A thread on the Facts about running ITBs on a non ITB ECU

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A thread on the Facts about running ITBs on a non ITB ECU

Postby yoshimitsuspeed » Mon May 06, 2013 11:07 am

The other thread turned into a $#!!&!$!fest so I am starting this thread in hopes that we can put down simple facts.
I am looking for people who have run ITBs on the 16v ECUs with widebands and any other sensors to monitor effects and or people who have dyno tuned ITBs on any of these ECUs.
I am not looking for opinions or theories unless you have specifically studied induction theory, engine management and engine tuning to the point of knowing enough that you are extremely confidant your theories are accurate and scientifically/mathematically supportable.


I started this thread because many people say the 16v ECUs will not run ITBs yet not one person has shown this to be true. No one has posted dynos or showed AFR logs or even just explained the effects the mod had on AFRs.
As importantly there are too many variables and unless someone plays with all of them you can't make a blanket statement like ITBs don't work with x ECU.

First lets get the performance part out of the way. ITBs are not a performance mod until your motor is very heavily built. It is not enough of a performance mod to justify the time and cost until you are getting close to Formula Atlantic territory. This thread is not about gaining performance through running ITBs because by the time you can you will have already been on aftermarket engine management for some time.
This thread is about running ITBs on a motor and having it function as well or better than it did with the single TB.
Now for a second of opinion. I think this is a silly mod. I do not suggest support or condone putting ITBs on your 16V. I think it's a waste of time and money. However I just want to try to straighten out facts. Saying you can't run ITBs on a stock ECU is a lot different than saying you shouldn't run ITBs on a stock ECU. Even then it's more just that it's silly from a performance standpoint.

Let's look at the basic science first. There is nothing that makes ITBs drastically different from a single TB setup. The throttle plates in the runners allow for quicker throttle response although we are talking in the range of milleseconds. So quicker response is a good thing. The plates in the runner cause a disruption for the intake pulses that allow for resonant induction. It's interference becomes much greater as the throttle plate closes so anything off WOT ITBs are actually much worse for resonant induction. A single TB will be better for street cars and overall efficiency across the spectrum of throttle travel. This will effect VE but it shouldn't be extremely drastic. An AFM ECU should have no problem compensating. A MAP ECU might have a little more trouble.
Now aside from that you really just have runners of x diameter and x length. Diameter is important at high level tuning but we have seen plenty of variations in runner diameter or people running SPs on LP ECUs, vice versa and such to know that it's not a make it or break it factor for this discussion.
Next is length. Length will effect the VE curve of the engine. It may not be possible to run all ITB variations on all 16V ECUs. Just because you try super shorty stacks on ITBs with bad results does not instantly mean ITBs will not work altogether.
When trying to build a custom system around a set engine management your ideal setup would likely be as close as possible to the original setup from there some tweaking may actually make it better.
So from a VE point of view ideal would probably be to try to match the runner length as close as possible to stock.
I still think there would be a lot of wiggle room on length especially on an AFM ECU.

