What is Speed Density?
 

So after much thinking about how to explain what true Speed Density is vs what we do here for instance, how AEM's are often setup, etc. I came up with the following idea, just explain what everything is and remove doubt.

MAF - if you dont know this one its a volume sensor. Thats it. Ours have IAT and a baro comp to make it more accurate but it simply measures volume entering the engine. If there are boost leaks its inaccurate, doesnt like VTA (letting metered air leave without pulling fuel), all the stuff we know.

Alpha-N - TPS x RPM. That is all that is with no VE compensation (i.e. boost). If I tell it that at 100% throttle and 6000 rpm it does it at all boost levels independent of air volume.

Speed density - estimates air mass by pressure vs temp. Then applies this to a 3D map. The "3D" we already have, its Load (pressure or volume) x RPM with a set value in each cell. Every point can be fine tuned so this is really Alpha N with compensation. Any VE changes needs a retune, doesnt matter the system. It only knows pressure and rpm not what the true mass of the air is (it has a trim table and most get ignored above certain levels).

THEN THERE IS WHAT I DO (and many others at this point).

I use the fuel temp sensor to mimic an IAT since its already in the car. The IAT reads gross temp not average. It can heat soak, be subject to a meth jet to close, all sorts of little issues. The actual trim table in the Evo ECU really isnt setup for IAT trim anyway. It has an algorithm that allows for minor alterations to fueling since its set for a MAF, and then trims timing vs air temp.

Fuel temp is more or less constant. The fuel heatsoaks going thru the rail hits the tank and then is sent forward again. It takes 15 minutes to get full heat into the fuel system (ask anyone with an A1000). It is a rough average of engine bay temp which is what the MAF does factory. I have done exhaustive testing and see no more than 5-6* variation from fuel temp as a source to what the MAF would read in the corner of the engine bay.

Now for the term everyone has been waiting for, Boost Comp. This is what MAFs do, most SD setups (AEM, Motec, Autronic, Vipec, etc.) do for fueling. It assumes VE is more or less constant until you hit backpressure in the turbine housing, head flow, cam size, and VE starts to drop off again.

I set the fueling at 16psi and in our maps this is 180% load or so. The values are constant out to 38psi. Hyper Boost Compensation is the proper name. Retuning is as easy as altering either the max boost portion of the MAPVE table to allow more or less fuel vs pressure, and in some cases the tip in portion of the MAPVE (121kpa column).

There is no such thing as true speed density. I havent seen any AEM ever do this or any other standalone. GM is the closest to True SD and its because tada they use a MAF as well to judge volume vs pressure.

Do I do it right? I dunno. Does it work well when its setup, I build a good map, and then work that map on each and every application? Yes. Are there advantages and disadvantages? Of course, before I had the MAF comp vs Coolant the cars DID NOT love life cold. The IXs were better but not perfect, the VIIIs didnt like me.

....to be continued....

Good read!

Thank you for posting this!

There is also Alpha-N with Boost Comp. This is more or less what we do EXCEPT IT HAS NO TEMP input. It is solely rpm x TPS x pressure. Since we aren't doing fueling by TPS vs RPM at any point other than accel enrichment it is not accurate to call the SD we normally do on Evos Alpha N or N-Alpha or Alpha-Omega or whatever. Alpha N is different and is normally something reserved for ITB cars or quads (single cylinders) that have really non specific fueling and just need fuel vs tps x rpm.

I never knew you didnt have to use an ait sensor,do you have to do anything special to the rom to use the fuel temp sensor?Im using the tephra prepatched Ix rom.

I give you an A for effort, but some of your thinking is off. The temp sensor in the MAF isn't there to measure engine bay temp. It's there to measure intake air at the maf sensor.

As you correctly stated, the Mitsu Karman MAF is a volume air sensor. The baro and temp are needed to correct to mass airflow. That's why the baro and temp sensor are directly in the MAF, taking the measurments where the volume air flow is being measured.

As you know, there are many 'loads' in our ECU. The load that is used for most of the fuel and ignition 3D maps is the baro+temp compensated load, meaning it's the mass airflow. So, our maps aren't pressure or volume vs RPM, it's actual mass airflow vs RPM. Of course, there are certain conditions that the ECU uses where it uses an uncompensated load where only volumetric airflow is used (such as using only baro comp load for the ignition maps over IAT of 77F, to disallow too much advance), but in general, the mass airflow is used so that it can calculate the mass of fuel.

