Tuning the turbo: CO levels, mixture, etc.

[RarlyL8]

If you turbo guys have been following the "getting blown this weekend" thread you have seen I'm having a few difficulties.

I'd like your input.

- engine seems to be running really hot. It warms up in minutes with exhaust temps that will combust cardboard in a heartbeat (ambient temp is ~100F).

- fuel mixture appears rich. The car surges at idle (when warm) and raw fuel is present in the throttle body.

You have to have octopus fingers to reach the fuel mixture screw and the idle adjustment. Any tricks or advice?

Thanks.

[WydRyd]

Sorry dude, I can't help here as mine is Motronics based, however, you might want to post on 911turbo.com. I'm sure Stephen of ImagineAuto will tune in and provide whatever assistance you need. He's very helpful and knowledgable with the CIS based 930's and tuning requirements etc. If he doesn't tune in, someone else will.

Maybe Bruce.M has some input, since he's got a 930 which use to be CIS'd before he migrated to Motec injection.

[dougcl]

Maybe you could summarize your setup. CIS or what?

[RarlyL8]

Sorry bout that, there are so many folks on this board that I forget to update (or backdate) my stories.

Here is the deal in a nutshell:

Turbo swap into a '78SC
- Motor is '78 930 w/CIS
- SC cams
- K27-7200 turbo
- 1.0 bar spring
- Euro exhaust w/no smog equipment
- Stock type muffler
- Large B&B Intercooler

Everything has been rebuilt and needs adjustment. This is my first turbo motor so I'm not familiar with the quirks or tricks.
I understand the relationship between timing, fuel mixture, and idle adjustments but don't know what to expect from the tuning inputs. Timing would be my guess as to a starting place, then fuel mixture, then idle.
Little things cause big problems, such as - do you tune with the air cleaner on? An if so how do you reach the set screws? I physically cannot reach them due to the stock airbox and my big hands.
There also may be some problems with the CIS. This will also muddy the waters. I'm hoping that the tuning can be done in spite of possible CIS problems that will bear themselves out afterwards.

I'd just like some input from folks who have tuned these engines and can tell me how they should behave given the different tuning inputs. I have a friend with a 930 who is very helpful but is short on time right now.

Thanks

[beepbeep]

First off all, install A/F - gauge. It's always helpfull...even ordinary narrow-band type. Exhaust-temp gauge is also pretty handy.

When does engine get hot? Just idling? How do you measure the temperature? Are you looking at oil-temperature or do you have some sort of exhaust-temp guage plugged in?

Is your car on the dyno or are you doing it on the street? Do you have intercooler?

These thing will reduce temperatures:

1. More fuel
2. Retarded ignition on boost (it will lower the power as well)
3. Less muffler backpressure (OEM muffler is crap)
4. Sucking in cool air (Stock air-filter box is good)
5. Intercooler!

I suggest not to use too much boost when getting all tuned-in. Running stock boost gives you some error-margin. At 1.0 bar, this margin gets much thinner and bad ingition timing/fuel probs will cause problems that cost $$$$.

Good luck!

P.S. Exhaust tubing will always get pretty hot on 930 beacuse of turbo, especially in hot enviroment as yours. That doesn't mean that engine itself is running hot.

[rboylan]

Brian,

Forward an email to richard_boylan@trendmicro.com with your phone number and I can share the pain and the solution. I hope all is well.

Rich

[RarlyL8]

Thanks guys.

I have an A/F meter, it isn't hooked up yet.
The engine has an intercooler and is in the car. The oil temp gage shows a very rapid warm up rate and the exhaust gets terribly hot. The gage may not be working properly due to mismatched sending unit. I'm mainly going by the exhaust heat. I cannot begin to drive the car in this condition. No real tuning has been done yet, I'm trying to figure out where to start. Trouble is I don't have a baseline feel for these motors.
That's where you guys come in.

[jbailey930]

Rarly,
have you tried Stephen at www.imagineauto.com ? He's built regular turbos, big bad turbos and 3.2 turbo variants. He should be able to help tune you in. 913-310-9927 is the number in KS. His partner is located somewhere in IL too.
Good luck

[JohnC]

Sorry O'l crotchety one I can't comment on the intricasies of K-jetronic 'cause I ripped out the motor before I had the pleasure of "tuning".

