LS3 Sidedraft ITB System
Drifting
Joined: Nov 2017
Posts: 1,384
Likes: 297
To do alpha-N with drive-by-wire throttle you'd want to get the "alpha" value from the throttle butterfly angle, rather than from the pedal. There are times when the throttle position doesn't match the pedal position, like idle for example - the PCM adjusts the throttle angle on it's own while your foot is off the pedal. Same for cruise control.
I suspect traction control might also reduce the throttle angle, if it can't get enough torque reduction by pulling timing, but I'm not sure of that.
SD seems preferable to me though. Alpha-N basically works on an assumption that intake-tract air pressure is determined by throttle angle, whereas with SD you're actually measuring that pressure. It's a bit tricky to measure for ITBs, because of the issue with averaging, but that seems like a solvable problem.
And I wouldn't be surprised if ITBs idle better with a little manifold for the MAP sensor than without it. Seems like it might be hard to get all 8 throttle openings to match precisely when the openings are tiny. But the added manifold could compensate for that.
I suspect traction control might also reduce the throttle angle, if it can't get enough torque reduction by pulling timing, but I'm not sure of that.
SD seems preferable to me though. Alpha-N basically works on an assumption that intake-tract air pressure is determined by throttle angle, whereas with SD you're actually measuring that pressure. It's a bit tricky to measure for ITBs, because of the issue with averaging, but that seems like a solvable problem.
And I wouldn't be surprised if ITBs idle better with a little manifold for the MAP sensor than without it. Seems like it might be hard to get all 8 throttle openings to match precisely when the openings are tiny. But the added manifold could compensate for that.
Thread Starter
Drifting
Joined: Apr 2015
Posts: 1,893
Likes: 295
From: Buffalo NY
I'm totally open to any tuning strategy that will give me a nice driveable result - doesn't have to be alpha-n. If I can do it totally using Speed Density and IAT, then I'd like to proceed with that route and not reinvent the wheel.
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
Again I can only speak to EFILive but, it has the Alpha N (TPSxRPM VE Table) and another setting to allow transition between AlphaN fueling strategy and standard VE speed density based. Basically let's you do a normal SD tune, but allows you to define VE for certain regions based on TPS alone where MAP isn't reliable.
Beyond that I have no idea is this hybrid or pure SD is better, no personal experience myself. Good luck!
Beyond that I have no idea is this hybrid or pure SD is better, no personal experience myself. Good luck!
Le Mans Master
Joined: Nov 2003
Posts: 8,308
Likes: 157
From: NJ
I'll read thru and chime in when a get a second and give you some feedback from what we were able to do. It's been a long time and there are a ton of details to getting this to run right and I have to refer back to some notes to be completely accurate. There were a few threads years back where I commented in that have a lot of detail that will also help.
But for now, we tuned alpha n for street and strip. I did real time tuning on the street that helped a great deal. When you get it right you can idle at 500 rpms with a giant can, drive around with no surging, and pull away from a start with no throttle.
But for now, we tuned alpha n for street and strip. I did real time tuning on the street that helped a great deal. When you get it right you can idle at 500 rpms with a giant can, drive around with no surging, and pull away from a start with no throttle.
Le Mans Master
Joined: Nov 2003
Posts: 8,308
Likes: 157
From: NJ
We did this with drive by wire and eventually cable.
In the beginning we were getting REP code until I figure it out and had to adjust the linkage so to allow for things to sync up.
I'm not a tuner like some pros on here that may have other solutions but I can tell you what worked for me on the street and strip. Most people thought my car was a mild heads and cam car by its street manners. I'll post up a video.
In the beginning we were getting REP code until I figure it out and had to adjust the linkage so to allow for things to sync up.
I'm not a tuner like some pros on here that may have other solutions but I can tell you what worked for me on the street and strip. Most people thought my car was a mild heads and cam car by its street manners. I'll post up a video.
Thread Starter
Drifting
Joined: Apr 2015
Posts: 1,893
Likes: 295
From: Buffalo NY
I'll read thru and chime in when a get a second and give you some feedback from what we were able to do. It's been a long time and there are a ton of details to getting this to run right and I have to refer back to some notes to be completely accurate. There were a few threads years back where I commented in that have a lot of detail that will also help.
But for now, we tuned alpha n for street and strip. I did real time tuning on the street that helped a great deal. When you get it right you can idle at 500 rpms with a giant can, drive around with no surging, and pull away from a start with no throttle.
But for now, we tuned alpha n for street and strip. I did real time tuning on the street that helped a great deal. When you get it right you can idle at 500 rpms with a giant can, drive around with no surging, and pull away from a start with no throttle.
This is good timing, actually...I received the kit from Speedmaster today and it will need some massaging to work (100% expected that, at this price point...)
I am using a spare L92 longblock as a mock up and will post up once I've compiled some more info on what the kit actually needs to work.
Last edited by nsogiba; Nov 25, 2019 at 06:18 PM.
Le Mans Master
Joined: Nov 2003
Posts: 8,308
Likes: 157
From: NJ
100kpa MAP signal at 30% throttle sounds like a side effect of bad plumbing for the MAP sensor. Unless of course they were also seeing full power at 30% throttle.
I wonder if it would be helpful to use a long log, and locate the MAP sensor a long ways from the lines that go to the ITBs, so the sensor sees a good average of the ITB pressures.
