Turbo manifold styles- Absurdflow lowmount vs ramhorn, which for maximum power?
#22
http://i89.photobucket.com/albums/k2...301/BMW_02.jpg
i am pretty sure bmw knew what would make the best power and the best low end torque when they built this manifold for their 1980s 4cyl f1 engine. that engine made over 1000hp at 2.0l displacement on 74 psi during qualifying, and thats with older turbo technology then we have today.
i am pretty sure bmw knew what would make the best power and the best low end torque when they built this manifold for their 1980s 4cyl f1 engine. that engine made over 1000hp at 2.0l displacement on 74 psi during qualifying, and thats with older turbo technology then we have today.
5.5 bar around 1300hp
almost 80psi
They also used different fuels than we do back than.
#27
i am pretty sure bmw knew what would make the best power and the best low end torque when they built this manifold for their 1980s 4cyl f1 engine. that engine made over 1000hp at 2.0l displacement on 74 psi during qualifying, and thats with older turbo technology then we have today.
To help the OP understand...
If your goal is to reduce the boost threshold of a 2871 or 3071 turbo from say 4k RPM to 3.5k RPM on our cars, long exhaust runners are counter to your goal. A low mount short ram will be superior while sacrificing very little in high RPM exhaust flow/max power.
Long runner, tuned, equal length, turbo manifolds are a max power design decision. The design criterion is for max exhaust flow in an RPM window well above boost threshold. Time to reach target boost (aka spool) is minimized within this RPM window.
The reason you see these manifolds across all forms of racing is because racing is essentially sustained high RPM operation. The time spent from idle to 4k RPM is so small it is irrelevant
While it is all about "area under the curve" you only measure the area under the portion of the curve which is relevant to your operating range. Racing neglects a portion of the curve which is of key relevance to most of us.
That is all, carry on.
#30
Some rough numbers to think about
1.8l exhaust manifold gasket hole perpendicular to flange -- 48.8mm X 29.8mm, Area = 1264 mm^2
Stock 99 head perpendicular to throat-- 45mm X 23mm, Area = 921 mm^2
Ported 99 head (Replika or FM) perpendicular to throat -- 47mm X 24mm Area = 1004 mm^2
1-1/4” schedule 40 pipe -- ID 35mm Area = 962mm^2
1-1/2” schedule 40 pipe – ID 41mm Area = 1320 mm^2
Area 4 of the runners gets necked down to before entering the volute on the turbo is ~792 mm^2 as a guess.
Bob
1.8l exhaust manifold gasket hole perpendicular to flange -- 48.8mm X 29.8mm, Area = 1264 mm^2
Stock 99 head perpendicular to throat-- 45mm X 23mm, Area = 921 mm^2
Ported 99 head (Replika or FM) perpendicular to throat -- 47mm X 24mm Area = 1004 mm^2
1-1/4” schedule 40 pipe -- ID 35mm Area = 962mm^2
1-1/2” schedule 40 pipe – ID 41mm Area = 1320 mm^2
Area 4 of the runners gets necked down to before entering the volute on the turbo is ~792 mm^2 as a guess.
Bob
#31
To help the OP understand...
If your goal is to reduce the boost threshold of a 2871 or 3071 turbo from say 4k RPM to 3.5k RPM on our cars, long exhaust runners are counter to your goal. A low mount short ram will be superior while sacrificing very little in high RPM exhaust flow/max power.
If your goal is to reduce the boost threshold of a 2871 or 3071 turbo from say 4k RPM to 3.5k RPM on our cars, long exhaust runners are counter to your goal. A low mount short ram will be superior while sacrificing very little in high RPM exhaust flow/max power.
See actual data.
Love you back Mikeypoo. <3
#32
Boost threshold is why. Lowering the boost threshold of a large turbo is key to achieving "max power" as in "maximizing the area under the curve", when you can take advantage of a wide power band but can't rev to the moon.
#33
You asked why some members on this board ranked an Absurdflow low mount (aka unequal length mini ramhorn) higher than an equal length long runner ram horn.
Boost threshold is why. Lowering the boost threshold of a large turbo is key to achieving "max power" as in "maximizing the area under the curve", when you can use take advantage of a wide power band and can't rev to the moon.
Boost threshold is why. Lowering the boost threshold of a large turbo is key to achieving "max power" as in "maximizing the area under the curve", when you can use take advantage of a wide power band and can't rev to the moon.
You should notice that the dyno graphs were /exactly/ the same until the ramhorn 'kicked in' though. That is interesting in and of itself.
#36
I think the results of a test like that on a bp would yield less drastic peak power differences due to the much worse flowing head we have, but the overall results would be similar IMO.
I remember a thread where begi did a back to back of their log vs s4 and it was something like 7-10hp difference up top? Don't quote me on those numbers but it was something small like that.
Now since an absurdflow will flow circles around a log (pun intended) I'm going to guess the difference between it and a ramhorn would also not be very drastic, but the "top power" winner will still be the ramhorn. IMO
I remember a thread where begi did a back to back of their log vs s4 and it was something like 7-10hp difference up top? Don't quote me on those numbers but it was something small like that.
Now since an absurdflow will flow circles around a log (pun intended) I'm going to guess the difference between it and a ramhorn would also not be very drastic, but the "top power" winner will still be the ramhorn. IMO
#37
mkturbo.com
iTrader: (24)
Join Date: May 2006
Location: Charleston SC
Posts: 15,177
Total Cats: 1,681
So I have been talking to Tim about possibly building me a V-Band setup. I have asked him about a few of his designs and these are what he has sent me so far. What one do you guys think would work the best.
1.
2.
3.
4.
We also have Abe's ramhorn as follows.
5.
1.
2.
3.
4.
We also have Abe's ramhorn as follows.
5.
#38
I've been talking to Shuiend about this, linked him to Abe's setup. There's a few people interested in a ramhorn at the moment, at least.
So far Abe's setup still looks like it would flow the best, and it seems to be closest to what I'm seeing from drag cars, specifically turbo Honda B/K series engines. Full race, for example.
So far Abe's setup still looks like it would flow the best, and it seems to be closest to what I'm seeing from drag cars, specifically turbo Honda B/K series engines. Full race, for example.