I bought a used Accel Gen 7 setup to install on a 383 I'm building. Came with dual-sync dizzy and everything needed but a manifold surface temp sensor.

What I'm wondering is if I really need a MST sensor, and how much cam I can get away with before it makes tuning difficult. I've tuned GM ECMs with a stock LT1 cam and stock LA1 cam on custom engines, but nothing radical. I have also never used the Accel DFI setup before.

Here is the cam I'm looking at: http://www.summitracing.com/parts/edl-22015

Going in 11:1 383 with AFR 195 elims.

 

You can get away with out using it but depends on the software. Are there intake air temp based tables for fueling and or timing adjustment? If you zero those out you can run without it but you are at the mercy of the weather on a set tune. If air temp changes there wont be any compensation and you could end up rich or lean.

If its just a matter of buying a sensor and pluggin it in by all means go get one. I assume you mean MAT for air temp not surface temp.

Cam size shouldnt matter with this. I dont know much on the eddy cams but it appears to be a soft lobe for good valvetrain control and longevity but will sacrifice power. You can get similar duration at.050 with less overlap at advertised with a comp xe grind or lunati grind or even gm/crane 847 cam if you want something that big.
I think something like that is a better match to those heads and will offer better overall power and be easiest to tune at idle

 

No, it is manifold surface temp. I read Accel uses a Saturn CTS for it. The tip touches the surface of the runner close to the head and you have to fab a bracket to use it. There is a MAT in the plenum also. Seems redundant to me. Plus, it's ugly.

I compared the Edelbrock to a Comp and you're right. The 294/300adv Comp is 242/248@.050. Won't that drop the vacuum and make MAP tuning more difficult?

http://www.summitracing.com/parts/cca-08-468-8

 

Yea it would, what you would want to see is less advertised vs .050" compared to what you have now. Like 230 deg at .050 would be closer to advertised of 280-282. I am not sure where edelbrock takes its advertised duration measurements from. Comp does .006" tappet lift, crane did it at .004" so their cams look lazy compared to comps but you really need to see all lift points to see how aggressive it is.

Generally with a good head port you can cut back on seat duration and raise lift to turn the rpm range you desire.

A simple 230 deg lobe thats 276-284 deg at advertised and .550-.600" will peak near 6000-6300 rpms and support power to 6600+ depending on lsa and exhaust lobe with those heads. If you want to rev higher i would have gone with 210cc heads . A good single plane efi would like a tighter lsa like 108-111 but that will make idle abit more choppy. 280xfi from comp has worked well on those heads but its alittle hard on the valve train.
Xe version is abit milder and would work good on a 110 lsa and 1.6 rockers.

Never heard of a surface temp sensor and really cant imagine what good that data will do for tuning. You only need to know coolant temps preferably taken at the waterneck on manifold and air intake temps. From the water temp and some idea of air intake temps you can expect manifold surface temps to be inbetween but likely same as or slightly lower than coolant temps.

Try to look in the software and see if there are any tables using that sensor and determine what its trying to control

 

I got the cam for cheap along with a bunch of other stuff, so I will call Edelbrock and see if I can get some more info on it.

I do like a choppy idle, but at the same tame I know the overlap is what messes with the MAP and O2 readings down low.

I spent some time with the Accel software tonight and I'm not overly impressed. There are a couple ECT modifiers, but I do not see anything about the MST other than a switch for on/off.

 

I'd just set it off and dont worry about it

 

There should be a switch in the configuration>system screen. Just shut it off and you will be just fine.

 

I wonder what it uses it for. (the MST).

-- Joe

 

Here's a video of that Edelbrock cam in a 383 with a carb. It looks to me like it wouldn't be too bad to tune.



Wondering what the estimated hp would be with that cam, 11:1 383 and AFR 195 Elims. I can bump lift to .575/.584 with 1.6 rockers. Hoping for 500. Think that is realistic? Or would it need a cam swap?

 

Hi Woody,
Not sure why you elected to come here for answers because most of them are wrong.

Christ I wish people who really don't know would just be quiet. There's enough bad info on the net.

The Accel uses manifold temp, intake air temp and engine coolant temp to better calculate the amount of incoming air. The Accel is the only true VE based system in it's class because of that. Cold air is more dense but warm air moves faster. That's the reason for needing temp info for a more accurate VE measurement. ALL the others are pulse width based, FAST, Holley, Megasquirt, Haltech, Motec, all of them.

