L92 head dyno in GM High Tech
TECH Regular
Joined: Nov 2005
Posts: 459
Likes: 0
From: Arlington, TN
Not to nitpick, well yea to nitpick.
People keep mentioning Torque issue's at the lower end with this head.
The Escilade L92 has the solution for this, and the Vortec Max L76 will probably recieve it in 08 (along with the Yukon L92 in 08, or 09 anyway).
It's called a Cam Phaser.
It allows the cam to be advanced at the lower RPM's and retarded at the higher rpms.
This allows GM to use a decent cam (not the biggest or the smallest) and have the low end torque with the high end horsepower that is not seen in previous GM Small blocks.
What I would like to see is the HP and TQ comparisons between a Yukon Denali's L92 and an Escilade's L92.
Have both engines tested on the same engine dyno on the same day (using there respective computers and wiring harness's, but use dyno headers just for the fun of it).
The Yukon doesn't have VVT and should show lower readings across the powerband -vs- the Escilade's L92 with VVT. Note they have the same cam but the Escilade is listed at 403hp where the Yukon is listed at 380 and the Caddy's peak tq hits 100rpms sooner (its whats not shown that will probably drop jaws, ie under the curve numbers).
From GM's site.
Horsepower @ RPM 403@5700 (Escalade) -vs- 380@5500 (Yukon XL Denali)
Torque @ rpm 417@4300 (Escalade) -vs- 417@4400 (Yukon XL Denali)
I would like to know how much the cam is advanced in the lower rpm's for the Caddy and what the under the curve torque band looks like compared to the GMC's motor that can't adjust its cam's timing.
Okay now yall can go back to discussing velocity, flow, etc...
People keep mentioning Torque issue's at the lower end with this head.
The Escilade L92 has the solution for this, and the Vortec Max L76 will probably recieve it in 08 (along with the Yukon L92 in 08, or 09 anyway).
It's called a Cam Phaser.
It allows the cam to be advanced at the lower RPM's and retarded at the higher rpms.
This allows GM to use a decent cam (not the biggest or the smallest) and have the low end torque with the high end horsepower that is not seen in previous GM Small blocks.
What I would like to see is the HP and TQ comparisons between a Yukon Denali's L92 and an Escilade's L92.
Have both engines tested on the same engine dyno on the same day (using there respective computers and wiring harness's, but use dyno headers just for the fun of it).
The Yukon doesn't have VVT and should show lower readings across the powerband -vs- the Escilade's L92 with VVT. Note they have the same cam but the Escilade is listed at 403hp where the Yukon is listed at 380 and the Caddy's peak tq hits 100rpms sooner (its whats not shown that will probably drop jaws, ie under the curve numbers).
From GM's site.
Horsepower @ RPM 403@5700 (Escalade) -vs- 380@5500 (Yukon XL Denali)
Torque @ rpm 417@4300 (Escalade) -vs- 417@4400 (Yukon XL Denali)
I would like to know how much the cam is advanced in the lower rpm's for the Caddy and what the under the curve torque band looks like compared to the GMC's motor that can't adjust its cam's timing.
Okay now yall can go back to discussing velocity, flow, etc...
And for the record- Yes, Delwest makes the Stock LS7 Intake valves, and yes, they are a flawed design. Stock cars are dropping valves, breaking valvesprings, missing gears and ticking occurs, pull the valve covers off and find a few lash pads laying in the head.
They may have been used for years, and still are, but you have to ask your self- at what cost are they to keep them when known failures exist in this application? My customers bring me their 70, or 80k cars, spending another 1000-1500 to make the package more reliable is like an investment to them. I have a pile of Stock LS7 valves and lash pads if anyone is interested.
Louis
They may have been used for years, and still are, but you have to ask your self- at what cost are they to keep them when known failures exist in this application? My customers bring me their 70, or 80k cars, spending another 1000-1500 to make the package more reliable is like an investment to them. I have a pile of Stock LS7 valves and lash pads if anyone is interested.
Louis
Teching In
Joined: Nov 2006
Posts: 7
Likes: 0
I have a few toughts regarding to CSA, i am new here so dont be too harsh =)
I would think that it will be hard to get much above 100% VE with that massive 3.1sq.in CSA even with 6L bottom end. At least not until about 7000-7500rpm.
Those heads are supporting something like 800hp@7500rpm, that impessing =O
I think that GM desinged such a large heads to support smallish camshaft for emission reasons and to gain lots of flow to fill cylinders.
Still i am not figured out why they did so large runners as they are delivering much more than motor demands.. maby because of long runners and thick boundary layer / flow losses or maby they just could use so large CSA because of long runners with lots of inertia?
I think that if you put some overlap or "old desing" long duration cam you could really get in to trouble at the low rpm if car is supposet to be s street driven..
about measuring velocitys in flow bench.
I dont really think you can use velocity measurements from flowbench with fixed depression because you would need very high revving engine before you would hit the velocity limit in living engine. If you get too blind with bare fps figures you can en-large intake valve and runner CSA as long as bore starts to restrict flow and you allways get higher velocity in runners..
