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View Full Version : how to build a blowthrough carb for your turbo bike



turbonate
01-06-2011, 12:56 PM
had a few people ask me how i got mine to work right, so i figured why not just post a thread about it. i've been building turbo cars with blowthrough carbs for years and decided it was time to do a blowthrough bike. i've put almost 12000 miles on it and ridden it all over hell and creation with no issues other than getting some trash in the needle and seat outside of slidell la once.

the bike

turbonate
01-06-2011, 1:04 PM
i'll try to list everything in the right order as the pictures

the first thing you need is an electric fuel pump, i use a frame mount pump from an 89 f-150, they are available at any parts chain for about a bill. you can also see the fuel feed port i added to my tank in this picture.

you'll also need a good quailty return style boost referenced fuel pressure regulator, i use an aeromotive since i've had great success with them on my race cars

, i guess it goes without saying that you'll need a return port in your tank as well, i used the stock pickup location as a return port.

next you need to seal all the atmospheric vents on the carb and drill and tap it somewhere above the fuel level, i built a 4 into one manifold and used an old zenith i had.

turbonate
01-06-2011, 1:08 PM
this has nothing to do with the carb, but you are going to need an oil feed and return for the turbo. i drilled and tapped both camshaft oil pressure galleries in the head and tied them together and ran that to the pressure side of the turbo.

next i drilled and tapped the case above the oil level directly in front of the cam chain and fed the returned oil from the turbo into it.

turbonate
01-06-2011, 1:18 PM
now here is the key to the kingdom that makes this whole mess work right. i installed a pitot tube into the charge pipe with a flared end directly in front of the compressor outlet. now tie the hose from this into a y that feeds into the pressure port you put into the side of the carb, and the fitting on your boost referenced fuel pressure regulator. what this does is the flared tube creates a restriction in the intake path and the higher pressure generated is carried to the float bowl and fuel pressure regulator creating about a 1.3 to 1 float bowl to carb throat pressure differential causing a self enrichening condition under boost that will keep your pistons from having a thermonuclear malfunction. on my bike i'm making right at 10psi so i limited my total timing at 8 degrees shy of the stock max, it's been a couple of years since i set it all up, so i don't remember the exact numbers.

ibuiltmine
01-06-2011, 6:40 PM
you have a video fo this bike running? I like turbo stuff

turbonate
01-06-2011, 7:32 PM
you have a video fo this bike running? I like turbo stuff i sure don't,i don't even own a video camera.

Randeezy868
01-06-2011, 11:04 PM
Cool man thats a pretty sweet setup.

gmp
01-06-2011, 11:37 PM
awesome i have a few 14b's laying around and i have always wanted to do this to a sr500 nothing like hearing a turbo'd motorbike.

turbonate
01-07-2011, 8:30 AM
awesome i have a few 14b's laying around and i have always wanted to do this to a sr500 nothing like hearing a turbo'd motorbike.
except riding one :D

Randeezy868
01-08-2011, 12:13 PM
I think im following you with the carb mods. Are you using anything in the carb? Or just using it basically as a throttle body with fuel injection. I cant tell if your using the carb for idle fuel and using thefuel pump to boost fuel(sort of like an extra injector controller) or did you basically go full fuel injection with the fuel pump running fuel at idle and at boost. Also, any problem with crushing the floats in the carb. Ive heard boost will squash them and not allow them
To work properly. Ive done some turbo cars but nothing with a carb.

ibuiltmine
01-08-2011, 1:25 PM
except riding one :D

Im looking for a Yamaha Warrior. That is going to be my first turbo build.

Have you done any EFI turbo stuff?

turbonate
01-08-2011, 2:16 PM
I think im following you with the carb mods. Are you using anything in the carb? Or just using it basically as a throttle body with fuel injection. I cant tell if your using the carb for idle fuel and using thefuel pump to boost fuel(sort of like an extra injector controller) or did you basically go full fuel injection with the fuel pump running fuel at idle and at boost. Also, any problem with crushing the floats in the carb. Ive heard boost will squash them and not allow them
To work properly. Ive done some turbo cars but nothing with a carb.
i've got the carb working just like a normal one, all the circuits function normally. the pitot tube provides about a 1.3 to 1 float bowl to carb throat pressure ratio to cause the air fuel ratio to enrichen under boost, the fuel pump runs at all times, and the fuel pressure is set at 1 psi at idle so as to not overpower the needle and seat, the electric fuel pump simply provides a pressure increase under boost so that fuel will keep flowing in the the carb and not get blown back into the fuel tank. i'm running stock brass floats unfilled, i've not had any problems with them up to 10psi, but anymore than that and i'd find some carbs with nitrophyl (foam) floats. if you have anymore questions i'll be more than happy to help any way i can.

turbonate
01-08-2011, 2:19 PM
Im looking for a Yamaha Warrior. That is going to be my first turbo build.

