Low power on fresh engine, please help
 

Hello! I am having a very mysterious issue on my car, I recently put a built engine into my car and have gone through the break in process. after tuning the car and increasing boost the car is making significantly less power than it should be making. I have been diagnosing everything i can think of for the past several days. Any help would be much appreciated! The car made 188whp and 196wtq on virtual dyno @14psi where the stock motor made 250whp. Along with a graph that peaks at 5400rpm and torque falls off immediately on either side of 5400rpm. Here is the setup, and some things I have tried:

The engine had a break-in consisting of:
15 minutes 2k-2.5k rpm
change oil and filter
50 miles, light-moderate load, lots of vacuum
change oil and filter
150 miles, light moderate load, lots of vacuum pulls
change oil and filter to synthetic Castrol Edge 5w-40

The engine is a bp-4w (99')
head needed to be shaved so real compression is close to 9.3:1, otherwise completely stock, cams, valves, etc..
supertech pistons 9:1 compression
manley rods
wiesco xx rings
acl main bearings
king rod bearing
arp head studs

dw200 fuel pump
630cc ka-injection injectors

using NA style cam sensor as reference sensor
48mm inducer ebay 50 trim t3 that was capable of 250whp on the stock motor
Running vics intake manifold with vics currently unplugged

Here are things I've checked so far:

Checked compression while engine was warm, all cylinders tested at 180psi exactly, using a known good otc gauge

checked base timing several times while megasquirt was on fixed advance at 10 degrees, and yes I turned it back to use table afterwards, even changed rpm while checking to ensure there wasn't spark latency

Tried two different cam sensors

I originally thought that the mechanical timing must have been off for this amount of power to be lost, and the chart to look that way. I checked for a slipping harmonic balancer, used a screwdriver to see cylinder one go to tdc, the intake cam gear had the "i" facing up, the exhaust cam had the "e" facing straight up, 19 teeth between the gears. the timing mark on the harmonic balancer was lining up properly where it should be. I even made sure the cam gears were on correctly

I even increased timing in boost by up to 5 degrees which didn't change as much as it should have

The afr all look good at 11.2-11.5 at 16-17 psi, the duty cycle is at 75%

I even increased the boost to 21psi and the car still wasn't making much power at all

I made sure the throttle opens completely

Checked for any boost leaks

no vacuum leaks in the intake system

The MAT is max around 15 Celsius and the ecu is confirmed not pulling any timing, the clt sensor is working properly

That concludes everything I have checked and looked over, This issue is beyond me at this point I have no clue what would cause this behavior. I think the only people who have a chance are possibly @Braineack @18psi I'm sure other knowable people, any help would bee much appreciated and Attached are two data logs at WOT one at 13psi and one at 20psi

This might be a problem. I don't have enough experience with using a vics un-plugged...
Only thing that jumped out at me.

I have heard of lots of people that run it unplugged or take the butterfly's out. I will probably wire it into the megasquirt soon but I don't think it would affect power that drastically, but thanks for replying!

AFRs in my opinion do NOT look good, you hit 175kpa at 4700rpm (ebay turbo FTW), and your AFR is 12.2. You creep to 185kpa (ebay FTW again!), when you finally target 11s, 11.9 to be exact. But your actual is closer to 12.0-12.4. I'd add 6% fuel minimum to that row.

Your 2nd datalog looks much better, although you've increased boost from 12psi to 19psi, and you've only decreased advance by ~1 degree. I usually target at least a degree less of advance per psi. So if you're at 15 degrees at 12psi, I'd expect 11 at 19psi, not 14.

Your break in was fairly short, and I don't like the "15 minutes 2k-2.5k rpm", not sure where you heard this information, but it's bad. You have ~30 seconds to check for leaks after startup, then you should be driving with with high throttle or no throttle for 50 miles, and stay on break in oil for 500-1000, not 200.

Quite frankly, if you're making the boost you should be, your spark is where it should be, your afr is where it should be, then the only remaining factor is a rag in the exhaust or a poorly functioning engine. Try performing a leak down test, IF your break in wasn't successful, I'd expect decent compression numbers but poor leak down results.

