Thanks Shaun, may keep an eye out for a used set.
Long tube headers, which Primary size is 'best'?
- Thread starter Shaun@AED
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So much win in this thread
Shaun just out of curiosity do you have any thoughts on kooks green cats? For those of us who have to pass emissions
Shaun just out of curiosity do you have any thoughts on kooks green cats? For those of us who have to pass emissions
the best way to do an accurate test IMO would be to take the same car, run it tuned with the same brand of 1 3/4 headers, 3 back to back pulls, get a 2 or 3 man team in there and do a swap on the exact same car, and then get it back on the dyno in 2-3 hours for 3 back to back pulls again.
We did something similar on the 15 comparing brands back to back, but not sizes.
I do think if your plans are always to stay n/a, that 1 3/4 is plenty, kooks and arh both make them, the pypes 1 3/4 to 1 7/8 is a nice option too.
Fo power adder cars, it's hard to get too much, we have 2" with 3" collectors and are getting ready to go to a 2" to 2 1/8" stepped with 4" collectors, more than most will need, but I'm guessing we pick up 50+ rwhp with the larger setup with what were making.
if you have any plans on going f/I, or think it's a remote possibility we usually err to going with the 1 7/8 setups. from what we've seen you give up a little low end, but you pick it back up top
We did something similar on the 15 comparing brands back to back, but not sizes.
I do think if your plans are always to stay n/a, that 1 3/4 is plenty, kooks and arh both make them, the pypes 1 3/4 to 1 7/8 is a nice option too.
Fo power adder cars, it's hard to get too much, we have 2" with 3" collectors and are getting ready to go to a 2" to 2 1/8" stepped with 4" collectors, more than most will need, but I'm guessing we pick up 50+ rwhp with the larger setup with what were making.
if you have any plans on going f/I, or think it's a remote possibility we usually err to going with the 1 7/8 setups. from what we've seen you give up a little low end, but you pick it back up top
most guys do the 1 7/8 simply because they are so close on the dyno, you give up a couple ponies down low and pick it up on the top
bosses are high revving, so you could make the argument, go 1 3/4 to pick a little down low, or go 1 7/8 to scream up top like the boss intake
again, most do the 1 7/8 to give growing room
thanx for clearing that out !! .. is there any1 with dyno chart who can show us in the rpm band how they differencaite at the low and at the top ?
What rpm range is the 1 3/4 better at ? (1k to 2K ? 3K? ) ... also the 1 7/8 what rpm rpm do we see better output (5k to 7k ? )
like I said the only true way to give that data accurately is a back to back set of runs, as close as you can on the same car.
take that car, make 3 back to back hits, get a 2 or 3 man crew to have the headers swapped and back on the dyno in about 3 hours, and then do it again
that would give you a true number. to quote anything without doing it that way really is just "guessing" as every car is different. same car, same day, now, whos going to spend the $$ to do that
I would do 1 7/8ths on an NA motor if it had more cubes, like one of my LSx cars, picked up everywhere on my H/C/I 99 SS by going 1 7/8ths from 1 3/4. However I don't see the point on a smaller NA 5.0, hell would probably try the 1 5/8ths Kooks to try and pick up more low-end tq.
Shaun, the 3.5" portion you're referring to is at the beginning of the axle back or is this 3.5" from xpipe/hpipe. Hope it hasnt been answered, but if you need at least 3.5", what about a GT500 quad exhaust?
FYI, the coyote uses LESS airflow than any other V8 I've worked with.
Case in point:
A customer had a V3 on his built 2V running a 15% lower pulley and 2.95 upper. Setup produced just over 600RW thru a C4 on E85 and made 18PSI boost peak (over 7K RPM). Car ran a best of 9.67 I believe.
We swapped in a stock coyote and left the V3 but ran the stock coyote crank damper and 3.7" upper. On the Dyno with E85 thru the same Trans/converter the setup put down 640RWHP and produced only 9psi at 7500.
Less airflow feeding the engine by a large margine and it made basically the same power. Car ran 9.64 the first day out.
Less air in, less air that needs to get out.
This car has 1&7/8th headers BTW. LOL
For those looking for low restriction, just keep this in mind:
At the head the exhaust exiting the cylinder is traveling at a sonic level, so this is where you can get away with some exhaust tubing restrictions.
The farther back in the system you go, the more impact restrictive exhaust has in performance. The last place you want an exhaust restriction is at the axle back.
It does not mater how good your exhaust is at the head if you push it thru a 2.0" straw at the tailpipe.
Also, the larger/longer your system, the more weight the exhaust must push out of the system. Air weighs ~.08lbs per cubic foot. 8 cylinders flowing 300CFM has mass. Over 3lbs of air flowing thru the system per second.
Case in point:
A customer had a V3 on his built 2V running a 15% lower pulley and 2.95 upper. Setup produced just over 600RW thru a C4 on E85 and made 18PSI boost peak (over 7K RPM). Car ran a best of 9.67 I believe.
We swapped in a stock coyote and left the V3 but ran the stock coyote crank damper and 3.7" upper. On the Dyno with E85 thru the same Trans/converter the setup put down 640RWHP and produced only 9psi at 7500.
Less airflow feeding the engine by a large margine and it made basically the same power. Car ran 9.64 the first day out.
Less air in, less air that needs to get out.
This car has 1&7/8th headers BTW. LOL
For those looking for low restriction, just keep this in mind:
At the head the exhaust exiting the cylinder is traveling at a sonic level, so this is where you can get away with some exhaust tubing restrictions.
The farther back in the system you go, the more impact restrictive exhaust has in performance. The last place you want an exhaust restriction is at the axle back.
It does not mater how good your exhaust is at the head if you push it thru a 2.0" straw at the tailpipe.
Also, the larger/longer your system, the more weight the exhaust must push out of the system. Air weighs ~.08lbs per cubic foot. 8 cylinders flowing 300CFM has mass. Over 3lbs of air flowing thru the system per second.
Have you tuned a car with 1 5/8 headers ? im anxious to know how is it compared to the 1 3/4 and 1 7/8 after reading this article.
Not one customer has come in with 1 & 5/8th Kooks.
This is really good info, thanks. I never really thought of it like that.
shaun can you show us what is the gap difference between the 1 3/4 and 1 7/8 from dyno charts ? even if you have different cars but same setup ...
am anxious to c a comparison and how big is the difference gap between them .
If i am in usa i would definitely find used headers and try them on my car to see the comparison lol but shipping would cost me tons here to kuwait lol .
Such a gr8 person i have so much respect for ur work and your caring to respond to ppl who have questions man ... god bless u !!!
am anxious to c a comparison and how big is the difference gap between them .
If i am in usa i would definitely find used headers and try them on my car to see the comparison lol but shipping would cost me tons here to kuwait lol .
Such a gr8 person i have so much respect for ur work and your caring to respond to ppl who have questions man ... god bless u !!!
If you guys raise the $$$ for 1 5/8ths tubes I'll put em on and be the dyno guinea pig... Jus sayin
If you guys raise the $$$ for 1 5/8ths tubes I'll put em on and be the dyno guinea pig... Jus sayin
Lol i dont mind as long as it gets shared among a couple of others to pay a reasonable price for it
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