However I did have an experience where I pulled off the road to put air in my rear tires and was standing with my foot nearest to the rear quarter panel (driver side behind tire).The car was idling at the time. When I reflexively jeked my foot away from the car.It felt like my leg was against a hot exhaust pipe and this was with jeans on! It turns out that the heat from the exhaust and the cooling air from the motor tends to be REALLY hot!

My car tended to run rich also. So I don't think that you can tell just by "feel".

Also if your paranoid take the plugs out to see if there are any signs of a lean burn situation.

[rattlsnak]

How long has the cis fuel head been sitting? This is VERY common for the slide valve in the center of the fuel distributor to stick. This will cause all sorts of problems. It must move very freely. You have to take the top of the head off to see it though. (just the three allen heads and the fuel lines) Lift it up and you should be able to move it up and down with the weight of your finger. Should slide easily. Even sitting for 2/3 months can cause this. Running too lean will cause hot temps, not too rich. Unless its misfiring, excess fuel cools the cylinders.

[beepbeep]

OK, so you have Lambda-sond that isn't hooked up yet?

(Btw. You can always measure lambda-voltage by ordinary Volt-meter and look in the tables to see how rich you are running)

My first bet would be to check ignition timing. If ignition is very retarded, mixture will burn in exhaust-pipes and heat them up pretty quick.

Also, your engine is recently rebuilt? Newly rebuilt engines still have some internal friction and will gradually "loosen up" after a while. (They recomend using Mineral-oil during break-in period, to be replaced with fully synthetic later)

I would do things this way:

1. Hook up lamda-sensor to either A/F guage or voltmeter.
2. Check that CIS fuel pressures are OK and WUR is working.
3. Adjust ignition timing according to factory specs (i think this could be the culprit, if it isn't done)
4. Adjust idle-mixture, first to lean (when engine almost starts sputtering), then back a bit until it starts spinning better (this will be hard to do if your ignition-timing is far-off as engine will sound bad anyway).
5. Start driving the car and keep eye on temps and A/F gauge, not using any boost and monitoring for oil-leaks and such.

Also, make sure no stupid mistakes are done, like wrong-timed camshafts or bad oil-cooler.

Adjusting idle-mixture w/o airbox shouldn't make an problems as long as you don't drop something into intake


Good luck!

[RarlyL8]

I have spoken with both Stephen and Michael of ImagineAuto, we've become very familiar in recent years. Both can be difficult to get ahold of due to their customer schedules.

The "feel" I was looking for is more of how things sound when they are NOT working right. The idle has a surge in it that I think indicates a rich mixture, but I haven't adjusted that yet so I don't know. What should the engine sound like when a) the mixture is too lean or b) too rich? Somewhere I'm sure I read that the idle would surge when adjusted too rich. I can't get to a CO meter until the "rough" tuning is done and the car can be driven.

The CIS sat for quite few months after being rebuilt. I removed the fuel head, freed the stuck piston, cleaned everything real good, and put it back together about a year ago. It appears to be moving properly. Again - no tuning and very few adjustments have been made at this point.

I plan to first adjust the timing, then the mixture, then the idle.
It looks like I have no choice but to remove the aircleaner to do this. I tried Sunday and simply cannot reach the adjustment screws. The SC engine bay dome must be more shallow than the 930, I can barely get the aircleaner off. The A/F meter isn't hooked up yet 'cause I didn't think it could help me at this point (target calibration is 14.7).

My post is very premature as I haven't done any tuning yet. The purpose of my questions is to help me save time by not doing things that either won't work, shouldn't be done, or may cause harm. The 930 manual sais to always make adjustments with the aircleaner on. I can't see why this is so, but hey what do I know?

[juan ruiz]

Rarly L8,
I don't have any advice regarding the problems that you are encounter BUT take it from me take a few days away from her just relax I know is easy to said that to do it, but sometimes things are a bit more clear, you have waited so long whats a few days more.

[dean]

Do the timing first. You can't adj the mixture with the aircleaner on. It is not possible to get the allen wrench in with the housing on. If the timing is good and the motor is rich it won't heat up fast like you are saying it does. If it will rev to 4000 rpm then set the timing per factory specs. Then play with the mixture. I set my mixture on the rich side until I got my CO meter. It was at 7% then I leaned it out too 3%. It runs like a dream now.

[Natchamp]

Yo Dude, glad to hear its finally running.

1st, get out the laptop and load up the Haltech engine management system.....just kidding. I don't know much about tuning the CIS system but might be able to help with diagnosing what the current rich/lean/timing issues are and what direction you might need to go. Can you give me a call? It's much easier than dueling emails. If you don't still have my number just shoot me an email.

