HQM383 wrote: ↑Tue Apr 23, 2024 6:17 am
Richard Holdener doesn't have an opinion, he has a dyno. The 2.165/1.590-inch valve combo in this lsa test also responded favourably power wise to a 108* lsa
It’s a wide open throttle dyno test from 3500-6500rpm, of course a tighter lobe separation is going to look good… for a street guy, they’re literally only testing just a little less than half the actual power range.
Like everyone sit back and take a look at what they’re actually measuring on the dyno.
The point was the standard size valve also responds to the tighter lsa as expected. I don’t think Holdeners results were anything we didn’t know.
But join the dots. DV claims the smaller valve AFR head lost out to the standard head because the smaller valve head wants a tighter lsa and the bigger valve head is closer to its ideal lsa already. Holdener test shows what we already know that the std head should also respond to the tighter lsa.
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
My chassis dyno does a rollout and measures drive-line losses.
So it is very exact as long as the wheel inertia is the same.
Wheels with more Inertia always show up as a smaller loss than they are because they act like a flywheel with stored energy during roll out.
So heavier wheels give less engine kp but as ling as the same wheels are used the comparison is good.
Harder tie down shows up as a loss and engine hp is the same.
I usually only have to tie back as I have dual serrated rollers.
Erland Cox wrote: ↑Tue Apr 23, 2024 6:54 pm
My chassis dyno does a rollout and measures drive-line losses.
So it is very exact as long as the wheel inertia is the same.
Wheels with more Inertia always show up as a smaller loss than they are because they act like a flywheel with stored energy during roll out.
So heavier wheels give less engine kp but as ling as the same wheels are used the comparison is good.
Harder tie down shows up as a loss and engine hp is the same.
I usually only have to tie back as I have dual serrated rollers.
Erland
Erland, US and OZ dyno shops very rarely use coastdown/roll down losses, almost always just use whp
The dyno in question looks like dyno dynamics/ dynotec which doesn’t have that capability to measure (just adds a % to whp if you set it up that way) but from the video on the unity motorsports youtube channel the vehicle wasn’t strapped down hard for the AFR head run as you can see it moving around
I copied the test data of both heads from the video and made a comparison. Here is a port energy density comparison between ported ls3 (as i remember it) and AFR ls3 head;
Port Energy Density comparison.png
-juhana
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A balanced person dares to stagger, and modify ports bigger
Something seems wonky here. I’ve never see an engine fall off dramatically and level off like that without something being wrong. If the air is reaching a critical velocity from being undersized, it will start falling off and remain falling off.
Are they sure they don’t have valvetrain issues or tire slip issues?
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hoffman900 wrote: ↑Wed Apr 24, 2024 10:18 am
DD49CF24-2C89-4064-9210-6E069EA0604A.png
Something seems wonky here. I’ve never see an engine fall off dramatically and level off like that without something being wrong. If the air is reaching a critical velocity from being undersized, it will start falling off and remain falling off.
Are they sure they don’t have valvetrain issues or tire slip issues?
Yes something is clearly wrong. I wish they had pulled the AFR heads one more point on the graph. As you can see at the last point the AFR was making more HP than the LS, and if you look at the slope of the curves it would have been up a good amount at the next data point.
Stan
LS_Dyno.gif
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hoffman900 wrote: ↑Wed Apr 24, 2024 10:18 am
DD49CF24-2C89-4064-9210-6E069EA0604A.png
Something seems wonky here. I’ve never see an engine fall off dramatically and level off like that without something being wrong. If the air is reaching a critical velocity from being undersized, it will start falling off and remain falling off.
Are they sure they don’t have valvetrain issues or tire slip issues?
So much missing data..
Knock retard
A/F
TIMING
RPM
It could be valve float, lifter float.. who knows.
Being that they show this in MPH you'd see tire slip on the graph.
mt-engines wrote: ↑Wed Apr 24, 2024 11:24 am
Either way.. port energy is some MADE UP BS to sell a BS computer program to chose a cam with an arbitrary lobe center.
juuhanaa wrote: ↑Wed Apr 24, 2024 11:16 am
Based on the flow curve and cross sectional areas, im not convinced the heads fit the engine well.
WAG; Maybe the air flows through the valve throat in such a way that it blocks the flow zone, reduces the available area and chokes the engine?
-juhana
If you work on a rules restricted engine, they level off when the restrictor reaches choke velocity, before falling off. They don’t suddenly dive, level off, and creep a hair back up, and hold on.
mt-engines wrote: ↑Wed Apr 24, 2024 11:24 am
Either way.. port energy is some MADE UP BS to sell a BS computer program to chose a cam with an arbitrary lobe center.
Would you expect anything else from that camp?
I don’t know how anyone can look at that graph and think “this is a good test, let me put it on Youtube”.
hoffman900 wrote: ↑Wed Apr 24, 2024 11:33 am
I don’t know how anyone can look at that graph and think “this is a good test, let me put it on Youtube”.
Its the ongoing quest for relevancy that drives it!
I’d like to think in 2024 we’d still have good content being made and shared, but this is all that seems to be left in the dust of the internet / social media age.