Now for my personal experience.
I started out with a 4AGZE AW11. At one point the supercharger seized so I converted it to NA while I put together my turbo build. I went from the GZE intake to the NA intake. It was slow without boost but it drove just fine. Going from 2 in runners to 12 in runners seemed to have no effect on how it ran or drove.
I installed the DSM T25 turbo and started driving it at stock boost. Now that I had a turbo I wanted to up the boost but I wanted to do it safely so I bought a wideband. The new setup with the NA intake mani behaved just as others described the GZE behaving as far as AFRs. From there I had a baseline. At just 10 PSI I started to get low end leanout. People said the 440cc injectors could just be dropped in although I couldn't find one person who could back that claim with a wideband or a dyno.
I decided to give them a shot. I learned that the GZE ECU could not handle the 440s and that it ran too rich no matter what. If you reset the ECU it would run way too rich across the board while it started to relearn. After that it leaned out the closed loop back to where it was supposed to be but the open loop stayed int he 10s. The 20% increase did allow me to up the boost to 12 PSI before the low end leanout got scary but that was not enough to lean it out above that.
We theorized the larger 3SGTE AFM would lean it out since the larger flapper should open less per unit of air so I decided to try that. For whatever reason the 3SGTE AFM actually makes it run richer. I was able to tweak the AFM to get closed loop AFRs back down but it did not help WOT AFRs.
After running that setup for maybe 5k miles I got rod knock. I decided I wanted a BT instead of rebuilding the 16V.
I did a lot of research and found the dizzy worked the same, the TPS output was the same, all key components between the GZE ECU and the BT should be able to work together so I decided to try to run the BT on the GZE ECU. I found 380 injectors which after my experience with the 440s I knew should work fine. I also decided I was going to run my DSM T25 on the stock BT.
At that point most people told me it wouldn't work. No way you can run 11:1 compression on a GZE ECU. No way you could boost stock BT pistons. No way you can run ITBs on a GZE ECU.
At that point I realized these were valid concerns but decided to push forward. I actually initially planned on removing the ITBs and running a plenum with a single TB but I decided I didn't want to bother with all the extra work. Plus I'll admit the ITBs are kinda cool. I decided I'd just have to try to get it to work as it was.
Initially I left the wastegate disconnected making it essentially an NA. In the very beginning it had a bad tip in stumble. If you gave it gas quickly it would often stall. My theory is that the GZE has such a large volume of air between the TB and the intake that it probably had some delay in the ECU. The ITBs might respond so quickly the ECU doesn't have time to adapt.
I adjusted the TPS on the very tightest side of it's adjustment range so it would register coming of idle as early as possible.
I played with the AFM adjustments for a while balancing AFRs and trying to reduce the tip in stumble.
Finally I got it to where the tip in stumble was only there when it was cold and even then I could drive around it easy enough. Once it warmed up the stumble was gone and it was fully responsive.
The AFRs behaved just as they had previously. Possibly a little richer than the originally 365s but much better than the 440s. At idle and cruise it found stoich immediately. At WOT it would go from about 13.5:1 around 3k RPM to about 12:1 at redline. AFRs behaved exactly as well as I could ever hope for a stock ECU.
At this point I also had a knock light and a pyrometer.
I took the timing from 6 deg to 8 deg with no noticeable change. I took it back to 6 and hooked up the turbo and slowly took the boost up to about 6-7 PSI.
From there I took the timing back to about 8 deg and it seemed happy. After that I took the timing to 10 deg and I got some knock at low RPM pulling away from a stop so I took it back to 8 deg.
I have driven the car with the VVT turned on and with it turned off and there is no noticeable change in the AFRs, EGTs or knock.

I do not believe that ITBs change anything enough for an AFM ECU to have any trouble whatsoever with them.
I am also quite confidant that with the right tweaking a MAP ECU could be made to run them just as well as the original setup. That however is only theory.

I do not have personal experience with the NA ECU on ITBs but I have seen people run 8 PSI boost on a stock AFM ECU with minor tweaks. If it can do that then I can see no possible way ITBs could effect VE enough to cause any sort of running/driveability problems.

So that is my story and my reasoning.
If anyone has any datalogs, dynos, or personal experience with making ITBs work or with issues that they had with trying to get them to work then post them up.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby chohdog » Mon May 06, 2013 11:31 am

Take the intake manifold off and try to run the ITB's completely open with the stock computer.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby yoshimitsuspeed » Mon May 06, 2013 11:51 am

chohdog wrote:Take the intake manifold off and try to run the ITB's completely open with the stock computer.


What is your point? Why would I try to do that? Wouldn't work very well with my AFM based ECU.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby oldeskewltoy » Mon May 06, 2013 2:26 pm

The BIGGEST problem with running ITBs (silvertop, or blacktop)... are setting them up correctly...

