Thread: Boost pressure

Thanks Lemo.

Just did the bypass, and it's good to go now(ie. no surging)

Only have a nanocom to check boost pressure and it works on Bar values .. which makes no sense to me(PSI is more like my language).
IIRC the Td5 can run 1.42 or 1.45 Bar or so? I'll adjust the rod to suit whatever is just below max.

engine has got very good torque and pull up to about 3250RPM where it seems to tail off a little, but can rev more if needed, but up to 3250 it pulls much harder than the V8 except off idle(of course).
Boost comes in below about 1500RPM too(much nicer than the Tdi ... )

We have no history on the car and whether a previous owner has mapped it.
Going by how torquey it feels compared to a couple of other TD5 D2's driven, I reckon it's been mapped(so that's a new quest to work out too).
Car is heavily modded(lockers, lift, winch, and stuff) .. but no CDL, so I'm assuming a previous owner did some stuff, maybe not very well thought out tho(eg. winch wiring is a shambles).

if it is mapped, we have no EGT gauge to work out if it's running high.
Only consolation with that is that it blows no smoke at all even at full throttle up to 3500RPM(that I'm willing to take it too). Only a very short puff at startup only.

Now the hard bit(for me) is to convince bro to part with some money and get these damned gauges!
ps. he's got the money .. makes double what I do .. just can't get him to spend it on stuff he needs!

I'm fairly sure that few people actually know how the waste gate control on a TD5 works, and every time I see much of the advice in this thread the more I'm convinced its wrong, the guru on this topic is Offtrack, from reading his posts and website and doing my own experiments, here is my understanding (which may also be wrong)

Firstly bypassing the waste gate modulator will do nothing to increase boost, because the entire function of the WGM is to INCREASE boost, its incapable of reducing boost (unless its just reducing the amount by which it is increasing boost) but if its faulty then it wont increase boost...unless the fault is a blockage.

Bypassing it will just slave the waste gate valve to the turbo pressure, however, it will give you the ability to manually increase your boost pressure by messing with the waste gate screw.

Note, messing with the wastegate screw whilst the WGM is in place will do little to increase your boost pressure.

The max Normal turbo pressure on a TD5 is 1.19BAR or abut 17.2PSI, this is controlled by the ECU, if the boost is low then the ECU closes the WGM to isolate the Waste gate valve from the turbo pressure which will INCREASE boost pressure, if the boost pressure is high the WGM will do nothing and let the turbo pressure go directly to the Waste gate valve open the wastegate and REDUCE pressure.

So, just bypassing the WGM will mean the ECU cant choose to dial in more pressure, and just messing with the wastegate screw will mean that the ECU wont try and dial in more pressure.

Doing both will give you more boost pressure, but give you a fairly dumb (simple) turbo control

The *correct* way to increase turbo pressure is to change the WGM target boost table in the ECU map, this table cross references throttle position and engine RPM to select a target boost pressure, then the WGM fires to achieve this pressure.

turbocap.PNG

So, in conclusion if your boost pressure is 18PSI then congratulations, it sounds like your engine is working correctly!

Thanks for that additional info too.
I've been reading Offtracks and Sierraferry's comments re the WGM and wastegate control.
For my immediate needs tho, to get my bros TD5 not surging, al I'm interested in is where to start looking and what to mod/disconnect/etc .. just to locate what is doing what.

So the WGM bypass for now at least hase proved to be effective to locate the source of the boost surging, and inability to get past about 2750RPM.

Now with his info, I can advise bro on what we should do next.

And reading up on Offtracks webpage at TD5.com I'm getting a better understanding of it all too now.

My thoughts at he moment are to go with the std WGM and wait for Offtrack to complete his findings on the mapping and then maybe even convince my brother to purchase a well sorted out map.
Or, go with a D-Force controller now, and setup some turbo pressure memories(it holds up to 6) and use them as required.
We're not looking for tyre shredding power or torque, just enough power with reliability and economy.

The only 'problem' with the GFB boost controller is that it doesn't work on pressure values.
You set up your required boost pressures using only duty cycle values in percentage terms(which mean zip to us non duty cycle types ), so you have to set some values up in the memory banks and take it for a test drive and watch the boost gauge.
If it's too much, then switch to the next memory. if too low, then change again.
The only boost value it does give tho is the overboost control(where it maxes out). Everything else is a learning curve.

And I was unclear on my question re boost values.
What I should have asked is what is the max or overboost value that the ECU measures when it spits out the error or shuts down the fuelling or limp home mode setting or whatever it does.
That is, if it's at say 22PSI, or if that correlates to that 1.45Bar value I've seen every now and then, if he decides on the GFB controller, then I'll set it's max boost to shut off at just below the Landrover value.

If it weren't for the two gauges on the GFB, I'd be less likely to suggest it to him anyhow.

he's not really interested in a 1Gauge like I have in my D1.

I'm no expert and my comments were based on AK83 asking re the bypass of the WGM and if it was functioning and along with the MAF, was posting short replies on a busy weekend and should have added to my posts that was the case.
So apologies I'll endeavour to be more precise in the future.

There's also a few threads by OffTrack that explain the correct operation of WGM, sorry can't locate them on the iPhone.

I'll link them up tomorrow for future reference etc.

Cheers all and have a great Sunday, Lemo

Here's a few links, had a coffee after 9pm so no sleep for me!!

TD5 waste gate actuator operation

Wastegate Modulator - testing and unpowered behaviour?

OK, I have tried two different MAF sensors, 1 from my old car (I know it was good, not saying is good) one from the beast I drive now. Both give me the same on road effects, surging, turbo pressure up and down, thinking it was over boost I backed off the waste gate rod (I had previously screwed it up), the lower I set the boost the more the fluctuating turbo pressure and surging, though less vicious.

I have now disconnected the MAF sensor and the car drives like it should occasionally reaching 20 PSI but generally running (under load) around 18 PSI.

This would seem to indicate both MAF sensors are cactus. I will get out and check them eventually but as the car is running so well I am inclined to leave the MAF out of the loop altogether. I'm sure someone will come along and tell me the error of my ways!!

My test track has always produced a drop of ten KPH but as the car is now it only dropped five KPH and felt good.

Now to find someone to remap the ECU and I will be like a pig in the brown stuff.

Cheers

Mike

Originally Posted by AK83

Thanks Lemo.

....... it works on Bar values .. which makes no sense to me(PSI is more like my language).
IIRC the Td5 can run 1.42 or 1.45 Bar or so? I'll adjust the rod to suit whatever is just below max....

1 Bar = 1 atmosphere at sea level - 14.5038 psi

Originally Posted by donh54

1 Bar = 1 atmosphere at sea level - 14.5038 psi

Actually 1 standard atmosphere (atm) is equal to 101 325 Pa (pascals) which is 1.01325 bar. Bar is basically shorthand for 100 000 Pa.

I assume this is because we have kilo (x 1000) and Mega (x 1 000 000) for kilopascals and megapascals, but there is no metric prefix for (x 100 000).

We get this number because (like most things in the metric system) 101 325 Pa is the mean atmospheric pressure at the mean sea level at the latitude of Paris, France (thanks Napoleon for conquering so many nations and giving us a logical system of standardised measurement! If only you had given us a useful prefix for 10^5. Maybe bar- can work? barpascals? barmeters? bargrams? barseconds? barlitres?).

A pressure of 1.01325 bar is a force of 101325 Newtons applied to an area of 1 square metre. This is the same force as if gravity was pressing a 2000 kg elephant onto an area of 0.2 square metres - about area of a human torso. So when you are running at 1 bar of boost, you should feel an elephant pressing on your chest.