Low compression on cylinder 3 65,000 miles

Mazda speed3 low compression on cylinder 3.
Here for some insight.

So, last summer, my k04 shit the bed at 60,000 miles. After a couple seasons of tuning & a summer of meth injection.

After the K04 let go, I knew I had an issue and parked the car for the year, now a year afterwards. The car is back in action with a v3 XS power exhaust manifold, BNR S5, 44mm Tial, 3 bar map & all associated bolt ons. ( Catless turbo back, 4” intake, etc. ) the only part I’m missing is the intake manifold. Still running stock with a VTCS delete.

I’ve been going through the tuning process with the wizard himself at PD Tuning. And have put approximately 600-1000 miles on the car since it’s been thrown together and running. I’ve noticed lately, that the car was still smoking a little blue smoke after WOT pulls, and occasional downshifting or spirited driving. So I decided to take the intake manifold off, change PCV valve, clean intake manifold, throttle body, and FMIC intercooler pipes, as well as ensuring OCC hoses had no kinks, and that the OCC was working properly.

At the end of this process, I decided to do a DRY compression test to ensure cylinder pressure was good & my results were 180-180-145-180… infamous cylinder 3 being a little low, I shoved the Borescope down there and everything looks fine, valves, cylinder walls etc. but I did have some oil in cylinder 3, as well as cylinder 2. Wet test the next day came back 185-185-150-185. I am here to gain some insight on potential issues or things that could be occurring to cause this. Aside from common issues in this scenario. I understand that a leak down test will give me more of an understanding of where any leakage may be appearing. Just wanted to share & get some opinions. No misfiring, or stuttering or irregular issues.

I am the original owner of the car, with currently 65, 000 original miles. I have never had any engine issues before. And am only currently tuning on 91 octane as that is the best I have for pump fuel in Atlantic Canada.

i only drive the car during the spring, summer & fall months. And was hoping to get the full summer out of it at least, I understand pushing the limits with a larger turbo will tire out a stock engine. The car is more of a weekend warrior, I would like to have some sense of security, that if I am normally cruising in the car on weekends and respect it, as well as not perform any harsh driving or stress the motor more, that I’ll be okay and won’t destroy anything. Before storing the car, and doing a short block build during the off season.

any more information needed, can be provided as well as any logs.

Thanks in advance.

 

I'd probably just pick up a used engine at this point and throw that in there then rebuild the one you have now.

40 psi difference in compression is a big number. Sure you can do a leak down test and that will tell you where you're losing it at, but if you want to keep it on the road sooner rather than later a used motor is your best bet.

 

Understood sir. Unfortunately, I live in Newfoundland, Canada & here mazdaspeed’s are hard enough to come by as is. Finding a motor that’s solid locally is essentially like coming across a needle in a haystack.

I have no issues building the block once I store the car, just out looking for opinions, culprits & thoughts on my scenario. I do appreciate the advice though sir!

I will be performing the leak down test within the next couple weeks, as well as just cruising around in the car, to monitor any more compression loss, oil consumption, as well as exhaust smoke. Anytime I decide to take it out as it isn’t my main daily driver, it will be well respected & there won’t be a consumptive amount of WOT pulls, or harsh driving.

 

If you've lost that much compression it isn't going to get any better and the risk of damaging the block beyond repair increases.

Why not import a 2.5 block and build that? You can swap your head onto that and they can be bought here in the US for cheap.

https://www.ebay.com/itm/234500651946?hash=item369953fbaa:g:2LkAAOSwd2liUIrS

 

It’s a thought, but really all I mean by continue to drive it is literally probably 500 more miles, max. I understand that I could end up looking foolish with a damaged engine down the road as well, but I will be inspecting the motor, with a borescope & compression test each drive.

I love the car, and have very limited months to drive it reasonably where I live, I’ve heard the pros & cons of the 2.5 engines, and they are more common here I will admit, but I want to entirely build this block once fall hits. Money thoughts entice me to do the same thing.

Shipping absolutely anything from the United States to Newfoundland, is a hell of a time though brother, between your dollar rate compared to ours, Canadian, and American taxes; plus shipping & duty fees. It would blow your mind how much I will end up paying for even these examples you’ve linked.

 

I hear you on the importing issues. I'm trying to purchase carpet for my Miata but it's RHD so I have to get it from England. Converting from GBP to USD and shipping is crazy. I'll be paying almost the cost of the carpet kit with shipping and duty fees.

 

So I’m curious what kind of damage could occur from driving the car (hard?) with one cylinder at 145?

 

If the fuel being sprayed into that cylinder isn't atomizing enough due to low compression then the cylinder will get washed down further. The fuel gets into the crankcase and dilutes the oil leading to increased wear on the other cylinders, catalytic converter damage (if equipped) as well as damaged spark plugs.

There are also other concerns such as a cracked piston or ring land that can break causing damage to the block.

 

Knock will likely happen. KR may be so bad it will pull timing advance. Your tune may have masked KR. I had same one hole blowby of 20% with a S3 and KR was 5-8 causing timing to go crazy. Tried 33% methanol because no other fuel choices, I pulled (reduced) advance 12 degrees and still KR. Thats when I did complete rebuild.

 

Interesting!

Before I rebuilt the engine in mine the highest was maybe 155, with others 140 or lower and cylinder #4 was 0. It actually didn’t run that terribly. Though cylinder #1 did break a rod and vented the block, so…

 

I’m glad you guys chimed in. I appreciate the insight, and Jsilva, you poor bastard, hahaha.
I haven’t been driving it since I posted this thread because it isn’t my daily, but I’m still 180-180-145-180 & will be monitoring any change every drive, usually on the weekends. No misfiring has occurred before.

I do have ghost knock, for a fact during normal driving conditions, waiting on a new knock sensor, but my WOT logs have all been pretty good, a couple had minor KR around 5000rpms from .50-1.5, but I believe that it was just heat soaked. I haven't had it during better chosen WOT runs that have been overly consistent with KR. I’m also going to keep track of this, although I don’t see myself driving the car hard anymore the summer. Rarely if so. I am on my fourth pump gas revision with PD.

Cfoldone, what exactly do you mean by 33% methanol, pulled advance 12°? Timing advance? I’m not crazy familiar & am curious.

essentially I’m curious how you eliminate KR by advancing timing, i think.

 

Pulled timing from advance tables on my VersaTune map. So would subtract whatever value was set for that cell. Washington State only has 92 and to double check KR added 100% methanol from fuels vendor to get 33% in addition to timing.