As some of you may know, I have to replace my cam because it went flat due to fuel wash. I am currently learning how to do my own tuning. I was wondering if someone could tell me how difficult it will be to tune for my bigger cam. My current cam specs were 228@.050 int and 232@.050 ex. Lift is under 500. Lobe center is 112. New cam is .230 .230@ .050 with a .510 .510 lift with 1.6 roller rockers. Lobe center will be 109. The cam manufacturer says it will be lopey at idle and run best between 3-6000rpms. I want to use the car mostly for racing with little daily driving. Will it be hard to tune for the new cam or should I get a different one? I don't want a roller cam at this time as that will be in my next project motor. Just trying to get a head start on this install. Thanks for the help and advice.

 

my cam is going in today 224/230 @.05 lsa is LSA. with a 114 LSA i dont expect any difficulty. this is a comp cam for computer controled engine. my WB will compensate for my tuning incompetentcy.

 

That's nice, but it doesn't answer my question....

 

dont think too difficult. i will be the first to let you know if i made a mistake. IOW i would not have made change had i had doubts. give me 2 weeks tuning with new cam.

 

109 LSA? i went other route on LSA after getting better advice from others on this board. maybe 112 a better idea?

 

Did I miss something or did my question still not get answered...I am going from 112 to 109. Will it be too hard to tune for and if so why? Is it just a matter of tuning the lower VE tables or do I need to look at other things as well?

 

What you need is someone on this board who has already tuned a 109 LSA cam. Basically, from what I have seen and read, you dont want to go below 112 for LSA.

So, you may be one of the first to try to tune a 109 LSA. So, start with the basics, set minimum air, set static timing, increase the idle RPM in the Eprom. In other words, get it to idle as best you can. That cam will be very loppy for a computer. I would expect that it will hunt for idle forever. You will have to deal with it the best you can. The engine will behave like there is a vacuum leak (I expect).

Then you work on the BLMs, then WOT fueling and timing.

Well, that about covers it!!!!!!!!!!!!!

I dont mean to be funny or not, but I think your biggest challenge will be a suitable idle. Please keep us posted on this. I am very interested in how a 109 LSA cam will idle with an ECM trying to control things.

 

CaptPicardsZ28 the board is kinda slow latley, I think everyone is out Tuning and Racing as much as they can before the dreded Winter. I have no Experiece on you question but most the posts I see about this recomend at least 112 Even When I called CompCams the recommened at least 112LSA even though I told them I can tune My own Proms. I am sure that Grumpy, RBob and the rest will post soon on the technical Reason for this and any problems you will have with a 109 LSA.

 

And you're tuning what kind of system?.
MAF/MAP, TBI, Port?.
Have you read all the stickies?.

 

Yes, I read the stickies as often as I can. I am running the 7730 SD MAP setup on my 85Z28. Tried to answer this much earlier in the day but couldn't. Server wouldn't let me.

 

Yes, you'll have to change the timing and VE some. Changing the LSA changes the self EGR'ing of the engine, and when you increase the EGR'ing you have to add a lil fuel, and timing. The WOT will be a matter of again finding the engine's sweet spot.

 

What do you mean by EGRing? Sorry to sound dumb. I don't have emissions. EGR stuff is long gone. I have a strange feeling that's not what you mean tho. Anyway, I think I will try this cam. After all, It will be good experience to try since the one in my next motor will be a bigger roller cam. Thanks for the help.

 

My 406 has a 230/236, .550/.560 lift, 110lsa. Idles at 40 kPa @ 750 RPM, as smooth as my stock 305 did. It sounds like a stock cam (almost disappointing!). Mine is a solid roller though, that may change things.

It actually ran on the stock fuel and timing tables. I did make changes to injector constant and cylinder volume of course.

 

i recently did a 1227730 on a 383 with hogged out fast burn heads running a mini ram with a 245@50 625 lift 106 lsa cam. it idles with 14 inches of vacum at 900rpm. tid bit gassy on the exhuast though due to all the overlap.

 

That's a pretty radical cam dude, track only car i'm guessing. imagine a 383 with flowmaster 40 series, idling at 900 RPM with 28in. rear tires at a stop light, right next to a cop..... good times.

BTW funstick, did you have to change any of the tables concerning startup? like the crank PW, timing stuff like that? and before it goes into closed loop, how did you know how much to increase/decrease the PW at low temps? trial and error?

 

At overlap, both the intake and exhaust valves are open. With the piston moving down, and with the exhaust having some pressure, some exhuast gases get sucked into the intake runners. Thus, self EGR'ing.

 

Thanks for the clarification...

 

yes had to change basically every part of the calibration.also its a street driven car. gets 18mpg high way and 12 city.

 

I've tuned a 109LSA cam before with more duration and more lift than what you mentioned and did it on a 350. Remember that you can run lower LSAs as you crank up the cubic inches with no real ill effect. Definitely can be done on smaller motors ... and IMHO it was pretty easy to do. I dialed it in even further using the O2 constants to lean out the idle.

