Author Topic: Murz' 1986 Arctic Silver GXL aka Silver  (Read 46763 times)

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Offline toplessFC3Sman

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Re: 1986 GXL engine rebuild
« Reply #60 on: October 06, 2014, 08:21:29 PM »
Sorry, I guess I wasn't clear - the fuel cut defender (FCD) won't prevent boost creep, it will just keep it from being catastrophic.  With a free-flowing exhaust, the turbo has less backpressure on it, so the turbine makes more power and thus can compress more intake air to a higher pressure.  Normally, you could open the wastegate further to bypass the turbine, but the stock S4 & S5 internal wastegates aren't big enough even when fully open to bypass enough exhaust gas around the turbine, so you get boost creep.  This wouldn't be so bad, except that when the boost gets above a pre-set limit (6 psi for S4's, maybe 9-10 psi for S5's IIRC), the stock ECU cuts fuel, which can cause a lean condition and lead to detonation, killing the engine.

All the FCD does is prevent the ECU from actually seeing the correct boost pressure, so it never detects the pressure that would cause fuel-cut.  Effectively, the FCD passes through the manifold pressure signal unchanged up to atmospheric pressure, and then starts scaling it once you're boosting. Since the actual fueling rate is based on the AFM, which detects the extra air flow that goes with the additional boost, you get enough fuel delivered by the injectors, BUT the spark correction, which is also based on the boost as well as air flow, can get too aggressive if you push the boost beyond a few PSI over stock.  Even so, I'd run 93 octane exclusively for the extra knock protection since the spark will be slightly advanced when boosting.

With that being said... $130 for one?! Holy crap, its a couple of resistors and connectors!  I used to have one, let me dig around & see if I can find it for you.

Also, DO NOT use the S5 NA AFM - it will be rich at low to mid loads, right up to the point where the turbo maxes out it's flow capacity and then you go lean, popping the engine!  For example (and i'm sure the numbers are wildly inaccurate), say the S5 NA flows 100 cubic ft of air/minute (CFM).  The ECU will want to see that whole range from 0 - 100 CFM over it's voltage scale of 0-5V, so the S5 NA AFM will show 0V at 0 CFM, and 5V at 100 CFM, at which point it is max-ed out and can't read any higher.  Now, if the S5 Turbo flows 150 CFM, then the S5 Turbo AFM will have 0V at 0 CFM but 5V at 150 CFM.  If the S5 turbo ECU is expecting to convert 5V into 150 CFM, but it's hooked up to an S5 NA ECU telling it 5V (which is actually 100 CFM), the ECU will deliver 50% more fuel than is necessary, making the engine run rich.  The dangerous part comes when the engine actually flows more air than the NA AFM can measure - at that point it just keeps reporting it's maximum airflow and the ECU doesn't add any more fuel or pull any more timing, and the engine runs lean & goes "POP".  This is a pretty simplified explanation, leaving out all the correction curves that convert between CFM and voltage, temperature correction etc, but you get the picture...

There is a bit of a difference between S4 & S5 alternator wiring, but IIRC it amounts to running 1 extra wire.  I've swapped the larger output S6 alternator into my S4 'vert, and it just needed a voltage signal wire from the fuse box next to the battery.

One thing to be cautious of with S5's is the electronically controlled OMP - if it works well, then great, but they seem to be a bit of a failure point vs. the S4's mechanical OMP.  Then again, when the S4's OMP fails, you don't necessarily see it as an OMP failure, you see it as an engine failure...

Offline murz

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Re: 1986 GXL engine rebuild
« Reply #61 on: October 07, 2014, 08:17:05 AM »
Makes complete sense now, thank you. So now my question is this, if I just port out the waste gate would that fix the issue? But I guess either way I'd need the FCD if I want to run higher than stock boost. I'm not sure how much boost is even needed to get around 250hp, but I've read that the stock turbo maxes out at 12 PSI, would a boost controller be needed to attain that level? Right now the only mods I can think of doing is just full RB exhaust, FCD, and Megasquirt eventually. I will be upgrading the fuel pump to the one you guys mentioned, the Walbro 255. Will I need a fuel pressure regulator? Yeah, I agree $130 for such a simple device is a rip off, if you could find the FCD that would awesome, thank you!

Now I understand how AFMs work, yeah crisis averted, thanks for that well put explanation.

So, I want to go premix, I just figure it to be much safer and efficient. But the S5 MOP, when removed throws an error code and puts the car into limp mode... I'll have to find a way around this.

Hmmm, so JDM engines don't come with crank angle sensors I read somewhere. Wondering if an NA S5 CAS would just drop in. I'd think so...
1986 AS GXL Turbo swapped
1993 VR R1

Offline toplessFC3Sman

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Re: 1986 GXL engine rebuild
« Reply #62 on: October 07, 2014, 10:20:15 AM »
The stock turbo can't push more than about 10-12 psi, and even then, 12 psi doesn't make much more power than 10 since the backpressure starts going up pretty quickly due to the more restrictive turbine wheel.  From that point you can get into hybrid turbos like the BNR, and clipping the turbine wheel to make it less restrictive, but these mods start to trade off low-RPM responsiveness for high-RPM power.