I would use it mostly for fixing velocity variations that cause flow losses and possibly fixing some shortside velocity problems, but these should also be measured with intake attached at least if there is separation problems with higher depression.
Lets see what CSAs are aftermarket companies using.. I would bet they will desing smaller CSA to support ~6500rpm for better efficiency for street cars?
I would think that it will be hard to get much above 100% VE with that massive 3.1sq.in CSA even with 6L bottom end. At least not until about 7000-7500rpm.
Those heads are supporting something like 800hp@7500rpm, that impessing =O
I think that GM desinged such a large heads to support smallish camshaft for emission reasons and to gain lots of flow to fill cylinders.
Still i am not figured out why they did so large runners as they are delivering much more than motor demands.. maby because of long runners and thick boundary layer / flow losses or maby they just could use so large CSA because of long runners with lots of inertia?
I think that if you put some overlap or "old desing" long duration cam you could really get in to trouble at the low rpm if car is supposet to be s street driven..
about measuring velocitys in flow bench.
I dont really think you can use velocity measurements from flowbench with fixed depression because you would need very high revving engine before you would hit the velocity limit in living engine. If you get too blind with bare fps figures you can en-large intake valve and runner CSA as long as bore starts to restrict flow and you allways get higher velocity in runners..
I would use it mostly for fixing velocity variations that cause flow losses and possibly fixing some shortside velocity problems, but these should also be measured with intake attached at least if there is separation problems with higher depression.
Lets see what CSAs are aftermarket companies using.. I would bet they will desing smaller CSA to support ~6500rpm for better efficiency for street cars?
On The Tree
Joined: Feb 2006
Posts: 109
Likes: 0
Bring the Noise, you ask and I deliver 
Here are links to the dyno graphs,
first the Escalade:
http://media.gm.com/us/powertrain/en...calade_SAE.pdf
Then the Yukon,
http://media.gm.com/us/powertrain/en...kon_Denali.pdf
It can be clearly seen that there is a difference, it seems that the Yukon has the cam set not to make top rpm Hp.
It also looks like the advance takes place at around 5k rpm.
Br//
Here are links to the dyno graphs,
first the Escalade:
http://media.gm.com/us/powertrain/en...calade_SAE.pdf
Then the Yukon,
http://media.gm.com/us/powertrain/en...kon_Denali.pdf
It can be clearly seen that there is a difference, it seems that the Yukon has the cam set not to make top rpm Hp.
It also looks like the advance takes place at around 5k rpm.
Br//
TECH Regular
Joined: Nov 2005
Posts: 459
Likes: 0
From: Arlington, TN
Thanks Tahoe I've wondered how there power bands would compare...
It's a shame that who ever is doing the pdf files at GM can't keep the TQ listing in the same area on the pdf files (one lists up to 900 tq and the other only to 500).
There is a noticable notch/change in the tq curve at around 1400rpm on the caddy but it's actually a decreasing ramp rate in the torque curve compared to the Yukie's which doesn't start to slope off until 1900rpm. Maybe thats torque management kicking in early along with the phaser starting the adjustments to the cam.
I'm wondering if they share the same parts for the exhaust line (they are built on the same frame, shoot it's about like comparing an Camaro to a Formula Firebird or Trans/Am).
I would still like to see the 2 motors tested on an engine dyno with torque management and other driveline friendly programs disabled.
It's a shame that who ever is doing the pdf files at GM can't keep the TQ listing in the same area on the pdf files (one lists up to 900 tq and the other only to 500).
There is a noticable notch/change in the tq curve at around 1400rpm on the caddy but it's actually a decreasing ramp rate in the torque curve compared to the Yukie's which doesn't start to slope off until 1900rpm. Maybe thats torque management kicking in early along with the phaser starting the adjustments to the cam.
I'm wondering if they share the same parts for the exhaust line (they are built on the same frame, shoot it's about like comparing an Camaro to a Formula Firebird or Trans/Am).
I would still like to see the 2 motors tested on an engine dyno with torque management and other driveline friendly programs disabled.
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FormerVendor
Joined: Jan 2002
Posts: 173
Likes: 0
From: Mpls., MN
Bring the Noise..... you are correct that variable cam timing will help, but you can't fix the port speed problem without changing the head. What we have to remember is that GM's plans for these heads are certainly far greater than just a 6.2 truck motor.... we just don't know what they are yet.
68Corvette.... you have a pretty good grasp of what's going on. We head porters can fix things to the point the castings allow us to. That said, I recommend an LS1 based head for 346 and 364 inch motors and mild to moderate 383's. Once you get beyond that power or displacement level, some form of the L92 head is going to be an awesome piece to put on these engines. It is certainly the best large scale production head produced by an American manufacturer to date.
Louis!..... you finished with that degree yet?! Tell your dad I said hi, and Merry Christmas....same goes for you. Maybe I'll see one or both of you at PRI.
Brian
HiTech Motorsport
68Corvette.... you have a pretty good grasp of what's going on. We head porters can fix things to the point the castings allow us to. That said, I recommend an LS1 based head for 346 and 364 inch motors and mild to moderate 383's. Once you get beyond that power or displacement level, some form of the L92 head is going to be an awesome piece to put on these engines. It is certainly the best large scale production head produced by an American manufacturer to date.
