And lets just make sure things don't get out of hand, we're supposed to discuss rather than argue.
If anyone knows something that hasn't been said or contradicts what we who've done this line of work for years (19+ years myself) have always known, just provide proof and let it be known without being tempermental.
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MOOG Certified Tech. For mods and sound clips, see profile and gallery.
Ask me why I ran "only" a 13.54.
Member: NMRA Member: White Mustang Registry #362 Member: Fuzzy Dicer
I have a "full" exhaust on my car. BBK shorty hedders, off-road h-pipe, and flowmasters. That's it. Many people tell me I am hurting my engines performance because of my "no backpressure" environment. They say to fully benefit my "otherwise stock motor", I would need to run high flow cats with my setup. Is there any truth to this statement I have made?
I have a "full" exhaust on my car. BBK shorty hedders, off-road h-pipe, and flowmasters. That's it. Many people tell me I am hurting my engines performance because of my "no backpressure" environment. They say to fully benefit my "otherwise stock motor", I would need to run high flow cats with my setup. Is there any truth to this statement I have made?
you shorty headers & h pipe are creating back pressure so you are fine with your set up.......
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Reggie
Real Racers Don't Street Race
PERIOD.......
'88 LX Hatch With A Little Of This & A Little Of That...... 10.39 @128 MPH Soon to be faster....
Step headers are a gimmick like a tornado intake thingy for fuel mileage. Mufflers are just what they are called... mufflers(sound restrictors)... there is no other reason they were invented than to restrict sound.
For a weekend car I would like to run open funny car style headers. But I wouldn't want that on the highway for a couple hours a day
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Corey
94 GT , Steeda and Maximum Motorsports suspension, cold air K&N, subframe connectors, Centerforce clutch, Pro 5.0 shifter, Hedman Ceramic equal- length headers, MAC offroad H-pipe, Magnaflow Cat-back, FMS 3.73s, Auburn Pro diff, Aluminum Driveshaft, Balanced 347, 11:1 compression, Comp xe282hr , AFR 185, BBK SSI-R, 75mm TB, 90MM MAF & 42lb/hr injectors, SCT chip and dyno tuned, MSD pro billet ditsributor.... all that and its still a wimp... must need some boost
Step headers are a gimmick like a tornado intake thingy for fuel mileage.
That where you are so wrong.......
If you check out kooks headers & what many of the pro 5.o & Nhra pro stock are running
I don't how you can compare step header to a tornado......
This will give you idea of what step header are......
this is an excerpt.....
HEADERS - I took seven sets of headers to the dyno; I was certain that one pair would have the magic.
Hooker (2 sets)
Heddman
Mac Performance
Basanni
Kooks (2 sets)
Once again, me and the lads at Westech Dyno were shocked that all of headers produced average scores within 5 points of each other. The headers had different peak horsepower and torque, but when you examine averages, the truth is revealed.
Most racers and engine builders want headers with primary and collector tube size diameters that are simply too large. My rule of thumb is to choose a header with a primary tube size, ten percent larger than the exhaust valve. Start in this range and test. In the 2004 engine master competition, most heads had 1.6" exhaust valves, and most competitors were running with 1.75" headers.
One of the more interesting tests we did while preparing at the dyno, was to run a set of 1.75" Kook's with a 3" collector VS. a 1.75" to 1.875" stepped Kook's with a merged collector. The difference in scores between the two headers was 1-2 points at best; that is 2 points out of 1,000. I've never been convinced that stepped headers or merged collectors make more power, and this test reinforced my beliefs. The two headers did have differing peak numbers, but peak is the false god...average is the true strength of the engine. Stepped headers and merged collectors are expensive. If merged collectors work, why do they work? It's my belief that they work by simply reducing the size of the collector (people choose collector diameters that are too large).
I wanted to test my size reduction theory; on the fourth day of pulls, with a standard set of 1.75" Hookers with a 3" collector, I mounted a pair of 2.5" collector reducers, inside the collector pipe. These reducers cost $25. We ran the test and picked up 2-3 average points.
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Reggie
Real Racers Don't Street Race
PERIOD.......
'88 LX Hatch With A Little Of This & A Little Of That...... 10.39 @128 MPH Soon to be faster....
Reg I am glad you brought up Stepped Headers as I was going to mention them. They create a Divergent Duct in them which will Decrease Pressure and Increase Velocity!
Reg I am glad you brought up Stepped Headers as I was going to mention them. They create a Divergent Duct in them which will Decrease Pressure and Increase Velocity!
