DISI Compression Results

[ms3blackmica]

Alright I re-checked compression with all the spark plugs pulled this time. Much more consistent #'s now.

205
205
205
205

[Lex]

How many times did you crank?

[ms3blackmica]

Originally Posted by Lex How many times did you crank?

once it stopped, i stopped cranking.

it was only a few seconds

[ManMan]

Just checked mine

2007 w/ 88600mi. 190 +/-5 across all four cylinders

[Lex]

Originally Posted by ManMan Just checked mine 2007 w/ 88600mi. 190 +/-5 across all four cylinders

Sounds healthy and ready for more modifications

[TRSpeed]

Nice numbers. I don't even want to check mine :/

Sent from my DROID4 using Tapatalk 2

[blackrs99]

Checked mine on Sunday, car has 45k and is fully bolted + tuned, the results were:

(passenger)
189
187
185
180

[Snotrocket]

0-190-190-195


TappaFak

[theurgy]

Originally Posted by Snotrocket 0-190-190-195 TappaFak

LOL Ouch.

[jack_hammer]

Woops

Probably sent from a toilet

[timjs]

Performed a compression test. 84k miles. Intake, internals, and freek tune in progress.

185, 185, 170, 185.

@Lex;

I have seen many DISI engines with exactly 150psi on cylinder 3 at work. (I compression test every engine I do timing chain/VVT work on, or remove the cylinder head, ect)

The engines have all run fine and make no noises.

As you can see, MY engine is developing low(er) compression on #3 .

I have searched my ass off for 45 minutes reading hundreds of posts on this forum and it would seem ring land failures are possible.

Since creating this thread (which I have not read completely through, out of time) has there been ANY progress on discovering what the hell is up with cylinder 3?
It's gotten to the point that I EXPECT 150 psi when I'm doing these compression tests now.

Thank you sir.

[Tokay444]

Cylinder three has the highest flow through the highly imbalanced intake mani and since we don't have individual o2 sensors in each exhaust port, fuel delivery is averaged over all 4 cylinders, and 3 runs lean.

[Dano]

he speaks the truth.

I would be willing to bet any that you test out in the 150 range, compared to others in the 180s has a broken ringland...or bent rod but you can check for piston height while doing the compression checks to confirm a severely bent rod with just a long screwdriver...slightly bent rod may require a dial gauge.

that is exactly what my compression numbers looked like and I have torn my motor down to confirm a broken ring land in #3 .

Since I am here I'll report my new numbers.

150 miles on the new motor with it fully warmed up

182 - 182 - 182 - 182

[ms3blackmica]

Glad to see you back up and running Dano !

Consistent compression is consistent! lol

[Dahouse702]

Did this a few months back at about 65k miles in a 2007 ms3 mods are in sig.

Dry

1-171
2-155
3-160
4-175






Wet

1-180
2-160
3-165
4-181

[timjs]

Originally Posted by Tokay444 Cylinder three has the highest flow through the highly imbalanced intake mani and since we don't have individual o2 sensors in each exhaust port, fuel delivery is averaged over all 4 cylinders, and 3 runs lean.

I see. Could you link to some hard evidence of this? Yes, I searched but came up empty.
I've never noted any signs of lean running on spark plugs or pistons. Or even exhaust valves on the engines I removed the head from. It would make sense though. I have a spare exhaust manifold, and an Innovate wideband. It would be very interesting to install a bung on each runner and actually get A/F measurements per cylinder. Has that been done yet as far as you know?

Originally Posted by Dano he speaks the truth. I would be willing to bet any that you test out in the 150 range, compared to others in the 180s has a broken ringland...or bent rod but you can check for piston height while doing the compression checks to confirm a severely bent rod with just a long screwdriver...slightly bent rod may require a dial gauge. that is exactly what my compression numbers looked like and I have torn my motor down to confirm a broken ring land in #3 . Since I am here I'll report my new numbers. 150 miles on the new motor with it fully warmed up 182 - 182 - 182 - 182

I checked mine with dial calipers, no piston height discrepancies.
The ring land issue. It seems so likely.
150psi on 3rd.. So common it's ridiculous.

