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My 924 Turbo, data logging AFRs
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CÚdric  



Joined: 27 Aug 2004
Posts: 1869
Location: Sweden

PostPosted: Mon May 20, 2019 9:14 pm    Post subject: Reply with quote

So, i had a severe misfire issue which actually almost got me halted. I really didnt have time to sort the issue so i threw in a new coil and ignition amplifier since i knew those two were older than me. It seems to run great now, so I went out to do some logging with 1 bar boost again, now without misfires.

I didnt really have a lot of time so unfortunately the data below have maybe to few runs behind it to be certain. But it looks fairly similar to what I could see in the logs and on the display (though running 1 bar limits the time you can take your eyes of road). There were a few occasions where it dipped down to AFR9,8, which really is crazy rich, im surprised it even wants to run at those AFRs, it does seem to lean out very quickly at the top end where the AFRs are actually fairly reasonable. Its interesting to see how the airflow characteristics have changed with the IC and turbo change, before AFR were flat up until redline, but even at stock boost its now have this really rich midrange. A combination of the even inlet temperatures that the IC provides compared to no IC, and the airflow characteristics of the new compressor, with the non linearity of the flap system as a tricky layer on top of all this. They were quite finely tune as std these engines, with every CIS component in tune.

My biggest issue is that I got some flickers on the knock light, not sure it its false or real knock, it could be a sensitivity with the much higher cylinder pressures. I will have to fiddle a bit and see what i can come up with. I really should put in my knock control device, I think it also have output for head phones, which would be helpful.

Not sure where to go with the WUR, i will firstly try to limit boost enrichment a bit and see how it runs, then I will lay up a plan on how to deal with it long term, there are many alternatives, from very low tech to high tech solutions

I couldnt resist anymore, ordered a set of 7x16" Fuchs replicas, just have to decide on what tyres to use for the best fit and grip. Will have a wheel clearance soon, my BBS wheels, cookie cutters and some more wheels will have to go to get some money back and more space in the garage, and maybe a set of 6"+7" D90 if I could possibly find anyone interested in those.
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CÚdric  



Joined: 27 Aug 2004
Posts: 1869
Location: Sweden

PostPosted: Tue May 21, 2019 3:50 am    Post subject: Reply with quote


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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1752
Location: MI

PostPosted: Wed May 22, 2019 2:32 am    Post subject: Reply with quote

Do you have your boost sensor pre-TB so it never sees vacuum and your chart in psia?
That would explain the very lean readings at 1.000 where your engine is actually in high vac overrun but the sensor still sees atmo pressure..

I really doubt you are actually that lean in throttle (cause it wouldn't run at all) so all that stuff in the top right looks like overrun up to the 1.143 in the 4ks might be reading that little bit of pressure at overrun from compressor surge or whatever the BOV can't get rid of fast enough on overrun..

I think this is making your logs impossible to get good data from and you should put your sensor post-TB so you get boost/vac readings so everything where you are actually in vac isn't skewing the data on your chart at 1.000 and slightly above which is probably residual intake pressure after you have closed your throttle.
Even part throttle you will see boost pre-TB when you are actually in vac post-TB therefore the data is wrong..
For example, if you are cruising at like .5-.9 Bar psia post-TB/MAP you will still read 1.xxx bar psia pre-TB because your turbo is trying to push air through your almost closed TB..

I think your data on that log chart is quite useless and you shouldn't use it to tune until you get good data.. You need to log with your pressure sensor post-TB, MAP sensor style, so you are logging what you are actually running, and not whatever pressure is in your charge piping..
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CÚdric  



Joined: 27 Aug 2004
Posts: 1869
Location: Sweden

PostPosted: Wed May 22, 2019 4:03 am    Post subject: Reply with quote

You're right about the low load stuff, I wrote about it before earlier in the thread, any low load data here is not relevant. And since it cruises around stoich there is little reason to adjust anything, i keep good track on the low loads during driving. Anything in the plot from 1.5 and above is full throttle(which is the area that im interested in) , i was either cruising or hammering for the sake of logs. Though i will move the boost sensor pretty soon as i will prepare for next run with some other fiddling on the way to lean it out a bit.
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Fasteddie313  



Joined: 29 Sep 2013
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PostPosted: Thu May 23, 2019 3:21 am    Post subject: Reply with quote

CÚdric wrote:
There were a few occasions where it dipped down to AFR9,8, which really is crazy rich, im surprised it even wants to run at those AFRs, it does seem to lean out very quickly at the top end where the AFRs are actually fairly reasonable.


These occasions where it dipped into the 9's are at 1.9 bar psia at 1026rpm, 2053rpm, 2395rpm, and 3079rpm..

