Rough running action time!

[GreenV8S]

Classic Chim said:

no stepper motor

Just out of curiosity, how is it doing idle speed control?

[Classic Chim]

GreenV8S said:

Just out of curiosity, how is it doing idle speed control?

Air temp sensor ( fitted to smooth bore elbow)
Map sensor ( Mass Air Pressure ) fitted to inlet manifold
Engine temp sensor

Decides ambient temp and air density and temperature of engine and then the Ecu adds fuel and adjusts timing advance/ retard to suit.
Heated lambdas as we use on a Tvr as mine are standard low band but they heat up fast so add to the ECUs calculations on air/ fuel requirements to retain the best air fuel ratio,,,,, I think
Even very cold after a few seconds the engine would idle but I raise the revs to about 1200 and warm it at this time of year.
I prefere to fire it, idle a few seconds then gently bring the revs up, saves rattling cams as the oil has started to move.
This is why I like no stepper, I’m better at controlling the effect on the cam on cold starts then even an Ecu can do do.
If my engine fired and instantly ran at high idle I’d have slight cam knock for those first few seconds.
As loads of RV8 cars run on carbs 700 revs idle is quite the norm and 750 as mines set to is spot on. Usually a bit higher in this cold weather about 800 for the first couple of minutes but then it’s just as if it was fully warm.
It’s richer when cold but not by very much and the timing helps ease the pistons over sort of thing so it runs smooth almost straight away.
This is where the real fuel saving is if you drive it lots, stop start, there’s no smell of overfuelling ever.
Stand behind it when warm and you will smell nothing, no smelling like a leaking tanker when in heavy traffic which roof off on a hot day used to choke me, these things are worth there weight.

As it was mapped Catted it produces virtually no emissions at all 0.02% on one reading
It’s environmentally friendly,,, it really is.
The cost of running the car has been reduced considerably.
And now the heart and brain are in sync and suggest years of happy motoring when you look at doing other things to the car you know it’s worth it.
Win win

ETA It can be mapped at 200 Rev sight points all the way up.

Edited by Classic Chim on Thursday 4th January 17:49

Edited by Classic Chim on Thursday 4th January 18:18

[GreenV8S]

Classic Chim said:

This is why I like no stepper

I don't think you said how it controls the idle speed. If there's no idle air control valve then I guess it might just be using scattered spark, but that would be a little disappointing.

[Classic Chim]

GreenV8S said:

I don't think you said how it controls the idle speed. If there's no idle air control valve then I guess it might just be using scattered spark, but that would be a little disappointing.

Why ?
You probably know more about this subject, I just enjoy the results

And yes I think it does but don’t quote me on that.

The Map sensor ascertaining inlet vacuum pressure plays a vital role I believe.

Edited by Classic Chim on Thursday 4th January 19:12

[GreenV8S]

Classic Chim said:

Why ?

Scattered spark doesn't provide a very positive idle speed control in my experience, and the more authority it is given the more the ignition has to be retarded for hot idle, which makes it run hotter when you need it least. I think there's a good reason why just about every OEM setup uses an idle speed control valve. It does mean adding hardware to the intake system, which may not be convenient when you're trying to produce a simple aftermarket package, but it gives a better solution.

Edited by GreenV8S on Friday 5th January 18:10

[Classic Chim]

Agreed If over employed.
Scatter spark is available but not used on my car.

Idle is controlled by extra air added to the Plenum via idle screw position which is set slightly open to replicate a stepper which I assume allows for more fuel to be used on start up mapping.
As you obviously know throttle when fully closed draws very little air into the Plenum which is why stepper Motors are used, simply adds air
I think Jason plays with the throttle position sensor readings as part of all this.
I can’t answer as I’m a layman.

I don’t have a cold or hot idle problem, the idle is one of the good points.

