turbo'd alfas??

[knighty]

Was having a catch up with a buddy here who's been modding a 242gt Volvo with some amusing success

here's an example of his 1500od kg 2.1l car in action (sorry for the non alfa link)

which got me wondering, what's been done with early 2l alfa mills and turbo's?


long story short, I'm toying with a 2l as a daily/toy as a similar bit of friendly competition.

Thinking turbo, draw through carb, water meth inj on a switch at about 6lb boost


what's been done??

[aggie57]

Been done lots and lots of times.  Most interesting recent thread:

http://www.alfabb.com/bb/forums/engine-conversions/264169-alfa-supercharged-turbocharged-phase-3-700hp.html?highlight=buzzed

[Darryl]

George Brook has been running a Turbo 116 GTV in Hill Climbs etc - see this thread http://www.alfaclubvic.org.au/forum/index.php?topic=10793.0 and of course the Beninca's have started running a Turbo 116 GTV in Sports Sedans again... It's a pretty impressive bit of work... Corners a bit better than the Volvo

[Mick A]

George Brook has been running a Turbo 116 GTV in Hill Climbs etc - see this thread http://www.alfaclubvic.org.au/forum/index.php?topic=10793.0 and of course the Beninca's have started running a Turbo 116 GTV in Sports Sedans again... It's a pretty impressive bit of work... Corners a bit better than the Volvo

The Benicna car is not turbocharged.

[festy]

what's been done with early 2l alfa mills and turbo's?
long story short, I'm toying with a 2l as a daily/toy as a similar bit of friendly competition.
Thinking turbo, draw through carb, water meth inj on a switch at about 6lb boost

If you're going to use carbs, wouldn't blow through be a better (safer) option? I assume you'd fit an intercooler of some form?


I'm still a while off completing mine -  but the path I'm following is low boost with std compression, EFI, E85, and a bunch of electronics like knock retard, boost control etc to try and prolong the engine's life a bit.
It's a low priority project and I'm making the parts myself (hardware and software) so no idea when it will be finished but the list of jobs is slowly getting smaller....

[Darryl]

The Benicna car is not turbocharged.

Ah - ok - even more impressive then - what have they done to that engine? I guess I just need to wait until I could be utterly confused (between believing tv commentators and possibly having had a glass or 2 of red before watching the race). Sorry about OT for OP.

Ah - ok - I would *swear* the tv said it was all alfa, and I just assumed some evo of the old turbo but If I do my homework it turns out to be 300hp from a nissan xtrail - now that is a scary image....

[Darryl]

what's been done with early 2l alfa mills and turbo's?
long story short, I'm toying with a 2l as a daily/toy as a similar bit of friendly competition.
Thinking turbo, draw through carb, water meth inj on a switch at about 6lb boost

If you're going to use carbs, wouldn't blow through be a better (safer) option? I assume you'd fit an intercooler of some form?

In theory (yeah I know) a draw through carb just sees a bigger NA engine, the air temp, density is all independent of boost so in principle it should "just work" tune wise unlike blow through which is a pita to get working in transition (or anywhere really - take your pick but usually you pick not lean on boost

[Neil Choi]

The Benicna car is not turbocharged.

Ah - ok - even more impressive then - what have they done to that engine? I guess I just need to wait until I could be utterly confused (between believing tv commentators and possibly having had a glass or 2 of red before watching the race). Sorry about OT for OP.

Ah - ok - I would *swear* the tv said it was all alfa, and I just assumed some evo of the old turbo but If I do my homework it turns out to be 300hp from a nissan xtrail - now that is a scary image....

Yes, the base unit is a Nissan XTrail motor leant a bit on its side.  Other than a few bits of the pillars, it only looks like an Alfa but there isn't anything wrong with that, it is Sport Sedan racing.


The car is built with bits of coke cans and real estate sign material etc but it goes fast.  And because they can and have the know-how.

[festy]

If you're going to use carbs, wouldn't blow through be a better (safer) option? I assume you'd fit an intercooler of some form?

