Well I still have idle problems.

Refitted everything again with no sealant or anything. Idle was a little rough to start with difficult to tell if it was hunting, if it was it was small.

However I still have a 1300rpm or more idle

So I now either have one massive air leak across all cylinders or no air leak and a still high idle.

Spraying brake cleaner in the each barrel results in the idle speed slowing down. Spraying it around all joint has zero effect.

Thats with 4 deg ignition advance too.

I need of a little motivation now

quote:

---

Originally posted by flak monkey
I need of a little motivation now

---

I've got no advice on your dodgy idle, but hope you stick at it. if these things were easy to build, vevry other f@$ker would have done it.

the fact its hard puts you in to an exclusive club once you've cracked it. keep at it buddy.

Didnt Nothampton Motorsport shed any light on it?

You could take a brake from yours and finish mine

time to call the rolling road???

Did you change compression ratio ?
Did you change camshafts ?
Did you balance the throttles ?
How much vacuum on the intake and are the sensors working OK (throttle position, intake manifold pressure, cooling temperature sensor) ?

Perhaps you can monitor whether your engine is running lean or rich with a lambda sensor to see there is something wrong with the fuel injection ?

[Edited on 18/3/10 by Breaker]

could you put a bit of wood progressively and slowly covering all four trumpets?

Ie take the roller barrels out of the equation by slowly restricting the air to all four barrels - if you can get the idle down by manually restricting air flow to all four you know its air past the rollers.

Then i'd play at restricting each barrel and combination of barrels to figure out if its an issue with all four or just one.

(i've never played with roller's but have you balanced them all so they all open at the same time now you've disturbed them taking everything off?)

you should have stuck with the pinto

sorry mate no help i know

chin up and keep smiling

take a half hour break, have a coffee and a biccy and go back, start at step one and work logically

All the best!

Please humour me for a while, on your last post you said the carb roller/barel was round on the inlet and oval in the outlet of the throttle body. If the barrel were rotated 180 deg making the oval side the inlet to the throttle body due to the shape of the oval when the throttle was closed a smaller amount of air could be drawn in so reducing the idle speed. This is how some model aeroplane engines were configured. I appreciate this might not work in your situation but it might be worth investigating.

It looks like you've answered your own question David, if spraying the cleaner into the barrels slows the tickover, it is temporarily reducing the clearences, and reducing the airflow.

I know you've tried just about everything else, but altering timing to reduce tickover is not the way to go, that is making the engine run inefficiently by not full burning all the fuel and washing lubricant from the bores increasing engine wear.

The advantage of these bodies is only realised at WOT, how often are you up there on a road car? would the supplier swap them for butterfly bodies?

Rolling road isnt an option at the moment. The cars not even driveable as it is. Plus no one will touch a megasquirt car unless is running pretty much spot on to start with.

Compression ratio was changed from 10.8:1 to 10:1

Cams are new but standard timed as per standard Ford procedure.

Throttles are roughly balanced - from experience if they are poorly balanced idle speed will decrease rather than increase. They are in pairs (like webers) so there is only one balance to set and like I say, its very close as is.

Vac is about as good as I would expect, around 65-70KPa at 1300rpm.

Lambda sensor is already fitted and talking to megasquirt. AFR is around 13 at the moment, which is still too rich.


Turning the roller through 180deg is not possible and not correct so its a no go.


If its a big airleak causing the high idle I am f&$(ed if i can find it.

quote:

---

Originally posted by Bigheppy
Please humour me for a while, on your last post you said the carb roller/barel was round on the inlet and oval in the outlet of the throttle body. If the barrel were rotated 180 deg making the oval side the inlet to the throttle body due to the shape of the oval when the throttle was closed a smaller amount of air could be drawn in so reducing the idle speed. This is how some model aeroplane engines were configured. I appreciate this might not work in your situation but it might be worth investigating.

---

If i cant get it running with what I have then I have zero chance of making it to Stoneleigh. Theres too much time and effort involved in changing from the roller throttles.



They wouldnt swap them anyway - I have drilled 4 MAP take offs in them to start with, and I also didnt buy them new - well they are new but not first hand should I say!


PS also looking at the best part of £1k's worth of throttle bodies sitting on the side of the engine at the moment

[Edited on 18/3/10 by flak monkey]

Have you tried running them with the pairs disconnected? another long shot, but is one pair holding the other pair open? You'd only see that with a gauge on each map take off.