Did the VICs runners change at all? Are they still attached? I wouldn't expect 50hp difference, but if they were in the high RPM position previously, and are now stuck in the low RPM position, that may explain some of the difference.

That afr is perfectly good and will make power the actual afr number can be a wide range and make no difference in power. Yes eBay turbo isn't the best but it made power no issues at all on the stock engine and it gets the job done.

In the map I have timing decreasing to around 11 degrees at 19psi, I am curious how it ended up at 14 from what you're saying. Maybe that's part of the issue?

I've looked into breaking in engines quite a bit every source says run the engine at around 2k rpm the first start until it's fully warm and then flush the oil and change filter. And I've seen all sources say accelerate at light to moderate throttle up to 3-4k rpm and let it decel down back to around 2k and that's what I did. I believe the engine is fully broken in and healthy with perfect compression across the board. The cylinder head is fully rebuilt by a very trustworthy machine shop

I don't have access to a leak down test currently and I'm confident the engine is healthy.

The vics runners are instant completely just unplugged solenoid but I will hook them up to see but I doubt it's that major of a power difference

Tripple check your cam timing, and make sure your crank isn’t off a tooth..

​​​​​​I have thought about it, I am very confident but I will probably be checking that again soon. There was a little speck at the top of the belt but not much and there was still 19 teeth I did the right procedure for tensioning the belt

OP needs a reality slap.
You join a forum to ask questions from folks who might have more experience than you.
When you actually hook a "big dog" like Curly (who feeds his family by working on nothing but Miatas and has for years) and he takes the time to look through your stuff and come up with his suggestions then types this information specifically for you...
For FREE, he's not making ANY money off of you.
What do you do?
You argue with him....

Had I taken the time to read your logs I probably would have come up with TOO LEAN and maybe TOO MUCH TIMING...
I didn't, I'm a busy shop owner as is Curly and just didn't care enough to take the time.
Dude, this is the recipe for disaster. You will soon be re-doing your engine build.
You have ZERO excess fuel safety net, anything happens under boost and your toast...

You should have said "Thank you SIR for your time and I will look into that shortly" even if you didn't agree with him.
You should have left him a pos-cat.
He is one of the good sources on this forum and I'm guessing he won't help you anymore.

I've been doing this shit for 40+ years, I am extremely competent, and I WOULD not call a motor good without a proper leak down test.
Don't have the tools, Purchase them, you will use them for years on everything...
They are not that expensive.

Lots of people have different ways of breaking in an engine. How you did it doesn't matter that much.
I believe 75% of the "break in" happens in the first 30 seconds it runs...
At idle...
After that try to NEVER keep it at the same RPM for any length of time. No long trips at one speed...
Up and down the range without being savage.
Staying below 75% throttle for the first 10 miles and then sending it...
Non detergent break in oil changed at the 10 mile point (and looked at under magnification for glitter) and then again at the 1000 mile point.

Curly, I just checked, the OP is 18 years old...
Do you ever get the feeling that you are wasting your time when you get a response like that?
I do...

I am sorry for how I may have come off, I do honestly appreciate all help greatly. I have since revised the tune adding more fuel in those areas in boost. as well as pulled timing back now 190 kpa area is around 14-15 degrees of timing. I will try to get a leakdown tester as soon as possible and make sure the tune is doing what it should. Do you think the power figures are low for the timing, boost, afr, ect? The last thing I am starting to think the issue may be is the turbo. Is it possible for a turbo to create high boost pressure but low airflow?

It is possible for a turbo to make high boost with low flow.
How this is achieved is a significant restriction somewhere in the intake PAST the point your took your reading and before the intake valves.
The later super crappy VSCS (?) manifold could do this with the "cold run" butterflys closed...
Not an issue on your set up...
Suggested test for you...
Leak down (hot- this takes skill, much learning is in your near future)
Exhaust back pressure in down pipe (tests your exhaust).
Pressure tests from intake track.
At turbo discharge.
At entrance to throttle body before blade.
From inside plenum.
Those will show your losses throughout the system.
Some losses are expected...

