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| Normal compression test results, and base timing??? http://www.4g61t.org/forum/viewtopic.php?f=6&t=34491 |
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| Author: | Redline89 [ Fri Apr 01, 2011 10:43 am ] |
| Post subject: | Normal compression test results, and base timing??? |
What are people getting for compression tests out of their 4g61, 4g61t? Its normal on 2.0l to see 140-160 I think right? What is base timing supposed to be at on these too. Need to check today. |
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| Author: | CaptainTonus [ Fri Apr 01, 2011 10:52 am ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Factory fresh compression on a 1st-Gen 4g63 is ~165psi The factory service "limit" on a 1st-Gen 4g63 is ~120psi If you're in between there, you're pretty much in good shape. I think the 4g61t is rated at 8:1 compression stock, and a 4g63 is 7.8:1, so they should be pretty similar. |
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| Author: | Redline89 [ Fri Apr 01, 2011 11:18 am ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Ive got 110, 110, 115, and 120 psi. with HKS 272 cams. and n/a pistons... do they have specs for the 4g61? |
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| Author: | CaptainTonus [ Fri Apr 01, 2011 11:28 am ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Quote: Ive got 110, 110, 115, and 120 psi. with HKS 272 cams. and n/a pistons...
I'm sure they do, but I don't know what the specs are. I remember back when dragstr4g61t owned that car he posted about the compression being really low like that, but the car still hauled ass so whatever. I'm not sure if the engine has been changed since then though. The N/A pistons should give it a good bump in compression though, I think they are 9:1 instead of 8:1. The cams might have an effect on the compression numbers. Also, make sure you do the test on a hot motor if you can, and hold the throttle wide-open while cranking it over, usually helps. There isn't a lot of variance between the cylinders, so that's a good thing. When in doubt, do a leakdown test!
do they have specs for the 4g61? |
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| Author: | Redline89 [ Fri Apr 01, 2011 11:59 am ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
NO!! I am scared to do the leakdown test.... I was scared all last season to do one... HemiColt is always making fun of me for it  I didnt think about doing it with the throttle wide open... I might do it again. Yeah bobby got 100-105psi on the old setup. Ive rebuilt this engine twice now, once due to need and once to put the na pistons in her. Ive reused the bearings and rings just like my good homie Dragstr4g61;) |
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| Author: | CaptainTonus [ Fri Apr 01, 2011 12:52 pm ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Quote: NO!! I am scared to do the leakdown test.... I was scared all last season to do one... HemiColt is always making fun of me for it
I'm sure it'll go up if you do it at WOT. Give it a shot. If the thing still runs hard, doesn't smoke too much, doesn't go through fluids, then fruit and banana it, keep running it!
I didnt think about doing it with the throttle wide open... I might do it again. Yeah bobby got 100-105psi on the old setup. Ive rebuilt this engine twice now, once due to need and once to put the na pistons in her. Ive reused the bearings and rings just like my good homie Dragstr4g61;) |
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| Author: | CSM Shaun [ Fri Apr 01, 2011 2:18 pm ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
 Tony would never lie to us. |
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| Author: | Flying Eagle [ Fri Apr 01, 2011 2:39 pm ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Remember that these numbers are all skewed because of the longer duration cams, and possibly from starter speeds as well because of smaller race batteries that some people use. Leakdown test will give a more accurate determination of sealing capability and wear characteristics. |
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| Author: | CaptainTonus [ Fri Apr 01, 2011 2:39 pm ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Quote: Tony would never lie to us.
Not intentionally! 
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| Author: | Redline89 [ Fri Apr 01, 2011 4:37 pm ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Thanks for that! That is awesome to know for sure now;) Yeah with my cams im sure it dropped down pretty good.... My spool and overall boost has signifigantly suffered and I am hoping my timing may have gone way out. Gonna check that later today or tomorrow. |
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| Author: | boostfreak [ Tue Apr 12, 2011 11:21 am ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Got 105-120 cold on my 61t yesterday. Also, when you went 10.9 and 10.6, was that on 61t or NA pistons? |
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| Author: | Redline89 [ Wed Apr 13, 2011 9:34 pm ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
that was on the stock turbo pistons. I havent had a good pull with the na pistons. This season should have no problem |
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| Author: | Mechacode [ Sun Apr 17, 2011 11:38 am ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
Hot motor, WOT, cams will take some out of it, around 10ish psi. |
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| Author: | 93'TSIColt [ Thu Apr 21, 2011 2:05 am ] |
| Post subject: | Re: Normal compression test results, and base timing??? |
unfortunatly different compression testers read differently. I have had three different testers (snap on,performance tools (china) and a walmart brand one (china)... each one read differently (on the same car)... one read around 150 psi, one read 120 psi and the other around 95psi... so u cant really measure ur compression.. and base if ur engine is good or not by compression test results... its more to check if there is indeed compression on each cylinder and that they are fairly even, As Flying Eagle stated... a leakdown tester will give you more acurate results on the shape of your engines internal sealing surfaces |
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