In theory (yeah I know) a draw through carb just sees a bigger NA engine, the air temp, density is all independent of boost so in principle it should "just work" tune wise unlike blow through which is a pita to get working in transition (or anywhere really - take your pick but usually you pick not lean on boost

By 'safe' I was referring to personal safety, not a safe level of tune - if an inlet valve failed to fully close before ignition for some reason, an intercooler full of pressurised air/fuel mix could be an eye opening experience 

[knighty]

thanks for the great replies gang!

following the KISS principle this time

it's amazing just how many people look straight past the draw through, how many toys have you seen that have been over engineered and end up being a complete and utter pain in the ring

there's a few blokes down here, that use a turbo/draw through (holden strata kit) with a simple water methanol spray using a tank that pressurises equivalent to boost pressure and turns on at around 6lb

two lc/j toranas with 186-202 and the 2.1l Volvo, all road registered and driven, and are holding quarter mile times from 13.2 to 11 seconds flat,

here's another

like I said, simplicity itself

[Duk]

In theory (yeah I know) a draw through carb just sees a bigger NA engine, the air temp, density is all independent of boost so in principle it should "just work" tune wise unlike blow through which is a pita to get working in transition (or anywhere really - take your pick but usually you pick not lean on boost

While this is your project to do as you will, your interpretation of what happens is, um, well, wrong.
A draw thru carby and a blow thru carby behave in the exact same way and have the exact same tuning limitations that carbies always have.
The carby (s) have to supply an amount of fuel for a given mass of air. That mass of air doesn't change. If the turbo is pumping in 10kg of air a minute (about enough to make 200hp), then it doesn't matter where the carby is, it still has to supply the right amount of fuel.
If the engine idles and makes, say 5hp, then the carby needs to be able to deal with a 195hp power change.
Case in point, plenty of people who have turbo'd Nissans have moved the (mass) air flow meter from in front of the turbo to after the intercooler. While there may be some tuning requirements, the behavior and resolution of the air flow meter doesn't change. It can't measure more and it can't measure less.
What is important is making sure that there is the correct pressure differential between the venturies and the float chamber. And that, along with the requirements for the carby to be able to hold in boost pressure at its shaft seals, have a fuel delivery system that maintains a set pressure above the pressure in the float chamber, plus keep its floats the same shape, are the 'technical' down side to blow thru carby turbo set ups and why people think blow thru set ups are easier.
The down side of draw thru carby set ups are plenty and they are more significant, especially for a daily driver. The fuel has a long way to travel and at low loads and low speeds, the fuel has a bad habit of falling out of the air stream and collecting on internal surfaces. This is make worse by using porely designed inlet manifolds and plumbing with overly smooth internal surfaces. Cold weather will make it worse again. The fix is to run the engine richer, so 'by by' respectable cruise fuel economy.
The turbo also has to be able to deal with pressure below atmospheric pressure (vacuum) at its compressor inlet. Not all turbos have seals that will tolerate that.
As Festy mentioned, with a blow thru set up you get the huge plus of being able to use an intercooler. Plus the fuel travels a much shorter distance and transient throttle response is better.

So a blow thru set up would cost more to do properly but will reduce your compromises.
A draw thu set up will be cheaper to set up but will have more compromises that can't be dealt with (drivability/throttle response, cruise fuel economy).
And if push comes to shove, a blow thru set up will make more power by being able to use an intercooler.

Incidentally, the drag strip is a very poor measure of success for anything other than drag racing. There are simply to few real world operating behaviors experienced in drag racing. That's why a certain brand of cheap programmable computers has been able to have its success for so long, they sold their product based on peoples drag strip success, but in the real world they are crap compared to what else is available for the same/similar dollars.