It's basic PV=nRT. In an engine, volumetric airflow is:

Airflow (CFM) = PR[RPM*V.E.*Cid/3456]
PR=Pressure ratio=(boost in psi+atmos(psi))/atmos(psi)
RPM = RPM of engine
V.E. = volumetric efficiency at RPM being measured
Cid=cubic inch displacement= 122 for our 2.0L engines

To get mass airflow, you have to multiply that volumetric airflow by P/RT:

Airflow(lb/min)=(Airflow(CFM)*P/RT)*29(g/mol air)
P=atmostpheric pressure in PSI
R=ideal gas constant=10.7316 ft3·psi· °R-1·lb-mol-1
T=temperature in R (F +460)


In terms of SD for the Evo ECU, the IAT sensor needs to know the true air temp after the intercooler. That's the only way it's going to know the true mass airflow. Using the fuel temp sensor isn't telling it the correct info. Of course, you can tune around it, with the 3D maps and the VE maps, but you are simply correcting the mistaken mass airflow that is being reported.

So for instance, would running the MAF IAT>>> with a gm IAT sensor in the cold piping be about as efficient as one could get in terms of achieving accurate fueling?

Yes, that's why the IAT needs to be post IC. Either in UICP or IM. The only issue is that heatsoaking of the IAT (for example after engine shutdown and starting a warm engine later) would cause inaccurate fueling. I think DSMLink's SD implementation on the DSM ECUs uses different parameters for startup to alleviate this issue. This can potentially be patched to the EVO ECU SD as well. Aside from that, the current EVO SD implementation with GM IAT post IC should have very accurate mass airflow calculations.

But, in my opinion, using the fuel temp sensor or just some engine bay temp sensor isn't a good idea, especially for the most important parts, such as WOT, where the IATs can climb rapidly. Your fueling will be off by quite a bit. Of course, it would be off on the rich side, which is safer.

I would imagine Aaron doesn't see much variation because he has (1) good intercooling, so temps don't rise too much during a pull, (2) open filter, so intake temps are starting close to engine bay temps, (3) an efficient setup all around making a lot of power, where he isn't in the throttle for huge periods of time, where intake temps can dramatically change. Even if so, it can all be tuned around, but that is more of a band-aid kind of fix than I would like, personally.

I disagree...

A SD system or a system with VE tables, will need to be retuned for any VE changes, as the SD system cant compensate for VE changes.

A MAF based system will compensate for the change in VE, but will need to be retuned for max performance.

While I see the point in your post. I think there is something to be said about the repeatability and consistency of using the fuel temp as a replacement. I can compensate for it "being off" and have still consistent fueling since it does not act in an irratic manner despite not being a true iat temp.

I hope this makes sense despite speaking in generalities.

definately agree with you l2r99gst. using the fuel temp as IAT is an awful idea for road race cars where true heatsoak of the intercooler with throw the tune way off. up in WA it might not be an issue, but down here in TX heatsoak is a huge issue. for drag cars or cars that don't see prolonged high turbo outlet temps, its not going to be a problem like it is for a track car.

Yes, I completely see your point and I agree that if you are in an environment and have a setup that lends itself to be tuned using the fuel temp or some other arbitrary temp sensor, then it will be fine.

You just have to know that and be aware that you aren't calculating or measuring any true mass airflow and that any deviation in that temp that you aren't measuring will throw off the tune.

When you say that fuel temp mimics air temp, I thought you were talking about post IC air temp, and not just the MAF temp, which is pre IC.

So have you compared fuel temp to air temp using a real AIT sensor and NOT the MAF temp sensor?

its definately MAF temps, because post IC temps can vary drastically on what intercooler you use, what turbo, how much boost, and of course the air coming into the turbo. and also varys over time depending on airflow through the intercooler, and heatsoak.

Exactly.

I made that post because JB has been posting that fuel temp mimics air temp, and I thought he was basing that statement off comparing the fuel temps to air temps taken with an actually AIT sensor, not the MAF. Now that he states he making this comparison off MAF temps, Id like to know if he's compared fuel temps to actual air temp taken with a AIT sensor.

