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Twisted46

Underwhelming Lap Times

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Well the catchy click bait title should be "My MONSTER V8 260z is SLOWER Than a Forester"

 

The real story is that I got to put in some good laps at Mid Ohio this weekend and my best lap was 11 seconds off my best lap I set in my 2012 forester XT, 2:06 to 1:55.

 

Now the forester had 2015 STI struts/springs and upgraded end links. It was also a stage 2 car so about ~300WHP but otherwise a stock car. I was running on 225 Hankook V12 EVO2s and had that thing at its absolute limit UNDERSTEER!!!!.

 

Now the 260Z, a 2+2 weighs at least 500 lbs less than the forester, probably more but I want to scale it before making any claims. It is completely stripped with a half cage right now. The SBC is probably making about the same power. I am on KYB struts and German 280Z springs, I replaced nearly every bushing with poly stuff and new tie rods/ball joints. Stock front bar with upgraded links and no rear bar (stock R200). The SBC V8 is in the JTR position(just enough room to rotate the distributor.) It goes without saying the CG of the 260 is WAY lower than the Forester. 245 R888r 200 race tires. I had the tires singing really nice and the car FELT great, just a little tail end slide in each corner and I could put it exactly where I wanted. I had a ton of fun but was getting passed all day (part of running with Porche club lol.) I could care less about getting passed by $100K+ 911s or anything for that matter but I know that I should be faster than myself in a damn crossover.

 

So here is the part makes me think something is up with my suspension geometry, I am making wider, stickier tires sing on a car that weighs less but I am going slower? Is there something that I am missing with my setup?

 

My winter plans include more cage work, front and rear tower bars, and adjustable front camber. Anything else I should add to my list? I have a baby on the way so no AZC stuff lol.

 

 

Note: of course I realize that the driver makes the single biggest difference in lap times and an AWD Subaru is a lot easier to drive at the limit. That is why I did not time my first few outings in this car until I really go to know it and get more comfortable.

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Too many variables to know for sure. Some questions though:

 

1) Is mid Ohio a high speed track ? if so, your aerodynamics might not be as good as your Subaru.

 

2) I didn't see anything about your brakes. Maybe you were able to brake later with the Subi?

 

3) Sliding is not the fastest way around a track. Theres lots of info on the site about setting up alignment specs.  I know when I was at the track, my lap times got faster, the slower i entered a corner. 

 

I'm no track expert, so take my advice with a grain of salt.

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Just curious....have you dyno'ed your SBC?  Reason I ask is because when my SBC was stock, it was making 179 hp to the rear axle.  It was a late-'70's stock block with a Holley 600 and block hugger headers.  The torque was good, but severely lacking in high end performance....which was pretty much par for the course in the late 1970's.

 

If you're running the stock front bar (either 18mm or 20mm, I can't recall which exactly), and no rear bar, you may need more bar.  Either bigger front bar, or a rear bar, or both.  Sounds like you're running aftermarket springs in the stock position....so they're something like Eibach or Stagg?  If so, your spring rate is probably 180 or 200 lb/in, which is on the soft side for track use.

 

More negative camber is an absolute must for track work.  On the front AND rear.

 

Also, has the track been repaved/refinished/etc or otherwise modified since you last drove it in your 2012 Forester?

 

New cars have extremely sophisticated brakes and suspensions compared to the archaic hardware on our beloved Z's.  Simple FOL.

 

Good luck with your winter plans

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"Make the tires happy, and the car will be fast." - tube80z

That's really what it's all about. By the sound of it the suspension is mostly stock. Mostly stock suspension on a Z = understeering pig of a car that won't change direction. You can compensate for that with a V8 by adding throttle, but it's not going to be as fast when sliding.

If you're really at square 1, I'd suggest getting some white shoe polish and making a mark in a couple spots on the tire, rolling over onto the sidewalls. You can then see how much gets wiped off on track and add neg camber to compensate. Beyond that you should be taking temps  on the inside, middle, and outside of the tread. Shoot for an inside temp is slightly higher than the outside temp on the tread, and hot in the middle means overinflated, cold in middle is underinflated.

