Blow through

[Mojo_stevo]

Can you put a blow though set up on a carbureted car? I know the Corvair had the draw style what was the point of that?

[Hit_N_Run-player]

Draw through is harder to plump, but is said to be better for the fact that you dont have to pressurize any of the fittings on the carb for boost. But everyone has there own opinions on what is best, i would say Blow through would be the easiest to assemble, but the draw through would also work well..

[Mojo_stevo]

Now is there any risk with draw though? I mean you are packing a fuel mist into a hot turbo right? I am more attracted to the blow through design, it seems to be far more popular by a vast amount, hopefully lead by the fact that it produces better results.

[beyondloadedSE]

This doesnt specifically apply to carb. cars, but here is why people prefer a draw through instead of blow through.

A draw through is easier to tune. Youll lose about 20-30% resolution on a blow through setup. It also leaves more room for power since its pulling through colder air (i.e. wont peg 5 volts) as opposed to being on the hot side of FI. The hotter the intake charge the less airflow the MAF read. The less airflow the MAF reads the less fuel. (load & airflow readings) The less fuel the leaner it gets. That's the exact opposite you want to happen as the intake charge temperature rises. You'll also take the chance of coating the MAF in oil which will really screw up your tuning, since no turbo on this planet is absolutely 100% totally oil sealed.

[nissanfanatic]

One reason that blow through on a carb would be beneficial is that it is easier to set up a blow off valve. On a draw through, when you vent to atmosphere, you would be venting fuel out as well.

[Black Lotus]

Suspect that the Corvair had a draw-thru because they could use an exsisting carb (Carter YF?) without modifying it for shaft seals, float, etc. Also, there was no thought at the time it appears, to intercool the engine or to worry about emissions. I had a 2V carb on mine (draw-thru) with a Rajay E-flow turbo, custom made manifold with a central plenum and 6 runner tubes going down to the milled off heads. And I must say, the drivability totally sucked in the winter. Starting it was a beast! Would hate to see what the emissions were.
You pretty much have to use a bypass valve on a blow-thru-carb version. If you don't, you'll prolly blow fuel out the throttle shaft seals and more fuel thru the idle circuits when you lift the throttle to shift. Big ball of fire out the tailpipe. Old UK Lotus Turbo Esprits with carbs (blow-thru) do that at times even with a bypass valve.

[Hit_N_Run-player]

Originally Posted by nissanfanatic

One reason that blow through on a carb would be beneficial is that it is easier to set up a blow off valve. On a draw through, when you vent to atmosphere, you would be venting fuel out as well.

Thats one of the things i ran into when trying to figure up draw through on my kart..venting gas into the atmosphere through the BOV...

[Mojo_stevo]

Yea I'm not crazy about blowing a nice fuely mist about it my Nova's engine compartment. I could hear it now "rrraaaaaaawwwwwwww--psstt--frrrrwwwooooooosh"..."So explain again how you lit you car on fire?" LOL