40mm Internal Wastegate???
 

40mm Internal Wastegate???

by our very own Cris Foogle

Yep...here it is boys. Took me a few hours, a mill, a lathe, a grinder, and well.....several moments of pondering. I wanted to stray from the whole external wastegate thing for more than one reason.....but mostly just to do something different!!

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finished making the new backplate for the Holset. It's ready to weld on the merge collector now, which will unshroud the new larger gate valve. Also mounted the actuator to the turbine housing. To get full valve opening, I changed the opening ratio by moving the pivot point on the link arm closer to the gate shaft centerline. I also am using a Banks Big Head, for it's increased spring pre-load on the gate. This is necesssary because the extra surface area of the more than doubled size of the valve would succumb to drive pressure opening before the set-point, in addition to the actuator's loss of mechanical advantage over the valve by changing its leverage ratio.

Keep you posted as the compound project nears it's end and TEST DRIVE!!



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The benefits of a larger WG are more like mandatory with compounds to keep drive pressures down. The little tiny stock WG won't cut it for higher boost apps. The drive pressures resulting from the bottleneck would make the EGT's extremely hot as well as put the head gaskeyt at jeopardy. Any advantages you would gain from more air would be lost to exhaust restriction. Most use an external gate and plumb it in prior to the little turbo. This in essence does the same thing, however.....

I think by keeping the exhaust stream more linear and through an internal gate proves better flow velocity, as well as higher heat retention than running it through an external valve and plumbing. Heat retention is highly advantagious for keeping the large turbo supplied with nice energy potential. And exhaust velocity is equally important. I opted for keeping 3" between the two turbos just for this reason, higher velocity and heat retention. Hotter gas is easier to keep moving fast, especially when not introduced into a larger pipe than the turbo outlet, and will provide a higher heat differential across the large turbo's exhaust turbine. Top this with insulated hot piping, and the energy loss from exhasut cool down should be minimized. The cold pipe between the turbos is another area of attention. I kept it at 3.5", and as short as possible, just as the compressor oulet is. Staged compression relies on a steady state of compression down the line, and dumping the big turbo into 4" just slows down the flow. Granted big pipes look cool and all, but their performance value is less than that of properly sized components. My final downpipe is 5"....which is large, but matches the turbo. This will cause a cooldown and pile up of gases, and ultimately making it more difficult to push downline. I insulated the first 4 feet of downpipe to aid in this department as well. It'll all come to a head tommorrow morning. And for those of you curious, I have about 60-80 hours of fab time in this project total....though alot of that was re-inventing the wheel on some aspects of the build and straying from the pack.

Finished off the compounds last night....almost. Still need to do a permanent air filter and some engine bay tidying, but they're functional.

You can see the roughed out merge collector to accomodate the larger wastegate that exits straight up because of the way i did the compound mounting. I like having the primary charger up on the side....both for looks as well as accessibility, and you can still get to the whole engine because nothing is crammed in a tight space. The pipes are short, sweet, and easily removable.

As for the perfomance of the gate....I tuned the secondary charger first without the coldpipe hooked to the prmary. The gate let me adjust it way down to 10 psi if I wanted, and all the way up to 40 if I wanted, so i knew I had the adjustablilty range..which means a success on the design and function. I ended up setting it for 25 psi. With the primary hooked back up, I pulled some fuel to make sure I didn't get more than 50 psi yet. Still need those O rings ya know! Drive pressures at 50 psi of boost were 41 psi, which tells me the gate is working perfectly, even with the 12cm^2 housing!! You can't ask for more than a 1:1 ratio realisticly, but this one is doing better than 1:1. The primary starts spooling at 6psi of manifold boost, another sign that the internal gate is keeping the temperatures higher without all the external plumbing and flow losses of an external gate. Combine that with the 3" inter-hotpipe for good velocity, and this package is hard to beat. The large gate showed no signs of flutter, and the big head actautor had the pre-load spring tension to keep it closed against the larger surface area it had to deal with. All in all a total success, I'll do some more fine tuning and monitoring with a few more instruments and keep you posted. I can tell you this.....temps peak at 1200 in high gear full load, instead of my previous 1600+, andf I'm still not letting it breathe to its potential. No smoke after boost pick-up, against my previous eclipse of the sun. Anyone who doesn't have compounds doesn't know what they're missing. I spent less than $600 on them, cheaper than a high end single. Even after the studs, o rings and boots, I'll still be less than a good single.

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The primary is pretty easy to hear...more through the exhaust than the compressor. It is starting to spool right off idle like it should, but by 6 psi on the boost gauge(total boost), the boost climb is much faster and you can just feel and hear the big one getting after the program. The secondary is wasting at 25 right now, but at about 20 psi, it slams the gauge instantly....well almost. I've got it cut back to 50 psi till i finish the prep work....you like that? PREP WORK. Before I cut it back, there was no way to cut the throttle quick enough...I actually saw it pin the gauge....that was enough. Its a hell of a ride though....breaks the 12.50's wide open shifting into 4th on dry pavement even.

My fueling mods are listed below, pretty basic, though i have the 100 pulled back to about halfway right now to control the top end boost. Can't wait to full fuel it. I was always afraid the 160 pump didn't have the poop to really fuel compounds, but I've been pleasantly surprised. I think once I can let it full fuel, I'll have all the power I think( ) I want on the street.