LSD REALLY helps. I'm imagining you don't have one from the description of the rest of the build, but if you were spinning a wheel coming out of slower corners, just imagine accelerating in all of those spots instead.

Also a front strut tower bar made a massive difference on my 240. HUGE. 

As to starting alignment specs, John Coffey's guide is a great starting point:

 

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First, a dumb question. I know Mid-Ohio has two configurations, were these laps done on the same track layout?

 

Second, an essentially OEM strut and spring, refreshed balljoints and poly bushings do not a race car make, even with a sticky tire. All that with a stock front bar make me think that if the car felt great and you were getting loose on corner exit, you probably aren't anywhere near the performance envelope of the tire.

 

If this is going to be a track car I'd look into a good alignment, making sure you have good brakes, verify power levels/healthy motor, then start ticking off bigger projects like a good coilover setup (Koni or MCS), lowering the car and putting heavier springs/sway bar on it. 

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I looked at my lap data and have a different perspective. I'll try and post it later. 

Jesse, 

1 - it is a decently fast track, my average speed is ~75MPH. The Scoob is a brick but the Datsun has lift. I am lowered 2 inches with an air dam and front lip that is 3 inches off the ground. 

 

2 - Lap data tells the story, I was being a chicken on the back straight, off the gas and on the brakes 350ft earlier in the 260Z and not on the brakes as hard. I am running stock fronts with kevlar pads. Rear ZX disc setup.

 

3 - I guess the term is subjective. I don't mean drifting or anything close to it. I mean the front tucking in and rear swinging in to place nicely.

 

JHM, no dyno runs yet but I have high output gm iron heads and a mildly aggressive cam. FWIW

 

I will look in to a bigger front bar, the choice for no rear bar is because I don't have an LSD... Yet

 

I just have to decide what camber method to go with.

 

Track is the same surface 11 mos apart.

 

JMortensen,

 

Thank you

 

Ben,

 

Yes both times are running the chicane "link" 

 

Stock geometry with poly bushings and a lowering spring/strut combo. Yes it is not a racecar... Yet, I am working on getting it to that point but slowly over time. 

 

 

Thanks guys

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I was having trouble getting a video that made sense of the Forester and 260z overlayed.

 

After reviewing data and video it is clear I was being light on the throttle (which I kind of knew) and shifting too early (not in the power band). 

I am confident I can shave 4 seconds off of sector 3 if I stay in 4th and brake 350ft later lol, my corner exit speed is way better in the 260z.

 

Looking at sector 4 gave me a lot more confidence in the car and reminded me that it is all about the idiot behind the wheel. 

Sector 4 goes from a hard flat 90 right to a very tricky blind uphill that you really need to sweep a 1 turn with no brakes. 

It is nice to be able to see where exactly I made mistakes and really I was just being too timid with my speed. 

 

That being said I could see a ton of roll in external video, upgraded bars it is. 

Next season I will have more alignment capability so I am hoping to make my goal of getting in to the high 1:40s. 

 

 

    Sector Trap Time        
1 2 3 4 5 6    
16.62 37.1 19.55 13.48 21.76 16.64   Forester
16.02 34.95 16.75 13.45 20.04 16.01   260Z
0.6 2.15 2.8 0.03 1.72 0.63   delta
               
    Sector  Trap Speed      
81 109 46 60 53 70    
77 113 38 65 59 77    
-4 4 -8 5 6 7    

 

image.thumb.png.827f9b6f58b6738ebb77f5e2d6c660e7.png

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Cars always develop slowly, but it looks like you're heading in a solid direction. Lap data is the best! Nice work analyzing. I've used RaceRender for lining up video for comparison, and had pretty good luck. Although with an 11 second gap it might become not super useful quickly.

