383 H/C/I Results!!
03-23-2017, 12:39 AM
#341
TECH Veteran
Seen a LS7 SS camaro (Ryan) run 9.9s-10.0s on 28" tire at the LS fest... but okay guess it can be did with either size tire.
03-23-2017, 06:47 AM
#342
I don't disagree, but if the plenum volume can't keep up, it's drawing air from a vacuum. Sorta like a higher DA. In this case, I'm not saying that the engine will be limiting cylinder fill. I'm saying that the intake won't be able to fill itself as fast as the engine draws it down. Sorta like filling a bucket at 2-gpm while there's a 3-gpm hole in the bottom
Edit - put more simply, the longer stroke won't fill the intake any faster
I honestly think this is the best decision. Larger plenum, shorter runners = less likely to hold the engine back.
Edit - put more simply, the longer stroke won't fill the intake any faster
I honestly think this is the best decision. Larger plenum, shorter runners = less likely to hold the engine back.
03-23-2017, 08:00 AM
#343
10 Second Club
6000 rpm is 6000 rpm but on a longer stroke engine the Pistons are moving faster at that rpm, increasing air speed, and choking out an intake earlier than a short stroke engine would
03-23-2017, 08:06 AM
#344
TECH Veteran
Before you guys beat up on the fast intake... it's been 9.3s in the quarter at over 140 mph in naturally aspirated form on pump gas (ported 92mm) in a F body application. Car weighed over 3000 lbs also. And that was back in the day.
03-23-2017, 08:12 AM
#345
If FAST won't do the short-runner for the Cathedral port, I wonder if someone like Tony Mamo who does a lot of work on this stuff anyway, couldn't get a set of runners fabbed up to fit into the manifold? Or modify the LSXRT runners?
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
03-23-2017, 08:45 AM
#346
I would like to see a log of the car showing MAP dropping dramatically during a pull, until then I'm not convinced that it is choking out unless hes revving high. I'm not arguing it would pick up power with a larger intake, I'm arguing scavenging is not an issue with the larger headers and lower overlap than Phoenix had.
03-23-2017, 09:29 AM
#347
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If FAST won't do the short-runner for the Cathedral port, I wonder if someone like Tony Mamo who does a lot of work on this stuff anyway, couldn't get a set of runners fabbed up to fit into the manifold? Or modify the LSXRT runners?
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
03-23-2017, 10:44 AM
#349
If FAST won't do the short-runner for the Cathedral port, I wonder if someone like Tony Mamo who does a lot of work on this stuff anyway, couldn't get a set of runners fabbed up to fit into the manifold? Or modify the LSXRT runners?
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
03-23-2017, 10:56 AM
#350
If FAST won't do the short-runner for the Cathedral port, I wonder if someone like Tony Mamo who does a lot of work on this stuff anyway, couldn't get a set of runners fabbed up to fit into the manifold? Or modify the LSXRT runners?
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
03-23-2017, 11:20 AM
#351
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03-23-2017, 11:44 AM
#352
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The 2" headers would be nice. I just don't like the fitment issues that come. Cutting up the K-member. The 1 7/8 should do ok. For now lol.
Darth. The intake swap you did, between the fast & msd, was really cool to see. Honestly I still liked the fast better. Made more tq/hp everywhere up to about 6200-6400? The msd is better high rpm.
I've been keeping an eye on the manifold vacuum on wot runs. Between say 4000-6100 rpm the vacuum is between .6 & .9 inches. Once it gets over that, 6400-7000, it gets up to just over 1.1" with flashes of 1.4". Right where the msd would do good to keep it at or under 1" at those rpm I bet.
Also I want to keep a Wilson intake on the car.
Darth. The intake swap you did, between the fast & msd, was really cool to see. Honestly I still liked the fast better. Made more tq/hp everywhere up to about 6200-6400? The msd is better high rpm.
I've been keeping an eye on the manifold vacuum on wot runs. Between say 4000-6100 rpm the vacuum is between .6 & .9 inches. Once it gets over that, 6400-7000, it gets up to just over 1.1" with flashes of 1.4". Right where the msd would do good to keep it at or under 1" at those rpm I bet.
Also I want to keep a Wilson intake on the car.
The thing is, when you look at the LS7 version of the MSD, it gains EVERYWHERE over the fast. I'm convinced that the shorter runners favor the longer stroke. And also, you can't use the 346 data to determine what's best for a 383. That's how people get a 383 that acts like a truck engine. They need more cam and intake to support that swept volume. Also, since the stroke is longer, the accelerative forces are higher. Without giving too much away, I deal with this in our manufacturing process. I have a machine that is limited by acceleration, so I have to design stroke and frequency within that parameter. With the longer stroke, you reach higher accelerative forces - i.e. internal resistance - at lower angular frequency. This causes the engine to peak earlier and fall off faster. Unless you have the modifications to make enough more HP to support more RPM. Like later IVC and shorter runners. Maybe Wilson can design you an intake
/soapbox
Are you familiar with Phoenix dyno thread? We aren't arguing about filling the intake any faster. RPM is RPM, meaning all the timing is the same regardless of whether its a 5.3 or a 427, 6000rpms still equals 100 rotations per second. But each of those rotations has the ability to draw in more air due to the longer stroke. Phoenix' issue was his exhaust port on his heads and long tubes compared to the intake port and valve overlap was overscavenging the combustion chamber and sucking fresh air right out of the chamber. That is not what is going on here.
