0ski_dwn_it

Ok I have been holding off on posting this for quiet a while now and feel that I have beatin this test to death with no hope for improvements to sway my decision. I am posting this information for other to use as reference and to make their own conclusions from. I don't intend to make it a pizzing match, and if you don't agree with my finding, then politely post your concerns or comments, but be prepared with supporting evidence/testing of your own to refute others speculations.

I built the 434 in my signiture this winter, and started off the season at the track with some pretty decent times. My first time out I had some oil problems and called it an early day. Some of you might recall my visit to Mason Dixon. I followed up that visit with an invitation to a private track rental and after some tweaking on the MAF system was able to run 10.7@127.5MPH in about 2500 DA weather. The car was hitting 101MPH in the 1/8mile, and was pulling a mere 1.54-1.57 60' time. I raced again at Keystone Raceway, side by side with Corky, Jim and a few others that we race with. My car ran low 10.80s all day in about 2500-3000 DA weather. Corky car was with a few hundreths of me and I was totally convinced with these huge flowin heads and intake that these motors were being choked off my the MAF finally.

I took the plunge and contracted a fellow forum member to build me a jumper harness that would leave my stock harness untouched and would utilize the jumoer harness to make the necessary changed to make the 730 SD computer work. I got the harness and all necessary hardware. Hooked it up and had zero problems with it. It worked just as we intended. I tuned the part throttle with a few hours with the romulator and logging laptop.

That following weekend Dad and I went to another Test and Tune to see what this thing would run. The car I thought would hit 50s in the weather ~2000-2500 DA. I was baffled to see that it would barely mustar a 10.9. After several run, reading the logged WB, my stock 02s, and plugs the car ran 10.9s@124. I was pretty disapointed to say the least. Corky was racing the same day at another track and I was dumbfounded to hear that he was hitting 10.6s! Glad for him, but very discouraged. We agreed that testing would be best done side by side, so the next day we again traveled 3+ hours to Ohios Dragway 42. There the car ran 11.0X and finally a 10.9. In fairness I did find a bad + wire to my battery that I thought was causing my loss of ET. It picked up a .1sec to give me my 10.9, but that was a far cry from Corky's 10.57@128 sporting a dinasour 870 computer. I was pizzed and frustrated.

I knew the tune was on, the plugs looked great, I played with the timing the previous day more than another possibly could, using the same exact method as I did at the first T&T with the MAF system to dial it in. Hell within 3 runs it was crankin out 127MPH. With the SD system my MPH dropped at the end 3+MPH, and the 1/8 mile is YET to hit 100 again.

Still as much as I wanted to give up, I had over 500 dollars invested in this system that even I thought should easily outdo the MAF on these motors. I wasn't giving up. I made more excuses and thought maybe it was the gearing. So I pulled the rear and installed the 3.45gear set and spool. Went out again to the track, 11.0x with a few 10.9s. Found that my alignment was not real good, so I bladed it on that again. Got the spool fixed and threw in even more gear 3.73s, which I think everyone will agree the motor should like, since I was only going through at 4700 RPM, but shifting at 6300RPM. Got the car computer aligned last Friday and went to race again side by side with Corky, jim and a few others.

Keystone Raceway was the test track, Corky said based on the terrible DA ~3500-4000 he should run a 10.7X@124. As luck would have it in the pitting lanes we paired up for our first run. I was confident as I jokingly said to him, don't feel bad when I leave you in the dust. We lined them up, mind you I put brand new slicks on as well, which should do nothing but help. We ran the cars, corky ran out ahead of me, gaining every so slightly the entire way down till there was about 1 car between us. I knew either he ran an exceptional time, or my car was right where it had been. Got our slips and he ran a 10.77 to my 11.03, both at 124MPH. WTF? :mad His 60' times are better, but not enough to make up that span. Then to boot the other guy, Rich that races there with us earlier in the year I was ~.06 faster through the 1/4 than him, i was running .2sec slower than him. The best I got out of the car all day would have been a 10.95@124. Corky went bottom 10.7s.

So here I stand, out of excuses as to why this SD system has not offered anything even close to my original system. The 60' times are pretty much right in the same exact range as the MAF ones are, and it just doesn't pull as hard. Raced several times with other cars that I had run with earlier in the year and I was always about .2sec behind them now.

