perfect header pics?
01-19-2007, 09:03 PM
#31
Burning Brakes
Join Date: May 2005
Location: St Johns, FL
Posts: 794
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by pzull
[snip]
If we drive the car like a sedan on the road then I think the short B&B non equal length headers will feel perkier but if we drive is a spirited fashion where gear changes result in rpms seldom falling below 2.5k-3k, I believe a short equal length headers will be beneficial (Marcos dont seem to have optimised to be shortest possible)
Of course I am only theorising and have no real world proof.......but may soon have.
If we drive the car like a sedan on the road then I think the short B&B non equal length headers will feel perkier but if we drive is a spirited fashion where gear changes result in rpms seldom falling below 2.5k-3k, I believe a short equal length headers will be beneficial (Marcos dont seem to have optimised to be shortest possible)
Of course I am only theorising and have no real world proof.......but may soon have.
When I bought the Marco headers, I still had a CIS car with B&B headers. After the change, I took it to the dyno and found I lost about 12 hp - but it was on a Dynojunk, sorry, Dynojet dyno. I then took it to a dyno dynamics dyno where we could load the engine. I was STILL down a dozen HP on a static 0 - redline pull. Pissed me off. Then, we loaded the engine at 3000 rpm and turned it loose. It gained 20 hp. So, why the swing? The equal length, larger diameter pipes were not designed for low rpm hp, nor for snappy spooling. But the 3000 rpm to redline showed awesome torque and hp numbers over the B&B.
Now that I have EFI, I can "tune" the torque much better and have improved the spool time over the smaller, short B&B pipes (granted, that was a CIS engine). As for the top end capability of these headers, I have not been able to find it. One additional note to these headers - the wastegate circuit. Whatever boost I dial in with the EBC, the circuit nails it every time at all engine loads.
Years ago when Doc Emmard was playing with turbos, he used pipes that kept each bank of cylinders separate right up to the divided hot side of the turbo. He could gain another 10 - 12 hp with this design. He said he got the idea from his diesel mechanic days since this is a standard design feature in truck motors.
As for the comment on Marco's design on length optimization, they are as short as you can get for a street turbo. He even uses the more expensive tighter radius (higher grade of mandrel bent SS) pipes. If you want short, buy short pipes...
01-20-2007, 02:13 AM
#32
Burning Brakes
Join Date: Nov 2002
Location: 2 ends of the Pacific
Posts: 761
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by DonE
Your last sentance is really the problem.
When I bought the Marco headers, I still had a CIS car with B&B headers. After the change, I took it to the dyno and found I lost about 12 hp - but it was on a Dynojunk, sorry, Dynojet dyno. I then took it to a dyno dynamics dyno where we could load the engine. I was STILL down a dozen HP on a static 0 - redline pull. Pissed me off. Then, we loaded the engine at 3000 rpm and turned it loose. It gained 20 hp. So, why the swing? The equal length, larger diameter pipes were not designed for low rpm hp, nor for snappy spooling. But the 3000 rpm to redline showed awesome torque and hp numbers over the B&B.
Now that I have EFI, I can "tune" the torque much better and have improved the spool time over the smaller, short B&B pipes (granted, that was a CIS engine). As for the top end capability of these headers, I have not been able to find it. One additional note to these headers - the wastegate circuit. Whatever boost I dial in with the EBC, the circuit nails it every time at all engine loads.
Years ago when Doc Emmard was playing with turbos, he used pipes that kept each bank of cylinders separate right up to the divided hot side of the turbo. He could gain another 10 - 12 hp with this design. He said he got the idea from his diesel mechanic days since this is a standard design feature in truck motors.
As for the comment on Marco's design on length optimization, they are as short as you can get for a street turbo. He even uses the more expensive tighter radius (higher grade of mandrel bent SS) pipes. If you want short, buy short pipes...
When I bought the Marco headers, I still had a CIS car with B&B headers. After the change, I took it to the dyno and found I lost about 12 hp - but it was on a Dynojunk, sorry, Dynojet dyno. I then took it to a dyno dynamics dyno where we could load the engine. I was STILL down a dozen HP on a static 0 - redline pull. Pissed me off. Then, we loaded the engine at 3000 rpm and turned it loose. It gained 20 hp. So, why the swing? The equal length, larger diameter pipes were not designed for low rpm hp, nor for snappy spooling. But the 3000 rpm to redline showed awesome torque and hp numbers over the B&B.
Now that I have EFI, I can "tune" the torque much better and have improved the spool time over the smaller, short B&B pipes (granted, that was a CIS engine). As for the top end capability of these headers, I have not been able to find it. One additional note to these headers - the wastegate circuit. Whatever boost I dial in with the EBC, the circuit nails it every time at all engine loads.
Years ago when Doc Emmard was playing with turbos, he used pipes that kept each bank of cylinders separate right up to the divided hot side of the turbo. He could gain another 10 - 12 hp with this design. He said he got the idea from his diesel mechanic days since this is a standard design feature in truck motors.
As for the comment on Marco's design on length optimization, they are as short as you can get for a street turbo. He even uses the more expensive tighter radius (higher grade of mandrel bent SS) pipes. If you want short, buy short pipes...
Anyway your experience seem to match what I was saying that a short equal length would be OK if you shifted at 2.5-3k rpm (meaning starting revs after shifting not before shifting)
The only example of marco I've seen are the minutely small pics on this board and it looked like the longest pipe wasn't taking the shortest route and then making all other pipes that length. The secondary pipe is also not equal in length. Maybe the pics were misleading as they were really small.
Doesn't the B&B keep each bank separate until they merge at the exhaust inlet of the turbo?
01-20-2007, 03:53 AM
#33
Not Forgotten
Join Date: Apr 2006
Location: South East, UK
Posts: 1,215
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by NineMeister
For up to 500hp we use a 1.5" primary pipes to maximise gas velocity which increases the scavenge efficiency on overlap.
Here is an example of maximising the area under the curve incomparison to a standard 930. Jon's engine would be excellent on track, boosts early, strong midrange and hanging on to the redline with a power peak above 6000. This engine runs 1.5" unequal length primaries.
Here is an example of maximising the area under the curve incomparison to a standard 930. Jon's engine would be excellent on track, boosts early, strong midrange and hanging on to the redline with a power peak above 6000. This engine runs 1.5" unequal length primaries.
I never tire of looking at my dyno graph
01-20-2007, 06:56 AM
#34
Addict
Rennlist
Site Sponsor
Rennlist
Site Sponsor
Originally Posted by pzull
saying it in pictures....
Actually there is a lot more to his than just pipe lengths and diameters: collector design is critical, as is keeping the left/right banks separated; the head/manifold interface can also be reworked to provide anti-reversion; the list goes on and on.
My view is that for 99% of applications, if the engine is tuned correctly (now there's a subject!), a 9m/B&B style unequal length header will give the maximum area under the curve for road engines up to 500+hp.
