Is 60 lbs comp enough?
08-02-11, 10:35 PM
#1
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Is 60 lbs comp enough?
I've spent months trying to get my gxl/t2 swap running correctly. I checked the compression on the #1 rotor and all I can get is 3 bounces at about 60psi. I didn't even check the #2 rotor.
Is this enough compression, should I be able to get this engine running correctly or should I just pull the engine and start gathering rebuild parts.
ashley
Is this enough compression, should I be able to get this engine running correctly or should I just pull the engine and start gathering rebuild parts.
ashley
08-03-11, 01:50 PM
#3
It seems strange that all 3 would be 60 lbs. instead of only 2 of them though. Maybe it's the crud of oldness. If it's not too much trouble to get the motor running you might want to let it run for a bit, maybe premix some 2-stroke oil, let it wear and seat a bit and hope the numbers go up. If you're really lucky. If it's not too hard to try then it's worth a shot.
It would also help if you knew how the motor was running before, if it was running recently (hopefully yes), if it's a lousy JSPEC, etc.
It would also help if you knew how the motor was running before, if it was running recently (hopefully yes), if it's a lousy JSPEC, etc.
08-03-11, 03:23 PM
#4
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The 60 psi might not be too bad if you go by the rotaryressurection.com method and I would think he would know what he is talking about. See step #8. The next thing to try would be step #9 and see what the overall compression is.
Compression test using a piston engine tester :
1) note battery strength. A weak battery will yield low compression results.
2) Remove both lower plugs and wires.
3) remove EGI fuse from engine fusebox.
4) have a friend floor the accelerator pedal, opening the throttle for more airflow
5) insert your tester into the leading hole
6) hold the valve on the side of the tester open
7) have your friend crank the car over for 5+ seconds.
8) observe the needle bounces. You should see 3 in succession without skips, even bounces, in roughly the 30-35psi range.
9) let out on the valve now, and let the tester reach an overall compression value for all 3 faces(highest of 3 will be displayed). 115+ is like new, 100-115 is healthy, 90-100 is getting weak(1 year or less in most cases) below 90 could blow at any moment.
10) repeat for opposite rotor. Note difference in overall compression between rotors, which should be no more than 20psi max.
Compression test using a piston engine tester :
1) note battery strength. A weak battery will yield low compression results.
2) Remove both lower plugs and wires.
3) remove EGI fuse from engine fusebox.
4) have a friend floor the accelerator pedal, opening the throttle for more airflow
5) insert your tester into the leading hole
6) hold the valve on the side of the tester open
7) have your friend crank the car over for 5+ seconds.
8) observe the needle bounces. You should see 3 in succession without skips, even bounces, in roughly the 30-35psi range.
9) let out on the valve now, and let the tester reach an overall compression value for all 3 faces(highest of 3 will be displayed). 115+ is like new, 100-115 is healthy, 90-100 is getting weak(1 year or less in most cases) below 90 could blow at any moment.
10) repeat for opposite rotor. Note difference in overall compression between rotors, which should be no more than 20psi max.
08-03-11, 05:07 PM
#5
The rotary resurrection method makes no mention of removing the schraeder valve from the tester. I can only assume that's the reason it tells you that 30-35 psi per bump is ok. If you leave the schraeder valve in, the numbers become fairly meaningless, as the springs are not created equal. A strong enough spring won't even allow the needle to move at all.
You really have to remove the valve and hold the bleeder open to get any meaningful numbers. 100+ psi per pulse is preferred.
You really have to remove the valve and hold the bleeder open to get any meaningful numbers. 100+ psi per pulse is preferred.
08-03-11, 06:03 PM
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The rotary resurrection method makes no mention of removing the schraeder valve from the tester. I can only assume that's the reason it tells you that 30-35 psi per bump is ok. If you leave the schraeder valve in, the numbers become fairly meaningless, as the springs are not created equal. A strong enough spring won't even allow the needle to move at all.
You really have to remove the valve and hold the bleeder open to get any meaningful numbers. 100+ psi per pulse is preferred.
You really have to remove the valve and hold the bleeder open to get any meaningful numbers. 100+ psi per pulse is preferred.
08-03-11, 06:10 PM
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The rotary resurrection method makes no mention of removing the schraeder valve from the tester. I can only assume that's the reason it tells you that 30-35 psi per bump is ok. If you leave the schraeder valve in, the numbers become fairly meaningless, as the springs are not created equal. A strong enough spring won't even allow the needle to move at all.
You really have to remove the valve and hold the bleeder open to get any meaningful numbers. 100+ psi per pulse is preferred.
You really have to remove the valve and hold the bleeder open to get any meaningful numbers. 100+ psi per pulse is preferred.
OK, I'll give it a try with the valve removed. I just had the bleeder taped open.
I just checked the overall compression with the bleeder closed and I get about 95 on #1 and 110 on #2.
I also tested the compression again also, with just the bleeder taped open. I can't really tell how many bumps I get. It seems to be even bumps, all between 50-60 psi but I'm not sure.
