Blow-through carbs on a turbo engine...I want some info
 

Does anybody have any experience with blow-through carbs and turbos? I would like to hear the pros and cons of running this system. I assume price would be a pro, and being able to easily change between gas and methanol by changing jets, another pro.

MazdaRacing does this on their turbo 1st gens. I think it is a very bad idea and won't cost anyl ess than standalone injection unless you are staring w/ a carb you can modify for blow-though. The advent of fuel injection in the '80s is THE reason turbos became prevalent in production cars-carbs just didn't hack it; then or now.

I was looking for specific reasons as to why I should not do it. Ive heard from plenty of people that I shouldnt do it, but nobody can really tell me why.

On a side note, the chance of me doing this is very slim, Im just looking for info.

I listed two specific reasons. 1- cost. You would have to buy the manifolds and carbs; no cheaper than buying standalone injection to use w/ your stock injection system. 2.-precision of A/F ratio. Fuel injection allowed for this and it is important to maintain precise ratios not only for emmisions (why standard production cars got them -performance cars had it since 50s) but also it allowed for tubos (also developed in WWII) in production cars because turbos need precise fueling to work well at all.

I know. Ask those 1st gen guys at Mazdaracing if they would rather be running Haltec or something if it cost the same (as it would for a car w/ injection already). Is it easier to change jets or load a new fuel map?:p

Well, this isnt for my FC, its actually for my FB, but I assumed there would be more people here who would be willing to answer my question.

Thanks for your input, and I did see your reasons in your first post. It was more of a warning for all the people who just say its bad, and give nothing to support it. That really pisses me off.

Blow through
 

Presently im running a similar setup-cartech to be exact. Pushing around 300 horespower with 3rd gen ported motor.

I believe if i had a haltech w/ 3rd gen intake i could push over 400 horses @ 15 lbs of boost.

The car is running 10 lbs now

And my posts had another hint in them.:) Check Mazdaracing website: they specialize in 1st gen turbos w/ blow-through carbies. I bet they can help you out w/ any questions better than us 2nd genny boys.

what is mazda racing web addrerss?

thanks BlueTII

here is some pics of my blow through

http://www.imagestation.com/album/?id=4292204243

Looks nice. Clean set-up, perfect for a period correct "restored" car or for the die hard "old schooler".
You mention 10 psi on that set-up, but 15 on Haltec. Is 10 psi because of some limit on the blow-through system?

we have pushed 340rwh in my friends rx2 with a blowthrough setup.
holley 650dp
t60
deltagate
race port
9.4 rotors
rb manifold
msd everything
running 15 lbs of boost

the biggest pain is having to adjust the jetting. in the desert temps can vary sometimes about 30 degrees from morning to night. it worked so easy that we are installing his e6k this weekend.

probly do some more adjusting with fuel. going back on dyno to monitor mixture @ 6-8000 rpm

maybe ad another se fuel pump to keep volume up

the car is making more torque than horsepower.

You can run up to 20 or more psi w carbs The problem is with jettig and fine tunening

I know all about that. I'm running FCD and boost over fuel cut so I do same crap. Add walbro, monitor A/F-add pump rewire, monitor A/F. I've taken my car 1 step closer to carbie by lying to ECU about boost and I don't like it:rolleyes:

fuel
 

would running a apexi computer or haltech help fine tune and cut down the use of so much different componants

Yep, I'm building a new motor soon and have to decide if I will do piggyback or standalone. For now I limit it to about 11psi max on stock turbo and its A/F is OK.

Good Luck blue TII

Well, it beats the heck out of a draw-through setup, but it's going to be a PITA to modify everything to take the higher pressure.

Yes, you can change your jets to run alcohol, but then you have to spend all weekend to re-tune it. Also, you will need to install a special alcohol carburetor, alcohol fuel lines, alcohol fuel cell, alcohol gaskets, etc. I'm not sure if it is worth the trouble.
http://terrasol.home.igc.org/alky/alky2.htm

Blow through
 

TTHE CHANGE WILL BE EFI AND HALTECH

stand alone and carb same cost?

I dont think so dude

Turbo II 4 barrel manifold $199
Holly mechanical 650 Double Pumper Sealed $385 (new)
*you can find some good used ones way cheaper*
Turbo Hat $100

under $700 with jets
-----------------------------
-Standalone-
1600cc Injectors $180
custom secondary fuel rail $100
Haltech E6K $1300.. w map sensors etc
F9A $900
SDS $900

standalone (if using the $900 ECU's) $1180

thats about a $500 diffrence

you can use the $500 you would save
to get a fuel pump
fuel reg
intercooler piping
clamps
hoses
wastegate deltagate

You can't use any old carb off the shelf.&nbsp It has to specially prepped to handle positive pressure from the turbo.&nbsp On top of that, if the carb happens to backfire (a real possibility), you'll lose the carb totally.

You'll also needs to run a "carbon seal" turbo - the "dynamic seal" turbo was not meant to have any contact with gasoline; gasoline will seep past the dynamic seal.

Unless you're drag racing only, you can't go over 15psi with the carbon seal.&nbsp This means on a street car, it's low boost only.

This really shouldn't be any discussion.&nbsp EFI is a vastly superior system, especially if you're going to street everything.


-Ted

7.6 1/4 time on weber carb
mid 8's on holly
EFI is better of course
but for a low budget carb is fine

you can use a marine holly or a get a holly sealed

where can u find a SHOW ME!

-mike

I have been running a Cartech weber 2C System for a couple of years and it works great. People like to compare Injection vs. Carburation and you should stick with what you know best. Help is always good but, how much is it going to $$$ cost $$$ you. I prefer the Weber IDF Carbs over all the rest of the models available. The Carb is ready to go out of the box all you need to upgrade is the needle and seat to a Gross Jet.

I like the Holley Carbs because of availability but, it is a much superior design for Turbocharging compared to the Weber. I have some pics I can put up this weekend with both Carburated Turbo Systems I built for my car.
The Cartech 2C Weber system is awesome. The Holley 650 Double Pumper is KILLER it should make a lot more power than the Webers.

Albert