# 16v 1.8 carbs... with a turbo???



## aaronl307 (Apr 26, 2009)

has anyone ran a 16v 1.8l with weber carbs and turbo setup? if not, can it be done? what do you guys think?


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## diceman469 (Sep 3, 2003)

*Re: 16v 1.8 carbs... with a turbo??? (aaronl307)*

Why? More trouble than it's worth. Here is a breakdown. An article from ford-truck.com, but fairly accurate in it's description:
Turbo's and carburetors
There are 2 ways in which a turbo can be set up with a turbocharger.
Draw through and Blow through.
With both set ups, the normal sized carb should be suitable.
Draw through
Far and away the easist of the 2 to set up, however there can be issues with it, and its performance isn't as great.
It, as the name suggests, draw air through the carburetor, to the turbo, which then compresses the air/fuel mixture.
Cars, such as the Corvair and the turbo Trans Am had such a system.
Benefits -
You don't need any form of adjustment for the carburetor to adjust fuel flow - as the carburetor is on the "atmosphere" side of the turbo, and therefore the pressure it sees is the same, therefore it is much easier to set up.
Detractors -
Poorer performance - The turbo now has to draw a much heavier fuel/air mixture, and therefore it isn't as efficient. Since fuel is much denser than air, it can seperate in the turbo, and pool, creating some turbo lag. The turbo can't be posistioned right on the exhaust side, and it requires longer headers - which will cause further turbo lag.
Also, given you are drawing air through the carburettor - which drops pressure, and then you are increasing the pressure with a turbo, means further inefficiency as you are compressing air from a lower pressure, and it will also increase your intake temp - and you can't run an intercooler (running fuel/air through one can be VERY dangerous (the fuel can condense inside the intercooler core and stay there if you then have an engine backfire the intercooler can explode), likewise a blow off valve shouldn't be used (it would eject a fuel/air mixture into the engine bay). Water Injection is the only way of cooling your intake charge.
If you are building the engine in the backyard cheaply, this most likely would be the preffered way to go, as long as you can live with the turbo lag, and don't want to run obscene boost pressures.
Blow through
More complex than the draw through arangement, but if set up correctly, has much improved performance.
It, as the name suggests again, means that the turbo is mounted before the carburetor, and it blows air through it.
To my knowledge this system has never been fitted to a production vehicle.
Benefits
Pretty much all of the detractors for the draw through set up are now reversed. You can use a blow off valve, an intercooler, turbo can be mounted on a set of real short exhaust headers, you aren't drawing air at a lower pressure etc.
Detractors
It is (as I mentioned previously) more difficult to set up. You have two major dilema's:
1. A carburetor can monitor air speed, and adjust fuel flow accordingly, but it can't measure an increase in pressure. Therefore, you may have a system making 15psi, and sending double the amount of air that a N/A engine would recieve, but the carburetor would only provide fuel for the N/A engine, meaning it will run super lean. As turbo's boost isn't linear, it can make it hard to tune.
2. You will now have a positive pressure, and it can cause headaches with your fuel flowing through your jets. The pressure will try to crush the fuel float, it's going to want to blow fuel mix out the throttle shaft, or back into the fuel line.
Also the carb must be sealed so it does not leak the pressurised air-fuel mix - it would be extremely dangerous. The best method I have heard of is placing the carb in an air tight box, and running a sealed throttle cable.
Because as the turbo increases boost that is more boost that the fuel pump must be able to overcome if it wants to push fuel into the carb. What you want is an electric fuel pump and a boost sensing fuel pressure regulator to increase fuel pressure as turbo boost pressure increases.
Fuel floats should be filled with something so they don't get crushed under the pressure.
For the black art of fuel enrichment (to adjust for the higher pressures that the carb can't monitor) I have heard some people overcome the first issue by just jetting the carburetor for when it is at maximum boost, however, when the turbo isn't at maximum boost (the majority or the time for a street driven vehicle) it will run horribly rich, and isn't really a suitible solution.
Another, better method is to have 4bbl carbs, the secondaries are jetted for the higher air pressures, and are operated by a vaccum system to open under sufficient turbo boost.
There are other more advanced methods, but if you want to attempt them, you (in my opinion) might as well run a basic EFI system, as most of them just attempt to mimic an EFI system.
So, what have you learnt after all this. Run EFI!!!