Nope, the above will not have enough exhaust flow to make the high boost anyways...
I can be wrong too....
Interested to see what your problem actually is...
Your response to my last post was excellent.
Maybe you can be trained...
I expected a temper tantrum...

Okay, thanks for your time. I am on the way to purchase a tester at napa. I will come back with the results when I am finished testing. What percentage of leak down would be a good result, and what would be a bad result?

It's been a stressful week as you can imagine, first built engine lots of time and money. I appreciate all the help, just really couldn't think of what the issue could be after all the testing and guess development a little disrespectful attitude

You don't know how to do a leak down and most of the threads regarding this leave important steps out.
I don't really have the time but I guess it's time to make the leak down thread I have been wanting to do for some time now...
Time seems to speed up the older I get...

Okay great, I can also look for other information online I'm sure. Also as an update on the way to the auto parts store the car seemed up on power. Almost felt around 230-240hp on the butt dyno. This is at around 14 psi boost pressure. I'd love to confirm this but virtual dyno had been giving me an e106 error code on the logs recently. I think it may be the turbo being irratic in actually air flow output

Very interesting observation I made on the way back home from napa (who didn't have a leak down tester so I'll have to buy one online) while driving I noticed the car seem to have power like it used to and felt great, but only part throttle. If I was roughly 60-70% throttle the boost that was there ~10psi felt great and like it should feel. So I'm thinking what if the VICS butterfly's are open out of boost which makes the engine less efficient and then close up In boost which then makes the turbo less efficient, possibly pushing the turbo further out of it's efficiency range at higher boost. If I was full throttle and higher boost it made less power, maybe cause like you said the restriction inside the manifold ie after the manifold pressure reading and boost gauge reading was creating a higher pressure than actually in the engine. Please lmk what you think of this theory and if it sounds plausible

I posted a long thread regarding leak down testing.
Check it out.
You shouldn't be hammering it till you diagnose your problem.
After you spend $$$ on another engine you will be more careful.
You must learn patience...

How well something is learned is directly proportional to how much money, blood, or "face" is lost during the learning process...

Okay I read the thread anf will follow that when the tester arrives. I was trying to do more testing and just figure it out. I'm really trying to fix the issue and finally experience what the engine can really do

Get rid of the VICS manifold and throw on a flat top, VICS crossover is IIRC 5250rpm stock which is right when you are nosediving for power. I wouldnt think if the butterflies are closed that you would lose that much power, and honestly at 19psi even before 5000rpm you should be making WAY over 200ftb the BP will peak tq on stock cams around 5000-5500 with a turbo thats not flow limited. When you set your cam gears the E on the intake side should be at 4 o'clock the the I on the exhaust cam should face 8 o'clock. You dont time the engine with them facing 12 o'clock. I bet your cam timing is off. double check the timing, and line up the marks to the back plate that is attached behind the cam gears.

I am going to wire up the vics butterfly's to megasquirt tomorrow and I believe my turbo may be damaged. I order parts to build a new manifold and I will buy a new turbo soon, probably Gtx gen 2 2871r.

I can check the timing again but I am very confident my cam timing is exactly right on where it should be

Alright, the leak down tester arrived and I tested the engine... took it for a drive until it was completely warmed up to temp then a little more. Pulled it into the garage and started testing
Test Results:

Cylinder 1: 4%
Cylinder 2: 17%
Cylinder 3: 32%
Cylinder 4: 4%

So obviously this is a massive issue with the engine, during the test I heard lots of air coming from the exhaust that I could easily feel during cylinder 2 & 3, and just a little bit from the oil cap but barely
Now the machine shop I used is very trust worthy, and well known. I've had work done there before, and the head was completely rebuilt. However I did the valve lash myself, so I am hoping the exhaust valves on 2 & 3 have negative lash and thus are leaking. I will probably check for that tomorrow and if I'm lucky that's the issue. Please let me know if negative lash would have that effect

https://cimg0.ibsrv.net/gimg/www.mia...c02688d28c.jpg

Sorry, had to. Side note, if your m54 has similar leak down issues, it's enough for BMW's DME to cut fuel to that 32% cylinder during runoffs at Road America. I didn't build that engine. Second side note, the m54 I did build finished 15th overall. Have fun rebuilding.

