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Twisted46

Underwhelming Lap Times

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My main goal with the cage work was to protect myself  but also to eliminate the work of the body between the rockers. There clearly isn't a lot of meat there so I tied the frame rails to the rockers at the T/C rod mount points and the roll hoop legs are only about 3 inches from the rear frame so that was an easy box weld with some plate to connect the rear suspension to the rockers. Door bars are there to triangulate the rocker structure and provide side impact resistance with vertical bars that come down behind the front seat brackets. I plan to add some material that connects those vertical bars to the tunnel and figure out something stronger at the firewall. I also want to add a bar that connects my rocker to TC bars to the upper frame horns. I don't expect to feel that difference very much but I do think it will be critical when running 400 in/lb springs. 

 

In other news, I got tired of the 280zx rear brakes overheating and went with a SM wilwood kit.  

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@Twisted46 Thanks for the recommendation of the NCRCA, I'm very impressed with how much better the steering feels over bumps and within hard turns. It no longer feels like i have to fight the car in the corner.

I have to weld my strut brace up, from what Jon also says there appears to be a lot of improvements to be had. ( and hopefully shaved time in the corners). October 12th is the next day, plenty of time to do some testing before then.

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Posted (edited)

Tires are 225 but i didn't catch the other important size numbers.

 

Lots of guys have track records on 60 series tires because they maintain a bigger footprint through non-optimal camber changes than a square shouldered 60 series tire.     

 

Rim size vs tire size matters in contact patch area.

 

 

Edited by HowlerMonkey

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8 hours ago, HowlerMonkey said:

Tires are 225 but i didn't catch the other important size numbers.

 

Lots of guys have track records on 60 series tires because they maintain a bigger footprint through non-optimal camber changes than a square shouldered 60 series tire.     

 

Rim size vs tire size matters in contact patch area.

 

 

 

True,

The Subaru had 225/45 300tw rubber on 17x7 wheels. The Datsun has 245/45 100tw rubber on 16x8 wheels. I think the problem was down to front end geometry being out of whack and me getting used to the car. The tires are glue after 2 laps now and let me take corners faster than I am brave enough to. 

 

I will be sure to get some footage this weekend.

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Posted (edited)

@heyitsrama As requested: https://drive.google.com/file/d/1ZMTusthPTrX-YXbRUJZl4vM3uAgz9SC8/view?usp=sharing 

Ignore the tires rubbing the front flares :) a bi-product of wider front track I will need to address this over the winter. 

Also ignore the very incorrect time stamp, no idea how I did that. 

 

So this was my first full lap out and sadly ended up being my best of the day. Coming on to the front straight to end my second hot lap I got black flagged for spilling fuel out of the fill cap. Sure enough it was soaked so I taped up the gasket and that fixed the issue. Session 2 I started good but got black flagged again because of smoke coming from under the car. Turns out a plug in an unused dipstick port came out and was misting oil down on to the exhaust, fixed that.

 

I then started having fuel starve issues for the rest of the day that I had previously only noticed when I was running the fuel level too low but I was running around half a tank of gas (trying to prevent more sloshing out). Basically when I would get out of a hard braking/turning zone the engine would sputter if I tried to give it any throttle and AFRs shoot up in to the 20's. This was very noticeable down the back straight where I could get on it for corner exit but by the time I would shift to 4th I would basically coast along for about half the straight and then get power back. Obviously this killed my times and just threw my focus off in general and I ran in the high 1:50s the rest of the day. My assumptions are that either the stock pickup and baffle are just not able to take the Gs or have broken off. When I cleaned the tank they were in place but who knows. I don't THINK it is a carb issue because it acts fine mid corner and corner exit which to me rules out a slosh problem. It seems like the carb is not getting enough fuel during hard corners and uses up what reserve is left in the bowls before the system can catch back up. I testing the pump in car last night and it pushes 5.5 PSI and plenty of volume when sitting flat. 

I am already planning to add a fuel cell before next season so in an attempt to temporarily alleviate the issue I am going to run a bigger needle and seat to help with recover and try to properly seal the tank so I can run it near full without any issues. I know another quick fix is to raise float level but I would rather not. 

 

Good news, the brakes felt amazing and I had not overheating or dragging issues with the rears. I only have 1 track day left this season so hopefully I can get through it without issues. 

Edited by Twisted46

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Yeah, you probably already know that fuel starvation is an issue under heavy g-loading....even with as much as half a tank.  The fuel cell should def fix it.  A small surge tank in conjunction with the stock tank is another possible solution.  (Or just keep the tank at least 3/4 full all the time! )

 

I've had issues with fuel spilling out of the gas cap with certain locking caps, but never with the stock non-locking cap....they seem to really lock down tight and prevent any spillage even with full tank and long fast left-hand sweepers.  Are you having any pressure build-up in the tank; and if so, maybe consider how you have the tank "hosed" to allow venting?

 

Sounds like you've got a nice "to-do" list building for this winter!  :-) 

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@jhm I have a rollover/vent with loop coming off of the top rear port in the OEM tank. I have never noticed any pressure build up, sadly my OEM cap is not very snug. I have been on the hunt for a new gasket but can't find them. 

 

I absolutely do haha, although I do not plan on doing a surprise engine rebuild again this winter :) 

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