kmead
Old enough to know better
Curious, do you know what VW Bug that rear bar came from? Thanks
A great read and good luck at your next race.
24 hours of lemons build and VW VR6 swap.
- Thread starter rozap
- Start date
A great read and good luck at your next race.
Rupunzell
Bernice Loui
What are the spring rates used front/rear?
Add a brake bias bar to adjust brake balance front-rear. This can greatly improve brake performance and lower brake temps.
-.5 degrees of negative camber seems small. While tire dependent, more grip could be had by increasing the negative camber any where between -2 to -4 degrees. Make sure toe front/rear is balanced to the center line of the car. Toe can be zero to slight toe in (not more than 0.10") and slight toe in at the rear about 0.050".
Do check tire temperatures across the tread, front/back the instant car comes in from the track. If all is mostly good, tire temps will be essentially uniform across the tire and front/back.
Not wise to add power until the chassis/brakes are Completely Sorted Out... Far too many at LeMons believe adding more go = win..
This ideology has been proven false time and time again.
Property built/put together Lampredi SOHC easily survives LeMons racing at nee 100% power ("Hot Rodded" not stock) for more than one race.. Key is prep and not using knackered parts and don't skimp where $$$$$ needs to be applied.
Bernice
rozap
Daily Driver
It's unclear what VW bug it came from, and it may have even been from a bus, and they may be aftermarket as well. A friend of a friend had a pile of old VW junk and I had mentioned that I was going to make a sway bar, and he gave me a bunch of them for the spring steel, and I was figuring I'd have to weld ends on. It turned out one of them in the pile fit like a glove. Sorry I can't be more helpful here. It's a very LeMons solution - using stuff that was headed off to the metal recycler.
350lb/in on the back, 250lb/in on the front. It doesn't feel too stiff, but it's definitely stiffer than it was. It behaved really nicely.
Maybe I'll try more camber. There was some rollover of the sidewall. What width of tires were you running when at -3* of camber?
We have a brake bias bar on the dual master cylinder setup. There's a picture of it in this post. There is a cable to turn the bias bar hooked to a knob on the dashboard, but we didn't have to touch it during the race. I dialed it in prior to the race and we had no imbalance so we didn't have to mess with it.
The intent was always to get the brakes and suspension to a place where we're happy, which we achieved in the previous race. Then add more power. The speed creep over time in the Lemons series means that as it sits now, our car is generally in the bottom 5 out of ~40 entries in terms of outright lap time. The last two races we finished better than our speed would suggest because we were consistent and had few issues.
Also, we were featured on the lemons youtube channel here, where I talk a bit about our experience with the car
rozap
Daily Driver
Much of this is down to my limitations as a driver, and some of it is down to the fact that it's a purpose built car. The reason this car is so fun is because I can drive it near the limit and not be scared to death, and I'm also not so worried about ruining a nice example of a car if I have a moment. Driving my esprit on the track is fun for other reasons (the noise, the handling...) but I'm definitely not pushing as hard and I'm a lot more tense. Most of that is down to my own headspace.
Rupunzell
Bernice Loui
Stuff to consider...
~Team & your goals for LeMons racing would be?
Highly recommend reading this series of books by Carroll Smith staring with Prepare to Win..
Race car prep and build is not simply cut/weld (hot glue)/experiment to see if what was made is gonna work.. There is very real engineering, design and consequences to anything done on a race car. What appears to be a not so relevant or important penny screw/bolt/washer/nut could come loose or fail ending the race weekend or crash or injury or more. Get comfy with using aerospace hardware (Boeing surplus), new metric hardware and proper materials for builds. This is astonishingly important stuff that should never be taken for granted.
On the rotary powered exxe LeMons car, front spring rates are 650 to 550 lb/in, rear sprint rates are 450lb/in to 400lb/in and the dampers (struts) Must be able to control these spring rates. Do NOT skimp of springs, use only Hypercoil, Eibach, Swift springs.. Low buck springs are source of constant suspension set up headaches. the 2.5" spring conversion has bee done. Do corner weight the chassis to establish a starting point for the chassis.. No "anti-sway or anti-roll" bars front or rear. Roll stiffness comes from spring rates, not "helper" bars.
