Boost gauge. Now I'm no expert but....

[C.A.R.]

....I have played Gran Turismo! So I don't know how qualified that makes me?

My boost gauge is a nice little gadget. I don't like how it doesn't look OEM, but ima fix that (as per my other thread) and I don't care really how accurate it is, I just like to see the turbo is behaving properly...

Which leads me on to the purpose of this thread.

On Gran Turismo (hear me out!) the boost holds at the same pressure throughout the rev range. Today, in a rare pursuit of speed in the HDi I exceeded 3,500 revs (I know Tom, I know). The boost comes in at around 1500-1800 and holds at 15-16psi, but what I noticed is that the car quickly ran out of 'puff' after 3 grand. Glancing at the boost gauge it was only reading 11psi and falling?

I know diesels don't "do" revs, but my focus TDCi seemed to still have power higher up.

Is this normal, or have I sprung a leak somewhere? Or is the turbo guffed? Service due next week so I can have a good look around, if there is a problem, where should I look for it?

[WiNgNuTz]

Not an entirely helpful post, but im having a remotely similar problem.

My boost doesnt peak (@ 19psi) until i have to change gear at about 4.5k rpm, so was also wondering if my turbo might be giving up.

Im not sure if yours should be dropping boost after 3k, as mine (when it was standard) was holding a steady 14psi up to the gear change, but peaking about 2k sounds about normal from other accounts ive read.

Im certainly no diesel expert myself, so i could be way off the mark. Im sure someone will be along shortly to correct me if i am.

[Dum-Dum]

I guess your still running a cat, it strangles it, thats the current restriction.

After that your restriction will be the turbo being too small.

[lolsteve]

the focus might have a vnt My housemate has a mondeo tdci 2.0 and that has one.

[aircool]

Standard map?

HDi's as standard don't seem to have much fueling at the top end.

More fuel = more boost.

[Poodle]

Wingnutz, you're driving a dt, completely different kettle of fish. And you're running 19psi on a t2 - MTFU!

It's pretty normal for HDis to drop boost after 3k, as said above, the exhaust system is pretty restrictive as standard and fuelling drops off after 3.5-4k anyway.

[WiNgNuTz]

Wingnutz, you're driving a dt, completely different kettle of fish. And you're running 19psi on a t2 - MTFU!

It's pretty normal for HDis to drop boost after 3k, as said above, the exhaust system is pretty restrictive as standard and fuelling drops off after 3.5-4k anyway.

See? I knew someone would come along and correct me!

[Toms306]

Afaik Chris is running stage 1 map.

Bit I'm still gonna say the turbos too small as standard, shame its not vnt eh Chris.

[Poodle]

In which case i find it a little odd that boost is falling after 3k, should have the fuelling up there to maintain flow...

[C.A.R.]

Should have said, has a stage 1 prosteve map on it, by previous owner. Could there be a leak at the EGR causing this? And is 15psi normal for a peak boost pressure on stage 1?

[Poodle]

Could be i guess, worth checking. How badly oiled is your inlet elbow? Alternatively, could be an exhaust restriction, have you decatted etc?

And yes, 15psi peak is pretty normal.

[Jonny81191]

I reckon its down to your exhaust..

On a completely standard car, I found that there was absolutely no point going over 3k. With a stage 1 map, (std exhaust still), it was a bit better, and I found myself revving higher to around the 3.5 mark.

When I bought my stage 2 (standard exhaust with pikey decat), it was similar, 3.5k was the "natural" point to change when giving it beans. Now I've replaced the decat with a straight pipe and got a straight through backbox, I often find I'm up near the limiter without trying, the engine is so much more free revving.

I've also noticed that when approaching the limiter, the boost peaks, rather than dropping as per the OP.

[C.A.R.]

It has still got the cat in place, as well as a very restrictive standard system.

Unfortunately I currently lack the funds to get a straight-thru, but what should I be looking for when I do eventually take the plunge? Should I go to an exhaust centre and spunk £300+ on a full system?

[4WayDiablo]

I don't see why a pikey lash up won't work as well. The only difference I've seen comparing my Ss turbo back power flow exhaust to home made straight through is the noise. Mine just sounds better lol
These turbo'd diesels just need to get rid of gasses asap

[C2K]

On another note if your hdi system is genuine pug and in good nick i might take it off your hands.

[Jonny81191]

Home build FTW!

Save the cash for other shineys you can't build with a grinder and welder!

[C.A.R.]

If it were genuine Peugeot I'd keep it myself! Unfortunately its a combination of aftermarket cat/downpipe rusty mid section and £35 back-box with the special 'droopy cock' stile tip!

I wonder what a garage would charge to knock one up. What's the best bore to go for?

[Midnightclub]

2.25" Is standard, that'll be fine but if you really wanted to you could go for 2.5" but gains won't really be noticeable and it will probably be more expensive

[Jonny81191]

2.25 straight with centre box is enough for most!

[lolsteve]

Pikey lash up! seriously how often do people go under your car and go "ooooo stainless"

[4WayDiablo]

There isn't much of a difference but the larger the diameter the deeper the noise :-)

[Dum-Dum]

Home made garage lash up, a garage may de-cat for free if they can keep the cat.

[Joe]

if you were closer id decat for free if i could keep the pussy...

[Jonny81191]

Same, have you got a mate with a welder who can do it?