Again I agree, I acknowledge this, and then it is in the process of tuning the car that you are accounting for these other variables (consciously or not) that aren't reflected when using fuel temp, i.e. efficiency of your setup, ic heatsoak, environment, etc.

Edit: I think you were getting at this now that I re-read your post. I'll restate anyway. :)

I have logged UICP temps vs Intake temp at the inlet (which Eric, I realise is what its for).

That on a good intercooler when it is moving air and not heatsoaking was within 9*.

Mychailo showed 64* inlet, 3.5" intercooler core, 26.6psi of boost, 73* UICP.

I showed very similar with my 3586 and 4", and fuel temp was in the middle. I did not have a true thermocouple in the intake pipe. I can do that I suppose but it defeats the purpose of why I do it the way I do other than for the knowledge. I just used a brand new infared on the surface. On Jeff's 1G racecar we do have pre and post to see how well the 6" intercooler works at 48psi. This is an extreme case, but at a 95* inlet it was 128* at 48psi in the UICP.

Jay,

Our MAF is good but not that good. Take a well tuned car and throw an Intake manifold on that works (i.e. Magnus) it will lean out. Why? Volume in thru the turbo at a given boost level doesnt have to go up. How the engine uses what it consumes does. I learned that 2 years ago when the Magnus first got released and went on Billy@Englishracing's landlord's car (Spaceballs I know).

DSMlink ignores it after a certain calculated Hz level yes. AEM ignores it under preset ranges or however you configure it for that matter. I have tested this in extremes, I am being 100% serious when I say 16*F to 106*F. AFR was 12.0 at both times on the same car. On 110 it made 647 both times with no changes and when we put Q16 in it and turned the boost up it ran 142mph in 90*+ heat without any tuning.

Anything is a band aid really. Its how big is the band aid vs the wound? I mean sometimes I have used band aids when I need stitches but I have gotten stitches when a butterfly would have been plenty.

I am agreeing with you, I am just trying to say there isnt a perfect system because entropy doesnt allow it. The UICP is the "best" solution but still has issues because it heatsoaks on sitting. Mine assumes a very good intercooler setup and relies on the heatsoaking to work perfectly. If you ran SD on an Ebay intercooler (like a lot of the hondas we see) it becomes obvious that it doesnt work that way.

I never did publicly thank Sean@FFTEC for telling me I didnt know what I was missing out on with SD.

Thanks dude {thumbup}

Aaron

Yep, Aaron, your method is just another way to skin the cat. If your true IAT temps post IC are very consistent and deviation from fuel temp is very consistent, then it will work without issue.

It's just not for me...I'm sort of a data junkie. I need the data to be right, for reference to other cars, other data, or even other logs from years past. I just feel better having the ECU know the true mass airflow when it counts.

But, there is more than one than way to get to a common goal. Your approach is just another. Thanks for sharing...I was never bashing it of course. Just making sure people understand what it's doing.

I don't completely agree with this, though.

The Mitsu maf based system does take VE into account. The reason you were leaning out when testing Magnus intakes on a MAF system was from other reasons, such as possibly the intake pipe being used, etc, etc.

The Mitsu MAF measures volumetric airflow. If the Magnus intake increased VE, the the volume of air the engine was using per time would increase, causing more air to be pulled through the MAF and measured. A properly functioning Mitsu MAF system will always account for changes in VE because of this. Any AFR changes you see are from completely different reasons altogether (burn rates, timing, tuning, other parts, etc).

SD on the other hand, doesn't take VE into account, since we are giving it the VE to calculate a mass airflow, and needs to be retuned for any mod that changes VE, such as an IM, cams, etc.

We are on the same team {thumbup}. I am posting this since recently there have been ALOT of questions about how we do SD, what is it if its not real SD, how does it compare. You guys have not let me down in making sure the proper labels have been applied and in your case the proper formulae.

In my car and Mychailo's it seems to be very consistent and his was on a stock appearing turbo which should be hotter for a given pressure ratio anyway depending on where a BBK runs at 26.6psi :)

That was constant since it was still on a MAF, it only changed the coupler to the turbo. The only change was the UICP was chopped to meet the angle of the Magnus. I will look at the thread to see what else might have been different but I am positive that was as back to back as we could get it. 441whp before at 28psi, 474whp at 28psi after.

