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Discussion Starter #1
It would be great to get any ideas on this but I finished a new turbo build on my d16y8. Set wastegate to 5 lbs. After my first run hitting positive pressure which did not go far above 1psi I started experiencing major acceleration issues. Symptoms include:


slow acceleration on flat and up hills as if I had a exhaust backup
not being able to reach even -1psi of vaccuum with WOT,
low power all around.
Again, this happened after my first boost run.

Other info. I was running a slightly modified base map with turbo settings on nep-tune.
There are no intake clogs or exhaust clogs as I have disassembled both including intercooler and I do not have a cat.
I have done both hot compression and leak down tests with 155 compression in all. And average 35 % loss on leak down test.
Tested fuel pressure at rail, after filter, replaced filter, tested pump pressure and electrical, cleaned injectors.
Distributor is new with all voltages reading properly to the wires, no sign of misfire.
Iridium Ngk plugs less than a year old and we're inspected.
Ran with no connection from turbo to TB and still had symptoms, turbo spools with exhaust with no end play or noise, oil pressure is fine.
Ran both a stock chip and a new basemap as well as a stock ecu and same problem.

Any more ideas would be wonderful as I feel like I've ran out of people to ask. I've searched the forums and am desperate.

Mike
 

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Two men shy of a group
99 civic sedan ex
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Who made the basemap? I'm going to go out on a limb and bet it's the tune, if you can swap the stock rom and basemap with same issues then it sounds like the ecu is freaking out seeing boost. I'm not understanding what you mean by -1 psi vacuum, vacuum is measured inhg.
 

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Discussion Starter #3
What I mean by -1 psi is relative to atmospheric pressure which is what shows on my gauge. Converted to 27 inhg. Sorry, the basemap was generated through the neptune rtp. Wouldn't it count the ecu out of the picture if I am getting the same symptoms with 4 different tunes including stock? And to add. I have not been able to hit positive boost at all since then and with all different tunes, it won't even reach even atmospheric pressure with wide open throttle. It feels like a build up of backpressure as I am able to slowly climb rpm but lose all the power whilst Giving off a compressed air sound like there is a blockage but there has not been.
 

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35% loss on leakdown?

with turbo not hooked to intake assembly (so running stock for most part) do you get any pressure out of the valvecover breather or from oil cap once removed? (at idle)


Keep in mind, if all you did was throw on a map without actually trying to TUNE, you might have jsut baked your motor and cracked a valve.


What was the numbers from a compression test? was 155 from one cylinder, an average, or were they all so close you just picked one number?
EDIT saw you said ALL. my bad
 

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I need to slap my self for forgetting!! Did you make sure cam timing and mechanical timing are dead on?
 

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Discussion Starter #6
First of all I meant -2inhg from my earlier post. Yes it was 35 +/-5 for leak down. Nothing past 39%. 155+/- 3 for all compression tests to cylinders. My timing marks are dead on still. Timing belt is only 9 months old with good tension as well.
As for the map. It was tuned enough for how I was driving as my wideband gauge stayed within 13-15 afr and is now tuned the same with high air to fuel only appearing while downshifting at high vaccuum and rpm. But where I experience issues has a good af ratio.

I have not checked if pressure was leaving the cover at idle with turbo disconnected from TB. I will give that a shot tomorrow but what am I looking for as far as diagnosis?
 

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Two men shy of a group
99 civic sedan ex
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What I mean by -1 psi is relative to atmospheric pressure which is what shows on my gauge. Converted to 27 inhg. Sorry, the basemap was generated through the neptune rtp. Wouldn't it count the ecu out of the picture if I am getting the same symptoms with 4 different tunes including stock? And to add. I have not been able to hit positive boost at all since then and with all different tunes, it won't even reach even atmospheric pressure with wide open throttle. It feels like a build up of backpressure as I am able to slowly climb rpm but lose all the power whilst Giving off a compressed air sound like there is a blockage but there has not been.
It won't matter if you use 4 different ecus if they don't have the correct fuel ignition maps, if you have the turbo plumbed into the intake and larger injectors connected then a stock ecu will not run the car, you can get the car to fire maybe on stock ecu with just larger injectors but then it's dumping way to much fuel. I don't know much about neptune, does it have a y8 stock rom? I know that a y8 has different fuel and ignition maps compared to a z6 and needs adjustment to run the car.

Also did you just load a rom and expect it to run a turbo motor? Like I said I don't know much about neptune but I know in crome you load a map then add boost columns then adjust fuel and ignition
 

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Brokedick Millionaire
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That much leakdown %, time for a rebuild

Smooth walls from a melted piston yielded 160 psi and 20% leakdown AFTER I dropped in a used set of pistons.
 

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Two men shy of a group
99 civic sedan ex
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That much leakdown %, time for a rebuild

Smooth walls from a melted piston yielded 160 psi and 20% leakdown AFTER I dropped in a used set of pistons.
I thought something was up with his leak down but I wasn't going to say anything because I've never done a leak down myself, I thought you wanted less than 10% leak down per cylinder?
 