 

For reference on getting rid of body roll etc, I am a big fan on these cars of controlling the roll with springs. My car might not be the best example since it's auto-x focus and the setup is fairly aggressive, but I'm running 500lbs front springs, 400lbs rear, the 1" MSA front bar and no rear bar. The rear end has a very aggressive 1 way KAAZ diff and 3.90 gears. It's also very low, and I've got roll center adjusters in the front along with quick knuckles and have re-drilled the front subframe to further correct the roll centers. The end result is a car with a super responsive front end, but it's not a struggle to keep the rear end under control.

 

 Post up some video links if you get a chance!

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Ben,

 

Thanks again for the suggestions.

Unfortunately I showed up to the track with my only GoPro card full.... dummy.

 

Here is a clip my wife took, It was lap 1 so not full out but you can see how much the car is leaned over. 

https://drive.google.com/open?id=1lHUmts9dnRvONSdJXeCmxB1UYCDN7UCe

 

Here is a session I recorded in the forester last year

https://drive.google.com/open?id=1_cOSLhnecTk7zxuCZ1SZRiydYeTxENpG

 

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With out seeing if your driving style stays the same or changes for the Datsun, I would suspect it is similar for both vehicles.

 

It seems to me you drive into the corners with too much speed, not enough initial braking and drive thru at the same speed you came into the corner.  Then I also see you clip the corners, instead of staying wider on entry, then rolling thru the corner.

 

So attack the straights, set the vehicle up wider to put the car on the correct apex of the corner and get on the brakes before entering.  Then roll into the throttle and out of the corners.  Basically more aggressive with your pedals, but smoother racing line to reduce under-steer on your Subi and over-steer on your Datsun.

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Silverado,

 

Duly noted and I will take you suggestions in to consideration that next time I out there. My driving line is not terribly different between the two but then they drive nothing alike and have to be treated differently. I will post my corner entry, mid, and exit speeds later today, that will tell a lot too.

 

 

What do you guys suggest for front camber adjustment: arms or bushings? I would do the plates but my long term plans for the car involve a nice adjustable coilover setup So i will deal with that then. I plan to do bump steer spacers and TC rod pivot joints at he same time.

 

I am also looking at the 1-1/4" ST bars considering I am on 180lbs springs for next couple years.

 

Do you guys know of any triangulated front braces that work with V8s? Or is my best bet the welder and McMaster?

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Plates > arms > bushings. I would suggest you get a good set of plates. The plates that come with some of the cheaper coilovers only allow for 1/2 or 3/4" of movement. That's enough to even it out side to side, but not enough to get enough camber for racing. A set of "good" plates (Ground Control, TTT, AZC) has a large range of motion, I'd have to go measure but I'd guess 2+ inches.

Arms work, but when you adjust you drastically affect toe so that's a lot more hassle, makes it much tougher to make changes in the pits. Also there isn't that much extra thread in the stock tie rods, so if you adjust a degree of camber in with arms, you might need longer tie rods for safety. Add in an adjustable tie rod and you're coming pretty close to the cost of the good camber plates. TTT sells a pair of camber plates for $250. By comparison their front control arms are $400, and then you're probably going to need the tie rods in addition, which are another $150. You could piece together the rest of a coilover setup like was commonly done just a few years ago, where you would modify the stock strut tube to use the coilover adjuster, or you could buy BC or similar cheapo coilovers that weld on, and use the better camber plates on them to get the camber you need. Either way is better than arms and tie rods, IMO.

Camber bushings in front are not a good idea IMO. The bushings don't allow for fore/aft motion. The arm needs to follow the TC rod which moves in an arc, that means that something is giving every time the suspension moves; probably flexing the crossmember sheetmetal. Also adjusting the camber with the bushing adjusts bumpsteer. It's a bad idea to use these in front. They do work in the back, but I found that I had a very narrow window where the toe was set correct, so I couldn't get the camber I wanted and the toe I wanted in back with them. 