The definition of overscavenging is drawing more air into the cylinder than the intake can draw in through the throttle. Once the intake is starting to pull a vacuum at WOT, power WILL fall off, because your g/cyl starts to decline even faster due to lower pressure differential between plenum and cylinder. SoFLa not getting much of a WOT vacuum, but when he moves to larger headers, and that cylinder fill jumpstarts better, don't be surprised if the WOT vacuum gets worse. The ONLY cure for that is a larger plenum. This is why the ITB arrangement is so good for power. The entire atmosphere IS the plenum.
03-23-2017, 01:17 PM
#353
Originally Posted by JakeFusion
If FAST won't do the short-runner for the Cathedral port, I wonder if someone like Tony Mamo who does a lot of work on this stuff anyway, couldn't get a set of runners fabbed up to fit into the manifold? Or modify the LSXRT runners?
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
Honestly, I don't know why someone hasn't come along and done that given the modular nature of the FAST. We could have multiple sets available... given the 3D printing capabilities, they could be done fairly cheap and with polymer. Or if you had a CNC machine, could cut them out of 6061 or something and fit them.
03-23-2017, 05:13 PM
#354
In all due respect I disagree. I have my reasons of corse. Look at the guys running 10s on motor or faster with T56 tranmissions . They all are running a stiff wall 28" slick.... Maybe the weaker/slower cars on in the shorter tire. I damn near got every issue of gmhtp. If you have them... Look at the 10 sec cars featured and see what size slick they running 
03-23-2017, 11:53 PM
#356
TECH Veteran
Look at the 10 second club section.... hell its a full weight SS camaro just reaped 136 mph trapping with a 10.0 pass on 28' Hoosiers with 4.10 gears
Last edited by Tuskyz28; 03-24-2017 at 06:04 AM.
03-24-2017, 03:33 AM
#357
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Remember seeing this sometime back and hoped that FAST would make a shorter runner for the other LSX heads: Ls7 and Ls2 style heads guy said the hell with it and did his own.
http://www.corvetteforum.com/forums/...2-runners.html
Pictures no longer show up. 1st 4 pictures from goggle images are from the same thread.
https://www.google.com/search?q=Maki...w=1013&bih=582
http://www.corvetteforum.com/forums/...2-runners.html
Pictures no longer show up. 1st 4 pictures from goggle images are from the same thread.
https://www.google.com/search?q=Maki...w=1013&bih=582
03-24-2017, 06:44 AM
#358
Got a STL file? I've got access to a decent 3D printer. To do an entire intake would require it being in multiple pieces, but a running should be able to be done in 1 shot.
Agreed, we're not talking about the same thing. I was explicitly talking about the difference between OP's setup and Phoenix in that Phoenix's setup was overscavenging, which my definition of is that there is a lower area of pressure in the exhaust vs. the CC and there is enough overlap, that the fresh air mixture that entered the chamber on the intake stroke was moved directly into the exhaust instead of staying in the CC.
My TA couldn't hook to save its life on a 26" tall tire at 600+rwhp, went to a 28" tire and went mid 10's lol.
Yes I am, but that is only part of what I'm trying to say. And if we're not arguing about filling the intake faster, we're not talking about the same thing, because that's exactly what I'm talking about. I would argue that my heads have extremely high flowing exhaust ports (possibly more so than his), I still run 11 degrees overlap AFTER the motor has warmed up (17 cold), 1-7/8 headers, and a 3" dual with X pipe.
The definition of overscavenging is drawing more air into the cylinder than the intake can draw in through the throttle. Once the intake is starting to pull a vacuum at WOT, power WILL fall off, because your g/cyl starts to decline even faster due to lower pressure differential between plenum and cylinder. SoFLa not getting much of a WOT vacuum, but when he moves to larger headers, and that cylinder fill jumpstarts better, don't be surprised if the WOT vacuum gets worse. The ONLY cure for that is a larger plenum. This is why the ITB arrangement is so good for power. The entire atmosphere IS the plenum.
The definition of overscavenging is drawing more air into the cylinder than the intake can draw in through the throttle. Once the intake is starting to pull a vacuum at WOT, power WILL fall off, because your g/cyl starts to decline even faster due to lower pressure differential between plenum and cylinder. SoFLa not getting much of a WOT vacuum, but when he moves to larger headers, and that cylinder fill jumpstarts better, don't be surprised if the WOT vacuum gets worse. The ONLY cure for that is a larger plenum. This is why the ITB arrangement is so good for power. The entire atmosphere IS the plenum.
I was explicitly talking about the difference between OP's setup and Phoenix in that Phoenix's setup was overscavenging, which my definition of is that there is a lower area of pressure in the exhaust vs. the CC and there is enough overlap, that the fresh air mixture that entered the chamber on the intake stroke was moved directly into the exhaust instead of staying in the CC. My TA couldn't hook to save its life on a 26" tall tire at 600+rwhp, went to a 28" tire and went mid 10's lol.
03-24-2017, 07:22 AM
#359
TECH Veteran
Spider- I'm not surprised at all. 600 rwhp is alot 