39 replies to this topic

[Chuck_norris]

Hey scott, have you considered using the motorcycle fuel management to take care of tuning purposes. Say If cbr600 throttle bodies are being used, couldn't they be ran off of the original cbr ecu. Then use a power commander to tune with, the power commander 5 is avalible with an O2 sensor so it should technically learn to map itself, fine tuning could then be accomplished but using a laptop and usb cord.

[cbstdscott]

Well, if I had any confidence in my ability to deal with the spaghetti mess of wiring ecus and sensors that would be a goog idea.

Being a clueless old man, comfortable with the familiar, I am going to see if the stock stuff will work before i travel into unfamiliar territory. If it does work think how many backyard mechanics will be able to access this mod. All I am doing is improvng flow through the head. It should work.

As I write this post I am recovering from a Vegas weekend (with my wife). Wondering why Mike Tyson' s tiger is in the room.

[cbstdscott]

Shit.

The tubing I ordered is too small.

Shit.

Re-ordered. Have to wait.

Shit.

[Screech]

That is ok, my off season project is just sitting too, but due to tranny parts. I gave Acura the part number, he read it back to me. And I still got the wrong part, even the part number on the box he handed me does not match the invoice.

[regularguy]

hey scott, i found your thread about wanting itbs on your car, and i figured i would offer my two cents, although its probably not worth even that much...

 

thanks for the distributor springs btw, i am going to get on the dyno this weekend to try to get a few more horsepower hopefully...

 

the appeal of itbs is very strong, especially with honda peoples, and the sound and additional power is always a sweet affair.  the problem with retrofitting an itb setup comes with the flow characteristics compared to a single plenum manifold.  as there is a lot more throttle plate surface area with four small units versus one bigger single one.  anyone that has swapped a significantly larger than stock throttle body can relate to the more sensitive nature in the first few degrees of throttle angle.  using four throttle plates only exaggerates this effect.  while the stock ecu is assuming a small amount of air flow with a small amount of throttle angle (which is confirmed with the map sensor), the same small throttle angle with an itb setup flows a lot more and separates map and tps signals by a lot.  this usually makes part throttle and normal driving very twitchy, with fueling way off optimal, and generally makes driving below 90% throttle miserable.  this is also compounded with electrically controlled ignition systems, which is not nearly as big a problem on the stock ew engine.  i am hoping that there will be enough vacuum in the system with an itb setup to properly run the ignition system seeing as it is the only link between fueling and timing.  

 

now with a proper, capable engine management system, itb tuning can be done well and produce a great running engine that is happy in just about all throttle angles, loads, and even temperatures.  if you have ever seen a normal tuning table for fuel or ignition, there is rpm on one axis and load on the other.  load in a normal single plenum manifold is usually done with mass air or manifold pressure values, which works well for that single plenum manifold when the active cells move around with vacuum or the lack thereof.  by having the plenum, you can create a large amount of vacuum with a small throttle angle and a high rpm.  with an itb setup, it is much harder to create the vacuum, as the plenum is effectively cut down to only four short cylinders.  with an alpha-n tuning table, which is very popular with honda itb tuning solutions, the load is represented with a tps value instead of a map value.  10% throttle at a given rpm will pretty much always require the same amount of fuel.  same goes for 20%, 30%, and so on.  

 

 

 

in my opinion i believe that you could take the tps sensor and, given the scales are similar, feed it to the map and tps signals both instead of the map and tps signals individually.  hopefully the voltages will be close enough within the stock ecu tables to give you a usable base.  you could then use a signal modifier, like an apex safc, to intercept the tps signal to the map input, and adjust fuel that way.  this is all speculation at this point, and until i am able to get everything in place (if ever), i cannot verify anything.  to me, the premise seems sound, but the practice will have to be seen to make any claims.  this would be the most crude but viable solution in my opinion.  you can use things like fuel pressure or injector size alone to try to get the itbs to a happy place, but the lack of adjustments available dont sit very well with me.  

 

i am currently trying to negotiate for a set of motorcycle itbs already fitted to a stock manifold.  if i am able to get that project off the ground i can hopefully come up with a viable solution.  i already have an safc installed in my otherwise very stock 85si/ew (save for some awesome distributor springs), and the inner masochist in me really wants to fudge whatever i have to in order to get it to work.  if i am successful i will report back, but otherwise i wouldnt mind chatting about an interesting project or two.  

[dwend]

The problem with ITBs is the lack of acoustic supercharging. ITBs can only reach atmospheric pressures, a well tuned plenum manifold can produce over atmospheric pressures in certain RPMs. This extra force feeding of air creates more power. For example a Nascar engine is over 100% volumetric efficiency. My Engine in my CRX, which is a cammed d16a1 with a '92 ZC intake manifold, creates pressure in the manifold at about 4500-5500rpm. Not much only about 50 mBar over atmospheric but it is something. I bet if I built my own plenum manifold with shorter runners I would get better results in a higher RPM window. But since I want a good torque at lower RPM for good tight corner exit acceleration that are found in the smaller autocross lots.

