E30 Zone

I have been posting about this build on a couple other E30 forums. I don't frequent here as often so I didn't really think about posting it here, but I figured you chaps might fancy a look at what I've got going on, and as always I value a good technical opinion

I've been wanting to try my hand at a DIY ITB project for a little while now, and now that my 2.8L stroker has been up and running for a summer I figured that while it's away for the winter I'd try and hash out a design.

I've seen a handful of DIY M20 ITB set-ups on-line but I haven't come across very many well documented builds, and the one big thing that's usually missing is before and after dyno plots. I'm hoping to take my stroker to the dyno this spring and get some tuning done with the stock intake manifold, and then swap over to the ITBs and see what they can do.

My goals for this project are as follows:

- as always it's a budget build so try to keep the cost down by doing as much as I can on my own
- try to retain the stock brake booster if possible (most DIY set-ups I've seen are running a brake booster delete or remote booster)
- design the manifold so that it will be possible to try different size throttle bodies in the future if at all desired
- If I'm really feeling ambitious I may play with different length velocity stacks

So the first thing I started with was finding some throttle bodies on the cheap. From what I've read, people seem to say that 38-40mm throttle bodies are what should be used (That's a whole thread on it's own so I'm not going to get into it here). From what I've seen GSXR 750, or BMW K75/K100 throttle bodies are good picks because they are in that size range and separable. However, at the time I was looking on ebay for throttle bodies there wasn't much available that fell into the price range that I wanted (aka dirt cheap lol). Then I came across some 2006-2009 Triumph Daytona/675 throttle bodies which seemed plentiful and some sets could be had for dirt cheap. The motorcycle aficionados amongst you will know that those bikes are triples, so two sets would give me 6 throttle bodies. The throttle body diameter is 44mm which is on the larger side (according to what people say) but they were so cheap that I couldn't pass them up, and since the manifold design is going to be somewhat modular, I could always try some smaller throttle bodies later if these happen to be junk.

I was able to pick up two sets for $55 + another $55 or so for shipping so $110 (US dollars) for 6 throttle bodies. They are separable and look like this...





Then I set about hacking up the manifold from the motor I pulled when I swapped in my 2.8L stroker...




And that's when I had an epiphany.... I could mount the throttle bodies vertically and then cut my hood and run huge stacks out the top!!!





How gangster would that be......














...not very gangster in my opinion so I continued hacking and after a little skim on the mill I ended up with this...





Now, as you can see the issue I had was that due to the angle on of the first and last runner the cross section of the cut is larger and that would pose a problem when going to weld on some new runner extensions. Using a straight edge I estimated roughly how far down I'd have to machine the runner for it to have roughly the same cross section. I'd like to retain the stock fuel rail mounting provisions if at all possible, so I'm only going to machine down the first and last runners and then make a decision as to whether or not the silicone couplers I plan on using will be able to compensate for the slight variation in angle on the two runners. The black line is roughly where I need to machine down to...



After that I wanted to take some measurements off of the car and develop a CAD model so I could come up with a rough design concept to check my clearances. Since it's hard to take measurements off of the car with all the wires and tubing in the engine bay in the way I decided to just use copper wire and touch off some key points relative to the manifold then cut the wire and attach it to the motor I had on the engine stand...



Point A (the horizontal piece with a small bend downwards) represents point on the brake booster that is closest to the intake manifold. Point B (the point where 3 wires come together) is a common point on the brake booster that will allow me to constrain the brake booster in my CAD model. Point B is also significant because I chose it by touching a wire off of a lower stud on the manifold and then laying it tangent to the brake booster. So as long as I can stay above the lower of the three wires I should be able to clear the brake booster. Finally Point C (the tip of the vertical wire) is a reference the lowest point on my strut brace that I could interfere with.

Then I took a side view holding the throttle bodies up at an angle that I thought might work and I imported it into autocad and scaled it so I could draw on it....



