Firstly, apologies, I know this has been covered a few times before but I have some questions...

I have a 2.0 Duratec with Titan Roller Barrel TBs. They came new from Northampton Motorsport along with an Omex 600 which they kindly put a map on from a similar setup.

Quick question is what is the best (lowest) idle I should expect with this setup? The very best I can get when hot is around 1000-1100 but quite erratic.

The history...

It started first time and has always run super sweet when its warming up and even runs nicely when it moves off the fast idle which runs to 60DegC. However when it warms up above 85-90 it all goes wrong. The idle is all over the place.

Ive checked the balance with a synchronometer (around 4ish Kg/Hr), ive done the static setup as per Caterham instructions (6mm open on front of barrel) and followed the Omex setup for scatter idle - take off idle, set manually to 150rpm above target then switch idel back on.

As it came the idle was anywhere from 1000 to 1200+ and occasionally would 'run away' to over 1600.

The Idle Scatter Spark Table had no correction for +rpm so i copied the-rpm figures but negated them and they run upto -5.89. This did seem to help and by setting the target rpm way down to 800 I can get it to idle at 1000-1100.

I do fully intend to take it to Northampton Motorsport to get it properly setup but 1) Wanted to sort anything first if there's a problem elsewhere and 2) Wanted to get it MOTed locally to see if I get lucky with emmission first, that way I can IVA and then drive to NMS.

Hi There

Have a look at the sensors and the all variables, when it's warm what is the air temp sensor reading. The air temp will provide fuel correction and could cause the issues you are describing...also check the TPS is reading correctly....

That is where I would start.

Cheers

Ian

Thanks Ian TPS is all OK but havent air temp beyond start up.

I meant to also ask what the AFR is doing as this is another clue.

Cheers

Ian

Is that in the fuel map?

Check for air leaks .

Pretty sure its not an air leak, at least between the TBs and the head. I put a piece of wood across the TBs and it immediatley stopped the engine.
All very frustrating as its the very last thing I need to do before IVA.
One thing I did notice a couple of times was the fuel tank made that noise you hear when theres pressure or a vacuum in a tank. I double checked the breather valve to make sure its round the right way.
Also ran with the cap off and it still wasnt idling well so not sure its a factor.

Flak Monkey had the same issue a few years ago, I'm sure he gave up and went back to conventional bodies:

https://www.locostbuilders.co.uk/viewthread.php?tid=131856&page=1

Unfortunatley, because the Duratec was mounted slightly canted over there's no room for other TBs so im stuck with the Titan ones.

I have the same TB but only managed my first start this weekend so not tried getting up to hot idle yet!

I have stood next to a many Caterham Duratecs using these TB and they idle fine so it Has to be possible. I also have a friend that had some on a Duratec powered Elise and he eventually got them to work with an Emerald ECU so that would also indicate its possible.

Can you tell me when you set it up what are your Raw maximum and minimum figures for the TPS in the ECU?

Check for air leaks using WD40 then check the balance of the TBs and also for slack in the throttle cable/linkage Over advanced ignition timing at idle will cause a fast idle speed

Raw Max and Min on the TPS are 20 and 223.

Did just notice that the throttle setting doesnt always return to 0 and sometimes is around 0.12%. I wonder if thats a factor?

Id did try squirting wd40 around the TB barrells but didnt notice any changes.

quote:

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Originally posted by ChrisJ15
Raw Max and Min on the TPS are 20 and 223.

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Cant remember TPS make, came from Northampton Motorport with Titan TBs.

Plan is to trailer it to NMS now.

quote:

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Originally posted by ChrisJ15
Cant remember TPS make, came from Northampton Motorport with Titan TBs.

Plan is to trailer it to NMS now.

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Gulp, just been quoted £157 (inc VAT and delivery) for 1 TPS the same as yours!

Need to get an answer from Omex if having a narrow TPS range is going to really make any difference before I swap this over

quote:

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Originally posted by peter030371

quote:

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Originally posted by ChrisJ15
Cant remember TPS make, came from Northampton Motorport with Titan TBs.

