2.3 problems- never ran right under boost

[Kmiller86]

Ever since I put my 2.3 in I have had problems. It has never ran right under boost. It drives fine. I can spool up the turbo but once it hits full boost it falls on its face and my wb shows lean. It doesnt matter if im running 15lbs or 25, same thing only when it hits full boost. So I did a boost leak test and found that it will not hold much for long. It can hold about 25 for 4-5 seconds before it is all the way to 0 again. I used the tester directly on the tb and could find no leaks other than alot of air leaking from the oil fill cap. I did a compression test yesturday and it came out to be 160-160-155-160. Does the problem I describe sound like an engine problem or a tuning problem. I have dsmlink for tuning.

BTW with my old motor it would hold 25psi for 15mins before it went back to 0.

Thanks.

 

[nightspeed87]

what pistons did you use, stock 1g pistons? Because only stock 1g pistons have comp numbers that low.

So you say it falls on its face soon as it hits full boost, and only when it hits full boost?
Perhaps your having a fuel problem, does it seem like fuel cut?
Maybe timing is getting snatch to hell from a fuel problem as well? But to have a stroker and to be running over 20psi at all Id image youd already have a logger.
What does your timing look like, and is the engine mechanical timing correct?........trying to help you brain storm.

 

[Kmiller86]

Pistons are JE 8.5-1 compression stroker pistions.

Yes it falls on its face only once it hits full boost no matter where I have it set at.

Fuel problem is possible but I dont think that is it.
-850cc injectors
-walbro 255 hp rewired
-base fuel set to 50psi
-dsmlink showes injectors were at 90% at 26psi

I have dsmlink as my logger and tuning equipment and I am fairly good i think. When I had my 2.0 i ran 28psi on pump gas with the same turbo i have now.

Timing is the stock 2g map and looks fine no knock, even when it falls on its face.

Yes the engine timing is correct and checked several times over.

Also on my dsmlink logs, my WB02 will spike very lean (14.9) when this happens, but the calculated a/f ratio stays 11.1 and doesnt spike, I have a log if you want to see it.

It feels like a huge boost leak, but I cant find one except for all the air coming through the oil fill cap when i do a boost leak test. but the compression is good????

Thanks again for the ideas and help.

 

[pneumo]

Perhaps the PCV valve is leaking boost into the valvecover?

I have a feeling the engine is misfiring from all the extra fuel, that's why you see a lean spike when it falls on it's face. A misfire will pass unburned oxygen past the O2 sensor giving a false lean signal.

 

[Kmiller86]

i dont have a pvc valve it vents right to a catch can, this is how i had it on my 2.0 and there were no problems.

 

[pneumo]

Your compression is a little low for 8.5 compression ratio. Pressure in the crankcase could be from leaky rings. Bad or improperly installed valvestem seals could leak boost into the crankcase, too.

I still think you should lean it out and see if the lean spikes and backfires go away.

 

[Kmiller86]

The compresson could be slightly lower that 8.5 because the head has been resurfaced 2 times and the block was decked. I also have a Cometic metal headgasket.

I accually havent drivin my car since july when this started happening, i didnt have the time or the money to try to fix it, but from memory and looking at some logs that I had, I did try to both lean out and richen it you to no affect, same lean spikes on the wideband only.

thanks

 

[95blackGsTurbo]

If the head has been resurfaced and the block decked then your compression numbers will be higher than normal. Why so high on the fuel pressure. It should be around 43psi. Do you have any sort of logger to see if you are pulling timing. That i probably your problem. How is your knock sensor? Are you sure you got it plugged back in?

 

[andymoraitis]

I'm with Adam on this one. I'd love to see a DSM Link log to better pinpoint what the problem is. The assumption that decking the head will also raise compression is correct. It could be something as simple as a MAFT that's going bad or a failing O2 since it seems to be open loop and higher airflow related. Get us a picture of a fresh set of plugs after a WOT pass so we can read them.

Please get back to us with more information,

Andy

 

[nightspeed87]

yea your compression should be more like 180 across the board,
does your dipstick ever pop out after a wot pull?
and do you have a afpr, 50 psi sounds pretty high. And when you say the car falls flat on its face, like what do you mean, its stop accelerating, looses power, hesistates, bogs?

You could run into fuel cut from a really rich state too I believe, but then again you have 11.1 ratio and dsmlink wouldve told you that. Id just try to remove all the leaks it has first.
I agree with what Andy and Adam said too, id assume your pulling timing. Make sure the timing belt is in the right position also, possible your timing is off a tooth or something, ? I dont know if that would be a feasable cause but still something to check out.

 

[95blackGsTurbo]

Get us a picture of a fresh set of plugs after a WOT pass so we can read them.

Andy

Send a set of plugs to Champion. For $5 they will read your plugs. And not that, white is lean black is rich crap. I sent a set of plugs to them out of one of my 383's I had built...but looking at the plug and tearing it apart and looking at the inside they came to the conclusion that I needed 2 more degree's of cam timing and to run 1 jet size smaller. They were right on the money and it fixed the problem. You would be amazed what someone can figure out just by analying a plug.

 

[Kmiller86]

Thanks for all of the ideas. I will try to answer all the questions that i can but I am at work so i will need to wait until i get home to get a dsmlink log for you guys.

I have the fp set to 43 psi, I HAD it set to 50psi for a time while trying to figure this out.

According to dsmlink I am not pulling any timing until it starts to loose power and stop accelerating. It feels just like a huge boost leak and sounds like on also or if you have ever had an injector wire come off under boost, it feels like that. I am at full timing advace when this happens then on the log it goes lean first then it pulls 4 degrees of timing due to knock.

I also have tried to keep it wot past this point, but the rpms just dont go up, i can not log past where the problem occures.

