Talk Morgan Forums Morgan Sports Cars Morgan Plus Four, Supersport & Plus Six (CX & CXV Generation Vehicles) Plus 4 CX - Initial Thoughts

and just a single inlet air compressor outlet port.

Thanks, John,

I learned about scroll compressors as an interesting anomaly when I was studying gas turbines at USNTPS. Clearly, I should have done more research - I have never heard the term being applied to turbines, but marketing people use a lot of - er - unusual terminology.

I copied my posts to Peter Ballard, for a sanity check and comment, but I presume I should not post his replies here though they are all jolly interesting. We are missing a lot of expertise here with the embargo on commercial members. One thing that did occur to me is that I do not have any data on wheel rate (spring rate at the wheel). If any TM member would like to measure it (you will need a 350 kg or so garage or personal weight scale) and I can provide the technique - I will get around to it sooner or later. I wrote to Nitron asking for details on spring and damper but received no reply…

And if anyone has a Plus 4 with the Dynamic Handling package with the rear anti-roll bar, let me know if you are willing to get data on roll stiffness using a slow drive over speed bumps.

The URL for the BMW training site is: https://bmwtechinfo.bmwgroup.com/#/login, and it costs £32 for access for a day - but you can short circuit the site and access the manual for the B46/8TU engines using this link. https://bmwtechinfo.bmwgroup.com/tech_training_manual/ST1837%20B46TU-B48TU%20Engines.pdf.

Regards,
David Poole

For my BioChem Eng BSc in the 70s we had to do thermodynamics. Not a favourite subject and as we headed for the course exam the lecturer said " every year I set a question on compressors either piston or screw (scroll). Last year it was screw compressors". I scrapped an honourable pass.

Hi David, what very interesting stuff, although I don't mind admitting I probably understood about 25% of the technical side, however, having recently moved over to a 300 mile old CX, with Nitrons and probably a rear a/r bar, not sure yet as I haven't looked, from a Trad ARP4 and previously 2 CSRs, a 260 and a 200, but what you say echoes my own less expert feelings, in that the standard damping is, I feel a little on the hard side, and I am going to be softening the front first for the same reasons you state.

The rear a/r bar is interesting, I had a Caterham HPC some years ago, which I used to sprint and hillclimb and found the a/r gave snap oversteer, very disconcerting, so I just disconnected one side and the handling after that was perfect, so I'm not really sure if the rear bar is actually necessary? A bit like the 6 speed box on the CSR, in which the ratios were so closely stacked and the 2.3 Duratec so torquey that you only really needed 3 of the 6 gears. I used modified 5 speed type 9 boxes with longer 1st and 2nd ratios on both my CSRs and that was perfect.

I wasn't aware of a ban on 'commercials' giving tech advice (SiFab used to) I thought it was just the pushing of sales of their brand ?

Simon, (moderator) could you comment please ?

In case anyone has an interest, this should be the link to the Plus 6 B58 manual: B58

And here is the 2 l B48

Hello Paul,

That is an interesting post - racing the CSRs must have been fun. Your comment about snap oversteer is interesting too - I have not been able to find information on the HPC tyre sizes, but it seems unlikely that the rear ones were as wide as on the CSR 260. The main difference wider tyres bring is smaller slip angles for the same side force, so wide rear tyres increase static direction stability and this may need a rear ARB to reduce it and make the car more agile.

It seems that I can quote Peter Ballard without compromising TM rules. He says that Nitron have a reputation for setting their dampers stiffer than SSL, so it seems worthwhile to try reducing damping by a couple of notches and seeing what effect it may have. An easy way of checking it is to find some speed bumps and take them at a slow speed, but fast enough to drop the car off them - this will act as a forcing function and you can observe the number of overshoots. You can also drive over speed bumps with just one set of wheels, pause on the top, and observe the roll angle. The height of the speed bumps and photo through the windscreen of the roll angles would be useful. If you have a rear ARB they will probably not be much difference between the front and rear, but if you do not you can expect a lot more roll angle from the front.

I bought my car Williams, and they turned out to be an excellent dealer. They race two teams - Caterham and Morgans, including a CX, and have a Flat Floor capability. I will try and persuade them to get wheel rates and roll stiffness specification, which would provide some light on the rear ARB. They fitted one to the racing CX, but have not yet tried it out. They had to drop the rear subframe, modify it, fabricate down links but I am not sure if they had to modify the rear suspension to make connections for them. They offered to fit one to my car when they were fitting the Nitrons, but I was a little cautious about it. More data would help… and I am curious to find what your comments are.

All the best,
David Poole

Hello David, I'd rather not deviate from the content of your excellent post re Morgan Plus Four ownership; however, did not want to ignore your question.

Historically, the commercial policy relates, primarily, to people who joined to hawk their wares and added little to the community and, in many cases, detracted from it. In latter years, it has been expanded to include people trying to drive traffic to sites that monetise content, be it directly or indirectly. As I am sure you can imagine, it needed to be a blanket coverall because otherwise, those who want to benefit from the community but detract from it are often the quickest to point to the lack of rules that stop them from doing what they are doing.

With all of that said, we take a pragmatic view on the above and my determining factor is always: does this aid the majority of the community and assist owners of Morgan vehicles. We have members who sell small parts that help other owners keep their cars on the road, we have artisans who mention and announce their products via TM and we have small businesses who offer advice and, at times and where appropriate, mention that they can help. As you can imagine, it is always a balance but TM generally operates in a genial and respectful manner and those who recognise they have a commercial product or service, which is relevant and could benefit the community, message me to discuss it. In doing so, more often than not, we agree something that benefits the community and allows the person to openly discuss what they have to offer.

As for a dedicated area, each time it has been mentioned to the forum, the general consensus, driven by the community is 'we would rather not.' With that said, people are also thoughtful and recognise that running TM, and keeping the lights on, isn't inexpensive; therefore, they appreciate that this may be an avenue that needs to be explored at some stage.

Hope that answers your question but feel free to PM directly if you have any others as I'd rather not detract from your interesting post on your CX ownership.