Blow-Through and Draw-Though systems

[Mk1Crazee]

Hi

Anyone heard of the old school Blow-Through and Draw-Though systems?

It was implemented to support turbochargers on a carb engine.

Mind = Blown

[panic-mechanic]

I turboed my 2.4 double cab hilux using blow through yes. I don't like suck through as you now have a lot of piping filled with an explosive fuel mixture.

[chucker02]

I turboed my 2.4 double cab hilux using blow through yes. I don't like suck through as you now have a lot of piping filled with an explosive fuel mixture.

I have always been facinated with carb turbo motors. Wanted to turbo my beetle when I had it but it was my only car and didnt want to mess with it as it was extremely reliable. What carb did you use?

[Mk1Crazee]

How is it tuned? How did it run successfully without a management system?

- Fascinated

[panic-mechanic]

Dellorto 36 dhla. One of the very few carbs that was made for blow through.
You tune it on a dyno just like anything else. Change jet sizes until you get the fuelling right.
Blow through needed you to raise the fuel,pressure just like you do with efi so you run an efi style fuel pump with fpr that is rising rate.
On the ignition they used to just limit max timing allowed by the distributor.. I used a fully mapped ignition system taht was built by perfect power.. So had fully electronic controlled and boost /rpm based timing which allows you to run fast timing out of boost and slower timing in boost like most efi systems does now.
The blow through carbs had the ability to be leaner out of boost and richer in boost where a suck through you had to tune the entire rev range rich and that was it.

[Mk1Crazee]

Interesting. I know you hate carbs though.


can this be implemented on Sidies too?

[panic-mechanic]

It's one of the reasons I hate carbs. The hilux would use fuel like no tomorrow. As in 2.8 km/l or 35.7l/100 for the modern crowd.
You can use a single sidedraught to build a draw through and that is what most people did.

[PapaJo]

Interesting. I know you hate carbs though.


can this be implemented on Sidies too?

Suck through easier on single sidie.

Blow through, same setup applies as described by Painc in previous post. Keep in mind that the square cover on the sidies at the airjets have to be sealed off or you would blow the fuel out of the carb.

[Mk1Crazee]

So this only works on certain carbs? like downdraft webers and dellos?

[panic-mechanic]

You can suck through any carb. To blow through it it had to be designed for it specifically and there literally ever was a handfull of those.

[Mk1Crazee]

This is really interesting.

Although modern EFI systems makes this alot easier. i can see why many people are not going this route any longer. (Especially with the horrible fuel consumption)

[panic-mechanic]

It's pretty much last century

[ALRoN73]

Worked for him even though it's last century.

[Mk1Crazee]

ahhh the DungBeetle. perfect example of this thread. Yet even he eventually went EFI with a Haltech management system to keep up with the guys

[ALRoN73]

ahhh the DungBeetle. perfect example of this thread. Yet even he eventually went EFI with a Haltech management system to keep up with the guys

Yeah, but it worked

[Mk1Crazee]

Yeah, but it worked [/quote]

Yeah worked like a charm. Ultimate sleeper with last century's technology

[V6 Capri]

A friend of mine is a bit of a carb guru, and he runs a turbo pinto motor in his MK2 Escort. Swears by it. Also loves giving people crap over it saying that fuel injection is only for people that can't tune carbs. Basically, the carb supplies the appropriate amount of fuel of the air going throuhg as the fuel is sucked through with the air. Pretty easy concept.


His system incorporates a boost box around the sidies that equates the pressure on both sides of the carbs. The air going through and the air around the carbs are at the same pressure. This eliminates the need to use a carb that can stand the pressure of blowing through them.

The sick through system is the one that has intreagued me for some time. See pic below. Apparently the fuel is enough to cool the boost down before it enters the engine and there is no need or place for an intercooler in this system.



Or, a more relevant pic maybe?

[billionairebum]

It's one of the reasons I hate carbs. The hilux would use fuel like no tomorrow. As in 2.8 km/l or 35.7l/100 for the modern crowd.
You can use a single sidedraught to build a draw through and that is what most people did.

Is this the same Hilux that you used when you put on a set of yello EBC brakes that lasted 900km or something similar? How strong was this damn Hilux??

[ALRoN73]

It's one of the reasons I hate carbs. The hilux would use fuel like no tomorrow. As in 2.8 km/l or 35.7l/100 for the modern crowd.
You can use a single sidedraught to build a draw through and that is what most people did.

Is this the same Hilux that you used when you put on a set of yello EBC brakes that lasted 900km or something similar? How strong was this damn Hilux??

Was so strong he had to drive on the brakes 24/7

[panic-mechanic]

I can tune carbs and still prefer injection. No matter how you look at a carb it is a linear device. So there are always a point where you cannot fix the fuelling when you make another point correct. So no matter how good anybody is the simple mechanics and physics of the tool younare using precludes you from perfecting fuelling at every stage of the rev band. So hence the reason i prefer injection and so does basically the rest of the world at this stage. You virtually cannot buy a car with carbs anymore. Why? Becuase they just are not ideal.

[panic-mechanic]

Hilux went from 55 kw on the wheels at the dyno I used at that stage to 120kw. 125 nm to just over 280 nm.

[Mk1Crazee]

Hilux went from 55 kw on the wheels at the dyno I used at that stage to 120kw. 125 nm to just over 280 nm.

wow that's a big jump! especially the torque figures.

[HendrikCTI]

Visit a site called www.Datsun1200.com

Couple of guys that turboed the A12 engine. One guy did this and competed in the under 2 liter class with racing.
I cant remember the details anymore but they used a SU carb from the Jaguar, I think it is a 1.8" SU, and then you make a suck through setup. The needle is removed and slightly changed on its profile as needed. Very time consuming. compression is dropped and also the distributor is re curved for the turbo setup. Not 100% sure but in the region of 110 to 120 HP at the wheels. Gearboxes struggle a bit with the power. Also the turbo seals are replaced with special seals to cope with the air/fuel mixture that is now send through it. Long time ago I visited the site.