Cylinder Performance Test

[mwada]

Hello Everyone,

There are a lot of posts on iATN of using the PICO scope to check the relative cylinder performance of an engine. For the past few months I had the opportunity to use Snap-on's version (WavePoint) of this tool. It is a very quick and easy test. All that is needed are the connections to the battery and if you wanted to identify the cylinder, a trigger pickup to number one cylinder. At the present time, the only trigger pickup is with a pickup probe on a plug wire. In other words if there is no plug wire it will be difficult to find a trigger.

I believe PICO's version is a "capture and evaluate" method where the analysis is not real time but since I have never used one I could be wrong. Please correct me if I'm wrong. WavePoint is done live where you can view the evaluation as it is occurring. Instead of a bar graph (PICO), a waveform is displayed which can make the analysis difficult but maybe it could be just me. "Time" may make the analysis easier.

Here are a few examples while using this tester:

This is from a 1997 Astro Van with an injector that isn't opening on number 5 cylinder.

astro trigger.gif

The scan data confirms the misfire.

scandata.gif

Here is another one on a Cadillac with shorted injectors. We see shorted injectors on these Cadillacs at least one a month but because of the age of the vehicle and the cost of the repair we rarely get to do the repair. I find that the symptoms are always the same, a slight rough idle. I feel that if you tried to identify the bad cylinder (relative power balance) you may get misled into the proper diagnosis. As you can see by the cylinder performance test number 6 cylinder is being flagged.

injector1.gif

I was wondering, would this be something useful if it could be used with a MODIS?

[john4842]

Very

I would think it would be very useful

[DerekRWilliams]

Hmmm. as to the "no plug wire" triggering issue, I believe you could trigger off of #1 Coil Primary on a COP system. Haven't had to try it yet so I'm not sure but it does seem possible.

[MasterWrench]

I was shown once by the guys from "Pro-Tech" in a class how to do a cylinder balance test with the MODIS using the amps probe. Will look to see if I can find my notes.....

[rdsmt]

It would be nice if the Modis and Vantage pro had a built in test to do cylinder balance test with an amp probe. I have done it before but a preset test would be nice to reduce setup time.

[jarvissamuel]

The pico version is currently not a live. It collects several engine passes and anaylyzes the data at idle. for the cylinder balance The wavepoint pro is currently only in conjuction with the sia 3000 correct? If so how do you like the scope so far?

Thanks Sam

[mwada]

Hi Sam,

The pico version is currently not a live. It collects several engine passes and anaylyzes the data at idle. for the cylinder balance The wavepoint pro is currently only in conjuction with the sia 3000 correct? If so how do you like the scope so far?

Thanks Sam

Thanks for the confirmation on the PICO version. And yes, you do need the SIA 3000 to run the Wavepoint diagnostics. As for using the scope, I haven't used it much. From the limited use, I see the scope as being a PC version of the MODIS. The interface (software) is almost identical.

I forgot to mention that this test does not check the relative compression of the engine while cranking. This test is done while the engine is running. Yes, I do agree that it would be nice to a relative compression test also.

Miles

[mwada]

Hmmm. as to the "no plug wire" triggering issue, I believe you could trigger off of #1 Coil Primary on a COP system. Haven't had to try it yet so I'm not sure but it does seem possible.

Hello Derek,

Thanks for the reminder. I was aware of doing this while using the MODIS but never really tried it being there wasn't much of a reason to do it. That said, I did try it as you suggested and it did work but with some precautions.

The vehicle is a 96 Volvo with the MIL on and a misfire. The code was for a misfire on number 4 cylinder. The reason for the misfire was a bad coil. Here is an image of the hookup as you suggested.

volvo coil.jpg

Here are the results:

single wire leaning on coil.gif

As you can see the wrong cylinder with the misfire has been identified. In this case no information would have been better then the wrong information. It took me awhile to figure what was happening. At first I felt that the probe was triggering on number 2 cylinder because the probe was lying on it but it looks like it is triggering on number 3 cylinder. More research needs to be done on why this happened. The fix was to move the probe away from number 2 coil. I was also told that it is better to clamp BOTH wires in the probe. This will cancel out the multiple events that are occuring during an ignition event.

Other observations were that if I placed the probe on the coil with the clamp open I could also get the correct trigger.

probe.jpg

Here is the waveform with a proper trigger. I had both wires clamped in the probe and moved the probe away from number 2 coil.

clamped both wires probe away from coil.gif

Thanks again for the reminder,

Miles

[jarvissamuel]

Thanks for the continued effort on this. I am still digging for info on the SIA 3000 and I came accross this under the Sun Diagnostics site

http://www.sun-diagnostics.com/catalog/product_detail.asp?GID=152&PID=127&item_id=3095

I was curious in you use of the usb scope have you seen any screens like those
displayed there? I am curious if has a slightly different software since this on appears to be for the UK or if had these abilities and the screen style like the modis/vp as well.

BTW one time I had a very difficult time finding a misfire on a 5cyl COP Volvo, I found a couple of the coil connector can be switched and appear normal but run very poorly. Don't ask how I know that

Thanks Sam

[DerekRWilliams]

Hi Miles,
Good post, Thanks for testing that method. Looks like that method should be fairly useful if one remembers to take proper precautions to minimize EMI.

- Derek

[mwada]

Thanks for the continued effort on this. I am still digging for info on the SIA 3000 and I came accross this under the Sun Diagnostics site

http://www.sun-diagnostics.com/catalog/product_detail.asp?GID=152&PID=127&item_id=3095

I was curious in you use of the usb scope have you seen any screens like those
displayed there? I am curious if has a slightly different software since this on appears to be for the UK or if had these abilities and the screen style like the modis/vp as well.