Some might say that its the "Tune" I bet to differ with anyone that takes that route. I KNOW that its on as far as anything humanly possible to control. If its changing stuff race to race on its own through corrections and otherwise, well its not a good system to have for bracketracing and dialing in a car as far as I am concerned then.

I was one of the biggest MAF advocates up till I tried the SD system. Then I was 100% for the SD system and getting ip optimized. I said it before even back when that our setups now I thought were exceeding the MAF limits. I however proved myself even wrong with the testing that I have done. Corky car week after week, runs quicker, not by a few hundreths, but tenths, which is HUGE at this level. I tweaked everything imaginable and still it runs slower.

Here are my conclusions.

The SD system is great for part throttle tuning. I was able to get every cell into the 128 range in no time. Which yielded not much an improvement over the already 124-132 BLMs the MAF system did. But yes it was easier to dial in.

The SD system is cleaner under the hood, but that is a matter of opinion.

The MAF outran the SD system at the track in every appearance. Not by a few .0x, but rather .x seconds. Not hardly acceptable in my eyes for the above improvements.

Things I did not like about the SD system is the base idle can't be raised above ~850 RPM, and with a big cam like mine, its not hardly possible, I got around it with the min idle screw, but that might not be acceptable on others cars.

In conclusion, I would say that if your looking for a street driving car that needs a setup, SD is fine, but if your trying to get every ounce of power out of the setup, the MAF is the ticket. I don't have an explination as to why, but Corky results and my first times out with the MAF are pretty tough to agrue with. 10.57@128MPH though a bone stock MAF is pretty stout, in 2000+ DA weather.

And if anyone thinks that even for a second that I did all this just to say that MAF is better, you sadly mistaken. Anyone that knows me, knows if I knew wearing an aluminum foil pointed hat around the pits would gain me a few .0X seconds, then that is what would be on my head. So if this system was capable of running quicker, both Corky and I would be running them, and I would have not wasted a few hundred bucks trying so hard and 1/2 my season getting it dialed in.

Thought I would share this with you all. I am going to give it one last attempt which cost me a few sheckles more to get setup for a final comparison and that is run the SD system as it sits now the next time at the track, then run my 127MPH chip with the MAF and see what it gains. That should put the nails in the coffin for my thoughts on it and should be a good thing for others to gage off of.

Hope you appreciate the testing, there has been a lot of trying to get this system up and optimized. Off the bat with the SD system on the street the car ran fine. Just isn't putting out the numbers on the track that I know its capable of. Even last night I had a conversation with my 3 yr old out in the garage. I asked him what he thought of it all. He crawled up in the car and pointed to his Shreck Doll he insists hangs from my mirror. Maybe hualin that green critter down the track is effecting things.

buzzbomb

Seems to me that you cannot draw conclusions without the final control experiment, putting the MAF back on. There could be other reasons for the performance loss, and your times may not recover when you go back. Just a thought, and we all enjoy reading your exploits

0ski_dwn_it

I agree the final test has to back to back runs with SD => MAF.

But I know the motor is sound as is the drivetrain. The ET loss started immediately after the conversion. Hell my first run off with the MAF with my 406 tune was 11.0X@123, then increased to 127MPH with a few tweaks of the timing.

But yes, your exactly right. It needs to be tested.

Nathan Plemons

I know this is gonna sound like a stupid question, but do you have a wide band O2 sensor to tune with? If not the SD computer could easily be running way out of wack at WOT, whereas the MAF computer would know a lot more about what is going into the engine and wouldn't have to rely on the O2 sensor output as heavily.

I'm sure you know this already, just grasping for straws.

89vette

I'm just getting started with this racing stuff if I ever get time to go back to the track. I switched to SD when I tried tuning my Miniram. Now that I an running a Super ram, I could probably switch back to the MAF. Hell I still have it in the intake system so I am not gaining anything there. Your finindings are very interesting. At WOT there is not much differnce if any between how a SD and MAF control the motor right? They both use the PE vs RPM table. I know with SD you can play with the VE tables so you actual ECM calculated AFR values are close to actual. You can do this by disabling PE and trying to get 128 block learns all the way up.

