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I'm pretty sure the throttle plates are NOT supposed to be fully closed and that's why your idle is so low.
The screw on top of the body (which you call the "idle screw") is an air bypass and it's simply not big enough to compensate for the flow you should have but don't.
See page F1-35 of the FSM.
Now THAT is news I can use! Apparently I over looked that when going through my FSM. Mine also says something about pulling the "blind cap off of the BAC for adjustment" ...Guess I read into that a little too much.
Manual never said anything explicitly about what that little screw was really for so I completely missed that it was used to achieve a gap spec that the motor needed right off the bat.
I still think the BAC might be fudged, but I'll cross that bridge when I get there. First order of business, get that whole deal adjusted the way it should be!!! I'm excited!
Thanks, clocker and RXSpeed16 for giving me a nudge in the right direction! Everything makes a lot more sense now.
The thing that I'm not sure I'll get with the 7 is chassis rigidity and strength. The 944 was built STRONG. and since the trans is in the back, and theres a big *** torque tube that connects the engine and trans (which is why a clutch replacement is an 8 hour job) the tunnel is super tall. Probably around a foot or so. Everything is pretty beefy. Seems to me that the 7's chassis is not quite as rigid. No idea about strength.
God forbid it happens again, but my 944 ended up on its roof with me still in it. Nothing buckled or collapsed and I was able to get out with just a couple scratches. If the same can be said about the integrity of the FC I'll be pretty happy!!
the FC is a more modern car, like you say. in general its built like a tank, anyone who has ever cut one up can attest to the fact that it is BEEFY in the back. its also very very rare to actually break anything, even in racing.
the gotcha is that its also a 4 star crash rated car (same as a 200 series volvo), so the front is a little bendy, as its designed to fold in an accident.
I would disagree.
FC's have numerous well documented electrical flaws (looking at you, switchgear) and engine issues can be much worse with rotaries since you can't really refurb them...if a housing is scored, you can't bore it out, you need a new one.
I haven't a lot of experience with German cars but I've heard that parts can be rather spendy, which might tip the scales a bit in the FC's favor but I can't really say.
the German stuff isn't any different, well the 944 is an iron block, so you can machine it, but every other porsche is a $4000 set of pistons an sleeves, or for the newer ones, you just throw it away.
i guess the newer cayennes have some thing where the piston ring scrapes the coating off the cylinder wall, and since its not repairable, the $10k engine is trash.
the Germans also still haven't gotten a handle on electricity, at least the british cars are wired by people who understood electricity, and then used crappy switches. the Germans just use crappy switches and then the wiring is a mess too.
if you want a for instance, my dad has a 2003 boxster, and the dealership spent a summer trying to get the starter motor to work with the key.
Mazda's parts prices are always crazy though, and they never seem to follow supply and demand either. that being said go to pelican parts and price out a 911 engine if you want sticker shock.
the gotcha is that its also a 4 star crash rated car (same as a 200 series volvo), so the front is a little bendy, as its designed to fold in an accident.
Thats what made me wonder... Put the car up on jack stands a little while back and noticed the front was a little flex-y. Seemed like the doors were a millimeter or so off and didn't close as well...haha. Never had anything like that happen with the 944, but you're right, more modern car, more modern structural integrity. Very cool! I don't plan to cut mine up, but I'll take your word for it!
Originally Posted by j9fd3s
the German stuff isn't any different, well the 944 is an iron block, so you can machine it, but every other porsche is a $4000 set of pistons an sleeves, or for the newer ones, you just throw it away.
They're actually aluminum blocks. You can bore out about 0.8 millimeters or so and get pistons to match but it gets expensive quick.
I have a situation with that back home. My big bore block has some light scoring from its past life. It'd be great if the pistons I have from a 968 happened to be of a tolerance group thats half a mil out, but I doubt they will be. ~$900 for a set I can fit after machining.
