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High spec EJ257 misfire, cam correlation, cranking compression difference between two banks


Rozsko
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A conventional tester would have said everything is just dandy as it only shows the maximum pressure.

The car ran on 3 when i got it in (still does as im afraid this car has now done its work).

This car was somewhat obvious as it had a kind of a puffing noise. Like you could hear the compression escape somewhere. What i did first was to disconnect the PCV tube between the intake and the valvecover and held a piece of paper in front of the intake port. That made it obvious that there was compression escaping into the intake. So yes a sensor in the intake would tell you there was pulses that wasnt supposed to be there. But was it because of a leaking intakevalve maybe? Took out the glowplug on nr 1 and tested with the WPS and i could tell what really was happening right away.

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  • 3 months later...

Hey guys,

Now that my Italy assignment has officially came to an end, I finally had the chance to pull the engine.

Here are the valve lash values: (in mm)

  • Cyl#1
    • Int
      • Front 0.14
      • Rear 0.15
    • Ex
      • Front 0.31
      • Rear 0.32
  • Cyl#2
    • Int
      • Front 0.21
      • Rear 0.16
    • Ex
      • Front 0.31
      • Rear 0.31
  • Cyl#3
    • Int
      • Front 0.15
      • Rear 0.17
    • Ex
      • Front 0.34
      • Rear 0.37
  • Cyl#4
    • Int
      • Front 0.15
      • Rear 0.16
    • Ex
      • Front 0.36
      • Rear 0.37

The Cosworth specs are the following:

  • Int 0.008" = 0.2032mm
  • Ex 0.01"= 0.254mm

I am not sure tbh. Some of the exhaust are more then 0.1mm out and the intakes are also out almost 0.05mm. Do you think this qualifies for replacing the buckets?

Also and other question, do you know if the Cosworth (or I guess any aftermarket) cam specs are for fully advanced or fully retarted state of the cams? I did some cam degreeing and the intakes are so much off of the Cosworth specs that I suspect those are for fully advanced state.

Thanks

Intake valve 1mm open.jpg

Intake valve 1mm close.jpg

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A lot of those are definitely too tight, and they will close up when the engine is warm. I'd like to see 0.25mm on the inlets and 0.35mm on the exhausts. Err on the side of caution on the high side, simply because the 01+ heads do seem to wear valves and seats over time, and with hard use, the gaps can only decrease. A little extra does no harm at all.

It's fairly common to grind a little off the top of the valve to gain a little clearance...with suitable tooling. A little bench belt sander setup correctly works well and makes it easy to ensure a flat and true top of the valve.

 

Or yes, buy new buckets.

 

IMO the cams at rest would be in a retarded state ? as the VVT can only advance them, but default position would be 0, ie retarded ?

Never actually dialled in a custom cam VVT setup, only ever done regular camshafts. Although it would seem pointless them giving timing data that cannot be achieved as you cannot operate the VVT ?

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16 hours ago, Stevieturbo said:

MO the cams at rest would be in a retarded state ? as the VVT can only advance them, but default position would be 0, ie retarded ?

Never actually dialled in a custom cam VVT setup, only ever done regular camshafts. Although it would seem pointless them giving timing data that cannot be achieved as you cannot operate the VVT ?

Yes, the rest position is the most retarded position, but physically looking at the inside of the AVCS cam gears the most advanced position would be way over advanced compared to the cam spec sheet as the roughly 25 cam degree can be achived with the AVCS which results in double crank angle.

So these spec sheets seem to me useless for AVCS gears. With that, All I will want to correct is the difference between the two sides and since the left side was higher in compression the the right, I will target adjust the right side.

First I will obviously need to sort out the valve lashes.

And as always, thanks for the reply.

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20 hours ago, Stevieturbo said:

Although are you saying you have adjustable AVCS cam wheels in order to actually do anything with the cam timing ? Never heard of that.

Otherwise....not really a lot can be changed from how it's ground ?

 

Have you contacted the cam supplier with your query ?

No, I don't have adjustable AVCS gears. I don't think something like that exists. What I have recently bought is a set of eccentric idler pullies which should be able to help me to adjust the tension in the belt such a way that I can eliminate the timing difference between the two sides.

Yes, I have sent a message to Cosworth, but they did not reply yet and I think I don't think they will.

2 hours ago, Steve said:

Great to see you back at it bud.

Im sure you know, and its im pretty certain its in the camspecs, but its common for a cam to be spec`d at 0.050" valve lift IIRC (its been a while). Just putting it out there just in case...

Thanks. yes, the specs mention the valve lift in both metric and imperial, that is how I took the crank degree measurements above.

FYI, I attach the camspecs.

Cosworth cam specs - 20191013_231520.jpg

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Looking at those specs those are all normal "fully home" numbers.  Since your opening/closing events dont match the spec sheet then it would be best to work off lobe centres.  To find the lobe centre just mark the protractor when the valve is about 0.010" before full lift, then again 0.010" after full lift and your lobe centre is half way between those two points.  The 107 on the intake is degrees ATDC and the 113 on exhaust is BTDC

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True, always set using either max lift as per lobe centerline, or lift at 1mm ( or whatever reference is given ).

 

Both should tally up as correct though. I would not be using an actual open from closed, or open to closed position for timing it in.

 

Also ensure you're on the correct lobe too, as Kelford cams actually have the two lobes slightly different opening/closing ramps which is a little odd.