The linkage is in the middle of the pairs and they interlock so there is no option of disconnecting the pairs sadly

OK, this might sound stupid, but to prove air is getting by the clearance in the barrels, could you temporarily seal all but the opening at the bottom with plasticine?

You couldn't operate the throttle but if you get a decent tickover, the issue is identified if not rectified.

I could and thats something I can try tomorrow afternoon.

I am just stumped as to where else there could be air getting past in high enough quantities to give such a high idle.

Hi David, just one more suggestion, although you're probably into 'suggestion overload' by now...

The idle bleed screws you mention - you say they are screwed right in, but are they in fact fully closing the air bleed? Are they fitted with springs behind the heads, if so are you sure they're not bottoming on the springs? Easily checked by temporarily removing the springs if fitted.....

As said by many others though, look for nothing else until you've fixed the air leak........

The bleed screws sit on tapered seats in each throttle body and simply have a lock nut, pretty simple really. They are all screwed down tight and appear to seal.

Its at this point I wish I hadn't bothered with roller barrels and just fitted jenveys in the first place Or even just a plenum and mahoosive single throttle body

[Edited on 18/3/10 by flak monkey]

Ok, how about this.

Pressure leaks are much easier to find than vacuum leaks, so rotate the engine till both valves are closed, then via an adapter of some sort in the plug hole, pump some pressure in and use soapy water to see where it's coming out.....

Sorry, should of course have said rotate till the exhaust valve is shut, inlet valve is open..

[Edited on 18/3/10 by GeoffT]

quote:

---

Spraying brake cleaner in the each barrel results in the idle speed slowing down

---

David,

May I also suggest posting a message on se7ens.net.

There's a fair few caterham owners on there, and the technical expertise in that area is pretty high (several Caterham duratec owners + Caterham dealer)

Stephen

Oh yes - and a lot of them live in Cambridgeshire...

You tried pouring water over it I guess?
best
D

Edit: I see - you used brake cleaner...

[Edited on 18/3/10 by Dave Ashurst]

Is there a forum there? If so do you have a direct link as I cant find one. Its getting late and I am in a foul mood!

I should also say I have tried using alpha_n (TPS) based fuelling too breifly just to check and it has the same result. A nice steady 1300rpm idle....

I also pressurised the bundle of MAP lines with an airline set at around 50psi and couldnt find any hissing joints.

Just to understand what I am trying to find. The engine should flow around 700CFM at 1000rpm idle (assuming 20% VE), to get that up to 1300rpm the air flow would be in the order of 920CFM, so I am looking for a pretty major leak of 220CFM! And thats assuming the VE is constant of course.

Anyway plan of action for tomorrow:

Replace MAP line from collector to ECU or disconnect and temp plug to see if the leak is at the ECU. Didnt fancy spraying cleaner into the ecu to find out!

Cover the throttle body inlets with a piece of wood and slowly cover them and see if the idle speed can be reduced that way - if so this points to air getting past the rollers themselves.

Failing that cover everything with sealant and reassemble. Though I have my doubts....

quote:

---

Originally posted by Dave Ashurst
You tried pouring water over it I guess?
best
D

---

http://mailman.se7ens.net/mailman/listinfo/sevens

[Edited on 18/3/10 by stevebubs]

quote:

---

Originally posted by flak monkey

quote:

---

Originally posted by Dave Ashurst
You tried pouring water over it I guess?
best
D

---

Hi Dave,

I havent tried that no, although theres a river opposite the house. Would pushing it in there have any effect?

David...

---

I poured water over mine and it slowed the fast idle..

Not a permanent solution of course

High idle appears to be a known issue with roller barrels, so at this point I would like to say I should have fitted conventional throttle bodies at 60% of the price

Anyone got a set of Jenveys? Seriously!

If the Rollers shut off completely then the engine would stall wouldn't it?
So a small amount of air needs to get past to let it idle.

There isin't some sort of bypass air drillings is there that are a little large for your setup?.

The idle speed doesnt change regardless of where the roller idle stop is set until you get a gap of 6mm or more. Closing them too far results in them opening up in reverse. Between this point and the point at which speed starts to increase there is no difference in idle speed whatsoever.

Idle bleeds are all completely shut off.

David

Hmm the air is getting in there somehow...

