M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: bmwman91 on June 06, 2012, 12:40:26 PM
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Lots of very positive stories have been posted about using ITBs on these motors (with a proper tune of course). They have always tempted me, but I am getting old enough that I don't feel like swapping stuff around every year or two for SMOG inspections. Now, I imagine that it depends on the shop to some degree, but I have passed SMOG with a MAF conversion, COP conversion, slightly hacked up stock air box and a suspicious looking vacuum line sticking out of the intake manifold. These cars are probably old enough that the guy at the station just wants to see a stock air box and a cast aluminum intake manifold.
So...
What about chopping up the lower intake manifold a bit, since it is almost completely obscured by the upper part and other adjacent stuff? You could either do some heavy mods with a milling machine & TIG welder to incorporate custom throttle butterflies into the original intake runners, or maybe chop parts of it out and bolt/weld in the throttles from some other ITB setup. Maybe get the upper & lower portions extrude-honed out first to open them up (at least for those of us with displacements > 1.8L) and totally bore out everything in the original throttle body so that it is just a "shell" to look stock.
I sort of like the idea of having a stock looking motor that is anything BUT stock, one because you don't have SMOG headaches, and two because the "sleeper" type of setup is always good times. Also, I think that the stock plenum dimensions are sort of important. The M42 is a small-ish displacement 4 cylinder with little enough torque as it is. The original intake system was designed to balance mid- & high-range torque, and the various resonances created by the stock runners & plenum are part of that. I know that ITBs really help with high end power, but I think that it would be nice to trade a little of that for more mid-range torque. Honestly, if I wanted to work that hard while driving, I'd just go buy a Honda S2000 and call it a day lol.
I have played with basic slide-throttle setups in CAD a few times, and that would be the easiest way (mechanically) to get the throttle as close to the head as possible. However, all of my reading about slide throttles indicates that they are extremely temperamental, and that they are almost guaranteed to get stuck open at some point unless you service them all the time. There's a reason that only race cars use them lol...when you tear a motor down after every race, you can use all sorts of temperamental stuff like that.
This isn't something I will be starting any time soon, but I would like to start the thought process on it. I have a custom motor coming in a couple of weeks, am going to Asia for work around the same time and have a wedding in October. So, maybe later this winter I will see about picking up a spare intake manifold setup and toying around with the possibilities.
I am interested to hear what people here think, and I am especially curious to see commentary from people with "proper" ITB setups. What differences did they make, how do you like them for street-use and what are your thoughts about the use of them with the stock upper intake manifold?
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I will say one thing - the average smog guy in the bay area knows very little about old Euro cars. I passed visual and sniff in a Porsche 951 with a big turbo, no cat, chip, MAF, upgraded injectors, CAI... I have also passed with Weber conversions (replacing EFI), engine swaps - if it's old and not a Honda or Toyota, they just push it through to the sniffer in my experience.
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Haha nice. Maybe if I make a plastic cover to hide the "dBilas" logo, I can just go that route lol. In the end it would probably be cheaper than hacking up the stock stuff, although I love me some good custom fabbing!
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I've suspected for a long time that inspectors are "lightening up" on the law. Not sure about Cali, of course, but there's a lot of tea party types around here looking to cut back on any sort of meaningful DOT regulations.
Given the amount of work you're investing in the MAF conversion, I'd love to see what you come up with. Personally I'd consider a set of Yamaha R1 or R6 ITB's...driven with a Megasquirt or VEMS and nice little WBO2.
Granted, Pittsburgh is a rust belt backwater, but you should hear some of the 'louder is safer' Hardly 'tards, ricer beeotches and/or redneck truck hoons 'round here. I see it all...straight pipes, carbs, chips, Ebay turbos, you name it. Anything goes, more or less. I'm sure nobody's looking for 100% original equipment on our cars...they're old enough to drink legally!
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Some other people have passed smog in cali with the dbilas setup.
