CAM LOBE SEP & EFI??

Guys, I've always used cams with relatively tight lobe separation values in my hot rods, and been very happy with the performance in every case. It's my personal choice, so let's not get off track and argue about it.

Now, I am just learning about EFI as it relates to hot rod engines. One thing that constantly comes up is "You can't run tight LSA's with EFI." I need help with that. Now please, I fully understand what tight LSA's do to idle quality and engine vacuum.

But here's my main, big, question. Why can't we do away with the IAC, and maybe even closed loop idle if necessary, and just tune the EFI for a suitable idle just the same as we would a carburetor, and be able to run a lopey cam with a tight LSA?? Why, exactly, is it said you can't use a tight LSA with EFI?? What, precisely, prevents it?? If is only the luxury of IAC control, or closed loop idle, I would gladly do without those things. I don't care for computer controlled idle speed on a hot rod anyway!

I will re-phrase the question. I can easily tune a carb to work just fine with a, say, 108 lobe sep cam. What would I have to do to accomplish the same with EFI??

Thanks!!
Vettepilot

whoever told you that you cant run whatever lobe sep or lift or whatever cam you want just can't tune worth a crap.

the challenge is with EFI you have a CONTROL LOOP. this could be fuel or idle target or whatever. it could be an open loop (you say 'we are doing this' and keep saying it) or a closed loop (you say 'we are doing this' and a sensor says 'we actually did this' and then you say 'ok lets try this instead')

so you need to adjust your control loop to MINIMIZE MODULATION

i have tuned everything from RV peanut cams with an incredibly smooth output, to insane cams which defy all logic and seem only be to show off. none of them have left my care running worse than a carb would.

yes the extreme cams require disabling an IAC sometimes or timing idle compensation sometimes.

sometimes a guy with a peanut cam wants it to idle like a crazy cam too. i have no problem doing that either.

Thanks for the reply!

Well, let's take a hypothetical scenario. I'm brainstorming an engine that I might actually do. A 454 big block Chevy with a "Thumpr" cam and FITech TBI. The cam is 227/241 with 107 lsa.

What would be entailed in making it run? How would you tune it?

Presently, that engine has one of Comp Cams biggest 4x4 cams in it. It has 111 lsa, but still has a very lopey idle because the duration is 234/244. What would it take to tune FITech TBI for it?

You mentioned what all you could do. What can I, an EFI newbie, accomplish??

;~)

Thanks again,
Vettepilot

Some of the cam advice may be left over from the old days. Slower processors and early code didn't play as well with a big cam. Rapid intake pressure spikes would trigger acceleration enrichment and rapid timing changes, rich exhaust would drive short term and long term fuel toward the lean extreme, engine speed would start hunting, and it would create a cycle that was really tough to control. Today's controllers are so advanced that it's a very different game.

A properly tuned ecm does a great job of eliminating all sorts of compromises we had to make with carburetors. Increasing idle speed, advancing timing at idle, running a loose converter so the car didn't surge at a stop light, stinking rich exhaust are much less common these days. Can you make the system behave like a carbureted engine? Sure. If you're comfortable with carbureted engine behavior by all means, install a computer and tune it to do the same job.

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You mentioned what all you could do. What can I, an EFI newbie, accomplish??

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More than anything, the answer depends on your patience and your expectations for engine behavior. I think you could probably dial in many of the spark and fuel settings rather quickly and make it so you can drive it without blowing up the engine. What usually takes time is driveability around town, start up, and idle. That process usually requires multiple drives, datalogging, change calibration, and drive more.

Ok, thanks.

One thing I hate about IAC is how slow it is to return to low idle. (On all cars with EFI.) I know it's to resist stalling, but I like an engine to crisply rev, then instantly return to idle.

No, I don't want to tune to be just like a carb. I just want to be able to run cams with moderate overall timing, but a tight LSA, with EFI.

Vettepilot

On the later OBD 2 cars this is called throttle follower, it mimics the old dash pots on carbureted vehicle. You can adjust it for more or less delay

if your IAC is too slow, throttle follower doesn't fix it or settings not available, and you want your idle to drop quickly, you can play with your timing advance vs idle error settings or whatever it's called in your definition. actually that's a very powerful setting that can increase or decrease cam lope and other things. another way to roll is you can close off the IAC passage by an aribtrary amount and then muck with your throttle plate. that way the IAC only makes fine adjustments and the throttle plate does its thing. finally on race cars i have deleted the IAC and just set a slightly higher idle that runs a bit crappy for the first few seconds but cleans up real quick as startup enrichment tapers off.

