Bug Eye WRX PPP - low boost
Discussion
Noticed a few weeks back that the car didn't feel as fast as it had done previously, as I'd just acquired an OBD dongle I did some logging and found that I was only getting 0.6 bar of boost rather than about the 1.1 I'd expect from the PPP map. Double checked the MAP sensor's figures by plumbing in a separate boost test kit which confirmed the readings from the ODB, thinking I might have a boost leak I gave the car to my mechanic to pressure test and it all came back good.
Next thought was to try the boost solenoid so I picked one up off ebay and fitted it, after jump starting the car (stupid battery went flat while it's been parked up
) I took it out for a run with the OBD on, initially I was only seeing 0.7 bar but after 20 mins or so of driving I did another run and saw 0.8, a further run and I was seeing 1 bar which is encouraging if a little shy of the aimed for figure. What I'm wondering is whether the flat battery means the ECU was in some kind of learning mode and slowly increasing boost as I drove or whether I've still got issues?
Other things to throw in the mix is that the last round of work the car had done was to correct a couple of exhaust leaks - most notably the up pipe was shagged and I replaced it with a decat item - I don't have any readings to confirm but I'm pretty sure that immediately after this work and for a good couple of weeks afterwards it was boosting correctly. I'm going to do some more running over the weekend and see if I'm now consistently getting this 1 bar figure but in the meantime has anyone got any suggestions?
Next thought was to try the boost solenoid so I picked one up off ebay and fitted it, after jump starting the car (stupid battery went flat while it's been parked up
) I took it out for a run with the OBD on, initially I was only seeing 0.7 bar but after 20 mins or so of driving I did another run and saw 0.8, a further run and I was seeing 1 bar which is encouraging if a little shy of the aimed for figure. What I'm wondering is whether the flat battery means the ECU was in some kind of learning mode and slowly increasing boost as I drove or whether I've still got issues?Other things to throw in the mix is that the last round of work the car had done was to correct a couple of exhaust leaks - most notably the up pipe was shagged and I replaced it with a decat item - I don't have any readings to confirm but I'm pretty sure that immediately after this work and for a good couple of weeks afterwards it was boosting correctly. I'm going to do some more running over the weekend and see if I'm now consistently getting this 1 bar figure but in the meantime has anyone got any suggestions?
Vixpy1 said:
Get someone with Delta Dash to plug in and reset the ECU, and check the MAF voltage when ign on, but not running
Don't know anyone with DeltaDash 
Also I'm guessing the flat battery will have reset the ECU?My OBD kit is a bluetooth dongle with Torque Pro, not sure if it can read MAF voltage or not - will investigate over the weekend. Should probably have mentioned that there are no fault codes logged on the ECU
Didn't manage to get any more logs over the weekend although driving it on Sunday morning it once again felt down on power according to the butt dyno. It's booked in for a proper diagnostic session with a local specialist this afternoon - from describing the problem to him over the phone he seems to think that like ScoobieWRX suggested that the ECU has detected a problem and is pulling boost.
Probably time I updated this.. Car had a diagnostic session with a local specialist on Saturday and after plugging in and running it on the dyno he said that despite actually making quite decent power (261bhp at the fly) "it's knocking it's tits off" and that he thinks the likely cause is ringland failure
He also plumbed in his boost gauge and determined that it's not agreeing with the MAP sensor, suggesting that this might have failed as well.
At this point I really don't know what to do with the car now - if it is ringland failure then fixing it is anything from a piston swap to a full rebuild apparently, and with an initial quote for full rebuild coming in at £3k that doesn't sound feasible
He also plumbed in his boost gauge and determined that it's not agreeing with the MAP sensor, suggesting that this might have failed as well.
At this point I really don't know what to do with the car now - if it is ringland failure then fixing it is anything from a piston swap to a full rebuild apparently, and with an initial quote for full rebuild coming in at £3k that doesn't sound feasible
I think the rebuild quote in question was including forged pistons to be honest - it did feel a little high even then though. My usual mechanic said he's going to have a think and give me a ballpark for how much he'd charge to do it but I'll check API out as well, even if I get my guy to do the build they might be a good source for parts! 
As for how he detected knock I think he was using detcans (he definitely had some sort of headphones on anyway!), my ears can't really hear anything unusual externally and neither could he the other week. I'm not sure why his gauge was reading different to mine - I know he plumbed in to a different place than I did when I did it which might make the difference. The boost readings he showed me from the MAP did look to be erratic in places and didn't seem to tie in with what he was seeing mechanically. Also the car was clearly making more than 0.6bar to record 261bhp!
As for how he detected knock I think he was using detcans (he definitely had some sort of headphones on anyway!), my ears can't really hear anything unusual externally and neither could he the other week. I'm not sure why his gauge was reading different to mine - I know he plumbed in to a different place than I did when I did it which might make the difference. The boost readings he showed me from the MAP did look to be erratic in places and didn't seem to tie in with what he was seeing mechanically. Also the car was clearly making more than 0.6bar to record 261bhp!
Pretty sure he plumbed his gauge into the Inlet Manifold and he was saying that he was seeing 1bar on it when the MAP sensor was showing 0.6 (apparently the MAP did occasionally show 1bar), as for the power figure I'm obviously not sure how accurate the Dyno was - the last time my car was on the same rig it made 253 IIRC which sounded about right and that was essentially the same setup but with the OEM up pipe in place, like yourself I'd be very shocked if it was making anywhere near that with 0.6bar.
