CIS Gurus - Help me Safely Inject my Hot Rod 3.0

kstylianos · 10:33 AM

82 SC USA w/CIS - Current Mods:
9.8:1 compression JE pistons
Elgin SC330 custom cam grind
SSI with Dansk Sport 2/1
Bore/Blend intake ports/runners to ~37mm

After much research and various conversations, the consensus is that my current CIS will not handle these mods, causing lean mixture (WOT and high RPM's), high CHT, and possible detonation.

Current suggestions were to:
Upgrade to MOTEC, TEC-3 or affix Motronic....NO WAY
Install PMO's/Webers....BETTER, Still NO WAY
Use Fuel Distrib and WUR from a 75-77 Carrera 3.0....Still better but these items are extremely hard to find used and ridiculously expensive new ($3000+).

Ultimately, I still want to use CIS if possible. Are there any other mods to richen my A/F mix throughout the rpm range w/o resorting to other types of injection? My thoughts were that the 81-83 Euro SC's had higher CR 9.8:1 (my engine's major drawback), were produced in greater numbers than the 3.0 Carrera, so used parts would be easier to find. Would the WUR/Fuel distrib. from the 81-83 Euro's be the fix I need?

Please help.....

1fastredsc · 06-02-2003, 10:56 AM

I think the problem might not be the C/R but the fact that you have JE pistons and a CIS system. If you noticed when taking your original pistons out that the had a wierd curved shape to the dome, it had a purpose. Since CIS constantly dumps metered fuel into the sytem, it never completely atomizes with the on coming air. Therefore the shape of those pistons you took out were designed to help swirl the air as it entered the combustion chamber so the fuel would atomize properly before combustion took place. A way to get rid of this need is to use carbs or a sequential fuel injection system, this way fuel is only extracted when it's needed. Plus i'm not an expert on cams as i haven't delt with them yet, but i believe the only cams that our cars accept are sc or 964 cams.

kstylianos · 05:21 PM

The JE pistons ordered are designed to be used with CIS, according to EBS. EBS calls them 'wedge shaped' and have been used with CIS injection with good success.

The SC330 Elgin cams have been used with CIS for the past 15 years. They are not as 'hot' as the 964's but give a better pull down low.

I was using Wayne's 'Top Engine Picks'. He lists the 9.8:1 CR JE's, 964's with CIS. Just curious how to tweak CIS to work with this combination.

69 911s · 06-02-2003, 11:09 AM

Charlie, did the folks at Elgin tell you that this combo would work with their cam and CIS? I would guess that an SC designation indicates this but I'm curious since overlap confuses most AFC injection.
Regards, Holder Trumbo.

dougcl · 06-02-2003, 11:13 AM

kstylianos, Have you run the engine on a dyno, or are you anticipating having these problems? How much power will this engine make?

Doug
75 911S

kstylianos · 06-02-2003, 11:29 AM

The engine builder (CE) worked with Elgin in choosing a cam that would work well with these mods. I also spoke with Elgin personally and they have used this cam in CIS injected SC's for the last 15 years with good results.

BTW: Elgin also offers these CIS custom grinds

SC330 - '1 step up for 911SC. Works well in stock engine, hot cam for Turbo'
Elgin Super C-2 - '1 step up for 911 cs. Hot cam for 911sc with 10-1CR'.

The 964 grind falls in between these two.

kstylianos · 08:53 PM

Doug,

The engine is still on the stand. I'm just anticipating these problems from researching other's similar mods and with talking with Steve Weiner. The reality is that there will be an issue with CIS (currently) not being able to supply enough fuel. Just want to know if adding the 81-83 Euro WUR/Fuel distrib will solve this issue. Steve was not to familiar with these years, but said the 3.0 Carrera (75-77) WUR/FD would work.

The C's are in route to EBS for the 9.8:1 JE's and Nikasil plating. I have put the P/C's on hold until I figure out if this CR is indeed feasible w/ CIS w/o spending $$$$ for the 3.0 Carrera WUR/FD.

If it all works out as planned with the 9.8:1, I'm anticipating 220-230 at the flywheel.

1fastredsc · 06-02-2003, 11:46 AM

Well then if your setup is that well thought out and you have the proper pistons for atomozation to take place, why are you worried about detontion, i don't see the connection. You marginally raised the compression and pushed your torque band up slightly with those cams so why's there a fear of detonation?

kstylianos · 06-02-2003, 12:30 PM

Fastred,

Read Steve's response to a similar mod, only difference is a 3.2 conversion.

http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=1;t=002416#000000

dougcl · 06-02-2003, 12:48 PM

Charlie, I would defer to the excellent advice given in the thread you posted there. However, IF you have already got the engine pieces, and you are committed to building the engine as planned, then TRY (engine dyno) the stock system before you commit to the euro FD (or anything else), which as you know, seems to be quite expensive. There are some folks out there who have put low boost turbo kits on SC engines, which should land them in the same power range you are expecting. However, if they have fuel enrichment, then that leaves you with no basis for comparison. If you are not committed to the engine as planned, then perhaps you should take a few paces back and re-think it.

