I've got an engine swap planned, and instead of going TPI or something like that, I've decided to just stay with the Throttle Body Injection I've got on my RS.

I'm not really experienced at all with this tuning stuff, but I think I can learn.


Here's the problem... I'm going from a 305 to a 361. I dont know if it's possible to come up with some sort of "safe" base tune to break the engine in with or not. I'd really rather not have to find a carberator just to throw on it for the break in period, but I dont want to potentially destroy a brand new motor I'm putting together either from a crappy tune.

Do you guys have any ideas? Is it possible to come up with some sort of conservative tune that should be safe to break in with and properly dial in the car later, or is that one of those things that's kind of a crapshoot where a safe tune on one motor will not work on another? Im not sure how much leeway there is with this computer stuff...


THanks guys!

are you camming it, if so the specs

Well this is a motor on a tight budget. It's not even built yet. All I've got so far is the block and my pistons. Im thinking I may be able to start throwing hte bottom end together early next month if things play out well.

But Im tryin to get everything planned out. At the moment I'm planning go with a cam somwhere in the neighborhood of 204/214 with maybe 114 lsa, but since I"m not limited to a stock TPI tune anymore Im not sure if I'm gonna stay with that or not. Also going with 083 heads.

Not sure if that really answers your question though.

That cam is exceedingly mild. I actually think your factory calibration would probably be pretty close as it is, let alone damaging your engine.

The thing you'd probably want to is adjust your displacement constant in the calibration to go with your increased cubes. I'm not familiar with TBI code, but in the TPI code, there's a value in the constants table that corresponds to engine displacement. I would guess that there is something analogous in the TBI code.

I’m not an expert on TBI (or EFI for that matter). I started my “new” 406 with speed density TPI and mild 214/224 cam without too much trouble. I made sure the injector constant was set for 30# injectors and that the displacement was set correctly for the 406. (I’m also using a modified BIN s_aujp3 that fixes a fuel limitation affecting larger displacements. Search on the board to make sure your stock 305 TBI injectors will support 361ci of displacement.)

I also asked on the board for advice before starting the engine and was advised that the stock fuel tables should be okay to start since my cam was mild and the displacement was increased. On initial start up, I mistakenly left off the distributor wire so the computer could not advance the timing properly (initial setting was 6 degrees), so I believe I was burning fuel in the headers since I melted (to a crispy powder) a few of the plug wires. After hooking up the distributor, I also reduced the lower RPM fuel table by 10% across the board to finish up my break-in. I didn’t burn any plug wires after that. Now I’m getting ready to start tuning – once the weather gets better.

Start immediately.....
Gather the bits and pieces, and start *tuning* on the stocker. It's MUCH easier to learn on a stocker, then try to get up to speed on unknown.

Get in get your feet wet, take notes, look for trends. Just that easy, and once you get some time under your belt it all *jells* alot better.

Im more concerned about the break-in period... Even if I know how to tune it, I'm not sure how easy it is to have a brand new motor ready to run in the applicable RPM ranges on a rough tune. I've still got to run it to dial it in, but I've got to have it dialed in to break it in... I just dont know how hard it would be to get it dialed in well enough to break it in.

I keep trying to look up cam swaps and tuning, but it's hard to find anything in the search. I'm not sure if I'm looking in the right places, but I may very well be going with a bit more aggressive cam. Still on the mild side but maybe something a little more than what I had planned originally. Would this change anything?

A “bigger” cam (lower vacuum signal) appears to the EFI system like an engine under higher load. The system will provide too much fuel at lower RPMs. Traditionally tuners have reduced fuel on the lower end. The recommendation to me was reduce fuel in lower RPMs to keep from washing cylinder walls with too much fuel.

When you say break-in do you mean the first 20-30 minutes of above 2000 RPM running or are you talking about the first 500 or so miles of driving? Initial break-in (running above 2000 RPM) was to support the break-in of a flat tappet cam. If you have a roller cam, you probably don’t need that kind of initial break-in. Search for the break-in procedures for a roller engine.

Unless there was real problem (vacuum leak, really poor spark, really low/high fuel pressure, incorrect injector or displacement setting) I don’t think you would be so far rich or so far lean as to hurt the engine on startup, but you’d need to start tuning right away to get the fuel closer to what the engine requires before daily driving.

It's gonna be a flat tappet block, so I've got to get the cam broken in and then be able to drive it enough to get the rings seated...

you will be just fine for your initial 2000rpm breakin for the cam.

If I were in your shoes, I'd do nothing more than disable closed loop (set the enable temperature to 255), account for the extra cubes and different injector size (if you change injector size) by setting the base pulse width or whatever means the TBI system uses, and then go for it. You're basically building a stock motor so a stock calibration is not going to be so far off so as to melt things down.

