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Possible upgrade in the future?

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Gary Lewis

Re: Possible upgrade in the future?

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Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

85lebaront2

Re: Possible upgrade in the future?

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In reply to this post by Gary Lewis

The reason for a downstream from the collectors or manifolds crossover (H or X) is the unbalanced pressure pulses, the same thing that gives you the V8 "rumble". On an inline 6, or even a V6, you do not need it nor really want it, same for a flat plane crank V8. On these the pulses are evenly spaced and it is actually detrimental.

I wish I could find the formulas Chrysler used in the 60s to calculate the runner length for intake ram tuning. I uses the same concept of pressure waves, but uses the pressure pulse generated when the intake closes to create a new pulse when it reverses at the end of the intake "tube" to arrive at the intake valve just as it opens. Newer engines with variable length intakes use this to help at low end, and again at higher rpms to produce more power efficiently.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Pebcak

Re: Possible upgrade in the future?

So is this going to be Common Core Math to figure this out? If it is then I'm not going to be any help.

Honestly, I really appreciate all the input. I would have never dreamed that this much can go into exhaust on a vehicle.

I've learned a lot this week so I'll see what I can come up with for a rough draft of what I might get.

On Feb 16, 2018 8:32 AM, "85lebaront2 [via Bullnose Enthusiasts]" <[hidden email]> wrote:

The reason for a downstream from the collectors or manifolds crossover (H or X) is the unbalanced pressure pulses, the same thing that gives you the V8 "rumble". On an inline 6, or even a V6, you do not need it nor really want it, same for a flat plane crank V8. On these the pulses are evenly spaced and it is actually detrimental.

I wish I could find the formulas Chrysler used in the 60s to calculate the runner length for intake ram tuning. I uses the same concept of pressure waves, but uses the pressure pulse generated when the intake closes to create a new pulse when it reverses at the end of the intake "tube" to arrive at the intake valve just as it opens. Newer engines with variable length intakes use this to help at low end, and again at higher rpms to produce more power efficiently.
"Getting old is inevitable, growing up is optional"
Darth Vader 1986 F-350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator
Wife's 2011 Flex Limited
Daily Driver 1994 Taurus LX
Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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NAML

1986 F150 XLT Lariat, 4X2, 351W, 1406 Edelbrock Carb - Currently going through an engine rebuild through a "Father/Son Project"

ArdWrknTrk

Re: Possible upgrade in the future?

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In reply to this post by 85lebaront2

CFD modeling has come a *long* way from slide rules in the 1960's...
(Yes, the A12/SR51 was designed in that era)

There are so many different factors that influence the outcome I would wonder if we could get an *absolute* answer -even today.

Plus manufacturing ability is always making new things possible.
(Find a few YouTube videos of Nissin CNC tube benders)

Wrt exhaust systems there a few basic principles.
But even then one needs to account for combustion temperature, pressure when the valve opens, mass and heat coefficient of the material, whatever.

Yeah it will make your head swim.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

ArdWrknTrk

Re: Possible upgrade in the future?

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In reply to this post by Pebcak

I'm sorry, I didn't directly address this.

No. You don't have to do crazy mental gymnastics to get an exhaust system that suits your needs.

This is not like the threads that start "I NEED a really lopey idle, but want a fuel efficient torque monster... and I want to do it for $150 with bolt on components"

My advice is to keep the runner/head pipe volume down and use as large a volume muffler and tailpipe as you like.

If you want a sound that is low and throaty go with a big muffler and tailpipe.
If you want something that 'barks' then smaller volume and free flowing design.

With a 351 -at 'normal' truck engine rpms- 1.75 head pipes and a 2.5 collector are verging on too big for best torque. (IMO)
But if the engine is not stock, and you drive it like you stole it, you would be fine and might want more.

Headers are always good... except for longevity, and serviceability.
Not being able to change a spark plug or starter with the pipes on the engine is hugely frustrating.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.