Adjusting my rebuilt Carrera RS (style) engine .. frustrations!
 

I have this rebuilt carrera RS (style) engine, it was done professionally on the west coast, I have had the engine in my carrera 74 for a long week now. I actually took some time off to put the car in operations but it has been a tought week.

http://i412.photobucket.com/albums/p...a/PICT0002.jpg

It has been anything but smooth, having spent many hours reading up and down MFI threads I think I have a decent overview ( I also have a 69E and a 70S so I am not that unfamiliar to the system/engine)

I got the engine minus alternator and oil cooler but else it was completely done, rebuilt/redone MFI etc.

My approach was too follow the CMA, throttle sync and correlation seem good. The long pull rod from the bracket must have been too tight, the throttle butterflies would not rest so I took it off and twisted it until it let them rest at idle.

http://i412.photobucket.com/albums/p...PICT0001-1.jpg

Ignition was tested and set static at 0, MFI pump was primed with 3 dl oil, quite a few squirts down the throttle bores and engine came alive last friday, it ran horribly, no way to get a throttle and no way to get the strobo lamp on it to verify, there was popping and backfiring and whatever I did the outcome was stalled engine. Top of this I had to keep revs under 3-4000, thats what I thought at least. The engine would come on quite ok up around and above 3000 rpm but I dont want to run it up with all these other uncertain matters.

http://i412.photobucket.com/albums/p...PICT0002-1.jpg

The only way to check whats happening are the plugs, they are getting black, I suppose we are getting way too much gas.

http://i412.photobucket.com/albums/p...PICT0004-1.jpg

I have spent some 30 hours on it since friday and gone through the CMA.

Ignition: I tried a std CDI system, same problems ( I have MSD that worked great on the old engine ), I tried the original 74 distributor with vacuum (wrong curve but I was only setting 0 and reving up to 25-3500), same burping and backfiring.


So, we are saturday, sunday, monday and half tuesday into the car, its not getting any better. After lunch I used my hot gun to really heat the thermostat once, tried more. Cleaned the plugs again and started it, still burping and backfiring, I have a colleague help me out holding the throttle (though it is almost impossible to find a steady running position) and I more or less veriifed the ignition dynamically to be around 0 degrees 800-1200 with vacuum (impossible to get steady running).

Took out and cleaned plugs, took distributor apart and set .35 mm opening (it was not far off), checked moving parts, installed. Heated the thermostat... checked the main rack, moves fine, checked the fuel pump timing, dead on.

Due to the mixture being way too rich I decided to adjust the load and idle mixuters, leaned the out both. Yes, not the CMA way but what can you do when all else have been gone through?

Car started a little nicer and I kept it running and it was actually getting better now. Took it outside to hook up the LM-2 as running it with the exhaust fan/extractor mess up the reading from the LM2.

http://i412.photobucket.com/albums/p...PICT0005-1.jpg


I was getting AFR around 20-24 on the idle and the load (if we can call it that, ca 2500 rpm) gave me AFR around 14-15, both are jumping more than I would expect but stable enough to work out from. Its getting dark so I have to get onto that tomorrow...

Having tried parrallel ignition systems I suppose the problem was not there, my conclusion so far it must have been the MFI pump.

Have a few questions to the experts;
Anyone have had these problems with rebuilt pumps?
Since I have messed a little with the mixtures, would anyone have some AFR values for idle and part load?
(I can measure lambda so perhaps I can convert from that..)

You haven't been anywhere near a business with MM in its name have you? Just asking!

No, Supertec built the engine. Its tight, quiet and promising but I need to get fuel and ignition correct.

Seems like I have the ignition in place now but I am not ready to take it to 6000 rpm to verify for a while. I had some problems getting the tach adapter to work as well, my LM2 reported 10350 rpm at idle so I know for sure we have mupltiple sparks ;)

I forgot to mention but I also have changed the first oil (to Brad Penn 20-50W "green oil") now, the old oil had about 20-30 minutes on it and should have cleaned out the engine by now. It was slight dark colored,I used a light colored 10-40 performance oil for the initial startup to have a free flowing oil, it is also easier to analyze it after you drain it.

