1994 RX-7: Xcessive LIM & Fuel Rail install (in progress)

[scotty305]

Finally finished installing an Xcessive Manufacturing Lower Intake Manifold (formerly marketed under the "Ground Zero" badge) , Xcessive 4-injector fuel rail, 4x 1000cc Yawpower/Injector Dynamics injectors, and a few supporting mods on my otherwise stock engine. The install took longer than expected, this thread was originally created as a checklist of what still needed to be done.


History:
Bought the car in January 2004, it was bone stock with 45,000 miles. It has seen a couple years of occasional autocrossing, some daily-driving when my other car was down, quite a few trips up and down the local mountain roads. It's now at 87,000 miles and the coolant seals are on their way out. I've had an AEM EMS and wideband installed for a little over a year now, managed to learn a bit about EFI tuning without hurting the motor so that's been fun. Before I tear the engine apart for a rebuild, I've decided to upgrade my manifold and fuel system; I'd prefer to test new things on the old motor in case anything goes wrong. As of now the car has been down for a few months and I'm hoping to have it back on the road before January (edit: finished in August!).

This project was largely inspired by Dan Chadwick's build:
http://www.rotarycarclub.com/rotary_...read.php?t=243


Parts Sources:
Xcessive Manufacturing - LIM & Fuel Rail www.xcessivemanufacturing.com
Yawpower Injectors www.yawpower.com , purchased from local vendor www.apexspeedtech.com
AEM - Honda-style Fuel Pressure Regulator www.aempower.com , purchased from local vendor/tuner MP Tuning www.MPtuning.net
misc. metric bolts, vacuum plugs, clamps - King Bolt located on Grand Ave in Covina, CA (no website)


"Done" List (complete):
Remove UIM, rats nest, OEM fuel rails, twin turbo assembly
Fabricate & install blockoff plates for UIM: AWS
Remove coolant lines to throttle body, fast idle warmup cam
Modify OEM turbos: hammer heat shield closer to turbos for increased clearance
Modify OEM turbos: bend coolant return line (photo below shows coolant line before bending)


Modify LIM: remove material from rear runner to allow clearance for secondary turbocharger



Modify LIM: remove material from front-upper mounting point to allow clearance for turbo oil feed pipe (note the new angle of the turbo coolant line)



Modify OEM UIM bracket (supports front of UIM near throttle body). The OEM LIM is angled toward the rear of the engine bay, while the runners on the XS LIM go straight up. This moves the UIM forward by about an inch. Among other things, the bracket pictured below needs to be modified. You can see that the notch no longer lines up with the mounting point on the UIM.


After taking the photo above, I made a vertical mark (using a Sharpie) where the bracket should be bent to meet the UIM. This bracket is part of the solenoid rack, which I disassembled. I clamped the bracket in a vise and used the vise to straighten out the top bend. Then I used a bending brake to bend the bracket at the mark that I had made. The mounting notch needs to be extended down; straightening the bracket and changing the bend location makes it a bit taller. Modified bracket shown below:





Test fit LIM & fuel rail

Modify OEM solenoid rack (remove all hard lines). Removing the rats nest of hard lines was easier than I thought, all you need to do is remove those awful phillips screws. PB Blaster helps, although I had to slot some of the screws and remove them with a big flathead driver.


Add FPR flange to Xcessive Fuel Rail
I built a couple of mockup brackets to mount the a universal-style Fuel Pressure Regulator with AN inlet and outlet ports, but after purchasing some AN fittings it became apparent my original idea wasn't going to work due to the size and packaging constraints introduced by the fittings. In the end, I switched to an AEM adjustable FPR that uses a flange and an o-ring and is designed mount directly to an OEM Honda fuel rail. After taking a close look at a Honda fuel rail, it's just a flat flange with a hole for the fuel and two threaded holes for mounting screws. Luckily I have a co-worker who can weld aluminum so I fabricated a simple flange and had it welded to the XS fuel rail. Doing this eliminated quite a few potential leaks: my original plan used six fittings and a short section of AN-6 fuel line to accomplish the same task. Be careful if you attempt this... the XS fuel rail mounts are not symmetrical and I put the mounting flange on the wrong side of the fuel rail on my first attempt (luckily it was only tacked on for the test-fit, see photo in post below).


