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LS1 / AFR Engine Dyno Numbers

 
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PostPosted: Tue Mar 09, 2004 9:46 pm    Post subject: LS1 / AFR Engine Dyno Numbers Reply with quote

AFR recently released heads for the LS1. What I found interesting is the baseline LS1 engine. Stock LS-1 Longblock, LS-6 Intake Manifold, 1 3/4"
Headers-Long Tube Style, 3" Flowmaster Mufflers. That made 428HP on the engine dyno.

Adding AFR LS-1 "205" CNC Heads, Fast Intake Manifold, Cam-224/228 @.050 .581 Lift, 78mm Ported Throttle Body resulted in 530HP@6500 and 475lbft@4900.

Here are the dyno graphs.
http://www.airflowresearch.com/ls1_dyno.htm
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2x4
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PostPosted: Wed Mar 10, 2004 8:23 am    Post subject: Reply with quote

Honestly Smoke, I'd knock 100hp off those numbers. Thier saying adding headers & exhaust will net ya 100+ horse on a bone stock engine. Isnt the factory rating somewhere around 320?

Duhh, just realized that that must be engine dyno numbers, not rear wheel! Anyway, AFR has to be the best!
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PostPosted: Wed Mar 10, 2004 11:30 pm    Post subject: Reply with quote

2x4 wrote:
Duhh, just realized that that must be engine dyno numbers, not rear wheel! Anyway, AFR has to be the best!


That's what surprised me. A near stock LS1 making 428HP.

The scary part is the AFR heads IMO aren't that impressive. You can take a set of stock heads, port them and make more power.
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PostPosted: Thu Mar 11, 2004 10:31 am    Post subject: Reply with quote

Did you get thier catalog? They list flow numbers for everything they make. My impression was that it looked ok, but not worth the $$. LS1 heads gotta be a real pretty penny!

There are some people with the regular small block heads making very impressive numbers with AFR heads, but I'm still a skeptic. Just seems like if you spent less on proven iron heads & dropped the $1000 you just saved into portwork, youd be well ahead of the game. I'd just go nuts on the stock heads you have, they have to be the factory's greatest head anyway-you felt the LS1's wrath!

Just a side note..On our S/G car we replaced the massively massaged cast heads with Brodix heads from a buddies S/C digger. We expected to go a lot faster, in the end we gained .02 . We even had the ports re-filled & done over, nothing. It does take smaller jets in the dominator now so it must be more efficient, but not worth the money at all.
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PostPosted: Thu Mar 11, 2004 11:09 pm    Post subject: Reply with quote

No I don't have their catalog. Just been all over their website.

I've read similar stories about people making huge power with AFR's and I've also read where they haven't picked up all that much.

In the LS1 world they will have to prove themselves because the factory castings work very well as it is. Several people have reported 400 RWHP using stock heads. AFR has their work cut out for them.

I can't wait to see what my new Z runs at the track.
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PostPosted: Tue Mar 16, 2004 2:10 pm    Post subject: Reply with quote

i ported the LS-6 heads for Alan Futral MotorSports's engine/car featured in new Hot Rod mag article as fastest 6 -speed car

could have gotten a lot more Flow/HP out of heads...but the LS-1 and LS-6 castings don't have enough metal on Short Turn in Intake bowls
water jacket is too close sometimes.

Hopefully the new AFR castings will correct all this and allow headporters to maxout that area ...along with being able to use 2.080 or larger intake valves -vs- stock LS-1 or LS-6 seat inserts

Also you have to be careful comparing LS-1 or LS-6 heads flow tested at just 28 inches

a bunch of times , i've Flow Tested LS-1 and LS-6 heads at 28 inches
and flow numbers looked good ....but when these same heads were flow tested at higher test pressures like 36 to 48 inches ranges...the flow numbers took a dive above .500" Lift

half of time 28 inches of test pressure is a little too slow air speed over short turn to showup flow separation problem that will occur in a live engine run down DragStrip especially with live wet flow conditions in intake ports

28 inches = 350.3 feet per second air velocity
just about half the air velocity of real engine conditions
primary reason sometimes flow tests at 28 inches do not 100.0 percent correlate to actual DragStrip ET/MPH times


live engines making peak Torque = approx 90 inches to 120 inches

90 inches = 628.03 fps

120 inches = 725.18 fps

above 120 inches or 725.18 fps Sonic Choke conditions will occur , and no further increases in pressure differential will result in increased flow .

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PostPosted: Tue Mar 16, 2004 10:49 pm    Post subject: Reply with quote

725.18 fps Sonic Choke ?

I thought the speed of sound is roughly 1120 fps depending on the air temperature?
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PostPosted: Tue Mar 16, 2004 11:16 pm    Post subject: Reply with quote

Hey MaxRaceSoftware!
For anyone who doesnt know, this guy has some very useful software for getting all the info from a timeslip. He did a breakdown of a run I did & it was unreal the info that was right there in front of me. Worth taking a look at Wink
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PostPosted: Wed Mar 17, 2004 2:57 pm    Post subject: Reply with quote

725.18 fps Sonic Choke ?