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## aaronl307 (Apr 26, 2009)

*Re: 16v 1.8 carbs... with a turbo??? (diceman469)*

thanks diceman... basically, my canvas is a blank slate... i have a 1.8l 16v long block... there are so many options out there, efi is definitely one of them...


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## antichristonwheels (Jun 14, 2001)

*Re: 16v 1.8 carbs... with a turbo??? (diceman469)*

Don't tell Lotus blow thru hasn't been in production.


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## B4S (Apr 16, 2003)

*Re: 16v 1.8 carbs... with a turbo??? (antichristonwheels)*

The above article is so full of errors it isn´t funny.
It´s complicated, so just go EFI.
Don´t tell ford-truck.com, but 300whp non-intercooled aircooled motors running draw-through want to make a few changes to their article. Fuel in the intake air will COOL the charge, and nothing atomizes fuel better than a blade whirling at 100000 rpm...
Yes, I am willing to admit that it´s not the most efficient setup however, but it´s far from terrible.


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## diceman469 (Sep 3, 2003)

*Re: 16v 1.8 carbs... with a turbo??? (B4S)*

I'm sure the article I posted is just as filled with errors as any typical wiki article. 
I guess the point I was trying to illustrate is for the level of PITA a turbo carb setup would give you, you can go EFI and make it run like it came that way from the factory. And thankfully there is enough of us out here doing 16vt that it's almost bolt-on easy, even if you don't want to buy a kit and are willing to do some reading to learn how to tune EFI.
On a motor that already has a carb setup, its easier to justify it. But to add a carb just to add it then have to mess with finding a manifold, jetting, linkages etc it just sounds like more trouble than its worth.
But of course this is just an opinion and is subject to http://****************.com/smile/emthdown.gif










_Modified by diceman469 at 8:28 AM 9-1-2009_


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## derek_mk1 (Oct 10, 2007)

*Re: 16v 1.8 carbs... with a turbo??? (diceman469)*

In the event where one has a 2.0 16, bare block and head, clean slate..... there trully is no advantage to going carb-turbo. If you go just turbo you're results would be better. If you go just carb your results would be better.
Carb-turbo is like those clowns in bresil who chose to go ITB-turbo-supercharge on a 1.6 20v. Sure it's cool. But surely beyond dumb.


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## B4S (Apr 16, 2003)

*FV-QR*

Ha...the brazilians have been kicking our asses at fast VWs for years, using far less technical equipment than we have access to. Beyond dumb is writing something off because it's not the highest-tech option you can get. A good builder/tuner uses knowledge from all areas.


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## derek_mk1 (Oct 10, 2007)

*Re: FV-QR (B4S)*

i agree with you entirely.
But seeing as how this gentlemen has access to both a turbo and a carburator, and i'm assuming he's starting with an empty block and empty head... he might as well just go turbo and probably develop more power than he otherwise would with a carb-turbo set-up. I know Bresil brings out some pretty quick cars, and i agree that sometimes the oldest tricks in the book work best...(i myself am using a weber set-up, because i believe it to be most reliable) but i'm sure you'd agree that advances, both in knowledge and technology allow us to achieve quicker cars. The buggati Veyron for instance, does not have a itb-supercharge-turbo set-up. Engineers in 2008-2009 decided a turbo set-up would suffice. And it seems as though it did.
This is what i was replying to, sorry if i wasn't clear:

_Quote, originally posted by *aaronl307* »_thanks diceman... basically, my canvas is a blank slate... i have a 1.8l 16v long block... there are so many options out there, 

All in all, if this guy is starting fresh, if he's gonna go carb-turbo, he might as well just go turbo. (and if power isn't a concern, than he might as well just go carb)


_Modified by derek_mk1 at 8:14 AM 9-2-2009_


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## B4S (Apr 16, 2003)

*FV-QR*

For sure, if it's a blank slate...don't go carbed turbo unless you're a die-hard fan of that setup.