Hot idle.
The car has ran at Powers for over 35 minutes replicating a traffic jam and lap top engine temp stayed totally consistent at 88-89 degrees with fans doing there job.
I was deeply impressed.
As the dash temp gauge is the same sensor as before Mbe after 30 minutes it was reading 100 degrees but the Ecu still read 88
So the engine doesn’t get to hot and idle is not a problem.
Cold winter I have to add a bit of air via throttle to raise idle but it’s only for a few seconds before it idles without drama but that’s more about cold oil.
It’s a performance car I like the total control I have over when the engine revs or not on start up.
It’s one less component to worry about or fail or go out of spec.
You might say thats a lazy or easier approach, I’d say simple and genious

Edited by Classic Chim on Friday 5th January 19:13

[GreenV8S]

Classic Chim said:

Agreed If over employed.
Scatter spark is available but not used on my car.

Does that mean there's no idle speed control apart from the fixed air bypass adjustment? If so, I'm surprised that you don't get significant changes in idle speed with engine temperature.

[Classic Chim]

GreenV8S said:

Does that mean there's no idle speed control apart from the fixed air bypass adjustment? If so, I'm surprised that you don't get significant changes in idle speed with engine temperature.

You’d be better served talking to Powers for the answer to that and you might be surprised to hear that I don’t get any uneaven idle or I’d have mentioned it.
The car drives beautifully around town on 1000 revs let alone idle?!?

It’s only because it works so well and the target idle of 750 is maintained so well I’ve come to the conclusion it never needed a stepper motor.
I’m sure a stepper can sort of smooth out the throttle response so make it easier to drive on off throttle but if your subtle with your foot It’s very rewarding and for me exactly what I want.

I’ve spent the money not just to have a very fast car and that’s a fact but to have a working Tvr that’s also user friendly or I couldn’t own it.
It has to do the job or I’m off!
It’s an awesome car now that’s all I can say.

Edited by Classic Chim on Friday 5th January 21:28

Edited by Classic Chim on Friday 5th January 21:48

[Classic Chim]

Green V8 I’ve just looked at your profile picture,,,
What a waste of words as you like induction systems,,, big ones by the looks of it and that must also mean management systems, you know exactly how they do it and don’t need me to fumble about trying to explain it.
I’m suprised you think I should experience idle issue’s though.
EFA
my engine with long thin trumpets that promote good air speed if not a bit restricted for outright power and the 885 cam that Dom specs plus decent compression from new rings and heads rebuilt plays an important role surely.

With this added suck squeeze bang It’s no surprise I got good results and because the cam and induction are not racy most likely the reason why I have easy manners at such low revs with zero shunting.
I have a new diff, I’d be screaming if the thing was shunting

The engine has done 25,000 miles since rebuild and well over 10,000 since Mbe so cams probably knocked off a bit by now. Truth is it’s got better and better at the low speed stuff weirdly enough.

Here’s one of the emmisions test readings that I did with a mate, I’ve done it a number of times
with the same results.
The Cat obviously works well and the lambdas do a decent enough job for low band.

Pre cats removed
Catted Y piece fitted
And sleeved exhaust.

footnote]Edited by Classic Chim on Friday 5th January 22:44[/footnote]

This is from an archaic engine producing 300 hp Catted and way more torques
Progress.

I’ve got a ticket with it de Catted somewhere and that might tell you more about the actual fuel ratio, thats if it’s not been binned.

If the S uses the Y and similar exhaust manifolds but runs de catt I’d expect more power than mine Catted.

Edited by Classic Chim on Friday 5th January 23:07

Edited by Classic Chim on Friday 5th January 23:31

Edited by Classic Chim on Saturday 6th January 00:52

[Classic Chim]

Here you go

This is fully de Catted using Clives Y with standard baffled exhaust.





And these are consecutive years mot readouts and many 1000s of miles inbetween.

Engine wasn't fully upto temp on one I seem to remember.




Not sure how much this tells you but I can confirm what the readouts suggest as I’m now running it Catted again, it runs clean and smells of little or no fumes

[GreenV8S]

Classic Chim said:

I’m sure a stepper can sort of smooth out the throttle response so make it easier to drive on off throttle but if your subtle with your foot It’s very rewarding

It's not really about throttle response. The main issue is that the engine's drag varies quite a lot between stone cold and normal operating temperature, and if you don't compensate for that the idle speed will tend to increase as the temperature increases. In other words it's easy to end up with an engine that idles too slowly when it's cold, and too fast when it's hot.