I've heard of checking for leaks on 2 stroke crank cases by smearing them with Grease... maybe not the best thing to be injested into your engine but something along the same lines could be thought up to check and find exactly where the airs getting in.

My intention is to block off the inlets tomorrow and see what that tells me.

At the moment a set of DTH Jenveys is looking like a possibility

quote:

---

Originally posted by r1_pete

quote:

---

Originally posted by Bigheppy
Please humour me for a while, on your last post you said the carb roller/barel was round on the inlet and oval in the outlet of the throttle body. If the barrel were rotated 180 deg making the oval side the inlet to the throttle body due to the shape of the oval when the throttle was closed a smaller amount of air could be drawn in so reducing the idle speed. This is how some model aeroplane engines were configured. I appreciate this might not work in your situation but it might be worth investigating.

---

That would just mean when the throttle is closed the oval would be opposite where it is now, as the inlet and outlet is symetrial top to bottom it wouldn't make a difference.

Only on opening the throttle, you'd have an oval against circular and vice versa.

---

quote:

---

Originally posted by flak monkey
My intention is to block off the inlets tomorrow and see what that tells me.

---

quote:

---

Originally posted by flak monkey
The idle speed doesnt change regardless of where the roller idle stop is set until you get a gap of 6mm or more. Closing them too far results in them opening up in reverse. Between this point and the point at which speed starts to increase there is no difference in idle speed whatsoever.

Idle bleeds are all completely shut off.

David

---

Have you spoken to Minster?
Minster Power

Have you tried leaning out the mixture?

[Edited on 18/3/10 by stevebubs]

I have leaned the mixture out as far as 14.7:1 as best I can. Runs really rough and at around 1400-1500rpm.

The throttle bodies were brand new essentially and untampered.

It is not possible to turn the barrels through 180deg and run the engine, for a start its not going to tell me anything, I know that with minimal opening on the outside there is no opening on the inside (infact anything under 4mm opening on the outside leads to no opening inside) so they are as closed as they can be at this point.

I do have a syncro, but having no trumpets fitted makes using it impossible as the port in the throttle body is too big in diameter to get a seal.

And yes I have seen the Minister datasheet, the same principles apply and I have applied them where appropriate

David

have you not just though that is how they will be? as you said they are know to have a high idle but there are allways compromisers for advantages

Speaking to Titan they tell me to expect a higher than normal idle, but that my expectation of getting an idle of around 1000-1100rpm wasnt unreasonable.

I have mailed them again tonight with the findings and will see what they say tomorrow.

I will also be on the phone to Raceline in the morning enquiring after a set of DTH Jenveys.

Dave Walker at Emerald has had similar problems to what I am experiencing with roller throttles and the way it was solved was to change to conventional Jenvey throttle bodies.

This is annoying though in 2 respects:

1 - there is now an awful lot of work to do to convert all the back plates I had laser cut and machined to fit the plenum to the roller barrels to fit a set of jenvey throttle bodies instead. Sure I can find a way, but its going to be another day lost. It also means that the plenum is going to have to make a guest appearance outside of the bonnet of the car, another thing I wanted to avoid purely for aesthetic reasons!

2 - the cost. A set of jenvery replacements is going to run me around £675 by the time I have sorted a throttle linkage and TPS.


I really could do without the hassle, but there is no way I am going to put up with a 1300rpm idle thats rich and crap just to be say I am running roller throttles!

After the lengths you have gone to try and find the cause of the problem i am still convinced the issue is the amount of air that leaks past the roller barrels and the only way to fix is new barrels maybe? or completley new Throttle bodies.

either way i feel for you david poo situation to be in but please don't lose heart it will be worth it in the end

i'd like to hear the results of the tests i suggested that you're going to do next .........

one thing springs to mind though - are you sure the rollers you've got aren't knackered? Is there anyway to test?

Just a thought mate, but are you getting cross air bleeing through the 4 map air sensors that you have fitted. Have you tried fitting one way air valves for the time being (yes I know that you would need to get rid of these once you have the supercrarger fitted)??????

Is there not room to mount the injectors below the throttle bodies if you go Jenvey route? would this then bring down the height of the plenum?

Depends on the design of the plenum of course (thinking about it makes it less likely to work)

[Edited on 18/3/10 by stevebubs]

[Edited on 18/3/10 by stevebubs]

[Edited on 18/3/10 by stevebubs]

Just read your other threads.

