Intake manifold construction, intercoolers

[Kevin _]

>Higher rpm, OK, how high are you talking about.  The thread started with
>street cars, are you still working the street or moving into the race field
>I'd hardly call 250d at .050 as a street engine.

I'm talking 8000-9500 rpm max.  Its very common in the I4 world.  Look at 
specs on the larger, high rpm lobes of the VTEC cams and I'm sure toyota 
stuff also - its in the 225-230 degree range at 0.050" from the factory.  
Now 270d at 0.039" is huge through if that cam is being used at low rpm's.  
In my former street car (now race only pretty much), I have cams that are 
234/236 at 0.050" and with a well tuned EFI setup its completely smooth down 
low, it even idles evenly at 1000rpm, it just doesn't have much vacuum 
(~8-10" at idle) and doesn't make any power before 5000rpm.

> > >If atmospheric pressure doubled, I don't think it will make an
>appreciable
> > >difference in the way an intake manifold worked.  The whole question
>still
> > >seems inconsequential to me, since by tuning an intake you are trying 
>to
> > >increase intake air pressure by a small number of pascals.
> > Have you ever datalogged and seen pressure pulses at the back of a 
>valve?
> > When its all tuned right with the proper sized runners it can be over 
>20%
> > beyond atmospheric pressure during valve closing.  We're certainly not
> > talking single Pascals here.
>
>At the back of the valve, OK, and how fast does that decay as you move back
>from there?

Why would you care at all what the pressure is anywhere in the intake tract 
besides the back of the valve during valve closing?  That's the only place 
flow is occurring into the cylinder so it could be -10psi 4" up the runner 
and it'd make no difference, as long as there is good pressure behind the 
valve.

> > I have to completely disagree on the turbo issue here.  Normally with a
> > turbo setup you have a huge pressure swing from before spoolup, during
> > spoolup, then maintain a good pressure differential for ~3000 rpm, then
>HUGE
> > PRESSURE INCREASES IN THE EXHAUST.  You will see drastic increases in
> > exhaust pressure, I've measured as much as 60psi for 23psi in the 
>intake.
>
>That has to be about the worlds worst matching of turbo to engine.

Yeah, I guess that's what I get for buying and off-the-shelf turbo that's 
made in mass quantities and sold for my car.  Its got a 54 trim compressor 
wheel, which should flow about 550hp max and be very efficient in the 450hp 
range.  Because of the small turbine side that was coupled to this wheel, it 
completely chokes itself off at just barely over 400hp.  FYI, its a 
Frankenstein stage 3 in the dsm world.

> > BTW - Bruce said he was looking for 'new' stuff in engines.  Check out 
>F1
> > stuff before you call everything old and pushrods good.  Approximately
> > 300hp/liter naturally aspirated on gasoline (yes, I do use that term
> > loosely) and revving to near 20k rpm isn't trivial.
>
>To whom?
>I haven't seen any of that wizz bang technology filtering to anything on 
>the
>street yet.  They still have reached any level of performance that can't be
>done with engines that would have transferable technology to the street.
>The rules in F1 are just a game anymore to see who can spend the most for
>something that can win.
>Bruce

There's a 5-10 year lag on all that good stuff.  But there are TONS of 
things that have filtered down from F1.  F1 was the first to use a wideband 
UEGO in a racing condition (Honda in particular), last time I checked that 
made it down to several of their production cars.  More subtly and 
importantly, there is a gigantic wealth of knowledge about vehicle dynamics 
gained from motorsports.  Learning how to do a good traction control system 
and a good ABS system (although I still argue the tuning of many production 
ones) starts best in the motorsports arena.  If its a slight competitive 
advantage in a street car, its really tough for a manufacturer to justify a 
big budget for it.  If it helps winning races so your team can keep its 
sponsor, you're going to make it a priority or go hungry.  The racing world, 
obviously, is much, much more Darwinistic than development/engineering 
staffs are at large auto makers.

Just my $0.02,

Kevin

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp

----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org