Race ride height is about stock height with the front visually slightly higher than the rear. Excessive lowering will put the suspension in a wonky area of the designed in suspension curves. Bump steer in the front can be adjusted-corrected as needed by altering the steering ball joint location relative to the front upright steering arm. Get rid of all the rubber bushings in the suspension, replace them with aerospace spec teflon liner & staked spherical ball joints. Cheap-O spherical bearings will produce wonky suspension behavior. Starting point for alignment, about 7 degrees caster front, -2 to -4 degrees camber front/rear, 0 toe in the front, 0.050" to 0.080" toe in rear_refernced to the center line of the chassis (this is Really Important). Last set of tires on the rotary exxe were 195/50/15 Dunlop Direzza on 7" wide rims all around about 30psi adjusted as needed.
That brake master cylinder conversion appears to be out of the PBS book.. Stop there, as many of the other mods in the PBS book are not good at all specifically their idea of lowering the entire chassis and spring rates/damper set up produces a wonky behavior chassis...
Front rotors were from MX-5 with four piston WIlwood forged calipers (some what remember they were 4x 1.38" pistons) and stock front calipers in the rear with Hawk ferro carbon Mazda RX7 rear pads and Wildwood pads (no longer remember the compound) front. Brake pad were was a non-issue, Stopping power was Good... If you're using Fiat 500 front calipers with 54mm pistons and stock rear calipers with 34mm pistons, the front pads will continue to over cook no matter what is done and the brake balance will never be correct regardless of the bias bar.. Fiat 500 calipers are designed for a FWD chassis with most of the weight up front essentially opposite of the exxe chassis. 5/8" master cylinders seem awful small... Solid pedal means zilch if the stopping power and balance is not proper.
As for what is possible with a properly built for endurance racing Lampredi SOHC and good chassis set up, LeMons video from 2012.
That would be 5.0 Liters of German V8 -vs- 1.5 Liters of Lampredi Italian style..
We ran about 6th overall in that event..
Years later, the Mazda rotary conversion was done.. after much sorting, here is a video of the rotary exxe on the tail of Eye Sore Racing's turbo Miata with Dave Coleman (chassis-suspension engineer for Mazda USA) driving..
Few years back, Jay and crew did this write up:
Fiat X1/9 Frankenstein: A Rotary-Swapped Hella Sweet Car of the Week - 24 Hours of LEMONS
It's time for another Hella Sweet Car of the Week and it's another Fiat...kind of. The Italian Stallions built a rotary-powered monster out of a Fiat X1/9.
24hoursoflemons.com
The rotary exxe uses up about one 12A peripheral port rotary race motor 1-2 races.. If all goes good. Lost count of how many of these rotaries that have been grenaded, then "re-built"... Current iteration of the rotary exxe has a dry sump 12A peripheral port rotary and Hewland formula Mazda race box.. the Porsche 901 was expensive and not up to endurance racing and gear ratio are no where near ideal for road racing..
Bernice
rozap
Daily Driver
When you say overcook, do you mean uneven pad wear or brake fade? I haven't experienced either. Stopping power is good when everything is up to temperature. Wheels all lock up at the same time when the balance bar is adjusted properly. The 5/8" MC did seem small - initially I had 2x 3/4" and the pedal was much, much too stiff and it was impossible to stop the car. I swapped to the 5/8" and that's what we ran in the race.
My concern is for the transmission. It's already the weak point so I don't think adding power is wise. That's why we're doing the swap.
Rationale here is that I'm not going to swap spring rates every time we change something on the car that impacts the balance, of which there will be many. Ie: engine swap (about 70 pounds heavier), moving the fuel cell to the front, etc. Dialing in the balance via adjustable bars is much more achievable. In a perfect world though, I agree. If you're doing it from the factory and have access to engineers/suppliers/tons of test time, then sure. That's how my lotus is set up. But it's not an x1/9 built in a garage...it's a plastic car built by blokes in a shed in norfolk.