[Tokay444]

When the intake manifold was flow bench baselined it's was 24% imbalanced across all 4. Lol. 3 being the highest flowing.
From my phone it's going to be hard to get you a link.
Seems the heat of running lean leads to piston rings butting together at the gap. Something has to give.
SilverDemon/JM Fabrications Intake Manifold Interest Thread
First post has the numbers.

[R.MS3]

Any word of this compression problem on #3 for the genpu's? I've been away since i sold my 07 MS3 a couple of years ago but interested in joining again by the summer.

[Dano]

Originally Posted by ms3blackmica Glad to see you back up and running Dano ! Consistent compression is consistent! lol

yes it damn well better be with all the work I did... esp in #3 cylinder to get it cleaned up proper!

time will tell how it holds up.

Originally Posted by timjs I see. Could you link to some hard evidence of this? Yes, I searched but came up empty. I've never noted any signs of lean running on spark plugs or pistons. Or even exhaust valves on the engines I removed the head from. It would make sense though. I have a spare exhaust manifold, and an Innovate wideband. It would be very interesting to install a bung on each runner and actually get A/F measurements per cylinder. Has that been done yet as far as you know? I checked mine with dial calipers, no piston height discrepancies. The ring land issue. It seems so likely. 150psi on 3rd.. So common it's ridiculous.

not only that but if my #3 cylinder wall is any indication of the larger data sample, they get pretty warped due to all the heat.

PWC bore measurements can be found in my thread.

http://www.mazdaspeedforums.org/foru...09/index5.html

[timjs]

Originally Posted by Tokay444 When the intake manifold was flow bench baselined it's was 24% imbalanced across all 4. Lol. 3 being the highest flowing. From my phone it's going to be hard to get you a link. Seems the heat of running lean leads to piston rings butting together at the gap. Something has to give. SilverDemon/JM Fabrications Intake Manifold Interest Thread First post has the numbers.

Thanks for the link. I might have missed it but did they flow test an unmodified intake?
I see results there for a ported stock manifold, but the results show that cylinder two actually flows the most, followed by 3.

Since the O2 sensor get an average of the four because it's reading all four exhaust streams, I look at it like this.
The average CFM per intake runner per that test, is 222.75 CFM.
Cylinder 3's result of 233 is only 4.4% higher than average. You could *theorize* that results in an actual AFR only 4.4% leaner.
Even still, cylinder 2 would be leaner yet.
All of this means squat since it was one test on one machine of a non-stock manifold since it was ported.

I'm not sure how conclusive that is. The only 100% for sure test would be individual bungs in each exhaust runner with a standalone wideband to check actual AFR.
If my car wasn't my daily I'd love to do this test with my extra exhaust manifold.

Are there any other tests done to verify the claim of lean on cylinder 3?
Not saying it isn't correct, it's just that one test on a ported manifold doesn't hold much water.

[Dano]

go to maperformance.com...lookup their intake for the MS3/6 and you will find all the flow data you seek.

[timjs]

Originally Posted by Dano go to maperformance.com...lookup their intake for the MS3/6 and you will find all the flow data you seek.

Will do thank you Dano.

Edit: Given that data, cylinder 3 is approximately 10% above the combined average for flow, and you could *theorize* once again that could equal #3 being approximately 10% leaner.

That, is significant. Thanks again for the information and links.
And I've always wondered why Mazda tuned this engine to be a soot-blowing dragon.

I still really would like to see an individual exhaust runner AFR test and may just do it myself. That is a project for another day however. ha

I also believe the ring gap closing is a possibility but what can we do but speculate?

[mrdouble99]

2009 speed3
77k km

1- 200 psi
2- 200 psi
3- 200 psi
4- 200 psi

[Tokay444]

Broken gauge.

[ms3blackmica]

Originally Posted by Tokay444 Broken gauge.

That's what I thought when I kept getting 205 and that was on a brand new snap on gauge.

I went over to my friends shop and used another snap on gauge, same #. I even tried a MAC gauge, same #'s.

I'm at 3 different gauges now showing the same lol

[Tokay444]

Weird that there would be that many broken gauges.

[Dano]

Originally Posted by timjs Will do thank you Dano. Edit: Given that data, cylinder 3 is approximately 10% above the combined average for flow, and you could *theorize* once again that could equal #3 being approximately 10% leaner. That, is significant. Thanks again for the information and links. And I've always wondered why Mazda tuned this engine to be a soot-blowing dragon. I still really would like to see an individual exhaust runner AFR test and may just do it myself. That is a project for another day however. ha I also believe the ring gap closing is a possibility but what can we do but speculate?

build a motor with OEM pistons and open up the ring gaps.

there is little doubt in my case the top ring butted causing the land failure.

