Originally Posted by SpartanSV
(Post 1490603)
They do have a plate (NA8's at least) but I verified ignition timing is correct. That should have ruled out an issue like that unless I'm misunderstanding.
The only thing I see from the graph is you're super-rich as you enter boost. 10.5-11 is good, richer than that is washing cylinder walls. |
Originally Posted by gooflophaze
(Post 1490604)
The crank timing plate is used on 96+ for OBDII misfire detection. Crank timing is still provided by the CAS, so it's not that.
The only thing I see from the graph is you're super-rich as you enter boost. 10.5-11 is good, richer than that is washing cylinder walls. So if timing is good the only way I could be making 200whp at 19psi (assuming VD is accurate) would be low compression right? That jives with my ability to run 19psi on stock ignition with no spark blowout. I'm also on stock fuel pump with 50% ethanol content and not running out of pump. Compression and leakdown come tomorrow. I'm now wishing I had measured the length of the ebay rods before I put them in. |
Either that, or you're not actually hitting 19psi - do you have a boost gauge as well? Before you turn the car on, are you seeing roughly 100kpa? I was 260hp at 13psi on a 2871 with rods 9:1 pistons and stock coils - so yes, this is an interesting issue.
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Originally Posted by SpartanSV
(Post 1490580)
I also logged a cold start to check vacuum at idle. ~39 kPa at 1025 rpm. Seems reasonable.
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Originally Posted by gooflophaze
(Post 1490606)
Either that, or you're not actually hitting 19psi - do you have a boost gauge as well? Before you turn the car on, are you seeing roughly 100kpa? I was 260hp at 13psi on a 2871 with rods 9:1 pistons and stock coils - so yes, this is an interesting issue.
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Originally Posted by andyfloyd
(Post 1490607)
That would only equate to about 12in/hg. I see 22in of vacuum at cold start. Your engine isn't making much vacuum at idle. I hope your compression numbers look ok.
Edit: Sorry I missed that you said it was on a cold start. Looks like compression is the culprit. Here's hopin for bad valves. |
Originally Posted by andyfloyd
(Post 1490607)
That would only equate to about 12in/hg. I see 22in of vacuum at cold start. Your engine isn't making much vacuum at idle. I hope your compression numbers look ok.
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Originally Posted by SpartanSV
(Post 1490612)
Actually, how did you calculate 22in? Can you share your baro and map values?
I just googled kpa to in/hg conversion. My boost gauge reads in in/hg but my Hydra confirms the gauge is indeed correct. |
Results are in.
Leakdown: #1-13% #2-22% #3-9% #4-9% Compression Gauge #1 #1-125 #2-117 #3-121 #4-128 Compression Gauge #2 #1-161 #2-140 #3-152 #4-162 Leakdown points to exhaust valves. I got a rebuilt head through a core exchange service on ebay. Has less than 1000 miles on it but I'm pretty suspicious of the work performed. I found missing pieces in 3 or 4 hydraulic lifters. I'm not completely convinced the numbers are bad enough to be responsible for the lack of power but I can't come up with anything else. I think I'll clean up the tune and pay the $75 to put the car on a local dyno to see what it's actually at. I also disconnected the exhaust at the turbo and took a quick drive. No noticeable improvement. |
Alright so I couldn't leave it alone. I moved cam timing a tooth in relation to the crank. It's soooo much better.
So if the pics I posted show a properly timed engine and moving timing a tooth made a significant improvement then the logical conclusion is that the damper has slipped. Correct? This is the same 4th gear pull to 5k from my first post. https://cimg5.ibsrv.net/gimg/www.mia...7d909f192f.png This is a 4th gear pull to 5k after changing the cam timing. https://cimg2.ibsrv.net/gimg/www.mia...25d539ce62.png Nearly half as much time to go from 3k to 5k. |
It's possible the crank pulley slipped. You could pull off the pulley and check the keyway on it to confirm. You should upload that into VD and see what she's putting ito for power now.
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Originally Posted by andyfloyd
(Post 1490779)
It's possible the crank pulley slipped. You could pull off the pulley and check the keyway on it to confirm. You should upload that into VD and see what she's putting ito for power now.
That pull was 224hp 243 lbft at 5k and climbing. 17psi. Not setting the world on fire but if the damper slipped then my ignition timing is going to be off as well |
Originally Posted by SpartanSV
(Post 1490780)
I don't think it's a key way issue. Someone correct me if I'm wrong, but I believe the issue is that the damper is made up of two pieces separated by rubber. When the rubber gets old and weak the outer piece which has the timing marks will rotate in relation to the inner piece.
That pull was 224hp 243 lbft at 5k and climbing. 17psi. Not setting the world on fire but if the damper slipped then my ignition timing is going to be off as well |
Originally Posted by andyfloyd
(Post 1490781)
Yep you may be right. I have bunch of parts if you need a damper pulley, mine is off an nb engine but should work if you need it. Lmk. Glad it's running better for you, nothing worse than a new built motor not performing up to snuff.
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That difference in results definitely points to a failure of a 20 year old rubber damper. The part that doesn't move is the notch in the crank pulley, which is the part you should be lining up with the cam timing marks. The timing marks on the damper are only for the spark timing.
So show us the crank timing mark and the cam timing marks at the same time, please. |
Originally Posted by SpartanSV
(Post 1490776)
So if the pics I posted show a properly timed engine and moving timing a tooth made a significant improvement then the logical conclusion is that the damper has slipped. Correct?
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I would say that the screwdriver test could easily be off by 5 or 10 degrees plus or minus and that one crank pulley tooth is within the margin of error.
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Originally Posted by sixshooter
(Post 1490843)
I would say that the screwdriver test could easily be off by 5 or 10 degrees plus or minus and that one crank pulley tooth is within the margin of error.
Soooo best way to confirm is to check against the actual crank timing mark on the block? |
Originally Posted by SpartanSV
(Post 1490879)
This. The screwdriver test shows it's in the ball park but it's less than precise.
Soooo best way to confirm is to check against the actual crank timing mark on the block? https://www.miata.net/garage/images/TBELT5.JPG |
Originally Posted by SpartanSV
(Post 1490879)
This. The screwdriver test shows it's in the ball park but it's less than precise.
Soooo best way to confirm is to check against the actual crank timing mark on the block? EDIT : Sixshooter beat me to it |
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