Welcome to the North American Subaru Impreza Owners Club Monday November 24, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Miscellaneous > Off-Topic

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 12-16-2007, 12:05 AM   #1
markman
Scooby Newbie
 
Member#: 93623
Join Date: Aug 2005
Location: What happens next
Vehicle:
will AMAZE you!

Default Blow through carb turbo question... any gurus here?

here's the deal-

I'm homebrew turbocharging a 1979 Fiesta. Carb will be boxed and modded to accept pressurized air. small turbo will be used (probably a T25 or similar), and 6-7psi will be max boost. Junkyard IC will be plumbed in.

FPR will be a Mallory 4309 or 4307 1:1 unit (haven't gotten it yet).

My question is: what is a good but cheap electric fuel pump I can use to replace the factory mechanical pump? Can I just plumb in a high pressure pump from a EFI car? I've got a fuel pump off an STi sitting in my basement- will that work? or is that more pressure than a carb-designated FPR can handle?

BTW this is just a for-fun project (and learning experience)

IBwhythehellareyouturbochargingafiesta?
* Registered users of the site do not see these ads.
markman is offline   Reply With Quote
Old 12-16-2007, 12:06 AM   #2
yarrgh
Scooby Specialist
 
Member#: 80465
Join Date: Jan 2005
Chapter/Region: RMIC
Location: Aurora, CO
Vehicle:
2001 2.5RS
Black Diamond Pearl

Default

she's gone from suck to blow!
yarrgh is offline   Reply With Quote
Old 12-16-2007, 12:08 AM   #3
hotshot172
Scooby Newbie
 
Member#: 85253
Join Date: Apr 2005
Location: Moore
Vehicle:
06 Beast Mode
I survived an F5

Default

I see no reason why the sti pump wouldnt work. Just be sure you wire it up correctly, and that you set the fuel pressure at the correct setting.
hotshot172 is offline   Reply With Quote
Old 12-16-2007, 12:31 AM   #4
Drink
Scooby Newbie
 
Member#: 102682
Join Date: Dec 2005
Location: Woodberry, IN
Vehicle:
... ripper's
sister.

Default

Any 255lph will work great for your application.

http://store.summitracing.com/partde...5&autoview=sku
Drink is offline   Reply With Quote
Old 12-16-2007, 12:36 AM   #5
markman
Scooby Newbie
 
Member#: 93623
Join Date: Aug 2005
Location: What happens next
Vehicle:
will AMAZE you!

Default

awesome, good to know.

now i gotta figure out how I'm gonna tap the engine's oil supply...
markman is offline   Reply With Quote
Old 12-16-2007, 12:39 AM   #6
Drink
Scooby Newbie
 
Member#: 102682
Join Date: Dec 2005
Location: Woodberry, IN
Vehicle:
... ripper's
sister.

Default

Just use braided stainless steel NPT oil lines.
Drink is offline   Reply With Quote
Old 12-16-2007, 12:41 AM   #7
hkerekes
Scooby Specialist
 
Member#: 66310
Join Date: Jul 2004
Chapter/Region: South East
Location: Removing passenger seat
Vehicle:
2012 Orange

Default

Quote:
Originally Posted by Mark03BlueREX View Post
awesome, good to know.

now i gotta figure out how I'm gonna tap the engine's oil supply...
Take the pan off and get it welded.

Which engine you working with?
hkerekes is offline   Reply With Quote
Old 12-16-2007, 12:42 AM   #8
Damn Yankee
Scooby Newbie
 
Member#: 53066
Join Date: Jan 2004
Chapter/Region: South East
Location: I guess a legend and an out of
Vehicle:
work bum look a lot
alike, daddy.

Default

why the hell are you turbocharging a fiesta?
Damn Yankee is offline   Reply With Quote
Old 12-16-2007, 12:45 AM   #9
markman
Scooby Newbie
 
Member#: 93623
Join Date: Aug 2005
Location: What happens next
Vehicle:
will AMAZE you!