The CAS should just drop in, and is the same for NA & turbo engines.  Some FC's (euro market primarily) had distributors there instead of the CAS, but I thought JDM engines had the CAS too.

As for the S5's OMP - you could potentially use the S5 engine with S4 electronics & premix, or just use the S5 OMP.  I like using the OMP because there's no chance of forgetting to add premix to the tank.

I don't know if an FPR is strictly necessary with the Walbro 255, but I had installed one and then put a gauge on the fuel pressure about 2 years later and realized that the fuel pressure was constant, not changing with intake pressure, so either the stock FPR was overwhelmed by the extra flow or it was broken.  Either way, it got replaced with an aeromotive FPR that's been working well and seems to have plenty of capacity, for relatively cheap.

Offline murz

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Re: 1986 GXL engine rebuild
« Reply #63 on: October 08, 2014, 12:31:10 PM »
Hmmm, i'll have to look into hybrid turbos, I'd be cool with high RPM power haha. But i get what you're saying, I also enjoy low RPM responsiveness, especially if it's going to be a street car. Well, I have two CAS so, i'm good on that. Yeah I read somewhere JDM engines don't have CAS, you're probably right, wouldn't make much sense really.

The OMP thing I'll have to put some thought into, honestly I'd rather just premix, I'll have to figure this one out. Same for the FPR.

Anyways, tried to start her up today, dead battery unfortunately, I did get her to crank and almost start, having the huge exhaust leak with headers creates the best sound ever. Second attempt the battery was too weak. Will try again tomorrow. Would like to drive her before the swap!

Bird poop on the door, she needs a wash badly. That's the downside of sitting underneath power lines.
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Throttle body mod, plus paint.
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1986 AS GXL Turbo swapped
1993 VR R1

Offline murz

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Re: 1986 GXL engine rebuild
« Reply #64 on: October 10, 2014, 02:18:13 PM »
Anyways, the issue I was having with the 86 was the idle was messed up. Well, to sum up what was happening, the thermowax and dash-pot were somehow jamming the throttle, keeping you from really doing anything. It was un-driveable, very un-driveable! So, Fidelity101 gave me the great idea of just simplifying the throttle body by removing those unnecessary plates and the thermowax and dash-pot. I did this, and didn't install it in the car until about a week ago. I also painted it!

And there she sat for another week. Yesterday I got the time and desire to try and start her. She wouldn't start, the battery died from too many attempts, so I put her on the charger and said I'd try tomorrow.

So, today I got the desire to give her a shot to shine. I also noticed the Mass Air Flow sensor was unplugged... probably why she wouldn't start the day before? Anyways, she fired right up, and idled right away too! i didn't expect that... Due to broken studs on the Pre-silencer, she has a giant exhaust leak. So she's louder than anything. I moved all three other vehicles out of the drive way and took her on the road. I feel like an idiot for not doing this previously, as she's an absolute thrill to drive! I'm glad I kept the actuators on, as the low end torque is veddy-nice-ah (compared to the Vert and how she ran previously)! The lightweight flywheel makes a ton of difference, she wants to move all the time, and does it noticeably faster! I'm keeping her below 4k for now, for break in purposes. At 4k RPMs she's too loud anyways. Also the Stage 1 Exedy clutch is very nice, another great mod I'd recommend!
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She idles at 1200 RPMs right now, I have been driving her all day and yesterday. I have the idle set kind of high for break in reasons, I adjusted the TPS correctly, and it's surging a bit when at idle, which isn't a real big issue really. So it's probably something else causing it now. She's just super loud really, I'll get around to fixing the exhaust leak next week. The electric fan switch I have broke on me while driving, so I redid it today, and replaced a few bulbs and stuff.

Everything seems to be working just fine now, you can hear the glimer belt sound on decel which sounds great. The lighter flywheel makes a big difference, better shifts and quicker accelerations, I probably could have just gone with an aluminum one really, but this one is just fine. The Stage 1 Exedy clutch kit works great with the flywheel as well, shifting is so smooth and quick now. I'd totally recommend the flywheel and stage 1 clutch kit for an NA car, I'd even go lighter too!
1986 AS GXL Turbo swapped
1993 VR R1

Offline fidelity101

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Re: 1986 GXL engine rebuild
« Reply #65 on: October 13, 2014, 05:30:52 AM »
surging idle leads me to think bad BAC.

