Tuning adjustment for performance mods.

lookforjoe

lookforjoe

True Classic
OK. I have one of Matt's 35/75 cams, milled cam box, locally milled (.075") & ported head.

Cam timing * stock position. AFM wheel in stock setting. CO adjust full rich setting. Ignition timing * 12ºbtdc. Bosch Platinum WR7DP * .028" 3bar FPR, injectors flushed & flow tested (186cc*3bar)

Now that I have the wideband O2, I can see that the AFR's are good at idle; 14.6-15.2 and cruising. However, under part load they stay in the high to mid 14's - only dropping to high 12's- low 13's under close to full throttle, over 5000rpm.

So, my question is, what target AFR should I be shooting for? I'm used to tuning for boost, not natural aspiration. The car feels good, but I'm used to seeing AFR's below 13.5 under load conditions. 14's seems to high, even for a NA setup?

EDIT: Does anyone have the ignition graph for the stock electronic ignition?
 
According to what I have been reading 14.7 is the stoichiometric air-fuel ratio which is good for emissions but not for power. Most articles I've read say that for power you are aiming for 12.5-13:1 for best power and any richer than that is a waste of fuel unless you have a supercharger or nitrous.
I just tuned my carb with a wide band and now get around 12 -13:1 throughout the range and the car pulls nice.
 
Platinum plugs

I'm not a big fan of Bosch platinum plugs, standard NGK or Champion's have always worked well for my Fiats, I'm sure others have a different opinion.
 
They never worked well in FI cars and I think that is because FI runs leaner than carbed cars. The lodges tend to foul a bit but a few good runs up to redline and your ok. I like the multi electrode design because you dont have to gap them or index them and no misfires.
IAP does not stock them anymore and Ive read a few posts on other boards that seem to say that they are no longer in production. I am going to look for some NOS and buy a few sets.
 
Sounds about right to me....

Those running operations pretty well describe my Megasquirt controlled FI engine. I need to run a bit richer at idle because I have a pretty hot cam, but otherwise, about like what you describe.

The FIAT Shop Manual lists for fuel injection Bosch distributor:
10* static advance
16* to 20* at 3500 rpm centrifugal
26* to 30* total advance
12* to 16* at 11 in Hg vacuum advance

I run about 12* static, and when I built my distributor, I tried all the vacuum capsules I could find and used the one that responded immediately upon application of vacuum. Most vacuum capsules hang up a bit or leak.

Oh yeah, and ditch the Plat spark plugs. NGK copper work great.

Ciao,
 
Thanks for all the replies.

I already have set of coppers (WR7DC) so I'll start with that.

It definitely pulls better under load when it's still warming up - AFR's are in the 12-13 range - I'd like to get the AFR's down a bit in the mid-load range, I guess I'll also try loosening the AFM click wheel a few turns.
 
Not to be argumentative...

Just stating the facts as I have experienced them with two X1/9s...

I've run the cheap $1.99 Bosch Single Electrode Platinums for over 8 years... WR7DPs... (they have a new number now...) and they have NEVER fouled or missed a beat. I hate to replace them... over 12K on them in HOT CA operations... I like the FULLY exposed kernal that a small single electrode eludes and I could actually FEEL the difference in performance over a conventional copper plug.

Try'um, I think you'll like 'um!

But ya gotta remember though... I live a charmed life!
 
I had WR7DP's in there...

... I replaced them today with the WR7DC's.

While I was there, I cleaned the rotor & distributor contacts, and found that #2 plug wire was badly corroded at the cap. I cleaned out the cap & the resistance value dropped to about 3ohms, same as the others. It's not a Bosch cap, the outer contacts aren't copper. I'll have to order a Bosch replacement. The #2 wire had extremely high resistance, all the others were in the 6-7K range. I put new wires in, since I had them.

The plugs looked very even, which is odd given the excessively high resistance of the #2 wire. Also, the magnetic pickup air gap for #1 was outside limits. It seems the system has a pretty high tolerance for wear, since I couldn't detect any drivability issues as it was. I set all four air gaps to .014", since that's the middle of the acceptable range.

See how it runs tomorrow.
 
took the car for a drive today...

... my wife & I went out to Rye Playland :grin:

I adjusted the AFM flap 5 clicks CC beforehand, to see if it improved 'feel" under load. AFR's didn't drop much, but it did feel and pull better, and cruising * 65-70 the AFR's stay right in the 14.6-15.2 range, which is great.

The only two issues I have are idle related, and that it seems excessively rich until fully warm. I'm still tweaking the throttle plate, to try & get a stable idle right around 1000rpm. With the larger throttle plate, very small adjustments make a substantial difference. With the rich mixture, I'm wondering if I can get it to lean out sooner by using the heater element of my new O2 sensor (currently unconnected).

I'm also wondering whether it's worth playing with different coolant temp sensors. To that end, does anyone have the spec resistance values? I can't find them in the Fiat Service Manual.
 
Cam timing

Cam timing * stock position

Most of what I have read about milling the head and cam box refers to using a adjustable cam wheel to get the cam timing back into spec. You end up with 4 or so degrees of neg. Disregard if you already have one installed.
 
karhawk said:
Cam timing * stock position

Most of what I have read about milling the head and cam box refers to using a adjustable cam wheel to get the cam timing back into spec. You end up with 4 or so degrees of neg. Disregard if you already have one installed.
Click to expand...


I don't have an adjustable gear - I had it one tooth advanced initially, but Matt suggested I try to get it back to the stock marking. It feels better than it did in the advanced position - it felt more than a couple of degrees advanced, btw.
Not sure how milling the head would shift the cam timing exactly - the change in relative position of cam to valves would only alter the adjusting shim thickness, surely? I understood that it just altered the belt length, hence the need for the larger OD 1300 tensioner...


