The car is a 95 Nissan 240sx w/ a redtop sr20det engine.I know its not a honda but i figured it wouldnt matter.The car has a Garrett gt25R Dual BB turbo,custom SS manifold,Tial 38mm wastegate and Greddy profec B spec 2 boost controller.The problem is that at around 5k-5.5k the boost falls off to either 5lbs or 0lbs.It does it in any gear,no matter how the boost controller is set.The Greddy profec manual says it would do that because the gain isnt set high enough,so weve cranked the gain up in 10% increments from 0 to 60% and still does the exact same thing.Ive tried low gain high set boost,high gain low set boost,both low and both high and still get the same thing,just at different boost levels.Ive also turned off the boost controller and completely bypassed it and still get the same thing.The way the manifold was built,the wastegate only draws exhaust from #1 and #3 cylinders.This was only done because there isnt room to run the wastegate anywhere else and those 2 cylinders were the only ones that could be reached.I was thinking this might be the problem but am not 100% sure.It was not doing this before I had this manifold built,same turbo and boost controller,internal gate and stock manifold.Anybody had any similar problems?Thanks

 

i gues the flow of your turbo or intake exhaust isnt good enough. or to much valve overlap.

 

I havent swapped out the cams and the car has been up to 19lbs consistantly before the external gate was put on.Thanks though

 

add more duty cycle to the boost control solenoid.

 

How much more should I take it up to?Ive taken it from 0% to 60% in 5%-10% increments and still get mostly the same thing,though boost falls off at a slightly higher rpm.Thanks

 

its b/c you dont have vtec. vtec will help your top end alot. Either that or your vtec fluid is low, fill that up. Or maybe god doesnt love anything but hondas and is damning your hotness of a car.

 

vtec makes boost drop sooner

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dnbruut &raquo;</TD></TR><TR><TD CLASS="quote">vtec makes boost drop sooner</TD></TR></TABLE>
wuh?....

 

Its got vtec killer cams.Maybe thats why...Ive still been filling up the vtec resevior fluid though just to be sure thats not it.

 

if your turbo is too small boost will drop sooner because there is more valve overlap.

 

The engnie has never been apart,so no big cams.It would be steady with the stock turbo,and the gt25r turbo before,at the exact same settings as now...only thing that was done different now is the external gate.

 

Sounds like the manifold may be the culprit.

 

You might just want to check the wastegate valve/diaphram. It might be stuck open? It's a Tial so probably not. Do you have the upper WG port connected to the outlet on the Profec solenoid or is the upper port open to atmosphere?