I may actually switch back to MAF at some point so my mileage figures work. I don't think I am gaining anything using SD with my motor.

kittmaster

To bad there isn't a way to use both at the same time as the 94-96's do. Something to think about????

Chris

Nathan Plemons

I don't think that's entirely correct. The MAF system uses the MAF at WOT to determine how much air is going into the engine, so it can add fuel accordingly. This is part of the reason why MAF cars generally require less tuning after mods than SD cars do.

ANTI VENOM

I will not be able to explain this well, but I have heard that SD can make changes to your WOT fueling, depending on your BLM just prior to going into PE. If your BLM is at 128 prior to dropping the hammer, you should be A OK. If you are sitting on your stall, or rev limiter, maybe your BLM is somewhere other than 128. I don't know the above statement as fact, but I have read it from some that are much more knowledgeable about the ECM's behavior than I.

Not to argue with you, but I still see it as a tuning issue, because the computer is only controlling spark and fuel. I will only mention these as a refresher for you. Another set of eyes so to speak. Can you verify that the timing maps are the same? Is the fuel PW the same at WOT going down the track with both setups? If you datalog your runs, maybe someone else can look over the two for discrepancies. It just doesn't seem logical that the car is tuned the same as the MAF, yet it runs quite abit slower. That is my lame attempt at an arguement for SD.

Can you conclude where you are losing your ET? You said that your 60' is pretty much the same. Maybe that will tell someone who has the experience (you) where your power is down. I am only speculating and trying to offer more suggestions. Good luck!!!

ralph

Jesse, that's great work!!!!

I know you have changed a few things along the way, so the switch back to the MAF with be very interesting. While I could believe there was no gain going to the SD system, I dont see how the SD could actually hurt your performance vs MAF all things equal. But i also can't explain why corky was able to pick up .05sec switching from a 1000cfm TB to a 1300cfm TB when theres a MAF that flows considerably less than both sitting right in front of it. complex creatures, aint they?

Well good luck on the next test.....keep us posted.

tempest

perhaps one explanation could be that, in general, MAP sensors have a slower response time than the MAF. steady state tuning will probably get you great street performance, but in a race you probably have so many transients going on that those steady state calibrations go out the window.

have you toyed with setting up an alpha-N (TPS-RPM) setup for kicks?

just some thoughts to chew on.

vader86

Interesting, I thought the SD would clearly outperform in your particular setup.

89vette

Yes but after 255 gms per second it is not measuring the air anymore.

Dale1990

SD has the same 255gm/sec limit as the MAF. All of the internal calculations are still based in 8-bit. For SD, the computer calculates the gm/sec to figure out the fueling and if you wind up over 255 then you have the same problems as with a MAF setup (or so I have read). I have not jumped into the assembly but it is on my list of things to do.

The real question is whether or not the WB was showing an acceptable A/F for your car. I am guessing it was or you would have mentioned it. This leaves the VE map out.

0ski_dwn_it

Guys. Thanks for all the great comments.....many of you asked or stated very good questions.

Let me try to answer a few:

1. WOT WB data logging (nathan) - Yes as I not only can observe it on the digital dsiplay, but I can also log it through the hack I have that let the WB feed right into the ECM and log on the ease software. That way I can plot both AFRs and RPMs. Also I have the stock 02 as well. So the fuel is a sinch to get dialed in.

2. A question was raised with regards to the BLMS before launch. Yes there are some corrections that can take place. These can also take place with MAF systems, but none of these corrections would result in the ~.2sec loss of power I am seeing. Also I would clearly see it on the WB logs that in these slower runs the AFR was way out of whack. Not the case.

3. How can SD not run as good (Ralph)? That is a question I ask myself daily since putting the system on. But its like I hit a brick wall with since I put it on. Hell I feel that my 406 is not far behind where I am now running. .1-.2 sec is all the faster I am going with all this more motor. My conclusions are and it touches on the next persons question, so I will answer/state them together.

4. Do the logs show the correct timing(which I think is what is going on based on my experiences before with how much the timing (2*) can effect the ETs on my 406 setup. YES the logs show the same or correct timing that I desire to run per run. But there is ALOT to these ECMs that even the best code readers have not uncovered. So its more than possible that even though the displayed timing is exactly what I program it to run, it might not be what the motor is getting. The only way to do that is have a timing light out there on the motor. Or have someone savy enough to setup a logging device that would record the actual timing the motor is seeing. that I have no idea how to do.