The XS fuel rail originally included a metric threaded bung for installing the OEM fuel temp sensor. I opted to cut this off and tap the remaining hole for a 1/8" NPT fuel pressure sensor. Luckily the hole was already the correct diameter.




Heat and bend OEM oil filler neck:
Used a heat gun to warm the plastic until pliable, then installed the UIM and throttle body while holding the filler neck forward. Stuffed an old t-shirt between them to create a reasonable gap, then allowed the setup to cool. Repeated this process a few times until the gap was satisfactory. Bent the plastic nipple for the PCV valve forward using a hex key when it was warm.




Modify OEM y-pipe:
The front runner on the new LIM interferes with the location of the factory Y-pipe. Chadwick rotated his primary turbo compressor housing, tilting the y-pipe away from the LIM for more clearance. I've never rotated a compressor housing and was afraid to damage my stock twins in the learning process. Instead I trimmed some material from the y-pipe, changing the angle of the mounting flange and removing a little bit of the lip near where the rubber coupler mounts. I also switched to a thinner rubber coupler to allow for a little more clearance (the old coupler was hard as plastic, I doubt it was making a good seal).



Bend or replace OEM hard pipes that mount to primary turbocharger:
Since the turbo oil and coolant lines needed to be bent, the OEM hard pipes for the turbo control, wastegate control, and prespool needed to be bent a little to clear them. They also needed to be bent to clear the fittings on the front of the XS fuel rail.




Got started on the solenoid locations and vacuum line routing. I'm not going to re-use any of the original "rats nest" hard lines since most of them would be unused or blocked off; purchased some high-temp plastic tee's from McMaster-Carr. I also built a couple of brackets to mount the wastegate and prespool solenoids on the solenoid rack (the XS fuel rail interferes with mounting them in the OEM location).





Install new wires for injectors, add fuel pressure sensor, re-wrap most of engine harness:
Turns out the injectors use a separate power wire that isn't shared with anything else in the harness so this was easier than I thought. The white wire going to the blue connector (top-right of photo) is the wire used for the injector power, the pin is the same one that is used for the injector pins on the ECU connector. While the harness was out of the car I removed a few unused connectors and added a connector for the fuel pressure sensor. I also moved a few wires at the ECU connector to match the changes I made to solenoid locations. For instance, I moved the Turbo Control solenoids to different locations on the solenoid rack because this made the vacuum routing easier. This required them to use different plugs than the original factory wiring harness, so I moved the wires for those plugs to different pins on the ECU connector. So now even though the Charge Relief solenoid has been moved to a different location (and now uses a different plug) it is still controlled by the same pin on the ECU.


Plug OEM primary injector holes:
Called Racing Beat and asked if their injector plug kit for the older 13B engines will fit the 13B-REW. The plugs needed to be cut about 1" shorter but after cutting they fit well (see photo above). I've got exact measurements if anyone is interested.


Modify Fuel Rail flange, shorten bracket height:
Previous setup leaked when tested under pressure. Fuel injectors didn't seem secure enough with the Xcessive bracket height and the Yawpower spacers.




"To Do" List (incomplete):
Clean up new fuel line routing & lengths (current setup works but could use clamps and brackets to further ensure the lines don't rub).
Clean up vacuum vacuum lines, permanently plug unused nipples on UIM



More photos and updates to follow... thanks for reading.

[neit_jnf]

very interested in seeing the modifications made to make the new LIM work with the twins! thats something i want to do in the future.

[Chadwick]

Glad my write up helped you along, looks like a nice install. Is the blue tape on the third picture marking where you need to notch for the y-pipe? Don't forget that you have to clock the turbo and adjust the rod.

Dan

[scotty305]

Yes the blue tape is approximately where the Y-pipe is contacting the manifold. I'm hoping I can get away without notching the manifold. Another thing I've considered is fabricating a new front part of the y-pipe, "afgmoto1978" posted a couple of nice photos on rx7club a while back.

