>1999 Solo II Rules, Section 14.10, Paragraph C. Last couple of
>sentences.
>
>Turbochargers may not be changed or modified. No changes are allowed to
>waste gates, pressure sensors or their location, and to other
>turbocharger or supercharger boost limiting systems. This allowance does
>not permit changes to blow-off (pop-off) valves. Devices know as "fuel
>cut defensers", and any modificationswhich alter or defeat the fuel
>cutoff when it is activated by boost level, are not permitted.
>
>Question, this would seem to make moadifications like Abersold's Supra
>had illegal. Am I reading this correctly?I know very little about turbos
>and systems, and that is more than I want to know. I don't have Jamie's
>address or would cc him as well.
>
>Rob
Rob,
As I would intrepret this rule, they are refering to a fuel cut that is
specifically activated by a set manifold pressure. In most newer turbo
cars (including the Talon and Supra), the engine control unit (ECU) gets
it's airflow information from a Mass Air Flow (MAF) sensor, whereas earlier
cars used a Manifold Absolute Pressure (MAP) sensor. An ECU using a MAF
sensor generally has no direct manifold pressure input, and computes fuel
delivery solely on the flow of air. It must then also compute the fuel cut
based on mass air flow, rather than boost pressure. The Talon, for
example, has a boost pressure gauge that is run by the ECU. However, the
reading is mearly a guess at the manifold pressure, and once any portion of
the intake is modified, it becomes terribly inaccurate. The ECU really has
no good idea what the boost pressure is in a modified car. The Talon's
fuel cut is solely based on exceeding a pre-set air flow limit. This
information is from our master DSM ECU hacker, Todd Day.
Older cars using a MAP sensor probably have their fuel cut based on
exceeding a certain boost pressure. My old Chrysler 2.2L Turbo had one
like that, and I think the older Audis are that way also.
I would say that a MAF-equipped car like the Supra would have it's fuel cut
based on air flow and not boost pressure. To make sure, you would have to
contact either Toyota or somebody familiar with hacking Toyota ECU code.
The place who modified Abersold's ECU would have that information. The
factory service manual should say if it has a secondary manifold pressure
sensor, but if it's like the one on the Talon, it's a differential pressure
sensor and not absolute pressure, so will not read pressures above
atmospheric. The service manual should cover that. I would say that
removing a fuel cut based on air flow would be legal under the first
sentence of 14.10.C "Carburetors, fuel injection, intercoolers and intake
manifolds are unrestricted."
Mac Crossett
'96 Eagle Talon TSi AWD #49ESP
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