Default



It's the 1600cc kent crossflow OHV engine, same as used in the old Formula Ford 1600 open-wheel racers.
http://www.wilcoxengines.demon.co.uk..._1600_kent.htm
markman is offline   Reply With Quote
Old 12-16-2007, 12:45 AM   #10
soldmyboxster
Scooby Specialist
 
Member#: 65520
Join Date: Jul 2004
Chapter/Region: International
Default

If you can get your hands on Corky Bell's book about turbocharging, Maximum Boost, it specifically discusses your issue in depth.

I used to own it and I think since the original carb used a low pressure pump, you need to stay with one, otherwise it could upset the needle or float or something.
soldmyboxster is offline   Reply With Quote
Old 12-16-2007, 12:46 AM   #11
Damn Yankee
Scooby Newbie
 
Member#: 53066
Join Date: Jan 2004
Chapter/Region: South East
Location: I guess a legend and an out of
Vehicle:
work bum look a lot
alike, daddy.

Default



reminds me of the old insanity test
Damn Yankee is offline   Reply With Quote
Old 12-16-2007, 12:49 AM   #12
markman
Scooby Newbie
 
Member#: 93623
Join Date: Aug 2005
Location: What happens next
Vehicle:
will AMAZE you!

Default

Quote:
Originally Posted by soldmyboxster View Post
If you can get your hands on Corky Bell's book about turbocharging, Maximum Boost, it specifically discusses your issue in depth.

I used to own it and I think since the original carb used a low pressure pump, you need to stay with one, otherwise it could upset the needle or float or something.
I think if the FPR does it's job the carb shouldn't see additional pressure unless it's under boost, regardless of the pump used. But yeah, the floats need to be replaced because the stockers will collapse from the pressurized air (or so I've read).

I gotta get that book.
markman is offline   Reply With Quote
Old 12-16-2007, 12:50 AM   #13
racer98
Scooby Newbie
 
Member#: 86793
Join Date: May 2005
Default

Quote:
Originally Posted by Mark03BlueREX View Post
here's the deal-

I'm homebrew turbocharging a 1979 Fiesta. Carb will be boxed and modded to accept pressurized air. small turbo will be used (probably a T25 or similar), and 6-7psi will be max boost. Junkyard IC will be plumbed in.

FPR will be a Mallory 4309 or 4307 1:1 unit (haven't gotten it yet).

My question is: what is a good but cheap electric fuel pump I can use to replace the factory mechanical pump? Can I just plumb in a high pressure pump from a EFI car? I've got a fuel pump off an STi sitting in my basement- will that work? or is that more pressure than a carb-designated FPR can handle?

BTW this is just a for-fun project (and learning experience)

IBwhythehellareyouturbochargingafiesta?
1981 Nissan 280zx Turbo External F/P set up is very nice one to use

also btw If you want to look at some Wacky Blow thru set ups look at the Lotus Turbo cars from the early 80s now that friggn shot my brain when I 2saw that set up.


its a bit extream in this case but make sure you have a Fire ext set up in the engine bay should something go wrong and you wont have to worry about any thing should something go wrong with the set up your running. Just a back up plan.
racer98 is offline   Reply With Quote
Old 12-16-2007, 12:58 AM   #14
hkerekes
Scooby Specialist
 
Member#: 66310
Join Date: Jul 2004
Chapter/Region: South East
Location: Removing passenger seat
Vehicle:
2012 Orange

Default

How did you box the carb?

Its difficult to do "right" because the throttle shaft on carbs isnt sealed.

The make specific blow through carbs where the throttle shaft is sealed.

Here is a link that might help ya. http://www.hangar18fabrication.com/blowthru.html

or http://www.dune-buggy.com/turbo/carbureted.htm
hkerekes is offline   Reply With Quote
Old 12-16-2007, 01:15 AM   #15
markman
Scooby Newbie
 
Member#: 93623
Join Date: Aug 2005
Location: What happens next
Vehicle:
will AMAZE you!

Default

Quote:
Originally Posted by O2wrx View Post
How did you box the carb?