UMMMM, maybe a dumb question, but why doesn't Henry offer you support?
Have you asked him?
Congratulations, however, glad you are making headway.

Doug

Whew! There's hope for you then!

teveo,

I suspect there is some easy solution.

First, you can test the distributor off the engine and confirm the advance curve from static and idle to 6000 rpm (3000 rpm distributor). This will let you set the timing statically with confidence of very close timing at 6000 rpm. You can confirm the 2.7RS advance curve.

You have checked pump timing. Good.

I recommend you force the thermostat to ‘OFF’. Henry sells a mechanical device that replaces the thermostat. I suspect he will lend you one for your start-up. This takes the thermostat out of the equation.


Henry does good work. I want you to confirm the valve adjustment, cam timing, MFI pump model (and research any service or modifications) and the intake components (throttle bodies and stacks size and fit).

Be very careful adjusting the MFI pump. Keep track of your changes. Every time, you want to be able to return to prior setting.

Clearly you are running too rich. As you lean the system, you want it appropriate for the range of operation of your 2.7RS; starting, idle, light throttle, full throttle, peak rpm and more. Proceed deliberately and carefully. You will have a lot of help on the Forum.

Best,
Grady

Hi Grady and thanks for the response,

the engine was built to exact carrera RS specs by Supertec, the only parts I put on it was the oil cooler and the alternator, I could measure it up but distributor is a freshly recurved 030 that was done to carrera RS specs, the mfi system was built to carrera RS specs by Henry as well (or outsorced to Pacific .. ), the engine and components have 30 minutes to one hour them since they left Supertec.

I am persuading the thermostat, will take it apart tomorrow and clean and check, I know there is some good thermostat info in the BBS, just dont have the link in front of me and its getting late (I am the old world, .. Norway to be more precise).

If I have the same work progress tomorrow as I have had the last few hours today I should be able to get decent AFR's at idle and part load tomorrow. First thing I will pull the plugs tomorrow, clean them and start up again. If the engine go off doing some sort of 4th of july celebrations (pop, burp and shoot) I will heat the thermostat for a while first and then start it.

rgds Trond

Two numbers from your posts stand out to me. First, the zero advance timing at idle. Seems to me somewhere around ten degrees initial and 30-32 total at 6,000 rpm is close to spec. I think your initial advance, or lack thereof, could be contributing to the poor running.

The other number is that idle AFR of 20-24:1. This needs to be 12-13:1; it is far too lean to run properly. You need to significantly fatten up that idle mix.

O.k., maybe there are three numbers we should talk about. Your part load mix is too lean as well, but not nearly as bad as the idle. It, too, should be somewhere in the 12-13:1 range.

About half a dozen clicks on the main rack should be close; remember, left is rich on the main rack. This will affect the idle, but not enough to move it 8-10 points. You will have to adjust the idle mixture screw as well. Remember, this one is opposite from the main rack - right is rich.

So, in essence, fatten up the mix and advance the timing. Retarded timing will make it sputter and pop, reluctant to take the throttle. So will a lean condition. You have both.

Jeff,

I am trying to get the afr on idle down to around stoich mixture, for the part load I am targeting to 13.5-14.
The correct ignition on this engine is actually 0 degrees with vacuum at 950 rpm, it beats me but thats the way it is.

I will take the car outside later today and run more tests with the LM2, ... ie if it starts.

Thanks, regarding support, all I can say is that the degree of after sales support vary alot out there but I dont really care now. Henry seem to deliver tons of great information for free on this BBS so the answers may be there to find.

With all the knowledge and experience Pelican users have typed in over the years, not to forget some of the extremely helpful people here I am sure I will have that engine tuned and running like a kitten in the next few weeks ...

