FI idle with a 42/82 cam

BBeaudet

BBeaudet

Daily Driver
I finally got my car on the road and have been having a ball with it.

Here is my dilema though. The car is an 87 and it a has a 42/82 cam in it. The only way I can get it to idle is to set it at around 1500. Anything less than that and it will stall out. It also has to be fully warmed before it will even consider idling and rarely restarts without purging the fuel system by pulling the dual relay and cranking it over.

Has anyone here had any experience getting a cam this hot to run halfway decent with FI. I am considering putting in a toggle switch into the dualrelay circut so I can shut the fuel down before I shut off the car. At least then it will restart when I want it to.

The car pulls well in second up to about 6k third to around 5k. The low end torque is nothing to write home about but it's been so long since I have driven an X that I don't have anything to reference.

Any tips or suggestions on getting this to idle better and hotstart would be appreciated.

Thanks,

Bob.
 
Bob...

With the overlap in that cam it's probably not going to want to idle below 1500 unless you get rid of the airflow meter.

You can do a couple of things to help idle during the warmup cycle though. First, disconnect the electrical connection to the heater inside the cold air valve (down low at the far left on the spark plug side of the head as the engine is positioned in the car). That will slow the closing of the cold air valve since it will then only be actuated by heat from the engine.

If that doesn't give you an acceptable warmup cycle you can adjust the valve to provide more air while it's open. You'll probably have to remove the valve to adjust it-- I'm not sure though because I've not attempted it on an X. The adjustment is secured by a small lock, typically sealed with yellow paint after adjustment at the factory. I forget the exact movement that adjusts the valve but it should be obvious by the time you get that far.

Note that on some valves you can actually adjust it to the point that it won't fully close with the electrical heater disconnected. This might or might not be a good thing. By lowering the idle speed adjustment and letting the additional air through the cold air valve raise the idle you might wind up with a more stable idle speed across a broad temperature range. I try to set them up so that they're fully closed when the engine is *fully* warmed and the electric heater is disconnected.

Kind of at a loss to understand why the engine doesn't want to refire. Don't recall having run across that before. One thing you might try is killing the car by removing the fuel pump relay and seeing if it will relight after you replace it. If so, I guess you could wire in an interrupt for the pump relay so you could shut down the engine without physically removing the relay.

That part sounds kinda strange to me though. Makes me wonder if your injectors are leaking down and getting the plugs too wet to fire. Might try checking to see how long it takes for fuel pressure to bleed off after shutdown.

Will the car refire if you try again immediately after shutting it off with the key? Are the plugs in good shape and correctly gapped?

HTH,

///Mike
 
The injectors are new.

I went through most of the FI system before I realized that the car had a cam.
The car will start sometimes on a key shut down but if it doesn't fire off right away then I a forced to purge. I currently have the idle set off of the TPS. It seems to idle smoother without it. Could this have any bearing on starting?

Are you suggesting that I just unplug the Aux air valve or do I have to go into the internals of the unit to disconnect the heater.

Thanks,

Bob.
 
BBeaudet said:
I currently have the idle set off of the TPS. It seems to idle smoother without it. Could this have any bearing on starting?
Click to expand...

That would make sense; as a fuel saving measure the ECU will shut off the gas when the TPS senses idle and the revs are above 1200. This would normally occur during coasting. That may be messing with your idle settings.
 
Your not the only one to have this problem

I have a FAZA 40/80 in my 86' and have had the same symptoms. One thing to check is the ignition timing. I had been setting mine using the marks and slot in the belhousing which resulted no idle and no hot restarting and poor low end power. I also had trouble with it pinging on hills and heavy loads. I finally reset the timing using the sheetmetal pointer by the crank using the mark on the pulley. I also locked out the vacume advance in the distributor. After going through all of that last weekend my X idles great and has good low end torque, no pinging, and has plenty of top end. It sounds like the first thing you might want to retard the timing a bit and maybe adjust the spring in the air mas meter. I just moved the toothed wheel a few clicks one way and then the other until the idle smooths out provided ignition timing is right.
 
2 problems with long duration camshafts.

One is the Mass Air Flow sensor

The other is the Manifold Absolute Pressure Sensor.

The car is set up for given fuel at MAP value, even a small air leak or calibrated one when the A/C is on will increase the amount of fuel into the engine.

My car is on MegaSquirt and I was unable to set it up on the MAP based part of the program for idle. The MAP values swings 20 KPA, this is not a steady value to work with for idle. MegaSquirt allows for a Throttle Posistion Sensor base program and my idle is smooth at 1000 RPM. Cold starting takes about 3 tries but once it fires the engine warms up nicely. The 40-80 camshaft pulls well and I have it retarded a half tooth and will adjust latter.

TonyK.

Grimsby Ontario Canada.
 
Just unplug it

If simply disconnecting the heater doesn't give you the warmup idle needed then you can readjust the valve. Neither require diassembleing the valve-- don't think that's even possible without destroying it.

The adjustment is quite easy to make-- the nut is on the outside of the valve. Just might not be able to get to it without removing the valve from the car.

Not sure if the TPS adjustment is having an effect on the apparent flooding but it certainly seems possible. I was actually going to ask about the TPS because I've had no problems restarting my car when the idle is set at 1500 RPM and the TPS is adjusted to spec. The engine is dead stock though.

Can't help but wonder if it's not something else though. My memory is terrible but I don't recall any problems restarting injected cars with wild cams. Warmup, idle, and A/C fast idle were all very difficult to resolve to an acceptable degree.