Now, how did you possibly have almost 1 bar of boost at 1026 rpm? Or even up to 2395 rpm? Can you even build .9bar at 3079?
This data looks unrealistic and therefore is probably also caused by pressure in the charge tubes that is not in the intake, probably when you dropped your throttle and it looks like your BOV didn't open very well to fill those boxes..
I doubt you could fill those boxes at all with a good MAP reading..

CÚdric wrote:
Its interesting to see how the airflow characteristics have changed with the IC and turbo change, before AFR were flat up until redline


Few reasons I can think of..
1. when you drop your throttle you have a lot more potential energy stored in your charge tubes now because they now have MUCH more volume, and are at a higher pressure than ever so you have a huge amount more energy to get rid of because of the increased volume and pressure..

2. Not only have you created more work for your BOV to equalize this pressure, due to the new higher pressure and volume, now you have a much smaller and less efficient BOV. The original BOV was huge overkill for it's job and superior to the new one with an even harder job.

3. You have a bigger turbo compressor now too.. You get that thing spooled up and it is also going to have more energy stored than your older smaller compressor due to momentum. So when you drop your throttle you are asking your BOV to equalize even more air now that that compressor is still pumping until it spins down..

The things that would skew the data on your charts are greatly amplified with your new system..

Is 2.0 bar psia as high as your chart/sensor/logging setup will go? If you are actually running at 2.0 I bet you have spikes higher than that when you drop throttle off full boost.. It just has to..
Your data is going to include pressure spikes from throttle drops all the way up to and through 2.0 and corresponding decel coming back down through them in decel, so your entire chart is tainted..

I would contend that all your data at higher pressure than 1.5 and below 3k rpm is false readings, unrealistic data, likely all overrun, you probably can't even build that boost there if you tried, which especially includes all of your 9.xx AFRs you are concerned about..
(your chart is upside down, if I say "below 3krpm" it's actually UP on your chart, or if I say "above 1.5 psia" it is actually down on your chart.. So it's hard to choose words to describe it correctly)
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CÚdric  



Joined: 27 Aug 2004
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Location: Sweden

PostPosted: Thu May 23, 2019 5:23 am    Post subject: Reply with quote

Relax , i have a pretty good feeling of how the logs look like, this is just a quick summary of several runs. I do look at the transient logs aswell, the 9,60-10 AFR comes just as i hit max boost at low rpms, then it jumps back up to 10,2 something a couple of rpms later, It was repeatable.

I had quite some signal issues this time, thats why you see some outliers, obviously i dont have boost at those rpms. Theres very little boost spike when i let of the gas, almost impossible to see in the logs actually, so the BOV does what it should. The boost controller also works ver well, theres almost no data at all above 2, so didnt mind taking that in.


Not sure why i dont get as good speed signal, it works well for a while and then drops out and then resumes a second later., or freezes I didnt have that with the old ignition parts when they were working. Maybe its something in the ignition system that still isnt working 100%. Could not feel anything in the car though, or maybe the innovate is on its way out

I wished i could filter out points where it only have like 1 or two data points, but i can at least mark them with colours, red is almost no data, green is alot of data. Here it is but for several sessions added. Wish there was more customization properties in the software in general.



For next time out the line is already moved post TB as I rerouted everything to include a pressure regulator to the WUR, to control boost that it receives, which will be interesting to see how easy it is to limit boost enrichment. But i will mostly go for full boost only so wont make big of a difference in the interesting range.
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CÚdric  



Joined: 27 Aug 2004
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Location: Sweden

PostPosted: Wed May 29, 2019 4:28 am    Post subject: Reply with quote

It seems that i adjusted the boost enrochement limiting knob the wrong way, hence didn't see anything different.so last time logging was a bit wasteful, even though accelerating on country roads is fun anyway. Its pretty quick at 1 bar! It also seems like i roasted my o2 sensor, i hope its wiring issues

Got my maxilite fuchs aswell, though two of them had some paint issues,so they sent out new ones and a courrier to pick the old ones up. Great customer service. It will be tricky to get a good fit, much harder than the cookies due to the added diameter. Well see what tyres i can find to make i work.

Same as last time, my rpm signal is on the way out, it was even more shaky this tim. Green and blue cells have pretty good data. Its so rich my o2 sensor and tailpipe looks like it from an ancient diesel, all covered in carbon :/ really need to lean it out..



