changing to ITB load

Tuning concepts, methods, tips etc.

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Yves
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changing to ITB load

Post by Yves »

I'm going to make a change to ITB load.

What can I expect regarding the VE table, idle etc ?
pkm123
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Re: changing to ITB load

Post by pkm123 »

Are you starting from AN or SD mode? What is your idle vacuum? What is your cam duration at 0.05?
Yves
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Re: changing to ITB load

Post by Yves »

I'm starting from SD. My idle is around 68kPa. The cam is 247/249 @ .050.

I just went for a drive with VEAL on to rough in the tables. It seems to do quite a good job but at higher loads she goes lean and holds back. I just went over it and smoothed the valley in the 3D view of the fuel table that I'm seeing. Hopefully that will help.

So far I've seen values as high as 93 and as low as 18.1 in load. I have my Y-axis set for SD, meaning that the mayority of resulation was geared in the +70 kPa range. Lowest was 30 kPa. How to deal with that ?

What is used in MLV to view load (Y-axis) ? Load ? Untill now I've used map.
pkm123
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Re: changing to ITB load

Post by pkm123 »

First you should become familiar with this explanation: http://77e21.info/mstuning_itbmode.htm To run in ITB mode you need the ITB switchpoints. To do this you make a log of your engine in SD mode. Then you use MegalogViewer to build a scatter plot of the file. You want to graph MAP vs RPM vs TPS. Then you find the 90 kPa points and write down the TPS and RPM values at these points. These you input into the ITB load TPS switch point curve. You then use VE Live to tune your engine, just like in SD mode.

My engine is described under Success Stories: 452 cu.in. FE in 1968 Mustang. I had difficulty making the engine run smoothly in SD mode. My cam is 248/254 @0.05, very similar to yours. It made 65-70 KPa at 850 rpm idle and 60 KPa at 1000 rpm. This made the engine seem to hunt at idle. I changed to Alpha-N hybrid and everything got much smoother. In AN mode, I can idle the engine down to 550 rpm if I want, but find it smoother at 800 -850 rpm. The bigger your throttle bodies are versus cylinder displacement, the less time your engine is in SD mode and more time it is in AN mode. My ITB's are 50 mm. My engine can't use SD mode above 9% TPS. Other people using ITB mode have had problems with AFR when the engine makes the transition from SD to AN. I elected to run AN hybrid and am very happy with the results.

You are welcome to download my tune and copy the Load table and general settings to your engine.
Last edited by pkm123 on Wed Jul 22, 2015 3:09 pm, edited 1 time in total.
Yves
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Re: changing to ITB load

Post by Yves »

I have set the tps switchpoints according to a log that I've made.

What did you set the ITB load at switchpoints to ? I currently have them all set to 50%.

My engine is 347 ci, short stroke, long rods with 50 mm TB's.
pkm123
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Re: changing to ITB load

Post by pkm123 »

It is recommended that you leave them at 50% for all points, but some people have more SD points at low rpm and more AN points at Higher rpm
pkm123
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Re: changing to ITB load

Post by pkm123 »

your throttle bodies are very large compared to displacement. You may have trouble tuning ITB mode. Please post your tune (msq).
Yves
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Re: changing to ITB load

Post by Yves »

Here you go.
pkm123
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Re: changing to ITB load

Post by pkm123 »

Everything looks great. I would change the accel enrichment to 100% TPSdot. See how it runs. ITB mode is the same as Alpha-N hybrid above the TPS switchpoint. If you have trouble with the idle and cruise, change to Alpha-N + multiply and try my fuel table. Good Luck
Yves
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Re: changing to ITB load

Post by Yves »

pkm123 wrote:Everything looks great. I would change the accel enrichment to 100% TPSdot. See how it runs. ITB mode is the same as Alpha-N hybrid above the TPS switchpoint. If you have trouble with the idle and cruise, change to Alpha-N + multiply and try my fuel table. Good Luck
I have ran on tpsdot alone, but it wouldn't work, way lean and too sluggisch reaction even when the threshold was set to 15.

Works great actually.

I'm still not sure on the way it runs in itbload. Need to do a lot more runs and datalogs. It feels as if on top she's better accelerating.
pkm123
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Re: changing to ITB load

Post by pkm123 »

Great!! I've been happy with my accel enrich, but I may try your settings.
Yves
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Re: changing to ITB load

Post by Yves »

pkm123 wrote:Great!! I've been happy with my accel enrich, but I may try your settings.
Not to mention that it did cure my farting exhaust (because of which i blew up my muffler a couple of weeks ago btw). The farting was clearly because of the lean condition during acceleration after a decel.

If you go thinking about it, map rises faster than tps rises in those first acceleration instances.

Signal needs to be clean of noise however since it can trigger to fast.
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