linear output relative to the engine spinning up. Hou can see the difference in the dyno graphs
Your not going to see an output like this with a SC
Your not going to see an output like this with a SC
01-20-2012, 02:49 PM
#9357
I'm surprised there aren't a few splotches on that dyno sheet after the number of times you have made love to it .
But yeah - the only way a SC'd owner would appreciate the difference is from hopping from a SC car to a well sorted (not that many around) turbo car of the same whp.
But yeah - the only way a SC'd owner would appreciate the difference is from hopping from a SC car to a well sorted (not that many around) turbo car of the same whp.
01-21-2012, 09:11 AM
#9364
if the question is answered then further analysis is non productive.
I am too old to waste time---thats for you young folks.
At some point I would like to do another dyno.
At this point my tuner says if the a/f's remain ok then I should be good--i dont have any lean spikes that I can see--got lucky I guess.
But I sure am keeping an eye on it.
Meanwhile has anyone wired up a fuel pressure switch to cut the pump if the pressure drops too low?
And what is too low? Would than be a car specific thing? I would think so? I am thinking that if it drops below 53psi or so that would be time to cut the pump off?
Any advance from anyone?
Just got my pack of hose candy it---it is a really a neat good looking concept
I am too old to waste time---thats for you young folks.
At some point I would like to do another dyno.
At this point my tuner says if the a/f's remain ok then I should be good--i dont have any lean spikes that I can see--got lucky I guess.
But I sure am keeping an eye on it.
Meanwhile has anyone wired up a fuel pressure switch to cut the pump if the pressure drops too low?
And what is too low? Would than be a car specific thing? I would think so? I am thinking that if it drops below 53psi or so that would be time to cut the pump off?
Any advance from anyone?
Just got my pack of hose candy it---it is a really a neat good looking concept
01-21-2012, 09:52 AM
#9365
If you were going lean from the pump pressure dropping, cutting the pump at that instant will just cause immediate detonation.
On my setup, if the fuel pressure drops below 48 PSI, my boost controller dumps my wastegate.
What you guys need is a controller that opens your bypass under similar situations.
01-21-2012, 12:57 PM
#9367
Ok I will bite---what is the purpose of an airflow study when the question is whether the ssv is opening? If it was confirmed that it wasnt opening and then after repair it was confirmed that it was--then what is an airflow log going to show ( other than obvious differences in flow) that will be useful?
If the a/f's are still with in target what good would that data be? If the overall system is compensating for this change and the trims are not too high then what else to I need to do?
How do you determine that a retune is needed?
MM --- duhhhh-- I wasnt thinking---you are right.
I dont know how the bypass could be set up like that?
Could you do an ignition cut?
If the a/f's are still with in target what good would that data be? If the overall system is compensating for this change and the trims are not too high then what else to I need to do?
How do you determine that a retune is needed?
MM --- duhhhh-- I wasnt thinking---you are right.
I dont know how the bypass could be set up like that?
Could you do an ignition cut?
01-21-2012, 01:17 PM
#9368
Don't be so hard on yourself. Your dead right. Its just that there are some of us who prefer...scratch that...want a supercharger, even recognizing all the turbo advantages you just quoted.
So here we are, on a forum for RX8s, arguably not everyman's cuppa tea and as ill understood by the general public as quantum mechanics, and further splitting the event horizon by arguing different forced induction modalities. Wait until we start talking about which metal is best suited for the fasteners (Unobtainium, of course
).
The grass is green, the sun is shining, and the long ribbon of asphalt awaits
So here we are, on a forum for RX8s, arguably not everyman's cuppa tea and as ill understood by the general public as quantum mechanics, and further splitting the event horizon by arguing different forced induction modalities. Wait until we start talking about which metal is best suited for the fasteners (Unobtainium, of course
).The grass is green, the sun is shining, and the long ribbon of asphalt awaits
01-21-2012, 01:30 PM
#9369
Ok I will bite---what is the purpose of an airflow study when the question is whether the ssv is opening? If it was confirmed that it wasnt opening and then after repair it was confirmed that it was--then what is an airflow log going to show ( other than obvious differences in flow) that will be useful?
If the a/f's are still with in target what good would that data be? If the overall system is compensating for this change and the trims are not too high then what else to I need to do?
How do you determine that a retune is needed?
If the a/f's are still with in target what good would that data be? If the overall system is compensating for this change and the trims are not too high then what else to I need to do?
How do you determine that a retune is needed?
01-21-2012, 09:37 PM
#9372
Team you never answered me?
Thanks Brettus once I discovered that it wasnt working I was really careful in running it--keeping a close eye on my lc 1 innovate wide band readings during the transition time. I did notice a slight change as I now have a very small/short, leaner period when the valve opens.
I really dont understand why the a/f's havent changed more?
Its been raining all day--tomorrow I am going to add some torco to the gas and do some careful logging.
I got the "hose candy" installed and it does look good.
Thanks Brettus once I discovered that it wasnt working I was really careful in running it--keeping a close eye on my lc 1 innovate wide band readings during the transition time. I did notice a slight change as I now have a very small/short, leaner period when the valve opens.
I really dont understand why the a/f's havent changed more?
Its been raining all day--tomorrow I am going to add some torco to the gas and do some careful logging.
I got the "hose candy" installed and it does look good.
