Fuel Injection Drivability and adjustment with 35/75 cam

al_ngl

al_ngl

Resident Boilermaker
My camshaft install has been completed for a while and I now have a working wideband O2 sensor and gauge (AEM UEGO, I know, not the best, but 'tuning' is limited anyway). I've driven the car for several hours with the 35/75 cam and the 45psi FPR (Volvo 960, Ferrari 348, etc.), and I definitely notice a difference in overall acceleration and torque. However, there are a few little issues that I would like to work through, primarily idle, but also potentially messing with the AFM if my A:F ratio numbers aren't good enough.

First of all, the camshaft is a Delta regrind to FAZA 35/75 specs. Valve timing was left stock for now, and static ignition timing is at 10* BTDC by timing light at idle, which at the time of being set was around 1150RPM. The car is running 90 octane unenriched/0 ethanol fuel.

My idle is typically 1200 on startup and 1600 when warm. This is with all idle adjustments at the lowest setting. This slightly concerns me because I would think that the air bypass would be shut and that the throttle butterfly valve would also be shut, so I don't know where the air is coming from. I have confirmed that the throttle will close to its rest screw (also basically at lowest position while still contacting the throttle), and the cable is not binding on anything. My current theory is that there must be a stop inside the throttle body to keep the butterfly valve from opening backwards, which is propping the valve open just enough to idle. Alternatively, the idle air bypass screw on the top of the plenum might let some air past even at its lowest setting. Even with all this adjustment, it would be nice for it to idle a little lower.

Next, my Air:Fuel ratios seem pretty good (to me) for the most part. Cruising at a set speed, the ratios hover from 13-14.5:1 typically. If I accelerate, the mixture richens, and quickly approaches and eventually reaches 10:1 or indicated maximum richness the more I put my foot down. The AFM has not been adjusted with the exception that the idle air bypass has been closed to richen the idle mixture. At idle, 14:1 to 14.9:1 is typical, with very short blips to 13's and 15's being noticed. If I let off the throttle slowly, the mixture slowly leans and then returns to the "set speed" ratio above. If I let off all the way, the ratio cuts fully lean, as fuel is cut. What is of concern is how rich the mixture is on-throttle. I figure I probably need to adjust the AFM flapper a few clicks and re-tension the spring, but I fear this may lean the idle and cruising A:F ratios too much.

Any input is greatly appreciated. I don't think that it is dangerous where it is at, but as rich as it gets under acceleration I want to make sure that I prevent any issues from running too rich, while also keeping it rich enough. I know that L-jet isn't very adaptable, but people do successfully run this cam with L-Jet.

Thanks,
Alex
 
That's a very high idle and you should be able to get it below 1000rpm or more. Look at the A/C idle valve (if equipped, just to the rear of the AFM and mounted on the AFM bracket) and perhaps more importantly, the Auxiliary Air Valve. The AAV is what allows extra air in when the engine is cold, similar to a carb's fast-idle linkage. If the AAV is stuck open or broken, it could cause this.

The AAV is located on down low on the forward side of the block, below the large coolant hoses. It should have a hose one side that draws from between the AFM and throttle body, and the other hose on it goes to the throttle body below the throttle plate. It also has an F.I. harness plug on it to provide power to the heating element.

If your hoses are in good shape, you can test this by simply pinching closed the intake hose to the AAV and see if that changes the idle speed. Another thing to look at is the cam timing, make sure you're not advanced a tooth or something like that.

The rich running issue could be a result of the 45psi FPR. Not sure why you are using that, shouldn't be needed. I wouldn't tamper with the AFM spring myself. The way L-Jet works, once you set the idle CO screw (the AFM air bypass screw), the rest should self-adjust using the O2 sensor feedback.
 
Test the 02 Sensor for Stolic ( sorry cant spell that one) and make sure your getting a signal...:)
 
I run a real Faza 35-75 on my FI, stock everything else. I certainly can't get it to idle smoothly, as it's very lumpy (lots of duration?) I hate it at idle, but at WOT it sounds great and pulls nicely. But I've never measured the mixture, ever. My plugs turn the right colour and everything looks/sounds right - except at idle.