If the roller clearances in the barrel are too large, could grease around the barrels help reduce the flow?

(Mechanical numpty on some of this stuff so please shoot me down in flames)

What does your synchrometer show as the airflow when pushed into the trumpet?

If i did go down the jenvey route I would leave the injectors in the head anyway and blank the ports in the throttle bodies and use them for MAP take off.

I dont really want to smear loads of grease around the rollers, they are meant to be run as they are (I have a copy of the Cosworth Duratec engine build manual and have followed it to the letter). All that would tell me is if there is air leaking past the barrels.

I did get some rough readings with the synchro when I first fired it up, and th readings were around 6-7 on the scale, which is high for idle, this is also without a proper seal on the synchro. The pinto would normally have idled showing 3.5-4 on the scale, so there seems to be more air being pulled in.

quote:

---

Originally posted by MikeR
i'd like to hear the results of the tests i suggested that you're going to do next .........

one thing springs to mind though - are you sure the rollers you've got aren't knackered? Is there anyway to test?

---

Very strange. Hope you get it sorted! It certainly sounds like the air is getting in there somewhere..... You're running NA at the moment I assume? The TBs might not appreciate being force fed I suppose if you're hooked up the blower. But I suspect you'll be wanting to get it working properly NA first!!

Is the timing right? It could have nothing to do with the roller bodies- something like a mix-up re timing could cause a high idle.

Try fitting the filter and inlet plenum. The further flow restriction may reduce the air into the rollers.
Personally, it sounds like the inlet ports are too big for the engine, so restricting the inlet by use of a filter or restrictor makes sense.

What do you think?

I know that putting a filter onto the carb on the Dutton made one hell of a difference and it suddenly stopped running rough.

The rollers are leaky. Everything points in that direction. Question: do you still have the MAP lines connected to all 4 barrels? If you do, then that could be a cause for your higer (well, a bit higher) idle. Reasoning for this is as follows: the 4 cylinders do not draw air in at the same time; roughly one of them is sucking at once (4 strokes, 4 cylinders...). By having the barrels connected, every cylinder is effectively (through the MAP hoses!) sucking on 4 (slightly leaky) barrels, and thus sucking on 4 times the "leakage area". Plug up the MAP takeoffs and see what happens with the motor running (for now) in alpha-N mode. If this helps and as an alternative to running speed-density, you could always use an airflow meter to determine load.

surley your map feed line should come from one point on the manifold???

quote:

---

Originally posted by boggle
surley your map feed line should come from one point on the manifold???

---

I am using 4mm vac hose for the MAP feeds. I have tried running under alpha_n and it made no difference.


As an update to this I have spoken to Raceline this morning and decided to order a set of DTH 45mm Jenvey throttle bodies. Conventional style. They should be with me tomorrow morning. Their opinions on roller barrels seem to match with quite a lot of others and they have seen a few. All in all very helpful people to talk to and they were very interested in my project.

David

quote:

---

Originally posted by MikeRJ

quote:

---

Originally posted by boggle
surley your map feed line should come from one point on the manifold???

---

If you only take the MAP feed from one cylinder when using individual throttle bodies then you get a very rough, pulsing signal that is of no use.

Sebastian makes a very good point with the MAP feeds though, what sort of diameter are the pipes you are using? I would definitely try his suggestion of blocking them up and running under Alpha-N if you haven't already.

---

quote:

---

Originally posted by flak monkey
I am using 4mm vac hose for the MAP feeds. I have tried running under alpha_n and it made no difference.

---

quote:

---

Originally posted by sebastiaan


Also with the 4mm MAP hoses disconnected and plugged per cylinder (by stuffing a 6mm bolt in each hose?)

BTW, I think it's a good move to go for conventional TB's. Expensive experiment though.

---

quote:

---

Originally posted by flak monkey
If i did go down the jenvey route I would leave the injectors in the head anyway and blank the ports in the throttle bodies and use them for MAP take off.

I dont really want to smear loads of grease around the rollers, they are meant to be run as they are (I have a copy of the Cosworth Duratec engine build manual and have followed it to the letter). All that would tell me is if there is air leaking past the barrels.

I did get some rough readings with the synchro when I first fired it up, and th readings were around 6-7 on the scale, which is high for idle, this is also without a proper seal on the synchro. The pinto would normally have idled showing 3.5-4 on the scale, so there seems to be more air being pulled in.