The rotary swap is badass, and that's some good driving. I don't think I'd have the patience for the rotary though.
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rozap
Daily Driver
We completed our last race on the 1500cc engine. Before the race I changed the oil and found a number of large chunks of bearing in it, so I had many concerns, but it was too late to rebuild the spare engine so we just went to the race and hoped for the best. The oil pressure was still good, and there was no noise, but I figured we'd get around 10 laps before it deposited a rod on the pit straight. So we started off with super short stints so everyone got a chance to drive it. But the little 1500 held on for the entire race and we managed 249 laps. It was a super fun race with a lot of changing conditions again, which slowed the whole field down and we had some really fun w2w battles. At the end we were in a battle with the chevy stylemaster for IOE, and only 3 laps down on them and around 25s per lap faster, so it came down to the wire, but the prize went to them. I think we could have beat them but there was a very long red flag on day 2 from a BMW in the wall (everyone was OK). We had a few off track excursions on day 1 in the wet, and the starter wire fell off again so we were push starting the car.
Front and rear sway bars helped the car quite a bit, and the balance ended up being great, so I didn't mess with the adjustment at all. It understeered a bit on corner entry, so you could trail brake pretty deep into a corner, and through the middle of the corner felt really balanced. I might add a bit of rear bar but overall I'm super happy with our improvements.
I think I'll need to corner balance the car as I got a couple front left lockups in the wet. But braking performance continued to be really good and I was braking later than many other cars could. I had a few somewhat sideways moments in the wet but the car was easy to manage, and a few moments where I overshot my braking point, but still managed to hit the apex, so it turns out I could have been braking harder and later and I was leaving a lot of time on the table that way. I need to work on my ability to move closer to the limit rather than settling into a rhythm and just turning laps. Still improved the fastest lap by a second from last time out.
So this winter we'll do the engine swap. I'll be surprised if we get it done by the next race (likely in April) but we'll see how it goes.
Front and rear sway bars helped the car quite a bit, and the balance ended up being great, so I didn't mess with the adjustment at all. It understeered a bit on corner entry, so you could trail brake pretty deep into a corner, and through the middle of the corner felt really balanced. I might add a bit of rear bar but overall I'm super happy with our improvements.
I think I'll need to corner balance the car as I got a couple front left lockups in the wet. But braking performance continued to be really good and I was braking later than many other cars could. I had a few somewhat sideways moments in the wet but the car was easy to manage, and a few moments where I overshot my braking point, but still managed to hit the apex, so it turns out I could have been braking harder and later and I was leaving a lot of time on the table that way. I need to work on my ability to move closer to the limit rather than settling into a rhythm and just turning laps. Still improved the fastest lap by a second from last time out.
So this winter we'll do the engine swap. I'll be surprised if we get it done by the next race (likely in April) but we'll see how it goes.
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Alex(Tenerife)
True Classic
Sounds like you had a great time. Not jealous at all
carl
True Classic
When I raced motorcycles there were many times when I was 100% convinced I had waited too late to brake for a corner and yet sailed through the corner with no drama. I think a lot of us are leaving a lot on the table in regard to braking. Of course I would rather brake a little early than shoot off a corner because I did wait too long.....the joys of being an amateur rather than a paid to win professional.
Rupunzell
Bernice Loui
No surprise, a proper Lampredi SOHC engine is a LOT more reliable/durable than most would know or believe.
Again, all it takes is one item great or small to create serious problems. What appears to be absolutely insignificant nothings can be race enders.
Never take any item for granted This means the tiniest what appears to be the most insignificant screw to seat mountings to suspension mounts to wheel screws and as in this case.... a wire.. Do the work, do the prep, check everything three times over and leave no perceived to be insignificant detail ignored.
~Murphy was an Optimist... Murphy will bit at any moment, any chance allowed.
Take the time to read this current discussion on suspension:
Suspension Thread.
