speed density good OR bad

[EROCK970]

Hey guy I'm thinking about going SD. Just want a Lil more info on it and what I need
Thanks for the help

 

[prove_it]

What would you use to go SD?

I love it. Makes piping easier to use. Drawback is that your not "truly" measuring the air entering the engine. It's pretty much an educated guess. You must have it tuned in right to be worth it. It's not worth spending $500 bucks to convert it over to SD for no other reason than to have SD, IMO. If your going to install ECMLINK anyway then yea, not a bad idea. SD won't make more power or have better accuracy.

 

[EROCK970]

I'm not to sure on what set up I'm going to do yet but I do have ecmlink so I can get the tuning np

 

[cheekychimp]

If you are asking, it's probably not something you need (but I could be wrong in that assumption). That's not meant to sound rude by the way, it's just that SD is usually something that people add after they have done a lot of other modifications and their power levels are increasing. As prove_it has explained, it's just another way of measuring or calculating airflow. It doesn't really give you any more power but like any good tuning it can help liberate more of the power that your other components are capable of producing. Why use SD over a standard MAS? Well as power levels increase significantly, it is possible to 'overrun' the stock MAS which then has difficulty calculating the correct airflow. When you add SD you give the ECU a set of values that it can expect to see at various RPMs under various loads so that it simply knows how much airflow it is getting without having to measure it.

Upsides and downsides? Because a MAS calculates on the spot it knows when airflow changes due to changes in your setup, temperature, humidity. An SD setup will require an IAT ( and a MAP sensor - well caught Jake! ) to help calculate temps and additional values will need to be fed into the ECU to correspond to different airflow at different temps etc. Generally, the car will run smoother with a factory MAS (assuming you have no leaks between the MAS and the intake manifold) because it measures the 'actual' airflow into the engine rather than 'estimating' it. That said most Hondas run SD straight from the factory and most of those run as smooth as silk. It all comes down to how good the data or Volumetric Efficiency (VE) tables that you feed into the ECU are and how well you update them. Your values are based upon a particular setup and if you change your setup you will need a new set of VE tables. That's why Honda ECUs are great for stock cars but the tune can rapidly go to sh*t if you make serious modifications to the engine without a reflash.

SD allows you to vent to atmosphere without any issues as well if that's your thing. Some people also claim it clears up a big restriction in airflow caused by the MAS. I'm not sure on that one. People have made 600+ hp on the stock Mitsu MAS. I'm not saying it was metering correctly at that airflow but I don't think it was really creating a huge restriction either. Then again, some people have reported making more power after switching to SD even though they weren't overrunning the stock MAS, so there may be something in it.

Google "Speed Density" and do some more reading on it. Also look up MAFT Pro and ECMLink and read what they say about it in conjunction with their ECU/piggyback controllers. Decide if it offers you what you want and also just as importantly if you have the resources and knowledge to be able to tune it to take full advantage of it. If you do it right and tune it correctly your car can run just as well as stock and theoretically should run better at WOT (depending on your power level), it just takes a little more effort to get things set up right.

 

[5OF2k]

That's debatable, prove it. And it actually does measure pressure and temperature(hence the MAP sensor). As far as "truly measuring the air entering the engine" and being "an educated guess" Im lost there....how else does it meter and compensate for varying airflow?? I've always heard and seen #'s/driveability/power/results that suggest the exact opposite of that....?

I've had multiple cars with multiple setups, everything from DSM MAFs to the GM blow throughs and SD, and I prefer SD hand over fist, as does every tuner I've talked to (save for the die-hard "if you dont have XXXXX setup, it's garbage" DSMers (We all know they're out there, adn we all know how they tend to react when people think outside of the box)).

I dare say this is just one of those topics that is always going to be under debate, just like the debate regarding 2.5 or 3.0 exhausts on 16g cars..... /ubbthreads/images/graemlins/smile.gif

-Jake

 

[ktmrider]

Agree with both points. IMO the old saying goes, "If you have to ask you probably shouldn't do it".

SD requires quite a bit more knowledge and time. It can also be finicky when seasonal changes happen. Like mentioned it puts most all the measurements ( flow, density, temp ) very close to the intake manifold which minimizes "boost leak" effects and/or charge temp variations ( IC location and efficiency, piping diameter, etc ).

MAF/MAS systems are about as plug and play as they get. Many EVO folks have made 400+ whp on the stock MAS and never have to mess with tune/maps year-round short of fueling changes. Downside is the opposite of SD positive.

Noob with no tuning experience or money to pay someone to tune = MAS/MAF. "Experienced" owner wringing every last HP outta their motor with money to spend = SD.