That way I was able to find roughly where the centre of the brake booster was as well as roughly what angle I will try out when I mock up the manifold. A 24 degree angle seems as though it will work.

The next step was to get my model going. I came across this drawing for the flange on some Swedish website for boosted cars...



The rest of the measurements I just measured off of my manifold...






Adding some 1.75" x 0.125" wall tubing cut at a 24 degree angle. (The cross section of the 24 degree cut happens to match up fairly nicely with the cross section of the manifold). Also the tubes on the first and last ports are at a slightly lesser angle in order for the tips to match up.




I roughly measured up the throttle bodies. In this picture they are spaced on 91mm centres just like the intake ports...





Putting it all together with some 2" to 1.75" silicone reducers looks something like this...




And with a rough estimate of the brake booster (I'm not actually sure of the placement of the booster depth wise but that's not really the limiting factor in this case)...




One observation that I had was that the outlet of the throttle body is actually roughly the same size as the cross section of the intake runner...




Unfortunately it's in the wrong orientation and off centre of the throttle body axis. It creates this situation in the transition...



I can blend the transitions so that going into the engine the air flow won't hit any steps, however any reversion will encounter a fairly big step at the exit of he throttle body. I'm not sure if this will have a positive or negative effect. It would be possible to bore out the throttle body so that it's round however I'm going to leave them be for now.

That pretty much brings me to where I am right now. I've ordered the silicone reducers as well as the aluminum tubing so it'll likely be a couple weeks before I'll have anything to update. However in the mean time I'm going to investigate potential methods of coupling both sets of throttle bodies and I'll work on making the spacers needed to space the throttle bodies as well as modifying the throttle syncing tabs to compensate for the spacing. One other consideration that I'm mashing around in my brain right now is making custom velocity stacks. I'm thinking of bringing them out at an angle towards the front of the car like this...



The reasoning is that it will allow me to have longer velocity stacks as well as afford me more space for air filters. However that will be on the back burner until I can get some test fitting done on the car.

(JUST A NOTE: I'm copying and pasting my posts from another forum, so the timeline is a bit off obviously )

Small updates:

The aluminum tubing showed up a couple days ago, so next week I'll cut a couple pieces and get them tacked on to the manifold in order to check clearances. I also made up a set of stainless steel spacers to space one set of throttle bodies...



I'm still considering what approach to use to extending the throttle sync tabs. Right now I'm thinking that since it's only 8mm they have to be extended I will just build them up with weld and then just grind them back down to the proper thickness. If that doesn't work I'll have to cut off the current tabs and fashion a small piece out of flat bar that can be welded on...

Modified one of the tabs the other day. One side was removable so I was able to cut it and weld on a piece of sheet metal...




The tab on the other side will be a bit more difficult because it can't easily be removed.
Last night I started prepping the manifold to get a couple runners tacked on for test fitment. I didn't get any pictures of that though.

So I modified the other tab on the throttle body yesterday, it was a bit trickier since I had to weld it while it was still attached to the throttle body. It turned out ok, it ended up being a bit twisted after welding so I had to bend it a bit. However it seems solid and should work fine...




I was also talking to the guy who's going to be welding the manifold and he expressed concern that the manifold is going to get pretty hot and could end up twisting because there are some thin parts in what's left of it. So to avoid any issues with that I made a fixture out of a piece of 1/2" steel flat bar. I threw the piece of tube on there as well to give you guys an idea of what that will look like...

Some updates for everyone....

Yesterday I got two runner extensions tacked onto the manifold. As you can see I've done a bit of work to the manifold hogging out material. That's so the end of the runner matches the ID of the extension.




I'll be going back once things have been fully welded to blend any remaining ridges...




If you have a keen eye you'll also notice that I knife edged the extensions. That's so that inside the silicone coupler there won't be a step for the air to run into...




Tacking on those two extensions allowed me to do this





First thing I noticed was that the dip stick tube was barely clearing the throttle bodies and would probably be an issue once the v-stacks were put on...




