dpf22

I'll have to do it. Its easy enough to disable thats for sure. Without the vacuum source, they stay open letting the secondary throttle plates do their normal thing. I plan to document it of course. It will be a ways down the road as I am still putting this motor together lol. Perhapse toward the end of the summer, possibly sooner.



dpf22

ColinRX7

He's starting to sound cheap since some guy on the internet kept saying he was the best there ever was...



I thought the best ones weren't on the internet.. at all.. like no mention of.. anywhere on the internet... Jim?

ColinRX7

Anyways, I tried throttle staging. I didn't think about using air/vacuum actuation. I modified linkage to stage the secondary throttle plates to open at 1/4 throttle, and then open at a different ratio than the primary plate so that by the time 100% was reached, all the plates were wide open. I was designing this for the street, to be used with cruise control. Once the car was up to speed, I didn't want the excessively late port timing the secondary runners were bringing, and try to conserve fuel on cruise. Wouldn't need any more than 1/4 throttle max on cruise, right?



I canned the idea, because I decided to can cruise control altogether on the car.



So, you're boosting aren't ya?



Why don't you operate the plate opening diapragm with a vacuum line from behind the throttle plates? Because the third set of plates is in front of the actual throttle plates, right? Setup a diapragm with linkage that closes (or almost completely closes) the plates at 0 pressure or vacuum, and then as you come into boost the plates open with pressure from the compressor. When you let off throttle, the intake manifold has a vacuum surge and closes your third set of plates. This means you'll have a variable open rate third set of plates that is directly proportional to intake manifold pressure. Now you won't have monster huge secondary runners slowing velocity to a crawl until boost kicks in to where it was designed to run (everybody is always shooting for pure HP). Sounds like a cool tuning trick to me. What time does your boost kick in anyways? The plates will always open in the same manner related to the boost pressure, so it won't matter what kind of fuel map you run with the megasquirt with the extra actuation options. You always need more fuel with more air, so make your air intake control depend on itself for accurate third plate opening. If you went this route, you'd just want to make sure your secondary injectors are staged before boost gets too high. If you can handle that, you're golden, the system handles itself, now you just have to worry about hammering out the rough edges of your fuel map. If you try to setup an electronic actuation mechanism, you're converting forms of work, and it will compound the types of problems you could potentially run into.



But, I know, those megasquirt features are attractive. I love the MS unit... Haven't looked back since I got it.

dpf22

Mostly I want to operate them later than what you described because i can actually "Tune" the way the powerband affects other aspects. It can also be beneficial to boost pressure threshold. I personally feel that velocity is directly related to rpm more so than boost pressure. I want to keep the secondaries closed for as long as I think it will aid torque by keeping the velocity higher in the primary runners when I decide to slap them open. We'll see. I will definately be doing some dyno test&tune with this to see how it will affect the powerband. I have been told by a few good rotarheads that this will be a great step in the right direction. If anyone wants, I have the assembly all ready to go so its sitting on my work table and I could post pictures of how I'm doing it. In fact, I'm going to get some pictures now and see if I can make them fit here.



dpf22

dpf22

Ok, took some pictures real quick for reference. Keep in mind that i don't have the electronics or any vacuum lines hooked up because my engine is still in the build process.

Don't laugh at my porting. I'm not completely done(and I refuse to knife edge the entries). I just left it mocked up for visual purposes and to see if it all fit. Its kind of a rig job, but fits real well. I am stuck with using the S5 throttle body because I use the full range portion of the TPS with my megasquirt for throttle enrichments.

Its really simple the way its set up. I took an S4 third throttle set from an old throttle body I had laying around. Put the shaft in with the butterflies, and drilled the alignment dowel in the center of the diaphram out to bolt where the rear (or front most) bolt of the tps bolts down. It actually worked really well. Right now the diaphram is ripped (20+ year old rubber). I don't plan on subjecting the diaphram to boost pressure. Rather, I will simply use a check valve so that it can only have vacuum (which closes the secondaries)and a solenoid to divert the vacuum back to the atmosphere when they open. This system has one flaw in that it will be entirely rpm dependent with no throttle position basis at all. I have to find some way to not have a vacuum leak at high rpm low throttle (cruising on the interstate) situations. I may have no other choice than to subject it to boost pressure.