Probably shouldn't say anything since it falls outside the scope of your question, but making such a wild cam work in an AFM equipped motor is kinda like pushing on a string. If the rest of the motor is built to support the cam (BVH, ported intake, >10.0:1 compression, etc) then changing over to a MAF would be easy to justify. If the motor is pretty stock with the exception of the cam I can tell you from firsthand experience that you'd save a lot of frustration and wind up with a more powerful, more driveable engine if you'd just swap the cam for a milder one.

Not trying to sound like a jerk or tell you what to do, but I've been there and done that in my own car, as well as with others. Actually did achieve a driveable combination with injection but the engine never made as much power as it would have had I done the right mods to begin with.

I have a 40:80 Alquati cam in my '76, which is not roadworthy. I'm currently working on a warmed over 1500 for my '85, which will stay with L-Jet until we install a custom injection system and get rid of the AFM. If I thought the 40:80 cam would be a good fit for this engine I'd install it in a heartbeat. No thoughts of doing that though, if that tells you anything.

HTH,

///Mike
 
Hey Tony...

Where is the MAP in an X? AFAIK, L-Jet never used MAP-- that's what the AFM is for. There is an atmospheric pressure sensor on most (if not all) injected Xs to compinsate for changes in altitude, but I don't know of any Manifold Absolute Pressure sensor, or why there would be a need for one.

Is my memory playin' tricks on me again?

///Mike
 
Ooops

You are correct, that is just for Atmospheric compinsation.

I get thinking X then Megasquirt and all the fooling around I had to do to get it there just to idle.

I would suggest looking into John Allens threads on swapping the engine fuel controller for a MegaSquirt unit. My car idles better with fuel injection on MegaSquirt than it did with the 36 DCNF carb.

A smooth idle is just so nice now to have.

TonyK.

Grimsby Ontario Canada.
 
Sounds Pretty Much Like The Way

the yellow X runs with the stock Bosch EFI. It idles lumpy at 1200-1500 RPM, and does not run that well below 3000 RPM. It's real power range is between 3000 to 7500+ RPM and this engine needs to be driven this way. It's far from ideal, but good enough for a fun drive.

Lowering the AFM spring setting helps only a bit, it's not a real fix for the problem of a cam with much overlap in this engine.

I'm going to live with this problem for now until at some point when a conversion to Megasquirt or ? can happen.
 
Thanks for the responses.

I was following the recent threads on FI performance and was kind of figuring that one of my best options was to go back to a stockish cam but I am still hopeful that I can tune this car the way it is to be a little more drivable. I don't do a lot of city driving so I can live with the high idle as long as I can get it to restart reliably.

My plugs have been fouled so many times that I will probally change them out this weekend to see if that helps with the restarting issue. I will also try to tune the car with TPS back online.

One more question on timing:
Should I set the advance as high as I can without pinging or is there a more ideal setting. Right now the car does not seem to rev that freely I can hit 6K in second but after that it seems pretty flat.

Bob.
 
Another point

Hi Bob,

besides the issues you are having, if your engine is otherwise fairly stock, you have mismatched your cam to your engine.
For a street cam, you have probably chosen the hottest profile out there.
This profile is meant to shift the power band up high and make hp up there (say 5000 - 8000 rpm). The rest of your engine, however, restricts the breathing at those high revs (head, exhaust manifold, ...) so that you are not getting the high rpm benefit.

In shifting your powerband, you have taken away the nice torque down low, that the FI engine has.

To make use of the big cam, I would suggest a compression bump, a good exhaust manifold and a reworked head.

Ulix
ex FI-car with Faza 40/80, shaved head, 1974 exhaust manifold, good idle.
 
Ulix hit the nail right on the head. I'm glad someone stepped up and suggested that this cam is simply too 'hot' for this engine.

I concur with Ulix.

Chris
'82 Spider
'87 X1/9
15 other Fiats gone but not forgotten
 
I have also come to this realization.

But at this time it's all I have. The car came with this cam installed and the motor was estimated to produce in excess of 100hp.

When I had the motor out and inspected it the only detectable mod that I can confirm is the cam and a deep sump oil pan so there is just no way this engine in anywhere near it's claims. The head may have been decked but when I posted pics hear folks felt it looked stock.

That being said my preference is to have a car that produces more power than stock so for the time being I may play around with it the way it is.

I am contemplating new exhaust , a bvh and a compression bump.

One more question: How would this cam perform with dual carb's on a stock motor with a header?

Thanks,

Bob.
 
Your least painful options

Hi Bob,

You're thinking in the right direction.
To get that motor to do what you want it to, you have a couple of options:

1. Swap out the camshaft with a 35/75 or less cam. We have great success with the 35/75 variation. I also have a car in the shop right now with an Alquati A-16 that holds a perfect idle with FI.

2. Move to a single 34 DM/ATR on a ported stock manifold, a single 36/40 DCNF (manifolds for these are very hard to find), or a pair of dual 36-40 DCNFs.

The downside is that you need to remove all the FI stuff,
and will need to fit a low-pressure pump, not that big of a deal.

The downside on the dual DCNFs is that tuning can be a major pita, don't expect to nail it in a weekend.

Just so happens I received a whole bunch of dual DCNF intakes recently, brand new! (Sorry, I don't have a matched set of carbs).

Those would be my two options.

-Matt
 
BBeaudet said:
One more question: How would this cam perform with dual carb's on a stock motor with a header?
Click to expand...

Not all that much better.
The more radical one of the components is (in this case your cam), the more important it becomes that the rest of the engine matches that same state of tune.
With your cam, you should have dual carbs, BV or professionally done head, as much CR as you can, efficient exhaust. That would be a nice package :)
 
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