Keep in mind that lower LSA cams tend to trick the O2 sensor. Low LSA means the intake and exhaust are open at the same time and thus you get fresh unburnt Air/Fuel going past the O2 sensor (even though your fueling might be nuts on). Thus, the ECM will change the fueling even though you might be 100% already on target for the correct fueling. It sees unburnt O2 and then adds fuel - even though the O2 it is seeing isn't O2 that was a byproduct of combustion. That's why it gets really rich with a low LSA cam on an EFI car. But, it's fairly easy to tune around if you run into that problem.

Tim

 

I'm tuning a decent sized cam on a 350 with a 747 TBI setup, I don't think us TBI guys have the O2 constants like the 730 guys do, or do we? I'm still playing with a stinky idle even though my blm's are spot on. I've played with the int delay vs airflow and that helped but didn't cure the problem. Any suggestions on where to start experimenting?

 

Thanks Tim...your input is greatly appreciated.

 

Tim,

What did you do to tune around this issue? My 02 readings are all over the place, and the ECM keeps adding fuel until BLMs are 160. Anywhere other than idle, it is fine. My lsa is 110. For a while, I thought my 02 sensor was bad, so I changed it and upgraded to a heated version. The readings remain the same. Also checked for vacuum leaks, but did not find anything that would add unaccounted for 02.

Thanks

 

Try open loop (the ultimate test that your tune is right IMO). Also, you can look at 'twiddling the bits in the code' to make it look at a different constant instead of 'temp' to go into closed loop (like mph or rpm). Then you just rely on the "timer" (like 10 minutes or more) to ensure the engine is warm enough.

So you end up with a logic where the engine will only go into closed loop if the vehicle speed is greater than 10 mph and been running for at least 10-15 minutes.

And, if you have source, then you can get REALLY tricky. But for starters, you can "twiddle the bits" so the address of the "temp constant" in the "start routine" becomes either mph or rpm (I prefer mph).

 

Question, clarification, or kick in the head......

I thought 160 BLM was lean and 108 BLM was rich. Do I have this backwards????

 

Well if your BLM IS at 160 and all it really needs is 128, then you are running a bit rich (not achieving true stoichiometric 14.7:1 Air fuel ratio), even though the ECU thought you were lean from a false O2 signal.

 

Red, you have it backwards. When you get a reading of 160 you are running lean and the ECM needs to add fuel. The problem is, the 160 is a false reading due to the "self EGRing" and in fact the true reading is richer than 160 (but the ECM only sees 160).

 

That's what I said, I thought. If the BLM is at 160 (due to false readings), and what it really needed was 128 (with correct readings) then the engine is running rich, even though the closed loop and O2 think it's stoich.

I'm pretty sure I'm right on this. If the BLM is at 160, it has added 32 counts of fuel (25%). If that 25% was addded due to false lean readings, it will be quite rich, depending on where the BLM should be.

Normally, if the O2 sensor isn't getting false readings, then 160 would mean that the ECU had to add fuel to obtain stoichiometry, and that the calibration (or something else) is lean. But this probably isn't the case in this situation.

 

Well, I'm gonna try the cam I mentioned at the beginning of this post. Hopefully it will work out ok at least until I build my other motor. It will be quite a learning experience trying to tune it. I did pick up the Dave Vizard cam book that Traxion mentioned in one of the DIY stickies. Hopefully it will help me understand cams a little better than I do now.

 

Okay, you are talking about the "false" O2 reading, where the engine thinks it's lean (and reading 160) when, in fact, it is running richer and should show an O2 reading less than 160. Thus the ECM over compensates and makes the engine run richer than it should.

Again, that is why a lot of guys now tune for "open loop" once they get a WB and make it run purely off tables. Or you can "twiddle the code" like I suggested to cause it to go open loop only at idle. But, as long as you let the ECM go into closed loop, the ECM will over compensate.

 

Could you elaborate on this a little if you dont mind for some one running a $8D as well as $6E systems as I would like to run closed loop except for low speeds.

 

Eprom burning is a LOT easier than you think. The biggest thing to overcome is the "terminology". Learning eprom burning is a lot like hoping on a fast moving train. You need to do a little reading of the Intro Article and then "just do it".

When you have a specific question, just ask it and someone will always jump in to help you. We ALL had to learn this at one time and we were all beginners once to. Just hang in there and read, read and read.

Also, when it helps to read a lot of the very early posts when most of the guys here were just beginners. Set your search to "the oldest" and read some of the old posts. Many of the quesitons you have, have already been asked at one time or another.

 

Thanks Glenn...your help and support is very much appreciated. I am reading as much as I can and trying to grasp things. My next step is to try and hook up the stuff I bought with the autoprom to see if I can play with my chip. I'm just afraid to screw it up. I have been looking and reading datalogs I took to try and understand what is happening with the car. It's coming along slowly but I will get there.

 

I got it . Its a real good book man ! All of his are . Good Bathroom material