Dyno'd car today, Having problems with boost please help! - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

ask52 · 07-15-2006, 07:22 PM

Hey guys I went to the dyno today (dyno jet) To see what the power was. Also I have been having troubles with the boost falling after 4800 RPM. These are the mods

redtop sr, fmic, greddy bov, turbosmart dual stage boost controller, electric fans, megan ss header, 3" turbo elbow, 3" exhaust no cat, K&N cone filter, stock t25.

The car boost's 15 psi right up till 4900 RPM then falls to 8psi (it falls right away not gradually, almost like some one hit a switch). @ 4800 rpm its at 200rwhp. Then it falls to 180 and slowly goes up to 211rwhp @ 8psi around 6500rmp. They did 4 pulls but could figure out what was wrong. They emailed me the dyno graph and you need the dynojet software to view it or I would post it up. Any ways I went home to try to figure out what was wrong. I test the ic pipes for leaks and nothing. I then pulled the line off the waste gate and plugged the vacuum line from the engine. I went on the high way and slowly got the car up to 4500rpm with out boosting. The I opened it up, The boost hit 15.5 psi and smoothly fell to 12psi @7000rpm.

So now I don't know what is wrong. I'm guessing that the t25 is just not big enough to hold 15 psi all the way to 7400 rpm. But why does the boost fall so fast with the boost control hooked up? If any one has any ideas please let me know!

Thanks...Josh.B

P.s We check for exhaust leeks as well and there was nothing.

smithers584 · 07-15-2006, 07:28 PM

Quote:

turbosmart dual stage boost controller

thats most likely your issue! you shouldnt run your t25 at 15 psi unless you want to blow it! even if you dont blow it, you are out of the turbos efficency range and it basically just turns into a heat pump. but with it bleeding off from 15 to 12 smoothly at high rpms that is normal.

ask52 · 07-15-2006, 09:09 PM

o.k thanks man, I'm gonna try a new boost controller. I'll keep the boost down a bit.

slideways2004 · 07-15-2006, 10:33 PM

#1- check for boost leaks
#2- lower boost
#3- change boost controller to and ebc

Id RaThEr DrIfT · 07-15-2006, 10:41 PM

yeah i had the same bc and it sucks! id drop boost also

smithers584 · 07-15-2006, 10:52 PM

well the reason i say that is because you are going from 15 to 8, which happens to be the setting for the stock wastegate. if you had a boost leak chances are you car would run like sh!t and you wouldnt go from 15 straight to 8.

ask52 · 07-16-2006, 07:48 PM

I'm gonna look for an ebc, thanks guys

revoltrise · 07-17-2006, 09:09 AM

i thought sr's had dual stage boost, ie starts high and drops off low on long pulls to make sure your dont fry your seals/turbo etc....if so i wouldnt mess wiht it unless you had a spare turbo lying around.

and like everyone else said no more then 12psi on a t25.

Nostradamus · 07-17-2006, 09:34 AM

^^RB25's have dual stage boost not sr20's

07-17-2006, 09:34 AM	#9
Nostradamus Zilvia Junkie Join Date: Sep 2003 Location: poolhall ma Posts: 355 Trader Rating: (0) Feedback Score: 0 reviews	^^RB25's have dual stage boost not sr20's __________________

07-15-2006, 07:22 PM	#1
ask52 Leaky Injector Join Date: Aug 2005 Location: North west Posts: 64 Trader Rating: (0) Feedback Score: 0 reviews	Dyno'd car today, Having problems with boost please help! Hey guys I went to the dyno today (dyno jet) To see what the power was. Also I have been having troubles with the boost falling after 4800 RPM. These are the mods redtop sr, fmic, greddy bov, turbosmart dual stage boost controller, electric fans, megan ss header, 3" turbo elbow, 3" exhaust no cat, K&N cone filter, stock t25. The car boost's 15 psi right up till 4900 RPM then falls to 8psi (it falls right away not gradually, almost like some one hit a switch). @ 4800 rpm its at 200rwhp. Then it falls to 180 and slowly goes up to 211rwhp @ 8psi around 6500rmp. They did 4 pulls but could figure out what was wrong. They emailed me the dyno graph and you need the dynojet software to view it or I would post it up. Any ways I went home to try to figure out what was wrong. I test the ic pipes for leaks and nothing. I then pulled the line off the waste gate and plugged the vacuum line from the engine. I went on the high way and slowly got the car up to 4500rpm with out boosting. The I opened it up, The boost hit 15.5 psi and smoothly fell to 12psi @7000rpm. So now I don't know what is wrong. I'm guessing that the t25 is just not big enough to hold 15 psi all the way to 7400 rpm. But why does the boost fall so fast with the boost control hooked up? If any one has any ideas please let me know! Thanks...Josh.B P.s We check for exhaust leeks as well and there was nothing.

07-15-2006, 09:09 PM	#3
ask52 Leaky Injector Join Date: Aug 2005 Location: North west Posts: 64 Trader Rating: (0) Feedback Score: 0 reviews	o.k thanks man, I'm gonna try a new boost controller. I'll keep the boost down a bit.

07-15-2006, 10:33 PM	#4
slideways2004 Nissanaholic! Join Date: Apr 2005 Location: Houston Age: 38 Posts: 1,706 Trader Rating: (6) Feedback Score: 6 reviews	#1- check for boost leaks #2- lower boost #3- change boost controller to and ebc

07-15-2006, 10:41 PM	#5
Id RaThEr DrIfT Zilvia Addict Join Date: May 2006 Location: socal Posts: 845 Trader Rating: (0) Feedback Score: 0 reviews	yeah i had the same bc and it sucks! id drop boost also

07-15-2006, 10:52 PM	#6
smithers584 Zilvia Junkie Join Date: Dec 2004 Location: sc Posts: 416 Trader Rating: (0) Feedback Score: 0 reviews	well the reason i say that is because you are going from 15 to 8, which happens to be the setting for the stock wastegate. if you had a boost leak chances are you car would run like sh!t and you wouldnt go from 15 straight to 8.

07-16-2006, 07:48 PM	#7
ask52 Leaky Injector Join Date: Aug 2005 Location: North west Posts: 64 Trader Rating: (0) Feedback Score: 0 reviews	I'm gonna look for an ebc, thanks guys

07-17-2006, 09:09 AM	#8
revoltrise Join Date: Nov 2005 Location: c-TOWN, RI Posts: 2 Trader Rating: (0) Feedback Score: 0 reviews	i thought sr's had dual stage boost, ie starts high and drops off low on long pulls to make sure your dont fry your seals/turbo etc....if so i wouldnt mess wiht it unless you had a spare turbo lying around. and like everyone else said no more then 12psi on a t25.