jonD6B 0 Posted February 11, 2006 Have just had a glance of the report I got back from the guy who tuned my 1.9 8V 205 and amongst the readings it has one entitled 'Cylinder condition'. It basically says:- "Speed drop for cyl. from base speed of" and then gives the individual cylinder readings, which are: Cyl. 1 - 1371 rpm=+ 313 rpm Cyl. 2 - 1373 rpm=+ 310 rpm Cyl. 3 - 1448 rpm=+ 315 rpm Cyl. 4 - 1754 rpm=+ 313 rpm Has anyone got any idea what these mean and can they be used to determine whether the bottom end is in reasonable condition or not? The car has done 135K. Cheers. Share this post Link to post Share on other sites
DrSeuss 0 Posted February 11, 2006 On merc sprinters you can monitor idle speed to give you a rough estimation of compression. Imagine trying to compress a cylinder with no compression then one with loads of compression. The amount of force required to do so would vary. This speed reflects in the speed of the crank during that cylinders compression stroke. Its not very accurate and i'm not sure how to use the figures you've posted. But it is a valid way of estimating engine condition. Share this post Link to post Share on other sites
Rippthrough 98 Posted February 11, 2006 Have just had a glance of the report I got back from the guy who tuned my 1.9 8V 205 and amongst the readings it has one entitled 'Cylinder condition'. It basically says:- "Speed drop for cyl. from base speed of" and then gives the individual cylinder readings, which are: Cyl. 1 - 1371 rpm=+ 313 rpm Cyl. 2 - 1373 rpm=+ 310 rpm Cyl. 3 - 1448 rpm=+ 315 rpm Cyl. 4 - 1754 rpm=+ 313 rpm Has anyone got any idea what these mean and can they be used to determine whether the bottom end is in reasonable condition or not? The car has done 135K. Cheers. It's where they turn off the ingnition to one cylinder and measure the drop in engine speed, as long as the drops are similar, the dynamic compression *should* be the same. Share this post Link to post Share on other sites
Paintguy 0 Posted February 11, 2006 As said, it's a quick 'rule of thumb' type check, and if the readings are roughly the same, it tells you that each cylinder is contributing in equal amounts. Of course, it could just mean they're all equally bad Share this post Link to post Share on other sites
PumaRacing 1 Posted February 12, 2006 On merc sprinters you can monitor idle speed to give you a rough estimation of compression. Imagine trying to compress a cylinder with no compression then one with loads of compression. The amount of force required to do so would vary. This speed reflects in the speed of the crank during that cylinders compression stroke. Its not very accurate and i'm not sure how to use the figures you've posted. But it is a valid way of estimating engine condition. No it isn't and that's not why it's used. It's a rough and ready test of the ignition, fueling systems and cylinder specific internal faults - NOT the overall engine condition. No matter how worn an engine is if all cylinders are evenly worn then all will contribute the same amount of effort at idle speed (or any other speed). Isolating each cylinder in turn will give the same drop in rpm whether the engine is brand new or completely clapped out. However if a cylinder has a bad plug, HT lead, blocked injector, bent valve etc then it won't be contributing the same effort as the other three and the rpm drop when that cylinder is isolated will be lower. However it tells you nothing about compression, dynamic compression or anything else. It just tells you that cylinder isn't running right. You then find the problem by further testing in specific areas. Unfortunately (unless it's just a typo by the OP) the person who conducted this test did them at different base speeds so the results are meaningless. It actually looks like cylinder 4 has a lower drop in percentage terms than the other three but the base speed has been raised to make that drop look the same. It may well therefore be that cylinder 4 has a problem. Share this post Link to post Share on other sites
jonD6B 0 Posted February 12, 2006 [unfortunately (unless it's just a typo by the OP) the person who conducted this test did them at different base speeds so the results are meaningless. It actually looks like cylinder 4 has a lower drop in percentage terms than the other three but the base speed has been raised to make that drop look the same. It may well therefore be that cylinder 4 has a problem.] Given what you have said a compression test is needed for more of an indication to the blocks condition then. What other tests can be done to determine the overall condition of the bottom end though as I'm probably going to go down the 8V route in my search for more power on the track and was hoping to concentate on head work only if I could get away with it. Share this post Link to post Share on other sites