I mean alright

If you actually have zero lash you're screwed. The valves are burned and require re-cutting.
You don't, lash will not be your problem, you have reasonable compression test results, if you had zero lash your comp test would be shit.
Did you read the bit in my leak down test thread regarding the legends car? Perfect leak down and bad compression is a valve lash issue.
Your engine might be fine... with one exception.
What didn't occur is the valves were not lapped in. Fancy machine shops commonly use SERDI valve cutting equipment.
SERDI advises their customers that hand lapping the valves is un-necessary and can lead to issues.
The machines will commonly cut the face angle and the seat angle a tiny amount differently. Like a 15 minute difference.
They are hoping that the valves will beat themselves into a good seal.
If that doesn't make sense GOOGLE angles below 1 degree to educate yourself...
This is HORSE SHIT.
I built a MSM for a customer that I had a machine shop do the whole head on. The only machine shop I trust...
Normally I just send them the head and valves, nothing else. In this case I didn't have a nice supply of Mazda shims to complete the final valve adjustment.
I sent them the whole shooting match. I took my own feeler gauges to "verify" the adjustment before I left the shop. They are a 45 minute drive away from my shop.
The valve adjustment was off on both intake and exhaust at delivery. I brought it to their attention and they re-adjusted 16 valves on the spot. Measured, pulled cams, changed all 16 shims and replaced cams.
No harm no foul....
Right...
During assembly of the head onto the totally stock used 155K motor I did a leak down as soon as I had the head studs torqued to 40lbs.
Bad leakage on the exhaust valves, minor leakage on the intake. It helped diagnosis having the exhaust and intake manifolds off of the head.
My worst leakage rate was 25% and the best was 17% PISS POOR!
I ripped the head back off and dissembled. No lapped valves, I didn't really expect I would see lapping evidence anyway...
After I hand lapped the valves and re-assembled I had cold leak down readings below 5% on an old bottom end.
My lapping the valves reduced my valve clearance readings by .0005, 5 tenths, or 5 ten thousands which ever term you want to use.
It tightened them up a tiny little bit.
I retested the car after initial break in 1k miles in.
180 across the board- no variation at all and leak downs in the 3-7% range.
Not perfect for a full on race motor but very good for a hot street car with a used short block.
Car has 25k more miles on it now and the owner (guy who has been a customer for 3 decades and handles my website) occasionally still calls me to say "thank you for my Miata, It's still running great!

My failure in this situation was relying on another person to properly do something I could handle because I didn't have a proper set of shims. A "money" decision.
The wrong one...
If you don't do it yourself and you don't check the work that you sub out you deserve what ever results you end up with.
That machine shop you used most likely had a yellow tag on the work that said you and only you are responsible for the finished product and if you find any issues you have to bring it to their attention BEFORE assembly...
You have to be better and more precise than they do...
You have to really know what you are doing. You are young and in-experienced and didn't know this before.
This is why learning this stuff can be expensive.
The single most important thing a beginner needs is experienced oversite...
You need people like Curly to help you and it looks like you might have pissed him off.
You need to pull the head back off and hand lap the valves, this will most likely solve your issue.
This still does not fully explain your original problem.
It may be something else and this just happens to be another facet in your education.
I'm out. Good luck!

Thanks for the insight! That is really bad news for me. But I guess I'll try that. I don't entirely understand all of that and how it works. I figured machine shops would test leaks after rebuilding the head

I ain't pissed, just gloating that I was right.

Basically I've been around long enough to read these posts as this: nothings wrong, but it's down on power.

Which tells me one of those things isn't correct. I'm assuming you picked identical roads and VD settings, therefore something is wrong.

Yeah, I understand that. I did chose same settings and roads.

Also update: pulled the head last night, measured all the valve lash and then removed the cams and measured the shims again. I am pretty sure I accidentally subtracted the difference that I need from the shim instead of add because all the gaps were at least twice the size they should have been. Oops. So remeasuring and hopefully I have enough shims to get it right. Then I ordered a head gasket and I'm lapping the valves hopefully today or tomorrow, just the exhaust valves in cylinder 2 & 3

And yet another BIG mistake...
I would NEVER go through all the work/parts required to pull the head and ONLY lap the valves on your currently bad reading valves...
Lap ALL of valves, you have 16 lapping procedures to do NOT 3!
And this thread take a depressing turn, it's not fun anymore...

