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-   -   dynoed the fb, big letdown (https://www.rx7club.com/1st-generation-specific-1979-1985-18/dynoed-fb-big-letdown-539276/)

rxguru 05-12-06 11:53 AM

You should study the voltage drop off on your dyno chart. Stock ignition drops off bad over 6000. Do some direct fire action. Its cheap and will probably give you slightly better numbers. A lot of fuel/air mix is cool, but you gotta have some way to burn it!

Hyper4mance2k 05-12-06 01:46 PM

PJ you're wrong I did 140rwhp with a carb and no sleves. People need to stop parrotring bad info.

Siraniko 05-12-06 01:49 PM

what size venturies are you using


Originally Posted by rotary_sex
so i have an 83 gsl, 13b 6 port swap
mods

stock port 175+k
gsl-se fueltank, pump, lines
weber 48dco carb (60f9 idle jets, 175 primaries, 160 air bleeds)
holley regulator
rb collected header and presilencer, 2.25 custom presilencer back with magnaflow
s4 lower intake manifold
no port sleeves

car made 123.8 hp ande 117.3 tq

must say im not happy with those numbers but theres room for improvement


trochoid 05-12-06 02:20 PM

The stock aux port sleeves will help a little, not much, the Pineapple ones will give better laminar flow into the housing. It looks to me that the torque drops off a little too quick. Most of the dyno sheets I've seen, the torque curve stays pretty flat once peak is reached, then a quick drop when air flow is maxed.

The 64 to 6? GTOs had a 3 duece setup for carbs, Really sweet and made better power than the 4 barrel, better fuel economy too if you stayed out of the secondary pair. An origininal setup is high dollar. Then there is the 440 GTX 6 Pack. I pulled up next to one in the early 70's in my Road Runner. I reved to 5k and couldn't even hear my car over his idle, he had a very scary car that had been built with a huge cam.

fcdrifter13 05-12-06 03:25 PM

My only experience with a 6 pack is on an old ladies car. Her son went into the army and removed 2 of the carbs so she could handle it or something like that. She had regular tune ups at the garage I worked at. It came in one day done a PM, and didnt notice that her son got back and put the other two carbs back on. Lets just say when I mashed down on it to cross the street to get to customer parking it was the ride o my life.

peejay 05-12-06 04:51 PM


Originally Posted by Hyper4mance2k
PJ you're wrong I did 140rwhp with a carb and no sleves. People need to stop parrotring bad info.

Somehow I have grave doubts, unless there's something you're not telling.

Did you ever take it to the track? MPH vs. weight is the best power indicator, chassis dynos are really none too accurate.

iceblue 05-12-06 04:59 PM


Originally Posted by Hyper4mance2k
PJ you're wrong I did 140rwhp with a carb and no sleves. People need to stop parrotring bad info.

Yes you do, runing no sleeves is pointless crap and screws the air velocity VE all up. Go study some. Oh yea and the port timing is now hog wash. With a carb the port timing design of that motor is void anyhow.

purple82 05-12-06 05:01 PM


Originally Posted by peejay
Disappointed? That's really good for an essentially stock engine. Using a carb is hurting you a bit, and having no sleeves is *definitely* hurting you.

Why would not having sleeves hurt top end performance? They'd be open at full throttle anyway. If anything, removing sleeves has increased the size of the port and improved high rpm flow.

purple82 05-12-06 05:09 PM

[QUOTE=trochoid] the Pineapple ones will give better laminar flow into the housing. QUOTE]

You don't really know what "laminar flow" means, do you?

iceblue 05-12-06 05:26 PM

It does not increase the port removing them, it makes them more like a bottle design instead of a steady flow rate despite the 90deg radius.

trochoid 05-12-06 05:36 PM

[QUOTE=purple82]

Originally Posted by trochoid
the Pineapple ones will give better laminar flow into the housing. QUOTE]

You don't really know what "laminar flow" means, do you?

Actually I do know what laminar flow is and had I not changed majors in college so many times, you would be calling be Dr. or Professor trochoid. :rlaugh: I have studied fluid dynamics, and gases are concidered fluids.

At the end of the aux ports is a 90* turn, that's like running into a brick wall, backing up, then deciding to turn right or left, at the same time backing up all of the traffic behind you. Not very efficient for air flow.

jgrewe 05-12-06 05:45 PM

I would see what size chokes are in that carb. Smaller than 38mm and they would really be choking the engine at the top end. With the size jets you have, if its getting enough fuel at the bottom end, I'll bet you have small chokes. It would be real drivable on the street though, give me more power over a wide range down low over a dyno queen(just a high HP number somewhere up top) anyday.

You should be able to see the size by looking into the carb at the venturis. There will be little numbers cast in the top near the edge.

purple82 05-12-06 05:49 PM


Originally Posted by trochoid
Actually I do know what laminar flow is and had I not changed majors in college so many times, you would be calling be Dr. or Professor trochoid. :rlaugh: I have studied fluid dynamics, and gases are concidered fluids.