Here is a good read on Intake manifold designs: http://www.team-inte...lculations.html

Edited by dwend, 28 February 2013 - 01:39 PM.

[cbstdscott]

Shit.

This is the type of mental heavy lifting I was hoping to avoid. Everything you say sounds valid (who am I to argue?) and I will have to face sooner or later.

Shit.

I was hoping that the stock management system would not have the partial throttle issues you suggest will happen.

At this point in the game I have the ITBs and I am confident that I have squared away the issue of vacuum. Motorcyle ITBs generally come with a vacuum line manifold (mine did). I am confident that I can easily arrange for feeds to the distributor and MAP sensor. The throttle cable connnection should not be too tough and the TPS is no problem.

My current project is to physically connect the ITBs to what is left of my cut down manifold. The two outside runners require a mandrel bent section of tubing to make a clean connection. Hopefully that bent
tubing arrives today.

I am going to lean upon the experience of others regarding engine management. I know that a modern management system is really called for in this situation, it is that this aspect of the job is outside my comfort zone.

Please let us know how your project develops and feel free to share all that you learn along the way.

Scott

[cbstdscott]

"the problem with retrofitting an itb setup comes with the flow characteristics compared to a single plenum manifold. as there is a lot more throttle plate surface area with four small units versus one bigger single one. anyone that has swapped a significantly larger than stock throttle body can relate to the more sensitive nature in the first few degrees of throttle angle. using four throttle plates only exaggerates this effect."

Wait a second!

I swapped in a larger (66mm) throttlebody and I have no partial throttle problem. And what about side draft carbs? They also have a lot of extra throttle plate surface and nobody complains about partial throttle issues with them.

I am not disputing your contention that ITBs create new problems that did not exist before and that a more sophisticated engine management system is really a good idea. But this gives me some confidence that maybe, just maybe, this wacky idea will work out.

Additionally, the mandrel bent tubing arrived. {sigh} I am not certain that this tubing will work either. But I have re-examined my first tubing purchase and I may be able to use it after all.

I will be locking myself into the metal shop at work this after noon and I will not come out until I have a solution to the connectivity issue!

Scott

[regularguy]

"the problem with retrofitting an itb setup comes with the flow characteristics compared to a single plenum manifold. as there is a lot more throttle plate surface area with four small units versus one bigger single one. anyone that has swapped a significantly larger than stock throttle body can relate to the more sensitive nature in the first few degrees of throttle angle. using four throttle plates only exaggerates this effect."

Wait a second!

I swapped in a larger (66mm) throttlebody and I have no partial throttle problem. And what about side draft carbs? They also have a lot of extra throttle plate surface and nobody complains about partial throttle issues with them.

I am not disputing your contention that ITBs create new problems that did not exist before and that a more sophisticated engine management system is really a good idea. But this gives me some confidence that maybe, just maybe, this wacky idea will work out.

Additionally, the mandrel bent tubing arrived. {sigh} I am not certain that this tubing will work either. But I have re-examined my first tubing purchase and I may be able to use it after all.

I will be locking myself into the metal shop at work this after noon and I will not come out until I have a solution to the connectivity issue!

Scott

 

 

perhaps i could clarify and elaborate a little on that issue-  it is not as much a problem i suppose as much as it is a driveability quirk.  by providing more throttle plate surface, you lose the (most likely) linear engine response to throttle input.  as far as the map sensor and air flow of the engine is concerned the first ~10% of throttle effectively ramps up much quicker.  if you ever need to modulate between 5% and 10% throttle, it is harder.  while most people will translate this added sharpness as more power, within the first part of the throttle sweep you are basically just opening the throttle faster.  if the engine is able to outflow the throttle body there is power to be freed up with a larger unit of course.  that being said, most 4 cylinder honda engines that are not built to an extreme will not be able to outflow 60ish mm worth of throttle body.  as for carbs, there are jets, pipes, and venturis that are in the way of airflow.  there are also properly sized carbs that will work for a specific flow and power demand.  it would be amusing to see someone try a 4 barrel holley carb on an ew, wouldnt it?  as for using the stock map sensor, it has been done before.  it 'can' work and im sure people have lived with it for long periods of time.  as a tuner though, i wouldnt be able to live with a car that doesnt run right most of the time and is no fun to drive.  once you get to, say, 10% throttle, all of the vacuum that the plenum manifold you would normally see is gone.  there is no chamber to create vacuum so the map sensor thinks the engine is wide open and will fuel it accordingly.  if you were to stay away from 10%-90% throttle then it would be pretty easy to get it done.  100% throttle would only need reasonable fueling adjustments and probably timing to be close enough to optimal.

