Carbs and a turbo
Discussion
Arfter building a zetec 16v turbo and spending a bucket load having it mapped and set up with autronic managment i thought for the next trick im going to build another on Blow through carbs. Reserch staeted and found out that dellorto turbo carbs is what i need so have sorced some and the fun begins....Has any one had anything to do with this kind of set up if so any tips or threads/forums to look at ??????
Dellortos might be ideal, but finding a set, and finding jets etc wont be easy.
Quite a few carbs can be used for turbocharging in a blow through setup.
SU's are very good. Ive also used a 600 Holley DP, 38DGAS, 32/36 twin choke, and normal pair of 40's Weber sidedraughts.
But I'd never choose a carb over efi again. There are far too many options for mappable fuel injection systems, at varying costs, to make carbs worth the hassle.
Quite a few carbs can be used for turbocharging in a blow through setup.
SU's are very good. Ive also used a 600 Holley DP, 38DGAS, 32/36 twin choke, and normal pair of 40's Weber sidedraughts.
But I'd never choose a carb over efi again. There are far too many options for mappable fuel injection systems, at varying costs, to make carbs worth the hassle.
jimmyfish said:
Arfter building a zetec 16v turbo and spending a bucket load having it mapped and set up with autronic managment i thought for the next trick im going to build another on Blow through carbs. Reserch staeted and found out that dellorto turbo carbs is what i need so have sorced some and the fun begins....Has any one had anything to do with this kind of set up if so any tips or threads/forums to look at ??????
Friend of mine has megasquirted his zetec engine, even made a little adapter board so you can directly interchange with the old ECU. Total cost including a wide band lambda setup around £300 from memory. Mapping is done by bribing your mate with beer to press the keys on the laptop whilst you drive around. (well that's how we do it, Gets a bit hairy in a 5L tvr trying to map WOT though). Really cant see the point of Carbs when you can have fully a mapable system for so little, esp for a boosted app.
Usually they are quite hard to set up to give decent economy, and good power with no flatspots or hesitations.
If you intend using a pair do Dellortos on a 1600cc engine, I'd say you will have more problems, as the carbs will likely be far too big for the engine.
When blowing, smaller carbs work better than big ones. With big ones, air speed is too low, and it can be difficult getting the on, and off boost fuelling correct, as it wont draw fuel properly off boost.
If you intend using a pair do Dellortos on a 1600cc engine, I'd say you will have more problems, as the carbs will likely be far too big for the engine.
When blowing, smaller carbs work better than big ones. With big ones, air speed is too low, and it can be difficult getting the on, and off boost fuelling correct, as it wont draw fuel properly off boost.
...hence the superiority of the SU, see MR2Mike's post 
It does if you use a suck-through setup, as the evaporating fuel provides an intercooling effect. Not for a blow-through though.
chuntington101 said:
loads of people in the states stil run FI and carbs. they even say that it give more power thanks to the evaperating fuel!
It does if you use a suck-through setup, as the evaporating fuel provides an intercooling effect. Not for a blow-through though.
[quote=stevieturbo]Usually they are quite hard to set up to give decent economy, and good power with no flatspots or hesitations.
If you intend using a pair do Dellortos on a 1600cc engine, I'd say you will have more problems, as the carbs will likely be far too big for the engine.
Econemy isnt a problem as it is not my main car the engine is 2.0 16v zetec
the main reason is to get away from efi i know it is good but when it comes to power tuning its v expensive
if you need a set of larger injectors just kiss the pounds away on top u may require a larger fuel pump remap etc cost just mounts up thats with out the rolling road cost with the carb idea the inithal (sp) cost will be high (as is arftermarket managment.) but if more fuel is needed its only a set of jets required which are 50% plus cheaper than injectors. Its not all about doing some thing on the cheap its something diffrent and a diffrent approuch to a solution to a problem it is easy to go and spend 2k plus on managment and mapping.
If you intend using a pair do Dellortos on a 1600cc engine, I'd say you will have more problems, as the carbs will likely be far too big for the engine.
