[Supras] 57 trim driveability

[Khalid Almufti]

Hi Bernie,
    I was wondering if the installation of the larger intercooler+hardpipes did anything to resolve the issue of losing performance?  IIRC, what motivated the install was the "losing performance" after repeated runs discussion.  It might not be possible to test for performance loss in these cold temperatures, but as the weather worms up, I'd be very interested in your test results of repeated 3rd gear runs (of course, don't get a ticket in the process, and if in doubt, save it to the race track).
 
Regards,
/Khalid 90T
 
Message: 5
Date: Tue, 29 Jan 2008 01:25:24 -0500
From: "berniek at technicaldevelop.com" <berniek at technicaldevelop.com>
Subject: [Supras] 57 trim driveability
To: "Supras at supras.com" <Supras at supras.com>
Message-ID: <479EC6D4.6000807 at technicaldevelop.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed


For the last two days, I've taken the '91 out on the road again after 
most of the salt has washed off the roads.  Mods are based upon a 57 
trim CT26, 550cc injectors, Lex, Walbro, 3" exhaust, Treadwell Spearco 
knockoff and the usual supporting changes.  Raising the boost to 16-18 
PSI, the car feels absolutely great, sometimes breaking loose in second 
gear on a dry road (need to fill the gas tank).  For straight line 
acceleration, I could not ask for more, once into second gear, since 
first is unusable at WOT as stated before.  I may add a microswitch and 
solenoid valve in addition to a second boost controller to reduce first 
gear boost, but that is only a partial fix for the real consideration 
which follows.


Most of the controllability regarding power occurs in perhaps the first 
20-30 degrees of throttle opening, notwithstanding the "digital" way the 
boost comes on at 3000 RPM.  Although I'm well satisfied with the power, 
the car is hard to drive from a power modulation standpoint in the real 
world as compared with a normally aspirated engine of the same power.  
I'm curious if anyone has come up with a more linear way of controlling 
boost as a function of throttle position to make the car more drivable 
when getting into corners at high speed.  Ideas that come to mind (some 
are hairbrained) are as follows:


1.  Modification of manual spring type boost controller, where spring 
preload is a function of throttle position through a lever link to match 
spring compression to throttle position.


2.  If elecronically inclined, develop a pulse width modulation circuit 
to drive a high speed solenoid valve to modulate boost bleed as a 
function of TPS potentiometer position.


3.  Revise throttle linkage to provide most of the opening within the 
last 10% of accelerator pedal travel.  That could be done with a 
progressive radius cable saddle on the throttle shaft.  Ford 
accomplished the same thing with linkage angles and a bellcrank in the 
'50s and early '60s when they had the Paxton blown 312 CID engine.


  Looking forward to ideas.


      BernieK






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