Theexploited1

iTrader: (6)

hey guys doin a 13b swap into my fb, since i wrecked my fc and was wondering if anyone had experience with sleeveless 6port 13b dellorto 48 stock port setups, so i can get an idea on what jetting i should use for best power and best eco, i dont have the funds for a wide band at the moment...

thanks,
sidney

diabolical1

iTrader: (3)

I used to run a similar setup. you can use this thread for a rough guide, but ultimately, your engine may have different needs.

https://www.rx7club.com/1st-generati...lation-398921/

Theexploited1

iTrader: (6)

sweet thanks man and yeah i know what you mean every engine and carb is different haha its worth a try to see if anyone did the exact same thing haha

Theexploited1

iTrader: (6)

oh and for fine tuning might you know the afm i should be running? i might beable to pick up a wideband kit in the next 2 weeks

Starfox07

AFM? I don't understand why you want an AFM with a carb. Use this site, it is awesome:

Gruntled.com - Dellorto Intake System

Also, my thread might be of use:

https://www.rx7club.com/1st-generati...-power-975331/

Says weber, but I got a Dellorto instead, as you will see if you read it. Carbs are a lot of work, but very rewarding when you get them tuned right. Just don't rely on it to be your daily driver, because it will be ill-suited with a carb.

diabolical1

iTrader: (3)

while it still doesn't explain the wideband he's planning to get, my guess is it's a typo and he meant AFR.

... just one of the reasons i'm not crazy about using abbreviations.

in all honesty, while i'm definitely a fuel injection advocate and don't really have much use for carbies these days, my experiences were just the opposite. I found my 12As and even my 13B with the Dell'Orto (after I finally got over my fears of it) great for daily driving. dead reliable, easy to troubleshoot and definitely a blast to drive.

Starfox07

Perhaps, but they also get pretty poor fuel mileage. I haven't got mine fine-tuned to perfection yet, but it pulls way, way harder than stock. It's a straight up beast above 6,000rpm.

ioTus

iTrader: (5)

I'm about 2 weeks away from an EFI swap, ditching the Dell 48 on my s5 block, however its running HELLA smooth right now.

My only gripe really is the fuel economy - *****!! like 12-18
. However on a massively streetport engine i guess that isnt too bad...

~Geoff

diabolical1

iTrader: (3)

I used to get roughly 24 mpg from mine (stock ports though). I tried real hard to see if I could get it on the other side of 25, but no go.

Theexploited1

iTrader: (6)

yeah it was a typo and thanks guys just got my 13b just about stripped and out of my fc love how easy it is to remove these engines hahaha and im going to go for a mpg tune after i get everything set and ready cause im taking a long journey to the west coast then its guna be set again down there for power so i cant wait till i get everything ready to go!

ioTus

iTrader: (5)

Whoa - out of a 48??

diabolical1

iTrader: (3)

yep. RB 48 DHLA.

Theexploited1

iTrader: (6)

lol while we are here any advise on exhaust? im thinking 2.5" straight into a magnaflo straight through 2.5" to 4" muffler you guys know what i mean the tips 4" and i have a rb header. and im planning on doing side exhaust out the passenger side before the rear tire. leme know this is a budget build so rb full exhaust is a nogo (already have the muffler)

Starfox07

I would suggest 2 mufflers. Mine has a dynatec split flow muffler (very compact, but effective) right after the header and then a large racing beat universal muffler at the end, with a 4.5" (IIRC) dump tip. It sounds very good, especially at high RPM. The racing beat universals sound way better than the power pulse, are way cheaper, look better, and have amazing build quality. With the header, I spent maybe $600 on my exhaust, total.


I took this video when my throttle linkage was preventing full throttle so that's why it looks so slow. But it gives you an idea on the sound.

Be careful about routing any exhaust under the passenger side, it could get pretty hot! However, from what I've seen, the shorter the exhaust system is, the better it sounds, so maybe try it out!

Theexploited1

iTrader: (6)

that does sound good haha

EDIT: why 2 mufflers?

Theexploited1

iTrader: (6)

whats better for performance out the back or out the side before the rear tire? and backfires are a + hahaha but performance is key

Starfox07

I don't think it will make much, if any difference on the length. It's important to have two mufflers because the one just after the header absorbs a lot of the high frequency 'noise.' Without reducing this, you get a very 'pingy' sounding exhaust, from what I've seen. It takes a beating though, so it needs to be tough. The dynatech has all stainless steel packing material, so it's a bit better than fiberglass, though I think even it has burned all up now. The second muffler (the big RB unit) gives the exhaust a nicer tone and absorbs a lot of the sound energy, so it's much quieter.

Theexploited1

iTrader: (6)

ahhh i see hmmm... alrighty i guess ill have to go with that setup haha

EDIT: oh and haha love the other video you have at the end you tap your light and it turns on hahahah epic!!!

Theexploited1

iTrader: (6)

3" or 2.5"?

Starfox07

Mine is 2.25" I believe. Anything larger is overkill for a stockport engine and you lose velocity, which reduces scavenging. This is what I've read at least.

j9fd3s

iTrader: (3)

a 2.5 straight thru should flow more than enough, and be quieter than a 3"

ioTus

iTrader: (5)

Well since we're all throwing in opinions on exhaust I might as well drop this one in.

Robert and Hyperformance2k have both found, with dyno tested results, that the most power they were able to get (by a significant margain actually) is through a 2.5" collected header, which flares to 3" header-back. As many mufflers as you want for sound deadening (at least 2 if you're a reasonable, sane person who's afraid of noise or sudden movements).

This will be how my next exhaust configuration is (2.5" collected to 3" header back). I plan on putting 2 mufflers and a cat on.

The flare technique is often used with heavy equipment and diesel engines, where they go from 3" to 5" or such.

I'm not enough of a geek to throw numbers around, but here's my armchair mechanic take on the sitch:

For clarification the flow characteristic of the collector and flare do make a substantial difference. the collector should be very long (i believe its at least half-again as long as the RB collector). I'm no exhaust guru but I have studied a bit on pressure wave dynamics, primarily for speaker and subwoofer design.

Abrupt edges near fast-moving sound pressure waves creates "chuffing" (as its called in the speaker world) which is where a spot of low pressure immediately around the edge interacts with the high pressure wave moving past it. this slows down parts of the flow and this speed change produces the chuffing noise. a flare directs the sound in a smooth and consistant path, evenly transitioning from one pressure to another. With the pressure change also comes temperature and speed change. This is why you'll see subwoofer ports flared. Ideally they'd be flared at both ends. Called "air horns" on carbs. You'll also notice these flares called "velocity stacks" and put on air intakes for the same or similar reasons.

j9fd3s

iTrader: (3)

i kind of agree, armchair mechanic. i also agree that the fewer transitions you have the better.

the header theory gets complex, but its very simple just to make sure you've got no sudden diameter changes

Theexploited1

iTrader: (6)

ok so what you guys are saying is take my rb header do a 1' in length collector into a 2.5" diameter then do a megaphone style flair to 3" then do my muffler then my other muffler then a flair to a 4" dump? or should i just do a 3" dump?

EDIT: so i will need 2 3" in 3" out straight through mufflers and a megaphone from rb or jegs or where ever and since thats guna put me passed where i wanted to dump (before the passenger rear tire) should i still do the dreaded axle bend since its going into a 1st gen? if so i should also put my 2nd muffler at the back to weld the dump onto right?

EDIT#2: is there any way to get passed the stupid over axle bend? i dont like them............

DriveFast7

iTrader: (1)

Either go under the axle or out the side before the rear tire. Each have their own issues.