Yeah, that's not going to work....




Solution: Use the box end of a big wrench to make a number of small bends at a few points along the dip stick tube...




End result: I should be able to make it clear in the car...




Then I started thinking about joining the two sets of throttle bodies so that they can be operated by a single cable. I popped off the end cap as well as the TPS....




My initial thought was to replace the nut on the one side with a threaded stand off. Then machine a part that I can thread into the stand off that has a slot on the end that which will mate up with the tab that actuated the TPS. That way I'd be able to adjust the coupler then lock it down with a jam nut.

My concern was that the shaft is made out of brass and that tab is pretty thin. That tab was only ever meant to actuate a TPS, not deal with the stiff torsional loads from the return springs or the shock loads from mashing the throttle open and closed, I felt that over time that could become an issue, and if it were to break then my car would only be able to feed three cylinders with air.

Then I started contemplating the throttle cable situation. With the way I currently had the throttle bodies mounted the cable would have to pull downwards in one of two spots to actuate the throttles...




I could probably use the throttle cable that came with the throttles and loop it around and up to the valve cover to whatever bell crank mechanism I come up with.


Then I was like hmmm.... what if I turn the throttle bodies upside down?




That way the throttle cable is up top. I thought to myself, that looks promising! Not only that, but all of the clutter from the vacuum lines will be hidden on the bottom side. It might be a bit tricky to get at the vacuum ports to sync the throttles, but I'll really only have to do that once....




That does look cleaner! And I can use the screws that the bike's fuel system was attached with to do some cable/hose management with the engine harness...




Then while I was playing with the one throttle cable I thought to myself... well what's stopping me from running a second cable right to this spot and just joining the two cables together so that they can be actuated with a single cable... so I threw a cable on the other set....




Now this I like! With this set-up I no longer need that coupler that I was feeling sketchy about. I figure that it shouldn't be too hard to make up an assembly that I can bolt to the valve cover where the manifold support brace use to mount that has a bell crank with two different diameters so that I can get proper pedal travel. I can probably even make it so that I can retain the cruise control




So that's pretty much where things are at right now. The next step is to test fit it on the car so that I can find out what's in the way... because there's probably something in the way lol. I'm thinking that I am definitely going to have to do some massaging of the hoses that go into the heater core. I was thinking about going to where I have my car stored and pulling the manifold off to test fit, but that will end up being more hassle than I want, so I'm likely going to put things on hold for a couple weeks until the snow melts enough so that I can get my car out and bring it home.

Just to make it look sort of complete I threw the other couplers on and tilted the motor to the angle that it sits in the car. A couple more pics...







Cheers.

looks great and interesting, i'm also planning to build itb's in the future. but what is the real benefit of itb's? still not clear for me.

Steven

Steven320 wrote:looks great and interesting, i'm also planning to build itb's in the future. but what is the real benefit of itb's? still not clear for me.

Steven

It seems odd to me that you are planning to build ITBs in the future even though you don't know what they do... you just know they are good haha?

In a nutshell, ITBs will improve throttle response, and if done right (when coupled with the right cam and some head work) they can give you some nice gains on the top end.

Oh and they make your engine bay look pretty sweet too

Excellent work there mate hope it works out for you! Looking forward to seeing the finished product

Great project, thanks for sharing it with us

i know what they do and are capeble of but i was more meaning of how do you think of it most people just say something en expect high gains. and is it worthy enough to spend time and money in it. sorry for my bad englisch btw.

Steven320 wrote:i know what they do and are capeble of but i was more meaning of how do you think of it most people just say something en expect high gains. and is it worthy enough to spend time and money in it. sorry for my bad englisch btw.

That's why I said "if done right they can give you some nice gains"

It's easy to slap some ITBs on a car and lose power because the system isn't designed well.

Part of the reason I'm going through this exercise is because I haven't really seen any well documented M20 ITB projects with before and after results.