I also have to keep the idle high to keep it running smoothly, around 1400 RPM.
 
Hay

myronx19 and al_ngl what do you have the timing set at ? if it's the factory setting you may have to advance it a little like to 12 to 14 also what do you have your valve clearance set at ? If it's at the factory setting bring it in a little to like 12 Intake and 14 exhaust . These tips where told to me by a vary respected Fiat racer ( Xweb name old fiat driver )that has built many of fiat engines starting from the mid 70s . Oh and it's normal to have to have the idle set to 1200 to 1400 RPM.

Hopefully Charlie ( old fiat driver ) will chime in and put his two cents in .
 
Thanks Bill,

At the moment,my timing advance is stock (10 degrees BTDC if I'm not mistaken). I also tested for max advanced, which looked good (can't recall exactly, but matched the book.

However, I applied those settings after I changed my timing belt last spring, and I believe the advance was at least 15 BTDC and it did indeed make it run better, but still with the high idle.

Shims, oh.. Hmm, I haven't checked for a longggg time. I suspect that it's due for measuring, but I keep putting it off to get my uno turbo motor installed. Heh.. That will help solve some other minor issues I'm having :)
 
al_ngl said:
I know that L-jet isn't very adaptable, but people do successfully run this cam with L-Jet.
Click to expand...

I found L-jet to be a bit of a one-trick pony, and at the cost of some of the components (look at a replacement flapper unit cost lately?) it was a bit of a dry-hole with regards to where you could go in tuning.

At high airflow, the flapper door goes full open and you're out of resistor travel. The Bosch ECU then goes into an RPM driven map totally unrelated to actual air ingestion so you're "squirting blind" at that point. Then you start playing with rising-rate fuel pressure regulators to try and re-curve fuel based on manifold vacuum.

I worked on adapting a hot-wire afm to an l-jet on my 2L scorpion. Had a driving car, good power, but never was as smooth as the original l-jet. After lots of effort, I abandoned the project.

Alternately, I've always thought it would be viable/preferrable to swap over to a more "modern" FI system from a later 80's car (like a Dodge TBI setup) which uses a map sensor and a piggy-back computer for adjustments (like a powercommander for a motorcycle).

Barring that, MegaSquirt seems to have a lot of support.

My $.02, don't waste time trying to tune an l-jet system. It's great for driveablilty and emissions for a street car. But leaves a lot on the table when it comes to building for performance.
 
Thanks for all the responses, they've all been very helpful.

Gregory- I ran the higher pressure FPR because I read that with this cam it is common to run lean, and it was mostly so that I could drive the car knowing it was safe until I got my wideband installed. I reinstalled the stock FPR, and it now idles a little leaner than stoich, at around 15.7 on average. I've been told that this isn't too bad and won't break anything as long as the numbers are richer under load and higher rpms. I haven't had an opportunity to drive the car since changing regulators, but I'm fairly confident the AFR's should be acceptable when driving.

There isn't an A/C fast idle valve (no A/C), and pinching the AAV hose with my fingers didn't change anything, though I just may not have been able to pinch it all the way closed. I will test the functioning of the AAV in other ways. If it does need removed/replaced, do the coolant hoses above it have to be removed or disconnected?

JJay- I think that the O2 sensor is working fine based on AFR's while driving, but I haven't taken a VOM to it yet. Good suggestion.

Racerx- Timing at idle is 10* BTDC. I might try a hair more advance. Valve clearance is slightly loose, but one size down on shims was oddly too tight. .013 intake, .016 exhaust.

cmice- Megasquirt is one of the next things I would like to do with my X1/9, but I can't justify the money right now due to graduating and taking time off to strengthen my resume before grad school. If I can find good employment, MS will likely be a reality, but until then, I'd like to get as much drivability out of L-jet as possible. It is definitely in the plans, as I really want to build my spare 1500 engine for turbocharging, and programmable FI will be mandatory, but that may still be years away. I'm definitely not expecting meaningful gains from messing with L-Jet, I just want the engine to last as long as it would otherwise, and a lower idle would be nice.

In short, I'm going to drive the car and get good AFR numbers, diagnose the AAV, check for vacuum leaks, check out the O2 sensor, recheck cam and ignition timing, and maybe advance ignition timing.
 