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  • 4 weeks later...

Hey Everyone,

Just thought to give you some update here.

The engine is back together and the car is up and running again. as you can see on the pictures, the relative compression test is very nice and the measured compression in two opposite cylinders (#2, #3) are 9.2 bars which is not bad from a cold engine I think.

As for the misfires, I am not sure yet as I am struggling to grab a good handle on the changes in the map, so as I work through those I will keep you posted and I am planning to do some tailpipe pressure/vacuum tests as well with the Pico.

Old relative compression:

531180664_2019-11-10114945Relativecompressiontest-sync4.thumb.jpg.db72104441ddb5b40c46a936001de5f6.jpg

New Relative compression:

1836676056_2020-04-29114945Relativecompressiontest-sync1-ACcoupling-1Vrange.thumb.jpg.369c020d69a44ff2f0b1a7bdcd857bfc.jpg

#3 cyl compression:

1548477714_2020-04-292350483compressiontest-relativecompressiontest-sync1.thumb.jpg.e788e4defe341bc8549ff0fa0ac2dded.jpg

#2 cyl compression:

1307125113_2020-04-292350482compressiontest-relativecompressiontest-sync1.thumb.jpg.37901601b8202802e402f1b4585ddbac.jpg

It's interesting see how much the volume of the flexi hose to the WPS effects the relative compression. you can clearly see that from the above two pictures.

This is how I ended up timing the valves:

20200424_133112_resize.thumb.jpg.e02a97c7874348f110313abb0cfe6816.jpg20200424_133151_resize.thumb.jpg.5f394c7ffdb38661192a7315932792a2.jpg

20200424_173953_resize.thumb.jpg.f2694cb882531fdf9ab05483aebc3467.jpg20200424_174030_resize.thumb.jpg.d1b2747b366e97be97e5a5a86bf9e398.jpg

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Now there`s a difference!

I find myself checking in on this post several times a week to see what it all ends up with. So i for one appreciate your updates :)

So your cams are now locked in a fixed position all the time if i get you right?

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41 minutes ago, Steve said:

So your cams are now locked in a fixed position all the time if i get you right?

Nope. The intake is still variable and these values are the most retarded rest position values.

The exhaust is of course fixed as it is single avcs only.

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16 hours ago, Stevieturbo said:

Not sure I'm following the cam timing.....you do not, cannot adjust based on a valve opening and closing point ?

 

And with the AVCS pulleys...they are not adjsutable anyway ?

 

As Steve says, I literally did only pop back in here myself to check this thread lol

All I am saying, is that I am still using the AVCS gears on the intake, but the most retarded (or resting) postion of the intake gears are degreed what you can see on the pics before.

The way they are adjusted is through the LIC eccentric idler pullies (see picture below). With these you can advance/retard the intake gears a couple of degrees.

On the exhaust side, as you can see on the picture I am using adjustable cam gears, so those are straight forward.

20200425_020442_resize.jpg

20200425_021243_resize.jpg

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I am playing with the map changes right now. Went through quite a few changes yet and I think I am getting close to get a good stable idle and relatively close VE table in the cruise area.

Here are two videos I shot just a couple of days ago. Can you guys check them out and let me know what you think?

with silencer: https://1drv.ms/v/s!Ale4oyMCOgLThMczCcYOeg5Gg7Do5A

without silencer: https://1drv.ms/v/s!Ale4oyMCOgLThMc0M8Zap8qNO7Wzzg

With the silencer I can hear quite a bit of misfire. At least that is what I thought I hear, but recently I removed the silencer and without it is far not that obvious. So I am thinking about is that really a misfire or that is only a side-effect of the silencer???

I still want to do a tailpipe pressure/vacuum test with the Pico, but first I wanted to get the basics done on the map.

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Just browsed throught your thread..

Did you sort the valve clearance out ?

Also .. since this seems cam related.. I am sure you've checked the buckets for abnormal wear... but have a read anyways.. 

Cossie cams could come from the same casting plant..

https://forums.nasioc.com/forums/showthread.php?t=2642831

 

I had a set of GSC cams with minor scoring on the buckets.

Also did you do the cam break in procedure ?

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On 5/13/2020 at 6:55 PM, remski2 said:

Did you sort the valve clearance out ?

Yes. All set to Cosworth Specs.

On 5/13/2020 at 6:55 PM, remski2 said:

Also did you do the cam break in procedure ?

Not really as at the time of initial install I did not pay attention to the last sentence on the Cosworth spec sheet, and my mechanic didn't mention that either.

 

On 5/16/2020 at 10:06 PM, Stevieturbo said:

Nothing wrong with that ?

Sorry Stevie, I am not sure what you mean.

 

On a side note, I think I got the map on the G4+ to a state that is pretty good in idle and cruise, but just two days ago I sold it and now I am waiting on the G4X to be delivered. I am very exited about that.

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  • 1 month later...

Just thought to give you guys a quick update.

Just came back from the third dyno session. It started out nice, but ended up bad as it seems the turbo is gone.

if you are interested, on the link you can see some dyno chart screenshots, the log of the pull and a video as well.

So now I'll need to get the turbo out and see what is exactly the fault. More to come...

https://1drv.ms/u/s!Ale4oyMCOgLThMsJ_3rw80Z6DRXUTw?e=5WToXO

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