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Originally Posted by 1project2many

Some of the cam advice may be left over from the old days. Slower processors and early code didn't play as well with a big cam. Rapid intake pressure spikes would trigger acceleration enrichment and rapid timing changes, rich exhaust would drive short term and long term fuel toward the lean extreme, engine speed would start hunting, and it would create a cycle

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with the old slow ECMS i had usually run open loop, disable AE, lock down timing outside of operating range, and just do my best. results have been really good and 'better than a carb n points' but definitely not economical, but it's the customers fault for not wanting to swap to an ECM that doesn't suck. 'not playing well' i think was just people not doing a good job, sometimes doing a good job is simplifying a crappy system until it behaves

Thanks guys.

Is Megasquirt any good?

But then I'm not sure what I would use for the TBI itself...

Vettepilot

most old 160 baud slow ass old tbi ECMs (which are probably older than the original nintendo entertainment system and have about the same processing power) have a newer 8192 baud cousin that is quite easy to re-pin for and better to tune. that'd be much easier than a megasquirt which is a total do-over.

you can really use most any TBI with most any TBI ECM if you are handy enough

edit: but to answer your original question, yeah, megasquirt is just great. really nice product. tuned 2 of them now, difficulty medium but rewards are great

Do some research on the thumper cams, they are noted for being a POS.

Look online and you will find they are known for being all sound and no go, along with no vacuum at idle, thus no power brakes.

If your looking for the classic rumpity rump rump sound, there are way better cams that will give it and go.

https://www.chevelles.com/threads/thumpr-cam.1164438/

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One thing I hate about IAC is how slow it is to return to low idle. (On all cars with EFI.) I know it's to resist stalling, but I like an engine to crisply rev, then instantly return to idle.

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So this is a part of tuning. Three factors affect idle speed. Spark advance, fueling, and air intake. For older ECM's the timing affected idle fastest, fuel next, and IAC last. Many of the OE vehicles are programmed to decelerate more slowly. Both emissions and OE needing "vanilla" tuning play a part in that. Newer ecm systems, and systems with electronic throttle control, can drive IAC and idle speed changes very quickly.

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with the old slow ECMS i had usually run open loop, disable AE, lock down timing outside of operating range, and just do my best.

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When I built the 302 in my '57 in 93, I was told the 350 hp 327 copy cam I was running was too big. I was using an 83 Camaro ECM back then and my only paid for tune from Turbo City ran like poop in OL. But CL wasn't bad, all things considering. Very wide INT and BL limits combined with mild VE changes were all that was done. I was very disappointed with that tune considering I worked for GM dealer and felt the vendor had promised it would run well. After learning to tune I had to give the tuner props as he worked entirely from paper specs and only got one shot to get it right.

I used to be a hell of an engine builder and tuner. I also used to be pretty hot at learning new tech.

But now, at 70, learning all this EFI tuning stuff is sounding more daunting than I want to take on; maybe more than I CAN take on.

Maybe a newer, self learning EFI setup is how I should go... (And whatever dam cam it will support.)

???

Vettepilot

let be frank even though my name is steve

don't be ridiculous.

stop saying "used to be" like someone can just up and lose a learned trade. that's not how it works

i know a bit about the brain and about learning

i realize a 70 year old brain is not adept at learning drastically different things than it has already been primed in. but the work and satisfaction of meeting
challenges like this will probably extend your life

if you weren't curious, you wouldn't be here asking about it man you would just hire someone.

it is a steep learning curve but you learning enough to do this on your own (with our help) could be the highlight of the next few years of your life. self tuning aftermarket systems help but always require tweaking.

if you reach an impass, and you give us logs and your current tune, we will help. that's why mark made this place, to help people out

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Originally Posted by steveo

let be frank even though my name is steve

don't be ridiculous.

stop saying "used to be" like someone can just up and lose a learned trade. that's not how it works

i know a bit about the brain and about learning

i realize a 70 year old brain is not adept at learning drastically different things than it has already been primed in. but the work and satisfaction of meeting
challenges like this will probably extend your life

if you weren't curious, you wouldn't be here asking about it man you would just hire someone.

it is a steep learning curve but you learning enough to do this on your own (with our help) could be the highlight of the next few years of your life. self tuning aftermarket systems help but always require tweaking.

if you reach an impass, and you give us logs and your current tune, we will help. that's why mark made this place, to help people out

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Well said Steve. Don't give up VettePilot. There are times we all need someone "hands on" with a project. If you put your location in your bio, there maybe someone local, or at least a recommendation for a local mechanic.

Good luck.

Jeff

Ok, thanks guys.

Anyone have anything to say about the FITECH offerings? Budget is a really tough consideration here, and the much vaunted Holley systems are so expensive.

A while back, I actually bought a "Stimulator" kit, which is the first step in getting your feet wet with Megasquirt. Have not built it yet.

Then, I suppose, there's the option of a modified OEM GM system.

I don't need nor want a system that makes me breakfast and tucks me in at night. Just something as simple and inexpensive as possible.

Can GM OBD1 be easily set up for tuneability, or is that stuff not available anymore?