You may want to check the "mis for sale" thread over in FS&W.

That car has a mildly decked head and a FAZA 35/75 and is running a different injector (higher duty cycle) to provide adequate fuel, runs stron, and ildes down to around 1k rpm.
 
AAV removal

It's possible with hoses intact, just difficult, but how I did it. On my '87 the bolts were allen-head and it was a pain to work down there. I did it reaching from above after removing intake hose and AFM. I found the bolts were loose and the F.I. harness plug had burnt contacts, like one was gone. Worked better after I fixed that.

Another way to test the AAV is the cause of the high idle is to undo the hose from it where it enters the manifold and block off both sides, see if that affects idle.
 
budgetzagato said:
It's possible with hoses intact, just difficult, but how I did it. On my '87 the bolts were allen-head and it was a pain to work down there. I did it reaching from above after removing intake hose and AFM. I found the bolts were loose and the F.I. harness plug had burnt contacts, like one was gone..
Click to expand...

I had the exact same failure mode on my '82 - bolts were loose, and the harness plug was burned (including the AAV), but I didn't have a high idle as a result. I can drop my idle, it's just rough with the Faza.
 
Digital Fuel Adjuster

rturchan said:
I found this digital fuel adjuster that may be the answer to getting more out of the stock system. Anyone have thoughts on this?
http://www.autospeed.com/cms/A_2418/article.html

Bob T
Click to expand...

Yes, I bought that kit a while back as part of a project to use a hot wire MAF sensor in place of the standard (restrictive) flap type AFM. The output curve of the MAF is fundamentally different from the stock AFM, so incompatible with the Bosch ECU. My plan was to use the fuel adjuster to make the MAF output compatible with the stick ECU (and provide additional tuning potential). Unfortunately, this is all still work in progress.

Cheers,
Dom.
 
Relocate that bugger...

Getting AAV off the block was fiddly enough.
Putting AAV back proved to be worse,
so I relocated the AAV to cambox end on 3 of my FI Xs.
Sorry the pic doesn't show it clearly.
As I recall, I hijacked a preformed hose from the spare FI setups I've scavenged over the years.
Tho' I don't like cosmetics of it sittin' up there,
I like wrassling with awkward stuff even less.

Also note lack of AFM...replaced by tubing with air temp sensor
as part of swapping to MegaSquirt ECU.
Also note extra vacuum line "T"ed off FPR vac line.
That goes to vac port on the MS ECU.

engine_zps4cd16599.jpg
 
I think I have one of these systems...

olerascal said:
Also note lack of AFM...replaced by tubing with air temp sensor
as part of swapping to MegaSquirt ECU.
Click to expand...

I have been looking for info on it. Who did the engineering and would know about it? You? John Allen? Someone else?

Here are some pics of what I have:











Any of this stuff look familiar? Any info appreciated.

Also, sorry for the thread hijack!

Pete
 
Good idea...

I like having it up top as well; like on my Scorpion conversion, and on Betas (coolant pipe). The hardest part is routing the hoses, and making sure the F.I. harness reaches.
 
As Sollozzo said to Michael Corleone...

"I'm not that clever". But John Allen is that clever.
He did brilliant plugn'play development of early MS about 10 years ago,
and built about 28 systems as I recall. I bought two.
One was the beta system now in your possession,
which we installed on my BlueX to develop the VE table.

The same table that eventually was passed around to other Xheads,
both as part of the remaining systems he built,
and as baseline VE table for systems others built.
I think even MattBrannon got that VE table.
Also think moderator MGandini bought one.

Anyway, the beta system was in a generic larger box,
with external resistor (from Honda I think) added.
Subsequent production systems were re-engineered to fit
into OE Bosch ECU case,tho' they both functioned the same.
I've run the beta system, and subsquently the "production" setup since 2004.

Search for John Allen in N54 archives and you'll find lotta posts.
http://www.network54.com/Forum/12159/message/1074483304/Plug'n+Play+MegaSquirt+conversion+overview

John is no longer building those systems.
Send me your email addy and I'll send you files I have on the system.
 
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