Personally, if you want to keep the stock manifold and increase breathing I would just make a big bore throttle body by expanding the size of the second butterfly valve.
Its supposed to work quite well and would look OEM. You could also possibly adapt a M50 unit which uses the same TPS.
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I want to do a extrutabody setup possibly anodized black then just make a 2 piece intake box and then add a BMW Motorsports label on the side and run it through smog bet they won't ask a thing.
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Some other people have passed smog in cali with the dbilas setup.
Personally, if you want to keep the stock manifold and increase breathing I would just make a big bore throttle body by expanding the size of the second butterfly valve.
Its supposed to work quite well and would look OEM. You could also possibly adapt a M50 unit which uses the same TPS.
Hmm...does changing the TB diameter affect the torque curve / require a custom tune? The intake system seems pretty sensitive to changes...a larger TB would flow more air, but would it screw up the tuning?
Yeah, I think that a tasteful hack-job of some S50 ITBs might work and look good. Anyone got info on that?
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Too large of a diameter throttle blade will make it hard to modulate the throttle. Think about it in terms of open area per degree of throttle rotation. The main issue is at low throttle.
Adjusting for the air is not too difficult as the AFM/MAF measures the inflowing air. Throttle position is mostly used for ignition maps to tell if you are trying to accelerate or cruise. Obviously simplified example, but you get the picture.
S50 throttles can be had fairly cheap. I was thinking of cutting off the flange and welding on a new one to fit M42 bolt pattern. I am also investigating Hayabusa throttles possibly. They are 46mm diameter throttles which I figure are about right. They can also be bored to 48mm easily if needed.
Dbilas look the most factory IMO.
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What is the inside diameter of the stock intake runners?
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Isn't the benefit to itb's largely from larger throttle bodies and shorter runners with better flow into the runners with titter bell ends?
I had considered trying to enlarge the plenum, improve the runner to plenum transition, and go to a larger throttle body setup with multiple plates on it to keep the engine more tractable at low throttle openings.
I however have been super lazy on learning the skill set to make any of this happen.
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Throttle response is the main benefit. The sound is divine as well :)
I need to measure the inlet diameter of the runners as well. I just started researching DIY stuff seriously so I am still piecing things together.
Ill put up an inlet runner diameter Monday since Im planning to work on the car and I have the upper intake removed :)
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Here's a silly idea I was working on in CAD. Yeah, this would have a laundry list of problems when it comes to making it reliable and avoiding metal shavings, but it sure looks cool!
http://youtu.be/zHlQBEQkTvA
The guide slots are curved to try to give the driver improved modulation at low-openings for better "around town" drivability. Assuming a linear-pull, the opening vs input curve is thus.
(http://www.e30tuner.com/other/thrprofile.png)
I think that a slide throttle would be the easiest thing to make, and it has one moving part which is always a bonus for reliability. I dis like them because at part throttle, you get air flow on one side only. I have been toying with a dual-slide setup where you have 2 moving plates that overlap in the center. As you open the throttle, the opening starts & grows out from the center. You can get most or all of the advantages of the ridiculous iris throttle idea, without as many headaches.
Either way, I like the "flat" throttle arrangements since it seems like one can just cut the stock runners and TIG in the new stuff, or TIG an adapter plate and bolt things in.
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Do these look like they would pass for stock looking?:D
http://s927.photobucket.com/albums/ad115/Warsteiner_photos/M42%20Stroker/
Cheers,
~Ralph
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NICE! That's the first slide throttle I have ever seen on an M42? Did you build it yourself? How does it feel compared to the butterfly ITBs?
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That iris concept is awesome!! I imgine they would need springs (possibly blade not coil) to bias the blades to prevent jambing.
For a non USA resident im going to ask a dumb question. Whats a smog test? It sounds more than a O2 sensor up the tail pipe but a full induction and exhaust inspectionwhere no mods are allowed? What if your mods reduce emmisions?