They need to be synchronized mechanically, AND each individual T/B needs to be adjusted (synchronized) for equal air flow.

This procedure tends to not get done correctly...


*IF* the above procedure is done correctly, then the ITB option will run and operate as long as all the sensors are satisfied (afm - on US cars means the ITBs can't be open if they are to run on a US ecu).
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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby dr.occa » Tue May 07, 2013 5:33 am

^ this is true.

The old carb method of synching each of the throttle bodies mechanically is use a uni-sync on each throttle body. Adjust the idle speed screw on each throttle to match that of any one of them - but choose one obviously.

A manometer is another tool that uses vacuum tubes filled with either mercury or some other liquid. You just hook up each of the vacuum tubes to individual vacuum ports on each throttle body (if they have them) and take note of the liquid levels as the car idles. Then, again, adjust the idle speed screws on each throttle body so all the liquid levels are level with one another.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby yoshimitsuspeed » Tue May 07, 2013 8:53 am

The stock 20V ITBs tie all the ports together post throttle plate with the vacuum manifold. I think this gives a little more wiggle room on the balance of the ITBs.
Similar to the way you don't mess with the BISS on a single TB unless someone before you has messed with it I decided to throw mine in as they were. It would be interesting to check the balance but I haven't found the need since it runs so well as it is.
If you removed the vacuum manifold then the balance would be all that much more vital.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby yoshimitsuspeed » Tue May 07, 2013 9:13 am

In the other thread it was brought to my attention that for all AE86 owners running ITBs is so synonymous with running open stacks that to fathom the concept of running an air box and AFM seemed about as conceivable as mounting an elephant to your hood with rubber bands before an autocross.
This makes me feel as though I should stress the fact that running ITBs is not synonymous with running open stacks and with an AFM ECU you could no more run open stacks than you could mount an air filter to your single TB and expect to drive off.
If you have an AFM ECU then you need to route the intake air to the AFM no matter what. This also applies to the silvertop which comes stock with ITBs.
If however the question is simply if you can run ITBs on the AFM ECU then as long as you run the AFM I see no reason why that should be an issue.

I would still like to hear more from people who have actually ran the MAP 16V ECU with ITBs to hear their personal experiences. I have heard one person say it didn't work but gave absolutely no information as to exactly what didn't work. Other than that I have heard nothing but uneducated theory and Internet gossip.

It may seem odd that I am so opposed to running ITBs on the average 16v yet so adamantly curious about why this will or will not work.
For me it's understanding the physics of it. Understanding the true facts of intake design and understanding the effects of different designs.
If one ECU cannot handle ITBs and someone documents exactly how and why, it first gives us the opportunity to understand how the components changed the system, how flexible the system is and also gives us the opportunity to see how much we can change things to try to make it right. These things all expand our understanding. If however that ECU runs ITBs just fine but Internet rumors lead people to think that it cannot then it is distorting the understanding of physics and intake design theory for all of us. We can delude ourselves into believing that is the truth and we can base further assumptions on those false truths leading our whole perception of reality to be heavily influenced by rumors instead of facts.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby ga_goosh » Tue May 07, 2013 9:15 am

so yoshi. i have seen honda ecu running the 4ag engine with a custom honda dizzy mount. i am wondering if it is possible to run a 16v 4ag with a simmilar dizzy adapter and ecu from a black top?
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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby yoshimitsuspeed » Tue May 07, 2013 9:35 am

ga_goosh wrote:so yoshi. i have seen honda ecu running the 4ag engine with a custom honda dizzy mount. i am wondering if it is possible to run a 16v 4ag with a simmilar dizzy adapter and ecu from a black top?

