Dyno results... whaaaaaaaaaaaa? (long)

[Guest bastaad525]

For the first time ever I have gone to the dyno to test my car and come back not the least bit happy . Things did NOT go nearly as expected, and it ended up almost being a total waste of money. I really only got in one complete run...

 

Having gotten some advice from a few other guys on this board, I finally decided to say what the heck and crank the boost up a little bit... 12 seemed to be a common, average number that guys have run on bone stock EFI'd, intercooled T3 setups without having problems. I had been running about 8.5psi since installing the I/C, but figured, hey, if these guys can run 12, so can I. So I set it to where it would spike to about 14 and then settle at 11-12, and got it on the dyno.

 

First run was a bust, the guy pulled to about 4500rpm, it was pulling nice and steady, with a nice 12:1 fuel curve, and suddenly it just JUMPED way lean, off the chart lean, the chart reading as high as 18:1. I mean it just shot straight up, so the guy let off immediately. There was no sign of ping, by the way, and no sign on the power graph of a sudden super lean condition either... no drop off in power (or power spike for that matter), no suddenly erratic curve. Torque was up a LOT over my last dyno w/o the I/C, in the 280lbft range... hp was lower but that's because he didn't pull up to it's peak.

 

 

So... I figured... okay my car aint gonna run that much boost I guess, so I go and crank it back down. On the next run, it only goes up to about 8 psi, with a 10psi spike, and this time goes lean even sooner!!! At about 3500rpm, the A/F just skyrockets lean, again going off the chart.... okay??? Again no ping, no sign of anything that would make you think fuel just cut out like that.

 

Third run, I decide to switch the boost controller to get it's signal from the manifold instead of the turbo, which I'd tested a couple of days ago and helped greatly with the boost spiking (a long story, see my other thread here for the details: http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=36058 ). He goes to do another pull, but notices he's getting no reading from the wideband O2 sensor (bosch wideband, tailpipe sniffer). He checks a few things, but it doesn't come back on. He starts to say something like "oh my car must be messing it up somehow"... this shop was a Corvette only place, nothing but new Z06's parked out front... and he makes some comment about my car not running 'as clean as a Vette... it must be damaging the sensor'. Double .

 

So he goes and makes a phone call, comes back and does something on the computer and then he's getting a reading again. So he goes for a third pull. This time boost is back up a bit, now that it's reading from the manifold, it hits about 11psi, but no dice, at 3500rpm it shoots super lean yet again. He stays on it a little longer this time, up to about 4000, to see what happens. Again, not one ping, and the power graph is relatively smooth. At the end of the pull, we noticed that the A/F ratio had just dipped back down onto the chart.

 

We talk a bit more, and agree that, with no sign of ping, either audible or on the graph, maybe he should just take it all the way up and see what happens. He offers to do one more pull and not charge me for it. I crank the boost back down to where I had been running it before, which got me about 8.5psi, when it was hooked up to the turbo instead of the manifold. In retrospect I should have turned it even lower this would have answered some questions, I think. Well anyways, he goes to do another pull, and again his O2 isn't working. Back in the office, another phone call, and he comes out and fiddles with some other stuff... no dice. He sits and waits and about 5 minutes later it comes back on.

 

So... one more pull, this time we agree up to 5000rpm, no matter what the fuel curve says, unless we hear some ping. As this was the only full length run, this was the only one I asked for the printout of... here it is:

 

 

Boost hit about 9-10psi in this run. Fuel curve still going WAY lean at about 3500rpm. Oh by the way, timing is set to stock, 20 degs, and I didn't fiddle with it during the testing. You'd think 210rwhp and 269lbft or torque (!!!!!!!) would be a great reason to be happy, but with that fuel curve I'm scared to drive the car that way. Again, NO sign of ping whatsoever. Oh for what it's worth he did all of the pulls in fourth gear, so they were taking a while... the engine being under load for that long, running from 15-18:1 A/F ratio, how the heck wasn't it pinging???? Why isn't there any real sign of a sudden lean mixture like that? I would think, at 15-18:1, you'd see a HUGE dip in power, but the torque curve just falls off as gently as it always has when I"ve dynoed it. For comparison, here was one of my first dyno pulls, before the I/C:

 

 

So... I'm stumped. I wanted to think this was some kind of problem with his O2 sensor, and part of me still does, but then I remembered this thread: http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=32872&highlight=injectors

 

Almost the exact same story. If you check that link he also has a pic of his dyno graph, and it shows that as he went up above about 10psi, it just goes SUPER lean off the chart. Even more odd of a parralel, is that if you read the first post and then look at the graph, the green line was when he set the boost the highest (15psi) and oddly, just like mine, it goes lean at about 4000rpm, but then when he turns the boost down, it starts going lean EARLIER instead of later!!!

