Hey, any HR guys spinning well past 7500rpms
01-07-2011, 02:06 PM
#23
Out of curiosity I would love to see what the PCM thinks is happening compared to what yourbox and tach think, and I would also like to see what settings and tables it is using after 7200. For 6900-7200 as well for that matter to see if its using changing values after 7k or still running the 6900 settings.
I've never heard of an OBDII car breaking 7200rpms.
01-07-2011, 02:53 PM
#26
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Do you happen to have a datalog of any runs?
Out of curiosity I would love to see what the PCM thinks is happening compared to what yourbox and tach think, and I would also like to see what settings and tables it is using after 7200. For 6900-7200 as well for that matter to see if its using changing values after 7k or still running the 6900 settings.
I've never heard of an OBDII car breaking 7200rpms.
Out of curiosity I would love to see what the PCM thinks is happening compared to what yourbox and tach think, and I would also like to see what settings and tables it is using after 7200. For 6900-7200 as well for that matter to see if its using changing values after 7k or still running the 6900 settings.
I've never heard of an OBDII car breaking 7200rpms.
01-07-2011, 02:58 PM
#27
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Ok I am unclear what point you are making here, sorry. And I called a friend of mine that has a 93 Camaro and he said he was shifting his at 7500 everytime. But by factory tach that was more like 7200-or so. He said that the computer once it reaches a certain point it just keep the same timing and fuel, it wasnt able to be tuned that high. But our cars kept on making power in thos ranges on the dyno
Last edited by THADD; 01-07-2011 at 04:31 PM.
01-07-2011, 02:59 PM
#28
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Yes they are, as I stated they are lazy. I am not really using my tach but I am using my Mallory box and a programmable shift light for rev limiter and shift points
Last edited by THADD; 01-07-2011 at 03:31 PM.
01-07-2011, 04:13 PM
#29
[QUOTE=THADD;14330491]Yes they are, as I stated they are lazy. I am not really using my tach but I am using my Mallory box and a programmable shift light for rev limiter and shift points
but do the vary from car to car?
so if you set your box at 7350 it will hit the limiter?
but do the vary from car to car?
so if you set your box at 7350 it will hit the limiter?
01-07-2011, 04:27 PM
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Ok called my tuner and he said that most the factory pcm's will shut down at 7000 give or take. Its not a dead set number across the board. Some will go higher but will eventually have the same problem. Mine just so happen to go a little higher. He said he and another guy bought a bunch of pcm's just to get one that would go higher. He said they all were close, but the lowest and highest were separated by 3-400 rpms
01-08-2011, 01:45 AM
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Ok called my tuner and he said that most the factory pcm's will shut down at 7000 give or take. Its not a dead set number across the board. Some will go higher but will eventually have the same problem. Mine just so happen to go a little higher. He said he and another guy bought a bunch of pcm's just to get one that would go higher. He said they all were close, but the lowest and highest were separated by 3-400 rpms
What h/c combo are you runnin in a HR setup that allows your motor to even keep on makin power even past 6800-6900 rpms. Im not callin you a liar at all but I got a pretty stout HR setup and it flatens out soon as 6800 hits man.
01-08-2011, 11:01 AM
#38
It is extremely hard to keep an HR stable pass 7k. Not saying its impossible, but it would take some high dollar parts to do so.
Generally, the spring pressures needed to keep a valvetrain stable at those rpms are too much for HR lifters. Then you need very stiff pushrods, expensive springs to keep the seat pressure low but open pressure high enough to control the valve, and all lightweight hardware.
I really see no need to go through all that, and would suggest someone thinking to go that route to seriously consider a solid roller.
Generally, the spring pressures needed to keep a valvetrain stable at those rpms are too much for HR lifters. Then you need very stiff pushrods, expensive springs to keep the seat pressure low but open pressure high enough to control the valve, and all lightweight hardware.
I really see no need to go through all that, and would suggest someone thinking to go that route to seriously consider a solid roller.
01-08-2011, 11:45 AM
#39
The factory tach's are often off, but here is my experience.
Many of the LT1 tachs I datalogged read high, mine read 200 higher than the engine, meaning 6800 engine was 7000 tach.
Now as for these 7200-7500 readings, they do not jive with the factory tach as it only goes to 7000.
As for the 7500rpm HR original question... if you use the zero lash (min preload) type of lifter, then yes it wil rev like a solid, given the proper springs & correct lobe geometry to support higher rpm. These Morel & Schubeck type lifters have minimum plunger travel so the plunger only depresses under 0.050" (just enough to allow for thermal expansion characteristics of the engine), limiting the amount that the lifter can collapse. This limits the lift/duration loss that a typical hydraulic roller can exhibit due to the compressibility of the stock type lifter. At the same time, a typical hydraulic lifter operates with about 0.050" preload, meaning that if/when the lifter pumps up, it holds the valve open this amount in effect losing power by "floating" the valves. When using the zero lash type lifter, this preload is set at approx 0-0.003" preload, so that the lifter cannot pump up & hold the valve open.
With all this creativity, you may ask how different is this from a solid roller. Truely there is very little difference at this point & some have even been known to use solid lifters on a hydraulic cam for his reason. Discuss this with your cam grinder if you want to go this way to ensure compatibility.
Many of the LT1 tachs I datalogged read high, mine read 200 higher than the engine, meaning 6800 engine was 7000 tach.
Now as for these 7200-7500 readings, they do not jive with the factory tach as it only goes to 7000.
As for the 7500rpm HR original question... if you use the zero lash (min preload) type of lifter, then yes it wil rev like a solid, given the proper springs & correct lobe geometry to support higher rpm. These Morel & Schubeck type lifters have minimum plunger travel so the plunger only depresses under 0.050" (just enough to allow for thermal expansion characteristics of the engine), limiting the amount that the lifter can collapse. This limits the lift/duration loss that a typical hydraulic roller can exhibit due to the compressibility of the stock type lifter. At the same time, a typical hydraulic lifter operates with about 0.050" preload, meaning that if/when the lifter pumps up, it holds the valve open this amount in effect losing power by "floating" the valves. When using the zero lash type lifter, this preload is set at approx 0-0.003" preload, so that the lifter cannot pump up & hold the valve open.
With all this creativity, you may ask how different is this from a solid roller. Truely there is very little difference at this point & some have even been known to use solid lifters on a hydraulic cam for his reason. Discuss this with your cam grinder if you want to go this way to ensure compatibility.
