chaffe

iTrader: (1)

Question for someone that is in the know, After putting the cat back on my car it is running less boost, understandably there will be a small restriction now in the exhaust, but IMO this should not decrease the boost. As i see it the ECU will want to achieve target bost of 19 psi (as before) And so should bled off enough air unril this boost is reached, regardless of backpressure. As a test i bypassed the factory boost controller and used a bleed valve, and yes the car can pysicaly run 19 psi in this manner. So my next train of thought was that i may need to "help" the factory bleed valve as it prehaps cant flow enough now, so i installed a restricor from the compressor housing, no change.
This leads me to the conclusion that somehow the ecu thinks it is reaching target boost, so i can only assume that the ecu does a calculation through the air mass meter? Or is there a seperate map sensor for this? thanks in advance.
BTW not interested in people telling me it needs a remap, I am quite capable of checking the AFR and for DET, thanks.

chaffe

iTrader: (1)

Prehaps the actual boost pressure needs to be calibrated to the ecu's calculated boost now the ve has changed? assuming it is a calculation made from the density and mass?

tjmatt

iTrader: (1)

Since you have had no replies, I'll reply. Assuming it is similar to the late classic ECU's there are target boost pressures vs load and rpm, as well as initial duty cycles vs load vs rpm. They have a MAP sensor which is used to measure manifold pressure. The ECU uses the initial duty and makes corrections until the target boost is achieved. I do not know if this is done with a proper feedback loop, and instantly, but I would imagine these take some time to amend. I think this because I remember adjusting the pre-load in the wastegate spring, seeing some more boost and then it soon backed it back off to where it was. This didn't seem to take more than a couple of blasts from what I remember. However if you can reset the ECU perhaps it might learn faster? How much less boost do you get? The duty cycle required for a particular boost will vary dependant on gear, and normally you will see less boost in lower gears because the ECU does not adapt fast enough and the duty cycles with be such that you do not get overboost in the higher gears. It may even be that its all working as expected but you were seeing some spiking and overboost before.

chaffe

iTrader: (1)

Thanks for your reply, It now makes around 14 psi, which is considerably less than the 19 peak and 18 hold before. I dont want to just put on a bleed valve and set the boost manually as then the ecu has no means to lower the boost if something is amiss. I see what you are saying about its adaptability, but it has had a few weeks to adjust. Where is the map sensor and where does it take its boost reading from? It does seem a strange one, the map toggle still works and i can change from hi to low no probs, do you prehaps think that more wastegate tension is required?

tjmatt

iTrader: (1)

4 or 5 psi sounds like quite a lot different, I would have thought maybe 1 or 2 psi max.

Is it possible the cat is blocked? Or you have a small boost leak, or uppipe leak after working on the car?

Its possible the duty aim tables are too low for the new setup, and target boost cannot be attained. In this case, adding more pre-load to the wastegate actuator may help you somewhat. Similarly you should be able to achieve the same with a smaller pill in the pipe coming off the compressor. However I find it hard to believe if it was all as it was, using similar duty cycles to those it did before that it could be 5 psi lower.

MAP sensor on my99 is not far away from the boost control solenoid, feed coming off the inlet manifold, not sure where it is on your car.

chaffe

iTrader: (1)

Not the cat or up-pipe mate, had the whole manifold off on the weekend for new gaskets and a wrap in heat wrap (tubular item) Boost leak was my next port of call, but then would it make the numbers with a manual controller if this was the case?
I also see what you are saying (highlighted in bold) i have put a restriction in the compressor pipe and it made no odds, prehaps this needs to be a smaller hole? any idea on size? (im using a manual bleed valve, utilising two ports only, one side and one bottom) so am i right in thinking that if it made 19psi at 60% duty cycle before it will not want to make 19psi at more than %60 duty cycle now? is that what your saying? thanks

tjmatt

iTrader: (1)

Having read the bottom of this page: http://www.ecutek.com.au/ecu-tuning/...ecu-comparison, I think the closed loop boost control should home in quite fast, and duty aim too low would not affect the final boost pressure. It is possible that the actuator it already on max duty and cannot go higher, and therefore you need a smaller pill in the pipe. Why it would be so different to when you had no cat in I do not know. Normally you would need a tiny fraction higher duty cycle to make up the difference in boost pressure caused by having the cat in place.

If you had a VAG COM cable you could log the ECU parameters and you would be able to see what duty cycle the solenoid is operating at.

tjmatt

iTrader: (1)

... You would also be able to read the Manifold pressure as measured by the ECU and check it tallies with the boost gauge (rule out dodgy map sensor and wiring).

chaffe

iTrader: (1)

thanks, i do have vag com, thanks again for what you have said. What program will i need to read the live data?

jura11

iTrader: (7)

Download EcuFlash or RomRaider for reading live data.


Jura

chaffe

iTrader: (1)

can you read the data if i have ecutec though?

jura11

iTrader: (7)

I think yes.

Jura

chaffe

iTrader: (1)

Ok, so i guess what can i do if the figures are wrong lol, nothing without spending 300 quid for somone to tweak the boost map, and tbh i would rather megasquirt the car than spend £300 for someone to remap it, it would be cheaper and ultimatly more tunable (ie I could tune it!) Bleed valve it is then! thanks for the help guys, if anything ive learnt something new

jura11

iTrader: (7)

I'm afraid yes,you have few options get your car mapped via OS tune,which is cheaper option(if your car is not mapped),or contact EcuTek dealer(Simon,Bob Rawle) which can adjust your map(tweak) for extra cash.

If you are thinking for Bleed valve,i would have look for used AVC-R which is best Boost controller.



Jura

dynamix

iTrader: (3)

By putting the cat back on you are making it almost impossible for the turbo to hit its boost target even with a bleed valve on it using the mapped wastegate duties. The increase in back pressure will be huge compared to what it has been mapped for and will pretty much require a 100% duty to run that boost. But I wouldnt be in a hurry to make that boost without changing/checking fuel and det and would recommend a before and after dyno run to see whether running higher boost has actually got more power. It doesnt always work that way.

Midlife......

iTrader: (2)

By chance it hasn't reverted to a possible second map running a restricted boost..... (the old WOT and rear heater trick)

Shaun

chaffe

iTrader: (1)

no, but thanks for the thought

chaffe

iTrader: (1)

Thanks for the informative post, increased wastegate preload or a restriction to the "T" peiece would help surley? It does feel faster and can achieve the boost with a manual controller, so must make more power (must be more than 20 bhp before you can feel it) As for the AFR, ive got wideband to monitor that, and there is no det (the std ecu makes a very good joib of keeping an eye on that) thanks for your concerns, BTW the cat is off a 2006 2.5 wrx, sureley it can flow my lowly desired 260bhp? wouldnt think it would be that much of a restriction? only trying to keep the car legal, i have the decat at home, would only take an hour to swap it.

ukpaisley

iTrader: (4)

So to claify , the ECU has a boost map that is adjustable within margins, but its not closed loop like a standard electronic boost controller.

chaffe

iTrader: (1)

AH! now i see when its said like that! so in theory I can increase the boost by fitting a smaller pill, as the duty cycle will not change on the solenoid due to it getting no feedback.

ukpaisley

iTrader: (4)

Need someone who mapps the ECU's to confirm this, this is why I think the restrictor pill and the like is bad news as you can change the pressure curve of the boost pressure.