In another post, @Steve Hoelscher and @Rupunzell were both commenting on not using the Miata suspension as there are much better choices. So, I thought it might be interesting to discuss what other options might exist out there for a custom setup. Note, this is not intended to be a bolt on...
xwebforums.com
All that was discussed applies to your LeMons racer. IMO and real world experience at LeMons and lots more, the exxe chassis/suspension can work excellent with no stability ala "anti-sway" bars. Increasing the springs rates Greatly from 300_ish lb/iin works better than those "bars" for a variety of reasons discussed in that thread. Keep in mind this is a track car where ride is a much lower consideration and suspension travel is not always needed for a smooth road/track surface... LeMons racer is not a public road car (or should be a public road car.. even if it's been done more than a few times)..
Front brake lock up is a brake bias problem, not a corner weight issue. While corner weight of the chassis/suspension does have an effect on brake bias, that is not the primary problem here. Given there is a mechanical brake bias adjuster, bring that adjuster cable and adjuster to easy reach of the driver. Brake bias should be a driver adjustable item that can be tweaked per race lap as needed.
As for corner weight of the exxe.. It is less essential (given the stock suspension design and set up has not been greatly altered) compared to other aspects of chassis/suspension set up. Put the chassis/suspension set up time, effort, resources else where.. like spring/damper rates, getting rid of the rubber/polymer bushings in the suspension, making a precise-accurate suspension/chassis set up rig followed by logging/recording what various suspension/chassis set ups do on track and making them repeatable.
There will be a cargo ship load of stuff to sort out once that alternative power train is installed.. Be well aware and well prepared for that.
Bernice
Steve Hoelscher
True Classic
Individual front brake lockup is typically _not_ the result of bad corner weights. That is, unless its REALLY bad, which is rare.
Its a popular misconception that the car sitting stationary on the scale, with poorly matched front wheel weights, results in front brake lockup. The reason is very simple; static corner weights and dynamic weight transfer are not related. Corner weights are far more about turn-in and steady state balance than braking.
Lets use my favorite bar stool as our example: Take the bar stool and put a shim under one leg. On a flat floor you now only have three legs in contact with the floor at any one time. Now, to simulate braking, tip the stool in toward any one of the four sides and those two legs are now in contact with the floor and only one leg on the opposite side contacts the floor. Apply this to corner weights and under braking, bad corner weights will usually result in one _rear_ wheel locking up first. But because its so lightly loaded the driver seldom notices it.
Consistently locking one wheel is more likely to be a brake issue than a corner weight issue. A sticking piston, caliper float pins dragging, pad miss-alignment, etc... But most often its just chassis dynamics; slight load transfer due to some amout of steering input, an alignment setting (mis-matched caster can do this) or a missmatch in front shock compression dampening (VERY common!). Miss-matched tire temps are also a cause (a track that consistently overloads one front tire can over heat that tire or the opposite is below operating temperature). The other thing that can cause it is variations in the track surface.
My experience as a race engineer has taught me that corner weights are important, but not critical.
kmead
Old enough to know better
And usually the offending caliper is the one that didn’t lock.
Steve Thomas
True Classic
Ride height looks high, very high. Probably due to big dia tyre?
Steve Thomas
True Classic
Understood - no idea what the situation is in the US
Certainly in Australia, there are a very large number of 13 inch tyres available. When you come to lower it - that is tricky. Pretty easy to conventionaly lower an X [coilovers etc] and ruin the handling. If you have time, while doing the engine change say, find some 13s
rozap
Daily Driver
Thanks, this is helpful. Some people go on about how corner weights are absolutely critical, but I won't sweat it too much. If i come across a deal on some scales, I'd like to pick some up, but there are more important things to do first.
When I think about where I had the lockups on the left front, they were into left hand corners, and it was wet and oily. I probably had the right side of the suspension loaded up ever so slightly as I pointed the car in.
Rupunzell
Bernice Loui
Corner scales are useful only when the coupled with a fully adjustable suspension and various suspension bits (selection springs, adjustable dampers/struts and etc) that can be adjusted as needed. Corner scales need to be on a level surface or the readings will be questionable.
