Initial set-up Queries

Give input on tuning as well as any tips and tricks you may have. Also feel free to share base mapping files for various engine types.
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katana
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Initial set-up Queries

Post by katana »

Hi All, I've used carbs for so long I'm struggling with initial set-up with ITB's. This may seem obvious to some but its not clear cut to me.

With ITB's and TPS set-up, is the 'closed throttle' TPS setting done with the throttle absolutely closed ie. not touching the throttle stop / idle screw or at an open position as when at running idle ie. blades just cracked? Both bodies have been sync'd for airflow btw.

At the moment I can get an idle with the blades totally closed - not great and seems wrong. Cracking the blades will cause a much higher idle level. Is a cracked throttle ok (as a minimum 'closed' throttle) and is it acceptable to reduce the rpm by decreasing the fuel supplied? Obviously with carbs a cracked throttle governs the airflow and so fuel delivery, but with injection the two are independent hence my confusion!
David Ferguson
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Re: Initial set-up Queries

Post by David Ferguson »

I suggest setting the TPS 0% with the throttle fully closed. Then crack it open with the throttle stop (usually < 2-3%). Control idle speed with ignition timing.
stevieturbo
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Re: Initial set-up Queries

Post by stevieturbo »

I agree.

I want 0% to mean the blade is actually shut. Clearly your idle position may not then be at 0%, but that's no big deal, just set it any settings for idle, to 2, 3, 4 whatever.

And likewise I'd want to ensure fully open 90deg or whatever is 100%

People who set the 0% with the blades open, but using the 0% as their idle position annoy me, it's just stupid. Blade shut, 0% should mean blade shut, not partially open.

As for idle speeds, it's a balancing act ( assuming no air bypass ) between blade open position and ignition timing. If it's too high, then pull timing.

Have main table around say 10-15deg, but allow idle control to retard that as needed to say 0-10deg ( doesn't have to specifically be those numbers ) to pull the idle back down.

If low timing cannot pull the idle back, then it will simply need less air somehow, but it is a balancing act.
Rob Stevens
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Re: Initial set-up Queries

Post by Rob Stevens »

'People who set the 0% with the blades open, but using the 0% as their idle position annoy me, it's just stupid. Blade shut, 0% should mean blade shut, not partially open.'

Stevie (and David by the looks of it) and I have polar views on this.

:)

I have always set the idle position as 0%, my reasoning is as follows.
* it allows full resolution of the TPS (not a big deal)
* you can't revisit your end points without completely closing your blades again, making it difficult to find you actual idle position again.
* it allows in field change of TPS simply and can be recalibrated easy (ok this isn't a daily requirement!!)(but as a competitor these things go wrong at just the wrong time and anything to help is welcome)
* every dyno I've ever been to sets as I do, however they also do a load of stupid other stuff (but I've only ever been to 4 different dynos)
* when quizzed on this the idea of setting the closed position as Stevie suggests the original designer of the system said something like 'why the fu** would you want to do that, but they can set it however they want' not known for customer cuddling.

Good thing is that DTA gives you the tools to set as you like.

I target 5 deg ignition on hot idle and use the idle via timing to maintain idle and works fine but when <0degC I need to open the throttle a little.

If your TBS are leaking that much it's not a good start, the final closed position needs to be on the screw stop, not the blades jamming in the bores.
Do you have any air leaks or bypass that can be closed?
stevieturbo
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Re: Initial set-up Queries

Post by stevieturbo »

there are no benefits to setting false baselines where closed does not mean closed.

And then if the throttle stop screw moves and the blade closes further....will it still read zero ? what's below zero ?

And your idle position will be whatever it was when you set your idle....be that 2, 3, 4, 5 whatever. Thus making it far far easier to ensure it is correct or reset later. When you set 0 as a false position that is not zero, it's just a mess.

Allan was very smart, but he had some strange ideas too.
katana
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Re: Initial set-up Queries

Post by katana »

Rob Stevens wrote: Tue Oct 04, 2022 3:19 am If your TBS are leaking that much it's not a good start, the final closed position needs to be on the screw stop, not the blades jamming in the bores.
Do you have any air leaks or bypass that can be closed?
I'm sort of glad to see that there is a difference in opinions - I guess all are right, and none are wrong - whatever works - works!

I'm leaning towards closed being closed and equalling zero with running condition being cracked a bit on the idle screw.
I did have a very high idle at one stage even though the blades were closed. It seems when I originally did the set up I was planning to use and IAV for idle control but as it didn't seem to be working, it was disconnected and the air bleeds plugged. But even these leaked enough air to idle up when blades closed / throttle actually disconnected! I've since removed the air connection nipples and replaced them with blanking nipples but engine will still idle 1000 - 1100 @ closed blades. I guess i'll have to try the ether / WD40 squirt to see if the manifold joints are leaking !

I'll give it another go maybe tomorrow, with a cracked throttle and maybe try reining back the fuel and the timing as, although i've got nothing to compare them against injector pulses of between 4 - 5msec at idle seem maybe a bit rich - lambda (if it can be believed) is saying AFR is >8 ! and timing jumps from 15 to between 25 & 30 @ 4% throttle. I'm used to 30 odd degrees for midrange.

Obviously I can't get the engine under any significant load (its not road legal presently) and trying to understand what the engine wants whilst balancing a laptop in my lap / fiddle with buttons / twiddle pot box knobs / and tweak throttle whilst trying to look at multiple diagnostic screens is certainly trying my patience! Maybe if I clear the Ignition table and just populate the whole table with 10's ? Its one less thing to worry about?
stevieturbo
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Re: Initial set-up Queries

Post by stevieturbo »

it is simple. closed means closed.

idle air/position may or may not be closed depending on what air bypasses you have if any....but 0%, closed should always mean closed. Not open. Like you wouldn't set the max blade position to 80% would you ? just because you won't push the pedal further ?

If the throttle blades are closed, and there is no air bypass at all...quite simply the engine should not run lol.

For simplicity, get a decent idle in the 13-13.5 AFR range to start. The engine will be fairly happy at that, then sort your timing as already stated whether using no advance adjustments for idle speed, or if you are.
Once you've got a decent stable idle via timing and blades all adjusted/balanced, then you can lean it back into the 14's and see how happy it is and if you can get it to run nicely at stioch.
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