Draw-Thru ( Turbocharging your carbed accord )

[lostforawhile]

where did all the SU stuff come from? i'm waiting on my long awaited book how to build and power tune SU carbs, so there should be info to add to this thread, took me two years to finally get my hands on one. as far as the SU's,why aren't they being run blow through? they are easy to pressurize,since the fuel bowl is external. they respond to the amount of air going through the carb, the more air,the higher the needle lifts,and the more fuel. they would seem to solve the problem of making all the power valves work right,and secondaries work right,etc. there is a lot of knowledge out there on running them under boost too. with something like one of the small eaton supercharger units,that is belt driven, and the new msd boxes that control ignition in proportion to boost,it seems like it would be a pretty easy setup. was i seeing things,or was there a bunch of jerry springer stuff deleted out of this thread just now?

[lostforawhile]

does anyone know what kind of horsepower those rhinos make? they actually have a supercharger for one, hmmmm. picture.

[lostforawhile]

here's an excellent article on superchargers great read for anyone http://www.502motorsports.com/PerformanceParts4.html

[Hauntd ca3]

where did all the SU stuff come from? i'm waiting on my long awaited book how to build and power tune SU carbs, so there should be info to add to this thread, took me two years to finally get my hands on one. as far as the SU's,why aren't they being run blow through? they are easy to pressurize,since the fuel bowl is external. they respond to the amount of air going through the carb, the more air,the higher the needle lifts,and the more fuel. they would seem to solve the problem of making all the power valves work right,and secondaries work right,etc. there is a lot of knowledge out there on running them under boost too. with something like one of the small eaton supercharger units,that is belt driven, and the new msd boxes that control ignition in proportion to boost,it seems like it would be a pretty easy setup. was i seeing things,or was there a bunch of jerry springer stuff deleted out of this thread just now?

you'd have to pressurise the float bowl aswell as the dash pot to make an su work as a blowthru set up.
ts a fairly fine balance to make them work spot on at the best of times.
the needles look like a straight taper but are far from it in reality.
they can be barrel shaped,hour glass shaped or anywhere in between.
the springs in the dash pot vary in strength and the amount and grade of oil in the dash pot can change the speed the needle moves in the jet.
the jet size itself.
i reacon that su's are prob a harder carb to tune than a weber even tho they are quite poss the simplest carb in the world to rebuild at home.
they prob run better than a weber once tuned aswell
its hard to explain how an su works without writing a novel eh.
rjudgey being a pom should have su experiance, i know i was rebuilding them for fun at age 12. a slotted screw driver and a 6 inch cresent are all you need to field strip them.

[colinnicholson86]

you'd have to pressurise the float bowl aswell as the dash pot to make an su work as a blowthru set up.
ts a fairly fine balance to make them work spot on at the best of times.
the needles look like a straight taper but are far from it in reality.
they can be barrel shaped,hour glass shaped or anywhere in between.
the springs in the dash pot vary in strength and the amount and grade of oil in the dash pot can change the speed the needle moves in the jet.
the jet size itself.
i reacon that su's are prob a harder carb to tune than a weber even tho they are quite poss the simplest carb in the world to rebuild at home.
they prob run better than a weber once tuned aswell
its hard to explain how an su works without writing a novel eh.
rjudgey being a pom should have su experiance, i know i was rebuilding them for fun at age 12. a slotted screw driver and a 6 inch cresent are all you need to field strip them.

X2.
The boost psi / fuel psi relation would have to be very accurate. Some form of rising rate regulator would have to be used, a Malpassi MIGHT work.
One of the issues I had was that too high fuel pressure would result in fuel leakage through the jet at low to mid throttle, and too low pressure would result in lean conditions at mid to high throttle.

As far a blowthrough goes with an SU. I'm not sure what would happen when you were at full throttle in boost and you closed the throttle - Would the jet close, or remain open due to the pressure acting on the needle? which could mean that the throttle would be WOT with no way of stopping it.