I thought the speed of sound is roughly 1120 fps depending on the air temperature?
=========================================

1120 fps => yes, you are roughly correct for mean sea level
and Standard Temperature and Pressure conditions (STP)

but also the speed of sound is "zero" in vacuum !!

so at a point or certain amount pressure differential, the actual speed of sound is much less in live running engine on Intake side

its been known for many decades or almost a Century now, by many researchers like Ricardo, Heywood, MIT, Ford, GM, Chrysler , etc along with many SAE papers on Sonic Choke conditions in Intake and Exhaust ports

recently many engine builders and headporters have used terms like
1-Port limiting Velocity
2- Inertia Block
3-Flow separation

to describe Sonic Choke conditions

Common sense tells you that its "not possible" to run the engine higher and higher in RPMs to Infinity and continue to make infinte power with infinte port velocity !

Sonic Choke occurs in all engines at a certain port velocity
and sets the point where power will ultimatelty fall off
and where pumping losses skyrocket

in larger Short Turn radius heads with straighter shot at valves like ProStock technology ..Sonic Choke can be delayed to near .70 of speed of sound (STP referrence point)

in heads like older 23 deg valve angle with more abrupt turn into bowl area ..Sonic Choke conditions will occur near .50 to .60 speed of sound (STP referrence point)

if all Ports could be made perfectly straight , then Sonic Choke conditions could be delayed to .80 to 100 percent of speed of sound

supposedly research papers have shown Wankel engine design to approch .80+ speed of sound port velocity before Sonic Choke condition occur

FlowBenches are steady-state flow measuring devices

4 Stroke engines are "Batch Processors"
"Inertia Block" with pressure differentials induce Sonic Choke conditions

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PostPosted: Wed Mar 17, 2004 11:12 pm    Post subject: Great reply Reply with quote

Glad to have Maxrace on here he knows his stuff and isin't affraid to ask the Godfather ( Joe ) for more info. Most people kill heads by hogging without study to get the numbers. Why did the Chevy h/p parts books go into detail on port shapes and turns? You run those heads and they make great h/p and don't flow as much as aftermarket heads. Point in fact a set of 482 heads a friend pulled of his 9.73 sec car to install aluminum went 10.10 after doing so. After major port work (and $$$) the car runs 9.60s. Seems like a lot of money to go backwards then ahead .13.
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PostPosted: Fri Mar 19, 2004 12:50 am    Post subject: Reply with quote

MaxRaceSoftware ... the numbers you mention for sonic choke. Are they measured? or calculated?
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PostPosted: Fri Mar 19, 2004 1:23 pm    Post subject: Reply with quote

MaxRaceSoftware ... the numbers you mention for sonic choke. Are they measured? or calculated?
============================================

i can measure sonic choke by both methods

my software calculates sonic choke to within 0 to 3 inches H2O pressure of when it will occur

but its so much easier and accurate just to probe ports with Pitot tube (velocity probe)

but i can't reveal exactly how i'm doing it or where in port or at what lifts are critical

but i can reveal this => at any point in intake port your Pitot pressure EQUALS your test pressure ...no matter how much air that head is flowing on a FlowBench ...the real amount of live engine airflow will be sonic choke limited

if that point is on the Short turn you will get localized fuel/air separation

if that point is in port itself , then Sonic choke condition will set airflow
limit .

the LS-1 and LS-6 heads do not have a sonic choke problem in port itself
but on short turn !

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PostPosted: Sat Mar 20, 2004 4:49 pm    Post subject: Reply with quote

in larger Short Turn radius heads with straighter shot at valves like ProStock technology ..Sonic Choke can be delayed to near .70 of speed of sound (STP referrence point)

in heads like older 23 deg valve angle with more abrupt turn into bowl area ..Sonic Choke conditions will occur near .50 to .60 speed of sound (STP referrence point)

if all Ports could be made perfectly straight , then Sonic Choke conditions could be delayed to .80 to 100 percent of speed of sound
--------------------------------------------------------------------------------

Real world examples=>
no matter how i port or redesign intake ports with epoxy ..in example-> 041x SBC
SuperStock SS/IA class 350 engine ....it becomes very hard to get more than 115.0 % PerCent Volumetric Efficiency on my SF-901 dyno on these engines

mostly because Sonic Choke occurs between .50 to .60 %
which sets port velocity fps
which in turn sets inertia ram-effect psi at intake valve closing point
which ultimately sets Volumetric Efficiency %


when dyno testing Comp Eliminator or ProStock type heads with higher, straighter ports that can approach .6 to .7 percent of sound before sonic choke conditions...these type engines run 120.0 to 128.0+ VE on my Dyno

the larger turn radius and straighter ports not only flow more air, but do it at higher port velocities before sonic choke condition sets limit
so at time of intake valve closing point, inertia ram-psi is higher,
Ve is higher

the more abrupt the turn inside intake or exhaust port the sooner
that port will go into Sonic Choke condition limiting real flow

the more the abrupt turn the great "shearing" or "pressure differentials" are between roof flow velocity fps and short turn velocity fps

greater pressure differentials make ports go into sonic choke sooner

Cylinder Head technology moving towards straightest possible intake port and oval port shape to keep velocity fps as high as possible (Ve %) before sonic choke limits flow

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