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".

 

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?

 

The only 2" reference seems to be to the inlet to the FM downpipe casting.

--Ian

 

I'll try disconnecting the exhaust system and butt-dynoing it, as well as the cam timing. Thanks

 

​​​​​​​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

 

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?

 

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
​​​​​​​

 

We all missed it.

 

no. its super low even for 1.6

 

Nah the Nissan one is definitely a journal bearing, it doesn't spin freely when spun by hand - I think the red top SR20s got the ball bearings and others got journal? Idk, too many chassis codes to make sense of those cars

 

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

 

need leakdown numbers

 

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.

 

with a 2560, and 16° timing, and 16psi, and a 3" exhaust -- it should be closer to something like ~250-260rwhp on a dynojet.


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?

 

Either the motor is one foot in the grave or the dyno reads really low.

 

Here ya go

 

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