Thanks for the linky, Greg!
 
Milling the head changes the timing because...

lookforjoe said:
I don't have an adjustable gear - I had it one tooth advanced initially, but Matt suggested I try to get it back to the stock marking. It feels better than it did in the advanced position - it felt more than a couple of degrees advanced, btw.
Not sure how milling the head would shift the cam timing exactly - the change in relative position of cam to valves would only alter the adjusting shim thickness, surely? I understood that it just altered the belt length, hence the need for the larger OD 1300 tensioner...


Thanks for the linky, Greg!
Click to expand...

If you look at the right side of the timing belt, it "pulls" the cam pulley clockwise and is kept tight (it might be easier to envision this without the aux shaft pulley). So milling the head moves the cam pulley closer to the crank pulley, which produces some slack in the belt. This slack is taken up when you re-adjust the tension, but the slack has to go somewhere, and where it goes is a slight rotation of the cam pulley in the counter-clockwise direction. Thus, the cam and crank pulleys are slightly out of phase with each other (relative to their original positions) after milling the head.

Pete

PS forgot to mention, the need for thickness of the adjusting shims is "machined" into the head/cam box arrangement by itself. Milling the head does not change that relationship. Milling the cam box on top of the head does.
 
Pete Whitstone said:
If you look at the right side of the timing belt, it "pulls" the cam pulley clockwise and is kept tight (it might be easier to envision this without the aux shaft pulley). So milling the head moves the cam pulley closer to the crank pulley, which produces some slack in the belt. This slack is taken up when you re-adjust the tension, but the slack has to go somewhere, and where it goes is a slight rotation of the cam pulley in the counter-clockwise direction. Thus, the cam and crank pulleys are slightly out of phase with each other (relative to their original positions) after milling the head.

Pete

PS forgot to mention, the need for thickness of the adjusting shims is "machined" into the head/cam box arrangement by itself. Milling the head does not change that relationship. Milling the cam box on top of the head does.
Click to expand...

Hi Pete

Still not seeing it - I was able to align the cam gear notch precisely with the backing plate reference pin, with the crank * TDC.. My understanding was that the larger tensioner removes all the slack created by the milled head, so I don't understand how that could cause a shift in cam timing that is not evidenced by a shift in the relationship of the cam gear to the reference marker.

Pete Whitstone said:
PS forgot to mention, the need for thickness of the adjusting shims is "machined" into the head/cam box arrangement by itself. Milling the head does not change that relationship. Milling the cam box on top of the head does.
Click to expand...

Yes, I understood that, just didn't express it correctly :rolleyes:
 
" add in a higher lift (than US spec) cam and the fact you've skimmed about 1.6mm from the head deck and you will (almost certainly) have an interference engine...so you WILL need to check piston to valve clearance... skim the cam box as well and you WILL need a vernier timing gear to get the best performance from the cam, and you WILL need a sleeve around your tensioner bearing to make up for the lost distance between cam and crank."

I quoted this from Steve C. since I am doing a similar build to yours, I will be installing a adjustable cam gear to dial in the cam timing, they are only about a 100 bucks from Millers MUle or Apple motors. One tooth on a stock gear is too much hence the need for an adjustable gear.
 
OK, so what is the consensus on the degree of cam retard created by milling the head & cam box? I haven't seen any specific mention of it.

I tried the gear one tooth advanced, which from what you're suggesting, means it was actually only perhaps a few degrees advanced. In my experience, a few degrees on either side of 'normal' will simply alter whether you have a little more top end (advanced) or a little more bottom end (retard). Mine feels pretty darn good right where it is.
 
Increasing the tensioner size does take up the extra slack...

lookforjoe said:
Hi Pete

Still not seeing it - I was able to align the cam gear notch precisely with the backing plate reference pin, with the crank * TDC.. My understanding was that the larger tensioner removes all the slack created by the milled head, so I don't understand how that could cause a shift in cam timing that is not evidenced by a shift in the relationship of the cam gear to the reference marker.



Yes, I understood that, just didn't express it correctly :rolleyes:
Click to expand...

But on the "wrong" side of the belt. The relationship between the crank and the cam pulley is maintained by the right side of the belt, not the left. The crank pulley pulls the belt downward (clockwise), and since the belt can't stretch much, it in turn pulls the cam pulley downward. All that's happening on the left side of the belt is slack removal.

If you milled your head, it should have made it so that your crank marker and cam marker were no longer in agreement with all the slack removed from the right side of the belt. If they are still in agreement, then I can think of several possible explanations:

1. The production tolerances were stacked up to the point where in the original (factory) engine configuration, they were not in agreement, and milling the head brought them into agreement.

2. So much material was removed from the head and block that it produced a full belt tooth of change, allowing them to be in agreement again, although 1 tooth off from the original (factory) agreement.

3. The amount of milling on the head/block were not enough to produce a visual change in the markers (but could probably be seen on a degree wheel).

I don't know which, if any of these, are correct...

Pete
 
Degree the cam

The ONLY way to be sure of cam adjustment is with a degree wheel, which most high performance engine builders do as a matter of routine. Especially when decking the head is involved, with a adjustable cam gear you can dial in exactly what you want. One tooth on a cam gear is like 14 degrees? someone correct me if I'm wrong, and that is way too much adjustment.
It should be the last bit of fine tuning on any high performance engine. And the price of adjustable gears is cheap when you consider the money spent on a high performance engine build.

Chris
 
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