Aftermarket Boost Management

[s2_wot]

Posting on behalf of Mick "irish"

The car has been in the hands of a jap scrap tuner and now has a whizzey box located under the steering column that was placed there to control the boost. There's a maze of small guage piping in the engine bay including a connection to the upper port of the wastegate. I suspect the N75 has been disabled / removed. Anyway my initial thoughts were to have all that stuff removed and the car put back to standard.

However having gone for a brief spin in the car it feels strong and I was wondering is there any way to verify if the current setup is safe to run?

Is there anything that could be logged during driving using vag-com or should the stuff be just ripped out?

[Tonks4x4]

I would think the obvious ones that can be checked are AFR, Boost and EGT through after Market gauges.

[prj]

The reason it is much less safe compared to stock, is that it does not pull boost when the engine knocks.
So it will merrily boost as much as programmed to, even if you get heavy knock.

And you can get heavy knock just from the MAF-Turbo hose leaking or a breather hose giving up the ghost.
If you want that flat "strong" feeling, I can send you a file with that for the stock ECU
The most I could drive with that setup was 10 minutes, home from the airstrip and then I got annoyed already. Especially with the stock turbo.

[DJones]

The reason it is much less safe compared to stock, is that it does not pull boost when the engine knocks.
So it will merrily boost as much as programmed to, even if you get heavy knock.

And you can get heavy knock just from the MAF-Turbo hose leaking or a breather hose giving up the ghost.
If you want that flat "strong" feeling, I can send you a file with that for the stock ECU
The most I could drive with that setup was 10 minutes, home from the airstrip and then I got annoyed already. Especially with the stock turbo.

Whilst you do loose the (factory) safety factor with an aftermarket set up would the knock sensors not retard timing prior to the heavy knock you describe..

The good aftermarket set ups have their own over boost facility that will halve the boost instantly if the maximum pre set level is reached.

Personally i would find out what is fitted and how it is operating prior to removing it.

[Dan]

My gut feeling is it's kinda risky - you don't know what this black box is doing / trying to do and as prj says, could just be holding on boost regardless of knock etc.

Far better to run through the ECU/N75 and have it mapped properly.

[s2_wot]

My concerns were mostly about the knock detection and also perhaps the car is running lean with more air than the ecu is prepared for.

I'm no expert but the car feels like the wastegate is closed all the time. With any of these cars I've driven / been a passenger in if you got to full throttle or close to it from low rpm you car hear and feel the wastegate fluttering via the N75.

With this car it feels more progressive once it begins to come on boost and there seems to be nothing to restrict or cut the boost to suit the fueling.

Maybe someone put a 1 tonne spring into the wastegate or something like that. When you come off the throttle there is a tissss noise from a dumpvalve that was fitted too.

[HMS-S6]

I would think the obvious ones that can be checked are AFR, Boost and EGT through after Market gauges.

Is there a good place to buy these from? Roughly what would they set you back?

[mcandmar]

I would be concerned about the fuelling too, if they did the boost management the dirty way god knows how they went about adapting the fuelling to suit. If it were me i would rip all that crap out and revert to stock. No point messing around with a stock setup. The real question is did they do anything to the ECU?

[newsh]

Is there a good place to buy these from? Roughly what would they set you back?

Google Vems Round

[Dan]

VEMS is great for what it is, but if the guy just wants a non-dodgy car again, rip that sh*t out, go back to stock ECU and get it properly remapped.

[s2_wot]

I would be concerned about the fuelling too, if they did the boost management the dirty way god knows how they went about adapting the fuelling to suit. If it were me i would rip all that crap out and revert to stock. No point messing around with a stock setup. The real question is did they do anything to the ECU?

The ECU was played with, damaged and put back to stock.

if the guy just wants a non-dodgy car again, rip that sh*t out, go back to stock ECU and get it properly remapped.

I think the route he'll have to take is pull those aftermaktet modifications out and get a safe chip put into the ecu. Then enjoy the car for what it is safe in the knowledge that any other problems could be sorted.

[prj]

Whilst you do loose the (factory) safety factor with an aftermarket set up would the knock sensors not retard timing prior to the heavy knock you describe..

Retarding timing alone does not always save you. That is why motronic pulls boost as well.
The timing retard is mostly so, that you can run on 95 RON fuel. The boost cut is to save people from destroying their engines.

My concerns were mostly about the knock detection and also perhaps the car is running lean with more air than the ecu is prepared for.

Yep, this happens on stock AAN past ~1.45 bar. And without the possibility to pull back boost no amount of timing retard will save you

[s2_wot]

Retarding timing alone does not always save you. That is why motronic pulls boost as well.
The timing retard is mostly so, that you can run on 95 RON fuel. The boost cut is to save people from destroying their engines.


Yep, this happens on stock AAN past ~1.45 bar. And without the possibility to pull back boost no amount of timing retard will save you

it's fair to assume that the car is running 95RON. if we assume the wastegate is closed at what RPM would the compressor make 1.45 bar? I know that will depend on load etc

If the car must be driven I suggested no aggressive accelerating and not passing 5000 rpm but I have no real technical basis for this.

[prj]

it's fair to assume that the car is running 95RON. if we assume the wastegate is closed at what RPM would the compressor make 1.45 bar? I know that will depend on load etc

If wastegate is fully shut you will instantly make 2+ bar and break your engine.

On stock spring the wastegate opens due to backpressure at about 1.6 bar @ 3000-4000 rpm and 1.1 bar at 6000 rpm from my experience.

[irish]

hey

thanks for info lads, i have taken car to place where he says he can remove all sh*t that was put in, so maybe it run as it should when done, as long as ecu is not doctored