There's just too many variables to account for with this custom turbine housing to just make another and send it out, otherwise I would in a heartbeat. They're not hard to do however, and I will gladly steer anyone who is into trying to make one.

The wastegate on mine contols only the secondary (little one). Becasue the secondary is the second stage compressor, lowering it's wastegate opening psi will effectively lower total boost, becasue you are taking the wind out of the second compression stage. The primary (big one) will only provide "x" amout of pressure, then the secondary re-compresses it again. I could get my total boost down to as loww as 40, but it was laggy waiting for the primary to spool without the help of the secondary. The sweet spot was around 27 psi of boost out of the secondary. It provided a seamless boost transition and made the best power. To control top-end boost, I merely pulled the plate back some to keep the primary in check. Without a wastegate in the primary, it's the only way to really lower top boost without making a lag, and poor boost situation. I am at 50-55 now on a stock gasket and bolts...very edgy, but it's a calculated risk, and I pick and choose my high boost times very carefully. I have also turned off the meth, and have backed the timing down to 15*...all to decrease cylinder pressures some. Very soon I will have the funds to do the rest of the job.

I think a 35 does fine for a decent set of street twins. An HTB2 would prolly be good as well, as long as it didn't hurt the low end spool up. That's the biggest killer in twins, is a secondary that's too slow to get going. The primary relies heavily on the high exhaust volumes and flows that the secondary provides in the lower end. I think that's why mine is starting to spool right off idle, and making boost by 6-8 psi of total boost. It's VERY smooth, I like it alot. Experiement a little, but I would think the 35 would be better for now, at least until you can get the headwork done. But, if you get to close in compressor sizes, you have killed the theory of compound compression. You need to keep some distance in size between the two, and correct me if I'm wrong, but an HTB2 is getting pretty close to a BHTB3's compressor? Now if you upgraded the primary to an even larger one...well then

I bought a BHTB3 from Turbo Supply. It's a Schwitzer model 167050.....$475 outright brand new no exchange. Pretty hard to beat. It does spin clockwise, so factor that in to your plans. As far as what engines use it, I know of Cummins 855's, late gen big cam 350's, and a few others that I can't remember. It's a very popular turbo, which is why it's so cheap.

12valve......unfortunately I don't have access to a dyno other than my levi's....but hope to make a trip south soon to check it out. Probably at Fast Specialties in WA. No 1/4's either.....there again, hopefully in the near future. The internal gate stock is around 17mm I think? I opened it up on the mill to 40mm, then made a new valve and actuator lever to increase the ratio so it opens full wide at full pressure. You'll have to relieve some of the inner scroll wall to unshroud the new opening, but there's plenty there to do it with. I also removed the devider down to the end of the gate opening to make sure it had a nice clear path, as well as gate the front 3 cylinders, unlike the stock one does. The BIGHEAD actuator has it full open at 50 psi, and 3/4 open at 40, though I still have a controller to fine tune that. The first thing you have to do to the turbine hsg is mill the entire gate area flat to get rid of the machined surface already there that is small. Then where the shaft comes through the inside, mill that wall flat as well, getting rid of the hump that lives there factory. You will then make a new shaft and weld the old actuator link to it. I shortened the link to change the ratio to allow it to open farther for a given diaphram travel. Then you will HAVE to make a merge collector, or "megamouth" to clear the new valve....scrap the stock back plate.

WideOpenThrottle....yeah the battery went bye bye. I moved them both to the bed. Eventually, I am going to re-wire and re-plumb the entire engine bay, remove useless studs and holes, and re-locate the PDC and various relays and solenoids. I want to see nothing but clean CTD and the go fast parts whenthe hood id opened. I also removed all the AC components, as we don't need it here anyway. There are 3 90's between the primary and secondary turbines, and yes, I was worried about the detriments of doing it that way, but I kept the interstage hotpipe down to 3" to keep velocity up, double wrapped it, as well as eliminated the external gate and it's extra plumbing to keep the heat up. I don't have another truck set up conventionally to compare it to, but my data shows it is working out okay.....at 50 psi manifold, the drive pressures at the inlet of the secondary are 40 psi, the primary is in full spool by 15 psi total boost, and is lighting at 6-8 psi total boost. I wanted a side mount for a couple of reasons....obviously to show it off some. But more importantly when I install the second intercooler, the plumbing will be very easy compared to having it below. I went with the 26 turbine housing. I would like to try a 22 just for the hell of it, but I can say this combo is potent. Boost climb is so fast you can't even react to pulling off the throttle quick enough, and there is absolutley NO waiting for the compression stages. I had to back out the fuel plate to keep the top end in line 'till I stud up. I'm pushin it at 50, but I've seen it pin the 60 lb gauge before I took some coal away from it. I even think I heard the needle hit the pin...LOL. The boost is perfectly seemless. I have the secondary gating at 21 psi, which is perfect for its map. I'm plumbing a pressure gauge between the stages to see exactly what the primary is up to, but my Intake temps are hovering around 110* full power without the meth on.

A 5" straight piped compound set-up is absolute music.....the second turbine really mellows out the note, and that primary turbine whine is really something else out of the exhaust. At times, you can hear both turbines at the same time, just a little different pitch from one another, and THAT's a very unique sound that turns heads.

Later guys.