I wonder if it would be helpful to use a long log, and locate the MAP sensor a long ways from the lines that go to the ITBs, so the sensor sees a good average of the ITB pressures.
Driving around for days tuning in real time was the key even with archaic BS3.
Le Mans Master
Joined: Nov 2003
Posts: 8,308
Likes: 157
From: NJ
We tuned alpha n and real time tuning make a big difference. I'm sure, a professional tuner like Julio can make it work well with whatever method of tuning he chooses but it will take some time driving around with it. Probably like any tuning you really need to keep tweaking it to get the results you want.
Sorry if I'm being redundant.
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Thread Starter
Drifting
Joined: Apr 2015
Posts: 1,893
Likes: 295
From: Buffalo NY
The advantage is that you can run a big cam and make a lot of power since the ITB's make the car completely streetable.
We tuned alpha n and real time tuning make a big difference. I'm sure, a professional tuner like Julio can make it work well with whatever method of tuning he chooses but it will take some time driving around with it. Probably like any tuning you really need to keep tweaking it to get the results you want.
Sorry if I'm being redundant.
We tuned alpha n and real time tuning make a big difference. I'm sure, a professional tuner like Julio can make it work well with whatever method of tuning he chooses but it will take some time driving around with it. Probably like any tuning you really need to keep tweaking it to get the results you want.
Sorry if I'm being redundant.
Can you elaborate on random location? You mean tapped into a random runner beneath a throttle plate?
Last edited by nsogiba; Nov 25, 2019 at 06:34 PM.
Le Mans Master
Joined: Nov 2003
Posts: 8,308
Likes: 157
From: NJ
Alpha n was the only think that worked for us at the time and it took a while to capture all cells but when we did the car ran like a dream. My buddy was a tuning hobbyist and I'm not a tuner but we managed to get it running great this way. I'll look for that meter and send it to you if you want with any other stuff I may have.
Write down your goals so we know how far to take this because there's a lot of stuff you need to know and maybe certain things wont matter to you.
I'll search for an old thread where I have a lot of info to jog my memory but I can tell you that things to consider are:
a lot of time tuning both mechanically and software based
adequate filtration without killing hp (airboxes, filter socks, screens)
controlling hot air from the engine bay feeding trumpets
fitment in engine bay to avoid blocking trumpet radii
trumpet lengths for optimal harmonic for desired rpm use
etc...
Write down your goals so we know how far to take this because there's a lot of stuff you need to know and maybe certain things wont matter to you.
I'll search for an old thread where I have a lot of info to jog my memory but I can tell you that things to consider are:
a lot of time tuning both mechanically and software based
adequate filtration without killing hp (airboxes, filter socks, screens)
controlling hot air from the engine bay feeding trumpets
fitment in engine bay to avoid blocking trumpet radii
trumpet lengths for optimal harmonic for desired rpm use
etc...
Le Mans Master
Joined: Nov 2003
Posts: 8,308
Likes: 157
From: NJ
I am following you. My challenge will be determining how to tune the setup (mechnically and digitally) using the tools I have - HPTuners, a wideband and MAP sensor. I was planning on using a synchrometer to make sure all 8 were flowing the same/close. It sounds like the best tuning strategy is a blend of partial throttle VE, and when it crosses the atmospheric threshold (30%TPS/100kpa) use TPS multiplier to turn it into alpha N.
That sounds like a smart formula.
Can you elaborate on random location? You mean tapped into a random runner beneath a throttle plate?
That sounds like a smart formula.
Can you elaborate on random location? You mean tapped into a random runner beneath a throttle plate?
Thread Starter
Drifting
Joined: Apr 2015
Posts: 1,893
Likes: 295
From: Buffalo NY
Drifting
Joined: Nov 2017
Posts: 1,384
Likes: 297
100kpa at 30% throttle sounds about right. That's why we chose alpha n. At the time the tuning software (efi live, I think) wasn't as detailed or complicated as it is now but it worked and eventually I went to big stuff3 so I could get around the rpm high limit of the stock PCM.
Driving around for days tuning in real time was the key even with archaic BS3.
Driving around for days tuning in real time was the key even with archaic BS3.
Thread Starter
Drifting
Joined: Apr 2015
Posts: 1,893
Likes: 295
From: Buffalo NY
Nothing too recent. I spent some time cleaning up the runner castings as they have a feature at the top that prevents them from laying totally flush against the head. Also had a friend make up some solid aluminum shaft couplers as the tab/arm system that comes with it causes uneven opening. Unfortunately they are very unforgiving of any axial misalignment (which is caused by the subpar machining), so I am working on that next. Honestly it's enjoyable to go through and make the setup more robust mechanically as I'm sure it will ease the setup down the road when it's on the car.
Thread Starter
Drifting
Joined: Apr 2015
Posts: 1,893
Likes: 295
From: Buffalo NY
They're unofficially for sale and you have first dibs!
I got as far as having a friend machine some solid bushings that would connect the shafts of each throttle body, as the original linkages caused the butterflies to open at different rates. Obviously they'll come with the set.
I got as far as having a friend machine some solid bushings that would connect the shafts of each throttle body, as the original linkages caused the butterflies to open at different rates. Obviously they'll come with the set.