Compression test results - Advice?

[mrzwei]

Ummm, I see a lot of new posts whilst I was typing to mrzwi

  s:lol: :lol: s:lol:   Trust the old git, don't worry unless you are losing fluids (the car that is) or losing power or getting a misfire.
Plus or minus 15psi from the norm of 184 would be 199 / 169.
Other factors = hot engine / cold engine, ambient temperature, altitude, accuracy of equipment, accuracy of evaluation (the chances of a exact 180 or 150 reading are nil), attention of mechanic etc.etc.
If you are really that bothered then buy / hire a quality compression tester and diy.

[aaronjb]

Hmm, wondering if ive done this wrong and if Im going to have to re-test the bloody thing. Which would be a colossal pain in the arse.

I did as the guide on the back of the tester seemed to instruct which was to remove 1 spark plug in turn, test the chamber and then reinstall and test the next.

So at the time of the chamber testing there were 3 chambers running as normal, with spark plugs and ignition coils inside. And 1 with the compression tester in.

Please tell me this wont have affected the figures because it took getting a bloody half day off work to get this done in the bloody first place!

The advice I've always been given has been to:

1) Pull all the spark plugs (you want as little cranking resistance as possible to build pressure without flattening the battery)
2) Pull the fuel pump fuse, injector fuse or another fuse that will stop the injectors from firing and filling the cylinders with petrol as you test - that'll just flood the cylinder and potentially falsely inflate the compression readings (either due to the liquid sealing badly sealing rings or taking up cylinder volume)

Given the figures you got I probably wouldn't bother going to the hassle of testing it again, though - it's unlikely to drop 60psi, and would most likely just come down to roughly optimal.  There's a bit of a variance between cylinders but it's in spec and could easily be down to the battery starting to struggle as it was working against the spark plugs the whole time.

Oh yes, I was always told to do the test on a warm engine, too .. although that always struck me as potentially painful!

[muffdan]

Above 200psi: http://www.mr2roc.org/phpBB3/viewtopic.php?f=11&t=28676&p=352573&hilit=compression#p352573
200psi: http://www.mr2roc.org/phpBB3/viewtopic.php?f=7&t=27017&p=332681&hilit=compression#p332681
216psi: http://www.mr2roc.org/phpBB3/viewtopic.php?f=11&t=24707&p=306616&hilit=compression#p306616
Just over 200psi: http://www.mr2roc.org/phpBB3/viewtopic.php?f=11&t=23507&p=292618&hilit=compression#p292618
215psi: http://www.mr2roc.org/phpBB3/viewtopic.php?f=35&t=22859&p=279021&hilit=compression#p279021

Standard compression is around 11.1:1 maybe? (I honestly can't remember but that's the number I have in my head). I run 8.8:1 (which is sold as LOW COMPRESSION) and I make 175psi. Some simple math gives: 11.1 / 8.8 * 175 = 220psi for the stock pistons. I dunno if that math is valid but the numbers do look nice!

Anyway, I believe the BGB states that burning 1 litre of oil every 600 miles is acceptable too.   s:? :? s:?   Just because the BGB says something, doesn't mean its good. I personally believe the consumption figures (and probably the compression figures) are there to give Toyota more wriggle margin before a warrantee claim can be made. It has to be really bad before they'll act. I would expect an engine making 150psi across all cylinders is going to be significantly down on power. Toyota will officially claim nothing is wrong as everything is 'within tolerance'.

[Ilogik]

I had Rogue check my engine when it was bought and once again when the thermostat broke. Both times 220 on all 4. N/A are high compression, my old turbo with forged internals was making 170, so i really don't agree with it being the best. I do have a 2zz though   s:D s:D    s:D s:D  But my old na was 200 or 215.

[aaronjb]

Here's the procedure from the BGB, incidentally (it doesn't mention stopping the injectors from firing):

1.   WARM UP AND STOP ENGINE Allow the engine to warm up to normal operating temperature.
2.   REMOVE IGNITION COILS (See page IG–4)
3.   REMOVE SPARK PLUGS
4.   INSPECT CYLINDER COMPRESSION PRESSURE
(a)   Insert a compression gauge into the spark plug hole.
(b)   Fully open the throttle.
(c)   While cranking the engine, measure the compression pressure.
HINT: Always use a fully charged battery to obtain engine speed of 250 rpm or more.
(d)   Repeat steps (a) through (c) for each cylinder.
NOTICE: This measurement must be done in as short a time as pos- sible.
Compression pressure: 1,270 kPa (13.0 kgf/cm2, 184 psi)
Minimum pressure: 1,000 kPa (10.2 kgf/cm2, 145 psi)
Difference between each cylinder: 100 kPa (1.0 kgf/cm2, 15 psi) or less


