Engine Runs At High Idle When Hot

[Glyn Harper]

Hello all..

Firstly, before I go into the detail, I'm not running a Lotus ECU I'm running an Emerald System M3D one..

The problem I'm getting is that when the engine gets really hot (when sat in traffic for example) the idle speed starts to creep up and up, whith the effect that the engine heats up even quicker.

The fans cut in and cool it, but it's not good.

It's obviousley down to my map, but i'm not sure how to change this.

The engine behaves perfectly at cold and normal warm operating temperatures. it's only when it's in traffic and the temp starts creeping up that it start happening, it get's worse as the temp rises until the fans cut in but they only bring it down for a bit and then it creeps up again as the temp rises.

The options I have are to change the fuelling or ignition at the part of the map where it happens (500-1500 RPM) but this may cause a flat spot when I pull away.

the other option is to meddle with the 'water temperature' settings in the map.. but then this will affect the whole map at the given temperature.

So, does anyone know much about how ECU's do their mapping, and suggest what I may try and change?

Cheers..

[Vulcan Grey]

Hello all..

Firstly, before I go into the detail, I'm not running a Lotus ECU I'm running an Emerald System M3D one..

The problem I'm getting is that when the engine gets really hot (when sat in traffic for example) the idle speed starts to creep up and up, whith the effect that the engine heats up even quicker.

The fans cut in and cool it, but it's not good.

It's obviousley down to my map, but i'm not sure how to change this.

The engine behaves perfectly at cold and normal warm operating temperatures. it's only when it's in traffic and the temp starts creeping up that it start happening, it get's worse as the temp rises until the fans cut in but they only bring it down for a bit and then it creeps up again as the temp rises.

The options I have are to change the fuelling or ignition at the part of the map where it happens (500-1500 RPM) but this may cause a flat spot when I pull away.

the other option is to meddle with the 'water temperature' settings in the map.. but then this will affect the whole map at the given temperature.

So, does anyone know much about how ECU's do their mapping, and suggest what I may try and change?

Cheers..

Does your car have the throttle jack capsule connected to the butterflies?

Mine started to stick, and it would high idle when coming off the highway, so I removed it (no EBPV anyways).

[Glyn Harper]

Does your car have the throttle jack capsule connected to the butterflies?

Mine started to stick, and it would high idle when coming off the highway, so I removed it (no EBPV anyways).

Hey..

no, mine doesn't have an ebpv or a throttle jacking solenoid.

it's a much simpler setup as the ecu controls the idle.

I'm going to have a meddle this afternoon..

Cheers,

Glyn.

[Paul17764]

Hey..

no, mine doesn't have an ebpv or a throttle jacking solenoid.

it's a much simpler setup as the ecu controls the idle.

I'm going to have a meddle this afternoon..

Cheers,

Glyn.

Hi Glyn, My GT3 started doing this today after a 40mile thrash, Ticking over at about 1500 RPM....Have you any luck with solving your problem yet?. Regards Paul

[Dermot]

Glyn,

Do you have access to the tables in your ECU.

Is there are target idle RPM vs. coolant temp table ?

You can look at some of the tables that are in the Lotus 4-cylinder ECU at:

http://users.ox.ac.uk/~ohare/ecu_tables.htm

[islandbloke]

Paul at South Coast in Douglas may be useful Glyn - although he's usually backed up with work...

[Glyn Harper]

I think I've sort of got there.. It's partly the target idle RPM settings (Cheers Dermot) but most of the problem was caused by the fact that the throttle cable didn't have any slack in it at all.

So, when the engine is cold, it's all ok. But when the engine gets really hot (the actual metals of the engine, not the water) then everything expands a bit.

As the throttle cable is clamped a fair way from where the inner cable connects to the actual throttle bodies, any expansion in the inlet manifold casues the cable to go tighter, thus opening the throttles slightly. I watched the settings for my throttle pot reduce slowly, after I'd turned the engine off.

I then slackened off the cable, and that's hopefully fixed it.

I'll just have to check now that I get full throttle opening. (or just run more boost instead!)