MAFs

[Matt Henson]

Hi Rod,
Thanks for the information.  I used to have a 951
also.  The pipe length between the MAF and the turbo
is pretty short - like 1 foot, right?  I guess it
takes more pipe length to have a laminer flow back at
the MAF.  Have you considered adding any air
straightening devices to your pipe?  Maybe some fins
or something?  I would suspect that your problem is
solvable without changing the basic architecture of
your system.

Certainly a blow through MAF would have major
advantages.  But, if it can't get at least 50k
reliability then it's not for me.

I think that in cases like this it's best to borrow
what the OEMs have done.  I always ask myself "What
would Porsche do?"  In this case, on their MAF-based
systems, they put it before the turbo.  Does any OEM
use blow through?

Regards,
Matt

--- Rodney_L_Wiggins at keybank.com wrote:
> Actually there is a fair amount of turbulence ahead
> of
> the turbo on a suck through system. In my
> application, I
>  have seen the signal from the (Ford) MAF rise from
> 1.2v
>  to 2.5 at constant load and constant throttle
> position
> in response to turbo RPM at an 80mph cruize. Makes
> for
> very annoying highway driving (WOT is fine, but the
> local
>  police frown on WOT as highway cruize policy).
> Blow-through also allows the blow-off vale to be
> vented to atmosphere.  Yesterday, I spoke at length
> with
> the engineer at Pro-Flow pro-M about pros and cons
> of blow
>  through and whether either can give consistent
> readings
> with a ford MAF on a turbo system. (Ford MAFs is a
> huge
> portion of their business) He was very knowlegable
> but not
>  terribly optomistic--even though he could have sold
> me
> some parts by being less honest. He seemed more
> concerned
>  about any bends in the plumbing than the spinning
> air
> from a turbo. But his turbo experience was minimal.
> They
>  are working on some huge, chambered design that is
> supposed to be immune to turbulence (not sure at
> what
> cost in terms of flow restriction) but it is still
> too
>  expensive to market $600+.
> Perhaps I do need to convert to MAP. Anyone here
> have
> any experience with the Link AFM?
> 
> I have also considered a throttle-position based
> voltage
>  clamp to limit the turbulence-induced enrichment at
> lower
>  rpms. Not an elegant solution, but relatively easy.
> 
> Rod
> 86 944 Turbo.
> 


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