Without the MST it will use a value of 100 to calculate airflow. And no Orr89 it doesn't effect the tune to make it go rich or lean. There are seperate temp tables for that. Intake air temp vs a calculated mass air amount are two different things. Plus the Accel is one of the few that has a seperate barometer in the box, that's why it's water resistant, not water tight.

And you can run as big of a cam as you like. Put whatever cam in it that you would if you were using a carburetor, maybe even bigger/more radical if you want.
To adjust it, when it's idling just go to "Acceleration Threshold" and raise the number a few counts above what you see flashing on the screen. It's like an adjustable power valve. It'll idle smooth as glass with 6" of vacuum if set right. Then you can use the "Idle Spark compensation table" to further smooth it from there.

If you're not seeing all of the tables then you probably don't have a Pro key. They did that on purpose. Some screens operate behind the scenes until you need them and more importantly know what to do with them.

And I'd put the Accel software up against anything, plus it has more transient fueling tables (drivability) than anybody, anybody. I'm helping another gentleman with a FAST XFI 2.0 system right now and that software ain't anything special.

Yes I'm an Accel dealer, email me again if you need any further info.

 

Hah

Agreed.

We know why it needs an temp sensor, we're curious why it uses two.

Since you obviously know everything there is about EFI, could you please describe the algorithm Accel uses to caculate VE?

Megasquirt makes an injector pulsewidth calcualtion based on Ideal Gas Law (which I'd assume most systems use)

P = VE * MAP (i.e. the pressure in the cylinder in kPa),
V = CYL_DISP = the displacement of one cylinder (in liters),
R = 8.3143510 J/mol K,
and T = (IAT-32)* 5/9 + 273 to convert IAT from °Fahrenheit to Kelvin.

Now, On ms3 extra there is a "mat vs iat" correction table. I'm not using an MS3, but I'm assuming it's logic is somewhat similar to why the Accel has both sensors.

Well, not that it is overly useful, but I could add a 2nd map if I wanted to to constantly read baro. Why??

Haha. An idle spark compensation table? Thank god, the OEM didn't start using those until jeez, at least the early 80s.

At least you give us the disclaimer at the end of your posts so we know why your so hot for Accel.

-- Joe

 

I'm not going to get into a pissin match here, so I'll just give the facts.

Apparently you didn't pick up on the fact that Woody and I spoke prior to this post.
And I've already explained why they use multiple sensors, did you miss that?

Accel still holds numerous patents, one of which is the way it fires the injector, and the formula they use to calculate airflow are both very guarded secrets.
How many patents does MS own?, Holley? FAST? Motec? Haltech?

Why a second baro/MAP? Simple, try driving up or down a mountain and then tell me you wouldn't want one then.

While I'm certainly not the best I can hold my own with EFI. But I'll tell you what, why don't you do a search on EFI sites as well as lateral G. Type in cutlassefi or supremeefi and see what I've done via the internet. I've nailed tunes from my chair, FAST, Accel, MSD/Big Stuff3, how about you? How many have you nailed that way?

The guy I'm currently helping with the XFI paid someone for 8 hours on a dyno, 8 hours! And guess what, he can hardly drive it. His "tuner" missed the boat but sold him a boatload of lies.
My point? There are too many people out there who think they know what they're doing, but they really don't, they're one dimensional tuners. Which one are you? I'd like nothing better than to have an intelligent conversation with you, believe me.

Have a nice holiday season everyone!

 

Correct but thats not what i was talking about. I didnt know accel used manifold surface temps for ve and i still dont see the advantage in that but i thought he meant mat, which is why i asked if thats what he meant. If you zero out mat tables used for compensation your tune can change with weather. Baro table would help correct that tho. Not sure why you think this thread is full of bad information

I am curious tho if you tuned for MST vs without, what difference will you notice? I dont think it would make any hp/tq difference but id like to see data on that.

 

So what you are saying is, Accel DFI is the best thing in the world, even though you don't know how it actually works because it's a guarded secret?

No idea. I have patents too, but what does that have to do with the discussion at hand?

So for the single application of an extended run time up a mountain ? Ok.

I don't care. On this forum all you have proven is your a good salesman, and your product is Accel. When asked an actual technical question you back away from it. You like Accel, I get it. But if the extent of your knowledge is the user interface, and you don't actually understand the logic I'm afraid your opinion is not of great value to me.