Have you done any EFI turbo stuff?warrior bike or 4 wheeler?
i've built and programmed 3 megasquirts, but never on a bike. been playing with the idea of converting the kawi to fuel injection, but i don't really want to have to add an intercooler since i won't be getting the cooling effect that a blowthrough provides when the fuel atomizes.

ibuiltmine
01-08-2011, 7:07 PM
warrior bike or 4 wheeler?
i've built and programmed 3 megasquirts, but never on a bike. been playing with the idea of converting the kawi to fuel injection, but i don't really want to have to add an intercooler since i won't be getting the cooling effect that a blowthrough provides when the fuel atomizes.

Yeah, a bike.
When you do decide to convert to EFI, let me know. I have a complete 04 gsxr750 with a spun main. Id sell the entire wire harness/throttle bodies, computer, fuel pump, etc.....
I even have a power commander PCIII Brand new in the box

turbonate
01-10-2011, 8:41 AM
i was beating on my poor turbo bike this weekend in the shop and broke the chain, which slapped the clutch pushrod, which in turn broke the case. luckily i have a spare engine, and yes, i'm drunk in the picture.

SOKfab
01-11-2011, 12:02 PM
i just read the steps u posted, and they were extremely helpful, thanx i have some questions, but i dont have time now ill try to get back on tonight.

turbonate
01-11-2011, 2:52 PM
i'll be glad to help any way i can

SOKfab
01-11-2011, 4:56 PM
ok im a little confused on where to drill and tap the carb exactly?

turbonate
01-12-2011, 8:10 AM
you want to drill an tap it above the fuel level so the pressure picked up from the pitot tube will help force fuel into the carb throat. you might look into how the overflow vent is set up on yours, that will work just as well as long as you are sure to plug all the other atmospheric vents.

SOKfab
01-12-2011, 9:57 PM
Ok im gonna post a pic of my carb and just let me know where,
http://i442.photobucket.com/albums/qq148/SOCKinside/rebelcarb.jpg

turbonate
01-14-2011, 12:39 PM
i can't tell from the pic. you want to plug all atmospheric vents except the vent tube and plumb the hose from the pitot tube into it. it'll be the one that isn't the fuel feed.

royota
11-16-2011, 4:27 AM
i want to know what blowthrough carbs you are using thanx

swinewerx
11-16-2011, 9:48 AM
Wow!!! You lost me a long way back!!! You really know what you are doing!!!! I may modify the appearance of my rides, but as far as motor section, I leave them stock as much as possible!!!

turbonate
11-17-2011, 2:35 PM
i want to know what blowthrough carbs you are using thanx

i was using an old zenith from a sportster on that one. going with a megasquirt when i go back together with it.

kacivic
01-31-2012, 9:01 AM
very cool. as I have nothing else to do with the bike at the moment, I'm considering trying to turbo my KZ305, and will definitely have some questions for you.

riceburner
01-31-2012, 1:11 PM
For blow through applications a C.V. carb seems to be better because of the way the slide is operated, controlling fuel and helps to eliminate flat spots in throttle response.

HatchA74
01-31-2012, 2:11 PM
Nice!

Is that a low compression turbo you're using? I have three "bolt-on turbos" from Ford Sierra turbo diesel engines (American version was the Ford Merkur). Possible future projects/disasters :)

ibuiltmine
01-31-2012, 5:38 PM
Nice!

Is that a low compression turbo you're using? I have three "bolt-on turbos" from Ford Sierra turbo diesel engines (American version was the Ford Merkur). Possible future projects/disasters :)

Merkur's had a T3 on em. Decent turbo.

RDH
01-30-2013, 5:26 AM
I have a tx500 Yamaha. What do you think my odd are on turbo

RDH
01-30-2013, 5:29 AM
I have a tx500 I plan on twin turboing it with Tiny turbos I'm just like everyone else kinda confused on the whole carb mess with blow through. Anyway would it be better to convert it to a single carb or keep the doubles Thx

ibuiltmine
01-30-2013, 5:24 PM
I have a tx500 I plan on twin turboing it with Tiny turbos I'm just like everyone else kinda confused on the whole carb mess with blow through. Anyway would it be better to convert it to a single carb or keep the doubles Thx

tx500's are know for self-destructing on their own, let alone with boost.

riceburner
01-30-2013, 7:24 PM
The TX had chain driven chains inside the motor.

RDH
02-02-2013, 2:57 PM
Yea the chains are def a mess but she runs strong I'm pretty mechanically inclined and can for sure pull it off I just have never messed with boosted motorcycles. I'm gonna go for it any here in the next 6 months so any advise from anyone would be great and anyone with resent knowledge on tx500 can give me some pointers I've searched for some nice pistons for boost can't seem to fine any performance parts online Well it'll be happening ill post pics. And yes it's my bike in the pic

78833Maker
06-27-2013, 10:11 PM
What is the valve on your regulator?

