Poor cylinder compression on new built motor - what to do?
Poor cylinder compression on new built motor - what to do?
Just been having a crazy run of issues here with this new motor.
Running a built block with APS ST w/ UniChip, RC 550cc inj. with Arias ED 9:1 and Eagle Rods; motor has about 300 mi. on it now.
When first installed, it was running well at idle and cruise, but very sloppy on the upper end (very rich). Stayed out of it until I had about 250mi. on the car and took it to DynoComp in Scottsdale.
Tuner was not able to find the coarse/fine fuel trim adjustment for UniChip, so during this session he was unable to take much fuel out of it. Additionally, he said I was experiencing spark blow out with 0.035” gapping (PLFR6 plugs) and to take it home, regap at 0.028” and come back after he had a chance to talk to UniChip.
So, plugs were cleaned and regapped, and coils pulled and tested to assure each was firing.
Took it back, adjusted the fuel trim per UniChip, and we were on our way to a happy tuning session…
...or not
Car made ~390hp (DynoDynamics) at 11psi with an AFR curve that looked like *** (very jagged). Tuner states that I may have either an injector problem (stuck/closed/whatever) and the I may still be experiencing spark blowout, or I have a weak ignition setup. We weren't able to proceed any further because the friggin' line to the wastegate burned through (intelligent APS design, no doubt).
I was sent back with the directive that I:
So, yesterday I ordered HKS’ Twin Power DLI II Amplifier and pulled the injectors to get sent to RC. Tonight, I had a chance to perform a compression check:
Cylinder psi
1 130
2 140
3 145
4 145
5 150
6 145
Curious, I rechallenged the compression test to validate what I saw on Cylinder 1. Results were:
Cylinder psi
1 100
2 140
3 145
4 145
5 145
6 145
WTF?!?!
Put a little oil in Cylinder 1; next reading came back at 180psi.
So, I guess now what?
I have not contacted the builder (Todd @ BuiltZMotors) as to what to do or how significant this issue is. After 300 mi., the rings should be seated almost completely by now. The car does not smoke, and has no observable symptoms other than some freakish’ tuning sessions.
Is the difficult tuning a result of poor compression on Cyl1 or is it more ‘tuner related’? I was at the point, after having talked with Sam @ GTM on the phone, that I would take a day off and drive to Calif. for a GTM tune.
My worry is whether I am facing the reality that I may have a bad motor? Is there a method/product that can be introduced into the Cylinder to promote seating? I’m completely lost, and I’m not sure what to do with the data I have in front of me…
Any help is appreciated.
Running a built block with APS ST w/ UniChip, RC 550cc inj. with Arias ED 9:1 and Eagle Rods; motor has about 300 mi. on it now.
When first installed, it was running well at idle and cruise, but very sloppy on the upper end (very rich). Stayed out of it until I had about 250mi. on the car and took it to DynoComp in Scottsdale.
Tuner was not able to find the coarse/fine fuel trim adjustment for UniChip, so during this session he was unable to take much fuel out of it. Additionally, he said I was experiencing spark blow out with 0.035” gapping (PLFR6 plugs) and to take it home, regap at 0.028” and come back after he had a chance to talk to UniChip.
So, plugs were cleaned and regapped, and coils pulled and tested to assure each was firing.
Took it back, adjusted the fuel trim per UniChip, and we were on our way to a happy tuning session…
...or not
Car made ~390hp (DynoDynamics) at 11psi with an AFR curve that looked like *** (very jagged). Tuner states that I may have either an injector problem (stuck/closed/whatever) and the I may still be experiencing spark blowout, or I have a weak ignition setup. We weren't able to proceed any further because the friggin' line to the wastegate burned through (intelligent APS design, no doubt).
