How do I "safely" increase my boost?

[DubDick]

okay, so I want to up the boost on my Transporter 2.5 TDi but I'm not sure how to do it safely, this is why.

My system has a boost ref pipe that feeds the ECU, I've "T" into this just before the ECU to run pipe for my boost gauge. I think this has effected the control by placing a small reservoir in the small diameter pipework which is creating a delayed reaction type scenario. If I plant the throttle at around 2,000rpm I can sometimes get a boost spike of 1bar shown on the gauge. I'm not sure if this was there before but I suspect not.

So First problem is my accidental boost spike.

Next is the ECU sets the boost at 0.8 for 2,000rpm and reduces to 0.6 as it reaches 3,000rpm and up.

So if I use a bleed valve and set it to give 1bar at high revs then I may get 1.2bar at low revs and 1.4 bar spike.

What I really want if possible is about 1 bar across the rev range.

Manual Boost Controller? - I'm not sure how an MBC would integrate with my system, as the waste gate is pressure controlled I guess it would have to bleed off the pressure applied to the wastegate - this would work for about 30 seconds by which time the ECU would have tripped into limp mode.

So I sort of need a MBC and a boost ref bleed valve. It all sound like it's going to be an absolute pig to balance but maybe possible?

So is there any sensible way of doing this without a remap?

Thanks

Rich.

[Col]

Boost spikes are quite normal, I wouldn't worry about it.

As for trying to up the boost without a corresponding increase in fuelling, I think you could easily end up damaging the engine.

From what you have described, it sounds like it is behaving normally, i.e. the boost diminishes as the revs increase. A good test is to hoof it up a long fast motorway hill, the boost should hold at 1 bar all the way up.

If you want t make it go quicker, get a remap done.

[DubDick]

As for trying to up the boost without a corresponding increase in fuelling, I think you could easily end up damaging the engine.

I'm glad you mentioned this as it's something I've never understood the need for, allow me to explain...

Firstly it's a diesel, they really don't mind running lean, in fact they do normally and also run a lot cleaner/smoke free like this. The only consequence on not increasing the fuelling would be very little power gain.

Also, the fuelling is electronically controlled and regulated via the MAF so if you increase the boost and control the heat you'll get a greater flow. The ECU will apply the appropriate amount of extra fuel to correspond to this increase unless you've already exceeded it's capacity (bigger injectors needed).

I'm also running a tuning box which allows me to have some extra control on the fuelling but not the fuel timing which is where a remap may have an advantage.

From what you have described, it sounds like it is behaving normally, i.e. the boost diminishes as the revs increase. A good test is to hoof it up a long fast motorway hill, the boost should hold at 1 bar all the way up.

Yes, I think it is behaving normally and for some reason VW have decided to tail the boost off as the revs climb. The turbo (KKK K14) is a little underspec'ed for a 2.5 but the rev range isn't that high, plus others have managed to achieve more from this turbo so I wanted to give it a go without having to resort to a remap.
Oh and it will never hold 1 bar in current set up, 0.8 is the max continuous boost and only at around 2,200 rpm. I have no idea why VW have mapped it to tail off as the revs climb, I've read that this prevents detonation but detonation is only something that effects petrol engines I believe.

[Col]

I don't quite agree with what you are saying about the ecu correspondlingly increasing the fuelling to match the increased boost.

Reason being, in simple terms a diesel engines speed is directly related to the amount of fuel going in, the boost control is secondary.

What will happen if you increase the boost without the fuelling is that the ECU will sense a fault and throw itself into limp mode.

To do it properly a remap is the way to go, a good map will optimise fuelling, boost and timing.

However...

I'd be really interested to know how you get on with this.

[DubDick]

I don't quite agree with what you are saying about the ecu correspondlingly increasing the fuelling to match the increased boost.

Reason being, in simple terms a diesel engines speed is directly related to the amount of fuel going in, the boost control is secondary.