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## derek_mk1 (Oct 10, 2007)

*Re: FV-QR (B4S)*

By the way, anybody ever try a carb(weber)-supercharge here in volkswagen land ?


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## water&air (Aug 1, 2002)

*Re: FV-QR (derek_mk1)*


_Quote, originally posted by *derek_mk1* »_By the way, anybody ever try a carb(weber)-supercharge here in volkswagen land ?


IIRC yes in the world or air cooleds (who also do alot of blow through turbos with excellent results).
if you are interested in blow through check out the tech articles @ cbperformance.com http://****************.com/smile/emthup.gif


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## xdawgedawg (Apr 12, 2009)

*Re: FV-QR (water&air)*

in the past, i have seen the 'blow through' setup on the air-cooled engines... but i never figured out how they controlled the fuel mixture... i was on an online site and i seen some fuel pressure regulators that raise the fuel pressure durning boost. would that work?
i read the 'blow through' setup by cb performance... milling and modifying a carb to be completely sealed is costly... i am not sure of the cost but it sounds expensive.
i also remember that the vintage shelby mustangs had an paxton supercharger option that enclosed(?) the carburetor??? 
i wonder what aaronl307 is currently running in his car?
dude, you gotta give more information on what youre trying to achieve..


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## aaronl307 (Apr 26, 2009)

*Re: FV-QR (xdawgedawg)*

here is the whole story, on our street, we have 4 people including me, that own mk1 and mk2... one day, one of the owners got rid of their mk2 for a bmw 135is. now, he says, 'vw sucks'. to me that is fine, but when he drives by, and i am tinkering with the mk1, and yells out 'vw sucks'. it gets irratating. he was once a vw enthusiicst. 
the bmw packs 300hp and 300lbs torque? i wanna take him down with my mk1, but i have spent too much money on the 16v 1.8l engine with the carb setup, and i am sure that, power to weight ratio plays a roll in this. bmw = 3300lbs? mk1 = 2000lbs?
that is were the idea of turboing a carb setup came to be. 
any help would be great


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## B4S (Apr 16, 2003)

*FV-QR*

If you're hell-bent (and I like that







), here are a couple forums that could provide better carb/turbo info than the vortex







.
http://www.theturboforums.com/...=13.0
http://www.shoptalkforums.com/...e0ad3
The second link is for an aircooled turbo forum, so it's not necessarily based around carbed turbo setups, but the Aircooled crowd has been turboing stuff with carbs for a LOOOOOOOOOOOOOONG time and have it down.


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## lamarchambers (Dec 25, 2004)

*Re: 16v 1.8 carbs... with a turbo??? (aaronl307)*

you live where turbos are king, CA. draw thru turbos work. mine runs 6.50 in the 1/8 mile and it's one of the slow ones. as for turbo lag, it's man made. i have {0} turbo lag. either draw thru or blow thru, you won't be sorry. i use a holley 750 double pumper with boost referance power valve for extra fuel. just my 2C worth.


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## aaronl307 (Apr 26, 2009)

*Re: 16v 1.8 carbs... with a turbo??? (lamarchambers)*

after reading on the forums, and checking websites, fuel injection would be the easiest to use with a turbo setup. what i have now is a 1.8l 16v long block (sitting on a radio flyer wagon), i have the weber dcoe kit, sitting in my room. 
on cb performance's website they sell a "carb conversion kit", i wonder if their throttle body would bolt up to the dcoe manifold? here is the link.

http://www.cbperformance.com/c...D=281
thanks guys


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## B4S (Apr 16, 2003)

*FV-QR*

Nope, those TBs are replacements for IDF or DRLA downdrafts, not weber sidedrafts.


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## xdawgedawg (Apr 12, 2009)

*Re: FV-QR (B4S)*

i just nutted myself.............








check this out...
http://www.twminduction.com/Th....html


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