bshusted

iTrader: (1)

So I got my streetported S5 engine in and running now, but it seems to have some trouble in the low end. I don't know if this is how it is supposed to behave or if I'm still having ignition trouble. Here is what it does: If I'm just rolling along in 1st and put it to the floor it will bog and spit for a second but then as soon as it gets to 2500-3000rpm it takes off and throws you back in the seat. I don't take it up past 4k because I'm still working on breaking it in so I can't say much for the top end but it sure seems to have no power down low. Thoughts/suggestions are greatly appreciated.

trochoid

iTrader: (6)

Carb or FI?

bshusted

iTrader: (1)

Sorry, I should have specified. It's the stock EFI and ignition.

84stock

iTrader: (5)

5th and 6th ports wired open? S5 computer or se computer?

bshusted

iTrader: (1)

The auxiliary ports are actually wired shut for the break in and I'm running the S5 N350 ECU.

trochoid

iTrader: (6)

Iirc, the levers for the S5 work in reverse to all earlier models, check that they really are closed. How big of a street port, who's template? Not that it will make that much difference.

I had the same symptoms with my 1/2 bp until I went with the Weber Dual DCD carbs that close off the secondary intake runners when only the primaries are open.

I'd be looking at vacuum lines, vacuum advance, check for leaks, check timing, etc.. Do you have access to a wideband?

Zentar44_ed

iTrader: (1)

agree with trochoid....check ignition timing too...

bshusted

iTrader: (1)

You are correct in thinking that the S5 ports are reversed. I have made sure that they are really closed. I have been looking for vacuum leaks but I should look more. It likes to idle high, which may be the result of a vacuum leak.

I have been having other ignition problems, which I believe have been solved now. I had the CAS off by a tooth, and it ran really bad. I also had a bad plug wire. Both of those problems solved now. There is no vac advance since I used the stock Crank Angle Sensor. As I understand it, the computer controls the spark advance. Maybe I should post on the FC side of the pond for help on that.

A wideband would be helpful but I don't think I know anyone who has one or has access to one. I will definitely ask around though. Thanks for your response.

trochoid

iTrader: (6)

"Other side of the pond." That's the most tactful description of the 2nd gen forum I've heard to date.

I'm not that familiar with the S5's. Do they really not have a vacuum advance? With a vacuum leak, the first impulse is to adjust the throttle screw, which narrows the opening of the butterflys in the throttle body. As a result, as soon as you touch the go pedal, they may be opening too far too soon, causing your bog. Adjusting the throttle plates requires a readjustment of the TPS.

Find and fix the vacuum leaks first, adjust the idle speed, re-time, then reset the TPS's.

RX-7 Chris

iTrader: (19)

it sounds like it is getting lean when you first hit the throttle but I don't know alything about efi.

bshusted

iTrader: (1)

Well, I tried driving it today to work ~1mile. It fought me the whole way. It would just buck and bog until it got to 3k and it would take off. The idle is terrible. When I got home from work I hit it with the timing light again and it was right on the money. Just for giggles I decided to check the trailing...T1 was at the timing mark for the leading and T2 was way out in left field. How can the leading be on and the trailing be so out of whack? I did some hunting for leaks as well and I am pretty confident that I am not leaking any vacuum (starting fluid method). There really is no vacuum advance on the CAS. According to the FSM all of the advance is controlled by the ECU. My thought is that the advance in the ECU is playing games with me.

RXDad

iTrader: (2)

Try connecting the timing light on T2 instead of T1. If the trailing timing mark lines up, your CAS is not stabbed correctly. Remember that the Leading is wasted spark and fires both rotors every 180 crankshaft degrees. Trailing is for each rotor is fired every 360 degrees, followed by the other rotor 180 degrees apart. If you think that the CAS is stabbed wrong, try resabbing the CAS. I believe that there is a write-up on how to find TDC and how to stab the CAS in the TDC position.

RXDad

trochoid

iTrader: (6)

If T1 and T2 timing marks don't match, make sure you have the wires plugged in correctly.

thunkrd

iTrader: (1)

disconnect the trailing wires, see how it runs(at least until you can figure it out?). how much does an s5 need them?

i accidentally plugged mine in incorrectly. it was running so bad, i thought the car went into lawnmower mode. then i unplugged the wires. it ran way better. then i was like omg how stupid am i?

bshusted

iTrader: (1)

So, let me get this straight. When I have the light on T1 the trailing mark should line up with the second mark on the pulley. T2 should also match this mark if what RXDad is saying is true (that they are 180 out of phase). I have wired the plugs incorrectly before too, but this time I am sure that they are correct.

Someone else suggested to me that maybe I am having trouble with the primary injectors and it runs better in the higher rpms because the secondaries are on. Anyone know when the secondary injectors start to fire in the S5?

I think my next step will be to wire in a Check Engine Light so I can check the code.

trochoid

iTrader: (6)

Secondary injectors kick in around 3600-3800 rpm. Much later than your engine is coming to life at present. Recheck the timing for L1/T1 when the engine is warmed up. If the cas is stabbed correctly, the bolt that holds it down is near the center of the slot for adjusting timing.