[proz07]

i have a question i also have x-lim and rail. im wondering why your going this route running the stock twins? if its just for piece of mind for the airflow or future single being your not going to be using the primaries anymore? i would also like to hear of the off idle low rpm response difference moving the injectors up in the air stream once you get it running?

z

[scotty305]

Good questions, proz07.
This whole project started in July when I decided I wanted to block the rear coolant line and bypass the fast idle cam on the throttle body. As I dug deeper in the engine bay I saw first-hand how many comprimises Mazda designed into the OEM lower manifold. I was not impressed with how the runners dodged the ACV and EGR passages... who knows what that does to airflow but it can't be good and I'd rather not find out the hard way. Still need to block that rear coolant line, fast idle cam is done though.





Things sort of snowballed from there. I didn't originally plan on making any other changes but then I decided I wasn't too impressed with the OEM fuel rails and plumbing. Main reason to upgrade now is because I'm afraid that if I were to use the OEM secondary fuel rail I'd have to plug the two additional injector holes in the XS LIM and wouldn't be able to un-plug them in the future.


The primary injectors are only moving a few inches upstream, I don't anticipate major problems from moving them. I'm not saying the distance won't be noticeable, but you can adjust the injector phasing in the EMS (not just the pulsewidth but also when the injectors are opened... similar to the difference between coil dwell and ignition timing). I've heard that other people had funny idling and throttle response complaints but I suspect this may have been due to improper injector phasing... either the ECU couldn't adjust it or the tuner might not have been aware that it could make a difference. According to some people there are potential fuel economy and power gains to be had by moving the injectors further upstream due to improved atomization, unfortunately I'm making so many other changes this might be difficult to quantify. I'll definitely post the results here, even if they're bad.


I'm not sure if I'll want much more power than the stock twins are capable of, but I'm hoping this fuel system will be capable of supporting whatever I decide to do in the next few years.

[neit_jnf]

updates?

and where will you be getting all the vaccuum/boost sources that the new mani doesn't have?

[scotty305]

I haven't made much progress lately... past few weeks got busy at work, plus Christmas and New Years and family stuff. I purchased some AN fittings but they are larger than I realized, my fittings aren't fitting. My revised fuel setup will include an aftermarket FPR designed for a Honda setup which mounts directly to the fuel rail using a flange with an o-ring. Mounting the regulator to the fuel rail will eliminate 5 fittings and adapters compared to my original plan (NPT-to-AN male, AN-female to push-on hose, push-on hose to AN female, AN male to AN male). I'm hoping to finish that within the next week or so.


The OEM lower manifold includes four vacuum pass-throughs (near the top)... I'm removing one of those lines (EGR) and planning to route the other three (used with the Charge Control and Charge Relief valves) around the rear of the manifold near the firewall.

The vacuum line near the front secondary intake runner supplies air for the primary injectors, that passage is not retained with the XS LIM so the vacuum line will not be necessary.

The other vacuum line is just manifold pressure, the diagram isn't clear but I think it is used for the OEM fuel pressure regulator. After eliminating the AWS, ACV and EGR solenoids there will be at least one unused port on the UIM near the throttle body... one of those ports will feed vacuum/boost directly to the FPR (the OEM Fuel Pressure Control solenoid will be eliminated).

[scotty305]

Update: purchased Honda-style FPR, mounting flange nearly completed.

Did some more research on the OEM solenoid vacuum lines, ECU pins and control logic. I've always wondered why most (but not all) of the solenoids are OFF at low RPM and ON after the secondary transition. The only exception is the Charge Control solenoid, it is controlled exactly opposite of all the others... ON at low RPM and OFF after the secondary transition. It turns out the vacuum lines for the Charge Control solenoid are plumbed backwards compared to the other solenoids... see diagram below:






I want the ECU to operate the Charge Control Solenoid the same way the others are activated, (off then on) this will allow me to experiment with controlling the sequential switchover point based on a combination of TPS, MAP, RPM or even VSS rather than simply RPM-based control. In order to do that, the vacuum and pressure lines going to the Charge Control solenoid will need to be swapped. The plan is to install the solenoids and vacuum lines as shown below, this should leave room to mount the Prespool and Wastegate solenoids on the bottom row of the solenoid rack (the top-feed fuel rail is going to prevent them from being installed in their original location).