I have no use for Accel, Fast, or Big stuff 3 (the order in of product development, from his first and most archaic to his most recent and innovative) because it's closed source and you are stuck with the logic and features as sold. Prom tuning interested me for a number of years because of patches, hacks, etc. I got into Megasquirt because of the well written C code and documentation on the forums makes it very easy to make logical changes and add features. It still lacks some things that the OEM code had such as a true vss based throttle follower, at least in v1 and v2, v3 now has one, but none of the aftermarket do by design. (probably mainly due to NHRA rules against monitoring wheel speed).

Dyno? I've never tuned a car on a dyno. We don't race dynos, and we sure as heck don't drive them to work.

I'm not a "Tuner". Tuning a car is like programming a VCR.

But in all seriousness, if your experience is strictly from a user point of view, and you don't actually know how the code works, how can you really discuss this? Don't you want to know the logic behind the click?

You too!

-- Joe

 

From what I got out of his post, was that the pw was derrived from some calculation that uses MST, IAT, CTS, and MAP.

In reality, it probably uses the same ve calc everyone does, but "blends" the T from the MST and IAT. There are lots of theories running around the tuning sites of the air density changing when it hits the hot heads, valves, etc and using a "mat compensation table" to adjust your temperature variable for your ideal gas law fuel calc.

At the end of the day, who cares? Do you really need to know that at an intersecting cell that 75.4% ve is 100% spot on? Software can make all the barometric and environmental "guesses" to correct the injector pw it wants, but in reality (in closed loop) the o2 sensor has the final say.

Speaking of which, does Accel DFI use closed loop AFR tables? Or is it strictly ve based with a set stoich feedback loop like the stock delco stuff?

-- Joe

 

O.K. The Accel uses the IAT, ECT and MST to calculate airflow thru the engine, more like a mass air system than a speed density. And what's it matter if I don't know the secret? So because you know how your system works that automatically makes you a qualified tuner? I can shoot holes in that all day.
No one knows the formula except probably John Meany and Joe Allameddine, but I do know how to tune EFI better than most. I know that because I've fixed alot of other peoples goofs. I do other systems too, and I've had least 1 MS owner buy an Accel because it didn't run they way he expected. He complained about the exact same things you're praising. I guess they're not for everyone, that's why we all have a choice.

The Accel will run in closed or open loop. You can view any table in either configuration. It will show the correction needed but won't actually do it till activated. The numbers in the VE table represent the amount of air and consequently fuel moving thru the engine. They will change as your desired air/fuel ratio changes.

And fire up your MS, FAST or whatever. Watch your correction table, it'll change as the engine warms to operating temp even after cold start has shut off.
By using the IAT vs VE and ECT vs VE graphs along with Temp vs VE you can keep that correction at or near 0 throughout fire up to operating temp and along with the baro and available baro correction tables, from sea level to 5000'. That's what a true VE system will do.

And by the way I said it was the only one in this class that was a true VE, that just the fact. I never said it was the best in the world, please show me where I said that. Yes there are better EFI systems out there, PI and a host of others. But they're 3 to 4 times the money for just the ECM's, not to mention Bosch that goes for around 50K.
However none of them are any good if you don't know how to tune them correctly and to their full potential.

 

This is what I was getting at. Depending where you put the sensor there will still be changes in the air temp as it moves along. What if its a single plane intake and the sensor is on the front runners closest to where coolant water passes thru the front?
What if its in the rear where no coolant flows thru the engine manifold? I would think the temps across the board would have some variance. Maybe small but still something to think about. I havent really measured my temps, I know my intake gets hot on the surface but never measured for variances.

Oh well there are some great running cars without systems like that so again whats the point. Point of this thread was Is a MST crucial to operation? Looks like its not

 

To some degree that's true. It's like anything, are you happy with good or good enough?

Thank you

 

True, dont let good enought get in the way of Best

For a 500 hp n/a car on the street? I dont think you need to get too complicated.

My old 383 was AFR 195's eliminators #1040's, 11 to 1, cam was 230/245 .603/.613 on a 109 lsa. Tuned just fine. I got tons of vids of it on the youtube LOPEY but drove like a honda accord. Very docile until you hammered it. All tuned on stock ECM and MAF sensor from 89

11.4's at 118-119mph in summer air. Would have had a chance at high 10's with more converter, gear, and cold sealevel air in winter. 400whp on a hot dyno day on last pull.

So your cam will tune nice and make decent power and likely give some good valvetrain life. My cam was pretty aggressive with the high lift.