As he described it to me the ECU was seeing 0.6 bar and was pushing the boost solenoid duty to 75% all the time trying to get higher boost then as it was getting det it was winding the advance back. I'm not sure how on the level the guy was - several people have said he's a decent guy (including David @ API) and given I was quite prepared to pay for him to map the car on the day if it needed it I doubt he was trying to sell me a map as I was already pre-sold as it were I'm thinking I need to trust he was being honest even if he hasn't correctly identified the issue.
The plot has thickened somewhat in that I spoke with the guys at API yesterday and they seemed to think that it would be highly unlikely to be ringland failure as this wasn't a common issue until the 2.5 engine, they do however think that it could easily be the beginnings of a crankshaft failure or HGF or similar.
At this point I'm honestly at a loss of what to do next - wondering whether it is worth getting a secondhand MAP sensor off ebay and swapping that out and maybe doing a leakdown/compression test?
As he described it to me the ECU was seeing 0.6 bar and was pushing the boost solenoid duty to 75% all the time trying to get higher boost then as it was getting det it was winding the advance back. I'm not sure how on the level the guy was - several people have said he's a decent guy (including David @ API) and given I was quite prepared to pay for him to map the car on the day if it needed it I doubt he was trying to sell me a map as I was already pre-sold as it were I'm thinking I need to trust he was being honest even if he hasn't correctly identified the issue.
The plot has thickened somewhat in that I spoke with the guys at API yesterday and they seemed to think that it would be highly unlikely to be ringland failure as this wasn't a common issue until the 2.5 engine, they do however think that it could easily be the beginnings of a crankshaft failure or HGF or similar.
At this point I'm honestly at a loss of what to do next - wondering whether it is worth getting a secondhand MAP sensor off ebay and swapping that out and maybe doing a leakdown/compression test?
Thanks for all your continued help Scoobie.. I'm going to definitely owe you a beer at this rate!
What you're saying about the MAP does make sense, worth investigating at any rate - I'm guessing even if the MAF is metering the air coming in correctly it will still fuel based on the boost it sees at the MAP?
Is the MAP sensor the same between the WRX and the STI? I've seen this on ebay and wondered if it was worth picking up to try it?
Compression test does sound like a good idea as it would hopefully show up underlying mechanical issues? I'll speak to my trusted mechanic and see if he can fit me in.
What you're saying about the MAP does make sense, worth investigating at any rate - I'm guessing even if the MAF is metering the air coming in correctly it will still fuel based on the boost it sees at the MAP?
Is the MAP sensor the same between the WRX and the STI? I've seen this on ebay and wondered if it was worth picking up to try it?
Compression test does sound like a good idea as it would hopefully show up underlying mechanical issues? I'll speak to my trusted mechanic and see if he can fit me in.
Thread resurrection time!
Finally got round to having the MAP sensor changed on Saturday and shock of the day I'm still seeing low boost Checked a few things out, tightened a few pipes that seemed a bit loose but still no joy!
Current thinking from my trusted mechanic is that it's not an underlying mechanical issue but rather something electronic or a boost leak somewhere. Suggested next steps are that we try and change the DV as that could be bleeding boost or that it could be the MAF sensor. I've ordered both off ebay (DV second hand and MAF new) so I'll try those and we'll see what happens.
On the plus side after 3 months of not driving it I reconnected the battery, gave it a dash of coolant, a smidge of air in the tires and it fired up and drove like I'd never been away. I know it's not "right" but it still felt like a rocketship after 3 months of just my 1.2 Clio!
Finally got round to having the MAP sensor changed on Saturday and shock of the day I'm still seeing low boost
Checked a few things out, tightened a few pipes that seemed a bit loose but still no joy!Current thinking from my trusted mechanic is that it's not an underlying mechanical issue but rather something electronic or a boost leak somewhere. Suggested next steps are that we try and change the DV as that could be bleeding boost or that it could be the MAF sensor. I've ordered both off ebay (DV second hand and MAF new) so I'll try those and we'll see what happens.
On the plus side after 3 months of not driving it I reconnected the battery, gave it a dash of coolant, a smidge of air in the tires and it fired up and drove like I'd never been away. I know it's not "right" but it still felt like a rocketship after 3 months of just my 1.2 Clio!
Hol said:
I bought a cheap 40 boot leak tester off eBay. You stick on the turbo inlet and pressurise the system with an airline.
It was amazing the amount of leaks I found on an EVO engined car.
Intercooler clamps, throttle body seals, gaskets and injector seals. It's now sealed up and holds 2.0bar.
There are some garages that have kit to do this while they inject smoke into the system, so you can see the leaks easier.
Hmm... might be worth investigating.It was amazing the amount of leaks I found on an EVO engined car.
Intercooler clamps, throttle body seals, gaskets and injector seals. It's now sealed up and holds 2.0bar.
There are some garages that have kit to do this while they inject smoke into the system, so you can see the leaks easier.
Still planning on testing out the notion of swapping the MAF and/or DV as well (if the DV ever turns up...grr!). Took the car out last Thursday and other than the noticeable drop off in power at higher revs it still felt fun to drive which put we in a good mood, coming to it on Saturday to find it had drained the battery didn't though
king progress 
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