Contrary to popular belief......
I know a little bit.......
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Reggie
Real Racers Don't Street Race
PERIOD.......
'88 LX Hatch With A Little Of This & A Little Of That...... 10.39 @128 MPH Soon to be faster....
Backpressure in the exhaust system is bad.
Overscavenging in the exhaust system is also bad.
The idea is to scavenge the exhaust gases from the cylinders just enough to make sure that none are left to contaminate the next intake charge and at the same time, avoid overscavenging because that'll pull fresh intake charge into the exhaust causing a rise in hydrocarbon emissions and a loss of performance.
Ideally what you need is a variable diameter exhaust so that you achieve optimum scavenging and maximum exhaust gas velocity over the widest rpm range possible. Not easy to achieve, hence a lot of R&D goes into tuned length pipes and selecting the optimum pipe diameter for the rpm range that you want to operate your engine at.
You could create a "variable diameter" exhaust by installing valves in the tailpipes that open and close electronically depending on rpm and load. The technology already exists for variable length/diameter intake manifolds so the same principles could be applied to the exhaust.
Backpressure in the exhaust system is bad.
Overscavenging in the exhaust system is also bad.
The idea is to scavenge the exhaust gases from the cylinders just enough to make sure that none are left to contaminate the next intake charge and at the same time, avoid overscavenging because that'll pull fresh intake charge into the exhaust causing a rise in hydrocarbon emissions and a loss of performance.
That is exactly what I've been trying to say!
I never said you want as much backpressure as possible, but there is a fine medium where an engine will perform the best.
Also, to Steelers, technically this site is for EVERYONE not just people that want to race... although it can seem like that I guess. Plus not everyone has the money for a RACE car.
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-1994 Mustang GT... K&N filter,GT40 tubular intake,BBK Full Length Headers,modified midpipe & Flowmaster muffs, timing at 12*. Best time- 14.74 @ 93.16 -Check profile for pics of our car collection! -Member of MBMCustoms Car Club - AmericanMuscle ROCKS!! - "Save a horse, drive a Mustang!"
One of the more interesting tests we did while preparing at the dyno, was to run a set of 1.75" Kook's with a 3" collector VS. a 1.75" to 1.875" stepped Kook's with a merged collector. The difference in scores between the two headers was 1-2 points at best; that is 2 points out of 1,000. I've never been convinced that stepped headers or merged collectors make more power, and this test reinforced my beliefs.
So thats about as much of and effect as a tornado make to your mileage..... 1-2 points out of 1000....
Sure there its a little bit better, but not worth the cost.
Why do all the top guys run them? Its that competetive and they are willing to burn up their money to have every little ounce of performance.
Am I missing the point? I ain't no expert....
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Corey
94 GT , Steeda and Maximum Motorsports suspension, cold air K&N, subframe connectors, Centerforce clutch, Pro 5.0 shifter, Hedman Ceramic equal- length headers, MAC offroad H-pipe, Magnaflow Cat-back, FMS 3.73s, Auburn Pro diff, Aluminum Driveshaft, Balanced 347, 11:1 compression, Comp xe282hr , AFR 185, BBK SSI-R, 75mm TB, 90MM MAF & 42lb/hr injectors, SCT chip and dyno tuned, MSD pro billet ditsributor.... all that and its still a wimp... must need some boost
Sure there its a little bit better, but not worth the cost.
Why do all the top guys run them? Its that competetive and they are willing to burn up their money to have every little ounce of performance.
Am I missing the point? I ain't no expert....
to a point you are missing the point......
I know when i went to the expense to buy Kooks Headers....
They were already expensive so why not spend the extra money to get as much as you can performance wise....
But the again for the average bolt on type build
No the expense is not worth it......
the point was being made in a hypothetical and theory sense.....
__________________
Reggie
Real Racers Don't Street Race
PERIOD.......
'88 LX Hatch With A Little Of This & A Little Of That...... 10.39 @128 MPH Soon to be faster....
That is exactly what I've been trying to say!
I never said you want as much backpressure as possible, but there is a fine medium where an engine will perform the best.
HEADERS - I took seven sets of headers to the dyno; I was certain that one pair would have the magic.
Hooker (2 sets)
Heddman
Mac Performance
Basanni
Kooks (2 sets)
Once again, me and the lads at Westech Dyno were shocked that all of headers produced average scores within 5 points of each other. The headers had different peak horsepower and torque, but when you examine averages, the truth is revealed.
must need some boost