My set-up may end up working well, it may end up being junk, but at least we will find out

the ITB doesn't make any WOT power they work only under transient throttle situations. It is the geometry change that is possible which makes an ITB system work (when done correctly) and there is lots of info about what geometry should be used

So I brought the car out of storage yesterday. I took it for a rip around the block just to get a little taste before it would be going on blocks for the next few weeks. First order of business was obviously to drain the coolant and pull the intake manifold so that I could test fit my ITBs...





Over all I was relieved to see that everything fit into the car more or less how I predicted it would. The set-up clears the brake booster and will clear the strut brace when it's in place. The only real interference is with the upper heater core hose which I already figured would be an issue.




However after looking at it, it shouldn't be too hard to reroute. If I can find a hose with a tight 90 degree bend I can run the upper line down behind the booster, either that or I'll trim the rib on the tip off of the inlet and solder on a 90 degree copper fitting that I can attach a hose to. Now I just need to figure out the throttle cable set-up as well as what I'm going to do for air filters. The angled velocity stacks are still on the table too.

Happy Easter

i dont want to rain on what is a great looking project but one of the essential components to successful ITB conversion is air velocity, without that the engine will just loose power everywhere and its the most common mistake made by nearly everyone. Try to keep the manifold extensions and rubber joiners small as you can.

even if you dont gain much power the SOUND is so worth it!

The manifold extensions are more or less as short as they can be in order to get the angle I want and have meat to clamp the silicone reducer, they are roughly 2" long. I've also trimmed back the silicone reducers a bit as well.

I'm currently just working on the throttle linkage. I also rerouted the upper heater core hose down behind the brake booster, it no longer interferes with the ITBs.

Bullet_Ride wrote:The manifold extensions are more or less as short as they can be in order to get the angle I want and have meat to clamp the silicone reducer, they are roughly 2" long. I've also trimmed back the silicone reducers a bit as well.

I'm currently just working on the throttle linkage. I also rerouted the upper heater core hose down behind the brake booster, it no longer interferes with the ITBs.

he was talking about diameter

I totally mis-read that. I had a long day in the garage yesterday swapping out an old rusty gas tank... must have sniffed a bit too much gas fumes

I kept the runner extensions and silicone couplers as short as possible so that I'd have room to fit the bike's OE v-stacks and clear the strut brace until I can come up with a nice solution for a curved v-stack like I mentioned in the first post.

The diameter of the runner extension is as small as it can be (using readily available aluminium tube) with out being smaller than the existing runner.

I know it's been a while since I've posted any updates, that's because there hasn't been many...

I was able to squeeze a hose behind the booster, it involved cutting the hard line from the heatercore back a bit. There's not much for the hose clamp to squeeze on, but it hasn't been leaking so it should be good...



I also figured out that the throttle cables will roughly reach where the bracket for the throttle body cable screws on, so I'll be able to modify that bracket to hold onto the throttle and cruise cables....



I'm still in the process of designing the mechanism I'm going to use to join the cables.

And finally, the manifold has been fully welded...

Good to see you over here

looks nice

Awesome work! Looks very professional!

What's the progression like off idle?

I've done a fair few sets of ITBs for various engines and experimented a little with throttle progressions.

If you rig the cable up to a bike throttle directly, the car feels razor responsive at low engine speeds, then almost feels like it slows down when you floor the throttle.

Progressive linkages are well worth the effort in my opinion

Holy Sh1t!!!!!!

You're back????

Turbo-Brown wrote:Awesome work! Looks very professional!

What's the progression like off idle?

I've done a fair few sets of ITBs for various engines and experimented a little with throttle progressions.

If you rig the cable up to a bike throttle directly, the car feels razor responsive at low engine speeds, then almost feels like it slows down when you floor the throttle.

Progressive linkages are well worth the effort in my opinion

Turbo-Brown wrote:Awesome work! Looks very professional!

What's the progression like off idle?

I've done a fair few sets of ITBs for various engines and experimented a little with throttle progressions.

