TR6 COMPRESSION READINGS

[RichyBarber]

Hi all. looking for opinion of below compression readings. Went to local rolling road to get my emerald ecu mapped and garage took tests. I have done my own to compare. Thinking i have issues with low readings, valves and or rings etc. Appreciate your advice / comment. Thanks

[RichyBarber]

apols for the multiple upload for the table - not sure how i remove now !

[Waldi]

#5 is lower, the rest falls within 10%. I would first check the valve clearances, but if it is running ok, I would leave it until something else needs doing.

How is your oil consumption?

Waldi

[RichyBarber]

thanks , will look at valve clearances first. Not sure on oil consumption - not gone far yet -!!!  no smoking evident - will dip the oil / check and monitor. Runs ok ish, but still need the ecu / efi mapped properly  

[Mike C]

Slightly low- did you do the tests with all plugs out, WOT?

[RichyBarber]

yes plugs out WOT

[RichyBarber]

valve clearances all good. No apparent loss of oil.

[john.r.davies]

The low difference between wet and dry  in 4 and 5 shows that the low compression is due to a valve seal problem, not piston rings.   Consider regrinding the seats.

John

Edited August 19, 2021 by john.r.davies

[RichyBarber]

Thanks - that may make sense - i did grind them in, but have to say its my first attempt. I have tweaked the map in the ecu, and it seems better - i hve a full session on RR next week to get it mapped - after that i think i will let it settle in and consider re grinding valves over winter. Thanks for help.

[john.r.davies]

A rolling road check is just that, final tweaking and fine adjustment.   And expensive too.   Not worth doing until you have got the engine as right as possible.    With the low compressions it is now far from that!   Correct those first!

Edited August 20, 2021 by john.r.davies

[Mike C]

2 hours ago, john.r.davies said:

A rolling road check is just that, final tweaking and fine adjustment.   And expensive too.   Not worth doing until you have got the engine as right as possible.    With the low compressions it is now far from that!   Correct those first!

I agree. I suspect the garage gave you those results to prevent any comeback later, after you find out you've wasted your money.

[RichyBarber]

I re-did the comp test on 5 and 6 on a cold engine last night and got similar low readings (as the garage) - not sure if it is normal to have such low readings when cold ?   I am actually taking the car to emerald (manufacturers of ECU) to their RR next week (not the original garage) - i am not confident in my set up settings on the ECU with ignition timing, fuel  and map generally and want to take their expert advice on the set up / make sure the ECU is functioning correctly etc. 

[PodOne]

22 hours ago, RichyBarber said:

I re-did the comp test on 5 and 6 on a cold engine last night and got similar low readings (as the garage) - not sure if it is normal to have such low readings when cold ?   I am actually taking the car to emerald (manufacturers of ECU) to their RR next week (not the original garage) - i am not confident in my set up settings on the ECU with ignition timing, fuel  and map generally and want to take their expert advice on the set up / make sure the ECU is functioning correctly etc. 

Having the ECU and MAP adjusted by Emerald is going to be pointless until you have addressed any mechanical issues first. It can't be used as a sticking plaster to fix things and I suspect they may say the same.

Your money, but as other have said save it and investigate the compression issues first.

Andy

[Andy Moltu]

If the pressure improves with a drop of oil it is indicative of a ring issue rather than a valve leak. The oil helps the rings seal but has negligible impact on the valve sealing.

What prompted the compression test? Was the car running right? Using oil?

If the car has stood for a while it may be a gummed up compression ring which may settle with a bit of use..

 

[RichyBarber]

yes car had stood for a while, but i did rebuild the head. in hinesite i should have invested in rings / honed it and spent more time on seating valves. It does run ok ish - have had to tweak the MAP settings to get it somewhere near ok. Have only done about 50 miles, so maybe will settle in. I am kind of set on getting it set up properly with emerald first, run for a few hundred miles and monitor. Failing that, i will pull the head over winter / maybe pull engine if i need to - may have to do this anyway as need to sort my A type OD which is not engaging currently

thanks for all your comments / advice 

[Andy Moltu]

You can hone and re-ring with the engine in situ, although taking the engine out allows easier access and allows you to do more if required.

[trchris]

Now you have compression test data you have identified a slight problem with 5 & 6 cylinders before you attempt anything further I would suggest you do a cylinder leak test this will identify why the figures are low as Andy says above its a bit pointless going to the rolling road session

Chris 

[RichyBarber]

Is there a way of doing a basic leak down without a specify leak test gauge kit. I do have air compressor and basic compression tester (cheap eBay type). 

[harlequin]

An OKish guage are not expensive at £20 to  £30, certainly less then a garage would charge to do the test.

George 

[SpitFireSIX]

Hi,

 DIY spark plug adaptor and inline pressure regulator will do. Plus a pair of ears.
TDC on Compression stroke.

RichyBarber, do you have a single throttle or six PI ones? I guess single as you are using MAP.
If you have a Lambda sensor, the K3/6 has an autotune function for fuelling that is useful when RR is not available.

Cheers,
Iain.

 

[RichyBarber]

I have the original  CP TB’s - tried to keep as much original as possible. Not running MAP - using throttle TPS for load. I have no 02 sensor so the auto tune won’t function.

[JochemsTR]

RichyBarber, you run Alpha-N.....but before you mentioned tweaking MAP ??? Not sure how that fits together. If you do not have an Lambda Sensor, what are you targetting at? This does not make sense. Drifting off subject....

Anyways, spend a few money to do a leak test, before spending lots of money on a RR.

Jochem

PS....please get rid of the straps holding your fuel rail. This should really be a fixed attachment.

[RichyBarber]

I meant tweaking the fuel map and ignition map. At RR , they will use their own  02  sensor. Fair comment on cable ties - will look at this / find a solution. - have doubled up ties since the picture. 

[DRD]

2 hours ago, RichyBarber said:

I meant tweaking the fuel map and ignition map. At RR , they will use their own  02  sensor. Fair comment on cable ties - will look at this / find a solution. - have doubled up ties since the picture. 

Surely to get the full benefit of EFI you should have a closed loop system, then you wouldn't need to worry about a RR unless you wanted to fine tune the MAP.

[RichyBarber]

agree on open loop to extent, but from past experience on my lotus 7 with an omex system, the wideband 02 was tempermental / not as good as a proper RR set up. the omex RR guy told me the O2 was not needed once set up. . There is a lot to set up and get right / check in the emerald settings, and i am not 100% confident without going to them .