You NOW need to do a bunch of video watching, thread chasing BEFORE you lap the valves to know how to do that crap correctly.
I have lapped 250-300 sets in my life and the first few I did were NOWHERE near the quality level I can achieve now.
This learning cannot be done in an hour...

I also take lash measurements and do the valve adjustment with the head bolted to the engine if I can.
I'll set a new head up on the bench before installation BUT I will recheck the measurements before I fire it.
If I'm lucky I will not have to change a shim; most of the time I'm lucky but sometimes I'm not...
I catch that shit before I send it...

Curly, glad you're not pissed; you seem to be a good guy. He's gonna need you...
I apologize if I mis-spoke regarding "only work on Miatas" stuff. I was trying to make a point with the OP.
You obviously kick as on German shit as well. nice results.

He's your puppy now!
Enjoy...

I just did my lash on my fresh head and plan to check it when I bolt it in the car, how much have variance have you seen after bolting a head down?

Giving OP a prop cat for owning up to his mistakes, learning from them, and really, how many guys his age are rebuilding their own engines?

For sure, I think OP is as legit as a young dude can get and deserves help at this point.

I think a lot of people are afraid to come to MT and ask questions.... for better or worse, thats definitely the reputation here. On one hand, kinda cuts down on the repeated n00b questions, but I also know how much it sucks to try to ask a question and just get crapped on because my background wasn't as mechanically extensive as someone else who has been with the platform for decades or the search function turned up hundreds of loosely related topics.

Thanks everyone for the help, I am trying to be very good at these things and hopefully own or be a part of a speed shop at some point. I have the head off the car, I already lapped the valves on the exhaust side of cylinder 2&3. I am going to bolt the head up to the engine with a fresh head gasket torque it down to about 40 ft/lbs and redo the leak down test before reassembly. I understand if I was highly experienced in lapping valves and such I would lap all of them but right now I'm more confident leaving what I know is good. And research has told me from sources such as real street performance, and hp academy that lapping valves is more of an old school technique and a fresh cut with very light lapping just to double check is the best strategy. So because of that I'm leave cylinder 1 & 4 alone and who knows maybe I'll have to take the head off again, but more experience I guess. I'll give an update when I'm all done and the new shims are in

Update after lapping the cylinder 2 & 3 exhaust valves I mounted the cylinder head and did a leak down test, cylinder 3 was at 8% leak down and somehow mad cylinder 2 worse at 22%. So I took the head off one more time, lapped all four exhaust valves again extra good mounted the head one last time now all leak down numbers are 5% or less within like 2%. So I would say I am good to go and should hopefully be able to crack the 300whp mark if stock ignition will let me

We have always checked valve lapping with head upside down, an air line sealed into the port, valves held closed and liquid in the bowl. Fire air into the port, leaks show up as bubbles, experience helps.

Have never seen a head come back from a shop that didn't need lapped and where the difference in the test I describe is very clear. Once the test is good; we have never then seen a sealing issue in assembly from lapping.

Given the issues experienced - it would be madness to not go through re-lapping all 16 valves thoroughly to save further pain down the road. It is simple, worthwhile investment.

Sort of an old thread however I figured I would update it so it is useful in the future. When I lapped the 2 valves I also moved the shims around and used the stock ones that came on the head. My valve lash was dramatically tighter however still anywhere from 30% to 50% too loose. This made the car pick up about 25whp through virtual dyno and the VE at high rpm was increased. I assumed that the valve lapping was the reason, however after that I removed the head again and took it back to the machine shop, they inspected it and did a leakdown test, they said the head was sealing perfectly. At first I was confused however after thinking about it I realized the valve lash being so far loose would create less lift and duration through the camshaft. This is why the virtual dyno plot looks the same as an engine with a camshaft limiting power but making very good low end torque. So I finally found a source for new shims and will have those installed tomorrow and hopefully the car will finally break the 300whp mark :)