Its difficult to do "right" because the throttle shaft on carbs isnt sealed.

The make specific blow through carbs where the throttle shaft is sealed.

Here is a link that might help ya. http://www.hangar18fabrication.com/blowthru.html

or http://www.dune-buggy.com/turbo/carbureted.htm
thanks for the info, i've been researching how to build the enclosure
markman is offline   Reply With Quote
Old 12-16-2007, 02:17 AM   #16
soldmyboxster
Scooby Specialist
 
Member#: 65520
Join Date: Jul 2004
Chapter/Region: International
Default

Whatever you do, don't half-ass it and make it a draw-through config. Blow-through is a much more effective design.

Fuel pumps for EFI are designed to deliver a certain amount of flow at a relatively high pressure (around 36 psi at 0 in/Hg of manifold vacuum). Carb pumps deliver similar volumes but are designed to work at very low pressure (couple or 3 psi).

I think using an EFI pump in a carb application might cause it to be grossly over-fueled, not to mention the carb probably wasn't designed for such pressure. Blown seals?
soldmyboxster is offline   Reply With Quote
Old 12-16-2007, 03:01 AM   #17
tspax2
Scooby Newbie
 
Member#: 44838
Join Date: Oct 2003
Chapter/Region: South East
Location: wilmington, nc
Vehicle:
2007 suby wrx
blue

Default

I live in Wilmington, NC . Want an aspire for parts ? Updated fiesta with FI. Yours for the taking.
tspax2 is offline   Reply With Quote
Old 12-16-2007, 03:23 AM   #18
nayeliesuncle
Scooby Newbie
 
Member#: 165137
Join Date: Nov 2007
Location: Caribbean
Default

Go to the forums at www.turbomustangs.com. The site has a carburated blow- thru and draw-thru section with a lot of information. The members are very friendly and will help you out.

Good luck.
nayeliesuncle is offline   Reply With Quote
Old 12-16-2007, 05:15 AM   #19
Fastbak390
Scooby Newbie
 
Member#: 64928
Join Date: Jun 2004
Vehicle:
1971 Turbo Pinto
1970 Ford Ranchero

Default

I don't hear of too many people turbocharging the 1600. However, as you've probably seen, there are a ton of fun parts you can get from across the pond.

Carburetors generally work at 4-6 psi. As stated previously, an EFI pump with an adjustable FPR would be complete overkill. I would recommend this pump:
Clicky

To tap the oil supply, use a T-fitting at the oil sender location on the side of the block and run steel braided line to the turbo. For a return, my 2.0 has a 5/8" hose fitting welded to it (make sure the fitting is sufficiently above the oil level in the pan). I just have rubber hose for the return.

Should you decide to take the easy way out and do a draw through setup like me (which will simplify carb tuning and eliminate the need for a wastegate or BOV), make sure you use a carbon-seal turbo instead of a dynamic seal. You'll have oil problems later if you don't.
Fastbak390 is offline   Reply With Quote
Old 12-16-2007, 06:00 PM   #20
markman
Scooby Newbie
 
Member#: 93623
Join Date: Aug 2005
Location: What happens next
Vehicle:
will AMAZE you!

Default

great info, thanks for the help.

tspax, i'm not sure there are too many interchangeable parts i could use!

fastbak- i'm definately wanting to do blow-through... if for no other reason than to learn how to do it.
markman is offline   Reply With Quote
Old 12-16-2007, 06:14 PM   #21
WindexLeggy
Scooby Newbie
 
Member#: 109266
Join Date: Mar 2006
Location: Canada
Vehicle:
1999 Jetta TDi

Default

Quote:
Originally Posted by Mark03BlueREX View Post
great info, thanks for the help.

tspax, i'm not sure there are too many interchangeable parts i could use!

fastbak- i'm definately wanting to do blow-through... if for no other reason than to learn how to do it.
Mark, kudos to you for wanting to mess around with this engine as a learning experience.

A little advice from a guy who grew up on carbs.

