I Have a Problem
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Increasing compression is only good for about 3% power gain over stock compression
Not sure whether this is some kind of extreme generalization, or a valid piece of data from a non-relevant discussion...
Ideal static compression ratio is heavily dependent on camshaft timing. Cam specs greatly affect VE across the rev range. When VE is decreased, there's less air getting in, but the final volume after compression is the same, so your "dynamic" CR will be lower. You need a higher static CR to get the the same amount of "dynamic" compression of the charge before ignition. Generally speaking, bigger cams require more compression, especially to restore torque that is lost in the low end/midrange which was lost because increased valve overlap results in a lower VE in those rev ranges..
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Not sure whether this is some kind of extreme generalization, or a valid piece of data from a non-relevant discussion...
Ideal static compression ratio is heavily dependent on camshaft timing. Cam specs greatly affect VE across the rev range. When VE is decreased, there's less air getting in, but the final volume after compression is the same, so your "dynamic" CR will be lower. You need a higher static CR to get the the same amount of "dynamic" compression of the charge before ignition. Generally speaking, bigger cams require more compression, especially to restore torque that is lost in the low end/midrange which was lost because increased valve overlap results in a lower VE in those rev ranges..
It is a generalization
Static compression ratio does not depend of camshaft timing, as it is simply using the volume of combustion area at the two most extreme points of stroke. The effective compression ratio certainly changes when you get into cam profiles and variable timing and things of that sort, which is not something I've delved into, as the static ratio of this engine has never been accurately measured, therefore dynamic is also speculative.When looking at adiabatic compression of the otto cycle, ~1 point of compression increase yields around 2 to 4 percent increase in efficiency as a result of more heat being generated by the compression of air itself and intake temp being the same (ideally) instead relying on the combustible fuel source to provide that energy. As your delta T increases so does the area in the otto cycle which is the work output.
Anywho, doing any modification without supporting it is silly, but when people with stock M50's talk about just increasing compression and expecting to see large benefit it is worth noting that they will be spending a fair bit of money for little gain.
Positive manifold pressure is a wonderful thing in an engine is what it really all boils down to.
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Man I'm good at buying vehicles that had things living in them.
Noticed some yellow/orange chips near the sunroof crank, and had been getting a more present animal smell in the cabin.
Started pulling the headliner down around the doors and more foam was rolling out.
Lovely.Add taking the current headliner out and replacing it to the list of things to do.
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Headliner was cleaned out and tucked back away for a later date .Cooling this engine had been sub optimal before, so I threw money at the problem.
Stewart water pump, Z3m triple core, SPAL branded fan.Clearances are tight, but man does this help keep temps in check!
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Oh, new wheels on. 595rs-rr's because RT660's were hella backordered. 225/45r15
Conclusion, lightweight, but 15's look meh in my opinion. -
Oh, new wheels on. 595rs-rr's because RT660's were hella backordered. 225/45r15
Conclusion, lightweight, but 15's look meh in my opinion.Call me lame but the 15's look perfect.
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Call me lame but the 15's look perfect.
+1
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Call me perfect but the 15's look lame.
Perfect
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I've been chasing down a tick from the rear of this engine for a bit now, and had some findings yesterday.
The previous work I've done was removing the cams and opening and cleaning all the lifters, which didn't change anything. I then replaced lifters on cylinder 5 and 6, which did not change the noise.
I tried heavier oil which helped reduce the noise a bit, but then was loud again, thin oil made it much worse.I am seeing metal in the oil so it was time to pull the pan and see what bearing I was losing. The piece upper right was from something else, but this is what was coming out of the back corner of the oil pan as I was pulling it.
I found the oil pump chain to be very slack, but intact.
I can't leave the chain that loose so I'll be pulling the engine seeing as I'm opening up a larger can of worms here than intended.
I have not seen any glaring signs of bearing failure which is good (no discolored caps) but I have yet to pull any caps. That'll wait until the engine is on a stand.Fun with engines!
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Bearings from rear most main cap, that'll do it.Crank looks fine, bearings didn't spin.
Will be taking the crank out and redoing all the bearings and verifying clearance along with replacing the oil pump chain. -
I’m sure you already did, but check the oil pump
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I’m sure you already did, but check the oil pump
In what capacity?
I have verified that the pump is still a pump, which is always nice! -
In what capacity?
I have verified that the pump is still a pump, which is always nice!Check the side clearance and inspect for anything that would cause lower output flow. Also check the relief valve spring, I doubt that is the issue though because typical idling pressure is very low anyway. Did you have an oil pressure gauge?
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Check the side clearance and inspect for anything that would cause lower output flow. Also check the relief valve spring, I doubt that is the issue though because typical idling pressure is very low anyway. Did you have an oil pressure gauge?
It did for awhile, then it went missing right around when I got it. It's in my amazon cart haha.
I question if the horrid old clutch in there didn't help the situation any, as it would chatter like a mother.
Previous dude also speculated that it was ticking shortly after assembly, but not as bad.
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Well, fired it up and it sounded the same.
Pulled the head and brought it to the shop, as that's the only thing left.
Dude called and said I had a bent valve or 24, so at least root issue was found. He noted the guides were ovals so it had been this way for quite some time, must've been a very subtle bend on most of them.Ordered some goodies and will be back better than ever.
+1 on the intake for fun
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Supertech Upgraded dual spring kit
Supertech Stock size exhaust valves
Supertech +1 Intake Valves
Supertech Single Groove Valve Locks
Supertech Valve Seals
Achilles Upgraded Valve Guides
Further head port work to accommodate and capitalize on the oversized intake valvesI'm looking forward to the re-tune on the dyno, last time my crank sensor was on the fritz so I was limited to 6100ish RPM depending on engine temp. With the new springs and such we will happily running it up nice and high in the revs without concern!
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The results are in!
Last tune vs new tune
That pickup in torque is very noticeable, the top end doesn't feel all that much different but feels much smoother than last time.
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