[TasRat]

Did a bit of a search and didn't find much on this

Been thinking of bolting a AMR300/500 type blower to carby fed 1.3, not knowing much I figured I'd just plumb it straight to the top of carb and supply a bit of pressure above atmosphere, nothing huge, I'm assuming the carb will feed more fuel due to extra air flow & maintain mixture

Anyone tried it? Or got useful info

[SierraDan]

I disagree.................

[atari4x4]

don't listen to the haters, i say do it & post up the results when you get a catastrophic failure or just fail

[wolf_rt]

blow through carbies suck...lol

[Fatzook]

wolf_rt wrote:

blow through carbies suck...lol

I see what you did there

[303zuke]

TasRat wrote:

Did a bit of a search and didn't find much on this

Been thinking of bolting a AMR300/500 type blower to carby fed 1.3, not knowing much I figured I'd just plumb it straight to the top of carb and supply a bit of pressure above atmosphere, nothing huge, I'm assuming the carb will feed more fuel due to extra air flow & maintain mixture

Anyone tried it? Or got useful info

Did you find THIS THREAD?

I wrote this about "Suck-Thru" Vs "Blow-Thru" carb set ups:

"Supercharging works to create more power by cramming more fuel and air into a given space. Carbs are simple devices that meter fuel by vacuum in relation to the flow of air past a Venturi.

Nothing changes in this relationship when the carb is upstream of the supercharger, and the accurately premixed Fuel/Air is compressed and passed into the engine. No modifications are required to the carb or jetting. The stock standard carb "thinks" it's working on a bigger, or faster revving engine flowing more air.

When the supercharger compresses the air before it gets to the carb, it upsets the balance. There is now denser air passing the venturi, which requires more fuel for a correct mixture, but the venturi only works on airflow. The air/fuel mixture is too lean, and at the higher compression ratios, this can cause pre-detonation and possible engine damage. You are required to fit larger jets to compensate. Also, depending on the particular design of the carb, with the higher pressure of the air passing through the carb, there may not be sufficient vacuum created to draw sufficient fuel (in fact, there could be positive pressure forcing fuel back into the fuel bowl), creating an even leaner mixture. Modifications to the carb are required to provide an air passage to the fuel bowl to equalise the pressure (which in turn runs the risk of crushing the float, upsetting the float level in the bowl and your fuel mixture). In this situation, the fuel is also becomes pressurised and the fuel pump needs to be adjusted or replaced to pump at a higher pressure to overcome the needle/seat. And lastly, depending on the condition of your carb (age, wear, etc), there is the chance of air leaking past the throttle shaft under pressure, throwing away any chances of properly tuning your carb."

Lean-Out Detonations are the biggest killer of poorly set-up supercharged engines, and it has nothing to do with excessive boost.

[TasRat]

Awsome Thanks for an inteligent response, No I didn't find your thread - wish I had.

I incorrectly thought the fuel was drawn by air flow in the venturi rather than vacuum, so it might work if the carby goes before the blower. I was thinking the carby would up fuel just like at higher revs as you say.

[youda]

what about blow through carbs? i have heard of these on old turbo cars possibly corollas

[stocker]

maybe im not directly attempting to answer your question but....



Fuel Injection and Forced Induction just go hand in hand...

Have you thought about doing a Conversion to like a G13B? ... or at probably the same cost as your Blower/Blow Through (your pistons) Setup, G16B Conversion...

[TasRat]

I'd go for an engine upgrade if this one croaked, but I've always got my eyes open for a bargain, Just looking for some cheap ponies at the moment. A mechanic mate's, mechanic son is sticking a similar blower on an 80's Carolla, I think he's planning on using the same carby before the blower. It'll be interesting to see how it goes.
The reply above answered the question re blow thru,
not familiar with the engine No's is that the Vitara motor?

[stocker]

g16a (carby 1.6) G16B (EFI 1.6)

[sideways]

You'd have to over speed those superchargers somewhat. AMR300 (or 500) = 300cc of air being displaced per revolution, a 1.3l would need 650cc in naturally aspirated form (assuming 100% volumetric efficiency), let alone making boost.

Anyone know how fast these superchargers will happily go?

[shneva]

im thinking of doing the same sort of thing on my vit, doing a sc12 super charger with a suck throu weber.

[wolf_rt]

only problem I see with suck through set ups is you cant run an intercooler (afaik) so you can easily run into problems with the intake charge becoming overheated (causing richer mixtures, causing more heat...) and general overheating.

have you considered the toyota SC-14 unit? they can be found fairly cheap, they are set for 0.7bar for a 2L 6cyl
http://superchargedsilvia.50megs.com/about.html

[303zuke]

TasRat wrote:

Awsome Thanks for an inteligent response, No I didn't find your thread - wish I had.