 

 

 

 

So... I don't think this was a problem with the shops O2 sensor. And I find it hard to believe it's something wrong with my EFI... the car feels like it's running great, and when the shop guy did the pulls he said it didn't feel to him like it was suddenly leaning out at all. And if it WERE something wrong with my car, why did someone else have the exact same experience as me? More funny stuff... in that same thread, he claims that though he was pinging at 12psi on the dyno, he discovered after leaving that his dizzy was fully advanced. He backed it off a bit (GAWD I wish he'd actually checked with a timing light to see what it was set to before and after) and the ping went away and he said he ran 12psi with no problems after that. Jersey, Cygnus, and a few other guys have also stated they've run 12psi intercooled on bone stock EFI with no problems, Jersey as high as 14 with no pinging at all. Well... if my dyno, and the dyno in the link I posted are any indication, then a typical stock setup should be running super lean at that point, and no motor should be able to put up with that for very long. I mean come on... 18:1 A/F ratio?!?!?!?! How on earth was it not pinging???? And please don't say "well it was probably inaudible ping" because it still would have shown up on the power graph... my N/A Z used to ping a bit at high rpm, WOT, and it showed up very visibly on the dyno chart.

 

 

So... I am stumped, confused, and 100% baffled. I have the car set back to 8psi, but even at that I'm worried that maybe I'm doing harm... I may just pull the boost controller out. I dont see why I should be limited to such low boost. I kinda wish I'd just followed by example, stuck with 12psi, and never went to the dyno at all. I seriously have no indication that my car is doing anything different than so many other guys on here, as a matter of fact, it seems to be mirroring many others' experiences perfectly. My first dyno pulls were VERY typical looking in both power and A/F ratio, compared to every other similiar setup I had seen tested. Now I'm again getting similiar results as at least one other person, unfortunately his was the only posted dyno test I was able to find with a relatively close setup to mine.

 

*sigh* so now what? I'm out of cash, so more fuel is out of reach for now... I'm gonna be pissed if I gotta leave it at 8psi... that means I'm actually making LESS power after the I/C than before....

[Guest bastaad525]

Notice also, on that link I posted with the other guys dyno, that even at the stock boost setting, hitting only 190rwhp and 220ft lbs of torque (the lighter pair of the dark blue lines), he was STILL going way lean, 13:1 AFR by 5000rpm, and 16:1 by about 5700rpm.

 

 

Time for some more 's

 

So stock EFI isn't even good for stock boost levels once you throw an I/C in the mix or what????

[Bernardd]

z31 ecu swap time????? You can use a 88 maxima ecu if you reprogram it as well. I've seen turbo ecu's go for 35 dollars. The maf's are cheap and then all you need is the Cas. I would think you could get something together for 100 dollars or so to ensure safe boost.

Bernard

[Tim240z]

Seems like the guys O2 equipment is not reliable. Having those problems that you were having on your runs I would not put a whole lot of stock in his A/F data.....

 

Tim

[johnc]

Next time try Superior Automotive in Anaheim: http://www.superiorautomotive.com

[Guest Cronic]

I dunno what everyone else thinks about this, but that guy's wideband is FUBAR. if your car were to lean out too bad, it would yank timing like no other, and the car wouldnearly DIE on the dyno. I've done it before, and the car all but stops from the amount of timing the ecu pulls from the ignition.

 

If you were running that lean, you'd know it. Get a cheap narrow band a/f guage, and you can get a reference for how lean you are. you should always see green from a WOT pass at 10psi. I did. Hell even at 15psi, I always ran green until about 4500rpm where it would dip yellow.

 

On the dyno I had an 11.5:1 a/f until about 4500rpm where it hit about 14:1.

[clint78z]

Run a wire tap from your O2 wire to a voltmeter, if it stays above .45v it should be a good indication that your A/F wasn't 18:1. The cicrumstanses seem a little fishy to trust the wideband.

[yo2001]

I would check for IC piping leak.

 

Other than that, running leaner on IC'ed air (denser) makes since to me.