Thanks for the encouragement!

Vettepilot

Separate question.

There's "I need a touch more "accelerator pump" and want to fatten up the midrange a touch."

Then there's "I'll adjust VE and change some Bins and tweak the trims."

I'm WAY in the first camp. Is that gonna fly??

Note: I'm not totally "cave man." I have a wideband AFR setup.

Vettepilot

you can adjust whatever you want. if you don't adjust the VE table or other airflow parameters what's going to happen is the ECM will just trim the fuel to be correct. edit: when i say correct, i mean roughly correct.

adjusting VE is not a scary thing

all it is, is a grid of numbers. higher number more fuel. lower number less fuel.

one axis of the grid is load. one is engine speed.

so if you increase the number by 5% at a certain load and speed in this table, you get 5% more fuel there.

it's not only more precise than tuning a carb, it's way way easier.

also the old TBI ecms are great for caveman tuning. the VE tables are tiny and imprecise, but they work.

if you have a wideband and you learn to log it, adjusting your VE table so all your fueling is correct will be a very very simple and quick task

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Originally Posted by Vettepilot

Ok, thanks guys.

Anyone have anything to say about the FITECH offerings? Budget is a really tough consideration here, and the much vaunted Holley systems are so expensive

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if these are the parameters:

- throttle body type injection
- budget conscious
- good learning project
- fairly easy to tune
- guys on this forum help you

you want a modified OEM GM system FOR SURE.

what you want for a TBI system is an ECM that has 8192 baud data logging. the older 160 baud ones might frustrate you a bit.

of course with ECMs of that age on a budget, you are going to have to open them, pop chips in and out, and program them.

that said, megasquirt is totally great too.

try to stick with stuff made by hobbyists. holley, fitech, those commercial guys, if you buy into them, you rely on them for support, and a lot of them are business men rather than basement car hackers whereas

So, how easy is it to burn your own chips?? The little reading I did on it made it seem rather daunting to get set up for that...

Then, converting OBD1 to being programmable. Again, over my head.

Sorry guys.

Vettepilot

stop being sorry. i was in the place you are in once and so was everyone else here. that's why you're here.
burning a chip is super easy. you buy a prom programmer on ebay or whatever they are cheap. you put the chip in it and read it modify the bin and then write it back. if you have enough computer skills to post on this forum you have enough computer skills to program a chip.
if you replace the chip with a larger one you have to 'offset' the program. this is also pretty easy.

oh and really old chips are this really cool thing called 'uv erase'
so if you have one of those chips you take the sticker off the 'uv window' and leave it hanging around on your window sill for a while and put the sticker back on
i tuned tons of cars with those UV chips

Well, ok. Let's say that at least for one of my vehicles, I stay with it's original OBD1 TBI system, but want to tune it for a better cam, heads, and exhaust. It's a 1994 GMC K1500 5.7 4x4. I already rebuilt the throttle body, and did all the mods to the throttle body itself to improve it for performance. Use will be mild everyday with about 10% offroad. What, exactly do I need to tune it and where do I start?

Second vehicle. 1987 Corvette. I am installing a hot 454 big block, and would like TBI. Big cam, many other engine mods. How to TBI/EFI that one??

Note: I do have an ALDL cable, a laptop, a tablet, and TunerPro and "ALDLDroid".

Also, yesterday I scored a "7427" ECM along with it's wiring connectors. Useful? Also, out of the Vette, I will have it's original ECM multiport 'puter once the engine swap happens.

So many decisions!!

:~(

Vettepilot

tune your truck first

you should be able to open the ecm, pop the chip out, and put it in a chip reader if you wanted to pull the stock calibration off, then tune it with tunerpro, and write the program back to the chip.

it's not the most elegant way like newer flash or realtime ecms but it will get the job done cheap

im pretty sure your truck would already have a 7427 ecm so now you have a spare if you really mess something up

i will tell you tuning trucks that are no longer being used as a truck (i.e. not hauling yards of gravel or towing big trailers) can be very rewarding. the stock tunes are very very limp in terms of both spark and fuel, because if you're driving up a big hill with a ton of stuff in tow, they don't want it to blow up. there is TONS of power on the table.

so a tune for a truck like that would be something like:

- drive around and get a datalog with your aldl cable and tunerpro, maybe bring a wideband with you too. you can use the logs to see how close the stock fueling tables are, and how much you'll need to change them.

- make a first attempt to correct fueling by making some small changes to your VE table, so when you load your new tune you can datalog again and probably get it close to good on the second try.

- spend some time on your spark table. if you have a different cam than stock, you want the 'under load' part of your spark table to be a bit different. timing should advance towards the torque peak of the cam then level off, well, you have a different cam. you can also add quite a bit of timing advance everywhere on the table in general if your fuel quality is good and you aren't towing.

