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simplicity and reliability, ZX turbo track toy

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Having trouble uploading the video, but if it worked here's a lap from my recent visit to buttonwillow.  Had some running issues, but overall felt great to get out on track.      edit; re uplo

@260det,  thanks for that.  I've got a few ideas going right now, going to do some prototyping and hopefully make some improvements. A few updates from recent activity. Earlier last year when I

I did lots of things to the car this year, but didn't feel it was necessary to update here until I had some results. The main outstanding issue with the car after Thunderhill was the cooling system

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4 hours ago, 260DET said:

Cooling problems on my 280ZX were fixed by removing the stock bonnet vent inserts and replacing them with coarse mesh with a mini air dam in front to kick the air over the vent and create a low pressure area over the vent.

...and the drivers side vent air dam can be seen in the video you linked in your signature.  Thanks for sharing!

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@260det,  thanks for that.  I've got a few ideas going right now, going to do some prototyping and hopefully make some improvements.

A few updates from recent activity.

Earlier last year when I rebuilt the gearbox I replaced the factory transmission mount isolator with the 240sx unit.

The only modification required was drilling two holes in the crossmember. 
This Megan racing mount came on one of the 240sx boxes I got, and is a bit more robust than a ZX unit.


The engine mounts tore again, so I ordered some OEM Nissan mounts from japan. 
The OEM mounts immediately delaminated on installation, so I ordered up some silver project mounts and they work just fine on the stock ZX.
They are a bit stiff at idle with the cam, but while driving I can't tell the difference. 





Took the opportunity while everything was apart to finally fit on my #5 bypass, should help flow at the back of the head at least a little bit.

AN to BSP fitting was easy enough to source.  The throttle body heater cap was also leaking, so it was a good time to re-seal that. 



The front sway bar was also binding due to some janky drifting stuff I did to get more clearance for the brake calipers at full lock. 
Steering is much more complaint now, as it should be. 

Went to Thunderhill East this weekend and got on track for my first lap, engine was misfiring and I get black flagged for oil smoke in only a few laps.

The driveshaft munched up the transmission output shaft seal, and it sprayed fluid all over the exhaust causing the smoke. 
I suspect it was due to the old failed engine mounts, but I'll find out for sure if it fails again. 
The parts shop in town had the required seal, I also got a coil and spark plugs to combat the misfire.

I missed a few sessions, but I got it back on track with no leaks and running better than it has in a while.  Set a 2:16.030, at least at a similar pace as the rest of the run group. 

The water temps get too hot after just 4 laps flat out, as mentioned previously in the thread I'll have to start doing something about this. 

A while ago I had adjusted the water temp enrichment table in the ECU to go very rich when the CHTS detects 240 degrees, and it worked great.  At just about 230 on the gauge and it goes rich so I'm not tempted to keep pushing it.  




Edited by stupid_fast
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  • 9 months later...

I did lots of things to the car this year, but didn't feel it was necessary to update here until I had some results.

The main outstanding issue with the car after Thunderhill was the cooling system. 
Got a TIG welder earlier this year in February and learned how to booger weld aluminum enough to start on cooling modifications.

I started with building an intercooler setup. 



Since I'm staying with stock EFI, I wanted to add a recirculating BPV so that required the intake boot to be replaced.




The factory intake box does not fit with the intercooler, considering my options I was unhappy about just running a pod filter in front of the radiator.
After a bit of angle grinder action, I found room for the intake under the headlight bucket. 




I bent up a piece of aluminum to box in the filter.  Took one out of the lemons build guide and secured it with self tappers.  Rivet nuts can be added later. 



Welded up the internal water pump bypass.



Welded up the radiator cap, removed the restrictive shroud, and relocated the oil cooler behind the radiator.
Methodology here is that the cooling stack is supposed to run from coolest to hottest.  


Added in a cheap ebay expansion tank and overflow bottle with a 22psi cap. 




I extended the fuel pump bracket to add a pre filter and upgraded to an 044 pump and changed the differential to an open unit. 




Built another set of axles, and tired of killing them I raised the rear ride height by 1".
Also adjusted the camber back to negative since I'm not drifting. 


I modified the wilwood combination prop valve bracket to fit on the z32 bmc.



Changed the cam to a factory 'A' cam.  The extra RPM wasn't doing anything for me. 


I decided it was time to rebuild the rear brake calipers even though they were not leaking.
After pulling them apart I found the cylinders were complete junk full of rust pitting. 
Got a set of reman calipers and now the rear brakes are working well again.


Built a bracket for a generic ebay adjustable wastegate actuator. 
It seems to work better than the old worn factory units I have. 



The ZX engine bay looking even more crowded than it did from the factory, however its now at the best state its been in since I got it.

Back to Buttonwillow for the yearly SpeedSF black Friday event.
Last years event they lost the lap timing for my fastest lap, but it was somewhere in the 2:13 range.  I had some issues in the morning but was able to get out for the last two sessions and managed to get down to a 2:08.582 with the same tires from last year. 

Positives from this event, the car is making a lot more consistent power in spite of running rich.  Still on low boost around 8psi. 
The cooling issues are completely gone, the water temp stabilized at 185-190 and didn't move pushing it for a full 20 minute session.  Oil temp stabilized at 250.

Now that the car is running faster the oil pressure is dropping on almost every right hand corner.  A baffled oil pan is next on the list before I can get back on track.
I changed to an open M30 differential, but raising the ride height gave a huge oversteer bias on the car and now the thing is really skidding around everywhere.  
Going to move to softer springs and adjust the suspension geometry a bit. 

Going to be interesting from this point on, I feel like the car is at a stable baseline and I can start actually tuning things rather than fixing major issues. 

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Nice work. That thing is loose on entry! What are your alignment settings? With how loose it is right off the bat, it makes it seem like your rear tires are shot and/or not enough rear camber and toe-in (not familiar with the S130 platform but I'll assume it's difficult to dial these in independently with the semi-trailing arms).

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I think the suspension is just too stiff, I'm going to get softer springs first then see from there.  There's practically zero body roll in corners and not much compliance over curbs. 
Also running the big MSA sway bar kit front and rear, the rear bar might be too stiff.  Unfortunately I threw away my stock sway bars. 

The tires are 225 front and a 245 rear, they've got most of their tread and are about 2 years old but garage kept.  The rears are also a few months newer than the front tires.  
If they were shot I would expect another few seconds on the lap time.   Grip level is about right for a 340 treadwear summer tire and I didn't get a chance to dial in the pressures, they were about 28psi hot. 

camber -3 front -1.8 rear
toe 1/16" in front 0 rear
About 3.5 degrees of castor.

It used to have heavy understeer bias when it was lower a few years ago when I ran it at Thunderhill west with 205 tires.  Almost the same alignment specs from back then, just different ride height.

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I bet when you were lower, your rear camber was closer to what the front was. That can make a big difference in balance especially if the tires are more camber sensitive.


A little bit of toe can go a long way as well. Zero toe in the rear could be a big part of the looseness, depends on your rear toe compliance (rubber bushings or PU?). Also try zero toe up front or even a tad toe out to tone down the yaw rate gain a bit. YRG is essentially a measure of a vehicle's response to a given steering input--the more your point the tires out of the turn, the lower your YRG. Meaning point the fronts out and the rears in if you want to take some oversteer out.


Softer springs could help but looking at how early the car oversteers during the cornering process is making me think that the main problem lies elsewhere. I could be totally wrong but that's what I'm reading in between the lines.

Edited by Leon
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