<VV> Draw through Turbo's

[Hugo Miller]

That's interesting. That's another combination I have never seen - by 
the time fuel injection came in, the trend had switched from 
superchargers to turbochargers, presumably with the introduction of new 
seal materials that could withtand the higher temps. What kind of 
supercharger did you use and where did you put it? I was thinking of 
doing something similar myself.

On 2020-03-23 03:55, mmccrae6 at cox.net wrote:
> I have a supercharged fuel injected '66 Monza that works quite well, 
> thank
> you!
>
> -----Original Message-----
> From: VirtualVairs <virtualvairs-bounces at corvair.org> On Behalf Of 
> Hugo
> Miller via VirtualVairs
> Sent: Sunday, March 22, 2020 8:51 PM
> To: virtualvairs at corvair.org
> Subject: Re: <VV> Draw through Turbo's
>
> Yes, superchargers always suck (as far as I know!). The Spyder was 
> the first
> turbo I ever saw that sucked. In fact it's the only one I ever saw, 
> though I
> understand there are others out there, but not in the UK I'm fairly 
> certain.
>
> On 2020-03-23 02:49, FrankDuVal via VirtualVairs wrote:
>> My 1938 Supercharged Graham Model 97 (stock) draws through the 
>> Marvel
>> Schebler carburetor.
>>
>> Frank DuVal
>>
>> On 3/22/2020 2:31 PM, kevin nash via VirtualVairs wrote:
>>>
>>>   Hugo- no the Spyder is not unique to use a draw through 
>>> carburetor
>>> set-up!! not even close! In the early days of turbocharging, it was
>>> way more common to use a draw through arrangement on carbureted
>>> turbo's... the Olds jetfire, the late 70's buick grand national(?)
>>> numerous japanese makes in the early 80's also did it this way. One
>>> of the quirks of this set-up is the compressor has to have a 
>>> special
>>> seal on it that will prevent lubricating oil from getting sucked 
>>> into
>>> the intake when the throttle is closed, and because this draw 
>>> through
>>> configuration used to be so common, Garret turbo's in particular, 
>>> can
>>> be had with this type of seal. The advantage of that seal is that 
>>> it
>>> is tough, can be used on anything blow through or not, the
>>> disadvantage is that it has a bit more drag.
>>> Although draw throughs would "seem" to not be the best way to turbo
>>> an engine, they do have some neat advantages... harder (nearly
>>> impossible) to send one into a surge, at least for the same
>>> conditions this usually happens on a blow through. Draw throughs 
>>> tend
>>> to run cooler at part throttle/light loads than blow throughs do. 
>>> It
>>> is the easiest, simplest way to get a carb to work, as the carb is
>>> always sensing vacuum. Theres no weird airflow changes being caused
>>> by blade angle on draw throughs either... I've seen a couple of
>>> youtube video's that test airflow variations to individual 
>>> cylinders
>>> at various blade angles, and it is pretty amazing as to how large
>>> these variations can be. One test shows some cylinders down 50% on
>>> airflow compared to another at part throttle, and basically no
>>> variation at wide open throttle!! With blow throughs, if the
>>> butterfly is big enough to never be a significant restriction at 
>>> wide
>>> open throttle and full boost, it is also big enough to cause
>>> significan
>> t
>>>   drivability problems out of boost, but on a draw though, they can
>>> be sized large enough to never be a restriction (if using EFI) and
>>> not have any drivability issues at all.
>>> Carbed blow throughs tend to have massive flow losses even when the
>>> carb is sized for the engine... one account that I read about, a 
>>> guy
>>> bothered to test the manifold pressure at full boost before and 
>>> after
>>> the carb... he was getting 28 psi before the carb, and 20psi 
>>> after!!
>>> Kevin Nash
>>> Draw through EFI daily driver, max boost tested=22psi
>>
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