I was sent back with the directive that I:
- Pull the injectors and send to them to RC to get flow tested/cleaned
- Amplify the ignition system somehow
- Perform a compression check
So, yesterday I ordered HKS’ Twin Power DLI II Amplifier and pulled the injectors to get sent to RC. Tonight, I had a chance to perform a compression check:
Cylinder psi
1 130
2 140
3 145
4 145
5 150
6 145
Curious, I rechallenged the compression test to validate what I saw on Cylinder 1. Results were:
Cylinder psi
1 100
2 140
3 145
4 145
5 145
6 145
WTF?!?!
Put a little oil in Cylinder 1; next reading came back at 180psi.
So, I guess now what?
I have not contacted the builder (Todd @ BuiltZMotors) as to what to do or how significant this issue is. After 300 mi., the rings should be seated almost completely by now. The car does not smoke, and has no observable symptoms other than some freakish’ tuning sessions.
Is the difficult tuning a result of poor compression on Cyl1 or is it more ‘tuner related’? I was at the point, after having talked with Sam @ GTM on the phone, that I would take a day off and drive to Calif. for a GTM tune.
My worry is whether I am facing the reality that I may have a bad motor? Is there a method/product that can be introduced into the Cylinder to promote seating? I’m completely lost, and I’m not sure what to do with the data I have in front of me…
Any help is appreciated.
Last edited by JoeDirtPharmD; Jun 6, 2007 at 01:08 AM.
Did you break the motor in on synthetic oil? Synthetic oil will likely extend the time needed to break in the motor. But Sam @ GTM is the one to talk to not us here.
JET
JET
Last edited by JETPILOT; Jun 5, 2007 at 11:51 PM.
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ring will seat within the first few miles. A rich tune can wash out the rings. A good startup tune is a must for running in any built engine.250miles is wayyyy to long, damage was done a long time ago. I always run mine in on the dyno.
Not that it is important..... but my boat motor had #8 cylinder not sealing properly recently. Compression was down. I filled it with a little oil, and I warmed up the motor, and the ring sealed and compression was fine.
JET
JET
Breaking in the engine with 0w30 regular oil. The first 20 mi. or so were mid-range driving with plenty of engine braking, varying the RPM loads and not exceeding about 5k rpms. At no time during the first 20 mi. did I romp on it enough to see an overtly rich condition. Between 20 - 50 mi. I jumped on it a bit but kept my foot out of the boost.
At 50mi. I did an oil change - same oil (0w30) and drove it more aggressively until I noticed it was bogging out at high RPMs and it was pig-rich. At 100mi. I took it for it's first tune.
The compression test this evening was done on a cold motor - but regardless I would have expected all the ranges to be close to eachother.
So - the big question is what to do about my compression in this one cylinder.
EDIT: The plug for Cyl 1 looks the same as the others; no oil contamination or signs of fouling. Also, during the secon tuning session, they ran a little Cipher/Consult-like tool and took down each cylinder during idle. They found:
Cylinder / rpm drop
1 / 0
2 / 25
3 / 25
4 / 12
5 / 12
6 / 12
Not sure how significant this information is, but more data for someone that knows...
At 50mi. I did an oil change - same oil (0w30) and drove it more aggressively until I noticed it was bogging out at high RPMs and it was pig-rich. At 100mi. I took it for it's first tune.
The compression test this evening was done on a cold motor - but regardless I would have expected all the ranges to be close to eachother.
So - the big question is what to do about my compression in this one cylinder.
EDIT: The plug for Cyl 1 looks the same as the others; no oil contamination or signs of fouling. Also, during the secon tuning session, they ran a little Cipher/Consult-like tool and took down each cylinder during idle. They found:
Cylinder / rpm drop
1 / 0
2 / 25
3 / 25
4 / 12
5 / 12
6 / 12
Not sure how significant this information is, but more data for someone that knows...
