hi guys noticed over the last couple of days that the scoobs been hesitating when i plant the throttle but then after a second or 2 it accelerates.

last night i had it on tickover, cold and opened the oil filler cap but didnt see any smoke coming out. but tonight hesitation seems pritty bad about a second or 2 but then powers comes in ok.

when i got home it was up to temp and i took the oil filler cap off and there was no smoke but quite a lot of pressure coming out, asin the lid would blow off if i rested it on there.

its an 07 2.5 sti hawkeye with a remap, full decat and panel filter and dumpvalve.

do these symptoms suggest anything to any one? the engine management light is off so not telling me theres a problem but doesnt feel right.

any help would be great been reading alot about rings failing on the 2.5 so a bit worried

thanks morgan

 

Have you recently filled up with fuel? Could be a bad batch. It's also worth cleaning the MAF as this can foul up a bit and can cause some stuttering.

What's your oil consumption like. If you have a cracked ringland, it'll be getting through the stuff at a rate of knots.

Also, if your DV is the vent to atmosphere typre, I'd think about replacing that if I were you - only thing it'll achieve (assume you still have a MAF) is noise (each to their own on that front), turbo lag and worse fuel economy.

 

i wish it was that, i was 3/4 of the way thru a tank but has been doin it a while. just done a compression test on it...
front left- 120
back left- 120
front right- 80
back right- 120

put some oil down the bore and it went up to 90 in front right

did a cylinder compression test and air was coming out of the oil refil

 

Gutted, sorry to hear that - I had a Forester XT previously that suffered the same fate as your STi... wasn't so bad for me as it wasn't worth a lot and was a good excuse to get back into an Impreza.

Hope you manage to get it sorted as cost effectively as possible.... though while it's apart it's a good time to do some upgrades (budget permitting of course)

 

Same thing happened to me.
Try David at API.
That's what I did.

 

Usual case cylinder number 2 to blow a ringland, Terminal illness on that motor, Nothing an overhaul couldn't sort depending on budget, it will need a re-bore and oversize pistons fitted

 

what pistons and rods do you all recommend? any makes to avoid?
thinking about forging her making sure it doesnt happen again and so i can get a bit more power out.

ive been told that the standard block will take about 450 without being pinned so not sure whether to pin it or not.

 

I think the Mahle pistons are quieter when cold than most. Ive heard Cosworth are noisy. If you go 450 you would be advised to get steel rods too. I would also get 11mm head studs on the list.

 

what rods do you recommend? ive been looking at the studs also.
what head gaskets are recommended? ive read quite a few threads on aftermarket ones failing lately so not sure what to go for

 

I think the rods will depend on whether your going to chase even more power at a later date. I would talk to Paul Finch API or Enginetuner for advice on that. I believe Subaru or cosworth head gaskets are the best. Im no expert just repeating what ive read mate.

 

no thats great thanks just trying to get an idea of what to look for and what people like/ recommend before i ring around next week

 

CP pistons sized correctly to your application are pretty much quiet. Note CPs are not offset.

I have them in my build and it is very quiet compared to Wiseco, JE.

Also they have a huge list of options off the shelf. Get a set of uprated piston rings if you plan on further mods.

Stock STi rods seem to be good. The OEM fasteners seem to be the issue.But a set of Eagle rods with ARP fastners are not much more dosh.

Also ARP head studs take care of the OEM issues.

Tuning build

Decide what path you want now. It is easier to put most of the parts in during the rebuild, than later.

 

sorry guys im still learning but what do you mean they are not offset?
and what do you mean by piston noise?

thanks

 

The best advice anyone could give you is to contact Paul Finch, & stay away from Cometic Gaskets.

 

Hey no worries, we all were taught at some time

OEM pistons have offset wrist pin. = less piston slap

Forged pistons generally have more PWC than OEM piston. This is because a forged piston expands more, PWC= piston to cylinder wall clearance.

Piston slap is the noise forged pistons make when cold until they expand to proper fit. I.e the PWC gets smaller when hot.

CP = great , others more noisy but cheaper.

Best to find a great engine builder. I recommend David at API aswell. Awesome service and very good info. It is provided in plain english. Some off us are a little down on our engineer speak

And he will talk to you long after you paid your money.

 

cheers for that, im trying to learn as much as i can slowly :P will give him a ring next week to chat through my options.

thanks guys

 

Just give me a ring when you're ready and l'll sort you out.

David APi

01926 614333