I incorrectly thought the fuel was drawn by air flow in the venturi rather than vacuum, .....

Well, it does relate to air flow, but also pressure drop. The vacuum is created by the Venturi, I'm not talking about Manifold Vacuum. It's a similar principle to a spray gun. The venturi throat in the carb will create a specific pressure drop relative to atmospheric pressure. This specified amount of vacuum is used to calculate the jet sizes to give the correct air/fuel mixture. It's why race teams (cars and bikes) change jets for different racetracks (altitude) or for different weather conditions (barometric pressure). When the induction pressure is higher than atmospheric pressure, the vacuum drop in the venturi will still fall by the same amount, but it will be 4, 6, 8 psi (or whatever boost) higher than the correct vacuum to draw the correct amount of fuel through the jets. Larger jets are required, and there are some "Rule of Thumb" calculations to work out approximately how much larger for a specific boost, but optimal A/F ratios can only be accurately measured with an exhaust gas analyser.

[SuziBlu]

303,

I am done with the idea of adding a supercharger, but still interested, specially in what you are saying.

Your words ring in a lot of sense, but, I have always read, and was of the belief that suck thru was not as good as a blow thru, because the dry fuel tended to burn out the rotors, where as a blow thru didn't.

What you are saying sound very logical, at the same time, wouldn't a carby set up for blow thru be preferable to simply bunging on a common ole carby on top of a blower and letting it be fooled itno thinking its needing to richen the mix as the more air requires ?

There are many carbys set up for blow thru off the shelf.

[TasRat]

303zuke wrote:

TasRat wrote:

Awsome Thanks for an inteligent response, No I didn't find your thread - wish I had.

I incorrectly thought the fuel was drawn by air flow in the venturi rather than vacuum, .....

Well, it does relate to air flow, but also pressure drop. The vacuum is created by the Venturi, I'm not talking about Manifold Vacuum. It's a similar principle to a spray gun. The venturi throat in the carb will create a specific pressure drop relative to atmospheric pressure. This specified amount of vacuum is used to calculate the jet sizes to give the correct air/fuel mixture. It's why race teams (cars and bikes) change jets for different racetracks (altitude) or for different weather conditions (barometric pressure). When the induction pressure is higher than atmospheric pressure, the vacuum drop in the venturi will still fall by the same amount, but it will be 4, 6, 8 psi (or whatever boost) higher than the correct vacuum to draw the correct amount of fuel through the jets. Larger jets are required, and there are some "Rule of Thumb" calculations to work out approximately how much larger for a specific boost, but optimal A/F ratios can only be accurately measured with an exhaust gas analyser.

Again Thankx
I hadn't consider some of the vacuum issues and was interested in the fuel bowl pressure implications etc.

[303zuke]

SuziBlu wrote:

303,

I am done with the idea of adding a supercharger, but still interested, specially in what you are saying.

Your words ring in a lot of sense, but, I have always read, and was of the belief that suck thru was not as good as a blow thru, because the dry fuel tended to burn out the rotors, where as a blow thru didn't.

What you are saying sound very logical, at the same time, wouldn't a carby set up for blow thru be preferable to simply bunging on a common ole carby on top of a blower and letting it be fooled itno thinking its needing to richen the mix as the more air requires ?

There are many carbys set up for blow thru off the shelf.

You're right, there are some carbs that will work as Blow-thru, and some that won't. There are a whole lot more though that will work perfectly as suck-thru. So sticking with a factory carb suited to a particular engine might rule out being able to choose Blow-thru if it's design isn't suitable, even though using a factory inlet manifold would make installation simple. One other point about where the carby is in a system is the volume of the manifold runners that contain compressed fuel/air. Consider what might happen with a backfire? Keeping the carb as close to the head as possible is best.

The point I was trying to make is there is a whole lot more to think about than just whacking on a supercharger wherever it will fit best. Supercharging is very much a science, and designing a system to give the best performance safely on a carby engine involves a lot of factors. An Efi system is better suited to supercharging or turbo (and Diesel better again), but the fuel system is just a small part of the whole equation. We haven't even discussed anything yet that should be done within the engine to adapt it for forced induction. It's not just a matter of finding a supercharger in the parts bin at the wreckers and making a bracket to fit it.

[Lockie666]

Lol how long do you think the poor old 1.3 liter engine would last being supercharged? I have heard of sierras being supercharged, but I can't really see the point in doing it. Just sounds like a never ending pain in the ass, but it will be good to see.

[atari4x4]

G16B.

[stocker]

atari4x4 wrote:

G16B.

For the win