Pistons are over rated anyway... I'm enjoying every second spent in the rotary world.
the Germans also still haven't gotten a handle on electricity, at least the british cars are wired by people who understood electricity, and then used crappy switches. the Germans just use crappy switches and then the wiring is a mess too.
Amen to that! Seen it...
Mazda's parts prices are always crazy though, and they never seem to follow supply and demand either. that being said go to pelican parts and price out a 911 engine if you want sticker shock.
I'd argue that Mazda's stuff is still pretty reasonably priced. With Porsche stuff it gets even worse in the second hand market. People seem to think anything with the emblem on it is practically cast out of pure gold.
Add to all that the amount of time it takes to complete a job on either car. For a kick, look up how you lower/upgrade the suspension in the rear of a 944. Look up a clutch replacement too. Its almost comical.
Good to see you over here j9fd3s! A large majority of my rotary knowledge comes from you and your thoughtful replies to other people's questions! Granted, I've got a ways to go with the rotary learning curve, so check up over here every so often!
I now have a good handle on this "throttle body mod". Mine indeed has it.
Now, from what I understand, the bottom "single" butterfly is supposed to be cracked open about 8º with the leading edge having a gap of about .02"-.03".
The shop manual suggests that this should be done by manipulation of a bracket that essentially determines how taught the linkage arm is that connects primary and secondary. See here:
So, I observed said bracket, and determined that it did need a a little massaging. However, I loosened up the bolt that that held the whole deal together, and was able to move and bend the bracket ever so slightly enough to establish an acceptable gap for the secondary. Ended up looking like this:
From there, I found you can fine tune the openness of either by taking advantage of linkage slop. Theres an adjuster screw that adjusts at the lower throttle blade, and one that adjust at the upper blade. Seen here:
And here:
From there it was just a matter of fine tuning so that the car was happy with its idle, and the TPS was properly adjusted.
One thing I've found weird with the TPS, is that it seems like the wide range is consistently not getting pushed in far enough by its lobe. I'll get the narrow range right down to its lowest end of tolerance at .8K Ohms, but the wide range would always be higher than its highest end of the tolerance at >.9K Ohms. It was possible to shim the wide range with a notecard thickness of paper and get it down to where it should be, but I'm not sure it matters that much. Seemed happy with and without it.
Anyway, idle seems happy now. Right around ~800RPM or so. I'll play with some fine tuning over the next day or two but for now I'm calling it case closed. I'll unhook the battery and run the fault codes again to make sure the computer is happy with everything I've done.
if you mess with the tb and remove emissions the idle is always going to be a little bit funky but it should never stall nor cause any cel's
So I've found... Definitely wish it was all still there, but you take what you can get. As long as it isn't throwing any TPS codes, I'll just settle for the funky idle.
Figured I'd throw up a quick update seeing as its been a couple months...
Not much has been going on, basically just been strategically purchasing parts as my bank account re-charges.
My pile as of right now looks as so:
Basically everything I need to do the clutch/short shifter, plus some random tune up stuff and the start of my brake system overhaul.
Speaking of that, I decided to spring for some EBC "Yellowstuff" pads. Just ordered the rears for now in order to get free shipping on my Summit Racing order Rest of that stuff should be coming in a month or so.
Idle/running issues have been completely resolved. Tested the TPS with an Oscilloscope and it looked good. Got everything adjusted properly and the old girl is running like a top!
Suspension stuff is getting planned out. I'm suspecting I have a bad rear wheel bearing which kind of sucks... If that is the case, I may actually pick up an entire rear suspension and hope it has at least one good bearing. Currently have a lead on at least one full set up. This would also be helpful for fabricating all the spherical bearings and heim joints I want in order to get a good range of adjustments back there.
I'd like to get the clutch done this weekend, but I'm anticipating some minor snags when it comes time to procure a work bay for that. Once thats all buttoned up, I have some minor fabrication work in order to get the short shifter to work that I ordered.
