Engine: T5: - T5's BOOST QUESTION

mick1232 · Jun 14th, 2009, 12:34

Hi guys, who owns a HPT T5's do you get full boost through all gears 1st & 2nd i get 0 psi positive boost pressure, 3rd gear i get around 8psi DO I HAVE A PROBLEM HERE as ive heard c70 t5 boost from 3rd gear high pressure normal through 1&2 gears ?

t5pete · Jun 15th, 2009, 00:05

You should get boost through all the gears but you will get lower boost in the lower gears

Alan M · Jun 15th, 2009, 10:36

What year car do you have? You should be seeing near enough the same boost through all the gears as standard holding at the same peak values every time at WOT with no fluctuation if there are no problems. Have you checked for vacuum/boost leaks, or perished hoses? If all is well there, get your codes read to see if there are any problems, that may be hindering performance, that the car itself has picked up to log a fault code.

mick1275 · Jun 15th, 2009, 18:27

C70 T5 COPUE 2.3L 2001 ME7.0 BOSCH ECU
1st gear holding at 3000rpm foot flat down to 6000rpm with 0 psi boost pressure straight into 2nd gear negative boost pressure unto 3500rpm vacuum at 20-25 inHg boost pressure then climbs upto 0 psi at 4500rpm keeping on the throttle to 6 grand into 3rd climbing between 3000-4000rpm i start to get positive boost pressure upto 8 psi @max rpm. Ive looked at the ECU NO fault codes stored ,also pipes ,hoses arnt a questions all brand new and secured with high pressure hydraulic hose clamps new actuator diafram no smoke from turbo or any in pipes I have also done a full vacuum system test by pressurising through the turbo i did find a minor leak @ the intercooler but repaired that.the only thinkl concerning me to this fault it the boost control selonoid situated side of air filter box but i would have thought a fault would have come up if malfuncting

Penguinistics · Jun 15th, 2009, 19:27

If the boost control valve was stuck open the boost pressure would be limited to that needed to overcome the waste gate diaphragm spring. There wouldn't be zero boost, rather as the revs climbed the boost would be limited. To test if it is this you could just disconnect, temporarily, the vacuum tube from the boost control valve to the waste gate. The waste gate wouldn't open though in that circumstance so you'd have to be careful. Sounds like you know what boost you are getting though so you would have to manually keep an eye and curtail as necessary.

Jun 14th, 2009, 12:34	#1
mick1232 I've Been Banned Last Online: Sep 4th, 2015 22:06 Join Date: Feb 2008 Location: yorkshire	T5's BOOST QUESTION Hi guys, who owns a HPT T5's do you get full boost through all gears 1st & 2nd i get 0 psi positive boost pressure, 3rd gear i get around 8psi DO I HAVE A PROBLEM HERE as ive heard c70 t5 boost from 3rd gear high pressure normal through 1&2 gears ?

Jun 15th, 2009, 00:05	#2
t5pete The three volvo's Last Online: May 26th, 2019 15:58 Join Date: Mar 2009 Location: barnsley	You should get boost through all the gears but you will get lower boost in the lower gears __________________ Sunny barnsley

Jun 15th, 2009, 10:36	#3
Alan M Senior Member Last Online: Jan 24th, 2023 07:05 Join Date: Dec 2007 Location: Cannock/Solihull	What year car do you have? You should be seeing near enough the same boost through all the gears as standard holding at the same peak values every time at WOT with no fluctuation if there are no problems. Have you checked for vacuum/boost leaks, or perished hoses? If all is well there, get your codes read to see if there are any problems, that may be hindering performance, that the car itself has picked up to log a fault code.

Jun 15th, 2009, 18:27	#4
mick1275 Mechanical specialist Last Online: Jul 24th, 2017 21:51 Join Date: Mar 2007 Location: PONTEFRACT	C70 T5 COPUE 2.3L 2001 ME7.0 BOSCH ECU 1st gear holding at 3000rpm foot flat down to 6000rpm with 0 psi boost pressure straight into 2nd gear negative boost pressure unto 3500rpm vacuum at 20-25 inHg boost pressure then climbs upto 0 psi at 4500rpm keeping on the throttle to 6 grand into 3rd climbing between 3000-4000rpm i start to get positive boost pressure upto 8 psi @max rpm. Ive looked at the ECU NO fault codes stored ,also pipes ,hoses arnt a questions all brand new and secured with high pressure hydraulic hose clamps new actuator diafram no smoke from turbo or any in pipes I have also done a full vacuum system test by pressurising through the turbo i did find a minor leak @ the intercooler but repaired that.the only thinkl concerning me to this fault it the boost control selonoid situated side of air filter box but i would have thought a fault would have come up if malfuncting

Jun 15th, 2009, 19:27	#5
Penguinistics VOC Member Last Online: Nov 20th, 2021 22:30 Join Date: Apr 2009 Location: Preston	If the boost control valve was stuck open the boost pressure would be limited to that needed to overcome the waste gate diaphragm spring. There wouldn't be zero boost, rather as the revs climbed the boost would be limited. To test if it is this you could just disconnect, temporarily, the vacuum tube from the boost control valve to the waste gate. The waste gate wouldn't open though in that circumstance so you'd have to be careful. Sounds like you know what boost you are getting though so you would have to manually keep an eye and curtail as necessary.

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