[Hauntd ca3]

As far a blowthrough goes with an SU. I'm not sure what would happen when you were at full throttle in boost and you closed the throttle - Would the jet close, or remain open due to the pressure acting on the needle? which could mean that the throttle would be WOT with no way of stopping it.

worst nightmare, a runaway motor
would want a kill switch handy eh
which part of nz you at colinnicholson86

[lostforawhile]

worst nightmare, a runaway motor
would want a kill switch handy eh
which part of nz you at colinnicholson86

thats a good question, all the boosted setups i've seen have had the output of the supercharger connected directly to the carbs. it's done all the time on mini's this way. my book i've been waiting on forever should be here this week. this one is supposed to be the bible of SU performance. been trying to get my hands on one for a couple of years,now it's on the way here. oh and my SU tool set got here yesterday, the original 1970's era one. looks brand new still. probably never used. i was going to rebuild these myself,but the cost of the rebuild kit, is just a little bit less then the cost to have them done,besides these need throttle shaft bushings, and i don't have the special reamer to ream them oversize. i can't justify the 100 dollars for it eithier.

[lostforawhile]

um these do have throttle plates lol. as far as venting the domes the dome vents are the extra holes in the air intake side of the air cleaner flange. those are the air passasges that go back to the top. the fuel bowl is a good question though. i would think the more air went through the carb,the more fuel would be pulled out of the jet. but i see the issue. the needle is supposed to be tapered on these, i've seen it changed into all kinds of wierd configurations before, but on these it's supposed to be a taper.

[Hauntd ca3]

tru on the throttle plate bit.not thinkin
on the float bowl bit, if you are blowing thru them, you'd have boost pressure at the jet which would try and push air into the float bowl, and boost at the aircleaner side and the throttle side, and since from memory an su takes a vacum from the engine side of the throttle to the top of the dash pot and atmo presure from the aircleaner side of the dash pot, you'd have to try and replicate this somehow otherwise the dash pot wont lift and airflow wil be restricted and the needle wont come outta the jet.
i've never seen a blo thru su set up b4, only draw thru, maybe because of this

[Rendon LX-i]

A little off topic but i love how the 4g63 manifolds bolt right up to a f22 on a 93 accord and you can basicly use the gst stock set up lol...Im a dummy when it comes to carbs i know little bout chevys thats bout it. Its confusing how a carb works when it comes to forced induction. But anyways lol

[cubert]

does anyone know what kind of horsepower those rhinos make? they actually have a supercharger for one, hmmmm. picture.

Do you mean Rhino as in a Yamaha Rhino?


Ive driven a supercharged one, and they go pretty decent. The one i drove was tuned poorly though

[lostforawhile]

Do you mean Rhino as in a Yamaha Rhino?


Ive driven a supercharged one, and they go pretty decent. The one i drove was tuned poorly though

i was just wondering about the supercharger

[89T]

If you want to do a blow through turbo setup, take notes from those toyota corolla guys running their 1970's round backs with turbocharged 3TC engines.

Yeah, there isn't too much information regarding blow-through weber turbo systems on the internet. I was lucky enough to hook up with a guy in Hawaii that built some fast corolla's. At the time he had a corolla that broke into the 9's with a blow through setup. He was running 30+ lbs of boost through a set of 45 DCOE's.

There is no real trick with boosting a weber setup except for these few key components:

1. Make sure to pressurize the fuel bowl of the carburator. This will ensure that fuel will still flow out of the jets into the intake runner and not the otherway around.

2. Be sure to use plastic floats. Those old brass floats will crush under boost and will take on fuel eventually flooding the carb/engine.

3. You must use a rising rate fuel regulator. It sounds odd to run more than 4 psi of fuel pressure through the carbs but it is needed to compensate for boost pressure.

You don't need to build a box around the entire weber carburator to pressurize the float bowl. You pressurize the float bowl via the vent hole on the backside of the carb.

Or if you use the stock carbs, there's the vent tube that connects between the carbs. Could just tap into there....

here is some info i found on P.P.

[colinnicholson86]

um these do have throttle plates lol. as far as venting the domes the dome vents are the extra holes in the air intake side of the air cleaner flange. those are the air passasges that go back to the top. the fuel bowl is a good question though. i would think the more air went through the carb,the more fuel would be pulled out of the jet. but i see the issue. the needle is supposed to be tapered on these, i've seen it changed into all kinds of wierd configurations before, but on these it's supposed to be a taper.

