Celebrating the fact that the Seven is up and running with an autocross video from Marina. The car still has an intermittent misfire that I am trying to iron out but it is running well so far.
Archive for the ‘cars’ Category
Back up and Running
Thursday, November 8th, 2012Brake Bias Issues
Friday, February 3rd, 2012The only major dynamics complaint I had about my Ultralite was the rear lockup issue under hard braking. The car comes with a very nice set of Wilwood brakes (front and rear) with separate master cylinders for the the front and rear so it definitely wasn’t a component quality problem.
The issue I was having is that under hard braking at autocross the rears would immediately lock up and cause a lot of oversteer. This was even worse at the track where braking at the end of straights would lock the rears well before the fronts leading to bad porpoising at the rear. The whole issue was being caused by having equal braking capability front to rear which meant that once the weight transferred forward under braking, the rear wheels had very little weight on them and were prone to locking up while the fronts were still spinning. You could avoid this by braking earlier but this would mean that the front brakes would not be used to their full ability and would lead to longer stopping distances. The real solution would be to move the brake bias forward which I first attempted to do using the balance bar in the pedal box/master cylinder setup. This made no noticeable difference to the brake bias which meant that the bias issue was worse that I suspected.
Step two was to install an inline proportioning valve(below) on the rear circuit which could reduce the rear line pressure by up to 57%. While this did make the autocross situation much better I still had the problem of rear porpoising at the track albeit much better than before.
After consulting with some of the folks on the various forums I came up with two options: 1) replace the brake caliper with a smaller caliper and 2) replace the rear master cylinder with a larger piston. Since the piston was significantly cheaper than getting 2 brake calipers I decided to replace the MC with a 7/8th inch piston (originally 3/4 inch) which has been a great solution so far and has allowed me to run a much more balanced car at the track.
If you are building a car from scratch I would recommend going for a smaller set of calipers in the rear and/or smaller brake rotors both of which will save you some unsprung weight as well. I believe that the later Ultralite owners went to using stock 12-inch Subaru rotors in the rear which sounds like an economical solution as well. If you have a car with the original setup I can say that this solution of larger MC and bias valve has worked well for me.
“Diff”icult times
Thursday, February 2nd, 2012After 18 months of procrastinating about updating the blog about the Ultralite I figure its time to start putting pen to paper (or fingers to keyboard). Regular followers of the blog may remember that my Buttonwillow adventure ended with the Ultralite being flatbedded home as it looked like on of the two bolts holding the diff in place had backed out and gas tank prevented me from doing a roadside fix. I was thus still quite happy on the truck ride home as I thought it would be an easy fix and I should be back on the road soon – little did I know that I was in for some “diff”icult times.
The first thing to do was to empty the fuel tank and then remove it. As you might see from the residue above, the gas cap had been weeping fuel for a while and I figured that this was a good time to replace the gasket around the filler and see if that would fix the problem. I stuck my hand into the empty tank to see what size spanner I would need to remove the nuts on the cap fitting when I was shocked to discover that the cap ring was attached using just sheet metal screws with no nuts or backing plate inside the tank. While I could probably have fixed the issue fairly easily, I figured I had ridden my luck hard enough by tracking such a shoddy fuel setup and decided to go with a proper fuel cell instead. I gave Fuel Safe a call and they were able to create a custom bladder that fit inside my existing tank. Not only was the new custom cell much safer than the original setup but it has a proper racing collector which meant that I could ditch my external surge tank setup and save some weight. If you are looking for a custom fuel cell I highly recommend Drew Barney at Fuel Safe who was the guy I dealt with to create the setup below.
While my tank was at a Fuel Safe, I got busy actually fixing the diff mounts. Removing the gas tank had shown that the bolt had not backed out and instead had snapped from the torque. After removing the bolt and drilling out the snapped section in the unit I found that both rear bolts were metric grade 8.8 which sounds fine but actually equates to SAE grade 5 which is not what you want for something load bearing like this. I swapped both the bolts with metric 10.9 grade (equiv SAE grade 8) hardware and refitted the fuel cell thinking I should be good to go. However as soon as I backed out of the garage I heard the clunk from the drive train which meant that things were still not ok.
Pulling the center console off the shifter area showed the second problem (above). The front mounting point was created by welding a single mount onto a cut down version of the differential member assembly from a Subaru legacy. This mount was attached to some very thin metal and had basically ripped itself loose from the member assembly. After speaking to other Ultralite owner I found that this was a common failure point and needed to be reinforced for track cars in particular. I thus had a thick steel plate welded to the existing assembly to moth create a new mount point and also spread the load more widely on the Subaru part (see below).
Talking to the other owner also brought out that the diff bolts breaking was a common occurance and that many owners had created a brace that attached to the frame and helped spread the engine torque loads beyond the two diff bolts. Rob at Dietschwerks created this brace for me that had been on my car for over a year now and has been through several track days with no issues.
If you are an Ultralite owner I recommend that you check that you diff bolts are metric 10.9 grade and also create a diff brace for your car to avoid the painful debugging process that I went through.
The road from LOG 31 (Video)
Tuesday, January 31st, 2012Timelapse video of 3 Elises driving back from Lotus Owners Gathering 31 (LOG 31) in Vegas back to the Bay Area through Death Valley and Sonora Pass. Route chosen by Steve M and video by John Z, I just tagged along to make up the numbers 
It was a spectacular drive with Sonora Pass (skip to the 3:10 mark in the video to see footage) with almost no traffic and excellent asphalt quality. The pass is closed for significant portions of the year due to snow so you should call ahead before you make the journey. Full route info below:
Lotus Management on the Future of Lotus (GGLC Exclusive Interviews)
Monday, November 29th, 2010Cross-posting the interviews I conducted for the GGLC at the LA Auto Show and originally posted on the GGLC blog:
GGLC attended the North America launch of the new Lotus range at the LA Auto Show and got a chance to speak to senior management about their plans for Lotus and the challenges in launching 5 new cars in a short span of time. Short descriptions of the interviews and their major points are below but we recommend you watch the actual videos to get a sense about the future direction of Lotus
First up we spoke to Dany Bahar, the CEO of Group Lotus about his vision for the future of the company and why they were launching so many cars in such a short timeframe. Major points that he confirmed were:
- Not all cars will be going to aluminium skins, the Elise will remain a composite body
- Motorsports activities will include Evora GT4, Evora GT2, IndyCar (bespoke engine and aero)
- Simultaneous worldwide launch with an intended volume of 6-7000 cars per year
Next up was Donato Coco, Head of Lotus Design and the man behind the 5 cars on display. He spoke to us about the challenges in designing iconic cars like the Esprit as well as the goals for the design language for the Lotus range. Our favorite quite here was that the design for the new front ends has been inspired by the original Lotus Seven and if you look at the cars (especially the Elise) it does actually come through.
Finally we spoke to Wolf Zimmermann, CTO of Lotus about the challenges in rapidly developing 5 new cars. This was a great interview with reasons behind various decisions and we recommend you watch the whole video below. Significant points include:
- Aluminium bodies are required because composite cannot provide the required quality and shapes for the new designs
- Engines are not yet confirmed but will be decided in the next few months
- VVA architecture and manufacturing will have to be upgraded to meet targets
- Lotus Engineering is already involved in some of the design processes