Guest bastaad525 Posted August 6, 2003 Share Posted August 6, 2003 I can't help but keep thinking, maybe the stumble I'm feeling with my new turbo engine, may be turbo lag. Can someone explain to me what exactly turbo lag feels like on a zx turbo engine? I know some people have said the stock T3 doesn't lag, which is why at first I was 100% convinced it was some kind of technical problem. Let's say you're cruising at a nice low 2000 RPM, what exactly SHOULD happen when you floor the throttle? With this engine, It stumbles really bad at first, like it would if you were running way too rich or way to retarded timing on an N/A motor. It struggles to get up to 2500 or so, then starts picking up, and at 3000 it just GOES. This stumbling is of course most notable whenever I leave a red light. It feels really bad to me, so much so that I still am not convinced that it is NOT some kind of problem. I dont generally make a habit of cruising at low rpms though now that I have a real exhaust and a working tach, I try to keep it around 2500-3000. Even then, when Im just cruising and the boost gauge shows vacuum, and suddenly I floor it, the car definately feels like it 'hiccups' before it starts pulling. I always figured you would definately be able to feel the transition from off boost to on boost, but should the motor actually bog and stumble like this? Quote Link to comment Share on other sites More sharing options...
yo2001 Posted August 6, 2003 Share Posted August 6, 2003 sound like you are getting lag. also probably getting too rich and no enough timing to burn the fuel properly. try little bit more timing and see what happen Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 6, 2003 Share Posted August 6, 2003 Already did that I advanced the timing as much as the '81 distributor would allow it's shaft to be rotated. From what I understand the '81 dizzy shaft can only be rotated as to allow about +/- 2* or so of advance/retard, so I guess I advanced it about 2*. To advance it any further I have to adjust the CAS... which I'm reluctant to do as I can't exactly figure out HOW to see where the timing is now and how much of an adjustment I'm making, as there's no mark on the crank pulley to go by, and I dont want to advance too much. If I AM running rich... wouldn't that be a blessing in disguise? In other words, would I be more able to increase the boost? I'm thinking of installing the Grainger boost controller soon, maybe tommorow, but keeping it at stock boost levels still. I want to do this because as I understand it the Grainger will help the turbo to spool faster, and everyone who uses one seems to agree on this. Maybe this will help with the stumble I'm feeling? my spark plugs aren't really giving a good indication of the fuel mixture, I pulled them again today, they still have the light grey ashy deposits, which I've been told was due to lead content in the racing fuel that the owner of the donor car used to run. The base of the insulator and the end of the threaded part have the darker powdery look that tells me I may be running a LITTLE rich. They definately do not look like they are running too lean, that much I know, and I"m glad for that. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted August 6, 2003 Share Posted August 6, 2003 Try closing your plugs up alittle to maybe .030 and see if that helps with the stumble. Also with the factory computer putting the foot to the floor doesn't get much response in the lower RPM's. Have the timing checked by someone with a light. You'll be glad you did if you tear soethign up while running to much timing. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 6, 2003 Share Posted August 6, 2003 It shouldn't stumble. But the causes are simple (ignition timing or mixture), it's finding the solutions that's the tough part. My car will not stumble when floored at a low rpm, but the "lag" is there if you can call it that. I call it "off-boost" response, and it just isn't good with a 7.4:1 compression engine. I've never dealt with an '81 with the separate CAS, or I'd try to help out with it. All I can say is you have to find out how to measure the ignition timing; there has to be reference marks on the damper. Turn the motor to TDC by hand, and just see what lines up. Once you know how much it's off, you can set it right. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 6, 2003 Share Posted August 6, 2003 I have a timing gun just gonna have to find and mark TDC myself then I'll check it. No pinging at WOT at 5500rpm so far. I'll regap the plugs... need to get my MSD hooked up also. Well, now I'm back to thinking it's not just turbo lag... took the car out and did a couple 0-60 runs with it. Figure, a stock zxt would run 0-60 in 6.9-7.2 seconds. I was only able to do it in 8.5, with 600 less pounds This was launching at 3000 rpm and shifting at 5500rpm, hitting 60 in 2nd gear at 5400rpm. And I know for sure my speedo is correct this time, I verified it with the transmission calculator java applet. I'm thinking I need to rev a whole lot higher and dump the clutch... at 3000, the tires would spin for about a half second, then the revs would drop down to 1500rpm and laaaaaaaaaaag until 3k. Very different from my N/A motor... dump the clutch on that any higher than 2.5k and the tires wont grab for all of 1st gear. Well... I gotta admit I'm a little dissapointed but I think if I found a better way to launch and avoid all that lag the car would have pulled a lot faster... definately feels torquier than my N/A once boost comes on. Any launching tips? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 6, 2003 Share Posted August 6, 2003 hmmm well we're gonna try to adjust the AFM one way or the other hopefully on friday I'll have some time. Will probably mess with the timing then too. Again... I'm also contemplating just going ahead and installing the Grainger boost controller but leaving it set at stock boost... supposed to help the turbo spool up faster. Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 6, 2003 Share Posted August 6, 2003 525 - you don't have an I.C. installed yet, right? If not, i dont think what you're experiencing is lag...because there's not much of it without an I.C. You mention race fuel that the guy before you, that owned the donor car, ran through it. This has me thinking. Did he race the car? Why was he running race fuel? Did you ever get a chance to do a compression check on this motor? My brain is working hard on your problem and i really want you to get it figured out. You've been so pumped up and excited about this Turbo swap and have posted about 3000 times in the last 2 months, i really wanted you, of all people, to have a good experience and get the real thrill of a T3 strapped on an L28...and it just aint happenin! Hopefully it's just a timing issue. We'll keep working on it..from a distance. Wish you lived closer to Jersey...damn. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted August 6, 2003 Share Posted August 6, 2003 Do you see black smoke coming out of the tail pipe when the stumbling happens? If it is rich enough to stumble, then it is rich enough to see black smoke. I would start by simply cleaning the connection at the ecu with brake clean. Spray the connectors too. See if that helps. Verify your timing, but you should not have to regap the plugs if you are not running an intercooler. make sure you have good wires, cap and rotor. You also need to check for a leak somewhere in your intake plumbing, and verify your fuel pressure it right. I had a car that had a leak in the intake tract, actually the turbo, and it stumbled badly when you got about 0 on the boost gauge, but would eventually clear out and run. Make sure you don't have any leaks. You should not have that much lag with the stock turbo. One of the things you can do is plug the nipple on the turbo that is giving the waste gate actuator its signal, and route it from the intake instead. It makes a difference. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 6, 2003 Share Posted August 6, 2003 yeah I've been looking for leaks on a daily basis. I've already found and elliminated (sp?) two major ones. The boot from AFM to Turbo was cracked really bad where it connected to the turbo, replaced that. Inspected the new one closely before putting it on, especially on the 'bellows' shaped area... no cracks that I can see. Also, the hose running from valve cover to that same boot was cracked really bad at the valve cover. Removed it completely, vented the valve cover with a K&N filter, and used the open port on the boot to route my BOV back to. I've checked and tripple checked the connection of the J pipe and it's on there snug. All the little vacuum hoses off the manifold are good. I have seen NO black smoke or any smoke for that matter, after I recirculated the BOV. I will test it again to be sure maybe I just wasn't watching good enough. As to why the previous owner was running race gas... I dont know, the car was bought thru a 3rd party. I did see the donor car, it looked like it was being prepped for racing, but as I understand it it never got finished. Compression checked out good, and the car starts right up every time so I don't think the motor is having any problems. Plus, it ran PERFECTLY before the swap.... Nope, no IC yet. Can you guys tell me what is a good way to launch a turbo? Obviously it's gonna take a bit different technique from what I'm used to. I still feel the car would have pulled much faster if I could get it launched on boost... wish I'd put an automatic in there then I could brake torque or whatever it's called where you can build boost at a standstill. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 6, 2003 Share Posted August 6, 2003 UPDATE!!! I went and did the timing right now. Found and marked TDC, and checked it. 10* BTDC. Supposed to be 20 right? So that explains part of it. I adjusted the dizzy and the crank angle sensor as far as they both will go, was able to get it up to 16-18. Drove the car, feels a bit better, still a little stumble. I figure it's the remaining 2-4* would probably even that the rest of the way out. I could turn the adjusting bolt on the crank sensor more, but if I do, when I start the car I get this horrid metallic rapping sound... nooooo idea what the hell it is. Dont have any more time to play with it today.... Plus, when I pulled all the spark plugs to make it easy to rotate the crank, I found that #'s 1-5 all looked perfect, but the #6?? BLECH!!! SUPER SUPER rich black powder on it!! So I'm thinking... either #6 cylinders valves are out of adjustment (I dont hear any valve tap above the usual though) or the #6 injector is sticking open?? What do you guys think?? I know what I think I think... I figure out whatever is wrong with cyl#6, and figure out how I can adjust the timing more, and I'll have a perfect running turbo motor Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted August 6, 2003 Share Posted August 6, 2003 Sounds like your certainly on the way Quote Link to comment Share on other sites More sharing options...
TimZ Posted August 7, 2003 Share Posted August 7, 2003 Also, the hose running from valve cover to that same boot was cracked really bad at the valve cover. Removed it completely, vented the valve cover with a K&N filter, and used the open port on the boot to route my BOV back to. As I recall, the valve cover vent should not be vented to atmosphere - this should be causing a vacuum leak. Both the BOV and the valve cover vent need to be plumbed in after the AFM. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 7, 2003 Share Posted August 7, 2003 hmmm... I do notice a lot of Z's with this same breather filter on their valve covers, I dont think so many would put it on there if it caused problems. I did note the idle before and after and it didn't raise as it would if it were a vacuum leak. From what I understand there is never vacuum present there, rather, the vacuum from the intake sucks any blow by air from there. I'll look more into this. I used to think this would create a vacuum also, because I know that removing the oil cap causes a vacuum leak, but then I thought about it and realized this only ever does/should happen when the valve cover is vented to the intake as it's supposed to be. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 7, 2003 Share Posted August 7, 2003 hmmm... I do notice a lot of Z's with this same breather filter on their valve covers, I dont think so many would put it on there if it caused problems. I did note the idle before and after and it didn't raise as it would if it were a vacuum leak. From what I understand there is never vacuum present there, rather, the vacuum from the intake sucks any blow by air from there. I'll look more into this. I used to think this would create a vacuum also, because I know that removing the oil cap causes a vacuum leak, but then I thought about it and realized this only ever does/should happen when the valve cover is vented to the intake as it's supposed to be. You are forgetting the other half of the equation - the PCV valve. It is plumbed into the block. If you unseal your valve cover, you create a huge vacuum leak. If you are going to remove the valve cover hose and vent it, vent the block where the PCV hose goes as well, and plug the hole in the intake manifold where the PCV valve used to be. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 7, 2003 Share Posted August 7, 2003 no kidding... you're right I had never even considered that. To be honest with you I'm not even sure there IS a PCV valve on this motor... I haven't seen it... not even sure where it is The other thing I had considered was just capping the valve cover instead of the K&N, but this is bad too right? Hmmmmm... well if I remember, on my ZX the PCV valve is screwed into the bottom of the intake manifold close to the rear of the engine bay, right? Same place on the turbo motor? I'll find it tommorow and do as you suggest, though, I have no other filter to stick on the crankcase vent. Maybe I'll find an alternate way to route the valve cover to the intake. Maybe this is yet more cause behind the hesitation I'm feeling? Again I did note the idle before and after and it didn't go up as it usually does when you create a vacuum leak... maybe someone already plugged the PCV? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 7, 2003 Share Posted August 7, 2003 Okay wait a second now I'm really confused, about venting the valve cover creating a vacuum leak. Consider this: on my N/A engine, which was equipped with SU's, and for that matter, any stock SU carbed Z engine, the valve cover is vented into the air filter housing. And of course, the air filter housing is open to air, and at idle isn't really subject to any strong vacuum. I also know a few guys that run the open K&N filters and filter boxes, and since these provide no port for the valve cover vent, they just cap that off with a K&N also, but I'm positive they still have their PCV in place. Even on the turbo, the valve cover vents into the intake before the throttle body, whereas all the vacuum is present AFTER the throttle body, is it not? When the throttle plate is closed, everything before the TB is pretty much open to air, with very little pressure there one way or the other... which means the air coming in from the valve cover could easily escape out the thru the air filter (maybe not so easily with the air flow meter closed) and thus creating a 'leak'. If the valve cover was vented into the intake after the TB and was part of the 'pressurized' part of the system, I could see just venting this to atmosphere causing a leak, but as it is I can't really understand how it does. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 7, 2003 Share Posted August 7, 2003 Reading the Haynes manual right now... I THINK I'm starting to understand how this would create a leak... kinda... not really... a little Okay let me ask this, if I pull the K&N breather off the valve cover, and put my thumb over the opening, should I feel vacuum there or no? And secondly, IS there a problem with just capping off the valve cover instead of venting it, if I decide I want to leave my PCV valve hooked up and in place? And one more question, the most important one I think. As I said, I ran a hose from the BOV, to the port on the afm-turbo boot, where the valve cover had originally been vented too. The other two ports on the afm-turbo boot are very small and would be kinda hard to use for either purpose. Could I run a hose from the larger port on the afm-turbo boot, put a large T there, and run one end of the tee to the BOV, and the other end to the valve cover? To tell the truth, the tee is already in place between the BOV and the boot, but I capped off the third opening. I was oringally planning on routing the connections this way but wasn't sure if having the BOV and valve cover vent teed together like this could cause any problems with the air going from BOV to Valve cover instead of into the intake as it should and therefore causing a rich condition. This is gonna drive me nuts...... Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 7, 2003 Share Posted August 7, 2003 At idle you will probably feel a vacuum, as the motor is pulling air from the crankcase via the PCV valve, and yes you have one mounted on the underside of the intake manifold. And you cannot compare the PCV system with a carburated system, as electronic fuel injection measures the air with a sensor, and fires the injectors appropriately. In a carbureted system, as long as all the air goes through the carb, you will be ok. If you cap the valve cover, under non-vacuum conditions the blowby has no place to vent, and you may puke oil out valve cover gaskets and other strange places. Not recommended. I suggest keeping your valve cover vented to the same place it was originally; it's too small for the BOV. If your BOV doesn't leak (it may though), just vent it to atmosphere until you can plumb it right. I built myself a custom intake pipe out of exhaust tubing, with all the right fittings for a fuel cannister vent, valve cover vent and recirculation of my BOV. Find out what others have done, as most will recirculate the BOV with stock EFI. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 7, 2003 Share Posted August 7, 2003 yeah I was gonna just leave the BOV open to atmosphere but it leaks big time at idle and was causing all kinds of problems that way. It's a 1g dsm... I guess I have to 'crush' the cap as so many other people have done with this BOV, to help keep it closed. I still prefer to leave it recirculated. I've been mulling over this all night... I dont see why I shouldn't be able to vent the BOV and the valve cover into the same port. Either way, it's air that has already been metered by the afm, and either way it will end up in the intake manifold. Now would be a good time to check the PCV to see it's working right, also. Another thing I'm going to do soon is get one of the afm-turbo boots that Jersey got, I think it's off the 2g dsm. Looked the same as the Z one but smaller, made more room for the afm, and had a port on it already for the BOV. Quote Link to comment Share on other sites More sharing options...
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