That was the main problem - SU's have piston/needle for fuel and plate for air.
A piston carb has no way of forcing the piston to close. If you tip an SU upside down the piston can open w/o the throttle rotor moving.
This means that when you suddenly close the throttle, The engine will still have a vacuum acting on the piston and fuel which won't necessarily force it to close, meaning that fuel could still be sucked in (without air, potentially causing fuel pooling)
For a blowthrough setup you have to remember the fuel being pulled through the jet relies on airflow AND vaccum to pull it through, not just airflow as such. E.g You have massive airflow at 10psi but you have to remember that there is now 10psi pushing back on the fuel jet, so you would need over 10psi fro ANY fuel to flow into the carb.

BTW - What was your original SN name and also Rendon LX-i's?
As you probabally know I havn't been on this forum for a while since I found CB7Tuner.

worst nightmare, a runaway motor
would want a kill switch handy eh
which part of nz you at colinnicholson86

I'm originally from Wellsford, but living in Auckland now.

A little off topic but i love how the 4g63 manifolds bolt right up to a f22 on a 93 accord and you can basicly use the gst stock set up lol...Im a dummy when it comes to carbs i know little bout chevys thats bout it. Its confusing how a carb works when it comes to forced induction. But anyways lol

I take it you've visted CB7Tuner before? That setup is more commonly know as the DSM setup. Its what I have on my CB Accord.

[A18A]

wow someone from north of auckland :O thats a first. sorry for the off topic

[colinnicholson86]

wow someone from north of auckland :O thats a first. sorry for the off topic

Damn another NZ'er, I really have been away for a while haha

[AccordB20A]

and another

[Rendon LX-i]

That was the main problem - SU's have piston/needle for fuel and plate for air.
A piston carb has no way of forcing the piston to close. If you tip an SU upside down the piston can open w/o the throttle rotor moving.
This means that when you suddenly close the throttle, The engine will still have a vacuum acting on the piston and fuel which won't necessarily force it to close, meaning that fuel could still be sucked in (without air, potentially causing fuel pooling)
For a blowthrough setup you have to remember the fuel being pulled through the jet relies on airflow AND vaccum to pull it through, not just airflow as such. E.g You have massive airflow at 10psi but you have to remember that there is now 10psi pushing back on the fuel jet, so you would need over 10psi fro ANY fuel to flow into the carb.

BTW - What was your original SN name and also Rendon LX-i's?
As you probabally know I havn't been on this forum for a while since I found CB7Tuner.




I'm originally from Wellsford, but living in Auckland now.



I take it you've visted CB7Tuner before? That setup is more commonly know as the DSM setup. Its what I have on my CB Accord.

AHhh i know cb7tuner.com well but i also boosted a 4gen with a stock gst setup...i tryed it on a 5gens but had to drill out the holes...But My original name is Joshua but im just josh lol...known as Rendon since its my last name lol....I like your setup also...May i ask why Carbs?

[colinnicholson86]

AHhh i know cb7tuner.com well but i also boosted a 4gen with a stock gst setup...i tryed it on a 5gens but had to drill out the holes...But My original name is Joshua but im just josh lol...known as Rendon since its my last name lol....I like your setup also...May i ask why Carbs?

Joshua, now I remember, Maybe you know me too http://www.cb7tuner.com/vbb/showthread.php?t=62581
I went carb simply because I had an addiction to carbs haha, That and I wanted to step out side the box.
Plus I can't deny the experience I got from it all.

[Rendon LX-i]

Good to know. I had a buddy boosted a civic that was carbed. was a pain lol...Oh yeah i remember. Didnt know that was you. Very nice bro. mad props

[colinnicholson86]

Good to know. I had a buddy boosted a civic that was carbed. was a pain lol...Oh yeah i remember. Didnt know that was you. Very nice bro. mad props

Haha carbs will always be a pain, But if done right they can be great.
Thanks Man