Chris's new build of an MX5 based car

[CTWV50]

Great day today, youngest off spring's birthday and we were all off to the "Climbing Hanger" 8 miles away with some school friends. We were a seat short in the two cars that were taking everyone, so I thought I'd take the birthday boy in my contraption as the weather was excellent, no chance of rain. Nice slow leisurely drive though busy roads, got lots of attention and swarmed my teenagers at one point asking lots of questions. Just need to sort the creaky suspension and a rear cover. Suspension, a job for tomorrow, I've got some lithium grease somewhere.

[CTWV50]

One of the first jobs I did when I started building the car was to push in the bushes on the suspension. I did it without grease, I can't remember what my thinking was.

So I greased up the rear suspension yesterday morning using some teflon grease I had, I use it on my mountain bike as it's waterproof (you'd think all greases were waterproof, they aren't, apparently). Took it out a spin and OMG the difference. The rear end is completely silent and silky smooth over bumps, around corners the rear really hangs in there but without oversteer. Before it was good but felt skittish going from under to over steer in the corners. I'm very pleased with it but i think I could do with 300lb springs in the rear rather than 250b. With me and my 11 year old in the car I felt us going onto the bump stops occasionally.

Still got that stuttering at 5000rpm, it's occasional and manages to get over it in 1st, 2nd and 3rd but after 15 minutes driving it will not go past 5000rpm in 4th gear. I think this suggests a fuel shortage or pressure issue but have a feeling it's coil pack related. Might hook up a pressure gauge to the fuel rail and see.

[wylliezx9r]

Originally Posted by CTWV50

One of the first jobs I did when I started building the car was to push in the bushes on the suspension. I did it without grease, I can't remember what my thinking was.

So I greased up the rear suspension yesterday morning using some teflon grease I had, I use it on my mountain bike as it's waterproof (you'd think all greases were waterproof, they aren't, apparently). Took it out a spin and OMG the difference. The rear end is completely silent and silky smooth over bumps, around corners the rear really hangs in there but without oversteer. Before it was good but felt skittish going from under to over steer in the corners. I'm very pleased with it but i think I could do with 300lb springs in the rear rather than 250b. With me and my 11 year old in the car I felt us going onto the bump stops occasionally.

Still got that stuttering at 5000rpm, it's occasional and manages to get over it in 1st, 2nd and 3rd but after 15 minutes driving it will not go past 5000rpm in 4th gear. I think this suggests a fuel shortage or pressure issue but have a feeling it's coil pack related. Might hook up a pressure gauge to the fuel rail and see.

I'm thinking of going to 300 lb springs on the back too (highlighted on a recent trackday). Alternatively I have been thinking about adding an ARB. Some people say you shouldn't need them but certain Caterhams come with them as standard. I'm probably going to try the springs first and if the ride is too harsh go back to 250 lb springs and add an ARB.

[CTWV50]

Originally Posted by wylliezx9r

I'm thinking of going to 300 lb springs on the back too (highlighted on a recent trackday). Alternatively I have been thinking about adding an ARB. Some people say you shouldn't need them but certain Caterhams come with them as standard. I'm probably going to try the springs first and if the ride is too harsh go back to 250 lb springs and add an ARB.

It's not really a corning issue for me I'm just a bit heavier than your average bloke I think. Helps with traction though! (16 stone)

[flyerncle]

Believe it or not grease is composed of soap,so not waterproof,does clean your hands though.

[CTWV50]

Originally Posted by flyerncle

Believe it or not grease is composed of soap,so not waterproof,does clean your hands though.

You learn something new........!

[CTWV50]

As I am still at a loss as to the lack of power occasionally over 5000rpm I thought I'd hook up a gauge to measure the fuel pressure.



Went out to test it and low and behold the power stutter returned after 10 minutes of driving. Fuel pressure remain solidly at 40psi (3bar), after a little thinking as I was driving I thought this must be coil pack related then but then thought what happens if i turn the lights off during a stutter ( I have been driving around with the lights on for safety/visability). Well the car took off like a rocket when I turned off the lights and when I turned them back on the car started struggling again. Now is this coils, the alternator, or could the tiny battery be the issue. I'm pretty sure the battery does nothing really when driving other than charge, car always starts first time so does that rule out the alternator. SO coils then?!?!

[Ianr]

Any idea what your voltages are Chris, I know this may sound daft but it seems to me you have a voltage drop, perhaps a faulty earth somewhere????
Ian

[CTWV50]

Originally Posted by Ianr

Any idea what your voltages are Chris, I know this may sound daft but it seems to me you have a voltage drop, perhaps a faulty earth somewhere????
Ian

yeah I think there is a drop in voltage might try a few tests tomorrow. But with the time delay of around 10-15mins I think the lower voltage is highlighting a weak coil pack when it gets warm. But could be a faulty alternator or regulator. hmmm

[TheArf]

It's all down to that electrickery stuff it don't play fair, unlike mechanical trickery, it hides out of sight.

arfon