[Dano]

Originally Posted by Tokay444 Weird that there would be that many broken gauges.

hahahahahahah


never seen a 200 before...ive hit 195 I believe in the heat of summer.

edit: strike that I have hit 190 before..

[Nitr0EngiE]

Originally Posted by Dano build a motor with OEM pistons and open up the ring gaps. OEM 1st ring is .003-.007 max of .010 = T I N Y there is little doubt in my case the top ring butted causing the land failure.

#1 195
#2 195
#3 196
#4 195

Built engine with about 13k miles on it i gapped rings to 23 thou

my wiseco pistons and rings are Boss

stock compression ratio 3 layer cometic HG

[Dano]

my wisecos are gaped as follows

1st = .018
2nd = .022

[ms3blackmica]

Originally Posted by Tokay444 Weird that there would be that many broken gauges.

ive just accepted it as actual.

only so many mechanic friends i can bug to let me borrow compression gauges from lol

[Nitr0EngiE]

i figured to be better safe then sorry and allow them more room to expand especially wanting to go over 500 HP in future, and with my high ass compression i dont regret it my gap is perfect.

believe it or not they dont even really leak down they hold the pressure.

[timjs]

Originally Posted by Dano build a motor with OEM pistons and open up the ring gaps. OEM 1st ring is .003-.007 max of .010 = T I N Y there is little doubt in my case the top ring butted causing the land failure.

Just curious, where did you get that info? Three thousandths would be out of spec.

This is out of the overhaul manual.
"Piston ring end gap
Standard
Top: 0.14—0.24 mm {0.0056—0.0094 in}
Second: 0.34—0.44 mm {0.0134—0.0173 in}
Oil (rail): 0.15—0.40 mm {0.0060—0.0157 in}
Maximum
1.0 mm {0.0393 in}"

Just trying to clear any confusion. Also, I do agree the low end of the spec is pretty tight and any engines that are AT the low end could have issues like you had.

[Dano]

I was incorrect you are correct.

[timjs]

Well if your gaps work for you, that's where I'm setting mine when the time comes, that's for sure.

[Dano]

for clarification...I am not running OEM pistons/rings.

If I were to run OEM pistons/rings I would run larger than spec...not sure exactly where I would land.

[Nitr0EngiE]

I got my specs from the wiseco instructions they show ring gaps for various power setups i.e natural aspirated, turbo, turbo with nos, nos the higher the expected power the bigger the gap

[Ziggo]

All of @Dano; s fail (my twin '08 red) and the talk of cracking ringlands from track use made me nervous enough to finally whip out the compression gauge.

'08 Speed 3, 48k miles, approx 20hr of track use, fully warmed up motor (oil temps ~180*F)

195-188-188-190

As for track use, I have been careful to shut it down when oil temps got above 240*F and have always used 40 weight oil.

[breakfasteatre]

Originally Posted by breakfasteatre 8k kms, waited for car to cool down so i could do the DP all 4 cylinders around 180

4 time attacks, and 31k kms now

passenger side to drivers side

180-180-180-165

oil bumps it back up to 180

doh

leak down test coming soon



on a side note, during time attack, oil temps would hit 260 and plateau, very quickly. Within a couple laps during test and tune
i did an oil analysis at some point and i was told the oil looked fine, high silica was the only problem, probably left the filter dirty too long

[sidekick]

I had a dealership do a compression test before I bought my car and they came back with:
190 - 165 - 150 - 175; I think I'm going to do it again when I change my spark plugs, because I don't really trust dealership techs. However, I'm just waiting for ZZB with that low compression on cylinder 3. That low compression did save me $2,000 though. Lol.

Originally Posted by ms3blackmica That's what I thought when I kept getting 205 and that was on a brand new snap on gauge. I went over to my friends shop and used another snap on gauge, same #. I even tried a MAC gauge, same #'s. I'm at 3 different gauges now showing the same lol

Have your head or block ever been machined? We ran a compression test on a friends miata after it was rebuilt and our #'s were 10PSI higher than the max spec. It was because the head was decked a few thousandths.