[Darryl]

In theory (yeah I know) a draw through carb just sees a bigger NA engine, the air temp, density is all independent of boost so in principle it should "just work" tune wise unlike blow through which is a pita to get working in transition (or anywhere really - take your pick but usually you pick not lean on boost

While this is your project to do as you will, your interpretation of what happens is, um, well, wrong.
A draw thru carby and a blow thru carby behave in the exact same way and have the exact same tuning limitations that carbies always have.
The carby (s) have to supply an amount of fuel for a given mass of air. That mass of air doesn't change. If the turbo is pumping in 10kg of air a minute (about enough to make 200hp), then it doesn't matter where the carby is, it still has to supply the right amount of fuel.
If the engine idles and makes, say 5hp, then the carby needs to be able to deal with a 195hp power change.
Case in point, plenty of people who have turbo'd Nissans have moved the (mass) air flow meter from in front of the turbo to after the intercooler. While there may be some tuning requirements, the behavior and resolution of the air flow meter doesn't change. It can't measure more and it can't measure less.

It was actually me that said that (the draw through vs blow through thing) and I am not wrong (for once). You are also not wrong until you assume you can equate a mass flow meter and a carburettor. Mass flow sensors have their own imperfections but a real one is still much better compensated than a carb. In any case, as we are all agreeing in EFI the mass flow sensor is one input into the efi system, having engine rpm as well gives you the ability to tune differently for same power produced at high boost low rpm and vice versa for example. EFI is clearly better than either carb location....

The problem with carbs in blow through is this:

When you flow a the same mass of air through a venturi but at a higher pressure, lower velocity, and even though the carb is pressurised, the carb does not deliver the same amount of fuel as it would in the lower pressure, higher velocity case. With the carb stuck out in front (draw through) it sees exactly the same density and velocity whether its low rpm, high boost or high rpm, low boost, if both of these points have the same mass flow.

The amount of fuel drawn in by the carb is due to the pressure differential in the throat which is proportional to density times velocity squared. The mass flow rate is of course density times velocity and that is what you really want to drive fuel delivery off....

Anyone who is familiar with flying carburettored aircraft knows this - the turbo is like flying below sea level, but less fatal.

It is all academic if, as you also point out, the car is being tuned for one particular line through the overall operating range of the engine (ie for a drag run). It is  making blow through carbs have good driveability that is hard/fighting with the physics. Note I'm not suggesting draw through is ideal either - its is just "right" from a pure flow to fuel metering perspective.

Given an alfa 2L vehicle as a starting point it is pretty clear blow through conversion is the most obvious way to make it work with boost, the amenability to intercooling is nice, but don't dismiss the water/meth injection as a very effective and simple approach if you don't have to figure out how to meter it across full load range etc (ie it is good for drag). We are possibly in violent agreement that for drag it probably doesn't matter either way... Taking the dellortos off and sticking them out front as a 4 barrel would be different at least.... And I still claim it would be easier to make it drivable on the way to the track....

PS Thanks for the springs...

[Duk]

Firstly, apporogies for the mis-quote. Certainly not an intention.

Your comments about carbies and air density are interesting. I'll be a pig headed prick and stick to my preferred interpretation of how carbies and turbos should go together, citing more car manufacturers with decent reputations have done blow thru, but I've probably put my neck on the chopping block there.................... 
At the end of the day, I hate carbies, so I'll leave it at that.

As for water injection. For those who haven't, buy Greg Gordon's book on supercharging. He spells it out in an easy to understand way.
Water injection equals knock resistance. If that can allow the engine to make more power by taking advantage of more aggressive tuning (leaner AFRs and/or more advanced ignition timing), while keeping the engine in 1 piece, then great. But the water (or water/methanol) itself didn't give the extra power directly. Keep in mind that while a water injection equipped engine will obviously show lower induction temperatures, the inducted air isn't actually any more dense. IE: It has no more (or only a very few more) air molecules. The air is now more humid and the water takes up available air (and so oxygen molecule) space.

Intercoolers give power advantages by cooling the air (as everybody knows), causing it to become more dense and allowing more fuel to be burnt for a given induction stroke. The cooler air also helps give some knock headroom. BUT(!!!) a good intercooler can't give the knock resistance that water injection can.
The real answer is to have BOTH.