The XJR-15 race car took me into uncharted territory today. I have owned many high performance cars over the years as well as doing just about every conceivable mechanical job, from rebuilding gearboxes to setting up the engine timing on a quad cam, but I have never set up the suspension on a car. I felt that the front of the race car was set too high which caused it to feel quite unstable on the motorway at speed. I borrowed a set of scales from a friend in order to lower the front of the car. I lifted the car off the ground and put one of the scales under each wheel. I then set the scales to zero before lowering the car on to them. The first thing I checked was the weight of the car. Including fuel, the car weighed in at 1064kg. I estimate that the car had about half a tank of fuel, so about 55 litres. A litre of fuel weight .711kg, so approximately 40kg of the overall weight was fuel. This suggests that the race car weighs about 1025kg, compared with the 1050kg in the spec. It might be that there was more than half a tank of fuel which would mean that the actual car weighed less. I make this point because I also weighed the LM and this came to 1084kg on the scales. My guess is that the weight in the spec is for a road car which has a lot of additional fitments such as the bench seats, the air con unit as well as the condenser and fan units. The LM is lighter than a standard car, so I am allowing for this as well.
Back to the set up.... I lowered the front of the car by about an inch, it is still a few mm higher than I would like, so I will probably take it down another step. The interesting and not so easy part of the set up was the cross weight. This deals with the pitch of the car when cornering and effectively adjusts over-steer and under-steer. I compared the readings on the scales between the LM, which I think is well set up, and the race car. I now have an approximate weight distribution of 60% rear and 40% front, but the cross weights are completely different between the two cars. One of the things I absolutely love about the 15 is that it provides such insight into what an F1 driver does on a race weekend. Yet again the 15 has challenged me as a driver, not just on the road, but now testing my ability to understand car set up. Whilst I have a lot to learn and will undoubtedly need to seek advice, the whole engagement with the car is on a different level to merely owning a supercar. It can only be described as fascinating.
Having lowered the front of the car, I then took it on a test drive. On the way to the motorway I took the opportunity to practice changing gear up and down the box as much as possible. I have to say that changing up the box is far easier than a normal synchro box. The speed of change is awesome. I would say that I can get this right 99% of the time now and my speed of change is getting quicker and quicker. The down shift is a bit trickier. There are essentially two aspects to this, braking, then down shifting and braking and down shifting at the same time. The technique to brake and then down shift is not too bad. This involves loading the gear leaver, brake, then left foot on the clutch, right foot blips the throttle and slot the gear. This is not too difficult to learn and over time I have no doubt will become instinctive. The second technique involving braking and downshifting requires either left foot breaking or heel and toe. I will certainly need a bit more time to master this.
As I reached the motorway, I was in 4th gear, without thinking I floored the throttle and felt the rear wheels spin up, so had to back off quickly. On the motorway the car was very stable and lowering the front had the desired effect. I was also able to check the accuracy of the speedo. I had fitted a pulse generator to a half shaft and fed the out put through and multiplier. Checking this against the digital readout I have fitted, this indicates that the speedo is within about 3mph, so pretty good. All in all today was a very good day. When I was looking for a 15, everyone said buy the road version. Whilst I am lucky enough to have both, I would advise anyone looking for a 15 to absolutely consider a race car. It’s a very different experience and at the moment the race car is fast becoming my favourite. With its full race livery the crowds of people that gather around whenever I stop for fuel, it is certainly a favourite with them as well.

 

A few pictures

 

More pictures

 

From above

 

Trying again

 

Fantastic! Thanks for posting, wasn't the LM built as a race car originally and not a road car? if so what is the difference between your LM and your race car, apologies if this has already been gone over elsewhere in the thread. cheers Alan W.