If you rig the cable up to a bike throttle directly, the car feels razor responsive at low engine speeds, then almost feels like it slows down when you floor the throttle.

Progressive linkages are well worth the effort in my opinion

The kit isn't quite finished yet I've been busy with some other things lately, some of which include a home made skid plate...

[/img]


As well as pulling apart, cleaning, and reassembling my coilovers...



However I've got a couple pieces together to start working on the throttle linkage, so I might get back into it next week. My plan is to build a housing that will hold the factory progressive linkage attached to a custom turned pulley to hook a cable to. I’ll measure how much cable pull is required to open the bike throttles fully then calculate what the radius of the pulley needs to be to achieve that travel with an arc length that corresponds to the amount of rotation the factory throttle linkage has. That way the amount of pedal travel should remain the same. Also that way I can sync up the throttles and open them all equally using a single idle screw on the factory linkage.

Dayum, another beautiful project.
Those look so pretty. Now wrap it up cause I want more! More, I say!

Looks great.! We need a video...!!!

mcbonio wrote:Looks great.! We need a video...!!!

They aren't quite done yet.

And I still need to get to the dyno to do a baseline before I swap over.

Unfortunately I've got too many other things on the go currently. It's been hard to find any time to work on this project.

I realize that I haven’t updated this in a while, but that’s only because there’s been nothing up update on unfortunately. Fortunately however, I am hoping to machine a couple of the bits I need to mock up my throttle linkage after work this evening.

I figured that in the meantime I might post some pictures of what I’m planning on building. My idea is to use the linkage off of the stock throttle body in hopes that the pedal travel and throttle progression will remain the same in addition to retaining cruise control functionality. My plan is to use the holes in the valve cover to mount a piece of angle iron and to that piece of angle iron I’m going to weld some laser cut pieces of 3/16”a steel.



The one side of the bracket is slotted and has a tab with two holes where the two throttle cables adjusters will mount. The slot is so I can set the height of the tab, once it’s set I’ll fill the slot with weld and trim any excess off the top. Then you can see the cable joiner to combine the two cables into one. I’m going to weld a shoulder bolt to the actuating linkage from the throttle body and attach my cable actuating lever to that.

Those with a keen eye will see that it’s not actuating through the axis that the stock throttle plate does, but the other axis of the linkage. The reason for this is that the throttle plate axis needs to rotate through 90 degrees in order to get full pedal travel and having the actuating lever attached to that axis adds complications to the motion of the actuating lever and clevis. Due to the geometry of the throttle linkage, the other axis only rotates about 45 degrees through full pedal travel which should be sufficient in order to get enough cable travel to fully open the bike throttle bodies.



Here you can see the actuating lever which is a lasercut piece welded to a collar clamp. The collar clamp is to help fine tune the cable positions when setting up the throttle bodies. Once everything is set, I’ll likely drill through the collar clamp and shoulder bolt and insert a spring pin to lock the orientation. That way I won’t have to worry about the collar clamp vibrating loose and slipping. The actuating lever has a few holes in it for the clevis for fine tuning the amount of cable travel.



p.s. I'm using thumbnail pictures to try and stretch out my bandwith for longer that it's been lasting the last couple months

I took a few minutes yesterday to tack together the main part of the throttle assembly so I could test fit it on the motor with injectors, fuel rail and injector harness. Everything appears to be clear...

Bullit: how did you find out what the right distance is between valve and butterfly?
im searching like hell to find the right info.

greetz

Steven

Any updates dude??

steve_k wrote:Any updates dude??

Not yet.... it's too cold in my garage right now lol

I will be finishing up this project for the spring time though.

Bullet_Ride wrote:

steve_k wrote:Any updates dude??

Not yet.... it's too cold in my garage right now lol

I will be finishing up this project for the spring time though.

Good good

I'm watching this one with interest & getting a parts list together as I go

Oh snap...

[youtube][/youtube]

I'll do some more write up with pictures when I get a chance.