The Only 3300 lb. Buick V6 in the 8s using...
- Thread starter Alky V6
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Why do you think it's a wide range? I will argue that it is multiple finite points.
Here is a simple example you can put your numbers into to find the multiple resonant frequencies. Input you manifold air temp in degrees C, then your runner length in meters. Resonances of open air columns
This leaves out the pressure waves created by the compressor wheel and valve events, but if your plenum volume is large enough the pressure waves from the turbo are negligible. The valve events need to coincide with the pressure wave to take advantage of this resonance. The valve is open for the high pressure spike and closes for the lower pressure spike.
If your inlet temps are ~110F and you have an 8" runner the resonant frequencies happen in multiples of 780 rpm. If you lengthen the runner, you get resonant frequencies happening more often. This doesn't account for pressure, but if pressure is constant this basic equation is still correct, but the output values would be different. Are you varying pressure with rpm to take change the resonant frequencies with rpm?
edit: you posted before I finished.
Here is a simple example you can put your numbers into to find the multiple resonant frequencies. Input you manifold air temp in degrees C, then your runner length in meters. Resonances of open air columns
This leaves out the pressure waves created by the compressor wheel and valve events, but if your plenum volume is large enough the pressure waves from the turbo are negligible. The valve events need to coincide with the pressure wave to take advantage of this resonance. The valve is open for the high pressure spike and closes for the lower pressure spike.
If your inlet temps are ~110F and you have an 8" runner the resonant frequencies happen in multiples of 780 rpm. If you lengthen the runner, you get resonant frequencies happening more often. This doesn't account for pressure, but if pressure is constant this basic equation is still correct, but the output values would be different. Are you varying pressure with rpm to take change the resonant frequencies with rpm?
edit: you posted before I finished.
Considering that I can shift at any rpm from 6700 to 7800 with no ET change, it might surprise you where I tuned the configuration to.
Haven't spent any time around pro stock team so I don't know for sure. I do know a comp eliminator racer that uses a similar though process. They don't bother searching for power with resonant frequencies becuase the gains are so small. There are easier more cost effecient ways to find power.
I like this post. Good info.
My intake is tuned to have the pressure waves peak every 1,000 rpm or so. With the plenum volume I'm using, I actually did what I thought was by best to try and tune out any pulse tuning on the intake side, hoping for a broader useable torque curve.
True, but in the middle of each peak there is an equal and opposite low point that should have a negative effect on pressure. If your peak pressure happen every 1000 rpm then you get one a 7000 rpm. At 6500 and 7500 you get the negative of that pressure wave. And a neutral point at 6750 and 7250. So your rpm range would need to be less than half of 1000 rpm and centered around a peak. 500 rpm between gear changes with a 3 speed isn't happening with a converter effecient enough to actually put the power to the tire.
I'll give you a clue. Anytime you see long tube headers, there is an attempt at pulse tuning going on. Anytime you see a new feature in collector design, there is an attempt to advance the effects of pulse tuning happening. Do you think long tube headers are just for that bitchin exhaust sound?
Yes, they have to pick something for header length so they look at rough number for peak power. Have you ever seen a pro stock racer or comp eliminator guy change header length trying to tune in more power. Probably not, there are easier ways to find power.
True about the negative section of the wave. Fortunately, that doesn't translate into the same sort of losses in the cylinder. Could have something to do with the timing of the exhaust pulse in relation to the intake pulse as rpm climbs through the range.
You will actually see tunable headers more on road course cars that have to deal with different track configurations, such as long straightaways versus tight cornering. Even what sort of cornering.
Dusty Bradford
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- May 24, 2001
I don't know much about the T76 combo but I don't remember it producing impressive numbers.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
Again. Apples and Oranges.
#1. Not boosted
#2. They use a 5 speed manual transmission and keep the rpm in a very narrow rpm range.
If you want to prove your set-up is seeing all these gains from this pulse tuning, put a GT-45-76mm on it and see if it goes 8.30's.
5.73 in the 1/8.
28 psi boost.
Same small valve heads.
Same small displacement.
Outdated turbo.
Wrong manifolding.
Wrong cam.
Wrong TC.
Ebp to Ibp ratio: 1.5-1.6:1. More back pressure.
Like I already stated, the less back pressure is helping, but it's not the complete answer in my case.
1) What does boosted or not boosted have to do with it?
2) Why do they choose to narrow the operating rpm band? We're still talking 1/4 mile run, right?
3) You have a turbo I can borrow?
Simple. The amount of boost I'm using to be able to do what I'm doing.
Who else with a 3300 lb. car with a 224 cid V6, with 1.83/1.5 valves can say they can do 6.80s in the 1/8 mile with only 8 psi boost?
Well, not the ones in the Southern Cal area. And I know you've tuned some of them. On top of that, they're all more motor and head than mine, with more properly sized turbos, too.Everyone who has one. You really have impressed the heck out of yourself this time
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