I honestly can't think of a good reason for Toyota to 'downplay' the compression figures, though, as is being suggested.. they've nothing to gain since it's not a number oft quoted to the public   s:?: :?: s:?:  Maybe all those high readings are just badly calibrated compression testers.. maybe all of Toyota's testers read low. Who knows. I certainly don't recall that any 1ZZ variants run lower compression (they do, however, run different diameter valves)

[muffdan]

I certainly don't recall that any 1ZZ variants run lower compression (they do, however, run different diameter valves)

Pure speculation on my part, just trying to give Toyota the benefit of the doubt and think of a reason why they have 184psi in black and white! I've recorded over 200psi myself when I was stock.

Is it possible to over-read through bad procedure?

Someone with a compression test should go outside right now and test their engine.  s:D s:D

[Anonymous]

2 of those are the same person,last link doesnt work.No proof equipment was calibrated so could easily be reading 15 psi high,personally I'm going with Toyota on this one as they designed and built every engine we're driving.

[aaronjb]

Is it possible to over-read through bad procedure?

Yes.. but I thought it read lower when cold (and the book advice is warm, which would simply mean it's even more wrong - assuming the OP here did his test cold and yours was probably done hot).. Or maybe yours and his were done 'hot hot' and the book means 'luke warm' ..

It doesn't exactly specify a temperature   s:lol: :lol: s:lol:  Though the mention of 'as quickly as possible' and to get it to normal operating temperature implies it would be consistent.

If I had a compression tester.. well, maybe not right now, neighbours wouldn't be best pleased!

[mrzwei]

So what exactly would you do if your readings were 180 on three and 150 on the other one?

[aaronjb]

So what exactly would you do if your readings were 180 on three and 150 on the other one?

I'd do exactly what you said earlier  s;) s;)  (test with oil in the chamber, if it rises, look and see how much oil I'm using and if it's unacceptable.. budget for repair/replacement. If it's not, ignore it and continue on until such time as the need arises to repair/replace)

[Ilogik]

Ill go with a specialist who builds them day in day out, with high power builds, ever taken your car to Toyota, need I say more   s:lol: :lol: s:lol:  You know Toyota are clueless when they call the specialist you take your car to for advice.   s:lol: :lol: s:lol:

[Anonymous]

Ill go with a specialist who builds them day in day out, with high power builds, ever taken your car to Toyota, need I say more   s:lol: :lol: s:lol:  You know Toyota are clueless when they call the specialist you take your car to for advice.   s:lol: :lol: s:lol:

Yes we know you do a little sex wee when you think of Rogue but you can't confuse the people who designed the engine/manual with the dealerships.

[muffdan]

Oops, last link is only available to mods as it's a for sale post that was automatically deleted a long time ago.   s:oops: :oops: s:oops:  

Here's part of the post by markiii

the turbo actually means you use less revs so you could argue that equals less strain, however the engine is just dandy.  :-) :-) :-)  she compression tested at 215 PSI or thereabouts across the board.

There were plenty more posts but I got bored so stopped collecting. Can all those compression testers be that far out? All of them over reading and not under reading? Are we going to ignore that Toyota's BGB also states that 1 litre of oil loss over 600 miles is absolutely fine? (Toyota would not repair under warrantee my first engine until they proved it was using more oil than this). I seem to remember that Toyota's wheel alignment tolerances are also very very generous and in some people's opinions dangerous.

Toyota have shown that some of their tolerances are questionable and therefore all of them should be taken with a pinch of salt IMHO. Real world measurements by reputable garages provide evidence that a healthy engine generates ~210 psi. I think this is definitely something worth considering. Everyone is certainly entitled to believe what they want to believe though so make your own mind up.   s:) s:)

[Anonymous]

I think I may do mine on Saturday trying a couple of different methods to see if and how much there is a difference depending on procedure taken.

[calaerial]

I personally would be quite interested to hear about this, as i do worry that my variation from the usual testing method may have skewed the results.

But on balance it doesnt really matter too much i would say. If the chamber is capable of generating 220/210PSI, then there isnt a leak.  Whether it generates that compression when actually running isnt relevant to the diagnosis of a head/piston ring fault surely?

Compression is compression.

[ChrisGB]

Just wondering if the difference in results people are seeing is difference between wet or dry test?

Chris

[Cap]

The Difference is Cam Design, and the positioning of the VVTi Sprocket..  

