Bridge port is over rated?
03-06-2007, 09:24 PM
#11
Senior Member
Join Date: Aug 2005
Location: Freeport FL
Posts: 381
lol thx heretic I had hit reply to the same post as it was loading to reply this and next post down you cleared it up. So many people confused as everyone is always talking about tq and gaining tq and not relies how irrelevant it is besides the equation factor of increased tq is increased hp but the tq measurement is still negligent.
But I do have a beef with your post perhaps it was an over site or misinterpretations. You stated and others on the net have readily stated. That TQ is what you feel and sits you back in the seat. When in fact TQ does no such thing TQ does absolutely nothing at all for feel or moving. TQ as you stated is simply a measurement of twisting force or force applied to/on an object measured in feet in/lbs. But what you feel accelerating you or pushing you back in the seat is simply and purely HP.
The comparison of low rpm engines and high rpm engines. When measuring in ft/lbs and hp no matter what engine you have TQ will always be greater then HP below 5252rpm and less then hp above 5252 rpm no exceptions. So a lower RPM engine like diesel engine will always produce more TQ then HP as it never revs to 5252rpm. Does this make it faster? No! The HP is the driving force of the motor not the tq. So if I increased the tq you’re not creating a faster vehicle. Now however since HP and TQ are equated as “(Horsepower X 5252) / Torque” by increasing tq you are also increasing HP or vise versa. So I think the correct explanation is a lower rpm vehicle will feel faster not because of the higher tq functionality but that its entire power band is useable much sooner / steeper then a broader power band engine making it feel faster. The other factor of gearing is directly related to available tq as output force on the tire contact point or pivot point. So another engine at peak power rpm like a 04 SVT will be around 5,600rpm making upper 300range of hp could easily be made to produce 600ftlbs of tq by gear ratio. Now the gear ratio will make each gear quicker but will slow the entire vehicle down top speed wise. So by changing gearing and static rpm comparisons between 2 engines I could directly make a SVT motor produce the same HP and TQ rating as a Cummins turbo diesel motor. They will however produce this power at entirely different rpm bands where the diesel motor would be running at around 3,200rpm or less and the SVT motor be running at above 5,000rpm. So what one seems more practical to deliver produces in? And what one seems more practical for race car driving?
The last thing to touch on based on RPM available power delivery is that RPM can also be negligent to direct performance but never irrelevant to power output, in some sort or fashion in some engines. I say this because by increasing rpm you are inevitable drawing a larger power band but taken to grater extremes we still have to keep piston speeds viable. By doing this I am saying increasing rpm will inevitable eventually yield in producing a shorter stroke. So the high rpm motor will be making the same power levels at higher RPM’s of a similar motor with a longer stroke at lower RPM’s. This is because the piston speed traveling is the same, as speed is determined by time and distance and piston speed can be determined by “piston speed (fpm) = stroke (inches) x rpm / 6”, the difference being power band production.
To the posted. Everything has basically been stated for you and BDC did an excellent job at it. Maybe you understand already or gathered it from others posts. Increasing the timing in advance or early has 2 side effects and people inquired about them both but in each scenario overlooked the other. BDC covered this but was very blunt about it you can increase the scavenging at lower rpms by some advance and produce more power lower in the region. Again taken to more extremes with larger ports there is not enough velocity left of reversion to purge the system as this is seen in loss of vacuum and thus shifts the power band farther up, the lingering side effect being a higher idle more timing advance and a lope or brap. I have been experimenting by trying to leave the bowel smaller and not increase the sizes I think it may be big enough as it is and apply a little more timing. I will see with a few more motors how I like this VS less timing and shaping the bowel and runners more. This falls back into my believe you cant just ask someone for a port or ask us what about this port because it is kind of like asking us how I think a new flavor of ice cream is going to taste, We cant possibly know. The porter should adjust his setup to what you want and you need to supply the information to them of what you want to do with the car. As simply put a setup for drag is not going to work to good on SCCA coarse.
But I do have a beef with your post perhaps it was an over site or misinterpretations. You stated and others on the net have readily stated. That TQ is what you feel and sits you back in the seat. When in fact TQ does no such thing TQ does absolutely nothing at all for feel or moving. TQ as you stated is simply a measurement of twisting force or force applied to/on an object measured in feet in/lbs. But what you feel accelerating you or pushing you back in the seat is simply and purely HP.