I was still editing my post as you were responding, but there are various (too many too name) reasons as to why the AFR changed when testing the Magnus. But, the Mitsu MAF system definitely takes VE changes into account. That was the point I was trying to address without having to write a 2 page answer.

I simply stated something like an intake pipe, since that is one thing that could throw off a MAF. But, it can get much deeper, such as the new VE needing different timing advance, causing different burn rates, etc, etc, etc. Difference in timing does affect AFR, for example. It's obviously a complex system and gets into the true engineering of an engine.

I agree, Aaron. This was just a good thread and I jumped in. You're doing a great job. Just like discussing things like this.

Aphpa-N is fundamentally different then "speed density" in that it is more of a direct look up system. Alpha-N is meant to be the most responsive to driver input and can use all kinds of compensation on top of the TPS vs. RPM and still be alpha-N. It is also largely used because of unstable pressure signals that high overlap cams and ITBs give. Thus the idea is that at a given TPS and RPM it will make a % of what ever the maximum torque is. That maximum torque level is then based on things like IAT, plenum pressure, coolant temp, and other variables that can be more slowly updated without causing a problem. Thus the ECU can focus more energy into calculating changes due to driver inputs.

Boost Comp, VE Comp, Hyper Boost Comp, blah blah blah they are all versions of "speed density" just different ways to skin a cat.

Boost comp is mostly popular simply because it is very quick to setup a fuel map that is very close for all boost conditions. Should you over boost beyond where the motor is tuned for, it is likely fuel will be close to what is needed. On a straight IPW based map by contrast, if you haven't programmed the pulsewidth at that pressure and RPM point correctly, the fuel won't be any where close.

VE comp is similar to boost comp, but typically separates out VE tuning from AFR tuning and it automatically accounts for density changes due to plenum pressure and IAT. This IMO is my favorite system as it allows you to focus on tuning the AFR separately from engine VE so if you make a change to an engine part, it is pretty simple to remap the VE curve with just matching the logged AFR with the target AFR table. If I ever get around to writing my own 3D SD patch, this is how I will set it up.

You say Potato...

subscribed! thinking about going SD myself. just trying to get as much info as possible prior to making a decision.

very good information in this thread.

x10!

This is a great thread Aaron. Thank you for sharing with the community about SD. It is more complicated then a lot of people think. You don't just throw a 4 bar on and go to town.

My brain feels a bit mushy now... :lol:

Mikey

Would you guys like me to give that a shot?

I figure I can just use the rpm and load axis that the tephra rom is using should be trivial in that regard to get a 3d ve map just need to repoint the map and function to use the get byte map function instead.

If any rom was to get this done what version would you prefer? 9417 or the 9653 variants?

Awesome thread arron!!!!!

Great info. Thanks

Selfish Request would be a V7 9653 {thumbup}

Thats not really selfish, because the 9653 is considered the universal rom anyways :)

Not to me. I never use the 9653. Unless the customer already has it as their ROM.

But u can use the others too.

Ya I know. I was just saying 9653 is universal because it works on uk/us evos where as 9417 wont work on uk.

Yeah I know but my friend didn't he tried the 9417 ten times.:lol:

I'll just do both but 9417 variant first because i'm way more familiar with its layout.

I should have this mod done within the hour been working on while you guys are debating. I plan on leaving the old tables just in case. Should be pretty cool when its done.

Wait you making a 3d VE map for the 9417 SD rom, right now?

Yeah I'm bored and this is pretty easy from what i can see.

Of course easy is subjective. Hopefully I have this decoded enough to see all the hooks. Atm there appear only to be 2 hooks into that VE table. I've already coded in the new table and compiled the new xml.

It simply is going to work or it will break. Wont brick an ecu just wont run if there are hooks I couldn't see, or will run poorly heh.

Test rom:
http://www.megaupload.com/?d=KH4LWMG6

Interesting.... :D This is sweet

Mikey

I plan on waiting for a test on that rom before moving to the 9563 as it would be pointless if it didn't work at all :)

how often to sd customers come back for a tune through out the year? could a single tune be done to last the year? or are tunes required more frequently because of weather?

also, would the intake manifold be the best place to install the IAT? if so, happen to know what drill bit size and tap required for a gm IAT:updown:

i am highly considering going to sd this year. this thread has got me thinking......