[Classic Chim]

With a decent diff that works with proper tyres this is a sub 4 second to 60 mph car
I've done a 12,7 on Rainsport.

I’ll leave this here




Not as fast as many great Tvr but it was never meant to be.
But it’s very fast.

And it’s faster than this time suggests as I had wheel rub from big tyres on my rear arches so one day I’ll get below 12.4 if I can be bothered.
The fact it’s so good on the road is quite magnificent and I count my stars.

[Classic Chim]

GreenV8S said:

It's not really about throttle response. The main issue is that the engine's drag varies quite a lot between stone cold and normal operating temperature, and if you don't compensate for that the idle speed will tend to increase as the temperature increases. In other words it's easy to end up with an engine that idles too slowly when it's cold, and too fast when it's hot.

Yeah
I appreciate those words as I’m slowly learning. It’s a fascinating subject and if I only had more time rather than talk bollony on here I’d likely really get into it so I avoid computer science at all costs

So if mine runs a bit more air into the Plenum via an open screw constantly wouldn’t it be controlled back by retard as surely it would run a high idle otherwise.
Will this in itself effect how much advance it can use when hot or at higher revs.
I don’t think Jason goes over 40deg either way.

Oddly it runs 800 revs cold dropping to 750 before water temp is 10 degrees even and maintains that when hot. just seems to need a few moments to warm the bores then it’s very un dramatic.

If anything after extended periods in traffic so as hot as it’s meant to get, reading 105 on my dash temp gauge it will go down to about 700/720 something like that and possibly smell rich but only just.
It seems to run very lean based on fuel and emissions tests but Jason says that’s not true and it’s fine.
Right now as I’m driving a short distance to work and back it’s not economical but it’s still into the 20’s rather than below them.

It’s so much better on fuel overall which is odd as most things that produce more power than standard Knock fuel efficiency off.

The lad I know who’s Subaru thingy
Tuned up and very nice but doesn’t do my fuel return figures and it’s marginally slower I’d wager. I’ve beaten a very new one and actually had him off the line too. Very interesting race with my engine pulling away mid torque band in each gear and his hp raining me in before another gear change and I just stayed ahead. Really interesting how each engine used it’s power and where it was. I had more torque after gear changes, the Scooby sort of bogged and hesitated for a tenth or two but was flying at high revs.

Gotta love a good tight race in safety

Edited by Classic Chim on Saturday 6th January 01:50

[GreenV8S]

Classic Chim said:

So if mine runs a bit more air into the Plenum via an open screw constantly wouldn’t it be controlled back by retard as surely it would run a high idle otherwise.

That's what is usually referred to as the scattered spark method, but I thought you said you don't use that.

Classic Chim said:

Will this in itself effect how much advance it can use when hot or at higher revs.

No. Since you aren't using a physical distributor there are no absolute limits on the available ignition timing other than the capability of the ECU.

[Classic Chim]

Scatter spark as far as I’m aware is switched off and only uses the extra air feed element of it.
I thought it just uses the map and a bit of ignition which is not scatter spark as such but I’m no expert and never will be, i just enjoy the benefits of a set idle of 750 and the low running manners down to 800 revs on occasion that that allows me.
Beautiful day for a drive in my little 450 that’s probably faster than a standard 500 and more economical than a decent 400 and with no shunt.

Idle problems,,, you must be having a laugh
I’ve spent a considerable amount of money for this reward or it would have all been totally pointless and it’s a combination of factors, ECU being one of them.

Edited by Classic Chim on Sunday 7th January 11:12

[GreenV8S]

Classic Chim said:

Scatter spark as far as I’m aware is switched off

If you don't have any idle air control valve and given the idle characteristics you describe, I'm pretty sure you'll find the idle speed is ignition controlled. If your engine does not use variable idle speed then this could be defined in the base ignition map rather than using a separate scattered spark configuration table, but it's scattered spark in either case. It's cheap to do and reasonably effective - I use it on my V8S - but it doesn't have as much control authority as a conventional idle air valve and does make the engine run hotter at idle. In the new induction system I will be using an idle air control valve. It's more work, but gives a better solution.

Anyway, I'm glad you're pleased with the way it works.