Why decat doesn't work on late MK 7

[limitedblack]

loads of vans/cars with vnt's run better and a lot cleaner with decat's

Not ours though, mainly due to fords engine management

[g-man]

sure some have been done without probs

[motorman116]

sure some have been done without probs

It has been mentioned that the turbo's that are controlled by ecu / electronic motor, loose torque when you de-cat them....

[limitedblack]

Various ideas on this, but 2 problems occur with ours, both due to engines being set up for back pressure. VNT turbo works by moving vanes in the exhaust side of the turbo, this system is there to control primary air flow, primary air flow is air flow into the cylinder, too much or too little causes wrong fuel ratios. VNT turbos were designed to give better spooling, and more constant boost (even at idle our turbos are boosting). VNT turbo control is complex due to so many parameters including EGR, temps, pressures, rpm, load, ect ect. It's not impossible to get a decat to work, but the map must control the vanes to compensate for the change in back pressure. Other issue is the ecu calculates pressure in the exhaust manifold for the vanes, again the remap would need new algorithms. Give ford £300,000 and they can fix it for us, but I don't think anyone here would

[belly]

How long before Mr Black slots in new management ? I will give a Transporter a go one day

Is this you?

Don't think so. Missing the black wheels, fly eye headlights and the private plate. Unless it's an old pic?

Yeh that's me Old pic Rumble before the Custom I was hinting at the potential design cue's of the Custom against a mk7 Why's that Limbak ?

[limitedblack]

Found it on the World Wide Web, your famous

[belly]

Linky ? Probably getting ripped by VW boys Lovelly vans but there a bit blinkered

[v8dave]

Various ideas on this, but 2 problems occur with ours, both due to engines being set up for back pressure. VNT turbo works by moving vanes in the exhaust side of the turbo, this system is there to control primary air flow, primary air flow is air flow into the cylinder, too much or too little causes wrong fuel ratios. VNT turbos were designed to give better spooling, and more constant boost (even at idle our turbos are boosting). VNT turbo control is complex due to so many parameters including EGR, temps, pressures, rpm, load, ect ect. It's not impossible to get a decat to work, but the map must control the vanes to compensate for the change in back pressure. Other issue is the ecu calculates pressure in the exhaust manifold for the vanes, again the remap would need new algorithms. Give ford £300,000 and they can fix it for us, but I don't think anyone here would

I don't know the system and what Ford are doing hence all the maybe's plus I'm thinking in print but...
It might be that the Ford management system is trying to maintain enough 'back pressure' to ensure that the egr flows from exhaust to inlet. Maybe if the egr is removed from the programming then the system can run satisfactorily when the exhaust back pressure is reduced, ie decat. It might be that the egr delete and decat can't be tuned out with the range of adjustment available in the ecu or that the system will tune but other problems will arise - maybe turbo overheating assuming the egr reduces temperature by recycling inert gases in to the inlet.
Ford will have a strategy behind their ecu program and those considering a decat and other tuning are needing a different strategy.
The ecu has measurements of :-
mass airflow - which might include intake temperature
manifold pressure - which might also include temperature post intercooler
throttle position
engine rpm
engine temperature
I don't know that it measures :-
exhaust temperature
exhaust pressure
All it can control on a non vnt turbo is fuel volume/timing and egr, for the vnt turbo the vane position is added.

[limitedblack]

I think some of it is the VTN vanes are critical to exhaust back pressure, as it is here where the map calculates position for correct boost. With lower pressure here the characteristics of the turbo must change. I have heard of other forum chats where decats have destroyed VTN turbos due to over spooling, how true that is I'm not sure.