Last edited by JoeDirtPharmD; Jun 6, 2007 at 01:16 AM.
hmmm...
some will argue that because of the composition of the arias ED piston rings (chrome) that they will not completely seat until up to 2000 miles of driving. The fact that you can put a little oil in the cylinder and the compression comes up typically indicates that the rings on cylinder #1 are not sealing as well as the others....
my advice for now: it is pretty difinitive with the oil in the cylinder test that the rings are simly not sealing as well as the others (vs a valve sealing or some other compression leakage elsewhere)...
I know some throw their vehicles on the dyno after only a few hundred miles and run them hard immediately.. in this case, i would drive a few hundred more miles- out of boost- and then check the compression again...
The rings uses on the arias ED pistons are some of the best out there! the cylinder bore/hone is within a few ten thousandths of an inch per cylinder and the ring end gaps are within one thousandth of each other, so from a machining/assembly standpoint, each cylinder should be identical- unfortuntely, there are several other variables when taking an engine from brand new- to- broken in and start hammering on it...
hopefully there wasn't an issue with an injector being stuck open, or spraying significantly more fuel during the break in process- this could wash a cylinder of its oil and allow the rings to scar the cylinder and prevent proper sealing---in some cases, this situation can resolve if the rich condition is corrected and then the car is driven gingerly to allow the cylinder to seal properly in an oiled cylinder...does the oil have a significant fuel smell to it?
I have seen problems with RC injectors on a few occasions, ususally stuck open...in these cases, the plugs wer enot significantly fowled, but since i run dual bank AFR, i would see a significant difference from side to side- and at times, the AFR was identical at WOT and 3/4 throttle, but anything below that would be significantly richer on one side vs the other..did you test the injectors yet? pull off the fuel rail with the injectors in place, make sure you cover the engine and manifold/whatnot so you dont get fuel everywhere...turn the key and let the fuel pressure buld and see if one injector is dripping/leaking...if this is inconclusive, you can have the injectors tested (we do this at our machine shop)- injectors can be plugged in and pulsed and you can measure the output between ech injector and determine if one is acted irregularly.
as a safety precaution, make sure that the injectors are consistant first- i would stay out of boost and recheck in 300 miles to see where the compression is at...good luck, let me know if there is anything i can do!
-TODD
some will argue that because of the composition of the arias ED piston rings (chrome) that they will not completely seat until up to 2000 miles of driving. The fact that you can put a little oil in the cylinder and the compression comes up typically indicates that the rings on cylinder #1 are not sealing as well as the others....
my advice for now: it is pretty difinitive with the oil in the cylinder test that the rings are simly not sealing as well as the others (vs a valve sealing or some other compression leakage elsewhere)...
I know some throw their vehicles on the dyno after only a few hundred miles and run them hard immediately.. in this case, i would drive a few hundred more miles- out of boost- and then check the compression again...
The rings uses on the arias ED pistons are some of the best out there! the cylinder bore/hone is within a few ten thousandths of an inch per cylinder and the ring end gaps are within one thousandth of each other, so from a machining/assembly standpoint, each cylinder should be identical- unfortuntely, there are several other variables when taking an engine from brand new- to- broken in and start hammering on it...
hopefully there wasn't an issue with an injector being stuck open, or spraying significantly more fuel during the break in process- this could wash a cylinder of its oil and allow the rings to scar the cylinder and prevent proper sealing---in some cases, this situation can resolve if the rich condition is corrected and then the car is driven gingerly to allow the cylinder to seal properly in an oiled cylinder...does the oil have a significant fuel smell to it?
I have seen problems with RC injectors on a few occasions, ususally stuck open...in these cases, the plugs wer enot significantly fowled, but since i run dual bank AFR, i would see a significant difference from side to side- and at times, the AFR was identical at WOT and 3/4 throttle, but anything below that would be significantly richer on one side vs the other..did you test the injectors yet? pull off the fuel rail with the injectors in place, make sure you cover the engine and manifold/whatnot so you dont get fuel everywhere...turn the key and let the fuel pressure buld and see if one injector is dripping/leaking...if this is inconclusive, you can have the injectors tested (we do this at our machine shop)- injectors can be plugged in and pulsed and you can measure the output between ech injector and determine if one is acted irregularly.
as a safety precaution, make sure that the injectors are consistant first- i would stay out of boost and recheck in 300 miles to see where the compression is at...good luck, let me know if there is anything i can do!
