Thread: VNT TURBO FEEDBACK PLEASE

Originally Posted by OffTrack

The Disco Td5 ecu is programmed with a maximum boost limit of something like 22psi. If the ECU detects a boost level higher than this it limits fuelling until the boost drops to acceptable levels.

Is the normal boost limit an absolute limit for all driving conditions? And so, does the boost box "fool" the ECU for all conditions or only for low rpm?

What is the risk of damage if you run with boost over 22psi?

The risk of running too high a boost is that it will stress the engine, head gasket would be one of the first areas to consider. Boost and more fuel to make use of the boost while keeping EGTs under control.

I don't know what the boost box does below the max boost, if it is smart it will only come into play at over boost situations. Although having the ECU think it is running lower boost than it actually is when below the max boost will not affect things. Unlike petrol engines, diesels don't have to run close to the stoichiometric fuel air ratios.

Hello,
I am on to the inter cooler..........thanks

The boost boxes I have taken apart are a slow bleed to earth which means they are bleeding volts all the time. i did notice a difference when i removed the one I had, much better. The volt switch I made only comes on when the boost gets high enough to go to limp other wise it runs normal readings, . Yes they do make the the ECU only see the volts just before limp mode.... you can call it fooling the ecu ...you take the risk for the extra power .....depends what you want.
Mine does peak at around 22ish PSI but will settle very quickly at around the 18psi it is set to. I do enjoy the extra power I have..........every day.
Ian

Hi Bronson
Have a Turbo technics VNT and boost box and super large PWR intercooler fitted for about a year now, GOt a custom BAS fuel map done. Also fitted on JC's advice an upgraded Ashcroft torque converter to auto.

Initially got really high egts without intercooler. Had a re-jig of the fuel map for slightly lower fueling up high in revs. Turbo and boost box was less landed here from uK than a standard LR turbo!!!

The driveability and instantaneous response is phenomonal (that doesnt look right). Beats my old D1 auto with hi comp 4.6V8 hands down. Wrinkle the big tow and wooshka.

Fuel economy is roughly about the same, hard to tell cos I can't resist giving it a boot full. Just did a quick return trip Melb to Sydney, on cruise 110km and avergaed that and got 10.5L/100km. Towed a 1t camper all over Oz and consistently recorded between 11.8-13.8L/100km over all conditions. IMHO the HD TC is a must have with a VNT to translate the low down torque and boost into oomph not revs. Am considering a modded MAF as occasional overboost if I get a bit crazy. Have done a bypass hose around MAF as a fix that works most of the time.

Its seriously a much better drive than my son's new Ford Ranger. Hope this helps. JC did all the work, all credit to him. Max (Hobart)

Hi Silverhammer

Cheers for the reply, just gotta get the bickies and i'll be on my way i reckon.
have you got an EGT gauge fitted also? Whats a safe level to have the car running at Re: EGT ?
Wont have to worry about the HD TC as mine is a manual.
Have you had any dramas with the boost box? What brand did you go for?

cheers
Luke

BAS supplied the turbo. map and boost box. Have had some persistent overboost till I put in the hose bypass of the MAF. Simple fooling of the MAF. Using a boost gauge on manifold pressure, max boost is 24psi but comes in about 1400rpm.

Yeah got an EGT pre turbo. Took advice from Peter Bell BAS UK on EGTs. The turbo can handle 800 as a momentary peak, but treat 750 as the regular redline for peaks and he says all is good. However these temps are not to be maintained under sustained loads. In my experience, motorway cruising sees EGTs at 380-480 ish, big long hills 550 to high 600s, and Pete says this is entirely normal, will have no detrimental effects. I tow 1t camper at 100kmh with EGTs 420-550 covers most terrain except big long hills. The big intercooler means the temps drop very rapidly. This is important as the EGTs are brief intermittent fuel burns not heat sunk or absorbed into the manifold and turbo.

Hope this helps. Cheers

Max

Has anyone on here had any problems with the S208? I have been running them for over 2 years now and have had 2 different problems. Never a complete failure but enough to warrant a rebuild.

Never any problems getting them resolved but wondered if others had them fail and what the failure mode has been?

I have been following with interest the discussion on VNTs and related means to improve the performance of my Td5. I’d like to check my understanding gleaned from the knowledgeable people here, to see if I have it right. The performance improvements are from the perspective of a manual Td5.

1. Mandrell bent exhaust
This replaces the standard exhaust system below the outlet manifold and may or may not retain the cat. Pipe diameter may be 2.5” or 3”. This reduces the exhaust flow resistance and allows the turbo to spool up more quickly. It provides a noticeable but small power improvement at low to medium rpm but little if any difference at high rpm.

2. Boost box
Electronic device intercepting the boost signal to the ECU to fool the ECU into thinking the boost is within normal operating parameters. I assume there is some way of setting the boost box operating settings to limit that “fooling”, so engine isn’t damaged. When used by itself it makes little difference to spool up lag but provides a noticeable power difference at all rpm after spool up. Results in higher average exhaust temperatures which can be risky.

3. Larger intercooler
Achieves better cooling of the compressed air from the turbo before entering the inlet manifold, which allows more air to be forced in. [Some posts suggest it reduces exhaust gas temperatures but I thought the exhaust gas didn’t go through the intercooler?] No change to spool up lag, minimal power difference at low rpm, better power performance at medium to high rpm.

4. VNT
Varies the physical characteristics of the turbo with rpm to allow it to spool up quickly at low rpm (around 1200) but not to overrun at high rpm. Not necessary but often used with boost box and larger intercooler to realise greatest overall performance improvement. Not necessary for fuel map change but will improve things further.


Thus, if I just put in the VNT I will lower the turbo kickin point and get better low end performance? I can put in a boost box and a bigger intercooler later as I can afford it.

Comments, corrections and advice would be greatly appreciated.