On the flip side, I know that roller cams are expensive, but with todays oils and the benefits of roller cammed engines, you should at least consider going roller. you won't have to deal with 2000rpm for 20 minutes, or having a cam failure (which are more common with todays oils and flat tappets during breakin), or any of that stuff. plus, i'm of the strong opinion that roller motors just last longer as well, less wear metal throughout the engine.

May be some othe more experienced tuners can comment on my thought.

Do as all the others suggested.

On initial break in I would link to aldl before. run a winaldl datalog while engine is at 2200-2500 rpms in neutral. make FPR adjustable. adjust fuel pressure while engine is running so as to get a 124 BLM. you may have to stop and start engine as you verify BLM. this will put A/F temporarily at 14.0/1 during breakin. a wide band 02 setup would be better(tailpipe) but not necessary. let it run as long as you feel necessary to break in. change oil and continue log on street. adjust tune as needed per your logs.

I disagree with adjusting fuel pressure to hit an arbitrary BLM value as a method to adjust the actual (in the chamber) AFR. If you are closed loop, the O2 is generating crosscounts, and the BLM is between 108 and 160, then the AFR in your combustion chamber is, by definition, stoich for the fuel you're burning (lets call this 14.7:1 for discussion sake) regardless of fuel pressure.

The only way to actually get a richer mixture by adjusting the fuel pressure is to run open loop, so that the closed loop routines won't take out the extra fuel you add. If you raise fuel pressure enough to get to a 124 BLM, then the ECM is just pulling out (124-128)/128 or approx 3.1% fuel negating your fuel pressure increase. You need the BLM and INT to stay put at 128 (by running open loop) to adjust AFR with fuel pressure.

I'm also not sure I'd run an expensive wide band in the exhaust of an engine thats just been started. Lots of nasty oils and solvents and silicones will be burning off, and could damage the sensor.

I'm watching this thread with interest, as I will have exactly the same problem as the original poster when I fire up my rebuild for the first time. I've rebuilt my truck motor with a hotter cam and higher compression aluminium heads with roller rockers (not a roller cam though), and I'm also a bit worried about initial start-up with what I currently have as my 'old' engine tune as a base.

If a bigger cam gives a lower vaccuum, leading to more fuel than necessary, doesn't that simply mean that the idle will be higher than it should be? After all, rpms is simply a product of the fuel (and air) supplied. Or does the ECM try to 'fight itself' as it thinks the idle is too high? Which would do what? An oscillating idle, or what? Why would 'excess' fuel wash the cylinder bores, and not simply produce a higher (than ideal) idle?

All help appreciated!

Quote: If you are closed loop, the O2 is generating crosscounts, and the BLM is between 108 and 160.

That of course is correct. I am assuming initially it may not be between 108-160. it would be fortunate if it was close but it most likely will not be. i was in same situation just not a brand new motor. modded engine, initially stock. i did not datalog. just upped fuel pressure to get it to run decently and break in cam. i had no EFI tuning skills. soon i realized it was insufficient as far as a tune goes and learned to tune.

so to get it at a reasonable A/F without a WB, one can use the NB sensor. consider it a tool to get engine at stoich for break in. i was wrong on the 14.0/1 i should have said 14.7/1. placing it OL one could only use exhaust smell or plug checks one woulld have no reference to actual A/F. yes FP would affect the A/F in OL but you would have little idea where you are other than very lean vs very rich. if you see 120-138 on BLM in log after changing FP i would suggest that would be where you want to be. OR read the voltage of the 02 sensor and adjust FP till you see crosscounts around .450.

again the change of FP is temporary to allow break in.

I guess in a way we're saying the same thing.

I would still disable closed loop during break-in. You have enough things to watch over and monitor during those first 20 minutes, to worry about what the ECM is going to do when it goes closed loop. The most important thing is keeping the engine running so that the cam and lifters can break in. Mess up and you're doing a cam swap after pumping a lobe or two worth of metal through your new engine.

Disabling closed loop also will allow you to make gross adjustments to AFR with an AFPR if necessary during break-in (such as observing the headers glowing and knowing you're way too lean, or a lot of black smoke out the exhaust meaning you're way too rich). Beyond that, it doesn't matter so much if you're at 13:1 or 14:1.

This is how a roller motor is so much easier to deal with. if you fire it up and it's too lean or rich or whatever, then there is no harm in shutting it right back down, fixing the problem, and trying again. A non-roller just won't tolerate this.

Also, if the engine is being ran for the first time, then rest assured you're at 128/128 until you encounter closed loop, because somewhere in the process of the engine swap, the battery has been unhooked and the ECM has lost all it's learned values, so initially it will start at 128/128 with some enrichment thrown in while its open loop.

More fuel will not make things idle higher, it will just idle richer. you need fuel AND air to gain a higher idle, in fact air is pretty much in control of idle rpm so long as the AFR is anywhere near reasonable (15:1 down to 11:1 or so).

