mazdeuce wrote:
Soooooo.....what are the carb mods needed to push air through a carb at mild PSI (maybe 5?) I know you need to build the sealed housing, but I'm fuzzy enough on carb theory that I don't know where to start. My understanding is that with most carbs, vacuum plays a central role to it all working. Is this one of those things where I need to be figuring out whether I have vacuum or mechanical secondaries? I probably need to buy that book, don't I?
Carbs work on a pressure differential caused by the venturi. This just so happens to cause vacuum in a NA motor. Remember that the fuel chambers will be pressurized to boost pressure(on the intake side of the carb) here. As long as its in a sealed box, or all the vents are hooked to a boost source, it will work fine. Vacuum secondaries will still work, with some tuning, I think, they will open whenever you get into boost.
e_pie wrote:
Do you have any videos of this? I want to hear a Geo engine spinning 9k RPM.
How do you build the engines in those, is there even an aftermarket or is it all custom?
Why am I so intrigued by the idea of modding a Geo engine?
I wish I did have a video of it. They sound a lot like a bike motor, being a 1.0L triple. I have a pic of the car somewhere.
The only aftermarket for those motors is me. Beyond that, you're mixing and matching OEM parts, which are generally very good, or making your own. Swift GT rods, later 1.3 16V pistons for lower compression, and you're good for lot's of power, and RPM, as long as you fuel and time it right.
That motor had stock pistons and rods, and would have lasted for many runs, but ultimately heat destroyed it. At those power levels, and no intercooler, a 1 mile land speed run just allows too much time for heat to build up. On the street, or at the quarter mile, it would have lasted forever. I have customers and friends making 200 reliable hp with those motors.
There is some Geo aftermarket.....
Chassis and some turbo stuffs: http://www.turbotuningturbinetech.com/en/products/swift.html
Cams and head packages: http://www.teamswift.net/3tech/
Check out www.teamswift.com , lots on there for the Geo's and Swifts with the G13B. The tiny chassis is fun with boost, I loved my last boosted Swift (in my avatar).
airwerks, welcome to the board! Stick around. Pull up a chair and crack open a brew.
BTW, I believe Zomby Woof IS TeamSwift, just FYI.
This austin 1275 draw through has a primitive a/w intercooler built in. So you CAN add an intercooler to a draw type, but this is the only one ive seen.
And I know not much about turbos, just though I would share that oddity.
You can put an intercooler on a draw type, but any gain will be negated by the atomized fuel inadvertently condensing to some extent no matter what you do.
In reply to airwerks:
I am 3tech, and the turbine tech stuff for the Metro is discontinued.
tuna55
PowerDork
5/15/13 9:29 p.m.
Zomby Woof wrote:
In reply to airwerks:
I am 3tech, and the turbine tech stuff for the Metro is discontinued.
ok, 200 hp, and how many dollars and how many pounds? I am thinking this needs to be in a Challenge car at some point.
OP, I am seriously sorry if we are hijacking your thread.
Kenny_McCormic wrote:
mazdeuce wrote:
Soooooo.....what are the carb mods needed to push air through a carb at mild PSI (maybe 5?) I know you need to build the sealed housing, but I'm fuzzy enough on carb theory that I don't know where to start. My understanding is that with most carbs, vacuum plays a central role to it all working. Is this one of those things where I need to be figuring out whether I have vacuum or mechanical secondaries? I probably need to buy that book, don't I?
Carbs work on a pressure differential caused by the venturi. This just so happens to cause vacuum in a NA motor. Remember that the fuel chambers will be pressurized to boost pressure(on the intake side of the carb) here. As long as its in a sealed box, or all the vents are hooked to a boost source, it will work fine. Vacuum secondaries will still work, with some tuning, I think, they will open whenever you get into boost.
Wait, does that mean that you need to dial up fuel pressure with boost? I did that with fuel injected cars and always understood that it was a way to make fuel delivery sort of non linear. More boost needs more fuel, add more pressure, get more fuel. But in a carb the bowls just need to stay full, and to do that you'd need fuel pressure above boost pressure. And.... crap, I need to read about carb theory more.
In reply to mazdeuce:
Precisely, fuel pressure needs to lead boost pressure by 6lbs or whatever your carb typically desires.
Which just means your carb-type fuel pressure regulator also needs to be in the box with the carb and you need an electric fuel pump in the TBI fuel pressure range (12-15 psi).
Zomby Woof wrote:
In reply to airwerks:
I am 3tech, and the turbine tech stuff for the Metro is discontinued.
Dang name changing tom-foolery! 
I'll be bugging you for a set of cams when I get the Colt swap finished up......
In reply to tuna55:
It can be done for challenge money. I brought my 87 car to the challenge in 03. I was pressed for time, so it was fairly stock, and probably in the 100 hp range (at 1450 lbs). A cam and a few tweaks, and I was in the 14's in the quarter, and 116 in the mile. I still have it, and almost $1k budget room, so I may bring it back someday.