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CÚdric  



Joined: 27 Aug 2004
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PostPosted: Sat Jun 01, 2019 11:23 pm    Post subject: Reply with quote

Went for a ride with my oldest boy today (4,5 years), he loves numbers and maths, so he gave me constant info on the AFR numbers, very practical I forgot to hook up the boost line to the WUR, which also happened to solve all my problems(the engine overfueling), the AFR curve is now nice and good. I would like a tad more at max power, instead but its a good compromise. So maybe im finished with fuel tuning now. To bad my O2 sensor went out again, changed earth point aswell, but that didnt cure the rpm drop outs

Power comes on pretty hard now when i leaned it out, 225 toyo T1Rs in the rear have no chance in 2nd gear when you push out of the corners. Might explore that further next time when Im without kids in the car

It wasnt the most obvious solution, but did solve my problems. To bad my O2 sensor is failing on me, need just some more verification to be sure it works at longer pulls etc.


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CÚdric  



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PostPosted: Wed Jun 05, 2019 5:26 am    Post subject: Reply with quote

New r comp track tyres are in, a tad wide for 8 inch wheels, but ive seen it work well on a 944 s2, so should work well on my car aswell. Even though it wont utilize the 245 fully it will be a big step up from my 205s, will be needed to put the new power down I got them for a nice price, otherwise i would have bought 225s.


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Fasteddie313  



Joined: 29 Sep 2013
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PostPosted: Thu Jul 25, 2019 2:46 am    Post subject: Reply with quote

CÚdric wrote:
the 9,60-10 AFR comes just as i hit max boost at low rpms, then it jumps back up to 10,2 something a couple of rpms later, It was repeatable.


Mine does this too..
Maybe it is airplate overswing that we are seeing and the slight backswing when the amount of air rushing in starts to stabilize?



I think mine is doing this more from a drastic change in TPS.. If I slap the throttle from about anywhere it dips rich and comes back with a little lean swing..

CÚdric wrote:

Power comes on pretty hard now when i leaned it out

I am also trying to get away from being so rich in boost.. It seems to make good power down to about 11 AFR but from 11 to 10.5 I can feel some power go away and it drops off drastically after that.. If it hits the high 9's it feels like it bogs right down..

I think this is getting to be a pretty good target for me up to 200kpa..

I'm still taking out a little fuel here n there but I'm getting close to that target map..
What do you think I should aim for for for 250KPA? Maybe 11.0?
Are you pretty happy at 11.5 at 200kpa?
I'm a scardiepants about taking taking out fuel..

14's all the way up to rolling into the 13's at 100KPA..
Low 12's at stock boost feels real healthy and rolling down into the lower 11s for my added boost areas.. Anything under 11 feels like throwing power away..
Another thing is that I'm needing to take some fuel out starting in the high 4k RPM area to keep my AFRs up, maybe because I'm going past peak torque/peak efficiency of my engine and VE needs to drop off some from there to keep the AFRs up and in the power through the rest of the rev range..

It sucks when it pulls great up to like 4800 and their is too much fuel from there on I can feel it make less power...
This is what it is doing to me when I push my boost a little higher than I'm tuned well for because I just have it set to go stupid rich incase of overboost and havent leaned out the high RPMs of higher boost yet.. The way my fuel map is right now it starts to bump into my "too rich" zone at around 15-16psi or just above 200kpa..

I can start leaning it out above 200kpa but I should not!
I want to really get everything perfect before I go messing around up there and wait till I have used up more of the warm season with a running car..
Over 200kpa may have an adverse effect on my engines reliability so though I really want to, I shouldn't..
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CÚdric  



Joined: 27 Aug 2004
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PostPosted: Fri Jul 26, 2019 4:19 am    Post subject: Reply with quote

That's an interesting thought, it might be some physical phenomenon with the plate. I have no boost enrichment at all in that log. I will try to log more driving conditions further on to learn more about it.

I had pressurising of the coolant system, so the head is now of and im planning on putting an mls in there. Still not decided on the arp bolts or not. Will do some small fixes like valve seals while im there. I did plan on it, was hoping to not do it in the middle of the season
I have some corrosion marks in the cylinder where there have been water, not decided how i will handle that. Can't pull the engine now, so maybe i will plan on a future bottom end swap. But not for a good while.

Had some fun in the twisties with a friend, last run before i parked the car. Drove some great roads!


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Fasteddie313  



Joined: 29 Sep 2013
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PostPosted: Fri Jul 26, 2019 5:06 am    Post subject: Reply with quote



I got the ARPs and don't regret it.. They are like $110 but I thought it was good bang for the buck seeing as they are reusable and keep some value..

Unless your engine sat for like a year with water in it, enough to actually create some deep pitting from rust, I doubt that it hurt anything if you are just seeing some brown stains.. How does it feel?
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CÚdric  



Joined: 27 Aug 2004
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PostPosted: Fri Jul 26, 2019 6:03 am    Post subject: Reply with quote

The arps are more like 220-265 usd here depending on where you buy them. But yeah, will probably go with them. Did you torque them according to arp instructions?