- tune power enrichment fuel. for something not hauling heavy loads, with consistent fuel, you will find peak power near 13:1. new tuner probably target like 12.5:1 or 12.8:1 or something. the wideband will really help with that.

- load your new tune and go and data log again. this time you're checking not just for fuel trims (to see how your fueling is doing) but also watching your wideband to make sure when you floor it, your AFR stays in the safe zone. you're also watching for knock to see places where you might have gone too far on your timing table

- now go back and make a few more changes based on what you see in the logs

analyzing logs can be a bit daunting, i have written software that helps A LOT, can teach you to use it. trimalyzer is pretty good for a beginner, i wrote it because i was kinda tired of teaching new tuners how to analyze logs.

Ok, got it. Except for the chip reader and writer. What exactly do I need to do that?

I would love to be able to tune this. Buying a chip for several hundred dollars that might work ok, and would need changed (and bought!) yet again if I change something on the engine, never seemed like a good process to me.

Is it worth getting into whatever the setup is that programs to the computer in real time, whatever that's called??

Thanks for your info and patience with me. Outside of EFI, it's usually me that does the helping in various forums!

;~)

Vettepilot

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Originally Posted by Vettepilot

Separate question.

There's "I need a touch more "accelerator pump" and want to fatten up the midrange a touch."

Then there's "I'll adjust VE and change some Bins and tweak the trims."

I'm WAY in the first camp. Is that gonna fly??

Note: I'm not totally "cave man." I have a wideband AFR setup.

Vettepilot

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Before Megasquirt existed, I met Bruce Bowling at a get together in Ohio. Bruce is a really sharp guy. We were talking about using tuning software. I told Bruce that the biggest hurdle for folks coming from the hotrod world was turning jet changes and accelerator pump shot into VE tables and AE duration. Tools that represent the hotrod way of tuning might be helpful... an "everywhere" fuel adjustment could represents jet changes, a dial for idle mixture, a choke spring tension adjustment for cold starts, a pair of accelerator pump sliders to tailor pump shot, would really help transition between mechanical things and digital bits. I'd even said that it would be really cool to be able to click on pictures of a digital carburetor and distributor to select the changes you want to make. I've never used MS but I believe their software has some of that functionality built in.

I came from the world of carburetors and distributors, and I started modifying EFI when people outside GM had very little clue how GM's software worked. We've had folks here in their '80s learning how to tune and swap efi bits successfully. I think you can get this. I wonder if coming from "I can do this easily with a carb" is going to be a big source of frustration? But maybe this is more like learning a new language. And the new language has more words to describe things so you will be able to understand what the engine wants much better.

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So, how easy is it to burn your own chips?? The little reading I did on it made it seem rather daunting to get set up for that...

Then, converting OBD1 to being programmable. Again, over my head.

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More detail to go with steveo's posts.

OBD1 is already programmable. Remember when we would tape over the small hole on the back of a cassette so we could put our music there instead of some craptistic band? This is the same thing. There's a chip inside the ecm that's programmed with lounge music. You can change the tune.

Tools you will need:
Eprom burner with software
Eprom eraser

You will also want a way to talk with the ecm to see how the engine is doing. The ecm is able to provide clues to what the engine wants and what it likes. You need software that can interpret the ecm's communication. Most folks use Tunerpro.

You will also want a tool to view and edit the data in the chip. Again, Tunerpro can do the job.

This is the bare minimum. Upgrades can include switching from EPROM to electronically erasable chips, adapters to allow quick and easy chip removal, and an emulator so you can make changes to your calibration while you're driving.

You have a '94 truck already? Automatic equipped trucks have a 7427 or similar ecm already. Those are a great choice for an EFI project. I agree with steveo. Start tuning the '94 to get used to the tools.

as a poor man i bought a cheap Chinese chip programmer
its tuned hundreds of chips now no problem
the sun can function as a free uv eraser in a pinch. it puts out tons of uv

open the lid on that 7427 you bought and have a look

That was me using improper language when I said "programmable". I know it's actually programmable via the chip. What I meant was actually programming in real time using an emulator. But maybe I should take "baby steps"...

Ok, back to burning chips. Do you have a recommendation on what to buy to erase and burn chips, and where to get it?? If it's truly only UV to erase, I could rig up a "black light" in a reflective box if that would work/suffice. I do my daily work on Android tablets. However I do have a laptop computer with Windows 7, TunerPro, and an ALDL to USB cable.

Actually, just for looking, I also have ALDLDroid to read the data stream on my tablet too, though I've not yet used that.

My truck is a 1994 Z71, but I believe the ECM is not 7427. I'll check when I get home tomorrow night. In any case, I'll have an extra chip to play with, right?

Vettepilot

I have a Willem GQ-4X that seems to work well.

Eprom erase frequency is 253.7nm. You'll want a light that produces UV-C for best results.