ok, i agree with u on this.
though i will use the system i described above on A12 when i start the project. as there r no MAP Sensors or Air Flow Sensor Plates in an A12
barpk

please make sure you take some pics for all of us at Datsun1200.com to take a look at!

I am very keen to see this setup and see how well it actually works!

Just to add my extra 2 cents!
A map sensor doesn't get affected by this!
And yes air flow sensor will not read the air if it is released to atmosphere but all it will do is cause the engine to run rich for a few seconds after each gear change!

That is all!
Cheers Steve!

[quote="Dragongoose"]Sorry guys, I still prefer the suck through carby setup...the standard mechanical fuel pump which should handle it real well. Power with a t25 garrett should be around 180 Hp at the fly wheel on conservative boost say 8-12 pounds...don't need a Blow off valve as there is no throttle body in the way. So simple effective and practical, and it looks real cool seeing the carbys hanging off the turbo inlet. Better than looking at a box.

Mate I respect your feelings

As for being simple to change back! Maybe
But what makes you think any other setup would be any different? If you have an exhaust pipe adapter there is no difference!
maybe my setup is even quicker to change back! ( but really why would you want to?)
My carbie is in the right place to start with! so it is only the turbo you need to take off!
and put an aircleaner instead of the intercooler pipes!
The carbie is set up to run good at no boost or with boost! Nothing needs to be done here!
And If all you are after is a car that runs no boost in the week! just disonnect the wastegate actuator and this is what you will have! Nothing else is required!

But in the end to each his own!
Think about it and tell me now if 45 mins is better then 5 mins!
You too could just disconnect the actuator but then you still have to suck the fuel through the turbo all the way to the manifold!
Just though I would point this out!

But to each his own!

yeah, your system would be quicker to change. the point I was making was that with a draw through system using a downdraught Weber instead of a better sidedraught Weber or SU, and the standard inlet manifold instead of a better fabricated item would give you that option albeit at the expense of a bit of power. It wasn't supposed to be a benefit of draw through over blow through, but I can see how you interpreted it that way. let's not make this thread any more agro than it already is

45 minutes is an outside estimate. I could put up with that. Some of the racetracks I compete at are 2.5 hours drive away and undoing a couple of pipes and moving the carb is a small price to pay to avoid having to tow the car home if you happen to blow the turbo at one of those events.

Quote: how about you try that and see what happens! I think you're in for a surprise...

as for your suggestion of sucking the fuel through the turbo when running in aspirated form, I reckon it would be very sluggish and horrible to drive. You would also have problems with pooling of fuel in the compressor housing which would't be a very good idea when you connect it back up - liquids don't compress very well

Mate there is no agro here just saying my point of view!

As for this suprise you say of!
I have had to do this as intercooler hoses have burst on me a few times and the noise is very annoying if you have to drive for an hour before you are somewhere to fix it!
Also the car will run like a dog with such a big exhaust no doubt! but if the exhaust has to go through the wastegate first this is causing a bit of back pressure whick would be better than just going straight to a big exhaust!
Also only the carbies secondaries are larger! yes this will cause the car to run rich but only when the secondaries are open! so you just have to take off slower so the car doesn't bog down! then once you are going you won't be bothered as much ( yes I agree it would still run like ####! )
But even changing one jet ( 5 mins ) isn't to much to ask!
Your webber would still have the same dramas!

As for fuel pooling in the turbo! this is one of my points exactly!

One thing I should point out is I never said the car would be the best to drive!
I did say why would you bother doing this!
And you gave your reasons and I acept them!
( Just don't agree with doing it all just so on a Saturday you can have a turbo car!

Not Agro just saying the facts!
Steve

the "saturday night special" comment was very tongue in cheek...

ahh I see what you mean now, dissconnect the wastegate actuator ROD so that the wastegate is free to open all the time. Rather than disconnecting the wastegate actuator from the compressor housing!

Fuel pooling is not a problem when the compressor wheel is actually being driven. You may get some wetting of the manifolding after the turbo, but I never saw any evidence of pooling in the compressor housing on my motor.

Back to the actual point of blow through vs draw through...
Personally, I prefer the simpler and cheaper draw through system. And from an engineering perspective, the best solution is the one that does the job effectively with the least complexity and minimal number of additional components. Not only does the draw through system have fewer components and less unnecesary complexity, it also does not suffer from the limitations of the blow through system. Extra capability from a cheaper simpler system - No contest really.

Much respect for what you say!

No Doubt each setup has its advantages and disadvantages!

You say " No contest"
I say " to each their own! "

I don't understand these limitations you mention of either?

And as for no contest! OK if you are not after maximum performance but if any of use were after this we wouldn't be messing with carbies!
We would go EFI!

not intended as a personal attack phunkdokta. I'm sure I haven't upset you have I? I'm flatter if I did, cause barpk couldn't manage it --just kidding-- All of what you have said in here is right, and you obviously know what you're doing. I just think there's a better way. Don't close your mind to the possibility.

You have described the limitations in detail yourself; amount of boost limited by the amout of fuel pressure you can achieve and control, and also limited by what the carb or box seals and float can withstand.

The real drawback of the draw through carby system is that you can't really intercool it. Most of the unlimited category speedboats run drawthrough carby turbo V8's with intercoolers, but it obviously only takes one backfire to turn them into a bomb. But there are ways around that, up to a point.

true EFI is the ultimate for performance, driveability, fuel economy and reliability. But for most people like you and me, the cost of the ECU and tuning is still prohibitive. I'm still after the maximum performance I get get out of what I can afford to do.

Besides, it's much more fun doing it all yourself. I'm sure you and I are really on the same wavelength on that score. Hell, the more fast little 1200's out there the better! "To each their own" is fine by me, just offering my perspective.

Harry