As far as building your own strut tower bars, you can buy turnbuckles from circle track parts suppliers or chassis supply places cheaper than you can buy the materials to make them through someplace like mcmaster.com. When I built my first set I didn't know much about this stuff so I bought "tap tube" and LH and RH taps and did it all by hand. This is a much easier option: http://www.colemanracing.com/Tie-Rod-Aluminum-P4199.aspx

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Thank you JM, I will avoid the bushings completely then. My only concern with the plates is that the ones I have seen replace the top hats and lower the car significantly or are only for use with coilovers. I do not mind going plates but I am not planning on dropping $2K for coils for another year or 2. I am building the car slowly so I want parts that will work now and later.

 

Is there a plate that can be used with OEM top hats?

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16 hours ago, jhm said:

Not trying to get this thread off track; but I'm curious what shocks you're running with those springs rates, @Ben280?  Also, is your front bar adjustable?  Thx.

 

I am running Koni 8611 inserts. Don't remember the specific lengths, but they come in a variety of sizes. I've had several conversations with Lee Grimes at Koni NA and he has said that the spring rate/weight of the car are well within the capabilities of these shocks. They are also rebuildable and have custom valving options if you need to get wild. The front bar isn't adjustable, but I'm planning to switch to a speedway style 3 piece bar this winter. I'll be making that somewhat adjustable, but more importantly, getting rid of the damn rubber endlink!

 

1 hour ago, Twisted46 said:

Thank you JM, I will avoid the bushings completely then. My only concern with the plates is that the ones I have seen replace the top hats and lower the car significantly or are only for use with coilovers. I do not mind going plates but I am not planning on dropping $2K for coils for another year or 2. I am building the car slowly so I want parts that will work now and later.

 

Is there a plate that can be used with OEM top hats?

 

You might be able to re-drill the upper mounts to get some more camber, but without switching away from the OEM rubber pile, I don't think you have enough range of motion. I can't remember how much room is in there with the factory suspension, but I suspect it's not much. I would guess tho that you could use some combo of the T3 upper spring seats along with their bolt in camber plates, and not lower the car toooo much. Would be a small investment and parts you could easily sell or put on a shelf for when you do get coilovers. 

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Yeah, I think the problem is that you'll run out of room moving the stock spring in there because it's wider than a 2.5 ID spring. As far as camber plates that actually adjust a decent amount go, outside of TTT, AZC, and GC, there is the "biscuit" style which doesn't require cutting, but I think you'll need the smaller diameter springs to get enough movement for the track.

https://www.dpracing.co/datsun-z-front-suspension-1

It's really not that hard to piece together a coilover setup with threaded adjusters, top hats, and springs if you want to get the camber. DP has everything, so would Coleman Racing or similar circle track supply houses. 

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Here is some corner data, I recorded the chicane "kink" as one corner since you really never open the wheel up.

 

  Corner   Forester                
1 2 3 4 5 6 7 8 9 10 11  
75.5 84.2 51 66 51 51.7 45.2 66.7 57.3 69.3 56.5 Entry 
66.1 67.4 29.3 50 47.5 49 57.4 69.7 51.1 - 23.1 Mid
77.2 61.1 55.9 43.2 37.3 45.7 66.7 57.3 46 - - Exit
      260Z                
73.7 76.8 46.3 53.4 47.7 51.6 45.6 57.3 55 74 54.4 Entry 
65.1 62 37 41.7 37.4 50.2 51.2 61 44.4 66.3 25.1 Mid
62.8 56.7 31 40.5 43 45.1 57.3 55 46.1 56.9 35.4 Exit

image.thumb.png.67f1ab363adbecc206aa7c2d9aa47531.png

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Okay after spending more time staring the frame and suspension here is what I came up with for better/flatter cornering.

 

Chassis work: I won't go in to detail in the this thread but my objective is to stiffen the car by connecting the front/rear frame rails to the rockers and tunnel, and tie the roll hoop to the front floor pan/rocker union.

T3 triangulated strut brace.

 

Camber: For now I am just going to stick with camber arms to get some use out of my new struts and springs.

Body Roll: ST F/R sway bars (240z style) and bad dog plates.

Misc: T/C Rod ball and socket swap.

 

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