Port Energy Anomoly?

[digger]

Dyno test shows "better" heads made less power

head test data


dyno sheet and explanation


the claims made are that the cam LSA was more optimal for the stock heads vs the AFR.

To me this looks like a chassis dyno sheet, seems something else at play besides the heads?

[Tom68]

Smaller valve head made less top end more bottom end, no surprises there.
Same thing a month earlier.

AFR may have to get on the front foot with this one and explain what the head is meant to do.

[HQM383]

Dyno test shows "better" heads made less power

head test data


dyno sheet and explanation


the claims made are that the cam LSA was more optimal for the stock heads vs the AFR.

To me this looks like a chassis dyno sheet, seems something else at play besides the heads?

He is claiming it’s a credible A/B test which tells me that nothing but the cylinder heads, appropriate valves and necessary gaskets were interchanged.

According to measured metrics the aftermarket heads flow more, have better coefficient of discharge, better velocity and above average “port energy” yet can’t make at least the same peak hp as a stock head with the same cam? If it’s all about valve size why are we worrying about flow bench numbers and development, increasing coefficient of discharge and porting for velocity? Has to be something more to it. Disclosure of full test procedure and what was changed on the engine when heads were swapped would go a long way. Has he unwittingly debunked port energy?

The scrip is already written for the next episode where he will change the cam for tighter lsa that will boost mid range torque no matter the heads used. Power will of course go up and DV will then claim he was right and the lsa was wrong with the AFR heads all along “and here’s the proof!”

[juuhanaa]

Observations from a hobbyists point of view; The flow curve shows possible intake port stability/air speed problems at higher lifts, where the port energy also drops like a tail.

Heres one head im working on that i expect will help the car out of corners and also have good top speed. (igonore the exhaust)

megane f7r IOP.png

IMG20240411191627.jpg

- juhana

[SpeierRacingHeads]

Observations from a hobbyists point of view; The flow curve shows possible intake port stability/air speed problems at higher lifts, where the port energy also drops like a tail.

Heres one head im working on that i expect will help the car out of corners and also have good top speed. (igonore the exhaust)


megane f7r IOP.png


IMG20240411191627.jpg



- juhana

I don't know what is being claimed in the videos, I didn't watch them, not my claim. However, Juhana nailed it!

Ever see a engine dyno and peak at say 7400 and at 8200 only looses 25hp? That is 100% flow curve. Regardless of cam lift.

[learner1]

None of these camparisons are really worth much regardless of who's doing them. If you're only changing heads then all you're doing is determining which heads are better for the existing cam or vise/versa. Even then the lift curve of the intake and exhaust lobes won't be optimal and the lift curves are even more important in my opinion. if Mike isn't designing the lobe profile for your cylinder heads you're losing out.

[SpeierRacingHeads]

Observations from a hobbyists point of view; The flow curve shows possible intake port stability/air speed problems at higher lifts, where the port energy also drops like a tail.

Heres one head im working on that i expect will help the car out of corners and also have good top speed. (igonore the exhaust)


megane f7r IOP.png


IMG20240411191627.jpg



- juhana

I don't know what is being claimed in the videos, I didn't watch them, not my claim. However, Juhana nailed it!

Ever see a engine dyno and peak at say 7400 and at 8200 only looses 25hp? That is 100% flow curve. Regardless of cam lift.

LOL

Nice first post!

Laugh all you want, it's 100% truth.

[KnightEngines]

I don't know what is being claimed in the videos, I didn't watch them, not my claim. However, Juhana nailed it!

Ever see a engine dyno and peak at say 7400 and at 8200 only looses 25hp? That is 100% flow curve. Regardless of cam lift.

LOL

Nice first post!

Laugh all you want, it's 100% truth.

Yep, a flow curve that never backs up will always make more hp & hold that power longer than a head with even a 20cfm stronger flow curve that backs up even .100" lift above valve lift - all else being equal.
I've seen it multiple times on the dyno - a 'weak' flowing head that is dead stable making more power than the flow curve suggests it can.

[HQM383]

Video 1 neither head is backing up in flow.

[Tom68]

Standard cam for DV's?
Then it's all about curtain area.
Both the ports are probably too big for a small cam.

[mt-engines]

Standard cam for DV's?
Then it's all about curtain area.
Both the ports are probably too big for a small cam.

Big ports don't need big cams. DV showed us nothing again.

[Tom68]

Standard cam for DV's?
Then it's all about curtain area.
Both the ports are probably too big for a small cam.

Big ports don't need big cams. DV showed us nothing again.

No but the AFR has a smaller intake valve.

[BLSTIC]

LOL

Nice first post!

Laugh all you want, it's 100% truth.

Yep, a flow curve that never backs up will always make more hp & hold that power longer than a head with even a 20cfm stronger flow curve that backs up even .100" lift above valve lift - all else being equal.
I've seen it multiple times on the dyno - a 'weak' flowing head that is dead stable making more power than the flow curve suggests it can.

By "backing up" do you mean where flow goes down with increasing lift?

Would you see this happening on those heads at lower lifts with higher depression? Assuming you had a big enough bench anyway

[HQM383]

Standard cam for DV's?
Then it's all about curtain area.
Both the ports are probably too big for a small cam.

Big ports don't need big cams. DV showed us nothing again.

No but the AFR has a smaller intake.

But by his measures the head with the smaller intake valve has the potential to move more air.

[Tom68]

Big ports don't need big cams. DV showed us nothing again.

No but the AFR has a smaller intake.

But by his measures the head with the smaller intake valve has the potential to move more air.

And it did at lower engine speeds.

I wonder whether it's the old flow bench doesn't pull as hard as a high revving engine causing the discrepency.