Very boring and technical cold start and mapping thread...

[Julian Thompson]

Working hard on a cold start map. Taken advice from Oily (thanks for your time!) and fiddled with the "Coolant temperature" injection settings.

 

I found that the lumpy, recalcitrant idle could be smoothed a lot by leaning off the mixture using injector trim. I am now working on transferring this trim gradually into the Coolant temp correction table.

 

I have 3 questions.

 

1) When ought I concern myself with ignition trim for coolant temperature?

 

2) I note that once semi warm, with no load (remember all my work so far has been with the engine cold and the car on stands!) but with the throttle part open, the engine seems lumpy and goes *quite lean* according to the lambda reading. How would I combat this, bearing in mind that enrichening the mixture in the correction table will impact the idle value at this temperature and spoil the low speed side. Surely I don't adjust DW's main map as this is perfect once we're fully warmed through?

 

3) The IACV setting range gives a matrix for -10degC, 0degC, 10degC, 20degC and 30degC. What happens once the temperature goes above 30degC? No matter where I set the 30degC to, the IACV always ends up showing 65 once the motor is warm. Why? and is this okay? For information, I have the IACV at 100% for cold start and on crank.

 

Many thanks for thinking about this and sorry to bore you if you're not interested!

 

Jue

 

Edited by - Julian Thompson on 23 Oct 2002 22:57:35

[V7 SLR]

Ju, I didn't mess with the coolant temp correction. There is already a relationship between the IACV opening and fuelling so I altered the IACV opening, increasing idle according to engine temp (so as to mimic a choke at start-up). In the end I actually had the IACV open about 95% at start-up, and tailed it off to normal idle once warm. It worked rather well.

 

Do you want me to email you my last map (don't use it though, it's set up for different injectors)?

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[F355GTS]

Ju

 

I don't think it's boring at all, when you've got it all sorted and I get my Emerald I shall be giving you a call !!!

 

Mark

[Peter Carmichael]

The emerald applies different amounts of the coolant correction depending on revs. In the additional settings there is a table that controls this. Settings are 100% at idle dropping fairly linearly to 15% at ~5000rpm:

 

Coolant correction:

100 100 100 90 82 77 73 56 36 20 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15

 

[Peter Carmichael]

The IACV sounds like added complication and is unnecessary. Rock solid idle and easy starting is possible with just advance control.

[V7 SLR]

I agree Peter, but given the SLR is supplied with Rover TBs, the IACV can be made to work OK quite easily and entirely without having to lift a screwdriver (configurable entirely on the PC).

 

Saying that, I've moved to a set of Jenveys now, for a few reasons:

 

1. The Jenvey throttle plates are closer to the engine so hopefully I'll get better throttle response. there was nothing wrong with original throttle response but perhaps it'll get even better?

 

2. The Jenveys offer a simpler setup. There's no IACV although it worked OK, but now I can take out even more engine loom cabling.

 

3. The whole assy is smaller overall affording me more room to work around them. I had to take the head off altogether to remove the old TBs because the bolts were so inaccessible.

 

4. I got the Jenveys cheap. An important consideration.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[Mike Bees]

FWIW my engine needs surprisingly small amounts of coolant temp. correction. If I had the laptop handy then I could expand on that with some numbers...

 

Mike

[Tony Martyr]

With the TB set-up being fitted by Nigel - no IACV - but with dta ECU by coolant compensation map adjustment is:

Temp C Fuel comp% Advance Comp %

0 35 20

10 30 15

20 25 13

30 20 8

40 12 4

45 8 1

50 7 0

60 5 0

This starts well and idles from cold - just

[Blatman]

Just trying to align Tony's posting..........

Temp C Fuel comp% Advance Comp %

0 35 20

10 30 15

20 25 13

30 20 8

40 12 4

45 8 1

50 7 0

60 5 0

Wel, it sort of worked...............

 

Edited by - Blatman on 24 Oct 2002 20:56:04

[Julian Thompson]

Hey guys, thanks very much. Lots of thought gone in here and I appreciate it.

 

Please help some more now 😬

 

SO.

 

Peter, thanks for the tip about the RPM compensation. Mine was untouched and looked very rich above the idle - i've copied in your numbers but had no chance to try them yet.

 

I've also checked the figures Tony gave and Blatman laid out. My fuel correction is encouragingly close to this but I have only 8% advance where Tony has 20% ; I DO have the "use advance to stabilise idle" option checked ON.

 

Ought I use more advance then and why?

 

In a similar thread a while ago I remember Peter explaining that the IACV was not required. I understand that I ought to lock the IACV to, say 65 and leave it. I'd then struggle on cold start, though. Is this related to the lack of advance?

 

I'd love to bin the IACV and make a nice finger screw idle bleed that weighs about 2 grams.......

[Mike Bees]

Julian - be aware that Tony's advance compensation is a %, whereas IIRC in the Emerald it's a number of degrees. You *don't* want 20 degrees of extra advance at any temperature...

 

At idle the ignition temp. correction is irrelevant if you're using the "advance to stabilize idle" option.

 

Mike