Update 01-31-2009: finished mounting flange, tacked it to fuel rail for test fit. Fits the FPR well but I put it on the wrong side of the fuel rail... turns out the fuel rail mounts aren't symmetrical. Good thing it wasn't fully welded on.

[albertomg]

Hmmm..... Seems like a lot of work to make work with twins. If equal distribution of air is the goal, wouldn't it potentially be easier and cheaper to send the stock LIM out to be flowed and ported?

Also, when you are grinding out material for clearancing, how do you take the expansion of the metal into account? Does it require 1mm, 2mm or whatever space to take that into account?

Thanks for the input and good luck with your project.

[scotty305]

Yes it is definitely more work than I realized from reading Dan Chadwick's thread. I suspect I would have been finished months ago if I had decided to stick with the stock fuel system and plug the holes in the XS LIM. He mentioned that he needed to add about 20% fuel to a previously tuned map after installing the XS LIM and performing some minor port work on his most recent engine build... I'd be pretty happy if I picked up an additional 5-10% power compared to the stock LIM... that would be 10-20whp which isn't too bad.

Good point regarding thermal expansion... I'll have to ask some Mechanical Engineer friends of mine to give a ball-park estimate of how much the turbos and manifold might grow when they get hot. I suspect the answer will be less than 2mm. I had some aluminum injector spacers fabricated and the outer diameter was about 0.001" larger than the hole that they needed to slide into, and someone suggested that I freeze the spacers and heat the manifold because that might make the cold parts shrink and the warm parts expand enough for everything to fit. I was skeptical so I borrowed a set of calipers to see the results of thermal expansion. After putting the spacers in the freezer they shrinking by almost 0.001," using a heat gun to heat the manifold so hot you couldn't touch it resulted in the injector holes expanding less than 0.001" (maybe 0.0005" larger). The result still didn't fit. When I purchased my XS fuel rail I asked them what they recommended for installing top-feed injectors in their LIM. They sent four rubber spacers which are apparently OEM parts used for the injectors in the FC3S. They actually said that the injector holes in the XS LIM are slightly smaller than the OEM FD3S LIM because they wanted a tighter fit with these rubber FC3S injector spacers. The fit is great, they are the thick black spacers in the photo below, I will use them instead of the green lower o-rings that were supplied with the Yawpower injectors.





I also decided I'd like to re-clock the vacuum port on the AEM FPR so it points toward one of the vacuum ports on the rear of the stock UIM. The top half of the assembly can be removed and rotated, as explained in their instructions:

[neit_jnf]

wait, so that means stock secondary rail wont fit because the holes are smaller?

[scotty305]

Rich from Xcessive told me the holes are slightly smaller (maybe a couple thousandths, I don't remember). It shouldn't be a big deal if you're working with rubber, and it wasn't much of a problem with aluminum either... some 1000-grit sandpaper and a couple hours of sanding on the hardwood floor while watching TV and they fit fine. By the way, I had the aluminum spacers machined by a friend and I asked him to make them slightly large, they didn't quite fit the stock manifold either but it's easier to remove some material than add more.

My main concern with the aluminum spacers was there wasn't a lot of seating area for the green o-rings... when I mentioned this to Rich from Xcessive he suggested the rubber FC3S spacers for use with top-feed injectors, apparently they're only a couple of bucks each.

The stock secondary rail should fit just fine with the XS LIM, quite a few people have done that and apparently you need to trim about 1/4" of material from either the stock fuel rail or the front runner on the XS LIM. I put one of the plastic secondary injector diffusers in the hole, it fit fine.

[hwnd]

Scott is rich, look at his leather couch!

I've got 100% faith in ya, doing it once, doing it right.. ;-)

[scotty305]

Haha, wish I was rich... the car would be back on the road already. Scored the couch for free when a friend upgraded to a new couch (it has some cat scratches). Need to find some tough snap ring pliers to clock the primary compressor housing... Chadwick made this stuff sound easy, that's how I know he's got some skills and experience in addition to a nice set of tools.