Why dont ecotecs perform better with cams
01-16-2015, 09:29 AM
#1
Why dont ecotecs perform better with cams
The variable geometry follower of the ecotec is a result of where the cam and follower join together vs lash adjuster to valve fulcrum points. I have never been able to find the base ratio(i assume 1.5 to 1) but the ending ratio at full cam lift is 1.69 to 1 . The stock valve train is based off of x amount of oil pressure for x amount of spring pressure
GM Ecotec Bolt-Ons - Cams And A Blower Make A 370 HP Mini Killer - Hot Rod Magazine
The Exh lash adjuster has to support the weight of the follower and the up force of the valve spring and it has to be able to withstand the pressure of the valve being shoved open through post combustion pressure. so the exhaust lash adjuster has to do 500x the work of the intake lash adjuster. The exhaust lash adjuster with stock springs @ 18lbs or more pounds of boost will start collapsing
The Intake lash adjuster just like the Exh lash adjuster has to support the weight of the follower and the up pressure of the valve spring but it doesent have to get shoved through post combustion pressure. The intake valve actualy gets help opening up through the positive pressure from the blower or snail so it has a much easier job then the exhaust lash adjuster
Now ALOT OF PEOPLE for years has said the Exhaust side of the head is the BIGGEST BOTTLE NECK that we need to deal with and they were somewhat right into reffering to the port. the port is part of the problem BUT the EXH lash adjuster is the main culprit as to why the ecotec makes lack luster power no matter what lift and duration you use. As explained above the Exh lash adjuster has HUGE LOAD to handle and in this article is the given time frame of the testing being done i think they figured it out but in typical fashon the testing team dident let them be privy to all they figured out.
GM Racing Ecotec Engine - Birth Of The Ultimate Import Fighter? - Turbo Magazine
So along with my dissapoint on the rollers and that article got me digging and calling and talking with those in the know now they gave me a little here and there but still wouldent give me the golden answer i had to figure it out and once i did it was confirmed by Shaver Specialties and Ray Bates. what ends up happening as said above . The stock valve train is based off of x amount of oil pressure for x amount of spring pressure. When checked @ an installed Height of 1.300 the stock spring showed 52lbs seat pressure @ .395 in lift the spring showed around 65lbs. So with that given info you can hurt performance by running stiffer springs you can actualy start collapsing the Exh lash adjuster loosing lift and duration. the more air and fuel you shove you start collapsing the Exh lash adj and then there goes lift and duration and eventually you will start breaking lash adjusters due to them bottoming out. It does not matter what generation lash adjuster you are using. They have tried shimming the lash adjuster but they failed from fatigue in the end to make the power they did they ran hyd lash adjuster on the intake and a solid on the exhaust. I dont agree with running a setup like that i feel it leaves power on the table.
The next thing you need to worry about is the angle of the follower the greater the lift the the steeper angle you get on the follower. If the angle gets to steep with the follower the easier it is to kick the follower of the lash adjuster and that goes with hyd or solid setups. Once you get to that point you either have to modify the follower for the lash adjuster to set deeper in the follower or get a different follower with a deeper pocket for the lash adjuster.
if you decide to get your cams reground you will have to know how much material is removed so you can figure out how much to add to the valve length and lash adjuster length the ratio is 1 3/4 to 1 dont ask me how to figure that out in relation to the cam base circle
Ray Bates, Shaver Specialties, gave up some info on thus Josh and Alan done some digging Tj also had input in this
GM Ecotec Bolt-Ons - Cams And A Blower Make A 370 HP Mini Killer - Hot Rod Magazine
The Exh lash adjuster has to support the weight of the follower and the up force of the valve spring and it has to be able to withstand the pressure of the valve being shoved open through post combustion pressure. so the exhaust lash adjuster has to do 500x the work of the intake lash adjuster. The exhaust lash adjuster with stock springs @ 18lbs or more pounds of boost will start collapsing
The Intake lash adjuster just like the Exh lash adjuster has to support the weight of the follower and the up pressure of the valve spring but it doesent have to get shoved through post combustion pressure. The intake valve actualy gets help opening up through the positive pressure from the blower or snail so it has a much easier job then the exhaust lash adjuster
Now ALOT OF PEOPLE for years has said the Exhaust side of the head is the BIGGEST BOTTLE NECK that we need to deal with and they were somewhat right into reffering to the port. the port is part of the problem BUT the EXH lash adjuster is the main culprit as to why the ecotec makes lack luster power no matter what lift and duration you use. As explained above the Exh lash adjuster has HUGE LOAD to handle and in this article is the given time frame of the testing being done i think they figured it out but in typical fashon the testing team dident let them be privy to all they figured out.
