J-Body Automobiles Forum banner
1 - 20 of 29 Posts

·
Registered
Joined
·
4,949 Posts
Got me, but it's too small for anything you plan on using it for in a Jbody :lol:
 

·
Registered
Joined
·
4,949 Posts
voiceless said:
Carbon seals, I believe. I could be wrong though. :lol:

Try google. :p

Got me, but it's too small for anything you plan on using it for in a Jbody
The turbo 3.1's came with a T25....
And if you read anything, were undersized for the motor. :lol:
 

·
Registered
Joined
·
1,026 Posts
Discussion Starter · #7 ·
well, the reason i'm asking is after the sale of the mustang trade, i picked up an 88 z24 5 speed and i want to try something completely different.

first of all, i yanked out all the fuel injection stuff, and replaced it with a carb LIM (with slight modifications ;)

2nd.

picked up a 3.1 turbo out of TGP's and plan on turboing the carb z24 with the turbo(if it doesn't work, i can always drop in the 3.1turbo.

setup is a whole lot easier than turboing with fuel injection :p

intake came from a s-10 1984 (2.8 4bbl)....

I'll be going with a draw-thru setup and therefore need carbon seals on the turbo as it will be compressing both fuel and air in the compressor housing.

hopefully i'll have this running soon enough :)
 

·
Registered
Joined
·
1,885 Posts
wow a draw thru set-up?!? say good bye to throttle response. and if you run an intercooler..... :-? good luck with that tho.
p.s. i had alot of problems with the draw thru design on my buick. carbs just dont know when the engine is running lean or not. i blew 2 headgaskets with this set-up.
 

Attachments

·
Registered
Joined
·
1,026 Posts
Discussion Starter · #9 ·
yuppers, that looks alot like what i'm going for, except i have more piping between the 2.

can't use intercooler on draw-thru.... can you imagine having fuel staying inside the intercooler ? just seems like a ticking timebomb to me...LITERALLY ;)... i have a water injection system in the box waiting for a project like this :pPP

i know with draw thru, you need to run an auxliary fuel source specifically for that... prevent it from running too lean... i'll be running one off a 2.8 stock injector on a vacuum/pressure switch.
 

·
Registered
Joined
·
1,885 Posts
those pics were from my 3.8 buick. the bottom end on a stock 3.8 109 block could handle upwards of 600hp before the main webs stretch and break :lol: wonder what the stock bottom end on my 3.4 can do....
 

·
Super Moderator
Joined
·
20,044 Posts
capitalsins said:
trying to get the most out of them on stock bottom ends ;)
You would get more with EFI.
Draw through set-ups suck, literally and figurativly. No one, I mean NO ONE, uses a draw through set-up to make power.

Guys that use turbo carbs, go blow thorugh, because the throttle responce is much better, easier to use a turbo that will match in size, not match in seal design, the turbo last longer. The fuel hitting the compressor wheel eventually eats away the fins, and also causes problems with fuel staying atomized through the entire travel from carb to cylinder.
The carb needs to be modified on the metering circuit, to be "rich" when at lower vacuum at the base plate, which means when you're in boost. The carb only knows thatthere is low vacuum at the base plate, it doesn't know that there is a turbo right below it, causing this low vacuum.
In a lot of draw-through set-ups, drivability was an issue as well, for the above mentioned reason, of the carb not knowing how much boost is being generated, or rather being able to meter a proper amount, most draw through set-ups ran pig rich at part throttle cruise, because the carb would just dump lots of fuel in.
Adding a secondary fueling system is just a band-aid on a poorly designed turbo system, where just moving the carb to a blow through set-up, solves a whole bunch of issues, like fuel attomization, it stays that way due to the shorter distance between the carb and the cylinder, the turbo lasts much longer as there is no longer fuel hitting the compressor wheel and eroding it. The Compressor is flow air only, as it was designed to do.
You don't have to screw around with odd throttle linkage, and in a case where it was originally a carbed vehcile don't have to modify it from stock, drivability is MUCH better, because the vacuum signal and boost refernce to carb is much cleaner, and also much more linear.

Better yet, keep it EFI, and make driavbilty that much better, with tune-ability that is not available to a carb set-up, such as being able to pull spark outunder certain conditions, where a dizzy on a carb set-up only really allows for a ramping of timing, and then staying there. You could attach vacuum/pressure pots to a vacuum advance type dizzy and be able to retard timing at a certain boost level, but then it will stay retarded after that, no being able to advance it again, later in the RPM band. Yes some engines like to have spark pulled out in there mid RPM band, or like more or less fuel at certain points, like peak of the torque curve generally takes less fuel than below and above it, whihc helps make even more power when tuned right.