Other than that, this thread will probably end up being quiet for another couple months. Once I have the funds to make suspension upgrades happen things should get interesting.
What I found when I opened it all up was about what I had suspected before. The car had a pretty spent 4 puck (probably ceramic?) clutch disc.
The friction material was about down to the rivets. Pilot and throwout where old for sure.
I threw in a stock clutch since it was cheap, and now whatever nasty squealing noise was going on is gone. I'll see how it feels. Later on I may consider a light weight flywheel and a slightly more grabby clutch disc. Time shall tell.
Also inspected my supposed "bad wheel bearing". Found that both rear wheels had the same wobble. I also found that both outside "toe link" ends were way loose. I'm thinking that it isn't the bearings at this point. Those type of rear wheel bearings don't really go bad, let alone both of them. Those toe links are probably spent. I've been planning to make adjustable ones anyway so that will happen eventually.
Seriously considering getting the Konis on the car rebuilt. Given my budget, I just don't think I can buy coil overs in the $1-1.2K range that will compete with with Koni single adjustables and a good set of springs. Height adjustability is nice...but the Japanese marketing machine coil overs just aren't doin it for me.
And the start of the the segment, that from here on out, I shall call "WTF, PO?!?" moments.
Today's "WTF, PO?!?" moment is brought to you by... *drum roll, please*
Aluminum pie pans!!!
Because somehow, somewhere (perhaps in a PO's head), in some twisted way, this was thought to be an acceptable substitute for an inner shift boot...
What was underneath really didn't surprise me either...
So, anyway, ALL the boots were replaced, and while I was in there I retrofitted an NA Miata short shifter that I found on Ebay for $45. I was in a hurry and didn't do a lot of documentation, but the procedure I used to make it all work can be found here: Triple-R: FC3S Buildup - Chapter 3: Part 24
I'll add that when you're doing this swap, when you pull apart the stock shifter, the bushing underneath the big ball is a shorter busing than the one up top. After reading over a few threads where this has been done, I can verify that this shifter works best when a taller "top" bushing is used both on top and bottom. I also omitted the pin, and plastic journal bushing from the big ball. Its only use is to keep the shift lever from rotating so you can tighten a **** on. It does absolutely nothing for slop/shifter feel. I'll be putting a **** on that doesn't have the gate printed on it, so I don't really care about this. Any **** tightening can simply be done by hand, holding the lever in place.
Anyway, it feels pretty decent. Decreased shifter throw probably somewhere between 45%-60%. Advertised as a 40% decrease on the Miatas, and they have a shorter stock throw than the stock throw on our 7's, so that should give anyone who's interested an idea.
Overall it turned out great! This is with the second of two pieces removed for installation of the boots. More pics later once I have a different ****:
Its been a while since I've updated this whole deal. A few things have been going on the last couple months.
I'll start this with a "WTF, PO?!?" moment!
Today's moment is brought to you by the phrase "measure once, cut twice", and is being co-sponsored by the phenomenon of cut springs!
Pulled the shitty cut springs out of the rear. This one looks like it got half way cut in one spot and then said PO realized he needed to cut it one coil up. That coil collapsed, rusted and eventually cracked at the first (wrong) cut. Check it out:
Out with the old, in with the new! Tanabe GF210 1.5" drop springs in the rear:
Those rear Koni's look like hell, but I actually found that they weren't as blown as I thought. In fact, they work quite well! I think one of these weekends I'll hit 'em with a wire wheel and some school bus yellow.
I wish I could say the same about the fronts... Went to put the front springs in, happened to pull the passenger strut out first, and this is what I found:
That don't look right! Needless to say that one is trash. Didn't even bother pulling the other side, and also didn't bother putting the new springs in since the ride will suck no matter what, and I'll have to pull it all apart again soon anyway.