-TODD
Last edited by 350zDCalb; Jun 6, 2007 at 06:13 AM.
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The first issue, is trying to tune this thing with the Unichip. 550cc injectors are beyond the scope of what the Unichip can "comfortably" control. So as far as the tune goes, I would suggest switching to the UTEC.
In regards to compression, these rings do take longer, and require a more aggressive, and methodical break-in process. The variance is unusual, but so is the fact that your technician got different numbers when he rechecked that cylinder.
Hope that helps.
In regards to compression, these rings do take longer, and require a more aggressive, and methodical break-in process. The variance is unusual, but so is the fact that your technician got different numbers when he rechecked that cylinder.
Hope that helps.
Big thanks to everyone that's responded and to Todd @ BuiltZMotors for taking the time to follow-up with me!
I ran a borescope down the intake runner last night: can see crosshatch marks with normal carbon buildup in the upper wall of the cylinder. The 'utility' part of the cylider walls do not have a glazed/mirror/glossy finish so I'm holding out hope that glazing has not *fully* occurred and that I can still salvage this cylinder. Todd gave me specific instructions to further break-in the motor so I'll keep my fingers crossed...
My thoughts are I rec'd a faulty/open injector that was likely leaking into the cylinder(?)
So, where I'm at this morning:
• Injectors are at RC getting refurb'd
• Purchased UTEC with MAP selector/sensor
• Purchased HKS ignition amplifier
• Purchased new LFR6 plugs
• Prayed alot
After I've put a base MAP on the car and ran her for 300 - 500 mi., then I'll source out a STRONG tuner for a finishing touch.
I ran a borescope down the intake runner last night: can see crosshatch marks with normal carbon buildup in the upper wall of the cylinder. The 'utility' part of the cylider walls do not have a glazed/mirror/glossy finish so I'm holding out hope that glazing has not *fully* occurred and that I can still salvage this cylinder. Todd gave me specific instructions to further break-in the motor so I'll keep my fingers crossed...
My thoughts are I rec'd a faulty/open injector that was likely leaking into the cylinder(?)
So, where I'm at this morning:
• Injectors are at RC getting refurb'd
• Purchased UTEC with MAP selector/sensor
• Purchased HKS ignition amplifier
• Purchased new LFR6 plugs
• Prayed alot
After I've put a base MAP on the car and ran her for 300 - 500 mi., then I'll source out a STRONG tuner for a finishing touch.
Last edited by JoeDirtPharmD; Jun 7, 2007 at 09:15 AM.
Blahhhhhhhhhh...
So where I'm at from the last time:
- Injectors were sent to RC - their inspection report that came back said all 6 injectors were flowing properly between 48 - 51 with excellent spray pattern with no observation of any injectors being stuck open. So injectors don't seem to be an issue, I guess...
- Rec'd new plugs - gapped them at 0.035"
- Added the HKS Ignition amplifier
- Drove the car ~500 mi. around Phoenix over the past couple weeks without hammering on it (resisting the urge to smash it was almost unbearable).
- Performed another oil change - oil quality looks good, no gas smell, etc.
- Purchased UTEC, and drove it to GTM on Tuesday (+320 mi. from house).
So, lemme start by saying Sam and the rest of the folks at GTM are remarkable and very thorough - can't say enough great things about the shop and my limited experience thus far.
Somewhat embarrassed about taking the Z over to GTM - there's still an incredible amount of finish work to do (cut/buff the repainted front end, install plastic fenderwell underskirts, center dash assembly, etc.) but I was anxious to get the 'performance' issues out of the way.