Econemy isnt a problem as it is not my main car the engine is 2.0 16v zetec
the main reason is to get away from efi i know it is good but when it comes to power tuning its v expensive
if you need a set of larger injectors just kiss the pounds away on top u may require a larger fuel pump remap etc cost just mounts up thats with out the rolling road cost with the carb idea the inithal (sp) cost will be high (as is arftermarket managment.) but if more fuel is needed its only a set of jets required which are 50% plus cheaper than injectors. Its not all about doing some thing on the cheap its something diffrent and a diffrent approuch to a solution to a problem it is easy to go and spend 2k plus on managment and mapping.
Megasquirt... circa £200 ???? Guessing as Ive never used it.
Injectors off ebay. £100 should buy you a suitable set.
Fuel pump. £100 will buy you a Walbro or Bosch capable of over 500bhp.
Mapping on a RR or dyno will be faster than trying to set up carbs.
efi doesnt have to be expensive these days.
I wonder how much has been paid for the carbs ? manifold ?, linkages ?
Now you also need an efi pump anyway and suitable fuel pressure regulator.
Then RR time to sort jetting, and chokes. EXPENSE if you need to replace chokes etc I imagine finding said items might be tricky too ? I honestly see the carb option as more expensive to get right. If I was doing a turbo conversion using a carb, I'd be trying to use 1 carburettor to simplify any jetting required. Something like 38DGAS would probably do.
How do you intend to control igntion on this engine ?
Injectors off ebay. £100 should buy you a suitable set.
Fuel pump. £100 will buy you a Walbro or Bosch capable of over 500bhp.
Mapping on a RR or dyno will be faster than trying to set up carbs.
efi doesnt have to be expensive these days.
I wonder how much has been paid for the carbs ? manifold ?, linkages ?
Now you also need an efi pump anyway and suitable fuel pressure regulator.
Then RR time to sort jetting, and chokes. EXPENSE if you need to replace chokes etc I imagine finding said items might be tricky too ? I honestly see the carb option as more expensive to get right. If I was doing a turbo conversion using a carb, I'd be trying to use 1 carburettor to simplify any jetting required. Something like 38DGAS would probably do.
How do you intend to control igntion on this engine ?
ignition will be a electronic dizzy. I purchesed the following : carbs inc a selection of 40 jets,emulsion tubes, chokes and compleate rebuild kit) linkage webro fuel pump and a fuel pressure regulator for 150 quid the in let manifold is going to be a further 90 quid the only thing i have to find is a plenum chamber this may have to be a one off but this is no problem as my uncle has his own machine shop this is only going to be an experiment just to see if it is viable the real plan is to turbo through a set of jenvey throttle bodys. Whith the reserch i have done over the last few months i have found that most carbs can only take around 3-4 psi of posetive boost im looking to run 9psi plus.I have once bought a set of injectors off e-bay paid 120 quid for a set of beige injectors for my fiesta rs turbo 3 of which were buggerd so i realy paid 120 quid for one injector some thing as critical as an injector i would never buy second hand again
jimmyfish said:
Whith the reserch i have done over the last few months i have found that most carbs can only take around 3-4 psi of posetive boost im looking to run 9psi plus.I have once bought a set of injectors off e-bay paid 120 quid for a set of beige injectors for my fiesta rs turbo 3 of which were buggerd so i realy paid 120 quid for one injector some thing as critical as an injector i would never buy second hand again
He seems to have been told that the boost limitation is with the carburettor. Not the engine. There was no boost limitations like that on any blow thru carb install Ive ever built. If there was, it would be waste of time.
As for injectors, even new ones are pretty cheap these days. Just some stuff, mostly relating to popular models are still silly prices. You could buy a set of LS1 injectors for buttons from the US, circa 300cc flow.
stevieturbo said:
[quote=jimmyfish]Whith the reserch i have done over the last few months i have found that most carbs can only take around 3-4 psi of posetive boost im looking to run 9psi plus.
He seems to have been told that the boost limitation is with the carburettor. Not the engine. There was no boost limitations like that on any blow thru carb install Ive ever built. If there was, it would be waste of time.
Wonder of he's thinking of needle seat pressures or splitting floats? Carbs are fine so long as there a boost pressure regulator. My holley was boosted to 9 psi, worked well.
Boosted.
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