Just recently they uncovered the fact/arguement that the SD system has the same exact 255g/sec limit the MAF experiences.....go figure. So I am sure there is alot more happening inside these ECMs than I can program or know.

This bring up my next very interesting point that I have spoken to Corky and Ralph (i believe ) about.

As these computers evolve they are designed at GM not to enhance performance for all intense purposes, but to give BETTER emission control. Therefore the speeds/memory of the computers are enhanced to give more capabilities to cover the increasing demands the goverments/states require of the car fleets. SAmple rates increase and so do the abilities to tweak setting to "optimize" (not in the sense of performance) but emissions.

Now let look at Corkys 870 computer vs my 730. Lightyears ahead mine is. Tons more parameters, and the ability to tweak different parameters is endless in mine comparing the two. Corkys acts more like a "carb" setup, but with more features obviously. I can only imagine that his setup runs exactly what its told to and doesn't have the time or ability to correct. Mine on the other hand might be changing all sorts of parameters. Throw ontop of that the all the items the computer might be looking for in regards to emissions etc, and you can easily see where .2sec might be lost.

To me it makes perfectly good sense. Depends where you sitting I guess as to which system is better.

Ralph you also make another great point. How could Corky pick up ET .06 sec with the 1350 CFM throttle body if there was a restriction. I too added the monster TB, but could not tell exactly how much it needed accuratly cause other things were changed.

I said it back when I was going to do the switch to SD. I think the MAF sytem is a VERY complex and living system (dynamic) and you can't just think of it in a static state (650CFM) there is A LOT more to it than that.

MAYBE the SD system is flowing much more air, but these possible corrections to say timing are spoiling the results??? The point I am trying to make is I think I am as capable as another you throw against me to tune one of these systems, and it netted me zero in the way of ET. Most of us are not NASA engineers or have the time to sort out the happenings of the ECM, and correct/account for it to make it better. I expect the system, as in the case with the 85ECMs to be stupid and do exactly what I tell it to.

When you think of some of the 85 cars we have here....there are some DAMN fast ones.....Ralphs 350 and 406, corkys 406 and 434, Beaches 383, Jims 383, and I am sure there are some other ones that I might have missed.

I am seriously considering going to the 870 ECM. I know its against the grain, but my gut tells me what I am right with the newer ECMs being a little too smart for their own good. When I program it to do something one shouldn't have to worry about it changing on you. My timing is set at 32* I expect it to run 32* just like a carb setup.

Again one much understand that this entire conversation doesn't apply to street cars. I would not tell you .1sec though the 1/4 difference if my life depended on it. Most of the time my car feels slower, and it turns a faster time. So for the street the systems are equal in my mind, with the SD maybe ahead because of its ability to get 128 easier. But again, even with my radical system, I have not a single problem dialing in the MAF to a respectable tune on the highway.

Pretty neat stuff. Alot of speculation that might be getting added, but its the only way I can describe it. As I have spoke about the other tuner that copied or 406 motors last year with the Miniram and SD system. he was always about .2sec behind us. This year he's running 11.3-11.4s, we would have been running teens and twenties with ours in similiar weather. This is his second full year of tuning his setup also.

I also added several other items as I mentioned along the way that should have really increased the ETs. Like going from a HV oil pump to a Standard Volume....that should have increased power....Better Tires, More gears, Lighter rear rotating assembly (spool), lost a few pound myself coming off my winter fur.

mike 1985

When I program it to do something one shouldn't have to worry about it changing on you. My timing is set at 32* I expect it to run 32* just like a carb setup.

Man, i commend you for working your tail off, and i feel for you for no gains. I'm also curious as to what if any the gear change will make. My friends 68 Camaro which has a 468 with a 6-71 was running the stock 12 bolt with 3.08 gear. the car was running 10.10. Due to worrying the rear would break, he added a spool, axles and 3.73 gears....to run 10.20's all day long with the 60' changing from 1.45 (3.08) to 1.50-1.52 with the (3.73)

I know you hate to hear this ...but can you try a 1000 HP carb ? and a reg dist ?