[rattlsnak]

You can very easily adjust the CO with the air cleaner on although the method is crude!! Simply take a big prybar and wedge it between the top of the airbox(where the sensor plate is) and the bottom of the package tray and and "bend" the lower piece of metal upwards. The metal there is two sheets thick, and there is about 2 inches of room between the the upper and lower. Sounds crude but you cant notice it at all, unless your looking for it. Your simply narrowing the gap. This will give you a good two inches more to squeeze the allen wrench in there,!

[RarlyL8]

Thanks guys.

I know the tuning order - timing, mixture, idle. What I am hoping to find out is how the engine runs or sounds when the mixture is too rich or lean. I know you should always tune rich then back it off, but what if it is already too rich? There is no cloud of fuel or smell out the tailpipe, but that may not be a good indicator. The difference between 2% and 5% CO might be undetectable at the pipe. I don't know - do any of you?

Blown- you said yours was set at 7%. How did the engine run? Did it smell of fuel? Did it surge?

My air filter housing has been "modified" so I can get it off the engine. How freaking rediculous is it to have to lower an engine to remove the air cleaner? GOOD LORD. Having spoke with a few folks today I will now remove the aircleaner for tuning. I realy have no choice, my hand will not fit with it on. I can easily get the 3mm allen wrench on the mixture screw with the housing out of the way. Of course I have to take the intercooler off first and then put it back on. THESE STOCK AIR CLEANERS SUCK and it's not in a good way. The triangular Edlebrock unit looks pretty good to me about now.

Timing - I know what the spec book sais. What are you guys running at the distributor? Are you dialing it back when using the 1.0bar spring?

Hey Mark, how is the Beast running? Got that paddle shifter working yet? I'd like to call you and talk shop. Right now I'm being WAY too over cautious. I've got more money in this motor than I paid for the car!!!! It's taken a bit of the fun out of things (sure I don't have to wine about budget overruns to you - ha!)

In a nutshell - what settings do you guys recommend for my break in period? I have 94.5 octane fuel in the tank and a pretty healthy intercooler.

[dean]

Brian,

Relax,

Yes when my motor was at 7% CO it stunk like it was rich. It didn't want to idle (too slow). And when I accelerated I could see black smoke behind me.

I also have a custom air filter housing. I have to take the intercooler off, then the housing, then put the intercooler back on, set the mixture, then reverse the process. I do this all with the motor hot so I minimize running the motor without the aircleaner. But you do have to do it. I did design the housing so that I don't have to lower the motor. It just comes out.

[Natchamp]

Rarly, how much trouble to hook up the O2 sensor/gauge? Even a narrow band 0-1v will give you an idea of where you are at. Just don't depend on it when you start tuning under load. If the engine is surging at idle it is too rich but I can surely relate to not wanting to lean anything out untill you know for sure. Where is your ignition set at? Is there any chance its not advanced enough? If it is too retarded, the combustion cycle will be too far off on the "back" side of the cycle and the flame front (heat) will be going right out the tail pipe heating up the exhaust very hot. If the motor is also running very rich it will compound this problem. Being very rich will not "always" be cooler. As long as the motor is not under any load you can play with the settings a great deal without hurting anything provided the thing doesn't get real toasty. You might try ignition of 8 degrees at idle, 12 at 2,000, 19 at 2,500 and 23 at 3,500.

The Beast is running very good. To be honest, I've back-burnered the pnematic sequential shifter. After 3 years of working on the thing my motivation is somewhat faded. The bummer is I really have it all figured/planed out and it would be really cool. I just have other priorities at the moment. I still haven't fine tuned my motor. Heck it has way enough power the way it is so its not like I need it. I'm still very rich (10.1) under full boost. I am going to be ordering some different injectors and installing them before I finally take it to the dyno for final tuning. I think I'm over "injectored" with 42lb. It is very touchy on the throttle, doesn't want to idle, etc. Any slight change in the mili-second duty cycle means a lot more fuel with those injectors. I am going to run 31lb's and those should still make 400 horsies. Heck, I still need to get the thing aligned and put some sway bars on it. Work is just kicking my butt so all in due time. It is fun to take for short romps on the weekend, as I'm sure you will be enjoying shortly.

When you get to the point of load tuning, I will loan you my wide band O2 if you are interested. Nothing else will do.

[hilandscott]

I second (or third) the comment about ignition timing being crucial-- retarded timing can really heat up the cylinder heads in a hurry.