Maxed my car a few days ago...

Purely in the interests of science, I ran my car pretty much upto vmax a few days ago. When I stopped a few miles later, the idle speed was very slow and lumpy. It almost stalled. It’s been running perfectly ever since, though. Any idea what would cause this?

The engine is all standard apart from Janspeed SS exhaust, cat baypass, and the Lotus breather kit.

Forgot to mention the engine is in standard 190 form.

My car often takes a bit of idle time to get back normal after a hard track session.

Yes, I think I’ve noticed this before after giving it a thrashing. Only thing I can think of is that it’s using fuel so fast that the petrol tank is getting depressurised and thus reducing the flow. That’s probably a load of bollox though

I think that is a load of horlicks

I’ve seen this with the lotus ECU on S160’s as well, mine used to do it after a hot track session… Dunno if the intake temps when you dtop are just so high that it retards the ignition so much it really does struggle! Would be the only logical explination to me.

Well, I certainly prefer your explanation to mine. Basically a “TADTS” is better than a “Low fuel pressure problem”

Incidentally, my “research” confirmed that the UCR gearset matches my car perfectly: The rev counter was reading 7800 rpm in fifth.

And… what sort of speed did you get?

I can’t remember what the speedo was reading, I know they lie anyway, but it was in the region of 140mph.
A quick calculation based on a rolling circumference of 1921 mm (plucked out of a demon tweeks catalogue) would suggest 136mph.
Don’t know if you need to add a bit more for tyre expansion at that speed
There was maybe 1 or 2 mph to come but there was another car ahead so I backed off.

And… what sort of speed did you get?

70 mph exactly occifer

brendan what"lotus breather kit" are u using?

mine does 130mph in 4th!!

Russ C, I don’t know the details of the breather kit, it was an option from Lotus for the VHPD motor. I think it’s officially designated as a 340R option. (Says 340R on the silicone pipes). It includes the pipes and an aluminium catch tank.

Koopa, yup, you’ve got the standard gearing. IMHO the car is way over-geared as standard. You barely even use fourth on track, let alone fifth. With the UCR set you can only do about 110 in fourth.

130mph in 4th must be right at the limiter, like 8000rpm!

I get into 4th pretty often on most circuits I’ve been to, Brands, Goodwood, Bedford definately, that’s 125 down the back stright in 4th and it doesn’t sound to healthy to me

i think it was about 7600rpm it was at 130! the car was loving it, sounded perfectly happy


Weird… I wonder what box I have then… 4th will basically get to about 120 - maybe 125 going up to 8k rpm but then 5th is so much longer, will drop down to like 6k or something…

According to my figures, 7800rpm equates to:
(Standard box)
1st 45
2nd 75
3rd 101
4th 128
5th 156

(UCR box)
1st 47
2nd 73
3rd 91
4th 111
5th 136

So that’s reassuring.
When the car was standard (177) I managed to get to an indicated 135 MPH at about 6800RPM in fifth.
So it was about right then

That’s a very accurate speedo Uldis.
Also suggests there’s not much differerence between the 177 and 190 spec.


Could you ‘lumpiness’ be due to wrong type or incorrectly gapped plugs ? they might have been running too hot ?.. may also have been ‘carbon cleansing’ from top of Pistons etc ? How old are yer plugs ?

Hi Rox, I think the plugs are fairly new. They should have been replaced when the engine was rebuilt recently. It’s a good suggestion, though. I’ll get them checked. The idle seems to be getting pretty irregular now. I suspect a dodgy sensor somewhere.