ryan22laird Posted October 19, 2014 Share Posted October 19, 2014 Hi lads can anyone help got a fresh rebuild on my forged engine two month ago was ran in proper at a 1000 miles with no boost till around 750 miles all oil and filter was changed as it should did a compression test yesterday and it was reading bang on 70 psi over all 4 cylinders a thought maybe it was the compression tester that was broke so a went and got a new one still the same result 70 psi it's wiesco 74.5mm low compression pistons surely if the engine was down on compression it wouldn't be reading the same over all 4 cylinders the car starts and drives spot on doesn't burn oil or smoke on boost can anyone help thanks Ryan Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 Thats fucked dude unfortunately.low comp good health forged should be 150-155psi over all four.70s not good. Are you doing this on a warm engine and throttle wide open also ???? Quote Link to post Share on other sites
ryan22laird Posted October 19, 2014 Author Share Posted October 19, 2014 Thats fucked dude unfortunately.low comp good health forged should be 150-155psi over all four.70s not good. Are you doing this on a warm engine and throttle wide open also ???? aw your kidding man its weirdo how all 4 cylinders are the same tho engine was cold when a did it and full throttle Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 Needs to be warm dude,with full throttle and duration of 5secs on the key Quote Link to post Share on other sites
ryan22laird Posted October 19, 2014 Author Share Posted October 19, 2014 OK will a heat the car up for 10min then do a compression test ? Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 Needs to be at full operating temps dude.needs a normal drive for 10mins Quote Link to post Share on other sites
ryan22laird Posted October 19, 2014 Author Share Posted October 19, 2014 OK dude will update soon with the result Quote Link to post Share on other sites
ryan22laird Posted October 19, 2014 Author Share Posted October 19, 2014 Just did a compression test again it wasn't reading 70 psi made a mistake it's sitting at 110 psi over all 4 cylinders that's with a hot engine Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 Thats with a 5sec key burst and wide open throttle ??If so your engines got an issue dude.as I said above shouldnt be any lower than 150 and plus the fact you said you have tried two different testersnot good news :-( Quote Link to post Share on other sites
_shaun_ Posted October 19, 2014 Share Posted October 19, 2014 Engine will be fine. If there ballenced across all 4 just double check its all timed up properly. Did u look into what comp rate you wanted the car to be when you selected you headgasket and pistons Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 Lol shaun 110psi isnt "fine" no matter how close they are balanced.The lowest it will be compression wise is maybe 145 psi. Quote Link to post Share on other sites
_shaun_ Posted October 19, 2014 Share Posted October 19, 2014 (edited) Lol shaun 110psi isnt "fine" no matter how close they are balanced.The lowest it will be compression wise is maybe 145 psi.whats that based on?its impressive to guess the lowest compression it can be with out knowing anything other than low comp pistons? changed loads of variable in the engine. for example mine came up at 125psi across all 4 cylinders and has atleast 15k miles on it now running constantly above 280bhp and pretty much abused anytime it gets taken out. i certainly wouldn't use your technical terminology of "fucked" to describe my engine. the engine itself could be perfectly fine but hes made a bad choice in headgasket size for what he wants if so its a case 2hours to switch the headgasket and hes good to go again. Edited October 19, 2014 by _shaun_ Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 Lol okies shaun.dude do you have any oil residue coming out of your breathers/catch tank at all ? Quote Link to post Share on other sites
_shaun_ Posted October 19, 2014 Share Posted October 19, 2014 Lol okies shaun.dude do you have any oil residue coming out of your breathers/catch tank at all ?no really elaborate on how you decided that figure am interested on what mathematical equation you used to decided 145psi is the exact figure at which is goes from fine to fucked?. i could be wrong but am just going by the word of my mapper who when tested it said it was quite low but its running perfectly healthy and making good power so its fine to map. now i no he may be wrong but as hes known to be one of the best mappers in scotland and maps alot of time attack cars and such like id be surprised if he was was making such a school boy error of not guessing what compression figures cars should be with out asking any actual specs Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 Lol shaun.Dude I just noticed in ure engine bay u have still a pcv connected up.do youself a favour and remove the WHOLE pcv unit and replace with an elbow to allow for better breathing.also as I just said about checking breather setup which in your case is a lil mini air filter in red.check the inside of that for being drenched with oil. Quote Link to post Share on other sites
_shaun_ Posted October 19, 2014 Share Posted October 19, 2014 Lol shaun. is that the formula you used? or do you just plan to reply "lol" when you dont want to answer? i could actually learn a useful piece of information here its seems rude for you to keep it to yourself. Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 ;-) Quote Link to post Share on other sites
5e colin Posted October 19, 2014 Share Posted October 19, 2014 to the op thats still to low for my liking when engine was put back together did they do the valveseats and the likes they might not be sealing right ???? also the cogs are they aligned to the right dots ??? Quote Link to post Share on other sites
ryan22laird Posted October 19, 2014 Author Share Posted October 19, 2014 Sorry about the late replie just went to my mate unit there and he's got a forged ep82 with the same rods & pistons as mine did a compression test and his is reading 122 psi over all 4 cylinders double checked mine and still the same as before 110 psi over all 4 cylinders if a can mind correctly am sure the the boy that built my engine used a 1.4 mm Antena headgasket does this lower the compression even more ? Quote Link to post Share on other sites
5e colin Posted October 19, 2014 Share Posted October 19, 2014 yes it will lower it ours stock compresses to 1mm get a leakdown test done to be safe Quote Link to post Share on other sites
ryan22laird Posted October 19, 2014 Author Share Posted October 19, 2014 Will phone the boy tomorrow who built it and find out what head gasket he used the car pulls well like doesn't smoke on boost or lost any power Quote Link to post Share on other sites
AdamB Posted October 19, 2014 Share Posted October 19, 2014 Mikey is right no matter which way you look at it, would you class an engine in perfect working order if it had 10 psi across all 4 cylinders? There's a threshold where there is a problem with the engine during a compression test. I'm not saying your mapper/engine builder is wrong Shaun, however it has been stated time and time again that anything below 135psi will require a rebuild or further inspection. I wouldn't expect to see a forged enigne run that low even if the compression ratio has been reduced because it should be a nice tight new engines where the sealing is good, remember that even 20 year old engines are still able to manage to pull 150psi on the odd "good" engine you can find. Get a leak down test carried out as that's a much more accurate way of telling why the cylinder pressures are down Quote Link to post Share on other sites
mikey4410 Posted October 19, 2014 Share Posted October 19, 2014 I have heard the majority of "low compression" forged engines run circa 145-150 psi.read a thread on that ages ago and alot of people inputted to that thread.mines a stock 17 year old engine with well over 165psi over all four cylinders.I do see whats meant about a thicker gasket as well as low comp pistons and thats when you see the 145-150 psi im sure Quote Link to post Share on other sites
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