 

[transparentdsm]

^ nailed it. haha

 

[prove_it]

Jake,

I was trying to get at that SD doesn't truly measure the air mass. It's a calculated function based on manifold pressure and air temp which references a VE table. It's pretty much spot on with tuning, but once you change piping or change boost it can get thrown off and need to be re-tuned. MAF cars actually measure the mass of the air and prove to be more accurate. Don't get me wrong, I love SD as it opens up the piping options and cleans up the engine bay, but comes at the cost of required tuning. For example if you tune an SD car at 15psi then go drive it, it will be great. Now turn up the boost to say 25psi and the tune is off. Your VE table could be so far off in those cells that fuel and timing will be way off. If you do the same to a MAF car, the sensor will read the increase in air mass and compensate for it (as long as it's not overrun). It might not be perfect, but it will be closer.

Not trying to argue, just want to be sure the OP knows what he's getting into. Also I'm mostly referring to ECMLINK. I don't have much experience with MAFT-pro. From what I hear is that it's pretty much plug n' play. For me though I don't trust my engine to plug and play computers. I still think the majority of cars work best with a translator and a GM sensor. The factory MAF is restrictive and will be overrun quickly.

Going back to Honda running SD. That was the past. Currently all Honda/Acura vehicles use a MAS now to allow better metering which in turn reduces emissions and improves mileage.

I'm still curious to why the OP wants to go SD.

 

[matt92vr4]

I have limited experience with this subject on Galants and DSM's, only two that I can remember. I have 100's of hours on the dyno with other platforms and SD ALWAYS put down more power with the same supporting mods as long as it is tuned properly. I've seen it put down as much as 75AWHP on a 3S after switching from the stock MAF to SD and new pipes. Same turbos and boost level.

SD is not for everyone though. I wouldn't say that it's hard, but it is very time consuming. If you are not interested in spending a ton of time farting around with your car and a laptop, then SD is not for you.

I have ECMLINKv3 with the SD setup sitting on my self waiting to install. Over the next year(or 2)I'm going to install one mod at a time and then switch to SD, going to the track in between each mod and after SD. In fact I'll probably run MAF and SD during the same track night to see what the difference is.

I'm very excited to find the results. I think I'll see about 10% HP gain with SD. Again, I could be totally wrong. Time will tell. I'll be honest, I thought about being lazy and just sticking with a 2g maf. My car runs so nice right now it was tempting. I was given a swift kick in the pants to stop being lazy and go SD /ubbthreads/images/graemlins/smile.gif

 

[DR1665]

Having cut my teeth on 2GNT DSMs, which run SD from the factory (and have also put down upwards of 600whp), I have an inherent distrust of MAF setups. Where some see plug-n-play and accuracy, I see an entire fuel system crippled by the weakest link - silicone couplers. I'll be going speed density on 195/2000 through an Evo VIII ECU. I've seen enough rally cars DNF because they lost an intercooler pipe or coupler on a hard landing and then couldn't even limp the car off stage before heavy sweep came through.

Oh, and just to be a smart ass, as to comments above suggesting MAP extrapolating charge volume mathematically using manifold absolute pressure and charge air temperature are calculated guesses, I'd rather base my fuel trims off data taken at the plenum, than on the resistance of a hot wire in the wind at the end of several lengths of pipe held together with glorified rubber bands and 73¢ hose clamps.

<img src="/ubbthreads/images/graemlins/devil.gif" alt="" />

EDIT: Oops. Kinda forgot to actually offer an answer to the OP's question!

There are pros and cons to each setup. MAF is a little less expensive up front, but mainly because you've probably already got one. For the price of a nice, used Evo MAF and/or one of those clever translator doo-dads, you could buy brand new MAP &amp; IAT. The big cost is how you tune. You could spend $500 on Link. You could also spend $300 on an Evo ECU conversion &amp; flash. You could even spend $200 or less on Jackal &amp; Ostrich. At the end of the day, it's a question of what best aligns with your goals.

You DO have specific, measurable goals, right?

 

[turbowop]

Two big bonuses of going SD with ECMlink are the ability to log IAT and MAP sensors. It's really nice to go back and see what your boost is really doing when you can't take your eyes off the road during a pull. And I like putting people in their place that try to tell me that aluminum piping is better for intercooler plumbing because it retains less heat. I can just go back and dig out logs that show it doesn't. /ubbthreads/images/graemlins/rofl.gif

 

[cheekychimp]

Quoting DR1665:
I'll be going speed density on 195/2000 through an Evo VIII ECU. I've seen enough rally cars DNF because they lost an intercooler pipe or coupler on a hard landing and then couldn't even limp the car off stage before heavy sweep came through.



Where do you get the VE tables for this Brian since I assume the stock ECU is setup to work with the stock MAS?

 

[prove_it]

Quoting turbowop:
And I like putting people in their place




What? I never knew that... /ubbthreads/images/graemlins/grin.gif

 

[5OF2k]

All very valid points, for sure!

I havent noticed it being that finicky though, on my own car. I DD my car, year round, and have no problems making any adjustments when I need to(IF I need to, rather. I hadnt had to change ANYTHING on my car as my setup changed until I put the T67 on). The thing starts and idles the same regardless if its -11* or 90*, and its always spot on. I dont know if thats a result of the AEM or not compared to link/whatever, but thats just my experiences....