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Sloppy Jalopy
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And to add. I have not been able to hit positive boost at all since then and with all different tunes, it won't even reach even atmospheric pressure with wide open throttle. It feels like a build up of backpressure as I am able to slowly climb rpm but lose all the power whilst Giving off a compressed air sound like there is a blockage but there has not been.

ok well , when you change your map I wouldn't call it a tune because well it hasn't been tuned it really is almost random .

we need more info about your setup and detailed pictures of the engine bay .
ecu
map sensor
injectors
what wideband
what is a 'good' air/fuel ratio
your looking at datalogs ???


The backpressure and loosing all power and compressed air sound ,
you are running way rich most likely .
 

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Discussion Starter #13
Well with stock injectors I ran a y8 stock map both with the basemap supplied from chrome and the ecu that matches the engine. Boost was accounted for with all neptune maps and have been running ~14:1 afr so I have not been running rich. I'm using a Bosch wideband sensor. Electonically it seems good with datalogging. Stable af ratio with acceleration only running in the 13:1 area during acceleration. Does anyone know acceptable leak down specs for a y8, because the symptoms are similar to burnt pistons, I did a cold leak down and was around 8% leakage on all cylinders.

Also, is it normal to have burnt pistons but have all of them fail at once? I was thinking the engine is needing to be opened but it's just a pain so I wanted to get some opinions, but it's looking like with all my diagnosing that the leak down is the only thing alarming, I just figured that it wouldn't be acting this terribly until I had 50% leakage.
 

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DIY Guru
96 Ranger-stock
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That much leakdown %, time for a rebuild

Smooth walls from a melted piston yielded 160 psi and 20% leakdown AFTER I dropped in a used set of pistons.
I thought something was up with his leak down but I wasn't going to say anything because I've never done a leak down myself, I thought you wanted less than 10% leak down per cylinder?
Like bone said, 35% leakage is a major issue. You need to pull it apart and inspect.

I'm seeing 2-3% on mine across all cylinders in a fresh rebuild


I am with Transzex... 35% is horrid, anything over 30% is cause for a rebuild.

A high mileage well running engine will be in the 15-18%

A fresh rebuild on the stand should be less than 8% and drop a bit once the rings seat


So you have 35% leak down hot and 8% cold

Check your gauge, somethings way off, I have not seen a fluctuation that far apart before.
 

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Discussion Starter #15
I was planning on redoing the hot test. And warming back up after the first 2 for better accuracy. I'll have to wait until tomorrow though. I was going to start rebuilding a new y8 in the next couple months so I could increase boost in the spring anyways. What are your thoughts if I redo the test and oil the cylinders to do it properly and see 20-25 and vatiation of +/- 5 tops? Still take it apart ? I hate buying new gaskets so I'd just like to be sure
 

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Meat Popsicle
91 CRX Si
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Make sure that the engine isn't rotating when you pressurize the cylinder. I use a 18" breaker bar and a 1" concrete block/slab to wedge the breaker bar against the floor once the cylinder is at TDC.
 

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we accidentally did that t9 my brothers old turbo mazda. replaced the timing belt and didn't verify mechanical timing and it had really bad power.
 

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Discussion Starter #19
I aligned at TDC using cam points then checked the pully marks and was dead on. I hoped I'd have found the problem there? It is slower than stock the way I got it a year ago. Feels like 80whp. I'll make sure I use the breaker bar when doing my next leak down. But when I set my leak down tester at 0 leak before plugging it into the cylinder. It only shows 1psi going into the cylinder with my compressor at 80psi. The tool allows up to 100 psi . After plugging it in on the second test I slowly turned the inlet psi up and as I did the leakage needle showed even lower leakage. I would have been able to get under 10% but I feel like that is not how my specific tester is supposed to be used.

Is there any recommended lubricant other thsn engine oil I should be spraying on the Pistons before the test to better mimic a running piston?
 

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Well with stock injectors I ran a y8 stock map both with the basemap supplied from chrome and the ecu that matches the engine. Boost was accounted for with all neptune maps and have been running ~14:1 afr so I have not been running rich. I'm using a Bosch wideband sensor. Electonically it seems good with datalogging. Stable af ratio with acceleration only running in the 13:1 area during acceleration. Does anyone know acceptable leak down specs for a y8, because the symptoms are similar to burnt pistons, I did a cold leak down and was around 8% leakage on all cylinders.

Also, is it normal to have burnt pistons but have all of them fail at once? I was thinking the engine is needing to be opened but it's just a pain so I wanted to get some opinions, but it's looking like with all my diagnosing that the leak down is the only thing alarming, I just figured that it wouldn't be acting this terribly until I had 50% leakage.
Your going to run out of injector before 5psi with stock injectors. Also your going to run out of fuel pump really quick too.
Word of advice, take off the turbo kit, save yourself $1000 so you can get a fuel setup and pay a tuner.
 
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