---

Just to make you feel better - if the barrels where leaking that much what would happen if you where making full boost and came off the throttle - would the leak under boost with a closed throttle just keep you going rather than slowing down...... Sort of the opposite of boost lag....boost persistance. Not much fun entering a corner

Maybe you are better off with throttle bodies.

quote:

---

Originally posted by flak monkey
If i did go down the jenvey route I would leave the injectors in the head anyway and blank the ports in the throttle bodies and use them for MAP take off.

I dont really want to smear loads of grease around the rollers, they are meant to be run as they are (I have a copy of the Cosworth Duratec engine build manual and have followed it to the letter). All that would tell me is if there is air leaking past the barrels.

I did get some rough readings with the synchro when I first fired it up, and th readings were around 6-7 on the scale, which is high for idle, this is also without a proper seal on the synchro. The pinto would normally have idled showing 3.5-4 on the scale, so there seems to be more air being pulled in.

---

wow....missed this thread.
cant believe it david, didn't hink ti would beat you. Did you try greasing them up??? have cosworth had anything to say???

quote:

---

Originally posted by stevebubs


Why not 2 sets of injectors? you can get better granularity at the low end then....

---

Flak, I dont have a clue what you are on about and cant answer any of your questions but hey mate whats new!

I admire you with all your ideas and your great work. I wish i was as good as you.







Now get back in that dam garage and sort it as im getting bored waiting for my test drive!

Flak, can you just clarify, (only just seen this thread!) you say idle doesn't change until all the rollers are open by 6mm.....................

if that's the case, air is getting in AFTER the throttles!

6mm of opening should see it revving a LOT!

Are there any ways in for air downstream of the throttles?

I simply don't understand, 1400rpm doesn't need a lot of air (my experience is only with normal butterflies, but under 1mm of opening will give more than that idle) but 6mm of opening is what you would be using when driving gently!!

quote:

---

Originally posted by NS Dev
Flak, can you just clarify, (only just seen this thread!) you say idle doesn't change until all the rollers are open by 6mm.....................

if that's the case, air is getting in AFTER the throttles!

6mm of opening should see it revving a LOT!

Are there any ways in for air downstream of the throttles?

I simply don't understand, 1400rpm doesn't need a lot of air (my experience is only with normal butterflies, but under 1mm of opening will give more than that idle) but 6mm of opening is what you would be using when driving gently!!

---

could be air leak-vacum..

Definately no vac leaks anywhere.

Anyway, fixed the problem now. Fitted the set of DTH jenveys that arrived this morning. Runs sweet as a nut now, much smoother and 950 rpm idle. Will post pics later, doing this off the phone

sounds good but would still be good to knwo what the problem was, expensive either way...lol.
At least you seem happy now

UP for sale then?

quote:

---

Originally posted by flak monkey
Definately no vac leaks anywhere.

Anyway, fixed the problem now. Fitted the set of DTH jenveys that arrived this morning. Runs sweet as a nut now, much smoother and 950 rpm idle. Will post pics later, doing this off the phone

---

Great to hear you've got it sorted out at last, but a very expensive experiment!

If you're coming to Diss tomorrow, I'll buy you a pint if it'll help!

Ed.

hi david, glad you sorted out the idle promblem, sham about the cost involed

stuart

Thanks guys, works much, much better now.

All I can say at the moment is that the high idle on the rollers is due to the clearance between the roller and barrel. I have spoken to a lot of knowledgeable people in the last week and they say that this is a common problem on rollers and can be bigger problems on some engines than others - even the same model engine. So whilst one duratec may run fine on them, some wont. It also depends on the spec of the engine and a whole host of other things.

I am happy with it on the raceline DTH's and they looks pretty smart.

David

Some piccies of the Jenveys


Jenveys 1

And made a set of MAP take offs to fit in the injector ports. Sealed with Hylomar and then clamped in with some fabricated brackets. They have been painted now and are drying overnight before final fitting tomorrow morning.


Jenvey MAP mod 1

glad you finally got it sorted
plain sailing from here then

Just to clarify the roller idle gap thing as I dont think I explained very well.

This is a pic from the front with the recommended 6mm idle gap.


Front

And this is from the back. As you can see there is no opening on this side. (Its a shadow from the flash at the top BTW) You need to open the roller about another 1mm before you start to get an opening on the back and it will start to open at the top of the port.


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