I really think most of this is unnecessary for the OP. His cam is mild enough that it's going to be just fine. Account for any gross changes (fuel injector size and engine displacement difference) and it's going to be good to go.

In the meantime, do as grumpy said. start learning how to burn and tune as soon as possible, and this will all be old hat to you when it comes time to tune the new motor.

I guess that is why many say carb it for the breakin.

I just wonder how close the A/F will be during the break in? granted if it flips CL once coolant comes to temp it should be 14.7/1. I am not sure what happens if the VE is so poor that it falls outside of the 108-160 range. maybe it stays OL. i am not sure. I would think he would benefit by "borrowing" one of our members .bin that runs a similar setup so as to get it close so it can run CL and correct fueling. if one knew the underlying fuel tables were "OK" then one could burn an OL .bin that had a bit more fuel in it and that would be great.

if the VE table is so far off that, once in closed loop, going to BLM=108 or BLM=160 is hit, then a check engine light will be set and the AFR will be adjusted no further.

Given the use of a stock profile cam, the VE (and resultant AFR) should be plenty close enough. The cam is what has (by far!) the most control over VE at low RPM's.

no reason to carb on this motor.

I don't want to hijack the thread, but what does anyone have any thoughts about how far out my base 'stock' tune will be out when starting my new motor? The original motor was a 454 TBI truck unit, I'm can't remember the exact original cam specs, but they were very poor, something like 190 duration with 250 lift.

The new motor has high compression aluminium heads, and a hotter cam, 202/210 dur @ .050, .468/.485 lift, 114 deg sep. The 'stock' chip I was running before the rebuild is actually an Edelbrock MFPI upgrade chip, which I think always ran a bit rich.

I *think* the stock 454 truck chip ran in open-loop idle, and from reading this thread it seems I should try to ensure that stays the case. Is the break-in advice to run off an Emulator (e.g. Ostrich) on break ing, and alter the stoich constant (away from 14.7 !?!) in an attempt to get a *real* 14.7 on running?

Cheers

That's still a tiny cam - especially in a big block!! As always, there will be tuning to do, but you should be just fine for initial startup without changing anything. I would not change the stoich constant. Personally, I would not even try running an emulator during a 20 minute cam break-in / first startup. You have much more important things to be paying attention to - leaks, overheating, signs of trouble, etc. rather than staring into a computer screen. If you have a friend who can monitor the computer for you, then that's fine, I would just make sure that the stock NBO2 never gets stuck below 400mV (i.e., you don't want to go lean).

Just my opinion, though, others may differ!

If the motor did go too lean, what then? Shut off, and do what, burn another chip?

depends on how bad it gets. If your headers are glowing and you're about to melt the exhaust valves, then screw the cam and shut it down. flat tappet cams are cheap, motors aren't. often you can get lucky with a shutdown during the break-in and not hurt anything. I'd want to be running a good oil additive (like GM's EOS) designed to help with break-in though...

but back on topic,

so long as you're running open loop, there are a lot of ways you can "hack" things to go richer:

increase fuel pressure
potentiometer in place of the coolant temp sensor
emulator/on the fly tuning (adjust injector constant smaller or BPW higher)

but again, it's just not going to be necessary with a stock profile cam like that.

Now that *is* a good idea, unplug the temp sender plug and wire a simple potentiometer across it, and voila manual control of temp, assuming the stock tables alter fuel delivery enough on temperature changes.

I might just have to think about doing that on start up. Thanks!

With all this in mind I've got a LOT of things swirling through my head.

Options:

1. Borrow carb/manifold/etc
2. Get some retrofit rollers lifters (Comes down to money I guess...)
3. Just let it do its thing on the stock tune...

But it seems like roller lifters would get rid of a LOT of my worries right now AND get me some better, theoretically mre reliable cams...



And for the record, I'm gonna be investing in the EBL for this, I'm not sure if I mentioned that, or if it even matters.

But guys, your help has been invaluable, please, if someone has nything to add, keep it coming, it's a very informative thread for me.

To re-cap a few things we discussed offline and bring others back into the discussion:

The engine InfernalVortex is buliding is a budget first engine, so perhaps the roller cam suggestion is a bit out of line with the goals. A flat tappet cam with a pair of vortec heads would probably be a lot better bang for the buck.

Or a flat tappet cam plus a wide band oxygen sensor, which both keeps this post on topic and is a great learning/tuning tool.

Can anyone comment on whether or not the various crap in the exhaust of an engine that's just been started/broken in would kill a wide band sensor?

*Me too*. The engine I *have* built ready to go in is a flat tappet cam, and I have a WideBand 02 available for use. I would love to know if I should use it on startup as well for the inital 20 min break in.