Calculating VW EA827 16v Compression. OEM vs Skimmed head vs Turbo examples 09-01-12

Background

In recent years myself and others have understood the 16v EA827 heads as being capable of holding 45cc in the combustion chamber. This 45cc measurement was based on what was read and used, by default for online compression calculators.

Almost on a year ago Danny challenged this:

vw_singh measured the combustion chamber of heads:

With the variation of information seen, I thought it would be useful to perform my own measurements to calculate the compression chamber volume in some 051 103 373 and 051 103 373 D heads. I have also then measured key dimensions in the engine block and put these measurements in a calculator to determine the compression ratio.

I hope this is useful and adds to the breadth of data and information which Club GTI is renowned for.


Tools.

• 100ml Burette
• 110x100mm Plexi glass to seal the titration on cylinder head and block
• 150mm Vernier
  
  
• 54 - 90mm Bore Gauge
  
  
• Toyotec compression spreadsheet.

Method.

The Burette is used a lot in chemistry for adding chemicals in the correct dosage to make a well balanced titration. It is important that the meniscus line is read correctly from the "zero" mark to the finish point when the fluid column has been dispensed.



More about how to recognise and read the meniscus line here.


Cylinder heads

Two std heads heads were tested both 051 103 373 found on European engines as such as the KR 9A and 6A codes and the 051 103 373 D fund on ABF, post 94 9As, ACE and ADL engines.

Both types heads were stripped and cleaned of carbon deposits.

The valves seats were greased to form a seal.




The fire-ring landing on the cylinder head was smeared with grease to form a seal for the plexi glass.




The spark plug as also refitted.

The burette was used to fill this space until there were no bubbles and the volume recorded. This was repeated on the other cylinders




Short Engine

The short engine used is an ABF engine.
To prep the pistons edges were smeared with light grease to form a seal.




The pistons were then moved down the bore and this distance recorded.




The deck above the pistons was smeared with light grease to form a seal to the Plexi glass.



The burette was used to fill the space until there were no bubbles and the volume was recorded.




This measurement was used to calculate the piston dish/dome by calculating the theoretic volume of bore size and this depth then adding (or subtracting) the measure volume from the burette.

The bore was also measured both by bore gauge and vernier and found to be 82.5mm.
The MLS head gasket bore was measured as 83.5mm


Results from Heads

Head type code	Cyl 1cc	Cyl 2 cc	Cyl 3cc	Cyl 4cc
51103373	47.5	47.4	47.6	47.5
051103373D	47.4	47.6	47.5	47.5

Piston cc (Dish +ve) (Dome -ve)

Chosen distance piston travelled down bore = 10.5mm
Theoretic CC = 56.12897062
Measured CC = 57.8
Piston dome/dish cc = -1.671029379


Calcualtion of ABF engine CR via Excel tool

Yellow = Entered data
Green = Calculated data
Red = CR result




Using the calculator, it should be noted that cylinders with 47.4cc the CR = 10.51529406
47.6cc the CR = 10.47893055
This still means the average CR of the engine would be 10.5:1


Calculation of ABF Turbo (WOLF R) with *stacked gaskets via Excel tool
*Assuming nominal 47.5cc camber volume.




Findings

• Based soley on the information from this exercise, KR and ABF 051 heads shown here have combustion chamber volumes of ~ 47.5cc.
• This being the case, as the CC is the same between heads fitted, one in favour of the other will not lead to an increase in CR when fitted to any EA827 16v.
• The information here matches the factory published measurements for CR, on an ABF engine as 10.5:1.

Comments welcome

Regards
Toyotecwerke.

 

The ACE factory published CR is 10.8:1, why and where is the difference as it uses same casting head 373D with same valves as ABF? Head gasket is same too.

 

Maybe there is more piston protrusion on an ACE?

Nice report Eddie. From memory the KR head gasket squishes more than the metal ABF one so would that point to the difference in the CC's that I calculated ages ago?

Gurds

 

Another great thread, clears up any theories about one head giving a higher compression than another

 

Good work Eddie.

You need to source an early KR 027 head casting and check that for full picture. The 027 is slightly smaller in diameter around the perimeter of the combustion chamber and may show a difference in volume.
It was an 027 type head I had previously CC checked to get the 45cc.
Production casting variations and of course any previous head skimming would also need to be considered.
I have heard of variations in production block heights which would also contribute to slight differences in CR.
If using standard components to build an engine then it is pretty safe that the CR is not going to vary to the point of it being too high.
But when fitting aftermarket pistons that are raising the CR substantially, then this is where it is imperative that accurate measurements are taken. 1cc at 10:1 does not have the same effect as 1cc at 13:1.

 

It is certainly worth exploring and I have one of those as well + MLS gasket (G60). Just need to take it off the engine.

The cylinder heads I have are STD items. I knew the vehicles they were removed from.
I do have a 051 KR unit from vw_singh that is skimmed to the limit line that I plan to measure in my own time.

It would be interesting to know the source of that information re production block heights.

If you fit after-market pistons and use the measurement procedure for the measured and the theoretical volume above the piston, moved a measured distance down the bore, you can work out what CR would be achieved with certain head CC, once you know the squashed gasket thickness.

Regarding 1cc difference yes you are right.
Take the combustion chamber.
A +/- delta of 1cc from the measurement I gave, in the ABF/KR cylinder head examples would give, on an ABF engine:

Nominal ccl|Delta +/-cc|New volume cc|CR*:1 47.5|+1|48.5|10.32:1 47.5|-1|46.5|10.68:1I would become nervous though if an OEM with automated CNC machines would manufactor cylinder heads with that level of variation though.

 

As per vw_singh's suggestion on different piston shape.

Worth checking too.

 

Great thread and the findings match the published figure but are still surprising the both heads are the same, nice to know, looking forward to finding out about the skimmed head.

 

Testing the modified/skimmed head 09-01-12

Well this request has been completed, well kind of.

The head in question had been skimmed to what appears to be a limit line.
There was noticeable work done in the combustion area where material was removed to fully unshourd the valves.
On other matters the valve throats had some work on both inlet an exhaust paths as well as some radius blending.

Unfortunately I only measured 2 combustion chambers as the other 2 suffered cracking between valve seats.

Results received from Burrett measurements are summarised below.

Head type code	Cyl 1cc	Cyl 2 cc	Cyl 3cc	Cyl 4cc
51103373 Skimmed	47	N/A	46.8	N/A

When the result for the head cc @ 46.8 is input into the calulator the CR for an ABF engine on STD pistons results in 10.64:1 and 47cc results in 10.6:1.

 

Bringing this back from the dead!

Can someone explain the relationship between the CR and engine characteristic difference I'd experience? I have an ABF head ready to go and I'm wondering if it is worth getting more skimmed off than just enough to flatten back to tolerance? For instance would a 10 thou skim over standard really give me much gain in performance?

ABF 051103373D head with a 9a block.

 

Hi great thread how were the piston to deck volume results calculated if you don't mind me asking? Thanks in advance

 

great info. thanks. I am looking at building a 16vg60 motor for my edition1 b35i replica car. I want to also build the motor in such way that I can turbo it after when the g-ladder parts ways with the shaft or seals...

 

hi , can you please tell me how is calculated the SC= side clearance cc ?