Jump to content
SAU Community

Recommended Posts

So i brought this car a year ago with 250k on it with a blown ECU and a tight cam belt, Fixed that and is was a new car again. The problem has been that the compression cold is 140psi throughout the 6 and once hot they all drop evenly 20psi down to 120psi throughout the 6. its been like that for a year now and hasn't changed. it doesn't use oil really and doesn't fill up the catch can. the k&n filter on the catch can looks abit oily however. There's no noticeable blow by just a puff of white smoke out the catch can when you give it a hard rev.

I haven't done a leakdown test yet I've been putting it off. my question is what causes compression to drop like that? i have no information on the history besides it was owned my crackheads and it sat dormant for possibly more then 5 years. the motor looks super clean for how many km's it has and how trashed the suspension is. the car runs perfect but i can feel the 20psi loss as the car warms up.
i was thinking someone put a thicker head gasket on to drop the cr but that still doesn't answer the compression drop. its suppose to rise isn't it lol.
I've asked many mechanics and they cant explain it.
Hope someone can help!
Thanks.

Link to comment
https://www.sau.com.au/forums/topic/482142-r33-gts25t-compression-issue/
Share on other sites

3 hours ago, blind_elk said:

Have you done a wet compression test?

Its a good idea, but it will confirm worn rings. The suspension didn't get rooted because the crackies drove it to church on Sundays. Or down to Supercheap for new filters, before the car wash.

Edited by Rusty Nuts
additional information
  • Like 1

hmm, its running 10psi atm, iv blown 2 turbos so far going any higher on the stock ones. Im still confused why the compression dropped 20psi just from warming up, and even more so why its 120psi hot and cold a year later. wouldnt it drop down to say 100psi once warmed up if its worn that much in the time iv owned it. if compression should be around 160-170+ and i have 120, shouldnt there be quite abit of blowby?
I forgot to take the crank case vent valve out of the manifold to get a true reading of how much blowby there is, i dc that. i took the catch can hose out and you can bearly notice air coming out, you have to squeeze the hose end and then its enough to feel like a gentle flow of air. 0 smoke. same if you give it a rev.
iv used the same comp tester for years to eliminate getting different readings.

Edited by JasonMate

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • That's not a transistor --- it's marked ZD1 which makes it a zener diode. As to what the breakdown voltage is, not enough there to divine.
    • Hi all, Long time since I've posted here. Looking for some advice on what I can remove to further identify the cause of my issues.  I can move the passenger seat forward and back but the knob used to adjust the seat angle is pretty much free spinning, there's very little resistance.  Removing the side cover I can see that the chain is intact but the shaft for the adjustment spins without the gear attached to it moving.  What's my next step for disassembly here? Is this a common fault? Just being a little cautious as I didn't want to start removing bolts for a spring to fly out or something equally as stupid.  Cheers
    • The incentives are mostly the same, yes. Ethanol is cheap compared to the cost of doing 98-100 RON with crude oil alone. 87 to 93-94 AKI all with E10. In 2020 Canada mandated E10 as a part of their "renewable fuel standard" and is supposedly going to go to E15 in 2030. In California where there are only 8 refineries with two threatening to shut down next year it's been over 20 years now of E10 and 91 AKI maximum because there's just not enough refinery capacity or crude oil supply relative to the demand for premium unleaded fuel. And CARB's low carbon fuel standard means functionally none of the diesel available at the pump is made from crude oil anymore. It's almost all entirely 20% biodiesel blended with 80% renewable diesel (hydrotreated vegetable oil) now. The number of gasoline vehicles that support E15 or higher ethanol concentrations is surprisingly low, I can't imagine it being wise to play tricks like this without flex fuel sensors in most of the fleet.
    • It's almost certainly the same as the one next to it. Have a fish around amongst these hits https://www.google.com/search?q=surface+mount+transistor+m33&sca_esv=9cb49794e0b2005d&source=hp&ei=2vJ5aNjTB7Kw0PEPldnS8QM&iflsig=AOw8s4IAAAAAaHoA6qkfmF6XcygtrZ4Vu9f92NXF_RFd&ved=0ahUKEwjYqIPP7MWOAxUyGDQIHZWsND4Q4dUDCA8&uact=5&oq=surface+mount+transistor+m33&gs_lp=Egdnd3Mtd2l6IhxzdXJmYWNlIG1vdW50IHRyYW5zaXN0b3IgbTMzMgUQIRigATIFECEYoAEyBRAhGKABMgUQIRigAUjKCFAAWABwAHgAkAEAmAHfAaAB3wGqAQMyLTG4AQPIAQD4AQL4AQGYAgGgAuYBmAMAkgcDMi0xoAfMBLIHAzItMbgH5gHCBwMyLTHIBwU&sclient=gws-wiz
    • South Australia, which is hardly as far behind as the rest pf Oz makes out, and who is also not a paragon of progressiveness (read that as over-legislation) in the area of vehicle standards, has this to say on the subject: Adjustable coil-over suspension Aftermarket adjustable coil-over suspension components are suspension units that incorporate an external thread on the main body and corresponding threaded spring saddle that allows the vehicle's suspension height to be varied. If fitting aftermarket or coil-over suspension components you must submit an Application to modify a light motor vehicle form and a report from a light vehicle engineering signatory (LVES).
×
×
  • Create New...