Anyways, here's the pictures...

dpf22

Damn! The pictures are soo large that I can only put one at a time. Ah well, here's another...

dpf22

And another...

dpf22

And the last. First one was obviously throttle plates open (no vacuum) Second, the linkage of the same. Third was simulated vacuum closed lol. This last one is what they look like as such (at anything lower than the preset rpm).

ColinRX7

Nice work.



You know, I used an S4 throttle body, and modified it to fit a 1994 mustang TPS. It's a D shape type full range TPS, in stock at most parts stores, and only 20 bucks. All I had to do was weld one of the nuts on the shaft, and then shape it with a zipdisc and sandwheel so that the end of the shaft became a full D shape, slip the TPS over the shaft, and clock the TPS mounting to fabricate a bolt on bracket out of tin.



[attachment=43861:tps.jpg]



That's an S4 TB with full range TPS.



I like the check valve idea, but I think the obvious answer is to expose it to boost. It's really not that big of a deal, you just need to make sure the diaphragm isn't going to tear (perhaps think about diaphragms on other engines in the USA that are exposed to boost and are of the same general dimensions and workload). If you did, you wouldn't need a three port check valve anymore. You have one solenoid valve, two ports, normally-open type. Can you not include in a stipulation that under acceleration output (the megasquirt does recognise this as an operating condition), that the check valve will remain shut? If accel, then energize. If idle, or if decel, or if RPM > xx variable, then de-energize. If the solenoid isn't energized, the remnant boost in the line that's leftover from the valve being shut will get sucked behind the throttle plates under vacuum (since you let off the throttle), and recharge your diaphragm to a negative pressure and shut your plates. If you reach the RPM variable, the solenoid deenergizes and allows boost pressure to push and hold the plates open.



Only problem with that idea that I can see is the plates will open abruptly. I thought with the diapragm being controlled by manifold pressure exclusively, you could have a smooth transition to have peak velocity until neccessary. It would suck to have the car buck when the plates open up no matter what scenario at spec RPM, in which case it would make room for improvement after you already completed the project. I'm not digging the huge snap open, but I could be wrong about it.

dpf22

lots of cars have a snap open type of secondary throttle plate system. All of the yamaha heads on the taurus sho's and the TVIS system on the 4age has them doing that. The mustang cobra 4.6dohc has them snap open. VTEC isn't exactly progressive, or VVTL-i (which also had dual runner intake as well) for that matter. All of these systems have a sudden rapid change in volume to the intake system.

I'm not worried about the snapping portion of it. I can adjust fuel in that range for it. The output for this particular solenoid will be rpm based ONLY. I cannot write code, nor do I have the inclination to learn to for this in particular.

Also, the way I will be running it will have the solenoid in between the check valve and the diaphram (in a T) which will shut the plates every time I let off the gas and there is vacuum. Thusly leting the velocity increase on shift (assuming I lift). The solenoid would be normally closed decreasing the load on it and the electrical system as the "on time" will be less that way.

The only thing I am worried about when exposing it to boost is the diaphram ripping. I don't plan to let the plates open as boost comes on. I want them to open at a higher rpm than boost threshold for a reason. As I said before, velocity isn't pressure dependent. It's rpm dependent. Engine literally moves more air in and out at higher rpms than it does at lower.

As for the s4 Throttle body, I would use one but the one I got the parts from had been butcher'd before I had it. I didn't have all the pieces. Also I have 2 fully opperational s5 throttle bodies that I had laying around. One that I had done some minor porting on. This works for me, and since its on the cheap... Its even better. I literally had all the parts I need in my garage.

I will promise that I will get some dyno numbers on this and post them this summer. The car is undergoing some major changes that require a lot of my money and time. And it's taking a lot of time to make the money, thusly taking a while to get everything done. My main goal is to have a fatter, earlier torque peak, and possibly to help the hp numbers a little bit with this mod in particular.



dpf22