Plan is to trailer it to NMS now.

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Searched on here and you have previously said its a 'RP5110-100 from Active Sensors' so I will try and get one of them to increase my TPS range

When you get NMS to set it up I would love to hear how you get on and what it ends up like?

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Just thought I'd give an update for this thread in case others have same issues.

Went to Northampton Motorsport yesterday for rolling road session to setup ECU and check emissions and all is sorted and OK. Car idles steadily at 1,000rpm and emissions fine.

Havent done this before so I had no idea what to expect. All in all a very pleasurable experience. I would thoroughly recommend NMS. They are all very helpful and knowledgeable and charge a fair price too.

Very happy with outcome too as im getting 196 bhp from my Duratec with a cat so couldn't be better really!

My similar spec build (no cat though) is booked in for a mapping session at ATSpeed next week, be interesting to see what they come up with.

They didn't like the fact I have roller barrel throttle bodies and did say there previous experience (from one car) is that they set the idle and then a few days later it is out again. They don't know why though. Mine currently idles at circa 1000 rpm and it seems fine to me so we will see after its fully setup

Remember to give as much banter as you get when you visit the boys at Atspeed

quote:

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Originally posted by jeffw
Remember to give as much banter as you get when you visit the boys at Atspeed

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What can go wrong, you might want to leave mentioning my name to Colin till you arrive lol...

Hi ChrisJ15/peter030371,

I'm trying to get a decent idle with these TBs on standard 2.0L Duratec and wondered whether you know what Idle Timing Advance was used by Northamption Motorsport and ATSpeed?

This is on my assumption that the key is Timing Advance (or in reality Timing Retard) - any info would be much appreciated.

Cheers
Pete

quote:

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Originally posted by pjay
Hi ChrisJ15/peter030371,

I'm trying to get a decent idle with these TBs on standard 2.0L Duratec and wondered whether you know what Idle Timing Advance was used by Northamption Motorsport and ATSpeed?

This is on my assumption that the key is Timing Advance (or in reality Timing Retard) - any info would be much appreciated.

Cheers
Pete

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Thanks, that would be great. Are you running Alpha-N or Speed Density based map?

I never got mine to idle less than 1200rpm with roller throttle bodies, fine for a track car not for the road - gave up and went to Jenvey DTH with the rotrex.

The reason being the clearance around the roller portion of the TB is large enough to allow significant air flow, even with them closed right off you will bypass enough to idle high. The manufacturing tolerance differences are enough to vary that idle speed by 100rpm or so, and you can slow it down more with some silly timing maps, but it's covering up a flaw in the design. Roller TB's just aren't meant for low rpms - infact the airflow through them is awful until you get over 50% throttle.

IMO roller TB's are great on a track car, but a bad choice for road use.

That reminds me I haven't looked at this yet, will try and do it at the weekend.

I have read lots of stories of poor idle ect with roller barrels but >300 miles in with a mixture of road and track use and on a standard engine (no lumpy cams) mine idles around 1000rpm just fine. Doesn't sound overly fast and doesn't change hot or cold (so far).

So much of my car is a compromise on the road (gearbox noise, no windscreen, poor view in the mirrors, no seat padding and so on) that this compromise doesn't bother me when it does give a little more power on the track at WOT

Based on Chris's initial comments I dug into the OMEX 600 manual and the section on "Idle Strategies" & "Without air bypass idle motor". It looks very likely that ignition retard is being used in your set ups to 'restrain' the Idle RPM when hot but give a fast idle when cold:

"As the engine is being given more air than is required to idle the engine when warm it retards the ignition whilst in the idle condition to maintain the target engine speed. When the engine is cold it requires more air to idle and so it benefits from the extra air, the ignition is advanced whilst in the idle condition, and the engine has an improved cold idle speed."

To confirm the Ignition Map and the Idle Scatter Spark Table can be looked at.