Yes, the engine speed is controlled by the fuel going in, as is the case with any engine. What I am assuming in this case is "on throttle " condition. The ECU should be trying to produce as much power as it can so will be looking to allow full boost and supply 100% of permitted fuel for the given revs etc.

It has a simple map which determines fuel delivery according to air mass and fuel temperature and throttle position.
Is that correct?
It can also adjust the timing as well I think, and may even alter the fuelling according the the actual engine rpm. I'm not sure of the full in's and out's of it.

So the point is that if you increase the boost without letting the ECU know about it then it shouldn't trip into limp mode. Also as long as the air flow does go off the map (off scale) there should be no problem. The ECU will just sense that you have slightly higher than expected air flow and increase the fuel delivery to match. Much the same as the power increase you get with cold air.

That is if this is how it works, if not then I can forget it.

When I installed my intercooler there was definite increase in med to high speed power. This would not be the case unless the the ECU had automatically increased the fuel to take advantage of the increased quantity of air now entering the engine.

So that's my plan, step the boost up and hope the ECU will compensate. If is doesn't do enough then I can help it a little more with my tuning box.

So is the ECU clever enough to notice that the air mass no longer falls within the expected range and if so will it go into limp mode?

Will the ECU simply disregard any extra air quantity over a certain level as the standard map doesn't go that high?

These questions are what I'm hoping somebody can answer.
As well as telling exactly how to implement this
Cheers.

[Col]

Will the ECU simply disregard any extra air quantity over a certain level as the standard map doesn't go that high?

I'd say it will reduce boost if it doesn't go into limp mode. The MAP sensor would see to that. So you'd be back to square one.

These questions are what I'm hoping somebody can answer.
So is there any sensible way of doing this without a remap?


Cheers.

I wouldn't think so. Look at the Chip and Spin group buy on here, not that much money if you are pwoer hungry.

[DubDick]

Hi BigCol
Sorry, I wasn't clear. When I siad the standard map I meant the ECU's map/program. The MAP sensor is biult into the ECU on engine and has a manifold ref pipe running to it. This is where I can in stall the bleed valve so the ECU will not "see" more boost pressure than normal.

What I'm wondering about is the the signal returning from the MAF sensor as it will be much higher than the expected value. EQ expect value based on boost pressure of 0.6bar whereas the actual mass flow is a result of 1 bar of boost pressure. It could be maybe 20% higher and that could be high enough for the ECU to put a stop to it.

Hmm Chip and Spin, I'll take a look but I'm hoping to raise my boost for less than £100, maybe less than £30 if I just do a bleed valve.

Cheers

Rich.

[Col]

I'm with you now !

Bleed valve on the MAP line.

I honestly don't know the answers to your questions and have only provided hypotheticly [sp] what I think could happen.

I'd be very interested to learn what happens and how you get on.

By the way, the Chip and Spin maps are £250(ish), I think, check the thread out on here.

[Gunnar]

Only way to do it is a remap, which also makes you inject more fuel, ups the torque and smokemap limiters.

On a volvo V70 (exact same engine) that turbo does standard 1970mbar, i got mine running a "tad" higher.

[ini]

A remap is by far the best way to go.

However, if you have a pressure controlled wastegate, you can use a 'boost valve', or stronger wastegate spring to increase the charge pressure slightly.

Or you can use an adjustable MAP, or higher bar rated MAP.
It is stretching the 1-5v signal over a higher mbar range, making the ECU 'see' less boost than actual.

Without extra fueling, increasing your boost will do nothing, probably trigger 'manifold pressure deviation' faults, and could be detrimental.

Any additional fueling will increase unregulated boost, as will a more efficient intercooler (denser charge)

A MAP bleed is not good, it is best to alter power/torque parameters 'at source', and let the engine manage itself correctly.

The MAF & MAP signals are not just used as a 'control' for each other in boost regulation.

Generally if the difference is too great, you will 'limp'.