[fl327]

Get a better dyno spot to run those tests, sounds like they suck.

[COZY Z COLE]

QUOTE " this shop was a Corvette only place, nothing but new Z06's parked out front... and he makes some comment about my car not running 'as clean as a Vette... it must be damaging the sensor'. Double . "

 

My .02 cents, first of all if somebody reccomended this shop to you they should be slapped!!! Something is happening to your engine at 2800 rpm's and if the a/f is to believed(????) there is an internal vacumn leak like around your intake manifold, ect. I'd do a complete vacumn check. As to not hearing pinging, that doesn't mean anything. A engine should be shut down with the a/f readings your chart indicates. Too bad you didn't pull the plugs after your run to check for oil deposits to see if you were really running that lean because of a vacumn leak. Any competent operator would have stopped the runs, told you what to check, and let you fix it and come back and charged you accordingly. This has been my exp.

 

LARRY

[Guest bastaad525]

Yeah I'm figuring on re-dynoing soon... definately will wait this time though until I can add more fuel as needed before going, will try to pick up an FPR this week. And this time really try to tune it instead of just for informative reasons. I wouldn't go back to the same place anyways... he was way too far.

 

I really want to believe it was an issue with his O2 sensor, but again, and for anyone who didn't follow the link above, here is the scan of of member DAT240Z's very similiar dyno sheet:

 

 

Now if I read his post correctly, then on this chart, the lighter blue line was at STOCK boost, got 190hp/217lbft, and leaned out pretty badly by 6000rpm. The dark blue lines were at 10psi, and just like mine you can see him go super lean right before 3500rpm, and the guy let off at about 4700. His best run was the green lines, which was at 15psi, and it actually leaned out LATER than at 10psi, at about 4000rpm it starts to lean out, but not as dramatically as at 10psi. It also richens back up a bit, back onto the chart, at around 4500rpm, just like mine!! And no, this guy didnt' test at the same dyno as me ! But it's very odd how he got nearly the exact same results. I've searched and searched but haven't found any other dyno's of people with similiar setups to compare to.

 

So that kinda makes me think it was not, in fact, a problem with his O2, as much as I would love to believe that. The second thing is, this wasn't the usual kind of dyno I've been to before, which were usually little hole in the wall places run by 'kids' with a line of hondas and acuras outside waiting to be tested. This place was NICE, and was ONLY Corvettes outside, I mean only NEW Vette's, most of them Z06's, most of them highly modified. It was a BIG place as well, with like 8 bays for working on the cars. The waiting room was nicer than any doctors office I've ever been too and even had a bowflex set up there. This guy obviously caters to some well off clientelle... I'm sure he does lots of dyno testing and tuning, I find it hard to believe his equipment would be faulty like that, as much as I'd like to.

 

Yo2001 - I've checked for leaks like 20 times, but anyways, wouldn't a leak make me rich instead of lean? A leak under boost = boost escaping = less air in intake than AFM has measured = running rich. Running leaner on intercooled air makes sense to me too but THAT much leaner???? Even more odd is when you get on it it definately SMELLS rich from the exhaust... though I know that's not a great indicator of anything.

 

I've been very interested in doing a Z31 swap, it's a bit more complex for me as I have an '81 dizzy ('blank' dizzy) so would need to swap out to a '82-'83 dizzy as well. The cost isn't too bad, I've priced it at around $300-ish from my used part sources for everything I need, but I dont' trust myself to get it installed and running well. I'm going to try going with an adj. FPR, or, if that wont get my fuel curve safe, then I'll go with bigger injectors. Enough guys here have run 370's on stock EFI with great results and more than enough fuel to support more than the stock T3 can dish out.

 

 

Cronic - how would the EFI know to yank timing under lean conditions like that? I thought the O2 sensor was not functional at WOT, heavy load circumstances? I'm not running the knock sensor, so even if it had knocked the EFI wouldn't know about it to pull timing. I dont think the EFI would have any way to know or compensate... otherwise how is it that so many people have blown their motors running stock EFI and just a bit too much boost

[ToplessZ]

Speaking of leaks you did have your intercooler leak tested before going through all the trouble of hooking it up right. You should not be forced to run near stock boost after adding the intercooler. I recommend joining me in the 300zx ecu swap path. Im sourcing the parts right now.