Louis!..... you finished with that degree yet?! Tell your dad I said hi, and Merry Christmas....same goes for you. Maybe I'll see one or both of you at PRI.
Brian
HiTech Motorsport
this could be totally impossible,but assuming the heads are too big for optimum power on a smaller engine,could you raise the port floor with epoxy to improve the short side turn and at the same time decrease the port volume for a smaller cube motor?like i said,that could be totally impractical....experts,chime in..
Last edited by 66deuce; Dec 10, 2006 at 03:17 PM.
Teching In
Joined: Apr 2006
Posts: 21
Likes: 0
Originally Posted by 66deuce
this could be totally impossible,but assuming the heads are too big for optimum power on a smaller engine,could you raise the port floor with epoxy to improve the short side turn and at the same time decrease the port volume for a smaller cube motor?like i said,that could be totally impractical....experts,chime in..
Originally Posted by Sweet35th
I just so happen to know people that do this...
wonder what the flow nos. would be like...
Originally Posted by 1MEANGTO
Hitech does this on ls1 and ls6 heads now. I'm sure brian will chime back in but the answer is yes on my heads we will be cutting the seats out and putting in smaller ones like a 2.10 or 2.08 instead of the 2.16 because there are no available aftermarkets as of yet.
Originally Posted by 66deuce
on the L92 heads?i know it's been done on the LS1-6 heads,among others...
wonder what the flow nos. would be like...
wonder what the flow nos. would be like...
Ok, here's the link:
L92 heads flowing 374cfm & exh 250cfm
https://ls1tech.com/forums/generation-iv-internal-engine/607018-l92-heads-flowing-374cfm-exh-250cfm.html
Here's the pictures:
L92 heads flowing 374cfm & exh 250cfm
https://ls1tech.com/forums/generation-iv-internal-engine/607018-l92-heads-flowing-374cfm-exh-250cfm.html
Here's the pictures:
Originally Posted by Tuf-Titan
Now this heads still need plenty of work. I would like to see myself in the chambers for one. Im still not sure if Im going to stick with the 2.150 valves or go with 2.200. I will post more pics when they are all done.
very interesting reading so far guys!! subscribing.
can anyone confirm if these heads would work well on a supercharger set-up on a 402?
i know nothing about heads/flows/velocity or any of that stuff so please be gentle on me.
im currently planning on running ported 243 ls6 heads and ls6 manifold on a built 402 for the time being but seein as though these heads are so affordable at this point and from reading the article, if this would be a better route to take i wouldnt hesitate to go to a l92/l76 set up. thanx in advance for some insight!!
can anyone confirm if these heads would work well on a supercharger set-up on a 402?
i know nothing about heads/flows/velocity or any of that stuff so please be gentle on me.
im currently planning on running ported 243 ls6 heads and ls6 manifold on a built 402 for the time being but seein as though these heads are so affordable at this point and from reading the article, if this would be a better route to take i wouldnt hesitate to go to a l92/l76 set up. thanx in advance for some insight!!
Originally Posted by TNTramair
very interesting reading so far guys!! subscribing.
can anyone confirm if these heads would work well on a supercharger set-up on a 402?
i know nothing about heads/flows/velocity or any of that stuff so please be gentle on me.
can anyone confirm if these heads would work well on a supercharger set-up on a 402?
i know nothing about heads/flows/velocity or any of that stuff so please be gentle on me.
Originally Posted by dhdenney
I don't know a whole lot about the physics of a cylinder head either but I would guess that these heads would be a good match for a supercharger since they flow so much better (than the LS6's). A 402 would be borderline small for the L92's but the addition of the supercharger would make up for that.
im not tryin to get crazy hp but if these heads would make it alittle easier to achieve my HP goals of 650rwhp without over spinning the D1 than i would jump all over these witha l76 intake.
Originally Posted by TNTramair
thats what i was thinkin myself. i know they are a great combo on a N/A application but not sure how efficient they are on a low compression set up...say 9.0 to 1 cr?? or if it would even matter b/c of the supercharger addition.
im not tryin to get crazy hp but if these heads would make it alittle easier to achieve my HP goals of 650rwhp without over spinning the D1 than i would jump all over these witha l76 intake.
im not tryin to get crazy hp but if these heads would make it alittle easier to achieve my HP goals of 650rwhp without over spinning the D1 than i would jump all over these witha l76 intake.
TECH Apprentice
Joined: Oct 2004
Posts: 329
Likes: 0
370Cfm?
Shouldn't use this on an app that makes less than 550HP.
On big head. Old days they had a "split port" or "tunnel port" basically two ports in one.
Imagine on this 370Cfm being able to have a 180Cfm head for idle-3500 and a 350cfm head for 3500-the limit
Shouldn't use this on an app that makes less than 550HP.
On big head. Old days they had a "split port" or "tunnel port" basically two ports in one.
Imagine on this 370Cfm being able to have a 180Cfm head for idle-3500 and a 350cfm head for 3500-the limit