Your on a built motor with upgraded valve springs correct? How many lbs of boost were you making, and on controller or springs?
EDP 7475 Results
- Thread starter Big Q
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Your on a built motor with upgraded valve springs correct? How many lbs of boost were you making, and on controller or springs?
I see no "falling on its face" at 6k. The power may not be climbing as rapidly but is sure as heck isn't dropping like a brick.
A turbo pwer curve will not continue to climb like that of a centri as the boost is constant and not tracking RPMs. Also, cam timing has a great affect on where power peaks. Has anyone logged cam timing while on the dyno?
Valve float on the exhaust side can be caused by excessive back pressure. With that, what is the ar? Has anyone taken pressure readings between the head and turbo?
I agree that installing new valve springs wont fix the problem if high back pressure is keeping the exh valves open. The root cause has to be fixed.
A turbo pwer curve will not continue to climb like that of a centri as the boost is constant and not tracking RPMs. Also, cam timing has a great affect on where power peaks. Has anyone logged cam timing while on the dyno?
Valve float on the exhaust side can be caused by excessive back pressure. With that, what is the ar? Has anyone taken pressure readings between the head and turbo?
I agree that installing new valve springs wont fix the problem if high back pressure is keeping the exh valves open. The root cause has to be fixed.
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It's already been established that the 7475 and 7675 cea are to small for this engine to make power to 7000 rpm. Both have .96 ar t4 housings.
My guess would be that back pressure sails above 6000 rpm.
Having big pressure drops across the cold side can have more than 1 route cause also.
The inlet boost vs exhaust back pressure ratio is going to be different if reading boost at the motor or at the comp with that much loss.
None of the cars fall at 6000 rpm. They are taking a dive by 6500.
Some thermal images of the entire system would be nice. My guess would be that things get pretty toasty at the turbo
My guess would be that back pressure sails above 6000 rpm.
Having big pressure drops across the cold side can have more than 1 route cause also.
The inlet boost vs exhaust back pressure ratio is going to be different if reading boost at the motor or at the comp with that much loss.
None of the cars fall at 6000 rpm. They are taking a dive by 6500.
Some thermal images of the entire system would be nice. My guess would be that things get pretty toasty at the turbo
Here is the kicker. The spool isn't super fast nor is it super slow. Hell mine at idle doesn't have enough drive pressure to keep the wheel spinning (mite spin if it was a bb unit) with a 3" down pipe.
2.5 inch piping is what is coming off of each bank of the motor, if they merge to 2.5, that creates a huge restriction and back pressure problem.
that would hurt an N/A car
JPC merges smoothly to 3 inch pipe to feed the t4, very simple math tells you going from 2.5 inch pipe to a 3 inch pipe is a 44% increase in airflow, and that's HUGE.
that would hurt an N/A car
JPC merges smoothly to 3 inch pipe to feed the t4, very simple math tells you going from 2.5 inch pipe to a 3 inch pipe is a 44% increase in airflow, and that's HUGE.
Show us this "basic" equation. Keeping in mind the inside of these turbo's exhaust housings is MUCH smaller than 2.5"
I'd like to know the truth here also
Cams aren't going to care that the valves are floating. Specially with the engine loaded at full tilt.
You want the air to speed up at the turbo, you don't. . . however, want the exhaust having trouble getting out of the engine.
2.5 inch vs 3 inch
(3.1415 x 25^2) = 1963.4
(3.1415 x 30^2) = 2827.3
2827.3 / 1963.4 = 1.44
44% more airflow
Where are you getting the 3.1415 ?
As long as the air in the hot side doesn't reach the speed of sound (anywhere in the hot side pre turbo) the pipe dia isn't the issue. If the air isn't moving at the speed of sound increasing dia will decrease drive pressure.
This isn't factoring temperature. In both EDP and JPC hot sides, the exhaust gases have to travel pretty far before reaching the turbo. These runs (length of pipe) also play a factor.
In boost and at rpm both wastegates are open. This is also going to play a factor.
Basic "math" isn't going to cut it here
What should I be looking for to tell if mine is falling off or falling on its face? Last night I kept an eye on my boost gauge and tachometer at the same time and i saw no drop in boost shifting up to 7k rpm. The dial stayed roght where it was at
I have something completely different I am thinking of related to VCT under certain situations.
Anyone have a graph or data from a JPC car running a 7675? Would be interested in seeing the curve at 6500+
Edit: JPC car with their standard kit.
Pi is used to find the area of a circle. You are missing a huge component here, if the exhaust on the hot side is too small then the air will never get out of the combustion chamber for the exhaust valves, thus not making more horsepower and falling on its face
This is why you do your homework before buying anything if you want a kit like this jpc is the best
Whether your supercharged or turbo it always boils down to a well tuned exhaust and airflow. The more air you can move through the engine efficiently the more power your going to make. You can stuff the engine with air easily but you need to get rid of it too. Sounds like either a up pipe or down pipe problem.
I guess we will have to start getting into exhaust pulse, scavenging, and balance?
I know we can at least agree on 1 thing? Exhaust gasses do not burn twice and that slapping stiffer springs in the motor to prevent float is a bandaid
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