short runner VS> long runners(Who's right
06-19-2002, 10:17 AM
#21
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Thanks Turbo that is exactly what I plan to do but just wondered if anyone had tried some of these at home and if so were there any gains. Motor already has good exhaust system and air cleaner with adjustable fuel regulator. ASM reprogramed ECU when exhaust was added. Had roller rockers installed a while back as the stock pivot ball rockers were showing signs of HIGH temperatures. Mainly just freshening up the heads as it pulled an intake manifold gasket in and started using oil big time. Also had some valve sealing issues so we pulled the heads. Glad we did the head gaskets were going to go next.
06-19-2002, 10:44 AM
#23
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I built one of these engines w/ 625+ tq and 530+hp and it's still in service w/over 400 hours of hard runn'n!...and he didn't even follow my instructions on service and runn'n the damn thing!
06-19-2002, 11:22 AM
#24
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Some interesting information here. What's actually going on in the runners that makes length important anyway?
I remember from many different sources that long runners are for boosting torque at low RPM, but I dimly recall a few other things:
- plenum volume also involved, there's a plenum "boost" too
- a long column of air is harder to start moving, so no good at high RPM when you have little time
- acoustics has something to do with it
When the valve slams shut a pressure wave travels back up the runner to the plenum or atmosphere, and part of this pressure reflects back down the runner. At a given RPM, the runner length will be such that the reflected wave arrives at the valve just as it is opening for the next intake event. This is how headers work too? Resonance is what some people call it; same thing that makes a pipe organ work.
Lingenfelter did the development work for Mercury. At the same time he developed his own "stealth" manifold. Think of the Mercury manifold but increase the volume of the plenum and extend the runners inside the plenum with extra tubing and a bellmouth inlet for each runner. This manifold made 600 ftlbs of torque with peanut port heads at a ridiculously low RPM. High RPM HP was limited. I think you can still buy it from Accel.
I remember from many different sources that long runners are for boosting torque at low RPM, but I dimly recall a few other things:
- plenum volume also involved, there's a plenum "boost" too
- a long column of air is harder to start moving, so no good at high RPM when you have little time
- acoustics has something to do with it
When the valve slams shut a pressure wave travels back up the runner to the plenum or atmosphere, and part of this pressure reflects back down the runner. At a given RPM, the runner length will be such that the reflected wave arrives at the valve just as it is opening for the next intake event. This is how headers work too? Resonance is what some people call it; same thing that makes a pipe organ work.
Lingenfelter did the development work for Mercury. At the same time he developed his own "stealth" manifold. Think of the Mercury manifold but increase the volume of the plenum and extend the runners inside the plenum with extra tubing and a bellmouth inlet for each runner. This manifold made 600 ftlbs of torque with peanut port heads at a ridiculously low RPM. High RPM HP was limited. I think you can still buy it from Accel.
06-19-2002, 11:50 AM
#25
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Turbo I hear you man. Programmable is why I am hesitant to make to much change.
Audacity any particulars on the motor would be appriciated. Was this a full mod as for upgrade to 2.25" intakes, cam change ect.
Tomcat I wish I had a dyno in my garage to play with! A lot of variables come in to play and I think the 502 is a pretty good package but we always want more.
Audacity any particulars on the motor would be appriciated. Was this a full mod as for upgrade to 2.25" intakes, cam change ect.
Tomcat I wish I had a dyno in my garage to play with! A lot of variables come in to play and I think the 502 is a pretty good package but we always want more.
06-19-2002, 12:13 PM
#26
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basically...very loose with that word!!LOL...runner length should be based on the speed of sound and as you all know that air will move from the hi pressure zone to the low...the more inertia it has (air is compressible) the more you cram/ram into the cylinder, hence the tunnel ram. so yes tomcat, you are on the right track for a carb engine...some of the rules change for EFI's only because there are different variables now...
i'm not really to sure about how i feel about telling people "how to" build up that engine...i designed and built a throttle body...i'll thell ya there is nothing in that unless you relly get out of hand and make 600+hp and hi rpms...i like to clip mine @5500..i'll tell you cam timing is VERY important to this engine (as with all) as will as the idle seq....i wanted a big cam hi hp engine to idle at 710-730 exactly ALL the time...it took a TON of dial in work, but it can be done. i'll tell ya if you think you will see something with a upgrade in flame arestor,,,just take yours off and look for a change...i've yet to see a EFI backfire a flame out the TB. personally there is more to gain (hp speaking) by taking off the EFI....have fun!
i'm not really to sure about how i feel about telling people "how to" build up that engine...i designed and built a throttle body...i'll thell ya there is nothing in that unless you relly get out of hand and make 600+hp and hi rpms...i like to clip mine @5500..i'll tell you cam timing is VERY important to this engine (as with all) as will as the idle seq....i wanted a big cam hi hp engine to idle at 710-730 exactly ALL the time...it took a TON of dial in work, but it can be done. i'll tell ya if you think you will see something with a upgrade in flame arestor,,,just take yours off and look for a change...i've yet to see a EFI backfire a flame out the TB. personally there is more to gain (hp speaking) by taking off the EFI....have fun!
06-19-2002, 01:17 PM
#27
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Thanks Audacity and I hear you load and clear but had to ask. You pretty much answered my question as to what it would take $ wise and time. Not looking to build that kind of HP just looking for some gains and keep the EFI while it is apart. If I want to go BIG HP I will go carb as I can tune those myself and cam selection to get it to idle is not as touchy as with EFI. I can probably get what information I need from printed articles. Thanks again.
