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Discussion Starter #1 (Edited)
My friend recently changed his transmission and he got a shorter geared D series (SI) the car was tuned with a dx transmission previous to the switch.

Prior to switching out the transmission the turbo would spool up to 13 to 14 psi in second gear at around 3500rpm...now in second gear 13psi doesnt come in until 6500 and in third gear 13psi doesnt come in until 5500...

To get 13psi to come in at 4500-5000 in second gear, he has to partial throttle the gas, and same thing for third gear.. is this tunning?

The car just seems to act a little different with the shorter geared transmission. For the turbo to spool to its peak PSI (13.5/14) you have to partial throttle it...
 

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Discussion Starter #3
ahh ok.
so adding a boost controller would have no effect on this ? its completely to do with load?

could a new tune sort out the load?
 

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I'm going to guess air conditioning :uh:
Yes lol

really? ac builds more boost??? :eek:
It builds its faster because its loading the motor. It doesnt add more boost/power. It just comes on sooner, lower rpm. But it may have a small power lose due to ac robbing you of power.

Just think about boosting up hill vs boost down hill. Your see your boost sooner in lower rpm while going up hill vs going down hill when there is no load.
 

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I cant say that I know for sure, but Ive certainly experienced it.
It could be that there is some physical relationship with progressive throttle and spool up, or it could be as simple as where in the map you are when you hit the throttle in different ways. Perhaps the higher advance seen when rolling into it spools the turbo better than going WOT and going straight into where timing is pulled.
 

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im liking the info found in this thread. i found myself learning.

OP let us know if you get it tuned and if it helped.
 

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I havent been able to figure this one out.
Noticed that the turbo wont spool if you rev the engine in neutral or first.
No matter how you open the throtell. Or how wide.
But put it into second and it seems to spool and make boost.

Would love to hear why this happens after all isnt your spool and boost related to your engine RPM and how much air is flowing past the hot side. Why does load play such a drastic effect on spool up.
 

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Because load gives you hotter EGTs, and it isn't just exhaust flow that spools the turbo, it's exhaust ENERGY. And heat = energy.
 

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I have a better idea for no load spool versus load spool.

Look at you injector duty cycle, then tell me why it won't spool in neutral.


More fuel = more exhaust energy and exhaust gas volume to spool the turbine up.
 
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