Also, Wop it's funny you should mention that, because I just had that exact conversation with a buddy of mine as I was talking about changing my hot side configuration and using stainless instead of aluminum. He was telling me that the steel wouldnt be as good and my IATs would rise because aluminum dissipates heat quicker. I tried to explain to him that because it dissipates heat quicker, it also absorbs heat quicker but he wasnt having it until I finished the stainless charge pipes and showed him the logs with the stainless IATs actually being COOLER.

....some peoples kids.... lol

-Jake

 

[prove_it]

I've always argued in favor of steel since I thought that aluminum would absorb engine heat. Glad to know I was right.

 

[5OF2k]

Im sure it's dependant on setup too though, and piping route. My HS pipe runs similar to a DSM's(low, along the crossmember), even with my old charge piping. That also puts it close to the DP, which Im sure isnt good for heat management. I do plan to wrap the manifold, get a turbo blacknet, and wrap the DP/HS piping too though. The FMIC I have is very efficient and known to support some good power, I just have a feeling having everything so action packed in the bay is transferring a lot of heat... I am seeing a lot higher IATs with this turbo setup than I was on the 16G, but that makes sense. Went from a cast setup to a tubular setup, inherintly more heat that way, always.

I am escited to switch to E85 and see what effect that has on the IATs. From what I understand it can run up to 40* cooler at WOT. Gotta love the corn!

-Jake

 

[prove_it]

Oh yea, just remember that your IAT sensor won't show the change in temp. I love E85. Was running 20* timing with my 14b making 300whp. Now if only I had more injector to go back to E85. It's not a rice burner, it's a corn burner.

I think we went way off topic. lol

 

[5OF2k]

That's news to me too man, I can watch it change on my logs, constantly..... Again though, this is on AEM....?

 

[Racah15]

Quoting prove_it:

I was trying to get at that SD doesn't truly measure the air mass. It's a calculated function based on manifold pressure and air temp which references a VE table. It's pretty much spot on with tuning, but once you change piping or change boost it can get thrown off and need to be re-tuned. MAF cars actually measure the mass of the air and prove to be more accurate.




I'm sorry if I'm beating a dead horse here, but If we all go to the basis of speed density, the ideal gas law which is pV = nRT, where R is a constant, we know the exact physics of the air coming in using the proper values if the sensors are placed near the intake manifold. I have my AIT placed on the TBE, and my Map at my manifold (in both my 2g and my Gvr4). So lets say if we use a maf, we typically use it near the air filter correct? Who's to say that the temperature, which also affects air density, does not change through 1'-2' of rubber piping after the MAF, Inside a 200+Degree turbo (which changes the density of ait), Out another 1'-2' pipe, Into a usually inefficient intercooler (which does cool it down changing the density again), and out another 2' of piping. This is just using rubber piping, if we use aluminum, we can actually see an increase in AIT's that the maf DOES NOT compensate for.

With speed density, you are measuring p = absolute pressure of the gas in the intake manifold (not compensating for anything due to pipeing), v = exact volume of the gas at the intake manifold, n = amount of gas, T = exact temperature of the gas at the intake manifold, at the closest possible place short of your valvetrain. The R value doesn't change unless you move to Helium City or Nitrogen Island.

So to go back to my quoted post, Changing the piping shouldn't affect anything because it's getting all the above values correctly. Now lets say you do tune at 15psi, then you want to up the boost. Usually, from what I've seen, the stock VE table is similar to the OEM Maf so you don't have to pre-tune before you start up on SD (this being ECMLink though). So if you have the correct values in the tables, it should only require minor tuning.

Now let's talk about Gas mileage. I have better gas mileage in my 2g on speed density than when I didn't. This is because we are entering more correct values than the MAF does, so which lets use burn the fuel more efficiently by being able to correctly calculate the stoichiometric ratio better.

Now lets talk about the benefits,
1:
Has anyone blown a coupler? Yes, we all have. Don't you hate having to pull over and wish you brought your tools, in order to get up and running again? With speed density, you will be able to drive back home with the only worry that a honda doesn't show up and want to race you because you're likely going to lose.

2: We already discussed better gas mileage

3: Better tuning range (People use MAFClamp frequently! [when you switch over to SD because you are overrunning the maf]), more precise tuning.

4: SD for less than $100 (http://www.ecmtuning.com/product_info.php?cPath=28&products_id=50&osCsid=5k76burcn1lmgatfj1eou7shc7)

Cons:

1: Need to understand the basis of the VE table to be able to compensate and tune correctly.

2: Need to tune the whole spectrum then smooth it out for smooth transitions

3: Harder to learn



I'm sure there's more, but I hope you all enjoyed this post. Have a good day /ubbthreads/images/graemlins/smile.gif

 

[prove_it]

Have you ever tuned with SD before?