Around here it seems that cars are constantly changing either parts or owners (who then change parts) so cars get tuned and retuned fairly frequently. I have gone as long as I can without retune and other than chasing an issue in my car that ended up being E85 black goo it hasnt needed retuned up until 2 weeks ago. This is based on it being tuned in July (the 5th to be exact). It didnt really need retuned recently either, it was more of a diagnosis thing.

hmm. so it is possible to get a nice tune for daily driving and have it last?
the only reason i havent done sd yet is because i herd re-tunes are required more frequently.

this would be done on a pure daily driven street car that never sees track time so thats also another reason. im not really trying to squeeze out as much power as i can from my current setup but would like better drivability...specially with the vta tial

I honestly feel the car should be checked 2 times a year or whenever parts change regardless of whether its MAF or SD. SD really needs the tune checked with part changes, but at least in my experience it can go longer on weather. The main thing to be kept in mind is what extremes the car is driven in. Here in the NW its pretty average most of the year and that could be a reason why my tune stays consistent. We do get extreme cold snaps in winter from time to time and heat waves in the summer. I drive the car through all of these but I dont rip on it all the time in the cold or extreme heat. If you got tuned (lets say in AZ for instance) in the middle of winter and race a lot in summer it would be in your best interest to get it checked when you do the bulk of your racing.

My DD was SD and for a whole year i never really tuned it. Drove fine no major shifts in AFR at any point and that was on e85.

I'd say its capable of being a DD rom for sure

im in texas. pretty hot summers, mild winters.

i dont really plan on adding any more performance parts so i think if i get a summer tune and winter tune i would be set. ughh...time to rip off that manifold again and drill in that iat:rolleyes:

thanks for the assurance though{thumbup}

Hey Aaron,

What great info i feel this should be a sticky {thumbup}

Mike

Good information Aaron. Thank you for posting. I will see you pretty soon for some modding tune.

the manifold isnt a good place for the IAT because it gets very hot, you'll have the heat soak problems people have with warm start on SD.

use the upper intercooler pipe if possible.

also, the SD doesn't require the AIT sensor at all if your not ever tracking the car. the fuel temperature sensor can work as well, and is already wired into the ECU.


and from my experience, a well tuned and maintained MAF car will work as good as a SD car (although in your case the TIAL doesnt help a maf tune). even the SD has its issues...

At this point my daily is a LOT hapier on SD. Granted I haven't had the same exact map for more than a couple days in a row (mostly because I like to play)... but in terms of smooth consistant, stall free 14.7-10.8 fueling I can't make the MAF work like this. I tried and gave up, I'm sure someone can but not me and certainly not with my intake and BOV set-up. :)

Excuse my ignorance here but couldn't you set the ECU to use the Fuel Temp Sensor during startup and then switch over the the IAT after a determined time or something? It seems the Fuel temp sensor shouldn't be subjected to as much engine off/heatsoak,no? I just figured that its already in the car and all...



Either that or use an ambient air temp sensor and build an IC efficiency table per RPM?

I haven't messed with SD (first time will be next week though) so forgive any stupid questions.

interesting

That's a very good idea. The only thing is that some people use the fuel temp sensor input for their GM IAT so there can be easy switching back and forth with just a flash.

That is a very viable solution, though. Else, as I suggested in the past, just use some offset from the coolant temp or something for startup and maybe 30 seconds after.

That would be kind of like DSMlink, I checked and it ignores air temp under 1500hz by default.

Aaron

Great thread Aaron. Hopefully the information shared in this thread can clear up some misconceptions of SD tuning.

Anytime Aaron.