Early Cams have a different grind and generally have higher pressures than late cams..  the Change was in late '02..  

And where the VVTi likes to sit when at rest, appears to be a Factor..  

It's the Variance of the Pressures that tells the Real Story, as the 'Damage' will not happen to all Cylinders Equally..

Here are my Compression Numbers at 100 and 140 K Miles..  


and my Factory Plugs at 140 K Miles..  


Car now has 180K Miles..  Original Plugs..  I did have to gap them once..  

Cap

[mrzwei]

So now we have Ilogik, muffdan and cap all quoting pressures in the 200+ range.
Possible differences quoted are early engines with longer duration or higherlift cams and later engines with larger inlet valves. Both would have the effect of allowing more mixture to be sucked into the cylinder and so require more pressure to be applied to compress said mixture (my physics is crap but that would be my lay understanding of the process). My thoughts are that the engine modifications would tend to cancel each other out and that the figures should be roughly the same for both pre and post facelift. Also, no BHP or torque differences are quoted pre / post by Toyota as far as I'm aware.
I'm certainly not going to ignore peoples' actual readings because this is the best evidence you can get. I would check my own but have a gauge more suited to old style ohv classics rather than ohc motors (now I know what I should have asked for for Christmas   s:lol: :lol: s:lol:  ).

 Two debates here really, do you just use the car as a daily driver / weekend fun motor, or are you looking to tune it, turbo it or race it?
If the former, then use the factory figures and if the latter then it seems you may want to be a bit more fussy. Just remember that there are endless variables that need to be taken into account and the costs associated with solving any problem.

Lastly, as has been illustrated, use the plug condition evidence to support  an isolated low reading on a cylinder (for example if enough oil is getting past the rings then that plug may show signs of oiling up).

[Cap]

Correction:

Pre and Post face lift have the Same Valve Size..  

Information:

Usually 'More Cam' will give you less Cranking Compression Numbers.. But Higher HP at the Top End..  

EDIT:..  here are the Known engine mods and the Date of them..  

06/01 New S-belt Tensioner
11/01 New Piston Rings & harmonic balancer
12/01 New pistons
02/02 New Longblock
04/02 New oil pickup
06/02 New Oil pump
07/02 New Water pump
10/02 New Cams.

Cap

[Ilogik]

Alright Cap the voice of reason, and my very helpful knowledge base when my car was running rich.

[Anonymous]

OK went to do a few comparison tests this morning,removed brace,cover,coils etc and then found no spark plug sockets I have will fit.  s:scared: :scared: s:scared:    s:evil: :evil: s:evil:  

Edit: I've done a bit of searching and will this do the job?

 m http://cgi.ebay.co.uk/Spark-Plug-Socket ... 2106wt_905 m

[ChrisGB]

More valve overlap = less measured compression.

Chris

[mrzwei]

More valve overlap = less measured compression.

Chris

Yeah, I get that now. That would shift the torque curve to the right as well?
That was good info from cap I have to say and given the dates quoted my engine may just have the revised piston design etc.

[mrzwei]

Edit: I've done a bit of searching and will this do the job?

 m http://cgi.ebay.co.uk/Spark-Plug-Socket ... 2106wt_905 m

That should do the job but I got mine from Halfords (blue 'T'' handled thing with a flexible connection). No idea of the price now though.

[filcee]

Is it possible to over-read through bad procedure?

Warning: I am not an engineer, so make of this what you will ...

I suspect that getting the process wrong will cause readings to be 'different' to those that might be expected.  However, Toyota state 184psi +- 15psi. Someone else has quoted a range of 169 - 199 psi as being 'within tolerance'.  Now, if the kit itself is not calibrated, it might be reasonably be expected to have some error factor 'built in'.  Let' say 10%, just to keep the numbers easy.  This gives a range of approx. 153 - 219 psi - and now we're starting to see numbers at the "extremes" of those quoted on here.  If a "bad procedure" is introduced, this might make further variation to these numbers - and we'll get even more extreme figures at the boundaries.

Would we be better, with uncalibrated equipment/amateur approach (apologies to those who are more knowledgeable and experienced than me) to look at the percentage variation between cylinders as read by the current compression test device:  184 psi +- 15psi is about an 8% variation, anything outside of this should be viewed as 'suspect'.  Any truly wacky numbers - lets say outside of the +-15psi range with an added (or subtracted) 10% in view of using uncalibrated equipment should be a strong indicator of the need to get things checked by someone you trust using equipment that can be considered of good quality and well calibrated.