Update on Roller Barrel ITB project for STI

[Specnomore]

Nice, what are you going to do about your radiator? Im assuming that your going to "v" mount it so you wont have all that hot air hitting your intercooler. It also looks like one of you plenums is blocking the turbo inlet, but that just could be the angle of the picture.

[wgknestrick]

Radiator is almost done as well. It is a copper Jeep Cherokee, 3 row radiator that is modified to fit the bumper. It looks just like a FMIC. 10" X 36" X 2". Jeep Cherokees are the only vehicles that have radiators this size (short height and wide).

Hopefully it hold up in a high impact area that low.

[wgknestrick]

[Ender81]

Wow looks like it's coming along nicely. How is it going with the throttle bodies?

[wgknestrick]

One of the housings was F-ed by the machinist last week, so he had to make another. Parts are about 80% complete at this point (they ship to me around 90%). They will be finished up by my co-workers once I get them.

I still have a good deal of work on the IC (mounting it); Radiator (plumbing it /painting/mounting fans); ITB synchronizer (back to drawing board); stock TB (have to modify to actuate synchronizer); manifolds (bead blasting interior/exterior/powdercoat), Running fuel lines / vac lines.

We'll see. Getting the manifolds complete before I even have the ITBs is pretty good. This is a big, big project.

[italianblaze]

you are a subie god

[naDintheHat]

Originally Posted by italianblaze

you are a subie god

Hell yeah he is. Not only does he have a bad ass car he took the time to show a fellow subie lover ( a newb) his car before this major work and even took him for a ride. Big ups to Bill, this thing will be sick when it is done.

[sisforsurfing]

Originally Posted by wgknestrick

This is a big, big project.

You're not kidding. I love seeing the progress, and you've gotta be excited it's at least moving along. Good luck with everything.

[HKS83]

I hope for your sake that this isn't a daily driven car. Barrel throttles offer no fine throttle control like conventional butterfly shafts do. Just like the XFE from Cosworth, theyre only suited for full throttle or no throttle situations. Eitherways, you did a killer job on your prep work. :]

[wgknestrick]

Originally Posted by HKS83

I hope for your sake that this isn't a daily driven car. Barrel throttles offer no fine throttle control like conventional butterfly shafts do. Just like the XFE from Cosworth, theyre only suited for full throttle or no throttle situations. Eitherways, you did a killer job on your prep work. :]

Mazda guys have used these quite a bit as well as the Honda engined lotus track guys over in the UK. They really don't report fine throttle control issues that you speak of.

Just for reference, here is a flow chart of roller barrel ITBs versus butterfly ITB with respect to throttle angle:

http://www.lumenition.com/roller.pdf

If you look at the graph towards the end of the document, you can see that if anything, barrel throttles are more linear than butterflies. I think you might be confusing these with slide throttles which have these problems.

[liberty2000rs]

Very Nice setup!! It's always great to see somebody doing something different!!

I wondered if you've done any reasearch on Plenum size when using ITB's and how it is different from Single pre-plenum throttle bodies.

We experienced something we didn't think would happen with a turbo 1000cc snowmobile recently which makes me wonder if it's a unique problem because of the fuel setup (propane) or if it's a common occurence with ITB FI engines.

With a larger plenum (1.5x the volume of the engine) we experience a bad throttle off flat spot that would almost kill the engine. We tried to tune around it with fueling changes and timing changes but never could get rid of it. We ended up going to a smaller more shallow roof plenum which completely solved the problem. The plenum is now roughly .8 x the displacement of the engine.

This could very well be caused by the propane system, I just wondered if what you had researched showed anything similiar to what we'd found on the sled, that with ITB's a smaller plenum is necessary.

[wgknestrick]

That sounds more like a tuning / ECU problem than anything. ITBs have "problems" running rich right off throttle because with most MAP based ECUs the vacuum goes right to ATM (which would indicate a higher load and therefor way more fuel than is necessary). I say "problems" because is isn't really a problem if you tune for it (and know it's going to happen). You just can't throw ITBs on a car and expect nothing to have changed. ITBs still have a bad (and un-earned) rep for consuming a ton of fuel, although that excess fuel used isn't really necessary a function of the ITBs, but a function of improper tuning.

Granted I don't have much information to judge your setup, nor much experience with 2 stroke, or snowmobile engines.

You might have changed a major variable thinking it solved the problem. While really a "small" variable changed with it that was the actual solution. I would bet that you changed something critical with how the ECU reads load to fix the problem (TPS or MAP), not the actual size of the plenum.

There just isn't a theory behind the plenum volume helping solve your problem.

I just can't believe you can run a turbo on a 2 stroke engine for very long time. I would think that EGTs would be extrememly high, but it is something that is very foreign to me (2 stroke tuning).