Hopefully we can actually meet sometime @ an event.:beer:

very informative thread! Thanks for sharing the info Aaron. {thumbup}
Ive been considering making the swap to SD for a min. now... Just started reading up on it a lil, and I have a couple dumb questions...
Now when u say "I use the fuel temp sensor to mimic an IAT since its already in the car", does this need to be re-wired into the correct input of the ecu, or does it just need to be configured in the SD maps, and if so, does it come pre-configured???
I have a base map ready for initial testing, just not sure on that, and whether or not I can run SD w/ the current MAF/intake (Injen) on the car (unplugged) until I get another intake?

edit: 88590715 1715 rom
TIA

Its just changing an ADC address in the ROM...0x03 to 0x0E as I recall.

well you and I seem to get it done {thumbup}

Of course...We were at the "West Coast Shootout" this year which was mostly a Honda meet it seemed but we try to get to Sac during winter to test before regular season as well.

Aaron

JB,
Is the fuel temp sensor scaling the same as the GM IAT sensor? Im wondering if the instructions in mrfred's MAT logging thread are applicable to using the fuel temp sensor, only without actually installing the sensor.

if not, can you share the scalings you use in evoscan and the big ecuflash table?

The lowest temp Im seeing is 68 deg (40 deg outside), even with a completely cold motor; using the settings in the MAT logging thread.

thx

If using the fuel temp sensor, you shouldn't change the table at all as that table is the correct table for the fuel temp sensor.

Evoscan should just be the standard temperature equation used on the ECT channel? "x-40" for degree Celsius?

edited...
found this
https://www.evolutionm.net/forums/ec...nsity-mat.html
So it really doesnt matter. But Im still not sure how to log the fuel temp sensor while not on SD. The scaling that comes with the SD ROM in the SD IAT Scaling table is correct for the fuel temp sensor.

you dont log the fuel temp sensor... its supposed to mimic actual intake air temps.. you should care more about making sure your MAP sensor ve calibration table is properly setup for your map sensor being used and then fine tune with the RPM VE.

some cars create a lean spot at around 2k which requires you to patch that area up .. i force the car in open loop and richen the area and it removes the issue entirely.

with the 3d ve maps by roadspike you can remove it as well with just the 3d rpm ve table he created.

SD is as easy to tune as a MAF is.. i was surprised actually, i expected it to be difficult.

I understand that. I was just logging the data before making the switch to the 3d SD rom. And wanted to make sure it was scaled correctly and the data I was seeing is what JB (and others who use the fuel sensor) is used to seeing. Im still not 100% sure the data Im seeing from that sensor is correct. It stays between 75-85 deg F (40-50 outside) And somtimes up to 15 deg difference compared to MAF IAT. But the car runs surprisingly smooth in the driveway so far. For some reason my STFT stopped working and need to look it that now...(different issue) But now I know that the SD IAT Scaling (found in phenem and roadspike's roms) is not to be modified if using the fuel temp sensor and the MAT Scaling in the MAT section does not get used in the SD roms. When I switch to the GM IAT sensor, that SD IAT Scaling table will need to get changed. As long as all that sounds correct, I think Im on the right path.

i see. i use the fuel temp sensor also. i never cared to log it against the maf.

does it stay consistent with the outside temp tho? consistent as in the distance between each other? if so that should be good enough.

As JB said, it appears to be an average. It doesnt change anywhere near as often as the MAF IAT. My MAF IAT had about 20 deg difference in the log Im looking at. The fuel temp "MAT" had about 3 deg difference. Fuel temp "MAT" temps rise under WOT as MAF IAT temps drop. Also once the switch to SD is made MAF IAT and MAT become the same in evoscan, right? So you cant compare.

But Im starting over from scratch today to try and aleviate my stft issue. Its quite possible I botched the MAT stuff, thinking it had to be patched in. Starting with a "stock" 3d ve rom and only putting my fuel/timing map in. Once the neighbors start russling around, Im going to try it out.

ya i would redownload and start with the regular table scalings .. sounds like to me you changed tables you didnt have to.

your stft was stuck at 0? did you confirm your o2 voltage is cycling like it should? also confirm the car is idling using fuel trim low also. if airflow is above about 43hz its usually using the fuel trim mid which is no good.

if all else fails put it in open loop at idle and force it to your afr of choice lol.

youll most likely need to lower the rpm ve at idle area to get it to lean out also.

have fun with it. i been teasing myself putting other peoples cars on it and not mine.. im waiting for weather to warm up here so i can get my car out of storage.. we just got snow 2 days ago lol!

you have a 2005? you might not even experience the jitter with your car.. some cars dont even get the jitter .. specifically 2005's.

you using the 9653 rom? that is what i would recommend to you

Oddly, Ive had to ADD fuel at low load/rpm areas so far... SFTF was +20, WB ~17 and the car wasnt liking it. I made that change, now no stft. Im also removing the WB o2 sim patch, just hoping I can still log WB via the ECU w/ mut12.