Since RX7Dad and I have given conflicting results on when the 2 trailing plugs fire, I'll defer to him. I was thinking the trailing plugs fired at the same time but I believe he's correct in saying that the leading fires at the same time, which becomes the wasted spark on the 2nd firing per combustion. If I'm wrong on that, someone please correct me.

You didn't specify but I'm assuming this is a fresh engine. If that's the case, it may simply be that the seals haven't seated yet, resulting in low compression at low rpms. Once the rpms come up, the seals seal better.

RXDad

iTrader: (2)

I like Thunkrd's approach. If you disconnect temporarily, the trailing plug wires and it runs right, it's an ignition problem and you don't have to even think about injector problems. If not, it's something else.

You don't need to run trailing spark to run right. I don't even have trailing hooked up right now.

RXDad

tasty danish

iTrader: (5)

If this is second gen stuff, the trailings get there own, and the leadings fire together in a waste spark configuration, that is, unless you venture on down to the haltech section and read up on the way to trick it

bshusted

iTrader: (1)

When I go to work on the car today I think my first test will be to unplug the trailing plugs and see what it does. My second test will be to unplug the secondary injectors and see how it runs. If it still does the same thing with the secondary injectors unplugged, then the problem must be something other than fuel.

This is a fresh rebuild as trochoid pointed out. Is it really possible that it would make that much better compression at low rpms? I could hit it with the compression tester today and see. Is it better to use a leading or trailing plug for compression test?

While I'm at it today, I think I will wire in a CEL and see what code is being thrown. Maybe that will shed some light on the subject.

trochoid

iTrader: (6)

My point was that it may not be making very good compression at low rpms, better compression at higher rpms. The thing is, there shouldn't really be that much difference between the varying rpms unless an apex seal is sticking or the apex springs are weak.

It doesn't really matter if compresion is tested at leading or trailing. I myself however prefer using the leading just in case something has has managed to plug the smaller trailing hole.

bshusted

iTrader: (1)

Well I didn't get to testing compression tonight, but I did spend quite a bit of time working. To start off I unplugged the secondary injectors to see it would make a difference in the higher revs, no change. I unplugged my trailing plugs and ran it, no change.

My next check was fuel pressure, 65 lbs...does this seem high to anyone else? The fuel pressure regulator on the secondary fuel rail is not bleeding off any of the pressure though the return line. (bone dry) I disassembled the fuel rails and tested all of my injectors. When I reassembled the fuel rails I swapped the injectors primary for secondary to see if it made a difference, no change.

Frustrated, I pulled out the timing light again to see where I was at. I could not get a signal from the leading coil on the front rotor. All others seemed fine. I swapped the wires just to see and had the same problem still with that terminal of the coil. I checked the resistance of the coil's terminals as per the FSM and everything checked out. My question is how can one terminal of the coil fire and not the other? Aren't they directly connected?

I'm still working on finding the wires that got pruned out of the wire harness for the CEL.

trochoid

iTrader: (6)

Fuel pressure directly from the pump should be running 64-85.3 psi. Fuel pressure at idle should be 35.6-37 psi without the vacuum hose disconnected, with the vacuum hose connected, pressure should be 28.4 psi. Injection pressure should be 35.6-37 psi. If the fuel pressure is higher than the 2 later stated numbers, find whatever is preventing the fuel pressure from bleeding off or replace the fpr.

As far as the leading coil, I would try another one in case the one you have is 'half' dead.

Since I don't have a hard copy of the S5 FSM, this info was taken from the 87 edition.

Kentetsu

Good luck man, but it sounds like you might have already found your issue. Get another coil pack and try again. If for some reason you can't find one, let me know, I've still got a couple laying around here somewhere.

Think you'll have her ready for the June 21st race? Dying to see it!

bshusted

iTrader: (1)

Well I have some wonderful news that ends in the car purring like a kitten. I thought I was having spark trouble from the leading coil, but as it turns out, the plugs would spark outside the block from both sides of the coil. The high fuel pressure was really bothering me and when we got to thinking about it, if the pressure is higher than the computer thinks it is, then when the injector opens it is spraying in way more fuel than it knew what to do with. The FPR on the end of the secondary rail is shot. At idle I was near 80psi. I checked the vacuum signal and it was pulling around 10in Hg. Since I didn't have another rail kicking around, we made a regulator. Granted it isn't the greatest, it makes the car run like it's new. We cut the regulator off of a fuel rail for an escort (it was available) and put it in series with the feed to the secondary rail. Presto! 40psi on the money and no more crop dusting. You would not believe how much better it runs. I can only figure that the plugs on the front rotor were fouling so fast that they never had a chance to fire. Now it is a turn key operation. No pumping the pedal at all to get it started. I could not be happier.

n0ferz

iTrader: (4)

Thats good to hear man, enjoy your 7