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Just wondering if it is normal for the boost not to drop off..

I can take the car to over 4500rpm / until line and there is absolutely no drop off from maximum boost whatsoever..

I keep reading stories of diesels losing power when the turbo reaches maximum boost, but mine just keeps pulling until I change gear with no holding back at all.. The engine would quite happily keep going into the red if I let it...

It is a 2000 200Sdi with a 2001 R45 engine.. 200 injectors / pump.. 45 Turbo / 200 manifold @ 14Psi.. 200 MAF.. blocked EGR.. DeCat pipe.. and 200 Box..
 

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My 98 SDi is exactly the same, low down powers crap but after 2500rpm until the red line it pulls like a train!! Been told its not uncommon for the l-series so have just lived with it!

It is wierd though how others with basically the same tunning on there l-series hit max boost at 2k and loose most of there power after 3k but mine is lucky to have hit 12psi at 2k! Max boost 19-20psi is anywhere just before 3000 until 4500!
 

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Mine becomes a bit flat after about 4k. I'm putting it down to my MAF dieing because it didn't used to be like that.
Jim
 

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no thats what it should be like, the turbo will still hold the psi right to the read line as the wastegate is controlling the boost. the power drop off is becuase the turbo is less efficient at high rpms and the car may not be getting enough fueling at higher rpm's. U can see from dyno graphs from standard cars that max torque is produced around 2k - 2.5k and then drops off towards 4k-5k. Then u look at a dyno from a hybrid turbo and its a flat torque curve from 2k, giving good pull to the red line.
 

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Sounds like you aren't running enough boost. At higher boost levels you'll find that the boost drops off at higher rpm's as the turbo simply can't shift enough air. Mine peaks at about 3-3.5k rpm and drops off after that.
 

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Mine holds full boost right until the limiter, so there's definitely some variation!

Hits 20psi at about 1850rpm, and it holds solid right there until the limiter cuts it off.

There's no reason for boost to drop off, really, unless you're running far too much boost, as turbos tend to work better as the revs climb, so as long as there's a reasonable load on the engine, full boost should be produced. Fuelling may drop off, but boost definitely shouldn't unless the fuelling leans out dramatically.
 

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Mine holds full boost right until the limiter, so there's definitely some variation!

Hits 20psi at about 1850rpm, and it holds solid right there until the limiter cuts it off.

There's no reason for boost to drop off, really, unless you're running far too much boost, as turbos tend to work better as the revs climb, so as long as there's a reasonable load on the engine, full boost should be produced. Fuelling may drop off, but boost definitely shouldn't unless the fuelling leans out dramatically.
Mine does too now.
I found my felxi join to the turbo was all oily, must have been leaking pressure, it doesn't leak now.
 

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Boost can drop off because the turbo is too small. Ask any T16 owner! Mine used to make 11.5psi at 2,500rpm but only 9psi at 6,500 as the turbo simply can't supply enough air. The turbo simply can't shift enough air to maintain the boost pressure at high rpms.

I don't know for sure if this is happening on the L series though, but I suspect it could be.

You are right though it could well be it leaning out as the fuel delivery limit is reached, which would obviously then decrease the boost level as there are less exhaust gases to spin the turbine.
 

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Boost can drop off because the turbo is too small. Ask any T16 owner!
I don't have to ask any T16 owner, as I am one. ;)

I've had about six T16 turbo cars over the years that I've fitted gauges and boost controllers to, and never had an issue with the T25 losing boost pressure higher up the rev range. Losing efficiancy and blowing hot air causing the *power* to drop off, yes, but never had a problem with the boost pressure dropping off to any lower than my set peak level, either on the road or on the rollers.

Maybe I've just been lucky! :D
 
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