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28 minutes ago, madkaw said:

No experience with turbo builds , but from lots of reading here it seems that the very first things the guys do is the down pipe increase. You have invested a lot of money in forged pistons and other goodies ,  but you are choking all your investments with a tiny exhaust. 

Timing might also be a victim of your small exhaust. Don’t want to build heat by bottle necking flow. What was your timing at?What was your AFR’s?

 

Yeah certainly the downpipe was too small and using the off the shelf MSA unit was a mistake. Definitely building a new 3.5" one is on the list and I am fairly certain it will yield a large power increase. 

 

According to logging on this dyno run, timing ranged from 18-20 degrees of timing under boost (it has a bit more advance higher up in the RPM's.) Bigger downpipe could definitely allow for a bit more here as adding another degree produced no more power at this boost level. I think I was likely also being held back to some extent by high MAT temps, which were reaching mid 130F ranges with approx 90F ambient. AFRs were mostly holding steady at low 11's but were in to the mid 10's where the dips in power occurred. 

 

Also want to say that the car is really a blast to drive. Very usable power here, accelerates nicely and pulls hard in every gear. I'm not disappointed by "only" making 258whp but will definitely be back at the dyno looking for more. Mostly I am really happy to have the car working properly and producing good reliable power at this point

Edited by Zcardude

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It looks like you have all the ingredients to whip up some good power . I’d see what a 3” down pipe could do for you . It might change more parameters than you think.

Do you run a knock sensor or did they have one at the dyno? 

 

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Zcardude:  thanks for posting..  

 

seems like you only need some fine tuning.  nice job. 

 

Yeah, numbers are often not the whole story.  if it`s fun to drive, then it`s good, whether you have 258 or 358 hp..  

 

I just did some minor tuning on mine, and it went from total crap to almost total crap, and I'm very happy with the difference, so imagine a car that works properly..   

 

If you do go back on the dyno after slight mods, make certain you post, it`ll be an amazing pre- and post- mod data.

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Zcardude, I'd say there's a chance that a 3.5" downpipe might only net you 20 peak HP, but the benefits will be much, MUCH more important in all the other ways. You'll likely pick up a good amount of spool time, and by dropping the pressure ratio you're also likely to end up in a better spot of the compressor map which means you might drop a few degrees of inlet temp for a given scenario.

 

You might pick up 30-40 like you say, and that'd be great. I'm just saying that I'd be more focused/concerns about the transient improvements. You're already getting pretty great numbers out of that turbo.

 

Equally important of a mod would be to ditch the 280ZX Dizzy for "crank" signal. Put a sensor on the crank. You might find yourself able to run more timing as well as the dyno showing smoother power delivery. You're on a smoothing factory of 5 on a dynojet, and it's still showing lots of roughness. Imagine what it looks like with zero smoothing... I'd be willing to bet a huge part of that is trigger slop/scatter. Get that solved and suddenly the engine state will be smoother which helps ALL tuning aspects.

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On 8/18/2019 at 10:08 AM, Gollum said:

Equally important of a mod would be to ditch the 280ZX Dizzy for "crank" signal. Put a sensor on the crank. You might find yourself able to run more timing as well as the dyno showing smoother power delivery. You're on a smoothing factory of 5 on a dynojet, and it's still showing lots of roughness. Imagine what it looks like with zero smoothing... I'd be willing to bet a huge part of that is trigger slop/scatter. Get that solved and suddenly the engine state will be smoother which helps ALL tuning aspects.

 

Thanks for the info! I didn't know that the dizzy's pickup could be robbing much power if any. I am using a bone stock 280ZXT dizzy with Magnecor wires and MSD StreetFire ignition. I am definitely struggling still with power dips, as was seen on my dyno graph. Originally we thought that the tune was just a bit rich in those spots but that does not appear to be the case any more although I am getting the same dips in power on a re-dyno (no new graph to share, sorry, didn't make much more power although power is up a bit from smoothing out the AFRs and leaning things out a tiny bit). I was beginning to suspect that the MSD StreetFire was not able to produce a strong enough spark, but I'm glad to hear an opinion that the dizzy's lack of resolution itself may be at fault. Are there any simple tests I can do to rule out lack of resolution as an issue?

 

I get that you're saying I should do a crank-mounted trigger, but as a stopgap, I've ordered the DIYAutotune 280ZX/300ZX optical trigger disc and will be installing it in the next week or two and re-timing the car to see if that helps with the power dips. DIYAutotune claims these are good for full sequential fuel and spark so this should be a worthwhile upgrade in terms of resolution. Additionally, I have a friend willing to let me borrow an MSD 6A box to replace my StreetFire unit to see if a stronger spark will help, but I think I am going to hold off on trying that until I see what the better optical trigger does for me.