I was thinking it could the the GM Maf, but that still doesnt explain why I am leaking air from the oil fill cap. I have also changed the maf comp in dsmlink whith no affect other than the calculated a/f ration changes, the wb still does the same think at the same spot in the log.

I have checked the valve timing several times and it appears to be correct. But it wont hurt to look again. The plugs are new when i built the motor about 600 miles ago and they are gapped to .028.

I have never had the dipstick pop out.

If the compression should be around 180 accross the board and mine is 160 accross the board, i can rule out bad rings correct? Could the cams beeing off a tooth explain all the cylinders haveing compression consistantly low.?

Once I get home today I will post up some dsmlink logs from july. I havent driven it since.

Thanks.

 

[Turbo Monk3y]

Don't aftermarket cams take away 10-15Psi across the board... it states that you have 272s in your head.... I forget...

 

[Kmiller86]

Well here are a few logs. You can see how messed up the logs get.

 

[Kmiller86]

I rechecked the valve timing and it is correct. So count that out.

Is it true that your compression can get lowered with different cams?

What do you think of the logs. Any ideas on what is happening?

Thanks

 

[90AWDTalon]

I think the lean spikes are caused by your injector duty cycles dropping. I don't know whats causing the duty cycle to drop, maybe a bad maf or a tuning issue.

 

[pneumo]

Is it true that your compression can get lowered with different cams?

Sort of. Big cams can lower the reading of a compression test since they have so much overlap, and a compression test is done at low rpm. The actual compression ratio doesn't change.

 

[project_tsi]

How many miles are on your new engine? If the engine isn't fully broken in yet, it won't give you as high as a number than if the engine was fully broken in. And when are you doing these comp tests? The engine needs to be hot and the throttle held open when your doing a comp test. I know for a fact that Andy's stroker puts out 190psi accross the boards w/ comp 200 cams with the intake advanced 4*. My stroker puts out 180 accross with comp 200's straight up.

 

[Kmiller86]

The engine was fully warmed up when i did the test. It has about 1200 miles on it.

The only thing i didnt do was hold the throttle wide open. Would it have made that big of a difference? Just curious. I will redo it this weekend.

Any other opinions on the logs?

Thanks

 

[andymoraitis]

The only thing i didnt do was hold the throttle wide open. Would it have made that big of a difference? Just curious. I will redo it this weekend.

Actually it will make a significant difference if the throttle plate isn't held open. I've seen as much as 15 psi less from not doing so. I'd re-run the comp test to get more accurate numbers.

FYI, my intake cam is advanced close to 5 degrees and not 4 as Dan previously mentioned. It's a bit aggressive, but the extra compression across all four makes a nice difference in off boost torque and transient boost response. As soon as I pick up some adjustable cam gears, I'll defnitely be dialing it back a bit.

I'll dig into those logs as soon as I have a chance but on a basic analysis I would suspect that something's up with the MAF as mentioned above. If you have the chance to swap it with a known working piece I would do so. It would also be a good idea to check the TPS for correct voltage.

 

[topstreet]

I am no expert when it comes to dsm link specifically but... A well tuned engine with 100psi of compression will hold 25psi to redline. It does not sound like there is 4" primary header pipes going to a Cat turbo or anything crazy like that.

Going back to the first post... I am slightly confused about this. During your boost leak tests, you say that it is dropping to 0 pretty quickly. Are you using a compressor for this? Every time I do a boost test, I go at the inlet of the turbo and watch line pressure compared to boost gauge pressure.

Eitherway, If you are testing at the throttle body and finding leaks this should give you some idea of what is going on. If you want to do some accurate tests, boost test the whole system from the turbo to the head. Remember that you are going to have a cylinder on its intake stroke. If you have a good amount of duration on you cams, you may actually leak out of the exhaust. This is why it is important to keep an eye on the line pressure too. Determine if you have any leaks and go from there.

If you are looking to see if the engine is sealing compression the correct way. Do the "on a budget" method of testing leak down. Take the tube off your compression tester and hook it up to the air line. KEEP IN MIND! You need the cylinder that you are working on to be at TDC with the valves closed. Put 120psi or so to it and listen for leaks. (Rad, dipstick, throttle body, tail pipe) If you dont have this right on TDC it is going to spin the motor over for you. Keep wrenches, cords, and you hands clear of anything that may move.

If these few checks on the piping system and engine come out looking good... Then at least you know.

Then the DSMLink guys can go to town.

Hope this helps,

Jake

 

[andymoraitis]

My stroker puts out 180 accross with comp 200's straight up.

Dan: Actually, your readings were at 170 across the board, which is still plenty healthy considering those cams may be off a bit. Mine were identical before the cam adjustment (170) and on the 2.0 with the same cams (unadjusted) she made 160 across.

Jake: Good stuff man!

 

[Kmiller86]

Ok thanks guys. The recheck will have to wait until this weekend. I will also do a cylinder leak down test as well.

Yes I was using an air compressor for the boost leak test. I did not watch line pressure compared to my boost gauge, I will give that a try as well.I originally had it on the inlet of the turbo and it wouldnt hold pressure. I did the good old soapy water test and found no leaks so I moved the test point to the throttle body.

I was also thinking a maf problem, the only thing that bothered me about that was I used it on my old set-up with no problems. Mabye it just went bad????

I just want to take care of all of these potential problems so I can take it to the track and get a slip then sell it.

Thanks

 

[topstreet]

I didnt even see this before, but... You are only alittle ways away from me. If you would like me to take a look with you then just let me know.

Jake

 

[KeltonDSMer]

I bet the boost leak is causing a very rich condition at high boost resulting in a misfire which would read as lean on a wideband from all of the uburned oxygen.

What is the A/F ratio as the car is spooling?