Hi Sam,

I wasn't able to view the link you provided but I think I was able to find the site. None of the screens are similar to the version I have. Like I mentioned the screens look almost identical to a MODIS.


SIA3000a.jpg


sia3000.jpg


I am curious, what is the reason for your interest in the SIA 3000? Is it because it is PC based or is it because you don't need a MODIS or both? I personally find it awkward to use the SIA 3000 as a labscope when comparing it to a MODIS.

[jarvissamuel]

Thanks for sharing that. I thought the sia was similar to the modis in scope operation I guess the screen shots from the SUN sight are european package. Much like the modis they list there is grey and has different software coverage.

My interest in the SIA 3000 involves several things.

First let me give you an idea of the current tooling I have. A mt2500 with vci carts, a heritage vantage and two different pc interface scope (parallel port/usb) So the two biggest things I would gain from a modis is another 2 ch and graphing ability.

As I understand it the modis/solus & 2500 given the same software have identical coverage. If that is inaccurate please let me know.

To be able to effectively afford a modis I would have to trade in both my vantage and brick. I am not ready to give up either of these tools. A modis while its convenient that it has everthing built into one unit. However that can be a problem as well. Not very often anymore but sometimes a scope and scanner are required at the same time. As I understand it the modis can run scanner and scope at the same time but it seriously reduces the performance. Another consideration is if it breaks yor are down all 3. My current SO dealer does not have a demo modis but I am sure he could pick one up.

The sia 3000 has 4 channels so I would be gaining an additional 2 ch and it would be a different format then the scopes I currently have. I do not have a problem with how my current scopes operate. It would just be a different option.

The pc connection to many is a burden but I am already used to a pc interface. I may be slower but that is what I am comftortable with. To review data in the primary format additional sofware is required for the modis/VP since this on a pc that is not required. One of the great features of the scopes I have is the ability to share files with other users. There are a lot of modis/ VP users out there now so it would be nice to have the ability to share files. As I understand the modis / VP and SIA have the same file format for labscope movies.

One of the main considerations for the sia is the seccondary igntion. It is able to do raster, superimposed and parade. My current scopes can do parade, and have the ability to show pos/neg DIS and there are work arounds to not having the raster/superimposed. Eventually the software for the scopes I have will probably have raster/superimposed but this is not a priority in the software development at this time.

Another consideration is the ignition probes for distributor igntions are included with the purchase price. The VP is currently on promotion and also includes the leads but I really would like to have 4 ch.

The last consideration is the sia is only tooling that will operate the wavepoint pro misfire software. I may/ may not pick up the wavepoint pro but its nice to have that ability if I want it.

Overall its been frustrating though. I emailed SO directly and a tech rep got in touch with me about the SIA and pretty much was more intersted in having me demo a modis. He did not have demo and pretty much could not get one. I understand the software most likely being tied to the pc and limiting demos compared to hand held stuff but he should be able to least come by and show it in use. It looks like at this point if I want to find out more about I am going to have to just take a leap of faith and buy it. I am just not sure I want to take that leap yet.

Thanks Sam

[MasterWrench]

I was looking at buying a Solus and Vantage Pro, or a Modis. It is about the same price to buy, but I am not sure what the updates cost for the Solus and the Vantage. I have had my Modis for 4 years now and have not had any problems with it yet. The thumb pad might need to be replaced soon, but other than that it has held up pretty good. If it ever does die, I will not be able to afford to replace it, so I keep my fingers crossed .....I don't own a shop, just a tech, so it is a litttle pricey.......

[mwada]

Here are a few more captures.

This is from a 1966 Mustang with a bad head gasket between number 4 and 5 cylinders.

headgasket.jpg

headgasket.gif

Same car after replacing the head gasket.

compression75.gif

Why did this happen? I don't know for sure. I don't know if the major failures hid a minor failure, the failure occured after/during the head gasket replacement or a user error. The compression was at 75 lbs on number 3 cylinder. All the rest of the cylinders measured 145 lbs.

This one if from a 92 Lexus with an intermittent misfire. The misfire only occurs with a certain load condition. I could duplicate the misfire by power braking the engine but the misfire would also occur at times by snapping the throttle while in Park. I wanted to see if it was possible to capture this misfire while just snapping the throttle.

lexus-spark-plug.jpg

Instead of creating an animation (which is kinda difficult with a trimmed image) I decided to combined the 3 events during the misfire.

lexus combined.gif

Another one from a Toyota 4runner with low engine compression, 75 lbs on the bad one, 125 on the rest.

4runner.jpg

Here is the vacuum waveform while cranking.

vacuum.gif

Overall I feel this tool does work and works well. The bonus is the simple and quick hookup. The downside may be in trying to interpret the results. I have many more captures that showed positive accurate results. Yes, many of these didn't need this tool for diagnosis and many needed additional testing to repair the vehicle. I feel using it whether you need to or not is the only way you will know if it will work for you.

[CdanB6]

This shot was taken with a Modis and a low amp probe. Shows low compression on a cylinder. Granted, it does not tell you which cylinder, but if you want a go/no go test, it's fast! Set channel to AC coupled, 40 amps and 2 seconds. Will try to see if it can be sync'd to another signal. Tried the tach pickup, but didn't appear to work. Ford DI multi-strike may have been the issue.