 

edit: Just want to note that looking at the datalogs with a few other people, I've been unable to determine any reasons why there are dips in power - the only things that ever show up on graphs are the dips in hp/tq themselves- AFRs are holding steady, spark advance steady, boost/MAP signal steady, MAT steady, etc so it really does seem like something mechanical or spark-related at this point. 

Edited by Zcardude

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On 8/30/2019 at 11:37 AM, Zcardude said:

Are there any simple tests I can do to rule out lack of resolution as an issue?

Feel free to send some logs my way to look at. I don't profess to be any smarter than other tuners, but sometimes someone will catch what others miss.

 

 

Do you have any VSS or MPH logging? If so, then take a long spirited drive making sure to row through the RPM range in several gears. Then pull up the log in MLV and make a scatter plot of MPH on the X axis and RPM on the Y axis. I use spark advanced as my color axis, but doesn't really matter. Here's what my super sloppy dizzy wheel looked like:

 

image.thumb.png.428b72fad2d7fc1f75418477801bd4fb.png

 

Notice the huge vertical distance traversed in RPM for a given MPH. What's more surprising, is when I select one of those entities, and then move forward and back through the adjacent log entries, it might be going from top to bottom of the spread during a WOT pull. That's a HUGE deviation and the motor itself is utterly incapable of undulating that much when in gear on the road. The only place that can come from is variances in the readings from the trigger wheel.

 

Here's another way to look at the same "noise". Look at my RPM reading during a WOT pull:

 

image.png.e09f996c9e60c78f93df18f428943865.png

 

 

SOME variations are expected, and I thought maybe I just needed to turn the lag up on the sensor reading. Then I found some tune files and logs belonging to a LS2, which has a factory crank mounted sensor. The WOT pull was smooth as glass, and lag was turned way down to 10 in his tune.... That RPM signal noise isn't power variance from bad fueling or loss off trigger signal. It's simply slop in the trigger drive leading to bad commanded timing, which just ends up fighting the input to the problem. No amount of having stronger ignition will fix that what the ECU "thinks" is the correct commanded timing might be wrong. Way wrong.

 

If you dig around you'll find that some people work really hard to remove slop from the system, and they likely fair a lot better than I did. But I say, sensors are cheaper than ever. Just get something crank or flywheel based and call it done.

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On 9/3/2019 at 11:33 AM, Gollum said:

Feel free to send some logs my way to look at. I don't profess to be any smarter than other tuners, but sometimes someone will catch what others miss.

 

 

Do you have any VSS or MPH logging? If so, then take a long spirited drive making sure to row through the RPM range in several gears. Then pull up the log in MLV and make a scatter plot of MPH on the X axis and RPM on the Y axis. I use spark advanced as my color axis, but doesn't really matter. Here's what my super sloppy dizzy wheel looked like:

 

image.thumb.png.428b72fad2d7fc1f75418477801bd4fb.png

 

Notice the huge vertical distance traversed in RPM for a given MPH. What's more surprising, is when I select one of those entities, and then move forward and back through the adjacent log entries, it might be going from top to bottom of the spread during a WOT pull. That's a HUGE deviation and the motor itself is utterly incapable of undulating that much when in gear on the road. The only place that can come from is variances in the readings from the trigger wheel.

 

Here's another way to look at the same "noise". Look at my RPM reading during a WOT pull:

 

image.png.e09f996c9e60c78f93df18f428943865.png

 

 

SOME variations are expected, and I thought maybe I just needed to turn the lag up on the sensor reading. Then I found some tune files and logs belonging to a LS2, which has a factory crank mounted sensor. The WOT pull was smooth as glass, and lag was turned way down to 10 in his tune.... That RPM signal noise isn't power variance from bad fueling or loss off trigger signal. It's simply slop in the trigger drive leading to bad commanded timing, which just ends up fighting the input to the problem. No amount of having stronger ignition will fix that what the ECU "thinks" is the correct commanded timing might be wrong. Way wrong.

 

If you dig around you'll find that some people work really hard to remove slop from the system, and they likely fair a lot better than I did. But I say, sensors are cheaper than ever. Just get something crank or flywheel based and call it done.

 

Thanks for the help!

