HP boost from shorty headers
06-08-2013, 08:51 PM
#12
4th Gear Member
Join Date: Oct 2009
Location: Buffalo, New York
Posts: 1,335
The engine is rated at 300 bhp. The rule of thumb is you lose 15% through the drivetrain, so RWHP should be around 255 stock.
However, even though these engines are built on the same assembly line and technically are all identical, they are not "blueprinted" and tolerances can change slightly as they build the engines. Those slight changes can easily lead to 10-20 hp swings, so one guy might get a great engine with 265 hp at the wheels, where the next guy might get a sloppy one with only 250 at the wheels.
Also, each dyno is going to be slightly different. If the owner of the dyno gets it calibrated from the manufacturer, it should read the same as any other calibrated dyno of the same brand. That is, of course, not always the case.
Then there is ambeint conditions. Elevation, Humidity, and Temperature can easily cause 20-30% changes in horsepower. They try to correct for it by making adjustments to the math that figures your power output, but these corrections are not exactly accurate, so even on a given day, you might see different results on the same car, all other things being equal. You can't expect to see the same results from location to location.
Finally, the temp of the engine makes a huge difference. If it is heat soaked, you will see less power. So if it is driven hard then tested, the power will be less than when the car is barely warmed up to operating temp.
When you combine all these factors, you can see the identical setup make 250 rwhp at one shop, and 305 rwhp at another. Does one really have more power than the other? probably not. Are dyno numbers the "true gauge" of an engine's output? No. Is there a better gauge? Not really.
So what good is a dyno? It is a great tool to get the most power out of your engine as possible. The number is irrelevant. If you start with 250 and end with 300 and other changes to the tune only result in lower numbers, then you found the best tune you can get for power, and the dyno was used for what it is good for.
So if you want to mod your car, mod your car. I promise you a CAI and tune will make your car feel more powerful, and if someone asks you how much power you have, just make up a number, it is irrelevant anyway.
*edit* - one more note.. we have a diesel shop here that has a dyno. They go for huge torque numbers on their diesel trucks, obviously. Funny thing is, a Honda with a tuner engine went to get a dyno sheet, and ended with 305 rwhp and 740 rwtq. Obviously this was WAY off, and the dyno was set up to make the torque numbers look good. Any shop can make the dyno look how they want. The real test is how it feels when you drive it.
However, even though these engines are built on the same assembly line and technically are all identical, they are not "blueprinted" and tolerances can change slightly as they build the engines. Those slight changes can easily lead to 10-20 hp swings, so one guy might get a great engine with 265 hp at the wheels, where the next guy might get a sloppy one with only 250 at the wheels.
Also, each dyno is going to be slightly different. If the owner of the dyno gets it calibrated from the manufacturer, it should read the same as any other calibrated dyno of the same brand. That is, of course, not always the case.
Then there is ambeint conditions. Elevation, Humidity, and Temperature can easily cause 20-30% changes in horsepower. They try to correct for it by making adjustments to the math that figures your power output, but these corrections are not exactly accurate, so even on a given day, you might see different results on the same car, all other things being equal. You can't expect to see the same results from location to location.
Finally, the temp of the engine makes a huge difference. If it is heat soaked, you will see less power. So if it is driven hard then tested, the power will be less than when the car is barely warmed up to operating temp.
When you combine all these factors, you can see the identical setup make 250 rwhp at one shop, and 305 rwhp at another. Does one really have more power than the other? probably not. Are dyno numbers the "true gauge" of an engine's output? No. Is there a better gauge? Not really.
So what good is a dyno? It is a great tool to get the most power out of your engine as possible. The number is irrelevant. If you start with 250 and end with 300 and other changes to the tune only result in lower numbers, then you found the best tune you can get for power, and the dyno was used for what it is good for.
So if you want to mod your car, mod your car. I promise you a CAI and tune will make your car feel more powerful, and if someone asks you how much power you have, just make up a number, it is irrelevant anyway.
*edit* - one more note.. we have a diesel shop here that has a dyno. They go for huge torque numbers on their diesel trucks, obviously. Funny thing is, a Honda with a tuner engine went to get a dyno sheet, and ended with 305 rwhp and 740 rwtq. Obviously this was WAY off, and the dyno was set up to make the torque numbers look good. Any shop can make the dyno look how they want. The real test is how it feels when you drive it.
06-09-2013, 07:15 AM
#13
This is a good read on shorty headers on the s197 with some before and after dyno's...
http://www.mustangmonthly.com/techar...s/viewall.html
My experience with the shorty was an immediate difference in Torque (why do we always forget the other white meat now-a-days?) that they provided along with the awesome sound upgrade! In terms of HP gains, I would agree with Dan and others of +7 to 10hp.
