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-   -   Very scary compression numbers on my turbo car (https://www.miataturbo.net/general-miata-chat-9/very-scary-compression-numbers-my-turbo-car-60801/)

hustler 10-02-2011 12:19 AM

Very scary compression numbers on my turbo car
 
1-4:
60, 60, 120, 120

I'm guessing the compression gauge is not sealing properly (rubber hose) becuase the car drives the same way it did when it was new. There is no smoke, no blow-by, and it sounds fine. It idles fine, cold starts and warms up fine, and drives fine. Should I be worried? I'm getting a different compression tester tomorrow and getting a working leak-down gauge tomorrow, but I can't sleep with this kind of drama no matter how much I drink.

Savington 10-02-2011 12:27 AM

Do you need me to rock you to sleep? I told you on the phone today that your compression tester was shit. Cars with 60-60-120-120 compression don't roll tire in 3rd gear on 80*F days.

hustler 10-02-2011 12:30 AM

Quote:

Originally Posted by Savington (Post 778542)
Do you need me to rock you to sleep? I told you on the phone today that your compression tester was shit. Cars with 60-60-120-120 compression don't roll tire in 3rd gear on 80*F days.

on concrete.

18psi 10-02-2011 12:36 AM

go to sleep hoe.
just rub one out and get a new tester tomorrow.
sav is right: with 60 in 2 cylinders your car would run like a tractor

flounder 10-02-2011 11:06 AM

If you've got a regulated air compressor you can use your comp tester as a leak down.

hustler 10-02-2011 12:18 PM

So would you guys pull the head off and have a look or just leave it?

Math~ 10-02-2011 12:38 PM

leave it and wait for your new compression tester =)

Savington 10-02-2011 12:39 PM

Quote:

Originally Posted by hustler (Post 778660)
So would you guys pull the head off and have a look or just leave it?

Next time we meet, remind me to kick you in the nuts as punishment for this thread.

hustler 10-02-2011 12:45 PM

Quote:

Originally Posted by Math~ (Post 778662)
leave it and wait for your new compression tester =)

Why would it be consistently wrong? I'm thinking 1/8 turn int he tester fitting either way would make some variation in compression.

Also, do you guys think 243whp at 11psi on 8.6:1 compression is low? I sure do. I'm guessing this motor was blown up a long time ago. I'm really worried about getting in there and seeing a ton of detonation and a dead motor. I guess I'm going to plan on not running TT next year, time to buy a kart.

Edit:
The plugs all look exactly the same too.

MartinezA92 10-02-2011 01:43 PM

Borrow a friends compression tester and see if theres a change. If its really bothering you do a leakdown test. If you really had 60 psi compression I think you would have noticed.

hustler 10-02-2011 01:49 PM

I'm guessing the head gasket is leaking between cylinders. Basically both of my cars are broken now and I'm fucked.

spoolin2bars 10-02-2011 02:32 PM

i wanna falcon punch you right about now! your cars are broken but they run great. you make alot of sense. I'm this - close to unfriending you for sounding like a clueless chick. you know your in the lead of unlimited class right?

btw - my car made 230whp at 11psi so no, that doesn't sound low

MD323 10-02-2011 03:01 PM

I had a BP that gave me low compression numbers but ran great (85,80,120,80) and by great I mean drove 1200 miles with 3 people and a motor in the hatch. turns out after tearing down the motor the head was cracked in 2 places.

BP's are built like tanks for the most part, they dont die till you ventilate the block.

hustler 10-02-2011 03:15 PM

Fuck it, I'm drinking today and I'll worry about this after TXMC. Time to smoke heroin.

spoolin2bars 10-02-2011 03:39 PM

Quote:

Originally Posted by MD323 (Post 778700)
I had a BP that gave me low compression numbers but ran great (85,80,120,80) and by great I mean drove 1200 miles with 3 people and a motor in the hatch. turns out after tearing down the motor the head was cracked in 2 places.

BP's are built like tanks for the most part, they dont die till you ventilate the block.

i guess anythings possible, but it's hard for me to believe that he could have a head that's cracked to pieces, but still runs enough boost (not 11psi, has to be more like 15psi) to roast 3rd gear, and there is no trace evidence on the plugs or even in the way the car idles, or revs. and drives smooth as always. no discernible difference from fresh build? that would be pretty amazing.

spoolin2bars 10-02-2011 03:42 PM

Quote:

Originally Posted by hustler (Post 778706)
Fuck it, I'm drinking today and I'll worry about this after TXMC. Time to smoke heroin.

YES! heron.... your not darth vader, don't let the fear consume you.... lol

hustler 10-02-2011 07:53 PM

Ok, so got a new gauge from HF and new leak tester and things are not good
Compression
60, 90, 120, 120

Leak
60, 60, 40, 10
I can hear air through the exhaust on every one. I've never really over-revved the car so I'm guessing some exhaust valves are burnt. However what really gets me is that the car drives totally fine, and still goes fast as shit. I guess I'm going to run TXMC then take the head off and have a look. If the valves are burnt we're switching to Inco exhaust valves with Berrylium seats. This is weird. Just to be sure I was at TDC I rotated the engine from -5* to +5* to make sure the exhaust valves were closed and never saw a real change in the leak gauge. I'm guessing it's not the tester hose since I always heard air through the exhaust.

flounder 10-02-2011 08:21 PM

Are you doing the test correctly on a fully charged battery? Five to six cranks wot on each cylinder should do it.

With the leakdown, make sure all valves are closed and only run like 30-40 psi at first.

With those numbers, the engine would barely stay running, you should be up in the 180's at least.

hustler 10-02-2011 08:33 PM

Quote:

Originally Posted by flounder (Post 778792)
Are you doing the test correctly on a fully charged battery? Five to six cranks wot on each cylinder should do it.

With the leakdown, make sure all valves are closed and only run like 30-40 psi at first.

With those numbers, the engine would barely stay running, you should be up in the 180's at least.

Many cranks, strong battery.

Savington to reminded me of valve lash. I had to adjust it a few years ago, maybe I went a tick too far.

miata2fast 10-02-2011 09:02 PM

If you had your valves that tight for that long, chances are you have erosion on the tight valves. If you are sure you did the test right, I would strongly consider pulling the head. The longer you wait, the more damage that will be done.


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