Mini-vacation is over and I almost reached my goal, car run but still not great, during the next few days I will take out the fuel console and clean and check it, install a new fuel filter and verify the fuel pressure. I will take out and clean/check the thermostat, pressure test all the injectors, re-read the CMA and perhaps pick up some other points to check/measure/adjust.

My friend,

Your money, your time, your choices.

Henry positions himself as not just another rebuilder but one who stands behind his product. Why are you not getting your support directly from the fellow who did the work? I would expect no less from the shops I use here.

Is Supertec choosing NOT to provide support or are you just not asking for it?

Its not a problem. I suppose they are busy building stuff and I dont really have patience to wait out answers or recommendation for days. My engine ran like crap from first second, I did not take that many days off for the installement and to wait out advice or answers is not ideal.

My MFI pump sofar does not play with but I am sure it will be solved, there are many members here with indepth handson experience that gratefully assist in debugging.

Right now we have snow coming down for the first time this fall, my timeframe stretched alot, running before winter was suddenly changed to running before spring.

It has been a long time coming for me to know the MFI system better, I have two other MFI 911's that should be tuned this winter and a fourth car waiting for a possible MFI engine.

Slight progress today.

I did check my fuel pressure and it was around 12-13 psi in the "primary loop" so that is within spec but maybe a tad low.

http://forums.pelicanparts.com/uploa...1257608613.jpg

My homemade adjustement tools are struggling a little so I ordered a kit form our host, especially idle is a pain in the ***, it seems the hole in the new shroud is poorly drilled/fabricated and I am considering working it a little with the Dremel tool.

http://forums.pelicanparts.com/uploa...1257608874.jpg

Ummm, with a rs curved distributor, there is no vaccuum advance. You set it to 0 with the engine off and at TDC on #1. This should get you very close at 6000 rpm and you can tweak from there if needed.

I went through this this spring.

Another dumb question, are your plug wires going to the correct places?

Are you running pertronix? If you are running pertronix with the S rotor, you need to shave the rotor or else it rubs on the pertronix pickup and the car runs really poorly.

That engine should have run right from the start with rebuild MFI and Ignition, not the way you got it. Furthermore you should not have to put up with them not answering your questions. As long as they seem to find time to push their products on this board, they also should be able to provide some customer support.

Thanks for the feedback & pertronix advice.

I did try to put a pertronix breaker but the axle in the reground unit seem to small, breaker fit tight in my 74 dizzy but on the rebuilt dizzy its loose. I put the breaker points at a tight .35 mm and that wont be too far off. Dwell and timing will be fine tuned when i have some hours on the engine.

Plug cables are correct, the engine is very lively on half open throttle but the low end is a rat. It does however start and run a poor idle now, i also took apart the thermostat and it was of course clean as expected, have not gotten around to check/measure the thermostat more, it seems to work though.

I think the carrera rs was delivered with vacuum, my engine has it and a few engine pix on the internet shows the same.
http://splitwindow356.files.wordpres.../911-rs-2.jpeg

Peter, at this point I decided to take a steep learning curve on the MFI rather than relying on providers, in the future I will spend my money somewhat different.

Disconnect your vaccum advance and see how it runs. The S and RS were pure mechanical advance. If you have a vac advance dist recurved, it is now probably also pure mech with the vac pot still on it - like mine.

Give it a try or call Henry for confirmation on this.

Don't believe the idle readings. The LM-1 with the sensor at the tip of the tailpipe is notorious for giving a false lean reading due to reversion.

If you can, weld an o2 sensor bung up where the three pipes meet, and install the wideband 02 there to get an accurate reading.

Thanks, have read something about this as well, mine is a LM-2 and the modified tailpipe adapter is said to better the results but could be wrong of course.

Maybe I should measure the car indoor with the Nedermann exhaust extractor running then, it sucks bigtime ;) so it would work against reversion...

I have SSI headers/exchangers and I was thinking about welding a bung in the muffler an inch from where it hooks up with the ssi, prefer welding in mild steel to stainless.