While the longtube rules on the dyno and at the track, I have found the shorty is a great addition on the street where that torque is felt and used with every push of the throttle. Enjoy the upgrade!
http://www.mustangmonthly.com/techar...s/viewall.html
My experience with the shorty was an immediate difference in Torque (why do we always forget the other white meat now-a-days?) that they provided along with the awesome sound upgrade! In terms of HP gains, I would agree with Dan and others of +7 to 10hp.
While the longtube rules on the dyno and at the track, I have found the shorty is a great addition on the street where that torque is felt and used with every push of the throttle. Enjoy the upgrade!
07-09-2013, 01:41 PM
#14
Thread Starter
Join Date: Feb 2012
Location: Idaho
Posts: 9
Thank you to all who took the time to post! I enjoyed the knowledgable responses and I've definitely learned a lot about Dynos, torque and HP-both from my personal experiences of late and from the readings here
My ride after the install of the Flowmaster headers dyno'd with a peak 306 torque at 4480 RPMs and 318 peak HP at 6280 rpms The torque RPMs turned out to be at a slightly higher peak than a friend who has the exact same GT with a different tune. so it really does vary. Our HPs were comparably the same.
My ride after the install of the Flowmaster headers dyno'd with a peak 306 torque at 4480 RPMs and 318 peak HP at 6280 rpms The torque RPMs turned out to be at a slightly higher peak than a friend who has the exact same GT with a different tune. so it really does vary. Our HPs were comparably the same.
07-10-2013, 05:37 AM
#15
The Paranoid One
Join Date: Apr 2006
Location: Texas
Posts: 5,320
If you are getting headers for power, don't go shorties.
Not worth the money.
Won't give you the gain long tubes will and won't help you
down the road to gain more HP with your mods.
I HIGHLY doubt getting 8hp from shorties.
I'd call it a difference in some other factor variation
in the dyno such as temperature when the dyno was
run or engine temp etc.
In other words I'd view it as a false gain number.
I'd say usually 3-5hp if any gain at all.
The difference in you and your friends trq and hp
99% chance is from the tune
Not worth the money.
Won't give you the gain long tubes will and won't help you
down the road to gain more HP with your mods.
I HIGHLY doubt getting 8hp from shorties.
I'd call it a difference in some other factor variation
in the dyno such as temperature when the dyno was
run or engine temp etc.
In other words I'd view it as a false gain number.
I'd say usually 3-5hp if any gain at all.
The difference in you and your friends trq and hp
99% chance is from the tune
Last edited by Blacksmoke; 07-10-2013 at 05:42 AM.
07-11-2013, 08:09 AM
#17
Thread Starter
Join Date: Feb 2012
Location: Idaho
Posts: 9
Flowmater Shorties
My shorties were a FREE install from Flowmaster so got the mod w/out the expense or re-tune due to O2 sensor placement, etc., which is ALWAYS acceptable. I posted my dyno numbers here because there were several inquiries in previous posts but wasn't implying a huge HP boost from the shorties. I am positive the tune made a diff. between the two GT's mentioned on dyno but thought it was interesting to note. Any dyno number can be manipulated for specific purposes and it's understood, as you said, many variable affect the outcome.
I'll go with the 6-8 hp boost that various resources and the experts say shorties give and the sound and feel add credibility to that so there's no rain on my parade Bottom line-I'm a member of the small population that gets to drive EXACTLY what I want to drive, my dream car, everyday! It's personal and it makes me happy and we all know that's what counts. I enjoy adding mods when and where I can and the tune was the icing on the cake mechanically
I'll go with the 6-8 hp boost that various resources and the experts say shorties give and the sound and feel add credibility to that so there's no rain on my parade
Bottom line-I'm a member of the small population that gets to drive EXACTLY what I want to drive, my dream car, everyday! It's personal and it makes me happy and we all know that's what counts. I enjoy adding mods when and where I can and the tune was the icing on the cake mechanically
07-11-2013, 08:26 PM
#20
6th Gear Member
Join Date: Jan 2008
Location: North Pole
Posts: 6,716
Hi Diabolical! 
Long time no speak.
I had shorty's on my vortech supercharged 4.6 and though it didn't make a difference in power, it did make it a lot cooler in the engine bay. I ran JBA ceramic titanium shorty headers and they were always cool to the touch...
Long time no speak.
I had shorty's on my vortech supercharged 4.6 and though it didn't make a difference in power, it did make it a lot cooler in the engine bay. I ran JBA ceramic titanium shorty headers and they were always cool to the touch...