An FI fuel pump is (as described above) is designed to work at high pressure and high flow, a carb pump is designed to workl at low pressure with flow matched to the carb in question.

If you put a MFI pump on a carb car, the pressure it creates is going to overpower the needle and seat's ability to seal, and you will flood the carb. What you need is a hi-flow pump designed for carbed applications - like from holley, walbro etc.

The poster above about the throttle plate is incorrect - throttle plate shafts sit in bushings with a very tight tolerance - unless the shaft/bore is excessively worn, you should be ok. you do want to make sure that the seal to the top of the carb is good.

Like an FI suby, once you have more air, you're going to need more fuel to match. You will need to get this from opening up the jet(s) in your carb. Start small, then work your way up- don't over-do it, as you can never go smaller again if the car just wont idle.

Also, to do it right, you really should lower the compression ratio by getting a thicker head gasket, or by dremeling the pistons, otherwise you will have to retard the timing and lose power.

Another option is to leave everything alone (aside from the blower), and incrementally raise the boost until it starts to lose power at high load - this is an indication you are running short of fuel (even with a high flow pump - remember, the main jet(s) meter the fuel - not the pump), then back off slightly. An EGT would be a good idea if you are trying for any kind of longevity...

All in all, sounds like fun. wish I had the time to do something similar.
WindexLeggy is offline   Reply With Quote
Old 12-24-2007, 11:09 PM   #22
markman
Scooby Newbie
 
Member#: 93623
Join Date: Aug 2005
Location: What happens next
Vehicle:
will AMAZE you!

Default

Question for carb smart people:

From researching I've found that i need solid or foam filled floats for my carb in order to prevent collapse under boost pressure. Problem: all i can find for my carb are OEM style hollow brass floats. I've heard you can fill brass floats with foam, but have not found any information detailing this.

My Question: How the crap do I fill these with foam? A friend of mine said to drill a tiny hole in them and fill them with that 'Great Stuff' foam, but this sounds ridiculous (but it might actually work).

Any ideas???
markman is offline   Reply With Quote
Old 12-24-2007, 11:32 PM   #23
jakeachy
*** Banned ***
 
Member#: 162893
Join Date: Oct 2007
Chapter/Region: MWSOC
Location: Jargin-off
Vehicle:
00 STM GC8

Default

OP-
Ive got a 255lph Holley electric external for dirt cheap.
jakeachy is offline   Reply With Quote
Old 12-25-2007, 01:58 AM   #24
markman
Scooby Newbie
 
Member#: 93623
Join Date: Aug 2005
Location: What happens next
Vehicle:
will AMAZE you!

Default

Quote:
Originally Posted by jakeachy View Post
OP-
Ive got a 255lph Holley electric external for dirt cheap.
thanks but after doing some more research I think that would be way too much pressure. I'll probably go with one designed for carb applications like the one FastBack390 recommended.
markman is offline   Reply With Quote
Old 12-25-2007, 02:09 AM   #25
bobturismo
Scooby Specialist
 
Member#: 42145
Join Date: Aug 2003
Location: cruizin' down the street in my
Vehicle:
6-4 jockin da bish-
es and slappin the hoes.

Default

I suggest you use a return line with a pressure regulator.

6-7 psi, the carb probably isn't gonna need a box like someone said.

I would use a chevy fuel pump designed for a TBI motor, they can be had for cheap and you can find one that will be in the range you are looking for.
bobturismo is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Blow through MAF questions vtchris Newbies & FAQs 0 10-06-2006 10:38 AM
Blow Through MAF Questions R0DENT Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo) 6 09-06-2006 06:02 PM
Perrin Blow through MAF turbo kit kams#3 Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo) 3 03-19-2006 11:57 PM
any good welders in the va-norfolk, suffolk, va beach. need blow through maf welded moorebl Mid Atlantic Impreza Club -- MAIC 6 03-07-2006 12:16 AM
blowing oil through a turbo? milkman Normally Aspirated with bolt-on Forced Induction Powertrain 20 06-25-2002 07:29 PM


All times are GMT -4. The time now is 02:52 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.