Just saw this last night...CB Drawthrough

[SamT]

[buguy]

The problem with that is it would cost just about the same as making 75 more hp. And using new parts wouldn't be cheap. I mean a new turbo is going to cost nearly a grand by itself. The way those that have done it cheap is by using a used turbo and most likely a used carb. Not many people would buy a kit filled with used stuff. Big difference between $50 and $1000. And that's just the turbo.

[oprn]

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[-Alex77-]

Definetly american style system
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[buguy]

Is there some sort or octain conversion for propane? How do you know where to start with a tune?

[SamT]

[BFB]

isn't the propane a form of injection and not subject to flood at steep angles like a gas carb is? I thought I read of some rock crawlers running propane for this reason?

[modok]

Yeah they always turn to one design VS another, but that's because you see something a little different and you think about it, gives you some new idea. That's what I really always enjoyed about car shows ect, tho a lot of times these days I don't see much thought provoking

If you run liquid/mist through a compressor or supercharger, it has a great direct cooling action. Propane....does not, so if used for a dwarthrough system it does solve one common problem but loses an advantage. You could still use methanol in there for cooling/enrichment, skys the limit but I don't like dual fuel systems much myself because there more chance of oops.
But I do like thinking about it different ways.

This idea, makes me think for instance of how you could have a turbo, but rely on the turbo LESS. I heard YEARS ago a turbo likes long gears.....and that's kinda true, in a lot of cases.
BUT, how bout this: Run a big echaust housing so it won't spool pre-maturely cruising the highway, but use a LOW second gear, so it will hit go through second QUICK and hit hard in third. Still blazing acceleration but done a different way
Close ratio 1/2 and wide 3/4.....the OPPOSITE of usual. I'd love it. If you never drove one with a low second your missing out.

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[modok]

a very light bug/buggy is worst case scenario for trying to spool itself on the highway IMO. This is because
-exhaust path to turbo is LONG thus an unfortunate amount of lag from tubes heating up.

-It's so light you are fighting air resistance more than weight at most higher speeds, and you can't overgear it much or the cooling fan isn't going fast enough. With most cars radiators and intercoolers work FAR better at speed, which allows you to get away with a lot more sin, but.... not ours.


-If it has enough power/weight it will accelerate fast, and outrun the turbo in the low gears.
interestingly, the more rapid the acceleration becomes, the more "lag" it has, not that it has more lag, it's accelerating faster than the turbo

So, maybe it's not a problem for you at this time....but it can happen, and it does happen. Depends what you want. some people want a streetable race car, some want a raceable street car. I would not find it acceptable if adding a turbo to my buggy lowered my sustainable top speed.

[Splitdog]

At 3000 rpm on the freeway I'm at 20 hg's of vaccuum. Just like NA.
Yes, turbos love to be bogged. I have 3:88's in mine and I only boost in 3rd and 4th. I'm wasting my time in 2nd, because I'd rather short shift and get it in 3rd. Then I've got one hell of a long pull in 3rd. That's when we change lane position.
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#notacallooker

[modok]

yeah that third gear is....feels me like falling. it's crazy!!
Each setup has it's owns quirks and IMO, just work on it, a lot can be done. To be honest I THOUGHT a drawthough was a stupid idea, until I saw a few done right and IN FACT the street manners are quite good if you can get the details right. Grass is always greener on the other side but it isn't, example:
Drawthough you shift gears the compressor is spinning in a vacuum...... Blowthough when you shift gears your still pumping air slowing down the turbo. So maybe I'm as guilty as anybody. I should build the engine THEN choose the gears based on how it actually drives, but. you get the idea. One step at a time, you get far......and ultimately one setup may end up far apart from another. One system needs a timing map like the rocky mountains....another just likes 28 degrees

[oprn]

Now there is a difference I have never thought about!

In a draw through at cruising your throttle plate upstream of the compressor is going to keep you in a vacuum condition regardless of what the turbo is trying to do. Your foot has direct control over the boost pressure but not turbine speed. The turbo at cruise is free wheeling not causing much extra back pressure on the engine.

On a blow through at part throttle the throttle plate is holding back compressor pressure and the turbo could be loaded even at cruise. This would increase exhaust back pressure, heat up the intake air, reducing engine efficiency and reducing fuel economy.

Is that where you were going with the larger housing and later boost Modoc?

If this is the case then the same would apply with fuel injection depending on where the throttle body was placed, upstream or downstream of the compressor.

Now that I think of it, that could be the reason for the different "feel" between my Rabbit and my wife's Subaru. With a quick shift on the Rabbit you get a kick in the butt as that free wheeling turbo grabs air again and turns it's momentum into boost. The Suby with it's throttle body downstream doesn't do that because the turbo is slowed down when you release the throttle to shift and has to build speed again.

Make sense?

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[SamT]

[SamT]

I run the T04B35 cb performance used to sell. It may be a touch small for my 2332. It spoools up in neutral at about 3500 rpm and if you get over 3000 driving in high gear it builds boost even if your trying to baby it.
I've got pretty short gears for the sand. I don't have trouble boosting in low gears even since they are short. The BOV makes it where you don't start over when you shift.
Keep in mind that mine is basically a drag motor that's had the compression dropped and the cam duration tightened some for the turbo. It's amazing how much air that thing pumps then a more traditional turbo motor with little heads and cam.
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