[Supras] performance loss with hardpipes and larger IC?

[berniek at technicaldevelop.com]

Jeff:


    Most of the bends are mandrelbends from ebay welded in with straight 
sections of pipe.  The fishmouth cut and weld angles in the replacement 
for the rigid plastic 3000 pipe feed line involves two angles of no more 
than about 20 degrees. 


    Today I took a friend out after connecting up a good dead weight 
checked gauge in the car.  Although the car felt better than last night, 
apparently I somehow lost  about 2 PSI of boost, now at 13 PSI.  Before 
it was 15.  So I'll crank up the boost a bit more. 


    Retrospectively, I should have gone with Weisco or other longer 
skirt forged pistons.  How much boost do you think the stock pistons are 
good for while getting decent life out of the engine?  I will always run 
it on the rich side.


    Bernie

Jeff Mohler wrote:
> Im betting this is where mandrel pays off.
>
>
>
> On Jan 12, 2008 9:37 PM, berniek at technicaldevelop.com
> <berniek at technicaldevelop.com> wrote:
>   
>> Over Christmas week I installed a Treadstone IC, a spitting image of the
>> Spearco.  Using the stock IC outlet pipe as a template, I made up
>> hardpipes from 2-1/4" exhaust tubing, with one section, where it comes
>> through the passenger's side fender coupled with about 4" of stretched
>> stock hose.  Outlet of the turbo is still the stock hose into a2-1/4"
>> tubing mandrel bend replacing the stock cast elbow, feeding a 2-1/2"
>> silicone elbow into the IC.  The 3000 pipe inlet hose is now fed with
>> 2-1/4" tubing, "fishmouth" cut and welded to clear the strut tower.  The
>> black rigid plastic piece is gone.
>>
>>
>> Now as before, I take the signal for the boost controller from a tapping
>> in the 3000 pipe.  After reading postings from Jeff Mohler and others
>> about restriction in the stock cooler and piping, it was clear that a
>> modified CT26 (57 trim in my case) could use all the outlet pressure
>> reduction possible to avoid bearing wear.
>>
>>
>> Now, as before, I have not yet installed the under-engine cover, as I
>> still need to change the A/C suction hose (and filter dryer, and
>> recharge the system, probably in the spring).  In an event, since I take
>> boost control from the 3000 pipe, I expected the performance to remain
>> essentially unchanged, but with less stress on the turbo.  I took the
>> car out for the first time tonight since cleanup work and other
>> commitments got in the way.  In 40F weather, I would expect the same
>> push in the back as before.  But now it does not break traction in
>> second gear as it was on the verge of before with the stock IC and piping.
>>
>>
>> It seems to have lost something in performance.  The problem could be
>> me, or the weather or something else.  Clearly there is far less
>> restriction than was formerly the case in the IC and piping.  But it
>> seems to build boost a bit more slowly, and it feels as if I need to
>> push it to 6000 RPM.  Before, the boost would come on at 3000 and the
>> car would rush right up to 6000 RPM or beyond.  The gas in the tank is
>> unchanged (good quality Amoco) as is the fuel mixture, in the range of
>> 9.5 to 11.0:1, sometimes rich but again unchanged from before.  Under
>> normal conditions the engine runs fine, evenly and smoothly.  I'm
>> certain there are no piping leaks.  I know there are some who claim that
>> increased volume of a better IC and bigger piping cause lag, but at
>> most, less than half a liter was added to the air path volume, an
>> insignificant consideration.
>>
>>
>> Boost is presently measured using the stock sensor, with a resistive
>> divider to make the dash gauge read 14.5 to 15 PSI full scale.  I'll
>> take a reading with a real gauge to confirm the boost, but taken from
>> the 3000 pipe, it should not have changed.
>>
>>
>> Any ideas about performance reduction would be appreciated.  Thanks and
>> happy new year.
>>
>>
>> BernieK
>>
>>
>>
>>
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>>     
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