The BT and the GZE dizzy function identical to each other. I am running the BT dizzy on my GZE ECU. If you found a GZE dizzy you could do the exact opposite. So it would in fact be much easier. Other than that you would just swap a few sensors over and I think it would run.
Now the BT is a MAP ECU so the VE of the engine is very important. The advantage of the honda ECU as I understand it is that you can reprogram them. Since that is not possible with the BT ECU your only option would be to try to get the VE map of your 16V as close to that of the BT as possible. That may just be a matter of adding the ITBs and throwing in some cams with similar specs to the BT. On the other hand that may not be enough to overcome the characteristics of the 16V. There is only one way to find out. It would be a very informative experiment however it's not the most practical route. I stayed with the GZE ECU because I already had it and it was already wired into my car. For the cost of the BT ECU you could buy a MS3 and for the time wiring it in you could redo the wiring much cleaner to accept the MS3.

I believe it's Scarecrowx on the MR2OC who has some threads in the MK2 section about modifying a 3SGTE to run a honda ECU. If it will work with a 3SGTE it should work on a 4AGE. Again though for the time and cost I am sure you could have some of the cheaper options of full blown engine management.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby ga_goosh » Tue May 07, 2013 2:11 pm

oh so thats why the honda ecu is a popular choice didnt know that. iv seen it done before but i cant seem to get any info on it. yea i am mainly considering ms2 or 3 but im not sure if i need all the features of the ms3. to tell you the truth your itb on afm ecu is really stirring up some questions in my head and now im second guessing a bit
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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby oldeskewltoy » Tue May 07, 2013 9:23 pm

yoshimitsuspeed wrote:The stock 20V ITBs tie all the ports together post throttle plate with the vacuum manifold. I think this gives a little more wiggle room on the balance of the ITBs.




I'm guessing you haven't seen ALL the 20V ITB manifolds....


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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby yoshimitsuspeed » Tue May 07, 2013 11:18 pm

I have not but I was under the impression they all had the same feature. Were there three different designs? I thought there were only two.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby ga_goosh » Wed May 08, 2013 6:27 am

yoshimitsuspeed wrote:
ga_goosh wrote:so yoshi. i have seen honda ecu running the 4ag engine with a custom honda dizzy mount. i am wondering if it is possible to run a 16v 4ag with a simmilar dizzy adapter and ecu from a black top?

The BT and the GZE dizzy function identical to each other. I am running the BT dizzy on my GZE ECU. If you found a GZE dizzy you could do the exact opposite. So it would in fact be much easier. Other than that you would just swap a few sensors over and I think it would run.
Now the BT is a MAP ECU so the VE of the engine is very important. The advantage of the honda ECU as I understand it is that you can reprogram them. Since that is not possible with the BT ECU your only option would be to try to get the VE map of your 16V as close to that of the BT as possible. That may just be a matter of adding the ITBs and throwing in some cams with similar specs to the BT. On the other hand that may not be enough to overcome the characteristics of the 16V. There is only one way to find out. It would be a very informative experiment however it's not the most practical route. I stayed with the GZE ECU because I already had it and it was already wired into my car. For the cost of the BT ECU you could buy a MS3 and for the time wiring it in you could redo the wiring much cleaner to accept the MS3.

I believe it's Scarecrowx on the MR2OC who has some threads in the MK2 section about modifying a 3SGTE to run a honda ECU. If it will work with a 3SGTE it should work on a 4AGE. Again though for the time and cost I am sure you could have some of the cheaper options of full blown engine management.


so would a st 20v ecu be a better choice over the bt since it is a afm ecu?
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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby yoshimitsuspeed » Wed May 08, 2013 10:44 am

ga_goosh wrote:
so would a st 20v ecu be a better choice over the bt since it is a afm ecu?


