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2007 Hawk STi forged / mapped to 342bhp
Just need some ideas really. Recently I've been noticing I'm filling up more often. I filled up just now, a proper fill up - past the click stop. VPower.
I reset my trip meter, and 20 miles later I've used 1/4 of a tank. It was a mixed, town / motorway drive, but it's using more fuel than I've ever known.
I did have a little while ago a CEL which turned out to the the passenger side single AVCS solenoid being stuck open. Idled terrible.
Cleaned it out, cleared the CEL with my PSI3 data monitor. ECU reset etc. No returning CEL. Idle normal etc.....but....
I still on a hot start, the car seems to start fine, then almost straight away the rpm drops to perhaps 250-300 rpm (according to the rev counter for a few seconds) then back up to approx 800 - 850 rpm.
The MAF was replaced last year, spark plugs too.
I don't have a CEL to help point me in any direction.
Could it be I would be better trying a new AVCS solenoid? But as said, no CEL.
Coolant temp sensor? But the PSI3 readings and coolant gauge seem fine / how they have always been.
Strong boost comes in a bit late....approx 3.5k rpm or 4k rpm, car doesn't have the bottom end grunt that it used to.
Boost system checked with pressure / smoke....no leaks.
Emissions are bad, and would fail an MOT, they said it was showing signs of unburnt fuel.
Whilst the car runs "Well" I could possibly be missing out on performance, and it really is drinking way too much fuel.
The guy I usually use also tried a new front 02 sensor, but apparently made no difference, so he put my old one back in.
CTS has three pins on the newage. One pin for the gauge and another for the ECU. Don't know where the PSI3 takes its readings from but don't discount the CTS sensor.
CTS has three pins on the newage. One pin for the gauge and another for the ECU. Don't know where the PSI3 takes its readings from but don't discount the CTS sensor.
Thanks Joe. The PSI3 probably takes it's readings from the ECU as it plugs into the OBD 2 port under the steering column....
Would I lose much coolant replacing it?
Intercooler off to get to it on the crossover pipe? Or inlet manifold off....hope not!
Wouldn't a faulty CTS give me crazy unrealistic readings on my gauge or PSI3? I guess there's no CEL for a faulty CTS...
It could possibly explain why a cold start is fine...starts up straight away and idles at about 1250 rpm, then slowly comes down.
Hot start, sudden drop in rpm then back up to normal after a few seconds.....
Last edited by Hawkeye D; 08 May 2023 at 12:52 PM.
Do it when stone cold in the morning. Alternator off don't take coolant cap off unplug, undo, replace, I'll be very surprised if you lose and egg cup full
It wasn't about the DTC's it was about the fuel cap.......(it's fitted with a vacuum release valve)
My vacuum release valve wasn't seized, it moved freely when I gently pushed on it a few times.
Just went out, did a hot start, the rpms dropped to about 150rpm or thereabouts then back up to normal.
When I cleaned out the AVCS solenoid a few months back, it did seem to hot start better for a bit...perhaps my inlet camshaft phaser sprocket on the passenger side is dicking around, but then I'd get a CEL surely?
Hot start, after car is sitting for a good few mins, you'll get a heat soak moment where car gets a gulp of very warm air which is why it near stalls then picks up again.
If you do a hot start then when it idles normally immediately turn it off and then start it again does it start and idle as normal? I'd say it will
Just read it, but I'm not getting any P codes...
My PSI3 tells me current and historic codes until cleared, it's empty of P codes...
Whats it saying the CT temp is on the PSI3?
What grams is the Maf showing with engine on but not started?
If you had a laptop and was using Romraider gauges id ask for the Maf voltage.
Hot start, after car is sitting for a good few mins, you'll get a heat soak moment where car gets a gulp of very warm air which is why it near stalls then picks up again.
If you do a hot start then when it idles normally immediately turn it off and then start it again does it start and idle as normal? I'd say it will
Well Gambit, massive thanks for this. Your comment made complete sense, TMIC heat soak. It's something I've read about often, but didn't realise I was "suffering" from.
Test :
Drove about 15 miles mixed driving, engine at about 87 degrees, pull into a car park, switched off.
Re-start a few seconds later, straight to normal rpm, no bogging down. Switched off.
Waited about 5-6 minutes, restarted, bogged down, rpm back up to about 850 rpm, switch off.
Restart straight away, no bogging down. - Exactly what you said would happen.
For over a year I've been wondering / waiting for a CEL that was never going to come. Classic textbook case of heat soak.....100%
I didn't even think of this for one minute sadly!
It seems even if I drive really carefully, or more beans, when I switch off, the turbo, exhaust / heat shields tick like mad...a fast ticking like crackling sound almost.
All this hot air is piling out the bonnet scoop...making my TMIC rather toasty - and fully explains the bogging down.
I sometimes even hear the PPP rear box ticking....proper hot, so hope I'm not running lean (no lean codes etc)
I always switch on the A/C in traffic to keep air moving under the bonnet...regardless of weather, but of course, this has no relevance for a hot start after sitting whilst getting fuel or nipping into Tesco etc.
Thanks again, something so simple, and zero cost, just how it is.
Last edited by Hawkeye D; 10 May 2023 at 05:49 PM.
Whats it saying the CT temp is on the PSI3?
What grams is the Maf showing with engine on but not started?