Irish669
06-29-2013, 7:17 PM
Man this is just the thread ive been looking for. I want to turbo my 81cb750 so I have some power to push a sidecar. Any particular turbos you would recommend I seek out size brand etc? :clap for you:

turbonate
02-27-2014, 12:58 PM
I used a chiwaneese knock off of a gt15, it held up good for a long time, and spool time was about right. The valve at the regulator is my fuel shut off to the carb, works just like a petcock.

angelmrtz
11-08-2014, 10:13 PM
hey man do you think you can give me some advice, i want to turbo my 99 r6. the thumbnails on this post are no longer there

turbonate
01-26-2015, 8:18 PM
Sure, it sounds worse than it really is, just a few simple carb mods, a fuel pump, and a boost referenced fuel pressure regulator and you're good to go.

ibuiltmine
01-28-2015, 6:54 PM
i have everything setup on my KZ ready to go. Just need the time between work and class to build the manifolds. once you get your head around how it works, its really pretty simple!

Dpratt07
05-18-2015, 11:05 AM
Did you change the timing of the bike ? Im about to do this on my gs550 and i wasnt sure if i needed to retard my timing or anything.

Thanks
~Dave

ibuiltmine
05-18-2015, 6:32 PM
on my rebel I cut new holes int eh timing plate and put it as far foreward as I could then locked it down with no further advance.

datadavid
05-19-2015, 12:59 PM
I really need to get me a cheapo crappy bike to try this on now.. think my brothers got a few garrets lying in his shed somewhere..
There really isnt more to it?

KeysRyder
05-19-2015, 2:08 PM
Turbo is simple, if you can cut and weld an exhaust and an intake, thats all there is too it. I have built 3 turbo bikes over the years, first one being a blow through, other 2 were fuel injected.

datadavid
05-19-2015, 2:36 PM
Im still gonna blow up my first attempt though.
Welders are shitty mechanics! :D

ibuiltmine
05-19-2015, 4:02 PM
blow through carb was WAY easier then efi bike i did. just got to size all your stuff to the bike your doing. need a fuel pump thats low pressure and a regulator that will raise it 1:1. you can only go as much boost as your fuel pump will do pressure, so you really need a fuel pressure gauge. I got that, and a wide band O2 meter. once I had it tuned up, I took the wideband off the bike. the rebel was running 6lbs of boost. I never had it in a bike, but i hooked it up to a stock rear wheel and tire and would put the tire on a 2x4 to make resistance and a full throttle pull in 3rd gear was damn impressive to watch. I sold the whole setup to a guy with a rebel chopper, and never heard from him again.

Adelphos
03-20-2016, 10:20 PM
Hey could you help me to install a turbo to a 1941 indian scout engine?

cggorman
03-21-2016, 9:27 AM
I got that, and a wide band O2 meter. once I had it tuned up, I took the wideband off the bike.

What setup were you using for your wideband? I'm looking at putting together a portable wideband to help tune a couple carbed NA bikes in the stable.

Blakeslee
04-23-2016, 12:02 PM
Turbonate. I'm in the process of putting a turbo on an sr250 but I need help understanding what to do with carb set up. Everything is hooked up and conected turbo wise. Just didn't know if you had any extra advise to what you've already said being is the motor is so small.

FLASH1970
06-16-2016, 9:47 AM
Am I on the right track?

http://i209.photobucket.com/albums/bb184/flashgordon1970/DIAGRAM_zps26mdxtay.png (http://s209.photobucket.com/user/flashgordon1970/media/DIAGRAM_zps26mdxtay.png.html)

FLASH1970
06-16-2016, 10:28 AM
What setup were you using for your wideband? I'm looking at putting together a portable wideband to help tune a couple carbed NA bikes in the stable.

I've installed and used a couple Innovate LC-1's when tuning cars with a DB gauge (just has a number readout) and the XD16 gauge (number readout and various color LED's along the outer edge lit up based on what the AFR is). But for datalogging and tuning I was able to have it hooked up to a laptop on the passenger seat... Can't really do that on a bike. lol. I believe the LM-2 can log multiple channels (RPM,AFR...) and store the data. And the LM-1 can as well but you need add on harnesses. I have also been looking into the Zeitronix ZT-2 that can log 4 channels of data at once. But, you have to buy a thumb drive add on to save the datalogs for analyzing on a laptop. Hope this helps.

81HondaBobber
07-01-2017, 9:27 AM
When boosting the bikes did you have to change engine internals like how you do in cars? Also do you need all the gauges/regulates like in cars as well(boost pressure, fuel pressure, motor oil pressure, turbo oil pressure?

quadrazer
11-01-2017, 1:08 PM
Could you possibly PM me some photos of your carb modifications? For some reason, they won't open for me on here.