The comparison of low rpm engines and high rpm engines. When measuring in ft/lbs and hp no matter what engine you have TQ will always be greater then HP below 5252rpm and less then hp above 5252 rpm no exceptions. So a lower RPM engine like diesel engine will always produce more TQ then HP as it never revs to 5252rpm. Does this make it faster? No! The HP is the driving force of the motor not the tq. So if I increased the tq you’re not creating a faster vehicle. Now however since HP and TQ are equated as “(Horsepower X 5252) / Torque” by increasing tq you are also increasing HP or vise versa. So I think the correct explanation is a lower rpm vehicle will feel faster not because of the higher tq functionality but that its entire power band is useable much sooner / steeper then a broader power band engine making it feel faster. The other factor of gearing is directly related to available tq as output force on the tire contact point or pivot point. So another engine at peak power rpm like a 04 SVT will be around 5,600rpm making upper 300range of hp could easily be made to produce 600ftlbs of tq by gear ratio. Now the gear ratio will make each gear quicker but will slow the entire vehicle down top speed wise. So by changing gearing and static rpm comparisons between 2 engines I could directly make a SVT motor produce the same HP and TQ rating as a Cummins turbo diesel motor. They will however produce this power at entirely different rpm bands where the diesel motor would be running at around 3,200rpm or less and the SVT motor be running at above 5,000rpm. So what one seems more practical to deliver produces in? And what one seems more practical for race car driving?
The last thing to touch on based on RPM available power delivery is that RPM can also be negligent to direct performance but never irrelevant to power output, in some sort or fashion in some engines. I say this because by increasing rpm you are inevitable drawing a larger power band but taken to grater extremes we still have to keep piston speeds viable. By doing this I am saying increasing rpm will inevitable eventually yield in producing a shorter stroke. So the high rpm motor will be making the same power levels at higher RPM’s of a similar motor with a longer stroke at lower RPM’s. This is because the piston speed traveling is the same, as speed is determined by time and distance and piston speed can be determined by “piston speed (fpm) = stroke (inches) x rpm / 6”, the difference being power band production.
To the posted. Everything has basically been stated for you and BDC did an excellent job at it. Maybe you understand already or gathered it from others posts. Increasing the timing in advance or early has 2 side effects and people inquired about them both but in each scenario overlooked the other. BDC covered this but was very blunt about it you can increase the scavenging at lower rpms by some advance and produce more power lower in the region. Again taken to more extremes with larger ports there is not enough velocity left of reversion to purge the system as this is seen in loss of vacuum and thus shifts the power band farther up, the lingering side effect being a higher idle more timing advance and a lope or brap. I have been experimenting by trying to leave the bowel smaller and not increase the sizes I think it may be big enough as it is and apply a little more timing. I will see with a few more motors how I like this VS less timing and shaping the bowel and runners more. This falls back into my believe you cant just ask someone for a port or ask us what about this port because it is kind of like asking us how I think a new flavor of ice cream is going to taste, We cant possibly know. The porter should adjust his setup to what you want and you need to supply the information to them of what you want to do with the car. As simply put a setup for drag is not going to work to good on SCCA coarse.
03-08-2007, 02:27 PM
#15
Senior Member
Join Date: Jan 2007
Posts: 115
.
Overlap = torque. Even a PP peaking at 10K rpm will make more torque at 3k rpm than a streetport. The real issue here is overlap has a serious negative effect on part throttle drivability.
[/quote]
my bad i was refering to this post, ive been told the oposite overlap=hp and the less overlap= TQ
Overlap = torque. Even a PP peaking at 10K rpm will make more torque at 3k rpm than a streetport. The real issue here is overlap has a serious negative effect on part throttle drivability.
[/quote]
my bad i was refering to this post, ive been told the oposite overlap=hp and the less overlap= TQ
03-08-2007, 04:23 PM
#16
Senior Member
Join Date: Jun 2003
Location: Grand Prairie, TX
Posts: 917
Originally Posted by kuhnke' post='862695' date='Mar 8 2007, 12:27 PM
.
Overlap = torque. Even a PP peaking at 10K rpm will make more torque at 3k rpm than a streetport. The real issue here is overlap has a serious negative effect on part throttle drivability.
my bad i was refering to this post, ive been told the oposite overlap=hp and the less overlap= TQ
Yet we've got vast practical experience that consistently says otherwise, Kuhnke. I suppose it's one of those things about what ya read over the Internet or what you hear from others -- always beware of it and judge it based on its merits. Who do you believe, the guy who says his brother's cousin's roommate's girlfriend's boyfriend said so, or the guy who's actually done it?
B
03-09-2007, 06:15 AM
#18
Senior Member
Join Date: Jul 2002
Posts: 1,007
Originally Posted by heretic' post='862767' date='Mar 8 2007, 07:58 PM
Ignore the overlap. Overlap is unimportant, it is just a necessary side effect for getting sufficient port area.
I personally dont see it as a "side effect" but thats just me.
03-14-2007, 09:29 PM
#20
Senior Member
Join Date: Jan 2007
Posts: 115
Originally Posted by BDC' post='862727' date='Mar 8 2007, 03:23 PM
Yet we've got vast practical experience that consistently says otherwise, Kuhnke. I suppose it's one of those things about what ya read over the Internet or what you hear from others -- always beware of it and judge it based on its merits. Who do you believe, the guy who says his brother's cousin's roommate's girlfriend's boyfriend said so, or the guy who's actually done it?
B
well it wasent on the internet or my roommates uncles cousin, it was my teacher at school who been doing pro drags for 40+ years, but that is for pistons.