rx7speed

I'm just curious here as to what the differences are between them in operation and what you would need to set one up and tune.

sleepybu

have you tryed a

rx7speed

actually I did and didn't find a lot of the info I was looking for.

maybe you could lend a hand since your here?

Project

Draw through means the carbs sit on top. Like in a roots blower- PULLED through

Blow through means the air is PUSHED through...

Check out the turbo mustang site...TONS of info...people say blow thru doesn't work....lots of guys running insane setups with 25lb+ boost...one guy on the board has a 1200hp setup with a powerglide that he takes on the street regularly.

rx7speed

understand the differences with how they work. but tuning differences?
would I need a blow off valve on a draw through setup.
how much worse is the lag going to be on a draw through?
what about mounting differences wit hthe draw through

PhLaXuS

According to Corky Bell, the draw-though is somewhat more inferior. I get the feeling that he also doesn't much care for carbs at all.

Off the top of my head, I think the lack of an intercooler is your biggest challenge. That alone makes it worth discounting draw-through as a viable option.

rx7speed

for low boost (6-8psi) would you relaly need an intercooler?
aren't a lot of stock carbed turbo setups non-intercooled?
also I could swear there are guys running roots s/c without an intercooler.

but yeah if I could an intercooler would be something that would be nice.

what other complications would I need to look at with either design as tuning carbs isn't my strong point.

tommyt

Draw-thru takes a special type of carb, with the seals set up to have gasoline being pulled thru the turbo. Most carbs are not set up for this. Blow-thru poses a different set of problems, which would be sealing the throttle shafts etc. but this is usually done pretty well, so they work ok, especially on lower boost motors. If had to choose, I would say blow-thru is better most of the time. The carb would have to be modified specifically for each type of setup. (Draw-thru would be more like a roots blower type carb, blow-thru more like a centrifugal blower type)

PhLaXuS

Very true, but in my personal opinion, a forced induction setup without intercooling is a job not yet complete -- good for testing & proof-of-concept, but incomplete. I think OEMs are to blame as they sometimes leave the IC out for cost reasons. If the engineers had any say over the penny-crunchers, they'd have one in every car.

Roots looks cool, but not too efficient (I think they're around 50%).

rx7speed

isn't it the turbo that needs to be special with carbon seal or something like that.
this way when under load the turbo doesn't start getting oil sucked past it's seals.

as far as blow through I'm sure I would not go with just a hat on the carb but rather a whole box to surround the carb. this way pressure inside should be close to pressure outside so as not to leak air.

one of my worries with a blow through system though is tuning. it seems it would make it more difficult to tune and would require a fuel pressure regulator which I would have no idea how to setup for this application and I'm sure some type of BOV which wouldn't be that hard

Project

Intercoolers are totally optional. My VR4 Ball drive hits 14lbs of boost and I make MORE power without an intercooler...with an intercooler I was hitting 11lbs and loosing 2 tenths...

Gear drive s/c make a ton more heat vs old ball bearing style.

nightrider87

That's twice in the 2 min i've been browsing the power adder forum that i've gone after reading one of your posts.

A draw through carb doesn't need any modification to work, its metering air just like it thinks it should be. You'll barely have to fatten up jets.

Blow through carbs need a bit of modification. Removal of the choke tower and solid nitrophyl floats are really the most necessary. Throttle shafts on the holleys are decent and those on the edelbrocks are better....but either is going to do just fine up to high boost levels...like 20+

oh and in regards to hat or box. The extreme velocity hat is getting great reviews from everyone. I'm ordering one this week.

tommyt

Sorry, that was a typo...I meant specially set up turbo...as can be seen from the rest of the sentence...
So, You dont think the power valves on a draw thru setup should be boost referenced ?

tommyt

As for blow-thru, the floats are needed, the choke tower milling also, but I started with a HP carb, and it had those done out of the box, so didnt have to worry about that. BUT:
here is what I did: o-ringed throttle shafts, enlarged PVCR holes, and installed big needle and seat assemblies. The HP also has the screw in air bleeds, so that will help too. I still dont know, only hope that the carb will be able to flow enough fuel...will have to wait and see. This is for my twin t76 BBC with A2W...I will make my own hat , I dont like the tight turning radius of the EV or similar hats, even tho they do have a divider built into them...
But never mind me, I'm just a noob

blue82_z28

how do you control the amount of boost you want to run with a draw thru setup??

83 Crossfire TA

iTrader: (2)

That’s a trick question, right?

Same way as you do a blow through…

rx7speed

so why do you need to mill the choke tower on a blow through setup?


and for a simple 6 psi lower power setup would you guys say for ease of install to just to do a draw through then? also how can I find oout for sure if the turbo is the positive seal type?

83 Crossfire TA

iTrader: (2)

[QUOTE=rx7speed;3284732]so why do you need to mill the choke tower on a blow through setup?[QUOTE]

So it doesn't blow shut or mess up airflow...

harleyd2900

Ok, I am not only new to this idea but new to this site. This topic was the topic that has drawn me in. I am building a Chevy 350 with my father right now. I have been entertaining the idea of turboing it. Which type of turboing would be the cheapest and easiest for me to do in my back yard. What parts are exactly needed? Does anyone have pictures of both methods of turboing?

Thanks,
Jimmy

TheMonster

Jimmy I am in the same situation. My dad and I are rebuilding my motor (in the sig) and I have been thinking about a turbo. If you have a welder and can fab up a manifold and an ebay turbo, with a modified blow through holley double pumper. I have to do a ton of reading though.

86CamaroTurbo

Can any one can help me with a blow through i need a part list on my 86 camaro

86trbota

Csu carb, aeromotive a1000, aeromotive 13202 regulator, -10 feed, -8 return