At the end of the aux ports is a 90* turn, that's like running into a brick wall, backing up, then deciding to turn right or left, at the same time backing up all of the traffic behind you. Not very efficient for air flow.

If that's true then you'd know that the bulk flow into the port is laminar or turbulent based mainly on it's speed.

You'd also know that the outside corner of a flow bend is where the slowest flow is occuring, counter to solid body motion, and that adding a wedge to that outer corner does next to nothing for airflow impedance.

purple82 05-12-06 05:52 PM


Originally Posted by iceblue
It does not increase the port removing them, it makes them more like a bottle design instead of a steady flow rate despite the 90deg radius.

I'm not sure what you're trying to describe. The sleeves are straight and when you pull them out, the remaining port is straight.

iceblue 05-12-06 05:59 PM

When you pull them out it creates an over hang so something like [ ]. I really whish I had a scanner right now. To explain my thoughts on the sleeves themselves. I am sure you understand purple how the wedge can lower the VE and increase the velocity. But this is only if the area radius of the sleeve is still greater or up to -20% of the area from the selves to the opening circumference.

Like I said I need a paper to make a diagram.

Kentetsu 05-12-06 06:20 PM

Wow, this is cool! :) To think that such a simple question turned into such an educational and entertaining thread!

Oh yeah, and I'm watching the spelling too guys.

Trochoid; you mispelled considered! Shame on you!

:jump:

trochoid 05-12-06 06:37 PM


Originally Posted by purple82
If that's true then you'd know that the bulk flow into the port is laminar or turbulent based mainly on it's speed.

You'd also know that the outside corner of a flow bend is where the slowest flow is occuring, counter to solid body motion, and that adding a wedge to that outer corner does next to nothing for airflow impedance.

If the aux port was a smooth raduis bend on both sides, then the cross sectional area of higher velocity flow would increase in size. With the 90* bend, the turbulence at the 'L' reduces clean flow on that side of the cross sectional area.

In a round, straight pipe, if one draws a line through the center, and a standard bell curve underneath it, that will show the relationship of velocity to that part of the pipe. When a bend is intoduced into the flow, the top of the bell curve, higher velocity, the bell curve becomes skewed to the the outside or longer side of the bend.

Solids and liqiuds, in dynamic applications, have the same flow characteristics, except that gases are compressible. Since we are dealing with a gas here, the 'L' corner will cause more turbulence and interference with flow than a liquid would because the liquid will not 'push back' like a gas will and acts as a solid, somewhat smoothing the 'L' into a curve, negating the turbulence conciderations.

Keep in mind that intake gases work under vacuum and not pressure and some of the dynamics are variant.

trochoid 05-12-06 06:43 PM


Originally Posted by Kentetsu
Wow, this is cool! :) To think that such a simple question turned into such an educational and entertaining thread!

Oh yeah, and I'm watching the spelling too guys.

Trochoid; you mispelled considered! Shame on you!

:jump:

I Googled concidered and apparantly I have been mis-spelling it for years. LOL :dunce:

Kentetsu 05-12-06 06:45 PM

Man, this is awesome. But nobody will ever find this incredible debate due to the fact that it is buried in the depths of a very commonly titled thread. :( A wealth of information lost forever.

This discussion is surely worthy of its own thread. I have to go to bed now due to weird working hours and my drunken state, but I will be checking back in on you guys later tonight.

Oh, and Trochoid; it's "gasses". :) Tsk, Tsk...

Kentetsu 05-12-06 06:46 PM

lmao! we were typing @ the same time...

trochoid 05-12-06 06:55 PM

My spelling is usually pretty decent, my typing sucks, where the hell is the spell check. You are just what I need, a proof reader.

rotary_sex 05-12-06 07:32 PM

well my 123 WHEEL hp is a huge increase over the gsl-se's stock 135 to the FLYWHEEL. so i wouldnt say having a carb is hurting me at all. im going to order some pineapple sleeves and pin them open for a smoother flow into the 6 ports, also am going to look into some second gen direct fire.

since that dyno run ive upped my air corrector jets to 220 so im running 175 primaries and 220 correctors, i have also advanced my timing 5 degrees over stock, it seems a bit peppier. we will see how it really goes after i install the DF and the pineapple sleeves.

trochoid 05-12-06 07:36 PM

When you get the sleeves, epoxy them in place so they won't rotate, unless you plan on having the work like stock.

krew 05-12-06 07:42 PM

If you had a wide band O2, it may help things.
My 12a BP sucked with a carb, went to EFI & a lot more fuel, I'm up at 204 rwhp.
So I think Fuel.

purple82 05-12-06 09:51 PM

2 Attachment(s)
Everyone can argue all they want, but it's hard to win an arguement against physics.

Here's a CFD simulation that I just ran. Notice that the high speed and low pressure is on the inside of the bend. The high pressure and low speed is at the outside. Suprised? Like I said, it's counter-intuitive until you understand what's going on within the fluid.


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