If you had a laptop and was using Romraider gauges id ask for the Maf voltage.
CT on PSI3 behaves normally, warms up to about 85 - 87 degrees, in traffic goes to 97 gradually, and the fans kick in, back down to about 82 - 85 degrees.
Engine off (hot), ignition on :
AF 2.2 g/s
LA 1.00 Afr
Last edited by Hawkeye D; 10 May 2023 at 05:47 PM.
Yes, PPP sports cat I think it is.
It's whatever cat they use for PPP on a Hawk STi....I think it's just slightly smaller than what it left the factory with...
It is also on standard up and down pipes.
Last edited by Hawkeye D; 11 May 2023 at 05:39 AM.
Yes, PPP sports cat I think it is.
It's whatever cat they use for PPP on a Hawk STi....I think it's just slightly smaller than what it left the factory with...
It is also on standard up and down pipes.
PPP on hawk STI 2.5 uses standard downpipe & cats - it didnt get the sport cat like previous 2.0 STI got.
Yes, PPP sports cat I think it is.
It's whatever cat they use for PPP on a Hawk STi....I think it's just slightly smaller than what it left the factory with...
It is also on standard up and down pipes.
Your cat could be on its way out and that would definitely increase your fuel consumption that would explain the extra heat from the exhaust also.
No easy way to tell? How would it create extra heat?
Would I not get a CEL from the after cats sensor with the yellow wire?
Does my standard factory up pipe have a cat? 2.5 UK Hawk STi.
As an example, I'm sure this is my standard turbo back set up, looks like 2 cats here,1 on down pipe and 1 on mid pipe :
I could get some second hand sections, but then I never know what I'm getting condition wise.
I wouldn't want to go too loud, but could do with more burble though, but then don't want to have to change sections for MOT's etc....
Last edited by Hawkeye D; 12 May 2023 at 05:50 AM.
Thats oem subaru cat, if its prodrive one should come with 100 cell sportscat but its a hawk and maybe something changed. Sti has no cat in uppipe.
You can sell old subaru cat and buy new sportscat, it should cost You nothing that way.
Last edited by JdmSti2006; 12 May 2023 at 06:24 AM.
No easy way to tell? How would it create extra heat?
Would I not get a CEL from the after cats sensor with the yellow wire?
Does my standard factory up pipe have a cat? 2.5 UK Hawk STi.
As an example, I'm sure this is my standard turbo back set up, looks like 2 cats here,1 on down pipe and 1 on mid pipe :
I could get some second hand sections, but then I never know what I'm getting condition wise.
I wouldn't want to go too loud, but could do with more burble though, but then don't want to have to change sections for MOT's etc....
Usually they wear and end up either falling apart completely and ratting around or they partially start to block the exhaust slowing the gases coming out so it creates the extra heat as the gas can’t escape quick enough, do you have a way of seeing your exhaust temps on a obd reader or aftermarket gauges?, if not try shaking your exhaust to see if you can hear anything rattling around, as said above if it is that a good sport cat would be the best way to go if you don’t want mot issues or the car too loud.
No easy way to tell? How would it create extra heat?
Would I not get a CEL from the after cats sensor with the yellow wire?
Does my standard factory up pipe have a cat? 2.5 UK Hawk STi.
As an example, I'm sure this is my standard turbo back set up, looks like 2 cats here,1 on down pipe and 1 on mid pipe :
I could get some second hand sections, but then I never know what I'm getting condition wise.
I wouldn't want to go too loud, but could do with more burble though, but then don't want to have to change sections for MOT's etc....
No up pipe cat
quoted link above is the downpipe setup on Newage bugeye and blob models NOT Hawkeye
Usually they wear and end up either falling apart completely and ratting around or they partially start to block the exhaust slowing the gases coming out so it creates the extra heat as the gas can’t escape quick enough, do you have a way of seeing your exhaust temps on a obd reader or aftermarket gauges?, if not try shaking your exhaust to see if you can hear anything rattling around, as said above if it is that a good sport cat would be the best way to go if you don’t want mot issues or the car too loud.
Ok, that explains the extra heat, I know exhausts tick when cooling down, but mine is a bit extreme in my opinion and leads to the heat soak mentioned above. This could also explain why after I clean the inside of the PPP tailpipe, it's weeks before there's even a film of very very light soot build up in the tip.
Sadly can't get EGT on my PSI3.
Thanks Don.
So the Hawkeye pic, what's at the bottom of the downpipe above the join, is that also a cat, or just a silencer?
Have replaced some missing images in that linked thread.
The "down pipe" is usually considered to be the section of exhaust from the Turbo outlet to the donut flexi joint. (Subaru have other ideas about that, but thats a whole different story)
As with the earlier versions there are two cats in the complete "down pipe" section. With the PPP the second cat is "usually" replaced with a straight through pipe section but can have the heat shields refitted.
I say usually as my MY11 WRXSTI has the then "Subaru PP" map with both OEM cats still in place and good for 340hp/360lbsft. It does have an H&S cat back exhaust.
Last edited by Don Clark; 13 May 2023 at 08:01 AM.
You welcome regarding uppipe 3 gallons per 20 miles, all burned below 6k rev band impressed with 2.5l ,less power than diesels with same rev band with 3x fuel consumption,bargain
08 May 2023, 08:35 AM
Using too much fuel...