Side note on the Koni's: I'm hearing that Porsche 914 rear shocks will basically work for an FC application. When I'm home in June, I'm going to pull the Koni inserts out of the struts from my 944 and see if they might be able to fit an FC strut. That may be a good alternative.
A buddy of mine out here hooked me up with a bunch of random 205/55r16 tires, so I went ahead and got some mounted on my mesh wheels. As some may know, a spacer if required to clear the front brakes when using Speedline/Crown Vic wheels. This requires longer wheel studs. I learned that late model Camaros use the same thread and knurl size as the FC. How handy! Got some ARP 12x1.5 .509" knurl extended studs off summit for about $15 a set. You get about half an inch more stud than whats stock on the front of the FC. Went in like a breeze! Pictured with a 7mm spacer:
The last order of business was to fix an issue I had with the passenger rear lateral link. The nut on one of the ends backed out, then corroded in place with rust just before it fell off. This caused the passenger rear wheel to have about an inch of nasty fore and aft movement kind of depending on whether I was accelerating, braking, turning, etc... It felt like ****, and was quite unsafe. Pic below. Threw a new link in yesterday, and now all is well! BTW, thats all PB blaster you see on the arm:
Now that all the above is done, the old girl is looking half decent! Check it out:
Far from perfect, but at least its safe to drive now and looks half decent. I'm entering another period financial limbo, so it will probably be a while till the next update. Peace.
I got bored today and decided to go rent a compression tester. Grabbed a buddy and we went through the process, which went as follows:
-All plug wires removed
-Leading plugs removed
-EGI fuse pulled
-Removed shrader valve from the engine end of the tester (this way it doesn't hold compression which allows viewing of each individual rotor face's compression)
-Ran both rotors like this
-Re-installed shrader valve to get an overall compression reading for each rotor
I'm not 100% sure how to interpret these results. If you didn't watch the video, each face of both rotors made about 50-52 PSI. The over all was about the same, but I expected that to be a lot higher (I've heard you should look for over 100 PSI). I'm not sure if this is a fault of the tester, or if my motor just has low compression across the board. I also heard that 30-40 PSI for each rotor face is quite good.
Edit: My FSM indicates 21 PSI for individual chambers and 85 PSI for the whole rotor. Now I'm even more confused!
Of course I'm not doing this with the special Mazda tool, so I'm not sure what I should be looking for. I am, however, quite happy that there is uniform compression on each face +/- 2 PSI. This means that if the numbers I've found are decent, this is a pretty healthy motor.
Would anyone following this thread care to comment? If so, please do!
Last edited by autobahn_don; 06-14-16 at 02:30 PM.
Alright, did some research on what I should be seeing from a compression test done the way I did mine.
My numbers are WAAAY low. What I noticed though, is that when I do an "overall" test on each rotor, I'm not getting anything different from what the individual rotor faces yielded.
I realize now that the 21 PSI I mentioned in my post above is likely the max variance between rotors (or even faces?)
I have no doubt that this engine could indeed be junk, but I'm going to test again with a known good tester just to make sure. The one I used was rented and may not have been working properly.
All that said, there is also no evidence of this motor having extremely low compression in the way that it runs. Hot starts are not an issue, it pulls hard, etc. Something just doesn't seem right...
Kind of looks like rotor one has an apex seal thats starting to get tired, but I slowed the video way down and it would appear that all the faces are still within ~10 PSI of each other, and thats if my phone's shutter speed was quick enough to pick up what was actually happening. When I was looking at the gauge real time with my own eyes this afternoon, the needle bounces look pretty even.
I'd say this motor is getting a little fatigued, but has some life left in her!
Still in financial limbo, future updates will be out a ways.
You're only looking for evenness on the bounce test. If you are holding the button or have taken the valve out it's not going to read actual compression. So optimistically, at least 1 rotor face has about 100psi and the others are close. The throttle should also be fully opened during the compression test.
12-18-15, 07:17 PM
Rest of that stuff should be coming in a month or so.