[liberty2000rs]

Originally Posted by wgknestrick

That sounds more like a tuning / ECU problem than anything. ITBs have "problems" running rich right off throttle because with most MAP based ECUs the vacuum goes right to ATM (which would indicate a higher load and therefor way more fuel than is necessary). I say "problems" because is isn't really a problem if you tune for it (and know it's going to happen). You just can't throw ITBs on a car and expect nothing to have changed. ITBs still have a bad (and un-earned) rep for consuming a ton of fuel, although that excess fuel used isn't really necessary a function of the ITBs, but a function of improper tuning.

Granted I don't have much information to judge your setup, nor much experience with 2 stroke, or snowmobile engines.

You might have changed a major variable thinking it solved the problem. While really a "small" variable changed with it that was the actual solution. I would bet that you changed something critical with how the ECU reads load to fix the problem (TPS or MAP), not the actual size of the plenum.

There just isn't a theory behind the plenum volume helping solve your problem.

I just can't believe you can run a turbo on a 2 stroke engine for very long time. I would think that EGTs would be extrememly high, but it is something that is very foreign to me (2 stroke tuning).

I can understand where you're going with your theory, and because of the fuel setup it very well could be an explanation.

The motor is however a 4-stroke 1000cc Apex (similiar to a yamaha R1) it's sleeved with 9.5:1 forged pistons and some other goodies.

The sleds run on a "carburated" propane setup, it's completely pressure based and uses a diaphram to regulate/measure fuel, and the fuel/air mixture is created pre TB. It uses four butterfly TB's. All settings were Identical, and back to back tests were done, the only variables that changed were the weather and the manifold. It may be worth noting that the bottom plate on the manifold was changed from a flush velocity stack to a stack raised 1" off of the floor. The volume of air needed to fill the stack was also calculated and the plenum built in acordance to fill each stack.

The interesting thing is the manifold setup was changed on three different sleds all with the same problem, all of them ran flawless after changing the manifold.

I don't know much of anything about the physics/thermodynamics behind an ITB setup which is why I asked if you had come across any relevant information that could help better understand the situation.

Regardless, your setup is awesome and I'll be anxious to see the results, good luck

[Supraholic]

Great work, +1 for your efforts. Although this setup will gain you mad props on the local shows, it will not offer a lot of gains on a Forced induction engine. This design is most efficient on naturally aspirated engines. You should see a slight increase in performace at WOT, normally 20-30 CFMs for combined runners on FI engines depending on the size of the ITBs. But also you have to take into concideration volumetric efficiency of these engines. There is only so much air they can processed per cycle. Either way, this is a great setup and certainly very very rare. Congrats.

[wgknestrick]

ITBs shipped today from the machinist. They are mostly complet, but the sides and injector bores need to be finished up once I get them.

[karl]

those itb's are lookin great!

[BradC]

Originally Posted by wgknestrick

Wide-the-hell-open right there man, that's great

[Honest_Bob]

Holy **** dude.

[Raven18940]

Originally Posted by wgknestrick

No you are absolutely right. This is the huge difference between the 4g63 and the EJ engine. Subaru heads suck. They are about the worst heads of all the Japanese companies and they always will be until they totally redesign them. Subaru heads are so bad because they have un-equal length exhaust ports INSIDE the freakin heads. Most companies refer to this as the "dog-leg" port on cylinders 2/4. Try to get 2 different length and shaped ports to flow the same inside the same head, good luck

And people wonder why I prefer SAAB's engine to Subaru's.

I've read through most of this thread and I'm really impressed. I only have a couple issues.

1. How were you planning to synchronize the throttles? I see the bars to move the throttles, but are they easy to adjust?
2. How will the engine idle? Is there an idle circuit or will the throttle be partially open?
3. Put a copyright on your design you fool! Right now!

[wgknestrick]

Originally Posted by Raven18940

And people wonder why I prefer SAAB's engine to Subaru's.

I've read through most of this thread and I'm really impressed. I only have a couple issues.

1. How were you planning to synchronize the throttles? I see the bars to move the throttles, but are they easy to adjust?
2. How will the engine idle? Is there an idle circuit or will the throttle be partially open?
3. Put a copyright on your design you fool! Right now!

There is more to a car, than just the engine (however it is a big part). To me Subaru has the best rounded car you can drive, with a huge fun factor.

1. This is still somewhat undetermined at this point. I kind of need the ITBs in hand, on the engine, before I can finalize things. I am going back to a lever system however from 2 flexible shafts (not accurate enough + bind). I have the layout complete, just need to finalize what Mcmaster parts are needed.

2. This is much easier of a task since I am retaining the stock drive by wire and TB. Basically I modified the stock TB to mount a central lever on the shaft. the car thinks it still has the original TB, but this now drives both sides of ITBs. The idle is handled by closed loop PID control (on the Hydra) of the TB opening. I can set target idle and it adjusts throttle angle to maintain target RPM.

3. We'll see how things go first.