[SR] Boosting until redline - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

reccakun08 · 07-19-2008, 04:13 AM

Asking everyone with a sr20det with stock t25 turbo boosting over stock how much boost can it hold to until redline?

Currently i am boostin about 12psi on a mbc. It will not hold the 12psi all the way to redline it will drop all the way down to 7psi i think after 5,500rpm. I tried cranking boost to 14psi and it is still dropping. I know the stock t25 does start losing boost to redline but how much?

My friends car holds 12psi all the way to redline.

Boost leak? exhaust leak?
Car drives fine and idles fine. Just doesnt pull hard up top from the decreasing boost. Full exhaust and fmic.

Thanks.

Def · 07-19-2008, 07:12 AM

Mine held about 11.5 psi to redline, and it was in great condition when I took it off. Could have probably held a bit more with an EBC, as I just had a cheap MBC at the time.

*fliprayzin240sx* · 07-19-2008, 07:38 AM

Get an AVC-R, nuff said...

tha240star · 07-19-2008, 07:54 AM

i have a turbo xs mbc and it holds 13 to redline, its spike a lil at first to like 14-15 but thats about it

SoSideways · 07-19-2008, 08:27 AM

I have a Turbo XS dual stage MBC, and it can only hold about 8psi to redline. At the time of the dyno graph, I had it set at 14psi.

s15specR · 07-19-2008, 09:28 AM

I got a new in box AVC-R for sale, hit me up if you need it, will let it go for the low

reccakun08 · 07-19-2008, 10:17 AM

i have Turbo XS dual stage MBC. You think thats the reason im not able to hold boost? Sosideways my graph is similar to yours. Gotta find it.

s15specR pm a 'low' price shipped.

Thanks.

garbury · 07-19-2008, 10:59 AM

I made my own mbc and it hit 15 psi and dropped gradually to 12 by redline. http://www.geocities.com/chmwatson/FAQs/mbc.html I threw on my ebc with the stock t25 and it would still drop down by redline. The t25 turbo has problems holding boost levels that high, unless an avcr is really that legit.

Honestly, besides the ability to change boost on the fly, I'd prefer the $12 hardware store boost controller over my greddy profec type-s.

!Zar! · 07-19-2008, 11:28 AM

The stock wastegate on a t25 freaks out once you start trying to raise the boost.

Also, I hope you aren't trying to boost your car that high with stock sr and no management.

haha.

Def · 07-19-2008, 04:01 PM

Quote:

Originally Posted by !Zar!

The stock wastegate on a t25 freaks out once you start trying to raise the boost.

Also, I hope you aren't trying to boost your car that high with stock sr and no management.

haha.

14-15 psi on a stock T25 with a stock ECU/injectors/MAF is just fine. The AFR curve is as jacked as it is on stock boost(lean in the midrange), but it's fine for the most part, especially street driving.

I recommend a FMIC to keep IATs down, as it doesn't take long for the SMIC to give up the ghost when trying to cool a little hairdryer like a cranked up T25.

reccakun08 · 07-19-2008, 01:48 PM

yeah i thought about trying the hks actuator to see if does indeed help and guess prove the mbc isnt reliable.

reccakun08 · 07-21-2008, 11:43 PM

Would an exhaust leak or a boost leak be a probable cause?

ILoveJDM · 07-22-2008, 01:51 AM

Quote:

Originally Posted by reccakun08

Would an exhaust leak or a boost leak be a probable cause?

could be

its possible one of your lines are backing off during boost.

i was having the same problem, so i reclamped and ziptied all my vaccum lines that i had been around (recent install of avc-r)

SoSideways · 07-22-2008, 08:28 AM

If you're worried about a leak, get yourself a pressure tester, hook it up to where your MAF would be, and pressurize the system to like 20psi.

You will find your leaks much better with that method, if you have any leaks at all.

codyille · 07-23-2008, 04:54 PM

I've seen this problem with homemade boost controllers. Try a higher quality controller. Or different vac line?

07-19-2008, 04:13 AM	#1
reccakun08 Zilvia FREAK! Join Date: Jun 2003 Location: Rockville, Maryland Age: 40 Posts: 1,090 Trader Rating: (5) Feedback Score: 5 reviews	[SR] Boosting until redline Asking everyone with a sr20det with stock t25 turbo boosting over stock how much boost can it hold to until redline? Currently i am boostin about 12psi on a mbc. It will not hold the 12psi all the way to redline it will drop all the way down to 7psi i think after 5,500rpm. I tried cranking boost to 14psi and it is still dropping. I know the stock t25 does start losing boost to redline but how much? My friends car holds 12psi all the way to redline. Boost leak? exhaust leak? Car drives fine and idles fine. Just doesnt pull hard up top from the decreasing boost. Full exhaust and fmic. Thanks.