I had GTM install the UTEC and was advised to install an EGT gauge at the same time. So that was done...
I guess the good news is the car makes a tad over 400rwhp at 4500rpm at 9psi. However, the horsepower curve takes a dump after 5500 rpms - looks almost parabolic in nature - down to low 300's by 6500 rpms. No bueno.
More concerning is that when the boost was increased to 15psi - there was no increase in horsepower at all
By the end of Wednesday, Sam had ruled out anything related to tuning. I decided to leave the car at GTM so they can perform a compression/leakdown test and go through the entire car looking for the gremlin(s). I'm concerned that cylinder #1 is still culprit, even after 1,300 mi on the motor...
Anyways, I ended up catching a last-minute flight from LAX to PHX so I can return to work on Thursday. GTM stated they may have a definitive cause for me within the next couple days, and we'll see where to go from there.
I just felt on leaving the car at one shop instead of having everyone's hand in the cookie jar on this one. I would go through the car myself, but it's a time constraint issue for me... and the fact that I've reviewed every variable myself and I can't think of what else to do on this thing
Soooooooo... that's that for now. Will keep everyone updated as things unfold...
So where I'm at from the last time:
- Injectors were sent to RC - their inspection report that came back said all 6 injectors were flowing properly between 48 - 51 with excellent spray pattern with no observation of any injectors being stuck open. So injectors don't seem to be an issue, I guess...
- Rec'd new plugs - gapped them at 0.035"
- Added the HKS Ignition amplifier
- Drove the car ~500 mi. around Phoenix over the past couple weeks without hammering on it (resisting the urge to smash it was almost unbearable).
- Performed another oil change - oil quality looks good, no gas smell, etc.
- Purchased UTEC, and drove it to GTM on Tuesday (+320 mi. from house).
So, lemme start by saying Sam and the rest of the folks at GTM are remarkable and very thorough - can't say enough great things about the shop and my limited experience thus far.
Somewhat embarrassed about taking the Z over to GTM - there's still an incredible amount of finish work to do (cut/buff the repainted front end, install plastic fenderwell underskirts, center dash assembly, etc.) but I was anxious to get the 'performance' issues out of the way.
I had GTM install the UTEC and was advised to install an EGT gauge at the same time. So that was done...
I guess the good news is the car makes a tad over 400rwhp at 4500rpm at 9psi. However, the horsepower curve takes a dump after 5500 rpms - looks almost parabolic in nature - down to low 300's by 6500 rpms. No bueno.
More concerning is that when the boost was increased to 15psi - there was no increase in horsepower at all
By the end of Wednesday, Sam had ruled out anything related to tuning. I decided to leave the car at GTM so they can perform a compression/leakdown test and go through the entire car looking for the gremlin(s). I'm concerned that cylinder #1 is still culprit, even after 1,300 mi on the motor...
Anyways, I ended up catching a last-minute flight from LAX to PHX so I can return to work on Thursday. GTM stated they may have a definitive cause for me within the next couple days, and we'll see where to go from there.
I just felt on leaving the car at one shop instead of having everyone's hand in the cookie jar on this one. I would go through the car myself, but it's a time constraint issue for me... and the fact that I've reviewed every variable myself and I can't think of what else to do on this thing
Soooooooo... that's that for now. Will keep everyone updated as things unfold...
Originally Posted by failsafe306
If you absolutely HAVE to keep the Unichip, have TS reflash for the larger injectors. Before the fcon and 1000cc's, I was running the Unichip with flashed ECU and RC650's, FWIW.
+1 good luck
Im sorry to read this. Stick with it, things like this happen occasionally, I know GTM will take care of you. Good luck, keep us posted.
I run the unichip on mine, and although it's not the greatest, it gets me by. I'm running 650cc injectors with it. I'm at 12psi putting out decent power.. do you have the stock ignition? unichip to utec isn't much of an upgrade imo.. I'm going fcon next year and turning up the boost a notch or 2..