Quite possibly, as long as you are willing to run the airbox and AFM but that takes us back to the original topic. If you are willing to run a box and AFM then what's wrong with an NA AFM ECU?
Unless your car currently has a different ECU like 16V MAP or something. I would still like to see someones personal experiences with ITBs on the MAP ECU. I am still not fully convinced it could not be made to work pretty well but until we find someone with personal experience with it that path would be uncharted territory with some risk.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby ga_goosh » Wed May 08, 2013 3:49 pm

see i dont mind trying a silver top setting since it is more tuned with the larger cams and higher comp. i dont see why it wouldnt work either then again price wise a ms3 would probably look more affordable with the ability to run open stacks not that that is a selling point but aesthetically speaking? sure its a big deal
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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby ga_goosh » Thu May 09, 2013 6:59 pm

what ignition options is there with the stock ecu? i want distributorless i have an edis 4 complete system i wouldnt mind putting to work.
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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby yoshimitsuspeed » Thu May 09, 2013 8:10 pm

I seem to remember a good thread on the old board about running DLI on a dizzy ECU or something to that effect. I don't know a lot on the subject myself. Honestly unless you have a way to tweak the timing I see this as more of a disadvantage if you are messing with other variables like boost, cams, or other VE mods. Stock DLI cars are timed for that exact setup. If you change one variable timing may no longer be acceptable. If you change VEs with a dizzy at least you can advance or retard the base timing to suit your needs to a functional level. This is still far from ideal because you can't change the map but if say you get knock at x RPM at least you can back it off till you don't have knock. Granted that means you are leaving performance on the table in other areas of the map but at least it gives you a workable solution. When trying to tune with a stock ECU the things you can change are limited enough so the last thing you want to do is reduce the variables you can change.
I really like playing with stock ECUs because it gives you such a deeper understanding of the OEM system, it's limitations and it's adaptability. I Also like contemplating what's possible. One example is a thread I started on the MR2OC a while back about using the 3SGTE ECU for boosting the 4AGE beyond the easy capabilities of the NA or GZE ECUs. It is interesting to think about and even test if you have easy enough access to the parts to implement it. In the perfectly right situation it may even be the best power/performance to cost option out there. Other times it may just be fun to try because you can and you have nothing better to do. Or it may just be an expensive time consuming educational experience. All that said the last thing you want to do it overlook upgrading to something much better when that really is the best option. In my experience this generally comes down to a fear of stepping up to the next big thing.
There are the times when you have an NA ECU in your car and just want to run 5 PSI boost or some mild cams and it's just not worth stepping up to aftermarket engine management. There are other times when "AEM" would probably be the most ideal solution and people will choose the safer route and bang their heads against it much longer than they should. Just make sure that you don't expend unnecessary energy taking the less efficient route when your ultimate goals line up much better with a more direct route.
That said there are benefits to each route. mk1noob on the MR2OC put a SC12 on his NA engine and ECU. He did relatively scientific research and really benefited the community in a big way by exploring the potential of the NA ECU. It was still a work in progress and I feel there was a lot more on the table when he decided to ditch the NA ECU but it still provided a ton of invaluable and relatively well done research to the community. When someone wants to run low boost on the NA ECU I am constantly referencing his threads. Now with that said, once he stepped up to megasquirt he kinda kicked himself in the head for messing with the stock engine management so long.
All I can say is know as best you can your end goal when you start and know when and why you choose to spend the time money and energy where you do.
I would love to someday see just how much boost/power can be made on an NA ECU. It would be a fun challenge but it wouldn't be the cheapest easiest way to a high power objective.

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Re: A thread on the Facts about running ITBs on a non ITB EC

Postby ga_goosh » Fri May 10, 2013 4:08 pm

ok illhave to do more searching then. also what would you do for the itb and the cold start injector?
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Re: A thread on the Facts about running ITBs on a non ITB ECU

Postby thaison » Wed Apr 26, 2017 2:40 pm

I know this is an old thread, but I just wanted to add to it. I've been off the forums for a while, but have been getting back into 4ag's again.

Anyways, I'm currently running a AE92 Hi-Comp 16v 4AGE with silvertop ITB and T3 adaptor plate and a factory map ECU from japan. My car is imported from japan, so it was already running all the MAP electronics.

All I had to do was rewire the 16v TPS to fit the 20v TPS.

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