Boost issues?

[Saaamon]

My car has a HLM chip in it has just had a new bcs fitted and the actuator is set to about 4.5psi (roughly). When driving along if i hold say 3rd or 4th gear then go WOT it boosts well, right off the end and will hold it, but say WOT throttle 3rd to 4th or 2nd to 3rd to 4th it doesn't make nearly as much boost on the gauge its just over half then 4.5k it starts to go to 3/4's and stays there.

It doesn't seem right to me, any ideas?

Thanks.

[Shinsplintz 101]

Could be a number of things - tired actuator or recirc valve? The turbo running out of puff? What size is it & was the hlm map for that turbo? Sure someone a bit more mechanical will be along shortly to offer a bit more insight

[T5frankie]

didnt i read something about you put a v70 t5 bcs on or am i making that up?

[oblark]

Has it always done it or has it just started to do it ?

[Jamest5r]

Have you tried it with the old bcs?

[Saaamon]

Yes it's a v70 bcs. I know the actuator is good as AndyR's checked it for me just before the map with a special tool. It was fine when it had a standard map with mbc, HLM map has been on for 2weeks now. Ill try an old bcs (850 version) and see what happens.

Thanks.

[960kg]

Yes it's a v70 bcs. I know the actuator is good as AndyR's checked it for me just before the map with a special tool. It was fine when it had a standard map with mbc, HLM map has been on for 2weeks now. Ill try an old bcs (850 version) and see what happens.

Thanks.

You don`t say what motor you have but it seems 850 T5!...

The V70 1997 on TCV is exactly the replacement for the round 850 BCS but did you connect the V70 one in the correct order?

There is a drawing circulating that is incorrect but this one is correct.

[T5frankie]

Funny thing is I put an v70 bcs on my 850 and it didn't work on that car properly

[960kg]

You probably used a dud 2nd hand one Frankie Lol.....

[oblark]

The direct replacement TCV from 850 to V70 -1999 is part number 9155936
The later TCV`s are 9473212 2000 - 2002 and 30670448 2003 onwards.

[mike 850]

about to say, i have a v70 tcv and works fine on my 850

[glock19]

My car has a HLM chip in it has just had a new bcs fitted and the actuator is set to about 4.5psi (roughly). When driving along if i hold say 3rd or 4th gear then go WOT it boosts well, right off the end and will hold it, but say WOT throttle 3rd to 4th or 2nd to 3rd to 4th it doesn't make nearly as much boost on the gauge its just over half then 4.5k it starts to go to 3/4's and stays there.

Thanks.

You didn't mention RPM or acceleration feel. Boost is a restriction to airflow. The more airflow (to the engine) you have, the less boost is captured at the manifold. When the charged air is consumed by the engine, you have less boost.

Until your engine is choked, boost will not rise and of course the boost map from HLM will also compare your engine load with RPM to give you the boost pattern

[Saaamon]

You didn't mention RPM or acceleration feel. Boost is a restriction to airflow. The more airflow (to the engine) you have, the less boost is captured at the manifold. When the charged air is consumed by the engine, you have less boost.

Until your engine is choked, boost will not rise and of course the boost map from HLM will also compare your engine load with RPM to give you the boost pattern

Interesting post, had to read it twice but i think I've understood it. When going quickly through the gears and using the whole rev range up to 6400rpm, the gauge never reads right to the end of the white, the gauge climbs steadily as the rpm increases. It doesnt feel slow when racing through the gears, but does "feel" quicker when one gear is held then the power brought on.

[Saaamon]

You don`t say what motor you have but it seems 850 T5!...

The V70 1997 on TCV is exactly the replacement for the round 850 BCS but did you connect the V70 one in the correct order?

There is a drawing circulating that is incorrect but this one is correct.

yes it is an 850 t5. A friend sent me a diagram which i used for reference and it is the same as yours so all plumbed in correctly. Thanks.

[oblark]

You didn't mention RPM or acceleration feel. Boost is a restriction to airflow. The more airflow (to the engine) you have, the less boost is captured at the manifold. When the charged air is consumed by the engine, you have less boost.

Until your engine is choked, boost will not rise and of course the boost map from HLM will also compare your engine load with RPM to give you the boost pattern

Interesting post, had to read it twice but i think I've understood it. When going quickly through the gears and using the whole rev range up to 6400rpm, the gauge never reads right to the end of the white, the gauge climbs steadily as the rpm increases. It doesnt feel slow when racing through the gears, but does "feel" quicker when one gear is held then the power brought on.

Not sure if this helps, but it shows the tcv duty cycle for given rpm and throttle position.

[Saaamon]

Not sure if this helps, but it shows the tcv duty cycle for given rpm and throttle position.

This is meaningless to me, could you explain?

[glock19]

From Oblarks table, RPM is on the left column
Load is the MAF reading + Throttle Opening (TPS signal) + Vehicle speed (sometimes)
Max High Load = High MAF intake + Load vehicle speed + Wide Open Throttle
Min Low Load = Low MAF intake + High vehicle speed + Small Throttle opening

The numbers in the chart denotes the TCV duty cycle
Low numbers = more restriction from compressor spool (boost) to the wastegate (less boost for engine)
high numbers = less restriction from the compressor to the wastegate (more boost)

Therefore boost control varies throughout the RPM and load range