[Supras] 57 trim driveability

[berniek at technicaldevelop.com]

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