Maybe I can get a video of the bumps and have you guys take a look at it. Well, that is on my agenda for tomorrow
ashley
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08-04-11, 10:54 AM
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What's the history of the engine?
I once got an engine running that had 30 PSI compression. It had been sitting for several years and the seals were stuck in their grooves.
Here's what I did:
Shot a high detergent oil into the spark plug holes. (Marvel's Mystery Oil and some standard 10w30 engine oil)... I shot some in both lower holes, turned it over one full turn, shot some more in, gave it another turn, then shot some more in.... Made sure it coated all three sides of the rotor.
Then I let it sit around for a week to soak in, turning it over every few days to mix it up.
After that, I hooked a tow strap on it and to another car. (A Honda Civic, LOL.) I had a friend sit in the RX-7 with the key on, I drove the Civic. The friend kept the RX-7 in 1st gear. I drove the Civic in circles for a few miles hauling the RX-7 behind it.
It started out as just one car hauling the other... round and round in circles doing laps around the house in the yard. Then we started noticing little puffs of smoke come from the tail pipe of the RX-7. Fuel was starting to get burned.
Slowly, you could start to hear the turbo spool if he hit the throttle.
Even later, if he hit the throttle, you could feel the load on the Civic get less and less and you could see the towing strap get some slack in it. The RX-7 would slowly catch up to the Civic.
Eventually, we stopped and had a solid 750 RPM Idle on the RX-7. We started droving the RX-7 on its own.
Sometimes these engines just need to spin.
I once got an engine running that had 30 PSI compression. It had been sitting for several years and the seals were stuck in their grooves.
Here's what I did:
Shot a high detergent oil into the spark plug holes. (Marvel's Mystery Oil and some standard 10w30 engine oil)... I shot some in both lower holes, turned it over one full turn, shot some more in, gave it another turn, then shot some more in.... Made sure it coated all three sides of the rotor.
Then I let it sit around for a week to soak in, turning it over every few days to mix it up.
After that, I hooked a tow strap on it and to another car. (A Honda Civic, LOL.) I had a friend sit in the RX-7 with the key on, I drove the Civic. The friend kept the RX-7 in 1st gear. I drove the Civic in circles for a few miles hauling the RX-7 behind it.
It started out as just one car hauling the other... round and round in circles doing laps around the house in the yard. Then we started noticing little puffs of smoke come from the tail pipe of the RX-7. Fuel was starting to get burned.
Slowly, you could start to hear the turbo spool if he hit the throttle.
Even later, if he hit the throttle, you could feel the load on the Civic get less and less and you could see the towing strap get some slack in it. The RX-7 would slowly catch up to the Civic.
Eventually, we stopped and had a solid 750 RPM Idle on the RX-7. We started droving the RX-7 on its own.
Sometimes these engines just need to spin.
08-10-11, 07:35 PM
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I finally got around to rechecking the timing on my S5 T2 swap. I removed the valve from the bottom of the compression tester this time and the gauge showed 3 bounces of 90 psi on both rotors.
Shouldn't that be good enough?
Seems as if the tps might be the problem. I set according to the 1 V method. The engine will run OK for a few seconds(if its already hot) and then start the up and down cycle again. Its not just at idle. If I try hold the rpm at 2k or 3k the rpm will still cycle over +/- 200 rpm.
Shouldn't that be good enough?
Seems as if the tps might be the problem. I set according to the 1 V method. The engine will run OK for a few seconds(if its already hot) and then start the up and down cycle again. Its not just at idle. If I try hold the rpm at 2k or 3k the rpm will still cycle over +/- 200 rpm.
08-10-11, 08:28 PM
#13
It seems strange that all 3 would be 60 lbs. instead of only 2 of them though. Maybe it's the crud of oldness. If it's not too much trouble to get the motor running you might want to let it run for a bit, maybe premix some 2-stroke oil, let it wear and seat a bit and hope the numbers go up. If you're really lucky. If it's not too hard to try then it's worth a shot.
It would also help if you knew how the motor was running before, if it was running recently (hopefully yes), if it's a lousy JSPEC, etc.
It would also help if you knew how the motor was running before, if it was running recently (hopefully yes), if it's a lousy JSPEC, etc.
It's time to rebuild.
08-11-11, 10:25 AM
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I just realized that the TPS I am using is for an NA.
According to Mazdatrix, the NA and T2 throttle position sensors have different part numbers. Also, the T2 TPS has a white plug & the NA TPS has a black plug. The TPS I am using has a black plug. I wondered why the plug on the TPS is black and the plug on the harness is white.
If anybody believes this is not true and it really doesn't matter which TPS is used, please let me know.
In any case, I'm now in need of a S5T2 TPS that has a white connector.
According to Mazdatrix, the NA and T2 throttle position sensors have different part numbers. Also, the T2 TPS has a white plug & the NA TPS has a black plug. The TPS I am using has a black plug. I wondered why the plug on the TPS is black and the plug on the harness is white.
If anybody believes this is not true and it really doesn't matter which TPS is used, please let me know.
In any case, I'm now in need of a S5T2 TPS that has a white connector.
08-11-11, 02:57 PM
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Does it matter? Is it a compatible TPS?
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