I think its exhaust restriction personally
That being said, double check that the mechanical cam timing is correct (set the engine at TDC and make sure the cam gear marks line up) |
I agree, some of it will most likely be the exhaust restriction. I picked up a ton of torque and spool when I went to a 3" exhaust from a 2.25" racing beat on my 2560. I imagine you have a similar restriction as at the same boost I was making 260ish hp if I remember right (with an NB head, mind). This was with the FM elbow coming off the turbo to their 4-bolt flange (that I hate) to 3" running the full length back. When I inquired with FM about the tube, I believe I was told it was 2.5".
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If your exhaust is as-described (expanding from turbo outlet diameter to 2.5" in the downpipe casting and then at least 2.5" from there back with no cat or muffler), then it's not the exhaust. A 3" is definitely better, but a proper 2.5" can do 250 whp easy.
If there's a huge dent where you hit a rock, then that's another story. :) Random thought: have you checked your spark hardware latency? Set spark to a fixed 10 degrees, use timing light to check at idle, now use it to check while holding at 6000 RPM and make sure it's still 10 degrees at higher RPMs. --Ian |
^I think he said it was 2" at some point. Im guessing a stock mid pipe?
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Originally Posted by Full_Tilt_Boogie
(Post 1467288)
^I think he said it was 2" at some point. Im guessing a stock mid pipe?
--Ian |
Originally Posted by Full_Tilt_Boogie
(Post 1467277)
I think its exhaust restriction personally
That being said, double check that the mechanical cam timing is correct (set the engine at TDC and make sure the cam gear marks line up) |
Originally Posted by codrus
(Post 1467276)
So it's a Nissan OEM part?
Have you checked it for shaft play and wheel damage? --Ian |
The dyno graph looks like it's choking up top, which would tend to support the exhaust restriction theories. You said it runs pretty even with your friend's F20 miata, but those typically dyno like 180-190hp and 5tq right?
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Originally Posted by fpscolin
(Post 1467302)
It could use a rebuild, no shaft play from side to side but a bit in/out. That's pretty far down on the list of 'todos when my student budget allows it" though, until it starts smoking or sounding like a supercharger lol
Radial play would be bad, a small amount of axial play is normal. Sounds like yours is good. --Ian |
Originally Posted by fpscolin
(Post 1467238)
1.6L
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no. its super low even for 1.6
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Originally Posted by codrus
(Post 1467309)
2560s are a ball-bearing center, which is not a DIY rebuild. "Rebuilding" one consists of sending the CHRA to a garrett authorized shop and they'll sell you a new one at a discounted price of $450 or so.
Radial play would be bad, a small amount of axial play is normal. Sounds like yours is good. --Ian |
Originally Posted by fpscolin
(Post 1467238)
1993 1.6L running MS2PNP, gt2560 @16psi, 420cc injectors. BEGI manifold, FM downpipe and 2.5" straight pipe exhaust
Made 180whp/wtq on a Dynapack As far as I can tell, the engine is happy. Doesn't cough oil and runs smooth (although I haven't gotten around to doing a compression test). AFRs are on point. Why are my numbers so low, when similar setups have been pushing 225+ with less boost? I've attached my tune as well as a picture of my timing table. Small update for everyone - warm compression tested the car, the mystery continues... Cyl 1: Inital: 90 Final: 190 Cyl 2: Inital: 90 Final: 165 Wet: 180 Cyl 3: Inital: 90 Final: 165 Wet: 190 Cyl 4: Inital: 100 Final: 190 :confused: |
need leakdown numbers
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Well, you have worn rings but I don't think you should be that down on power...
I see that you've checked base timing, but it's possible that your pulley has slipped. You could be running way less advance than you think you are. My pulley had slipped over 15° from stock. Drop a socket extension down #1 and check it against your TDC mark. |
Originally Posted by 18psi
(Post 1467319)
no. its super low even for 1.6
having only 13° spark and a 2.5" exhaust is NOT helping. |
How about a picture of the data tag on the CHRA? Positive it's a GT2560r?
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Either the motor is one foot in the grave or the dyno reads really low.
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Originally Posted by HeavyD
(Post 1473347)
How about a picture of the data tag on the CHRA? Positive it's a GT2560r?
Here ya go https://cimg0.ibsrv.net/gimg/www.mia...4f899fd367.jpg |
When you look at the dyno you can see the torque falls off really hard at the top.
Its either a restricted intake or exhaust, or something else isnt ok. Dann |
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