Mod Options? Low-ish Compression

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Imbenman

Greenie N00B Member
Hey so I've creeped around this forum since I bought my 07 Speed3 around 2 years ago, but finally decided to make an account and post for myself. I've kept the car stock since I've had it, spare an OEM replacement Stigan turbo (oem was dumping oil when it idled for more than a minute or two) and a TurboXS blowoff valve for giggle effect and have loved driving this car. But, now I'm wanting some more power but am not too sure how to go about it.
My main issue is that its stock motor and trans around 155k miles, and upon doing a compression test I noticed that cylinder 3 is at 105, acceptable but not by much while the rest were >115. I was thinking about getting Versa Tuner and a hpfp then just running an otf tune like that but idk.
So the main question is, how should I go about this? This is my only car and I'd really like to not blow a ring but I want a little more oomph than stock. What mods should I look to and avoid so I don't have to sacrifice reliability but still be able to get what I'm looking for?
Thank you all in advance for your tips and inquiries.
 
Umm 105psi is not acceptable at all 130psi is Min spec. I would not mod that car at all and would seriously be looking at another engine to put in that car if it's your only vehicle. Used engines can be had and put in. Saying other cylinders are >115 tells me atleast one other cylinder is <130 what are your compression test results per cylinder, did you do wet/dry test any leakdown test?

as per the shop manual; Compression
Standard: 1,280 kPa {13.05 kgf/cm2, 185.6
psi} [250 rpm]
Minimum: 896 kPa {9.14 kgf/cm2, 130 psi}
[250 rpm]
Maximum difference between cylinders:
196.1 kPa {2.000 kgf/cm2, 28.44 psi}
 
Depending on the tester he has it might not be able to read over 100. Had that issue with a HF one I think that wouldn't go over 120 or something.
 
Awafrican said:
Umm 105psi is not acceptable at all 130psi is Min spec. I would not mod that car at all and would seriously be looking at another engine to put in that car if it's your only vehicle. Used engines can be had and put in. Saying other cylinders are >115 tells me atleast one other cylinder is <130 what are your compression test results per cylinder, did you do wet/dry test any leakdown test?

as per the shop manual; Compression
Standard: 1,280 kPa {13.05 kgf/cm2, 185.6
psi} [250 rpm]
Minimum: 896 kPa {9.14 kgf/cm2, 130 psi}
[250 rpm]
Maximum difference between cylinders:
196.1 kPa {2.000 kgf/cm2, 28.44 psi}
Click to expand...

Oh.. well shit. I didn't know it was minimum 130 by spec, but tbh I didn't know the vehicle specific spec, I was simply taught if it hits 100 or under you have a problem. It's been a little while since I did the compression test, but if I remember correctly it read at: cyl 1 @120 cyl 2 @115 cyl 3 @105 cyl 4 @140.
I didn't realize how low my compression really was but she's run without much of an issue since the turbo swap about 6 months into my owning of the car (and I don't baby the thing), I think past that and the plugs/coils I put in with the turbo the only mechanical thing spare regular matinence I've done since is replacing the throttle body, but like a few others on this forum I've been chasing a random/multiple misfire only on cold start from day 1 but now I don't know if its even worth the time or parts to chase it any more, if the motor is gonna go soonish. I didn't do a leakdown test though I should've now I look back on it.
Now the real big question is: what should I do?? I don't want to get rid of the car because I learned stick on it and absolutely love driving it, but if the motor and/or trans goes on me anytime soon I can't afford to swap it. Is there anything I can do to extend the life of the already tired powertrain (again I knew it was tired but I didnt know it was THAT tired) or am I just boned and should drive it like I have until it goes on me??
Any sorta advice would be greatly appreciated, after this I'm not sure what to do for my poor Speed3.
 
Although it is inevitable that you have a engine with unknown date of expiry. Best would be to treat it with kid gloves from now on. If you were to dig deeper into what might be the reason for the low compression (aka a leakdown) you might be able to distinguish what the most prevalent problem is. These cars tho most commonly suffer low compression via the rings. All this while saving your quid for a replacement engine if required. Continuing to drive it like you "don't baby the thing" will most certainly have you walking the rest of the way without warning. Good luck.
 
Easter Bunny said:
Since you ha e no other issues with the way the car is running I would start with retesting the compression.

Have you ever cleaned the intake valves?
Click to expand...

I haven't cleaned the intake valves, and I'm now planning on doing both a compression and a leakdown test to see what's up. I'll figure out how to clean the valves. Is there anything else that can be done as "preventative matinence"?
 
Preventative maintenance is what you do over the entire life of the car to reduce the chances of failure, lol. A leakdown test can help you distinguish if you have a ring seal problem or a valve sealing problem. If you are having a ring seal problem it pretty much means a rebuild, especially if you wish to continue driving the car as it was designed. Hail Marys wont stop the inevitable decline of performance.
As for the latter, if you have a valve sealing problem, the first thing I would look into is valve cleaning. The build up of carbon on the valves can inhibit proper closing of the valves. It is conceivable your generally low compression across all cylinders is affected by this, and is worth verifying. If that dosent help, you could consider a re & re with a rebuild head. still not cheap, but at this point cheap wont fix any of your problem.
 
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