Thread: Raising boost on a td5

Reno France ?
I'm from Chalon-sur-soane.
Sorry can't help you with what you have asked but I'd like to know myself.
Might be a good idea to post the question in the Defender forum on here as well.

Alsace! Where France, Germany and Switzerland collide and the women are pretty.

Originally Posted by RenoHuskerDu

My td5 has a new turbo that just got put on by the dealer before I bought it. Unlike other td5 turbos I've seen here in France, the wastegate has an adjustment rod.

Looks like a standard Td5 turbo to me...

1) the td5 can make a lot more power and still be reliable

Indeed!

2) the exhaust manifold will however need stronger studs

No, it will need to have the interwebbing removed and some of the stud holes enlarged to accomodate for some movement. Standard Class 8.8 studs are perfectly up to the task once the manifold warping tendency is rid of, only some dudes think more make up torque is better and that's when the studs become prone to shear. Can get a fancy ceramic coated manifold but not worth IMHO.

3) you can safely raise the boost a fair amount

Yes but with your current set up power gains will be marginal

4) Discos have an overboost cutoff device that Defs don't

Hmmm... All Td5 engines have an inlet manifold air pressure sensor that feeds the ECU, this sensor is common to all electronically managed diesels and is widely known as IAT/MAP (it also measures inlet air temperature). The ECU will cut fuelling when detecting an overboost situation through the MAP sensor.

There is a difference in the way these vehicles do boost management though. Whilst both use boost pressure to operate the wastegate actuator, the Disco does it electronically through the wastegate modulator ('modulates' wastegate actuator pressure to obtain boost pressure values that best suit that particular fueling instance). On the Defender the wastegate actuator is controlled mechanically and directly by boost pressure. The wastegate doesn't 'cut-off' boost, it simply bypasses exhaust gases so that turbine rpms are kept more or less constant after full boost is achieved.

5) some owners remove that overboost device from their Disco

The wastegate modulator is known to fail & what some owners do is remove it and pipe the actuator directly to boost pressure. This effectively takes out the edge Discos have over Defos when it comes to boost management. The modulator is only about £12!!
On the other hand some owners install a gadget (Turbo Boost Box) that intercepts the signal from the MAP sensor to the ECU and 'hides' the overboost condition therefore fueling is not altered.

So because my turbo has an adjustment rod, I've been slowly turning up the boost and waiting for that overboost cutoff to kick in. So far I'm up three full turns on the adjustment rod. I have not put a pressure gauge on the wastegate hose yet because I haven't got a spare gauge. I suspect that the boost was initially set conservatively by the LR dealer when they put in the new turbo.

The former driver was a woman as I can see by the hole her high heels made in the floormat.

What do you guys think about my plan? Is it safe to just keep going up one turn at a time until the overboost starts shutting off the fuel? When that happens I plan to back off the rod 1/2 turn until the overboost stops kicking in.

Not much to be gained from doing this on a Disco for the reasons above explained. Boost is not about how much but about when.

IMHO it is wiser to first concentrate on 'engine health/life enhancement' upgrades (EGR removal, ProVent, reconditioning injectors, cleaning sensors, intercooler, etc.) before seeking out for performance mods.

I don't plan to remove the overboost protection until I have an aftermarket exhaust manifold with bigger studs holding it in.

No need to get a new manifold, can do the work yourself. See below.
http://www.aulro.com/afvb/good-oil/3...-charging.html

Rgds
Matt

Originally Posted by mturri

...No need to get a new manifold, can do the work yourself. See below.
http://www.aulro.com/afvb/good-oil/3...-charging.html

Rgds
Matt

I had a look see at that removed webbing bit, which looks very interesting. That post was from 2007 ... by now have we heard back on how it has held up?

Regarding EGR, I forgot to mention that I defeated it first thing.

Originally Posted by mturri

... There is a difference in the way these vehicles do boost management though. Whilst both use boost pressure to operate the wastegate actuator, the Disco does it electronically through the wastegate modulator ('modulates' wastegate actuator pressure to obtain boost pressure values that best suit that particular fueling instance). ...

I think that I understand that well now. This difference could explain the french folklore I reported about Disco/Def overpressure cutoff etc. They may in fact be depriving their Discos of advanced boost management just as you say. I will have to share that info with my LR mechanic mate.

By now I am up to four turns tighter on the adjustment rod. It does seem to me that max torque is up a bit more with every turn of the rod. Would you agree that the shorter rod means that the wastegate cannot vent as much pressure into the exhaust? So in effect, my wastegate modulator is still doing its job, but physically cannot open the wastegate fully, so max manifold pressure is up? (but not enough to trip the overboost).

Or maybe I am barking up the wrong tree.

Re the Td5 exhaust manifold work, have done dozens of these starting more than 5 yrs ago with no failures reported to date (I'm no mechanic --just help fellow Td5 owners-- so no reputation or pride at stake).

Shortening travel on the wastegate actuator rod essentially shifts the 'zero' position on the wastegate to a 'more closed' one (less exhaust gas bypassing turbine), consequently the fully open position will be a 'less open' one. This is good for low down engine liveliness but may induce it to overboost 'upstairs' under certain full boost conditions.

Not precisely sure but believe the wastegate rod in the Disco comes with 13-14 'free' threads and can be safely shortened to about 10-11 threads. Ideally one would be doing this on a step by step basis while closely monitoring boost pressure via Nanocom or HawkEye to ensure overboost does not occurr within the range of conditions the vehicle is commonly driven through.

Engine maximum torque cannot go up by simply manipulating the wastegate actuator rod, you're just making the engine more responsive by allowing the turbo to pick up revs & reach full boost sooner (call it 'earlier torque').

Keep forgetting you have a power box... which I'm personally not in favour of since in principle they cheat to both ECU and injectors. With a magic box or remap the torque vs rpm curve is shifted left and slightly upwards (more low down torque and somewhat of an increase in maximum engine torque at full boost).


Rgds
Matt

So not far from where I'm from then.

I went about 4 full turns ... 2x then tested, then went another 2x.

The Nanocom shows a max boost (standing start, foot to the floor, auto upshifting at 4200rpm) of about 19.5psi (peak). I have left it there, and have only once experienced a fuel cut/overboost in the last 2yrs since doing it (driving like a boy racer )