Offline murz

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Re: 1986 GXL engine rebuild
« Reply #66 on: October 13, 2014, 05:20:09 PM »
The surging is very strange, some days it doesn't do it, some days it does. I think you're right though, because pressing the brakes, using power steering, or turning the lights on will lower the rpms and it takes a while for it to go back up. With the higher idle right now it's not really an issue. It still revs up to 3k RPMs on cold start up for a second or two, I thought the thermowax delete would prevent this? I'm not complaining though, the 3k RPM start up is fine, just strange that it's still happening. I'll have to find a way to test out the BAC, I have an S5 one, but I think they're different connectors.
1986 AS GXL Turbo swapped
1993 VR R1

Offline toplessFC3Sman

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Re: 1986 GXL engine rebuild
« Reply #67 on: October 14, 2014, 09:41:18 AM »
I've seen the BAC stick before, sometimes only in cold weather, sometimes randomly.  Make sure you have coolant plumbed through the tube connected to it so that it warms up pretty quickly.  I think the factory ECU only uses it as an on-off device, so you could potentially check it by running wires directly to it from the battery and seeing if it clicks (or if the engine speed jumps up, if the engine is running)

Offline murz

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Re: 1986 GXL engine rebuild
« Reply #68 on: October 30, 2014, 01:15:11 PM »
Well, I have the surging fixed, I did the lamp method instead of ohms, replaced the Glimer belt with a dual belt that isn't underdrive. Seemed to have fixed the hesitations as well by redoing a few grounds. I got her to idle near 1200, but anything lower she will try to stall and recover, and that keeps going. So I have her idling around 1500 for now, anyways here's the video.

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I wonder if the high idle is due to the streetport, I doubt it though because the Primaries aren't that big. Anyways that's not the issue, it wants to stall when I brake or use power steering. So maybe it's the BAC?
1986 AS GXL Turbo swapped
1993 VR R1

Offline fidelity101

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Re: 1986 GXL engine rebuild
« Reply #69 on: October 30, 2014, 01:42:46 PM »
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I've seen the BAC stick before, sometimes only in cold weather, sometimes randomly.  Make sure you have coolant plumbed through the tube connected to it so that it warms up pretty quickly.  I think the factory ECU only uses it as an on-off device, so you could potentially check it by running wires directly to it from the battery and seeing if it clicks (or if the engine speed jumps up, if the engine is running)

Have it idling and put your finger on it you should feel the solenoid pulsing back and forth.

Offline murz

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Re: 1986 GXL engine rebuild
« Reply #70 on: December 14, 2014, 06:03:34 PM »
So, my multi meter died a while back, it was a pos any ways... So I'll finalllllly get around to testing out the BAC.

Anyways, in regards to the turbo swap, I've acquired some stuff! 1987 Turbo II complete engine with rebuilt turbo, Turbo II transmission, with light weight steel flywheel, new clutch, pressure plate and Pilot bearing, complete wiring & ECU, turbo AFM, Top mount inter-cooler, 550 Primaries, 720 Secondaries, AND an S4 Turbo LSD Differential.  Oh, the engine has 76k miles on it, but it seems to have good compression currently, (It did when taken out of the original car as well.) But I'll do a legit compression test later on of course.

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So, all that's left to find is...
S4 Throttle Cable (Or just fabricate something)
S4 Turbo Boost sensor
Turbo Half Shafts
New Fuel pump, probably going to go with the Walbro 255L
Downpipe
Fuel Cut Defender thing
Turbo inlet duct
Turbo Driveshaft

Some of these things I already have lined up such as the driveshaft and maybe half shafts.

Anyways, I wanted to go Megasquirt with the NA set up, But... I think I'll just get it Turbo swapped first. Also... thinking of going front mount inter-cooler right away, so I wouldn't need a Turbo II hood. I think I have my ducks in a row... Feel free to chime in!

1986 AS GXL Turbo swapped
1993 VR R1

Offline murz

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Re: 1986 GXL engine rebuild
« Reply #71 on: December 14, 2014, 08:05:32 PM »
Oh, I forgot to mention this old news... exhaust fixed!!! No more exhaust leak, in fact the exhaust sounds pretty damn good if you ask me. Here's a video clip.
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1986 AS GXL Turbo swapped
1993 VR R1

Offline ITSWILL

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Re: 1986 GXL engine rebuild
« Reply #72 on: December 15, 2014, 06:24:36 AM »
Im pretty sure I have the boost sensor,inlet duct, fuel pump and drive shaft you need.
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Offline ~Groll69~

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Re: 1986 GXL engine rebuild
« Reply #73 on: December 15, 2014, 07:31:07 AM »
nice.  what are your plans for your rebuilt NA motor?
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Offline murz

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Re: 1986 GXL engine rebuild
« Reply #74 on: December 15, 2014, 08:12:44 AM »
Awesome, that's really all the hard to find parts out of the way then. Groll69, good question haha, I'm not 100% sure what I'm going to do with it, I was thinking of selling it, but I think I'm going to keep it. I have a 6 port turbo intake manifold, and might make either a 6 port turbo or better flowing NA motor for down the road. I'm not 100% sure though. You are not allowed to view links. Register or Login It will probably be some sort of project.
1986 AS GXL Turbo swapped
1993 VR R1