 

Alan, there are a lot of small differences between the LM and the race car. Whilst there are believed to be circa 50 cars or so, there seems to be three variants. The race car, the road car and the LM. The body work on the road and race cars is more or less the same, at least on the outside. Under the skin there are differences. The road cars have inner wheel arch liners, whereas my race car has none on the front and splash guards on the rear. The LM body work is different to the road and race variants. It has a splitter on the front along with two additional air intakes. The rear wing has much higher pedestals and the pitch of the wing is also different. The rear screen is different on the LM in that it has three vents on each side, however the big visual difference is a roof scoop that covers most of the rear screen. My car was originally fitted with a roof scoop, but for some reason it is no longer there. I have some old pictures of the car with the scoop in place and the marks are still on the roof. I have sourced various suppliers that can recreate the scoop and make one for me, so hopefully next year it will be back in place. I have seen different pictures of LM’s which have further variations in the way the roof scoop has been made, so it may be that no two are exactly alike. The final difference on the body work is that on some of the LM’s there are no wing mirrors. I have seen one which has a different rear diffuser and four tail pipes which look quite cool. The interior of the three variants is also different. My race car has a single carbon fibre race seat and a large fire extinguisher where the other seat would be. My race car was originally fitted with a fire system, which I may have reinstated. Some race cars have two seats. The road car has a bench seat with a divider in the middle which creates two separate seats. They look quite plush and are well padded and covered in leather. The LM has two separate carbon fibre racing seats covered in a thin layer of leather. No padding. There is no air con or even a fan on the race car, but both road cars and LM have this. There are other small additions on the road and LM such as an interior light and of course pop up headlights. Road and LM’s have a handbrake and horn as standard, whereas I had to fit these to my race car for the Mot. The final part of the changes are on the mechanical side. The LM is a 5 speed synchro, the same as the road car, whereas the race car has the 6 speed dog box. There are a number of differences in terms of the engines and the engine management systems. The race car has a 6ltr engine with Zytek engine management, this is the same fitment on the road car, but I believe the mapping is different and I understand the cams are also different, but I am not certain. The LM’s were said to be fitted with 7.4ltr engines with down draught inlets. My LM does not have the down draughts and at the moment I am not entirely sure what size the engine is. It is possible that it is either a 6.5 or a 7 ltr version. The injection system has an extra injector on each of the inlet manifolds, activated by a cam on the throttle actuator. The engine management system on the car is Lucas. I think my LM was built in 1994, I am hoping to have this confirmed by AP Racing when I send them the clutch. It seems that all of the clutches have a serial number and were matched to each car when they were built. If the car is a 1994, it suggests that they evolved the cars as they were built over time. Certainly the changes on the LM are in many instances quite subtle, such as the steering wheel being closer to the dash, giving more space on the LM. The suspension set up is very different, probably to work more effectively with the aero pack. All in all the LM is a very different car to both road and race cars.

 

Thanks for the detailed reply. I find your insight very interesting and informative, but I am still a little grey on the LMs original purpose it sounds like a half way house / hybrid of the road car and the race car. Though I thought it was an extreme version of the race car. Or is it more like an XJ220S or F1 LM a racer for the road? I notice you say you have a racer and a road car so I take it the LM model is what you are referring to when you say you have a road car, herein lies my confusion!?

 

This is what I know about the LM’s, it may not be correct and perhaps others might clarify. The race cars per se were the original 16 or 17 cars that took part in the Inter-Continental Challenge series. These were the first cars produced (I believe). The LM’s were the last cars to be built. The propaganda of the day would have you believe that all the cars were sold straight away, but that is incorrect. The first cars were built in 1991 and the last in 1994 (or there abouts). Some say that there are 5 LM’s others say 12. Whatever the number, there are relatively few. It might be that there are 5 LM’s with the 7.4Ltr engine. As far as I know all of the LM’s ended up in Japan. They were built as road spec cars with air con, hand brake etc, but had all of the other changes I referred to. There is a white car in Japan that has been used in a race series with a lot of modifications and I heard that another car was cannibalised to make another race car. I think your comments about the XJ220S are about right. TWR put a lot of effort into the aero pack and the set up of the car. Whilst they retained the road car driver friendly additions, they also worked on weight reduction so the seats are much lighter than the standard road car. I think they also did some work on the cooling as well. Mine has an additional fan in front of the air con condenser. Another interesting modification on my LM is the ability to adjust fuel flow when driving, in effect the ability to turn up the power. At some point I hope to find another LM owner in order to compare notes.

 

Ah excellent, thanks again for the reply, now I understand my impression about the LM was incorrect, but thanks for clarifying. I hope to see it when you have the air scoop replaced! and good luck finding another LM owner.