I'm a huge pro-ponent of EFI, and have been for many, many years, I've converted two of my cars from carb to EFI, and have helped a friend convert his 348 (same as a 409 essentially) to MPFI, and I'm currently tuning it for him.

Once an engine is tuned properly, with EFI, no one evers seems to understand why they used a carb, which at newest is 40 year old technology, sure there have been some updates since the '60s, but it still runs on the very same priciples and has the very same short comings it did back then.
 

·
Registered
Joined
·
1,287 Posts
I'm with him ^^^. I've been around long enough to have grown up with carbs. I've retrofitted several vehicles to efi with great success. there are aftermarket boxes which can reduce spark advance as cylinder pressure increases, and others which can reduce timing under detonation. But the stock ECM already handles that job.

The earliest EFI'd GN used "draw through" setups with T3's. They worked and guys have made some decent power with them. But it's only possible because fuel response is controlled by the ecm and the fuel is still delivered at the intake valves, not by a carb. The throttle body is mounted at the end of the turbo and the only thing drawn through the turbo is air.

Anyway, you're right in thinking it's different. Good luck with it.
 

·
Registered
Joined
·
1,026 Posts
Discussion Starter · #16 ·
sixshooter, those are all valid and respected points....

i'm doing this out of pure boredom to be honest, like dropping 2 eaton sc's on a 420a eclipse, converting a civic to a RWD, converting a station wagon cavalier into a 90's el camino...

i got nothing better to do and plenty of parts to play with... like i said, if it turns out to be $h1t, i'll drop the 3.1turbo in the car and be done with it.
 

·
Registered
Joined
·
1,885 Posts
slowolej said:
I'm with him ^^^. I've been around long enough to have grown up with carbs. I've retrofitted several vehicles to efi with great success. there are aftermarket boxes which can reduce spark advance as cylinder pressure increases, and others which can reduce timing under detonation. But the stock ECM already handles that job.

The earliest EFI'd GN used "draw through" setups with T3's. They worked and guys have made some decent power with them. But it's only possible because fuel response is controlled by the ecm and the fuel is still delivered at the intake valves, not by a carb. The throttle body is mounted at the end of the turbo and the only thing drawn through the turbo is air.

Anyway, you're right in thinking it's different. Good luck with it.
X3 on efi. :lol: i wish i had pictures of all the ic piping i had to fab up to convert my HOT-AIR TR to intercooled. plus a powerstroke intercooler :eek: :lol: six did a good job of laying it all out on the table, nice work. if you still arnt convinced to stay efi then check out this link(s).
http://home.flash.net/~rjgeorge/ carbed turbo performance
gnttype.org has a couple recipes on hot-air setups
 

·
Registered
Joined
·
1,026 Posts
Discussion Starter · #18 ·
i see that most are fans of EFI.

i'm not doing this for pure power, or to blow every car out of the water, i'm doing this as a learning experience, and to try something different.

there's a guy down here that developped something pretty interesting and it's actually running and ran an untuned 14.7 on the 1/4 mile.

he's running 3 vacuum injectors into his intake piping, and as boost increases 3 more kick in to compensate for the extra air going into the engine.

he's running stoich on idle, when he floors it, the engine runs lean until about 2200-2400 RPM, then the other fuel injectors increase fuel as pressure increases and seems to be running optimal until the end of this RPM scale.

his setup completely behooves me, but no carb, no EFI, just vaccuum injection (kinda like a carb)

i'll try to get a vid of this, but he was iffy about me taking pics.
 

·
Registered
Joined
·
1,287 Posts
The reason computer controls are so popular is that they work. Even if you don't use the ecm for fuel, consider using it for spark. I've done a traditional carb with ecm controlled spark and believe me, there's a world of difference over a vacuum / mechanical distributor.

There are plenty of ways to get fuel into an engine. The first engines would boil fuel in an open container over a heat source and as the vapors came off the top they were drawn into the engine and burned. But the real trick is to get the right amount of fuel to the engine under all driving conditions. The ?vacuum injectors? sound like a very crude way of getting the job done, but if it's a strip only car it's got far fewer conditions to deal with. No warm up times, minimum idling, no cold weather driveability, no rainy days... all conditions that add to the complexity of an automotive fuel system.

If you build a draw through carb system you're in a neat position if you really want to experiment. You can route the compressor outlet mixture through a heated manifold to try and convert all liquid gasoline to vapor. You have to size the turbo small to do this because fuel expanding from liquid to gas will try and force the usable oxygen out of the engine, and the turbo will need to work as a check valve of sorts, creating positive pressure even at idle. Stories are that the original builder of this system was able to make gobs of power while increasing fuel mileage drastically at the same time.

Whatever you do, be sure to post progress pics. :)
 
1 - 20 of 29 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top