Thread: Raising boost on a td5

Originally Posted by SPROVER

Are you sure it's not going into over boost? Mine will Rev freely to 4000 if i really want to push it. But i run a boost box and 23 psi.

Possible, but when I tweaked up to this range before it would just go into limp mode, never this kangarooing thing, it is like some kind of limiter, I will back off a turn or two and report back.

Check the pipework connected to the wastegate modulator and if it's OK take the pipe from the modulator's bottom and connect it directly to the wastegate valve...if it'll run OK this way you need a new modulator

Check the pipework connected to the wastegate modulator and if it's OK take the pipe from the modulator's bottom and connect it directly to the wastegate valve...if it'll run OK this way you need a new modulator

Just to clarify an earlier post on this thread, my understanding of the modulator is that it is like an electronic "Dawes valve" in that it prevents air pressure getting to the wastegate diaphragm until 15PSI , to reduce wastegate creep and therefore increase boost at part throttle.

IE it has an electronic valve inside that is closed until the ECU senses 15PSI, presumable from the MAP and then it opens.

My boost is now about 20-20.5 PSI and I have no surging etc after 15PSI, although it sdoes seem to hit 20.5 then drop back about 0.5 PSI.

Regards Philip A

Thanks for the help. I set to work at the weekend and discovered I had not clipped the MAF sensor back after doing some remedial work after my boost gauge stopped working when one of the pipes to the modulator had come loose.


Hadn't noticed much difference to performance without it, so was guessing it was this that was causing the "kangarooing'. Since I have cleaned up the MAF and MAP with contact cleaner and would the boost back down to 19psi. The car is definitely running better generally, but still not satisfied on the 3,000 rpm rev range.


Yesterday I was pulling onto the Eastern Freeway, put my foot down and watched the revs and boost, again it got to 2,850 rpm and boost at 19psi and then slowly nudged it's way to 3,050 which took about 4 seconds with very little increase in speed, it then changed to 4th and whoosh, in no time I was at 115kmh.


Obviously once it changes gear to 4th, we are back in the turbo range, hence the band of acceleration I am guessing. Is this normal for an auto, I think not ?


I am not a foot to the floor driver at all, I know I can trip the over-boost if I put foot to floor going up one of the very steep hill round where I live (if anyone knows Warrandyte they will know what I mean), but choose not to as it is just not worth the effort to achieve a very small increment in speed, and this also means winding the boost back further.


What to do ..... ??

I just reread this thread and although I am not a good proof reader, I think you do not mention having a look at the fuel pump and filter.

If the car has had the washers changed in the injectors, it is usual for the filter at the base of the fuel pump to be blocked up with black crap.

Have you changed the fuel filter?

Another possible mechanical problem is that the basket filter in the head under the fuel pressure regulator can get blocked.

The TD5 auto in EU3 form should rev to 4200 RPM before change. When stock the last 1000 is pretty tedious but with increased boost and map , they go pretty well.
Regards Philip A

Right, a couple of things, the performance when in 'the range' of torque as you have found is one thing.

I fitted a new Torque Converter from Torque Converter Technologies in Melbourne (TCT), it has a larger lock up clutch and locks earlier (lower revs) than the standard one. This has helped keep the engine in the 'rev range'.

It does not alter gear change points but as the TC is locked it helps.

I have for a long time wondered about the pressure take off point for the turbo pressure reading, it appears to be in the vicinity of the turbo, my thinking is that if the reading was taken from the back of the intake manifold all the resistance and delays caused by the intercooler and plumbing etc would be taken out of the equation and a truer perhaps slightly quicker performance could be had with very little else done.

Right track or??????

Cheers, argue/discuss on.

Mike

Originally Posted by nismine01

I have for a long time wondered about the pressure take off point for the turbo pressure reading, it appears to be in the vicinity of the turbo, my thinking is that if the reading was taken from the back of the intake manifold all the resistance and delays caused by the intercooler and plumbing etc would be taken out of the equation and a truer perhaps slightly quicker performance could be had with very little else done.

Right track or??????

Cheers, argue/discuss on.

Mike

IMO the relevant pressure reading is as close to the engine inlet as possible cos that's what the engine gets in reality, the MAP sensor is exactly where it should be from this point of view, measuring boost near the turbo while you are not certain it gets untill the inlet might not help too much if you see what i mean