CA18DET powered sentra update........

[boost_boy]

was this compression test done cold or hot?

Both!

Dee

[fraz]

What pistons are you running? it appears to me that you have dropped the compression ratio, as everything seems normal in the way of air/fuel and similar compression across all four.

Did you get the crank ground? i dunno, to me it looks like you have just fitted some lower comp pistons and now its a bit of a slug off boost, but will go well with serious boost

[zero_gripS13]

ummm... im pretty sure he using 8.5:1 ....and i dont think pistons would be the reaosn why his compression numbers are so low..

[float_6969]

Thanging the compression ratio doesn't change the compression test results THAT much. AT 9.5:1, I ran about 180-185psi.

[zero_gripS13]

leak down results, any new ideas...updates?

[boost_boy]

After 500 miles of driving, compression still is about the same. I added oil to each cylinder and the compression went up about to about 105psi which is what this engine got anyways. Frustrated just a bit, I broke out my compressor and leakdown tester and begin this fatal process. Results were as follow:

Cylinder 1 had better than 60% leakage and it leaked down at a so-so pace. The air can be felt lightly from the breather and when the breather is plugged, the air can be felt from the oil return line. Conclusion: New rings possibly not yet fully seated.

Cylinder 2 had 90% leakage and stayed constant at 90%. When I moved the from TDC, it went to 100% immediately. After I removed the turbo & manifold and repeated said test, at least 70% of the air was coming out of the exhaust port. Conclusion, exhaust valves are not seated correctly .

Cylinder 3 was the same as cylinder 2 only the air can be felt from the throttle body at a near 70% rate. Conclusion: exhaust valves are not seated correctly

Cylinder 4 was the same as cylinder 1, except the air is felt a little better than cylinder #1.

I guess it's safe to assume that valves are not sealing and it has nothing to do with the camshafts. Off with the head, I guess .

Dee

[Rookieca18det]

That terrible man I was hoping to swing by get ride in the passenger seat, though if its any conciliation the bottom end I got from you is holding great. I beat on her regularly and she just keeps on trucking. Hope to hear some good news about the sentra soon man. peace

[boost_boy]

That terrible man I was hoping to swing by get ride in the passenger seat, though if its any conciliation the bottom end I got from you is holding great. I beat on her regularly and she just keeps on trucking. Hope to hear some good news about the sentra soon man. peace

Good to hear that bottom end is still holding up! So far, this new one is holding pretty good as well seeing it has only 500 miles on it. I have astock head that I may try when this hurrican thing goes down and we'll see if it helps. Holla at you lata'.....

Dee

[float_6969]

Are you SURE it's not the cams? Do you have a spare set of stockers setting around? For as little trouble as it is to swap cams, I'd through them in just for peace of mind before you start pulling the head apart.

If that doens't fix it, I'd beat your cylnder head repairman in the face with that junk head and ask him how he feels about that. There's just no excuse for that...

[float_6969]

And the rings should be seated by now. Were they properly gapped? No offense, but I'm not super impressed with your engine builder.

[Akihisa]

Do you have solid lifters or still the hydraulic ones?

[boost_boy]

Are you SURE it's not the cams? Do you have a spare set of stockers setting around? For as little trouble as it is to swap cams, I'd through them in just for peace of mind before you start pulling the head apart.

If that doens't fix it, I'd beat your cylnder head repairman in the face with that junk head and ask him how he feels about that. There's just no excuse for that...

My bad guys, I screwed-up the leak down test (what a ). I didn't rotate the engine to bring cylinders 3 & 4 to TDC which would be the reason why they leaked at 90% and air was flowing through the intake and exhaust ports. But after over 500 miles, I'm still not impressed with the compression readings. AT about 800rpm vacuum is at -8hg.

Unfortunately Ryan, I've already pulled the head. After the hurricane, I'm going to install the complete stock head with stock headgasket and test compression again. I gave it some bursts and it did well, but it is just too low on compression to be acceptable. After puttin oil into the engine and getting readings nearly identical to compression readings without oil, I started staring at the head. The engine should just have more compression than this.

Dee

[CA19DET]

Quote »And the rings should be seated by now. Were they properly gapped? No offense, but I'm not super impressed with your engine builder. [/quote]its either the rings or valve seats.. good luck

[float_6969]

The stock head should tell you if it's the rings or the valve seats. I have a feeling its the valve seats and that the head is going to fix it. I had my builder overgap the rings on purpose because I plan on running 2 power adders and the extra gap reduces the pressure on the ringlands. I've still got great compression, but just a little more blowby than stock. The blowby is clean though and has no/little oil in it.

[boost_boy]

Just an update, it was something with the head. The car now has a totally stock CA head and cams back on it and it runs like a bat out of hell. Vacuum sits at 21hg@850rpm and compression sits at 160psi all the way across. Like I stated before, since I started relying upon my chosen machinist, all my problems started. Word of advice, check your own tolerances and clearances after machining because some of them treat import stuff like domestic stuff (Half-@$$).

Dee

[boost_boy]

Just an update, the sentra's problemed CA has about 4000miles on the rebuilt engine bottom end with completely stock CA head and the car is running wickedly. With boost set @ 15psi and timing moddestly set, the car/engine screams with authority. The 8 year old KYB/Intrax suspension is up for a replacement soon and have served it's purpose. The car's gearbox with helical LSD is as stout as they come and it performs like a trooper as well. When the car hit's 5000miles, I will rest and continue on with my drag sentra with the fully built CA and transmission. This car will be decked-out with expensive goodies, but the engine takes the cake. You gotta love this little engine..........

Dee

[Kouks]

Awesome, wish mine was running, install in progress.