GM Racing Ecotec Engine - Birth Of The Ultimate Import Fighter? - Turbo Magazine
So along with my dissapoint on the rollers and that article got me digging and calling and talking with those in the know now they gave me a little here and there but still wouldent give me the golden answer i had to figure it out and once i did it was confirmed by Shaver Specialties and Ray Bates. what ends up happening as said above . The stock valve train is based off of x amount of oil pressure for x amount of spring pressure. When checked @ an installed Height of 1.300 the stock spring showed 52lbs seat pressure @ .395 in lift the spring showed around 65lbs. So with that given info you can hurt performance by running stiffer springs you can actualy start collapsing the Exh lash adjuster loosing lift and duration. the more air and fuel you shove you start collapsing the Exh lash adj and then there goes lift and duration and eventually you will start breaking lash adjusters due to them bottoming out. It does not matter what generation lash adjuster you are using. They have tried shimming the lash adjuster but they failed from fatigue in the end to make the power they did they ran hyd lash adjuster on the intake and a solid on the exhaust. I dont agree with running a setup like that i feel it leaves power on the table.
The next thing you need to worry about is the angle of the follower the greater the lift the the steeper angle you get on the follower. If the angle gets to steep with the follower the easier it is to kick the follower of the lash adjuster and that goes with hyd or solid setups. Once you get to that point you either have to modify the follower for the lash adjuster to set deeper in the follower or get a different follower with a deeper pocket for the lash adjuster.
if you decide to get your cams reground you will have to know how much material is removed so you can figure out how much to add to the valve length and lash adjuster length the ratio is 1 3/4 to 1 dont ask me how to figure that out in relation to the cam base circle
Ray Bates, Shaver Specialties, gave up some info on thus Josh and Alan done some digging Tj also had input in this
Last edited by mrbelvedere; 01-16-2015 at 10:02 AM.
01-16-2015, 09:50 AM
#4
Senior Member
I have seen gains (or rather losses) in 60-100 times with with ZZPs S1 cams on the LNFs. About 0.5 second faster 60-100 times consistantly with no tune changes and an otherwise stock engine. Boost drops 2-3 psi indicating better VE and it allows me to crank the wg duty cycle up a bit more (to bring boost back up 2-3 psi) in most cases and get around another 0.5 second off the 60-100 time.
01-16-2015, 09:55 AM
#6
I have seen gains (or rather losses) in 60-100 times with with ZZPs S1 cams on the LNFs. About 0.5 second faster 60-100 times consistantly with no tune changes and an otherwise stock engine. Boost drops 2-3 psi indicating better VE and it allows me to crank the wg duty cycle up a bit more (to bring boost back up 2-3 psi) in most cases and get around another 0.5 second off the 60-100 time.
01-16-2015, 09:59 AM
#7
The title of the thread is a little misleading, hes trying to express that ecotec's dont respond effectively to cams because of the valve train. Sure you can see gains with bigger cams, but there are seemingly big limitations with the way the valve train operates with the hydraulic lash adjusters.
01-16-2015, 10:19 AM
#9
Senior Member
The title of the thread is a little misleading, hes trying to express that ecotec's dont respond effectively to cams because of the valve train. Sure you can see gains with bigger cams, but there are seemingly big limitations with the way the valve train operates with the hydraulic lash adjusters.
Moderator
01-16-2015, 01:13 PM
#13
Senior Member
01-16-2015, 04:52 PM
#22
Curious question but, I have always been under the assumption that our hydraulic lash adjusters behave in a similar fashion to honda lost motion adjusters on vtec engines. Honda upgraded that design years ago to go from a oil fed piston setup to a spring assembly as shown in the picture below, I wonder if something similar could be adapted to maintain zero lash.
01-16-2015, 05:30 PM
#23
Curious question but, I have always been under the assumption that our hydraulic lash adjusters behave in a similar fashion to honda lost motion adjusters on vtec engines. Honda upgraded that design years ago to go from a oil fed piston setup to a spring assembly as shown in the picture below, I wonder if something similar could be adapted to maintain zero lash.