Doug
75 911S

kstylianos · 02:11 PM

Doug,

I'm not committed yet, the work is on hold at EBS until I decide. But would like (very much) for this to work if I can be done affordably.
The only option I can honestly afford is to use the 81-83 Euro components (probably in good used condition) IF they offer more fuel and a fuel curve that would accommodate my mods. The only reason I think they would work is that the Euros have the 9.8:1 CR. Just looking for some type of confirmation.

dougcl · 06-02-2003, 05:03 PM

I was hoping one of the SC turbo guys would chime in here and say, "yep, I'm getting 230HP without fuel enrichment." There doesn't seem to be a lot of advice out there for those wanting to push CIS beyond stock... probably because step 1 is throwing out CIS.

How about figuring out the max fuel delivery of your stock system while it's on the shelf and there's nothing better to do?

Something else I am thinking about is whether or not you can get away with 9.8:1 on pump gas without twin ignition.

Doug
75 911S

kstylianos · 08:55 PM

Doug,

Steve and I were talking about this on Friday actually. He said I would be able to use 93 or 94 octane (both available here in VA) with out troubles as the cylinder head temps on the street won't get hot enough to promote detonation, even in our hot, muggy summers. On the track, it's another story. I was advised to use a 50/50 mix of 94/100 octane race fuel. This all, of course, is if I get the A/F mix and fuel mapping correct to begin with.

I am hoping also that a CIS expert chimes in........

1980SC · 07:31 PM

If I were you, I would lose the lambda CIS, and convert to k-basic. If you can locate a euro '81-'83 fuel distributor, then go for it. If not, then the USA '78-'79 and euro '78-'80 fuel distributors are more common, and can be tricked into running richer.

Once you switch to this type of fuel distributor (non-lambda), then you use a vacuum controlled WUR. They are adjustable for hot control pressure. The process is a bit tedious, but I've done it several times. By turning a screw located on the diaphragm of the vacuum style WUR, you can lower the hot control pressure, which will deliver more fuel by reducing the force needed to raise the sensor plate. There is quite a bit of adjustment available, and you can really richen up the mixture this way. This is not to be confused with adjusting cold control pressure which gets discussed here often.

I've read, just as you have, about how the euro '81-'83 FD flow more fuel because of the 9.8:1 compression ratio, but I don't know how much more. I would expect that you would have to tweek the hot control pressure to get it to the A/F ratio you want with one of those fuel distributors anyway.

Here is a picture of when I was doing some hot control pressure adjusting :

You of course would want to run the car on a dyno to see what the mixture is doing as you change the hot control pressure.

Here is a picture of the k-basic and lambda fuel distributors. The one on the left is the low compression k-basic FD. The one on the right with the extra plumbing is the lambda style.

If you wanted to stick with the lambda style FD, you would have to trick the frequency valve into cycling faster. I don't know much about that.

Rob
1980sc euro

emcon5 · emcon5's Garage

I think it is more accurate to say your current CIS "may not" handle the mods.

Noah got good power with no problems on his C3 engine with similar specs with a 2.7 fuel distributor. The only difference is his is JE's are 9.5:1, not 9.8.

More info here:

http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic;f=1;t=004403

Quote:

Originally posted by 1980SC
If you wanted to stick with the lambda style FD, you would have to trick the frequency valve into cycling faster. I don't know much about that.

No need to trick it, just unplut the O2 sensor, it will run open loop, slightly richer (fixed 85% duty cycle for 1980, 65% for 81-83)

Tom

edit to correct duty cycle numbers, I went and looked them up.

1980SC · 07:47 PM

Unplugging the O2 sensor is what you do to a stock 3.0 to get it to run a bit smoother. It doesn't address his concerns for increasing the fuel rate so he can get to the proper A/F ratio at WOT on a built motor. The lambda computer operates the frequency valve at those set duty cycles at WOT regardless of whether or not the O2 sensor is plugged in.

I guess what I meant to say was that his WOT mixture will NOT be richened by unplugging the O2 sensor. The O2 sensor is ignored by the computer at full throttle anyway.

Rob
1980sc euro

emcon5 · emcon5's Garage

Quote:

Originally posted by 1980SC
The lambda computer operates the frequency valve at those set duty cycles at WOT regardless of whether or not the O2 sensor is plugged in.

Good point.

OK, how about doing a rich stop test? Should peg the Frequency valve at 95% duty cycle:

Tom

1fastredsc · 06-03-2003, 05:37 AM

Actually, what about doing emcon's idea with the 95% duty cycle and then disconnect the WOT switch that detects the WOT this way it won't go back to default WOT duty cycle but stay constantly at 95%.

dougcl · 06-03-2003, 07:53 AM

All the fiddling in the world won't matter if the FD doesn't supply enough fuel with the sensor plate fully deflected.

Doug
75 911S

tsuter · 08:03 AM

I run the stock CIS and use a single supplemental fuel enrichment injector(CSV) aka Callaway Microfueler set to open at 3.0 lbs of boost. Used to run two of them - one at 3.0 lbs and one at 7.0lbs. That setup was producing about 300-315 HP at 9.0 lbs of boost. Stock CR and cam single plugged for 78SC 3.0.

If you have the lambda loop o -sensor you cut it out at 1.5 lbs of boost and run open loop under boost and then restore when boost falls below 1.5 lbs.