 

I took your advice and dropped a recent log file and MSQ in to MLV, which I also attached to this post, and was able to generate the following scatter:

 

1766863468_ScreenShot2019-09-04at4_03_19PM.thumb.png.732d6e8f2f1880527df89f43402c1051.png

 

I have MPH calculated for 3rd gear only and no actual VSS input which is why I only get a single line here. Otherwise this is looking to me to have a large scatter, like in the graph you posted. I am guessing this should look more like a solid line? So this would point to slop? I am guessing this is somewhat mechanically tied to the rotation of the distributor, so maybe switching to the diyautotune trigger wheel won't help a whole lot and I should be looking at other triggering approaches.

 

I guess it's also worth noting that my RPM's jump around in a similar way to the other pic that you posted as well:1144900162_ScreenShot2019-09-04at4_08_29PM.thumb.png.11ccdb5aa2d486de1be95184ad86a132.png

 

edit: also, I did a fair amount of reading this evening and I wanted to note that I think you may be backwards on the lag settings: 100 is no smoothing, 0 is lots of smoothing. The MSQ I posted has a lag setting of 80. I looked around at some other L28ET MSQ files and I'm going to try out 50, which should add a fair amount of smoothing, and will see if that makes a noticeable difference with my setup. I'll also take another datalog and see if the RPMs are smoothed at all

 

 

2019-08-04_09.29.41.msq 2019-08-04_09.18.13.msl

Edited by Zcardude

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14 hours ago, Zcardude said:

edit: also, I did a fair amount of reading this evening and I wanted to note that I think you may be backwards on the lag settings: 100 is no smoothing, 0 is lots of smoothing.

2019-08-04_09.29.41.msq 119.77 kB · 0 downloads 2019-08-04_09.18.13.msl 2.91 MB · 0 downloads

Ah you're right, I'm sorry. My memory was failing me apparently. The LS2 msq I was mentioning was likely 90, not 10 like I'd said. I'll take a look at your msq and msl later today once I have time. Overall it does appear you have some scatter, but it also doesn't look as extreme as mine was. But definitely the same RPM reading jumps during WOT, You can see an obvious "high vs low" pattern and can almost draw two different curves across the low ports and high points. And engine doesn't rev perfectly smooth in WOT, but it also doesn't JUMP 500+rpm across one or two data polls in sub 15millisenconds....

 

I was 60 for my lag factor for a while, and was up at 90 when I blew my headgasket a few months ago. I'll be starting down at 30 and I'll see if I can raise it from there.

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Just had a baseline pull done on my 72 240-Z with NA L-28 motor. The block is a F54 with dished stock turbo pistons, E-88 head with valves unshrouded and and some port work, cam is 480 lift/276 duration, running stock cast iron manifold with 2 1/2 inch exhaust and straight through glass pack muffler, Pertronix ignition, re-curved distributor running 34 degrees of total timing, SB profile SU carb needles and ITG foam air filters. Pull was with 87 octane fuel. Best pull was 180.1 HP and 224.5 Ft Lb Torque. No dyno tuning to date but with some very minor adjustments believe I can squeeze another 10 HP out of her.   

IMG_4839.JPG

IMG_4842.JPG

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Hey randalla.

Thanks for posting :-)

 

Nice numbers...   I'm particularly impressed with the amount of torque and how much of it you're getting low-ish with dished pistons...

Must be a fun car to drive, without the hassle and the trouble and the gas money that can come with a turbo.

Just a question, why do you have two sheets that show very different result? Like, what info does each present?

S.

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The top sheet overlays torque and horsepower. The bottom sheet overlays horsepower and AFM readings. I have some work to do to lean out the AFM at lower rpms in order to flatten out the curve. Likely will be experimenting with some different needle profiles. Car is very fun to drive and was build to be very streetable with zero detonation issues. Planning to open up the spark plug gap slightly from .032 to .035, dial in 2 additional degrees of timing and re-check valve clearances and I may tighten them very slightly. Oh, and obviously I'll try higher octane fuel next time (91 octane).

Edited by Randalla

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bradyzq, I was a little mystified by that fact as well. When I dyno'd it I was running 34 degrees of total timing. I have since dialed in another 2 degrees to 36. The rpms were even lower until I changed out the SU needles for some that were much richer at top end. I'm going to try an even richer needle at top end to see if I can bump the rpms up a bit. Any other ideas? 

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2 hours ago, Randalla said:

Sorry, I misunderstood. Yes, re-checked the relationship between the cam and the crank and everything lines up properly.

 

With a degree wheel, per the cam card specs?

Edited by bradyzq

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