Yeah we got 1' out of that storm. Still rocking the studs on the evo, so its all good. Ready for summer, though...

So to sum up and not be so OT...You didnt change any of the MAT/IAT scalings when using the fuel temp sensor? Do they need to be changed if you use a GM IAT sensor? It seems to me that the MAT scaling table in the MAT section is a different size than the SD IAT Scaling table in the SD section. Thats what confuses me, as all the GM IAT info leads back to mrfred's threads about his MAT patch with the MAT scaling in the MAT section.

nope i didn't touch those. i never tuned a car with the GM IAT yet, but i don't believe so if you're using the SD v7 roms.

i have 2 cars here that had the GM IAT let me check the scaling and get back to you on my next post.

cross referenced 9417 on GM IAT and one on fuel temp sensor and both have identical MAT and SD MAT Scaling for IAT Scaling Tables

so just redownload, make your changes and you're good to go. let me know how the 3d MAPS work out for you with your spot you had to richen up prior. i havent used the 3d map yet, i use the 2d still since it works quite well. if the 3d map fully fixes that spot without having to touch open loop and fuel maps that will be awesome news.

you can pm me your findings if you want or post in here. whichever you decide to do.

I got a USDM EVO8 ecu MN132874_97140008 to try the Tehpra roms on my JDM EVO5, I got the car running with 96530706 rom (I hope this ROM is the right choice) and now I would like to start working on SD using the 96533706 since my car is a JDM EVO5 there is no map sensor but the IAT is on the AFM.

What would be my best straight forward option for a map sensor and IAT hook up as I will be getting rid of the MAF. Can I wire a external IAT to the AFM harness.

Anybody here selling the right IAT and MAP sensors

Regards,

Zakie

9653 is a universal rom off an evo that doesn't have a map sensor from the factory so you can just install the map sensor with no modifications to the rom and it will work.. you want an omnipower 4 bar map and just use the fuel temp as iat.. pointless tapping a sensor in after what was discovered by people of the accuracy of an existing sensor on the car.. requires no rewiring of anything.. just buy the map sensor .. plug and play.

Thanks for the reply, a omni power 4 bar would be nice.....do you sell them? I'm not sure if the EVO5 came with a fuel temp. sensor, whats should be my next option in terms of the IAT . Also would like to have some help in wiring the map senor, pin outs of the ECU etc..

evo5 didnt have fuel temp sensor pm me your e mail il send you the evo5 pinout

Thanks for the detailed break down of the calculations. I tend to be anal about numbers so this is a big help.

As far as the Thread is concerned, it's great. I think it should be renamed Various Load calculations for the Evo and definitely stickied! {thumbup}:beer:

I'm curious as to how tuning using the fuel temp to mimic an IAT for SD tuning would affect a car running a forward facing turbo setup? Since there really is no intake to speak of on these forward facing turbo setup cars, I would think the temps that the turbo are being subjected to are vastly different then what is going on under the hood of the car.

Also, does elevation affect this type of SD tuning? I remember reading somewhere that is does, but would like some confirmation.

In theory, it would work better to have a forward facing turbo when using the fuel temp sensor since the fuel temp sensor only reads outside ambient temps basically. Since the turbo will be fed more ambient temps than an underhood intake system would, I would imagine there would be more consistency.

-Jamie

Thanks for the answer. Makes sense. I wasn't aware the fuel temp sensor read outside ambient air temp.

What about elevation changes? Any issues with that?

so, what should i gather from the video? i think i'm seeing that the car is safe to drive even at higher elevation and colder temperatures; with eh only change being less PSI? Does this make it completely viable for a daily driven car that sees 4 real seasons?

I finally understand what is Speed Density :)

Just finally took the time to read through the entire thing and this was an incredible read. Great Job in explaining everything!

Thanks :)

Thank you for clarifying this! I read several threads trying to figure out how you did this.