K24 vs RS2 Spool-up. RS2 Results is now turbo comparison...

[Tony Tuzzolino]

Robert,

Were either of your cars MAC14/k24's?  I've got one with a 1.8 bar chip which
theoretically should give a bit more margin for safety than just the
resistor/schrapknobben mod on a stock ecu at 2 or 2.2 bar when it is combined
with them, right?

Now, I just have three problems as I see it:

1.  Detonation.  8.4:1 compression may need to be reduced.  I was thinking of
stacking 2 head gaskets and using an adjustable timing gear (or offset
woodruff key.)  Gary wants to use H2O injection, which is intriguing (sp?),
but I wonder about packaging and maintenance of yet another system on this
car, and what happens if it stops working at 2.5 bar?

2.  The k24.  No one thinks it will push that much air at the top end without
dying a hot, horrible death.  I know that the rs2 is the berries for this, but
what about a k26 for a cheaper solution?  I liked Gary's idea of bolting the
hot side of a k26 onto my k24.  What does one need to know about doing this?
Is it possible?

3.  The resistor.  I need to know what resistance to use to allow my chipped
computer to see 1.8 bar (while I'm running 2.2.) Anyone know how to figure
this out?

Let's keep this conversation going.  Tell me where I'm wrong.  I think we're
onto something...
Let's build some 280+ hp sleepers on the cheap...

Tony



On Mon, 5 Aug 2002 17:48:20 -0700 auditude at cox.net wrote:

On 5 Aug 2002 at 19:25, Robert Myers wrote:
>
> At 06:42 PM 8/5/02, auditude at cox.net wrote:
> >
> >I thought a Schrapnelknobben was different than a simple bleed, in that it
> >applied regulated boost pressure to the upper WG chamber.
> >
> >Is a Schrapnelknobben (the original Timmerman mod) a bleed, or an upper WG
> >mod, or either?
>
> You are exactly correct.  The schrapnelknob consists of an inexpensive
> surplus gas pressure regulator which admits a specific (but adjustable)
> maximum pressure into the top of the wastegate.  The pressure is derived by
> tapping into the pressurized intake system.  This acts as if the wastegate
> spring is stiffer actually than it is.  Use of the schrapnelknob by itself
> in the older systems for which it was used will lead to the dreaded
> overboost cutout.  Paul Timmerman also devised a resistor network
> arrangement which essentially told the ECU a lie.  The lie was that the
> pressure is lower than it actually is.  This allowed greatly increased
> boost levels (such as 18 psig vs. 4 or 5 psig) and significantly increased
> performance as a result.  It also could lead to overly lean mixtures at
> elevated boost levels which could result in overly high combustion
> temperatures and burnt valves and pistons.
>
> BTW, the lie prevented the in-dash boost gauge from indicating true boost
> pressure since the pressure transducer output was electrically clamped at a
> lower than actual value and the gauge displayed this artificial value
> rather than the true one.
>
> Essentially, the schrapnelknob plus the resistor network provided the
> boost/performance gains of a modern chip mod but did so on the cheap and
> without some of the fuel mixture safeguards which are more desirable.
>
> I used Paul's schrapnelknob along with an alternative zener/resistor mod on
> two '89 200 tq's for over 60K miles each.  I saw no indication of damage
> from lean mixtures.  YMMV.  BTW, it was a FUN ride.  :-)  AFAIK, one of
> these cars is still being run by another list member.  I have no idea of
> the current mileage or if these mods are still in effect.

Thanks Robert,

That's what I thought I'd remembered.  So Gary's post could've been (not
"trying" to pick at nits, I
promise!):

> Nobody does a pure electronic solution that I know of (i.e., chip and
> transducer, which probably isn't feasible anyway), so I'll either do
> the resistor fakey + big spring and/or schrapnel knob (resistor changes the
> resistance the computer sees, making it think the boost is lower than
> it is), bleeder (device that reduces the air pressure the WG/computer
> sees), or a combo of all three.

Actually, can a bleeder reduce the pressure the ECU sees?  I guess it could.
Would you then need two
bleeders, one for the WG and one for the ECU?  Curious about that now.  I
mean, a lower WG chamber
bleed isn't going to bleed off enough pressure so that the ECU will see the
lesser pressure.

Damn that looks like another nit, sorry.  Just making sure I understand.
Well, if decisions are being and
all...

I think the shrapnelknob mod is easier on the WG diaphragm than a big spring,
since pressure is
equalized.

Ken