 

the subject of manifold harmonics is also a very interesting subject that is very technical and partially black magic or trial and error.  it is commonly known that because a 4 stroke engine pulses rather than smoothly flows air.  those pulses can be used for good and evil alike.  there will be a sweet spot in every plenum type of manifold; the trick is designing a manifold that not only suits the desires of the engine as a whole but also makes use of that small bit of rpm that it likes to be in.  this applies to the other side of the engine too-  headers can summon the same amount of discussion.  some have been able to stumble on a design that works much better than others (given a certain engine configuration) while others keep chasing a better and better design.  venues like nascar can afford to do the r&d to test and retest different manifolds because that is very important to win races.  on the other side of the spectrum there are oem designers that have to consider much more than performance when designing anything for a car.  price, packaging, fitment, interchangeability between multiple models and fuel economy play heavily and produce a result almost always less than optimal for performance.  

 

although i am all for an itb setup on my 1g, it is mostly for the cool factor and 'because i want it'.  i can try to justify that it will make the car faster on an autocross course or it will sound crazy cool.  that will not negate the fact that it will be a bit of a headache and a lot of work to get there.  i try to validate the wants before i recommend a course of action (which usually requires spending money).  if you were to tell me that you wanted the fastest car, itbs are not the way.  if you wanted more power for your street car, pass on the itbs.  if you could get a good deal on a set of itbs from a friend and want to try it, dont do it.  if you want the throttle response for a racing application that needs it then it would possibly be worth the trouble.  if you just have to have them and your mind is set on it, 'because i want it', then sure.  just be prepared for unforeseen costs, lots of fabrication, time, effort, and down time that could be spent otherwise.  if you know what youre getting yourself into and are either smart enough to do it yourself or rich enough to pay someone that is, then be sure to post and include lots of pictures!  

 

i hope you have what it takes to go the distance-  hopefully it will be all worth it in the end.  i am willing to give some input to try to make things a little easier, and i hope you have a good camera...

[cbstdscott]

Geez,

You sure know how to take all the fun out of a project. I am in so far to this point, I will carry on to conclusion. If it really sucks, I can go back to the stock configuration. This is Next Winter's project anyway, I am planning to do the swap over to ITBs after the summer season has concluded.

But you have put the Fear of God into me about the ITBs. So with little to no expectation to succeed I can not be disappointed if the build does fail.

I am sure that people smarter than me ( which would be just about everyone in the world) have considered the problem of the stock intake manifold of the EW. What is the solution? I have a side draft carb manifold in my collection, I could go that route.

Scott

[JerBear]

Don't be discouraged Scott! You can do this, I felt the same way when I bought my car but its come a long way and I still question my choices but oh well, i'm going to push on until I finish my project. By the way, purchased my HondaTuning Mag tonight and saw the awesome section about the old Hondas!! So awesome you were in it haha, Ok, enough with the autographs. I am learning alot reading you guys bounce ideas off each other. Good luck, I know you will finish it, and write up a good DIY so not so inclined people such as myself can put on those beautiful ITBs!

[cbstdscott]

Thanks JerBear! All you have to do is show up at a show with a weird old car and they take your picture!

As I am making this up as I go along, there is a pretty steep learning curve associated with this project. I have been struggling (largely because I am stupid) with getting the correct tubing for the runners and trimming the stock manifold to the correct proportions. I have not removed the studs that the fuel rail bolts to and this has hampered my access to trimming the outside runners of the stock manifold. In the morning I will take the manifold to my favorite machine shop and have them remove the studs (they are in there pretty tight). Once the studs are out I can cut the runners to length and have them welded up.

There will be a detailed write up eventually, but I am still in the experimentation stage and I am not "ready to publish" as the research community would say.

Scott

[cbstdscott]

The bolts that hold the fuel rail to the manifold have been removed and now I am having an existential crisis.

Perhaps I should change directions again. Maybe the ITBs are not such a good idea. Maybe I should just build a single TB intake with a plenum and velocity stacks in the plenum. Awk! I am so torn. Like the heroine in a romance novel who has to make the choice between the dangerous but exciting Werewolf or the dangerous but exciting Vampire.

Screw it, I am so deep at this point to the ITBs I will stick with them. Unless... I could do both. If anyone has an extra Si intake manifold laying around I could make both and do a comparison.

When I was at the machine shop, they naturally wanted to know what the Hell I was doing with this weird intake manifold. I explained that there are no aftermarket intake manifolds available and so I was building my own. The guy at the counter said that it must be expensive to do this project and so I thought about what I have spent so far:

Motorcycle ITBs with velocity stacks- $90 on eBay
Intake manifold- $40 from junkyard
Aluminum tubing- $20, plus $20 in shipping, internet
Machine shop- $10

Welding costs- Don't know

So I am in for less than $200 at this point.

Scott

[xFactor]

See it through.  What part are you having trouble with?

 

later, matt

[cbstdscott]

What part are you having trouble with?

None of it, all of it. I really do not know what I am doing and so it is all new to me. I am not really worried about it, either it works or it doesn't. But if it does... oh man, that will be so cool.

So like the guy who climbed the mountain, "Because it is there," I am carrying on.

Scott