The corrosion is pretty bad, i can feel it with my finger. Not sure exactly when this started, it could be a long ago. Since i live in a winter country the car stands for 7 months aswell each year. Its happened on cyl 2 and 4. One is worse than the other.

The worst cylinder looks like this


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Fasteddie313  



Joined: 29 Sep 2013
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PostPosted: Thu Aug 01, 2019 4:46 pm    Post subject: Reply with quote

CÚdric wrote:
The arps are more like 220-265 usd here depending on where you buy them. But yeah, will probably go with them. Did you torque them according to arp instructions?

The corrosion is pretty bad, i can feel it with my finger. Not sure exactly when this started, it could be a long ago. Since i live in a winter country the car stands for 7 months aswell each year. Its happened on cyl 2 and 4. One is worse than the other.

The worst cylinder looks like this


I can get the ARPs for like 133 USD and reship them to you for whatever that costs.. https://www.ebay.com/itm/ARP-251-4701-Head-Stud-Kit/173646587010?epid=678973022&hash=item286e24a482:g:DUsAAOSwKhJdJ3f-

I may not have torqued them to whatever instructions..
iirc it said torque them gradually up to 90 ft/lbs and I did that but then I hear you are supposed to loosen them and retorque them or something..
I didn't ever loosen them, just pushed them all to 90 ft/lbs again after a couple runs..
I might check them to 90 ft/lbs on a cold engine again after all these heat cycles sometime soon, but I'm not loosening them..

I can't see anything too terrible in your cylinder from here, but I might not have a great view and certainly can't feel it.. ..
I'd say slap a new HG on it with ARPs, run it nice for a bit, and do a compression test and see what ya get..

Check for blowby too.. My blowby is still stock with the purolator to the upper air box lid, I was just in there a lot to access my airplate to get the calibration #s for the airplate travel sensor, and I'm dry as a bone coming out of the purolator.. Filter, aribox top, and plate are so dry I'm considering hitting them with some fogging spray to resist any possible corrosion..

If you do end up needing pistons I wouldn't mind getting together with you on some custom hardcore forged flat-topped pistons in a reasonable CR that will hopefully end up being non-interference to the valves..
Flat top pistons should be the cheapest to make custom right? Simple shape.. Zip zip on the lathe and done..
Forget squish when we are going to run 15-25 lbs of boost right? Couple % HP doesn't matter..
Lets just get some easy custom pistons with the right pin size and deck height to make the right CR, like 8:1 CR, that are made of the right alloy to hold stupid boost, and beat the crap out of them never having to worry about valve float from too many RPMs or a flimsy T-belt..

I think the bottom will hold about anything within reason, the top won't flow for crap no matter what, so just take care of the weak points.. The headgasket with an MLS, the head studs with ARPs, and the weak dished pistons with some JE forged flat tops, and give her all the boost..

Block is great, head clamping is great.. Subaru guys pay like $10k to make a block as good as ours.. Hold it in with a HG that won't leak, maybe even those cutrings, some pistons that will take it, and then it's just a question of turbo efficiency to jam the air into that 8-valve head, like your billet comp wheel..

We also still need a fix for that lower charge tube restriction.. You know what I mean..
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RC  



Joined: 25 Mar 2007
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PostPosted: Fri Aug 02, 2019 1:57 am    Post subject: Reply with quote

Would recommend using the ARP bolts, a small price to pay for the extra clamping force, reusability and reliability.

Fasteddie313 wrote:

I may not have torqued them to whatever instructions..
iirc it said torque them gradually up to 90 ft/lbs and I did that but then I hear you are supposed to loosen them and retorque them or something..
I didn't ever loosen them, just pushed them all to 90 ft/lbs again after a couple runs..
I might check them to 90 ft/lbs on a cold engine again after all these heat cycles sometime soon, but I'm not loosening them..


FYI there is a reason why ARP specify a particular procedure and the use of their lubricant. It is related to accuracy & consistency of the torque / stretch specification due to the variation of friction between the stud thread/ nuts/ head face when the lubricant is not fully coating all surfaces. Also to a much lesser extent, the microscopic deformation of the formed threads & stretch as they are "bedded in".
There may be a more detailed explanation on their website.

In a previous post related to the ARP rod bolts I measured and charted the torque : stretch. Note the difference in readings between the initial and subsequent tightning. See how the numbers are much more consistant after losening and then retightening. Head studs will obviously be different figures and tightened to torque specs, but the principle is identical.



http://www.924board.org/viewtopic.php?p=345162&highlight=arp+torque#345162


Cedric, is the cylinder rust you are talking about merely that 10mm or so ring at the top of the bore where the rings do not touch and the piston is at a smaller diameter above the top ring to allow for thermal expansion?
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