[rags]

Do I have this backwards? I thought if you had a leak in your intercooler plumbing or somewhere along the intake tract, you would go pig rich under boost because the engine isn't getting all the air that the AFM is accounting for.

 

Joe

[cygnusx1]

Bast. well I know it would be nice to be able to blame the dynos O2 sensor but I know what you mean. It's an uneasy feeling. The only thing you can do is to test at another dyno to compare data. I wonder if your AFM spring is too tight and causes the lean conditions at the mid rpms. The fuel started to come back in at the higher rpms, possibly as the ECU was mapping around the AFM at that point. It could be. You can also try the resistor mod on the temp sensor circuit. I know there is a thread about that somewhere. It will move your entire fuel map richer (I hear). One thing we can say is that your injectors and fuel supply are NOT the limiting factors at 3500rpms; its the fuel map thats lean. Yes, I continue to weekend drive my Z at 13-14psi limiting myself to 5300 or so rpms. For those that are reading... It's a a stock 83 EFI, Walbro Pump, good I/C, TO4B Hybrid, and the FMU (fuel pressure 45psi reached at full boost). Food for thought. Historically the ZX Turbo motors are very tough and have been known to tolerate the evils we do to them. Therfore, it is difficult to tell when we have gone overboard without the proper diagnostic tools.

 

DISCALIMER: I dont have any clue what my fuel curve looks like. It just runs good.

[COZY Z COLE]

Do I have this backwards? I thought if you had a leak in your intercooler plumbing or somewhere along the intake tract' date=' you would go pig rich under boost because the engine isn't getting all the air that the AFM is accounting for.

 

Joe[/quote']

 

This may help you..... LARRY

 

http://www.babcox.com/editorial/cm/cm120230.htm

 

"If the air/fuel ratio has too much air and not enough fuel (a "lean" mixture), it might not ignite at all - causing a loss of power and a big increase in unburned HC in the exhaust. This is called "lean misfire" and may be caused by dirty or clogged fuel injectors, low fuel pressure or an air or vacuum leak in the intake manifold."

[Guest bastaad525]

Do I have this backwards? I thought if you had a leak in your intercooler plumbing or somewhere along the intake tract' date=' you would go pig rich under boost because the engine isn't getting all the air that the AFM is accounting for.

 

Joe[/quote']

 

 

that's what I said if there is any leak, one that would cause a lean condition, it would only be between the turbo and the AFM. I"ll be pulling that rubber hose maybe today and inspect it for cracks. Otherwise I dont suspect any leaks in the I/C, pipes, or manifold.

 

My AFM spring is turned just a tad bit tighter than the stock setting, two gear teeth tight. I dont think this is the cause of the problem either. The first two times I dynoed, I was running pig rich in the midrange, and leaning out on top. The first time I dynoed, the AFM was set stock, the second time, was after I tightened the spring. The effect on the fuel curve was very minimal. I was trying to correct the super rich midrange, and also to lean out the idle and low throttle around town mixture, where it tends to run a bit rich as well.

 

I still dont get why it was going leaner, SOONER, after turning the boost DOWN. None of this makes any sense, but the fact that someone else had the exact same results as me makes it even weirder. And I still dont get how in the heck my car was nailing leaner than 18:1 A/F ratio at some 12-14psi of boost, under load all the way up to 5000rpm, and not ONE ping.

 

Regardless, I will most likely install an adjustable or a rising rate FPR by the weekend, will turn up the pressure, and will TRY to get back to a dyno... not that dyno though ASAP

[cygnusx1]

On the leak thing....

 

Under vacuum, a leak would suck un-metered air in and cause lean.

Under boost, a leak would let metered air out and cause rich.

 

So if you are idling lean and going rich under light boost then I would say you have a leak.

 

Does this sound right? I think it is correct.

[Guest bastaad525]

yeah and it's the opposite of what's happening to me... I'm running rich under vacuum and lean under boost.

[johnc]

this shop was a Corvette only place, nothing but new Z06's parked out front... and he makes some comment about my car not running 'as clean as a Vette... it must be damaging the sensor'

 

BTW... A/F and O2 sensor's don't get "damaged" from a few runs by a dirty car. On my engine I ran a 3 wire O2 sensor for two years while running 112 octane leaded fuel. Sensor worked just fine.

[yo2001]

Not if the leaks at the charge pipe.

 

Yeah, you guys are right, I/C leak will make it run richer. AFM does go WOT under boost though. So the ECU pretty much relies on rpm signal only.