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The pic of the slides are different than the last pic with the Dbilas ITB's. I had the slides made in Thailand with the guy who used to work for Schnitzer and built the S14 motors for Ravaglia back in the day of the E30M3. I don't have the slides on the motor yet. Just finished the mating of the complete E30M3 exhaust system with SuperSprint muffler to the new header from 666 Fabrication. Next is installing the slides and tuning the MSII.
Cheers,
~Ralph
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That iris concept is awesome!! I imgine they would need springs (possibly blade not coil) to bias the blades to prevent jambing.
For a non USA resident im going to ask a dumb question. Whats a smog test? It sounds more than a O2 sensor up the tail pipe but a full induction and exhaust inspectionwhere no mods are allowed? What if your mods reduce emmisions?
Good idea on the blade style return springs. I was trying to think of how to best do that. I'd just have to extend the guide slot ends so that the control disc doesn't prevent them from closing. I think that I would also put some small sealed bearings on the little guide pins to avoid having metal-metal wear issues. Then again, it has way too many moving parts I think...the throttle sort of seems like one of "those things" that you want as simple as absolutely possible! I need a second car to play around with this stuff on and not care if it breaks!
The pic of the slides are different than the last pic with the Dbilas ITB's. I had the slides made in Thailand with the guy who used to work for Schnitzer and built the S14 motors for Ravaglia back in the day of the E30M3. I don't have the slides on the motor yet. Just finished the mating of the complete E30M3 exhaust system with SuperSprint muffler to the new header from 666 Fabrication. Next is installing the slides and tuning the MSII.
Cheers,
~Ralph
Cool! Any chance you could open them up and get some pictures of the internal arrangement? I am really curious to see what the plate slides on. I can't imagine that it is just metal-on-metal in there (maybe some Delrin or nylon guides?)! I have always loved the idea of slide throttles. There's a dual-slide concept that I worked out in CAD last night that I think could improve on the original idea a little, without adding monstrous complexity (like the iris valve lol).
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I am all about flat slide carbs, just never thought about using flat slides for ITBs before until I saw this thread. I think the combination of high vacuum at closed throttle pulling on the slides and the necessity for tight tolerances to prevent air leaks could cause issues for even a really stiff return spring if the slides are not on some kind of roller bearing. Here's a diagram of a Keihin FCR carburetor (part #20 is a roller bearing):
(http://www.sudco.com/Diagrams123/fcr_exp.gif)
Now that I'm looking at this, if cost and "stock look" weren't an issue a rack of these could be modified and used just as throttle bodies.
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Where the lower and upper intake manifolds meet up, the inside diameter of the runner is 44mm.
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Awesome, thanks!
So did / do you go to Wazzu? IIRC the school hates people calling it that lol.
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For a non USA resident im going to ask a dumb question. Whats a smog test? It sounds more than a O2 sensor up the tail pipe but a full induction and exhaust inspectionwhere no mods are allowed? What if your mods reduce emmisions?
Our laws are idiotic, especially in states that follow California legislation.
The test is a visual inspection to make sure no "emissions equipment" has been removed. That means anything between the air filter and the muffler. If that is all there, then you get a 4 gas analyzer (sniffer) put in your exhaust pipe to check for Co, hc's, and NOs.
If you pass that then you gotta show you have no vapor leaks from the fuel tank.
Some states don't bother with the inspection, others aren't as stringent on the testing. Many only care that the car meets the sniffer test.
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Awesome, thanks!
So did / do you go to Wazzu? IIRC the school hates people calling it that lol.
Yeah, I went to Wazzu (graduated in 2005). The school wanted to shed the nickname to sound more sophisticated. They did not want the name on any school sanctioned printing.
Of course after the announcement everyone started using the name, printing the name, and wearing shirts with it ect. :)
The school will never shed its party image IMO. It is a party school in the middle of the wheat fields and always will be. They just happen to have some good academic programs as well :)