07-19-2008, 07:38 AM	#3
fliprayzin240sx Man w/ CTSV & a Car Seat Join Date: Aug 2002 Location: Tampa Posts: 17,998 Trader Rating: (19) Rides Gallery: fliprayzin240sx Feedback Score: 19 reviews	Get an AVC-R, nuff said... __________________ If you think Zilvia has too many assholes... CLICK HERE!!!

07-19-2008, 09:28 AM	#6
s15specR Zilvia FREAK! Join Date: Oct 2007 Location: USA Posts: 1,023 Trader Rating: (18) Feedback Score: 18 reviews	I got a new in box AVC-R for sale, hit me up if you need it, will let it go for the low __________________

07-19-2008, 11:28 AM	#9
!Zar! Post Whore! Join Date: Nov 2004 Location: North Korea Posts: 14,579 Trader Rating: (27) Feedback Score: 27 reviews	The stock wastegate on a t25 freaks out once you start trying to raise the boost. Also, I hope you aren't trying to boost your car that high with stock sr and no management. haha. __________________

07-19-2008, 07:12 AM	#2
Def Post Whore! Join Date: Apr 2004 Location: Houston, TX Posts: 2,701 Trader Rating: (16) Feedback Score: 16 reviews	Mine held about 11.5 psi to redline, and it was in great condition when I took it off. Could have probably held a bit more with an EBC, as I just had a cheap MBC at the time.

07-19-2008, 07:54 AM	#4
tha240star Leaky Injector Join Date: Feb 2008 Location: San Diego Age: 39 Posts: 95 Trader Rating: (0) Feedback Score: 0 reviews	i have a turbo xs mbc and it holds 13 to redline, its spike a lil at first to like 14-15 but thats about it

07-19-2008, 08:27 AM	#5
SoSideways Post Whore! Join Date: Apr 2003 Location: 你老母 Posts: 4,371 Trader Rating: (4) Feedback Score: 4 reviews	I have a Turbo XS dual stage MBC, and it can only hold about 8psi to redline. At the time of the dyno graph, I had it set at 14psi.

07-19-2008, 10:17 AM	#7
reccakun08 Zilvia FREAK! Join Date: Jun 2003 Location: Rockville, Maryland Age: 40 Posts: 1,090 Trader Rating: (5) Feedback Score: 5 reviews	i have Turbo XS dual stage MBC. You think thats the reason im not able to hold boost? Sosideways my graph is similar to yours. Gotta find it. s15specR pm a 'low' price shipped. Thanks.

07-19-2008, 10:59 AM	#8
garbury Leaky Injector Join Date: Apr 2006 Location: Arizona Posts: 93 Trader Rating: (0) Feedback Score: 0 reviews	I made my own mbc and it hit 15 psi and dropped gradually to 12 by redline. http://www.geocities.com/chmwatson/FAQs/mbc.html I threw on my ebc with the stock t25 and it would still drop down by redline. The t25 turbo has problems holding boost levels that high, unless an avcr is really that legit. Honestly, besides the ability to change boost on the fly, I'd prefer the $12 hardware store boost controller over my greddy profec type-s.

07-19-2008, 01:48 PM	#11
reccakun08 Zilvia FREAK! Join Date: Jun 2003 Location: Rockville, Maryland Age: 40 Posts: 1,090 Trader Rating: (5) Feedback Score: 5 reviews	yeah i thought about trying the hks actuator to see if does indeed help and guess prove the mbc isnt reliable.

07-21-2008, 11:43 PM	#12
reccakun08 Zilvia FREAK! Join Date: Jun 2003 Location: Rockville, Maryland Age: 40 Posts: 1,090 Trader Rating: (5) Feedback Score: 5 reviews	Would an exhaust leak or a boost leak be a probable cause?

07-22-2008, 08:28 AM	#14
SoSideways Post Whore! Join Date: Apr 2003 Location: 你老母 Posts: 4,371 Trader Rating: (4) Feedback Score: 4 reviews	If you're worried about a leak, get yourself a pressure tester, hook it up to where your MAF would be, and pressurize the system to like 20psi. You will find your leaks much better with that method, if you have any leaks at all.

07-23-2008, 04:54 PM	#15
codyille Leaky Injector Join Date: Sep 2006 Location: Cedar City, UT Age: 41 Posts: 50 Trader Rating: (1) Feedback Score: 1 reviews	I've seen this problem with homemade boost controllers. Try a higher quality controller. Or different vac line?