3800 injector question
- Thread starter Xtant12
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I was talking to a GEAR HEAD today at work and he was telling me somethig about shift points.. He was asking me about my mods and he was interested in getting a GP.. He told me for all my stuff I should be able to move my shift points to like 7000 rpm's.. I told him he was crazy and he somehow mistaked my car for a honda... 
well, he then said seriously that he thought we could do that with our cars.. I told him I would liik into it but I dont think it would be a good idea..
It is my understanding that the higher the shift points the more power you lose.. Help me out here guys.. who is right...
well, he then said seriously that he thought we could do that with our cars.. I told him I would liik into it but I dont think it would be a good idea.. It is my understanding that the higher the shift points the more power you lose.. Help me out here guys.. who is right...
Originally posted by Xtant12@Jul 21 2006, 08:22 PM
I was talking to a GEAR HEAD today at work and he was telling me somethig about shift points.. He was asking me about my mods and he was interested in getting a GP.. He told me for all my stuff I should be able to move my shift points to like 7000 rpm's.. I told him he was crazy and he somehow mistaked my car for a honda...
It is my understanding that the higher the shift points the more power you lose.. Help me out here guys.. who is right...
[snapback]133001[/snapback]
With no aftermarket cam, and on stock internals (springs, cam, etc.) a 7,000rpm shift point would likely grenade our OHV motor. Unfortunately we arent a LS1 or the like..
edited: and yes even if we could get away with spinning to 7k, we would lose power because of our low-end torque design due to the cam specs, and anemic heads.
Originally posted by SaturdaysGS+Jul 21 2006, 07:36 PM-->@Jul 21 2006, 08:22 PM
I was talking to a GEAR HEAD today at work and he was telling me somethig about shift points.. He was asking me about my mods and he was interested in getting a GP.. He told me for all my stuff I should be able to move my shift points to like 7000 rpm's.. I told him he was crazy and he somehow mistaked my car for a honda...
It is my understanding that the higher the shift points the more power you lose.. Help me out here guys.. who is right...
[snapback]133001[/snapback]
With no aftermarket cam, and on stock internals (springs, cam, etc.) a 7,000rpm shift point would likely grenade our OHV motor. Unfortunately we arent a LS1 or the like..
edited: and yes even if we could get away with spinning to 7k, we would lose power because of our low-end torque design due to the cam specs, and anemic heads.
[snapback]133008[/snapback][/b]
so wait a min... are you saying with a Hot Cam ( or any other Cam ) it is possible to get that high.. How high can you get..
Originally posted by Xtant12+Jul 23 2006, 10:06 PM-->@Jul 21 2006, 08:22 PM
I was talking to a GEAR HEAD today at work and he was telling me somethig about shift points.. He was asking me about my mods and he was interested in getting a GP.. He told me for all my stuff I should be able to move my shift points to like 7000 rpm's.. I told him he was crazy and he somehow mistaked my car for a honda...
It is my understanding that the higher the shift points the more power you lose.. Help me out here guys.. who is right...
[snapback]133001[/snapback]
With no aftermarket cam, and on stock internals (springs, cam, etc.) a 7,000rpm shift point would likely grenade our OHV motor. Unfortunately we arent a LS1 or the like..
edited: and yes even if we could get away with spinning to 7k, we would lose power because of our low-end torque design due to the cam specs, and anemic heads.
[snapback]133008[/snapback]
so wait a min... are you saying with a Hot Cam ( or any other Cam ) it is possible to get that high.. How high can you get..
[snapback]133133[/snapback][/b]
with a XP or XPZ cam it's "possible" to shift that high but you really don't make any additional power after 6400/6600rpm (depending on exact setup) the only reason to set shift points that high is if that will drop you back down into your peak powerband once you shift.
very few cams will make power over 6700 RPM. Not only do our poorly flowing intake ports not support it, bleed down from the lifters starts to really screw things up at that RPM. Comps help, but have issues for a daily driven car.
In addition, (on an oddly relevant note) the increase in RPM decreases injector headroom. The faster you rev, the more often the injectors fire, and accordingly, the less time they have to fire, so they become static sooner. A car that may be perfectly fine on 42s and 6200 shifts, might be static at 6600, requiring a bigger injector. It's just not feasable.
MT
In addition, (on an oddly relevant note) the increase in RPM decreases injector headroom. The faster you rev, the more often the injectors fire, and accordingly, the less time they have to fire, so they become static sooner. A car that may be perfectly fine on 42s and 6200 shifts, might be static at 6600, requiring a bigger injector. It's just not feasable.
MT
You wont make 10 more PSI in the last 800 RPMs, but you can still boost more with more RPMs. Thats just the blower spinning that much faster or the turbo spooling that much more.
Plus whats the average for boost now adays for the people that want to run that high of RPMs?? 14?? 15?? Hell, turbo peeps will run 18 at the track.
Plus whats the average for boost now adays for the people that want to run that high of RPMs?? 14?? 15?? Hell, turbo peeps will run 18 at the track.
"I dont think anyone has extra head bolts drilled into their motor. Thats the reason even cometics still fail. " i beg to differ, check out zzp
and boost pressure is not going to raise from rpms being raised. it will just get hotter as J/o said once you hit a certain psi the BC or wastegate will stop it right there.(mbcs creep but thats not much)
and boost is in the mid 20s not teens at that RPM.
and boost pressure is not going to raise from rpms being raised. it will just get hotter as J/o said once you hit a certain psi the BC or wastegate will stop it right there.(mbcs creep but thats not much)
and boost is in the mid 20s not teens at that RPM.
Not true...
Mike K and I had this discussion years ago, but the reason boost climbs as the RPMs climb is that their respective efficiency curves. The blower is flowing more air at high RPM than the air is, and this is true moreso at high RPM, and this is why cars who drop exhausts often experience very constant boost rather than a ramping effect....but that's ancillary to the real point.
Boost pressure and its effects are NOT the same at any RPM. 10lbs of boost at 7000 RPM is going to be MUCH more stressful on all parts than the same pressure at 6000 RPM, even if charge temperatures are identical. The reason is impulse. While you may have the same pressure putting the same amount of fluid (A/F mixture) into the cylinder, you are compressing it MUCH faster. You end up with the same volume compressed the same amount, BUT the time over which this force is applied is considerably smaller, which increases the impulse due to pressure on the entire pressure vessel (combustion chamber/piston) as a whole. The result is an increase in head gasket failures. If we had gaskets and mating surfaces that could withstand these forces, it would probably end up chipping pistons, even without the effects of knock.
As far as bolting, Zooom has added 2 small bolts and had good luck with it, and John Tsimaras has gone to fatter head studs and was also somewhat successful. I'm really most interested to see how ZZP's new aluminum heads do with these sealing issues. I'd think with Aluminum's yield characteristics, or rather lack thereof, a billet head could reeeeeally help in this struggle against sealing issues.
MT
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