The process when properly done is more involved than most wanna deal with. It is important, but no where near as important as making absolute sure what is perceived as tiny insignificant items like wires to the starter, transaxle mount hardware and etc never fail again... ever.
After the chassis/suspension on the rotary LeMons's X was made adjustable, we would do track testing days to sort out the chassis.. This was after nothing fell off the car, power train working good enough.. Then it was how do the drivers want the chassis/suspension to behave or trading off goals and needs.
Suspension and Alignment: A Saga
Welcome intrepid reader. I have a tale that in which mystery abounds. Many years ago, I installed Vick’s performance springs with KYB gas struts in my ’86 X1/9. After a while, I noticed that the rear was lower than the front. Measuring the pinch welds behind the front wheels and in front of the...
xwebforums.com
The corner weight scale pads sit on leveling pads, it took quite a while just to get all four level. Then put the LeMons X on the hub stands,
on the corner weight pads, get it all set up.. then tweak the suspension/chassis as needed..
As previously mentioned, if there is front corner brake lock up, look else where for the problem (IMO, allow the drivers to adjust the brake bias as needed, per lap, per track conditions, per car condition and the drivers will need to adjust how they are using the brakes.. Good braking into a corner means using all available traction from the tires with no skidding or lock up) not static corner weights of the chassis/suspension. None of the drivers reported brake lock up issues even before we modified the chassis/suspension of the exxe to be fully adjustable.
Static weight of the car will shift due to the dynamic/changing forces that act upon the car once moving. The really excellent drivers are extremely aware of this and know how best to exploit this given reality. It is also why braking, cornering and all changes greatly under dynamic weight shifting conditions.
Keep in mind, once that alternate power train is installed, you're starting at square one again. This will and can test your ability to sort out the behavior of the car in ways un-appreciated at this point.
Bernice
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rozap
Daily Driver
The more I've had to decompress from the race, the more I feel like the lockups were due to driver error versus the setup. I really only grabbed the wheel 3 times in ~100+ laps, and it was really, really wet and oily. It rained all weekend. Also the e30 lotus cortina's oil cooler fell off and I hit the oil patch before the yellow and red flag came out. That was a pretty spicy moment to instantly have 0 grip in T1 after the long straight. The car was easy to reel back in though.
I'm looking forward to the swap. We're planning to do some autoX and track days before registering for the race to work out some of the bugs. We don't *really* do lemons to be competitive, we do it because we like working on the car together. That's the real reason behind the oddball swap. If we really wanted to be competitive, we'd be doing a k20 swap like everyone else...no wait...we'd be driving an e36 but that's no fun...
I'm looking forward to the swap. We're planning to do some autoX and track days before registering for the race to work out some of the bugs. We don't *really* do lemons to be competitive, we do it because we like working on the car together. That's the real reason behind the oddball swap. If we really wanted to be competitive, we'd be doing a k20 swap like everyone else...no wait...we'd be driving an e36
but that's no fun...
Steve Hoelscher
True Classic
Glad to help.
There are lots of these miss-conceptions, since before my time, are accepted as common-knowledge, but are just wrong.
Corner weights are much more important regarding turn-in and overall corner balance than braking. They are important to ensure consistent balance turning either right or left, or, can be used to tune a car's prerformance on a track that has a significant bias to one direction (like an oval or a road course like Limerock Park).
The other thing that people don't seem to understand is: weight jacking (using the spring perch height adjustments) does not compensate for a car's CG location. That is: no amount of playing with corner weight numbers will compensate for a car that is heavy on one side, or one end.
Driver error might not be the correct attribution for the lockups. Changing conditions in endurance racing is a significant variable that requires drivers to adapt. That is a learned skill and a fairly high level one. Low grip conditions are challenging for the driver to maintain consistency which compounds the adaptation factor.
I know when I am pushing hard, working on setting fast laps, that the difference in car placement, dynamic state, and driver execution are magnified. It takes a tremendous about of focus and a very high level of execution to get it right every corner.