91tpi-zf

Why not just take both systems to a chassis Dyno and figure out what each one likes? That would be the best place to prove the power output between the two systems. Same dyno, same day, with the only change being the MAF vs. SD system

89vette

[QUOTE=Professor]SD has the same 255gm/sec limit as the MAF. All of the internal calculations are still based in 8-bit. For SD, the computer calculates the gm/sec to figure out the fueling and if you wind up over 255 then you have the same problems as with a MAF setup (or so I have read). I have not jumped into the assembly but it is on my list of things to do.

This is the first I have heard of this but I'm not saying you are wrong. With the SD the VE tables extend to 5600. Would this then become the 255 limit? With a big motor and a MAF you hit 255gms sec at about 4000 RPM (if I can remember right). SD on my car made the throttle response crisper but other than that no change. It made a big change with the Miniram mainly due to a problem with tip in. The faster reaction on the SD allowed me to tune it out for the most part.

0ski_dwn_it

Mike.

I can see that you friend would loose some ET since his 60' times changed a bunch. But mine remained in the same interval. ~1.52-1.57 depending on track and prep. I always break down my slips into intervals. With the MAF it hit 3.85sec in the last half. With SD where it should be breathing better, its best YTD is 3.95sec, a full tenth off pace. Corky car kills mine through every interval, where mine at the beginning of the year was nearly the same or better. When we first went out mine was actually quicker, then he changed to bigger headers and he shot out ahead, but by then I was onto the SD setup crawlin like a turtle.

91TPI- That is what I am saying with comparing the car to other cars that I raced along side of at the years begining. These guys KNOW their cars like the back of their hands for this bracket racing, you have to know to do any good at all competing. When my car went fast than Rich's at the years begining on every run, then later with him changing nothing and running the same times in the same weather, mine is slower by nearly .2sec, SOMETHING is not right.

There is nothing more that can be done to the tune to optimize what is happening. If the system is making changes based on incoming air temps etc and compensating spark advance you would be chasing your tail for the next 10 years trying to pin it down. The car is running strong, 10s is nothing to sneeze at, but I know its not running no where near what it would be looking at Corky's ETs. That is one reason why the two of us build very similiar setups each year, so we can accurately gage off one another. They usually run within hundreths of one another as they did at the years start. NOT TENTHS

This is the stuff that makes racing a hobby. Learning, experimenting, getting frustrated, but having the overall resolve to keep moving forward.

I am sure that given an unlimited amount of time and money better testing could be done. But my gut tells me I have done everything in my power to make the setup run to its max. I have run it through the azzato gauntlet, and have reached the end.

Face it, if there would have been a HUGE restriction on these motors based on the 650CFM claim, Removing the restriction, no matter how bad the tune, these things would have picked up TONS of ET. That did not happen. Or you can bet your bottom dollar I would be praising the system on these big azz motors.

As Vader said, he is surprised that our setups did not gain from the change. I am equally surprised, but you can't deny what has come out in the laundry.

Hell even one run I put the stock MAF with the tube on the car with the SD system still running and it ran exactly the same........pretty strange if thats a restriction....

MrNuke

Damn Ski,

Awesome review and report on your findings. Everyone always puts down my good 'ole '870 ecm, but she has been good to me throughout all these years too. As you said in your text, it does what you tell it to, very simply.

Once again, awesome job man.

Ramanstud

Ski:

Here's a dumb question- what changes did you make to the air intake ducting when you switched to the SD? Perhaps a great test would be to run the MAF, and then leave it in place (unplugged), hook up the SD and run again to see if it could be differences in response time or resolution between the MAF and SD sensors?

Also, if you DID pull the MAF sensor and replace it with ducting for the SD conversion, what did you use to connect the aircleaner to the TB? If you used ribbed tubing for the SD conversion, perhaps the turbulence could be affecting airflow (because the MAF is smooth...)?

If you DIDN'T remove the MAF... then do so! lol. But I can't imagine you intentionally leaving it on there, so I'm assuming you've put in a larger air duct (to the Throttle body) to increase airflow / remove the MAF restriction....

Regardless, I would look at the air intake and analyze the differences to look for the loss in power (before writing off the SD)- and let us know what you've done there.